Near-Earth Object Discovery Teams
There are several Near-Earth Object (NEO) discovery teams either in operation or in the planning stages. The early efforts to discover NEOs relied upon the comparison of photographic films of the same region of the sky taken several minutes apart. The vast majority of the objects recorded upon these films were stars and galaxies and their images were located in the same relative positions on both photographic films. Because a moving NEO would be in a slightly different position on each photograph and the background stars and galaxies were not, the NEOs appeared to “rise” above the background stars when viewed with special stereo viewing microscopes.
All of the NEO discovery teams currently use so-called charged couple devices (CCD) rather than photographs. These CCD cameras are similar to those used in camcorders and they record images digitally in many electronic picture elements (pixels). The length and width of CCD detector is usually given in terms of these pixels. A fairly common astronomical CCD detector might have dimensions of 2096 x 2096 pixels. While the CCD technology allows today’s detectors to be more sensitive and accurate than the older photographic methods, the modern discovery technique itself is rather similar. Separated by several minutes, three or more CCD images are taken of the same region of the sky. These images are then compared to see if any NEOs have systematically moved to different positions on each of the separate images. For a newly discovered NEO, the separation of the object’s location from one image to another, the direction it appears to be traveling, and its brightness are helpful in identifying how close the object was to the Earth, its size and its general orbital characteristics. For example, an object that appears to be moving very rapidly from one image to the next is almost certainly very close to the Earth. Sophisticated computer-aided analyses of the CCD images has replaced the older, manual stereo microscope techniques for all the current NEO search programs.
Not surprisingly, those discovery teams who search the largest amount of sky each month will have the most success in finding new NEOs. How much sky each telescope covers per month will depend upon a number of factors including the number of clear nights available for observing, the sensitivity and efficiency of the CCD detector, and the field of view of the telescope. Wide field of view telescopes can cover more sky per given time than telescopes with narrower fields of view. It is also important for search teams to extend their searches to greater and greater distances from the Earth or, in other words, go to fainter and fainter limiting magnitudes. A 6th magnitude star is roughly the limit of a naked eye object seen under ideal conditions by someone with very good eyesight. A 7th magnitude star would be 2.5 times fainter than a 6th magnitude star and an 8th magnitude star would be 6 times fainter than a 6th magnitude object (2.5 x 2.5 = 6.25). A difference of 5 magnitudes is a brightness difference of nearly 100 (2.5 x 2.5 x 2.5 x 2.5 x 2.5 is equal to about 100).
In terms of the discovery efforts for NEOs, NASA's current goal is to discover at least 90% of all NEOs whose diameters are larger than 1 kilometer within 10 years of project start. To meet the NASA goal, the rate with which new objects are discovered will necessarily be largest in the first few years. This is because during the latter years of the 10-year interval, more and more “discoveries” will actually be of objects that have been previously found. Currently, the best estimate of the total population of NEOs larger than one kilometer is about 1000. The progress toward discovering 90% of this population can be monitored under the "NEO Discovery Statistics" section on the NASA “Near-Earth Objects” Web site (http://neo.jpl.nasa.gov/).
Here is an example from the NEO Discovery Statistics section. As of April 24, 2012, here are the known numbers for the various categories.
Near-Earth Comet (NEC), 91
Atira Group, 11
Aten Group, 702
Apollo Group, 4808
Amor Group, 3326
Potentially Hazardous Asteroids (PHA), 1302
Near-Earth Asteroids (NEA), 8847
NEO, 8938
NEOWISE Space Infrared Survey
NEOWISE is the term used to describe the near-Earth object observing capability of the Wide-field Infrared Survey Explorer (WISE) telescope. WISE uses a 40 cm aperture telescope to observe the entire sky 1.5 times in its 9-month design lifetime. The cryogens used to cool the telescope are expected to run out in November 2010. The infrared wavelength regions are centered at 3.4, 4.6, 12, and 22 microns. The WISE spacecraft is in a nearly polar orbit with the telescope always directed 90 degrees from the sun's direction. NEOWISE is an enhancement to the WISE data pipeline that allows new moving objects to be followed up by ground-based telescopes operating in the visible region. These follow-up observations ensure that a NEO's orbit will be secure and the object will not become lost. Because dark asteroids re-radiate strongly in the infrared, NEOWISE observations can often provide better estimates for NEO diameters than can optical telescopes. That is, optical telescopes observe reflected sunlight so they cannot easily tell the difference between a small bright object and large dark object.
Principal Investigators: Ned Wright (UCLA) for WISE & Amy Mainzer (JPL) for NEOWISE
Look here for more information on WISE and
NEOWISE: http://www.jpl.nasa.gov/news/news.cfm?release=2010-174 and http://wise.ssl.berkeley.edu/
Look here for a tally of NEOWISE discoveries of comets and near-Earth objects: http://neo.jpl.nasa.gov/stats/wise/
Lincoln Near-Earth Asteroid Research (LINEAR)
In cooperation with the Air Force, MIT's Lincoln Laboratory has been operating a near-Earth object discovery facility using a one-meter aperture GEODSS telescope. GEODSS stands for Ground-based Electro-Optical Deep Space Surveillance and these wide field Air Force telescopes were designed to optically observe Earth orbital spacecraft. The GEODSS instruments used by the LINEAR program are located at the Lincoln Laboratory's experimental test site in Socorro, New Mexico. Tests in early 1996 indicated that the search system, now known as LINEAR, had considerable promise. In the period between March and July 1997, a 1024 x 1024 CCD pixel detector was used in field tests and, while this CCD detector filled only about one fifth of the telescope's field of view, four NEOs were discovered. In October 1997, a large format CCD (1960 x 2560 pixels) that covered the telescope's 2 square degree field of view was employed successfully to discover a total of 9 new NEOs. Five more NEOs were added in the November 1997 through January 1998 interval when both the small and large format CCD detectors were employed. Beginning in October 1999, a second one-meter telescope was added to the search effort.
Currently, LINEAR telescopes observe each patch of sky 5 times in one evening with most of the efforts going into searching along the ecliptic plane where most NEOs would be expected. The sensitivity of their CCDs, and particularly their relatively rapid read out rates, allows LINEAR to cover large areas of sky each night
Principal Investigator: Grant Stokes
Co-Investigators: Scott Stuart and Eric Pearce
Look here for additional information on the LINEAR program: http://www.ll.mit.edu/LINEAR/
Near-Earth Asteroid Tracking (NEAT)
The NEAT discovery team at the NASA/Jet Propulsion Laboratory has a cooperative agreement with the U.S. Air Force to use a GEODSS telescope to discovery near-Earth Objects. The NEAT team designed a CCD camera and computer system for the GEODSS telescope located on Haleakala, Maui, Hawaii. The CCD camera format is 4096 x 4096 pixels and the field of view is 1.2 x 1.6 degrees. When used for NEO discovery efforts, Air Force contractor personnel operate the telescope and the data are routed directly to the Jet Propulsion Laboratory for analyses. The NEAT system began observations in December 1995 and observed for 12 nights each month centered on the new moon through December 1996. Beginning in January 1997, the number of observing nights was reduced to the six nights each month preceding the new moon because of increased Air Force operational requirements upon the facility. In February 2000, NEAT operations were transferred from the one-meter GEODSS telescope to the nearby AMOS 1.2-meter telescope. While the field of view of the AMOS 1.2-meter telescope is about that of the 1-meter GEODSS telescope, the AMOS telescope is available for more nights per month than was the GEODSS telescope.
Beginning in April 2001, a 1.2 meter aperture Schmidt telescope at Palomar mountain (southern California) was also put into service to discover and track near-Earth objects. This telescope is equipped with three cameras, each of which has its own 4096x4096 CCD array.
As part of the NEAT effort, a SkyMorph system was developed whereby searches can be made for pre-discovery images of newly discovered objects. These pre-discovery images can then immediately improve the initial orbits of newly discovered NEOs and ensure that these objects will not be lost. Searches within the SkyMorph system can be made upon the archive of approximately 40,000 CCD images made by the NEAT system or within either the original or second generation Digitized Sky Surveys (DSS and DSS2).
Raymond Bambery: Principal Investigator
Steven H. Pravdo: Co-Investigator and Project Manager
David L. Rabinowitz, Ken Lawrence and Michael Hicks: Co-Investigators
Look here for additional information on the NEAT program: http://neat.jpl.nasa.gov/
Spacewatch
Beginning in 1984, the 0.9-meter, Newtonian f/5 Steward Observatory Spacewatch telescope has been used full time for surveying comets and asteroids under the leadership of Tom Gehrels. First installed on the University of Arizona campus in 1923, this telescope was moved to Kitt Peak, Arizona in 1963. In 1983, this instrument was donated to the Spacewatch team and in 1984 it then became the first telescope to detect and discover asteroids and comets with electronic detectors (CCDs, as opposed to photograph= ic plates or film).
The initial 320 x 512 RCA CCD detector used from 1984 to 1988 was replaced with a large format 2048x2048 CCD detector used during the interval 1989-1992. This system had a field width of 38 arc minutes and limiting magnitude of 20.5. The sensitivity of the CCD (quantum efficiency) was doubled to 70% in 1992 when a thinned 2048 x 2048 CCD was installed and extended the limiting magnitude down to 21.0. The 0.9-meter telescope is used about 23 nights per month to search for near-Earth objects. By locking the right ascension axis in place and allowing the star fields to drift through its field of view ("drift-scan") while the CCD detector was constantly read out, this telescope scanned at a rate that covers about 200 square degrees of sky each month down to magnitude 21. Each region of sky is scanned three times, about thirty minutes apart, to examine which objects have moved relative to the background stars.
This system was the first to discover NEOs with CCDs, the first to discovera comet with a CCD, and the first to discover an NEO with automated image processing software. In 2000, large minor planet (20000) Varuna in the outer solar system was discovered with this system. Spacewatch has discovered many of the smaller near-Earth objects that pass close to the Earth, including a ten-meter sized asteroid (1994 XM1) that had a then record close Earth passage (105,000 km on 1994 Dec 9). Discoveries of Potentially Hazardous Asteroids (PHAs) with the 0.9-m drift scan system total 45, NEOs total 274, and follow-up observations of NEOs many thousands.
In 2001, the Spacewatch group began observing with a newly built 1.8-meter aperture telescope designed for follow-up of asteroids that get fainter after discovery.
In late 2002, a large-mosaic CCD camera (four 4608 x 2048 CCDs) was added to the 0.9 meter, and the optical system has been modified to allow a wider field-of-view (2.9 square degrees). The 0.9 meter design now operates in the "stare" mode rather than in the previous "drift-scan" mode, whereas the 1.8-meter telescope operates in the "drift-scan" mode.
From 2005 through 2008 the Spacewatch group gradually shifted their emphasis to follow-up observations that are critical for securing accurate orbits. In addition to these activities, the Spacewatch team has been involved with studies of the Centaur and Trans-Neptunian minor planet populations and the sizes of short period comet nuclei.
Robert S. McMillan: Principal Investigator
Robert Jedicke and Jeff Larsen: Collaborators
Joe Montani and Jim Scotti: Senior Research Specialists
Look here for additional information on the Spacewatch program: http://pirlwww.lpl.arizona.edu/spacewatch/
Lowell Observatory Near-Earth Object Search (LONEOS)
Begun in 1993, the LONEOS system utilizes a 0.6-meter f/1.8 Schmidt telescope in Flagstaff Arizona to discover near-Earth comets and asteroids. The telescope was acquired from Ohio Weslayan University in 1990. Using a 4K x 4K CCD detector to cover a field of view of 2.9 x 2.9 degrees, the telescope is designed to make four scans per region over the entire visible sky each month down to a limiting magnitude of about 19. In 1999-2000, the efficiency of the LONEOS program in discovering NEOs increased significantly due to upgrades to the CCD camera and data reduction software.
Edward Bowell: Principal Investigator
Bruce W. Koehn: Computer Programming
Karri Muinonen: Asteroid detection modeling
Look here for additional information on the LONEOS program: http://asteroid.lowell.edu/asteroid/loneos/loneos.html
Catalina Sky Surveys
The Catalina Sky Surveys (CSS) is currently the most efficient NEO survey program for finding new near-Earth objects. CSS utilizes three refurbished telescopes all using identical thinned, multichannel cryogenically cooled 4K x4K CCD cameras; 1) The original Catalina Sky Survey (CSS, MPC COD 703) using a 0.7-meter f/1.8 Schmidt telescope with a 2.9 x 2.9 degree field at the Steward Observatory Catalina Station (2510m elevation, 20 km northeast of Tucson, Arizona), 2) The Siding Spring Survey (SSS, MPC COD E12) using the Uppsala 0.5-m f/3.5 Schmidt telescope with a 2.0 x 2.0 degree field operated jointly with the Australian National University Research School for Astronomy and Astrophysics at Siding Spring Observatory, Australia (1150m elevation), and 3) the Mt. Lemmon Survey (MLS, MPC COD G96) using the 1.5-meter f/2.0 prime focus telescope with a 1.0 x 1.0 degree field at the Steward Observatory Mt. Lemmon station (2790-m elevation, 18 km north of Tucson). The 1.5-m Mt. Lemmon and 1.0-m Siding Spring telescopes are also used for astrometric follow up and physical observations of interesting NEOs.
Edward Beshore: Principal Investigator
Steve Larson and Rob McNaught (SSS): Co-investigators:
Andrea Boattini, Gordon Garradd, Alex Gibbs, Al Grauer, Rik Hill and Richard Kowalski: Observers.
Look here for additional information on the Catalina Sky Surveys: http://www.lpl.arizona.edu/css/ and http://msowww.anu.edu.au/~rmn/
Japanese Spaceguard Association (JSGA)
Japan's National Space Development Agency (NASDA), the National Aeronautic Laboratory, and the Space and Technology Agency have allocated the necessary funds to bring this facility on-line. This observatory is located near Bisei town, Japan. In addition to the search for NEOs, this facility will be used to track debris in Earth orbit. The 1-meter Cassegrain telescope has a field of view of 3 degrees and there are plans to use a mosaic of ten CCD detectors each one of which will have dimensions of 2096 x 4096 pixels. A 0.5-meter telescope with a field of view of 2 x 2 degrees began operations in February 2000. Once the 1-meter NEO search telescope begins operations, the 0.5-meter telescope will be used to provide follow-up astrometric observations.
Syuzo Isobe: Principal Investigator
Look here for additional information on the JSGA program: http://www.spaceguard.or.jp/ja/index.html
Asiago DLR Asteroid Survey (ADAS)
ADAS is a dedicated asteroid search and follow-up program located at Asiago-CimaEkar, Italy. It is a joint venture between the Department of Astronomy of the University of Asiago and the Astronomical Observatory of Padua in Italy and the DLR Institute of Space Sensor Technology and Planetary Exploration, Berlin-Adlershof, Germany. The current system uses a 2K x 2K CCD detector and a 0.6 m aperture Schmidt telescope. Observations began in February 2001 and this effort will concentrate their searching at small solar elongation angles in an effort to discover near-Earth objects in the inner solar system such as Atens and the putative Inner Earth Objects whose orbits are completely inside that of the Earth.
Cesare Barbieri (Padua) and Gerhard Hahn (DLR-Berlin): Principal Investigators
Look here for additional information on the ADAS program: http://planet.pd.astro.it/planets/adas/index.html
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Saturday, April 28, 2012
Friday, April 27, 2012
Happy (Spring) Astronomy Day 2012!
Astronomy Day logo. Image Credit: The Astronomical League (http://www.astroleague.org/ )
The dates for Astronomy Day this year are in the spring on April 28, 2012 and in the fall on October 20, 2012. Around the world, astronomical societies, planetariums, museums, and observatories are sponsoring public viewing sessions, presentations, workshops, and other activities to increase public awareness about astronomy and our wonderful universe.
You can find out about special local events by contacting your local astronomy club or planetarium. You can also find more about Astronomy Day by checking the website for the Astronomical League, http://www.astroleague.org/ and you can visit the Astronomy Day site here: http://www.astroleague.org/al/astroday/astroday.html
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It is time, again, for Astronomy Day--an annual event dedicated to raise public interest in astronomy by providing interaction between the general public and astronomy enthusiasts, groups and professionals. The theme of Astronomy Day is "Bringing Astronomy to the People."
The dates for Astronomy Day this year are in the spring on April 28, 2012 and in the fall on October 20, 2012. Around the world, astronomical societies, planetariums, museums, and observatories are sponsoring public viewing sessions, presentations, workshops, and other activities to increase public awareness about astronomy and our wonderful universe.
You can find out about special local events by contacting your local astronomy club or planetarium. You can also find more about Astronomy Day by checking the website for the Astronomical League, http://www.astroleague.org/ and you can visit the Astronomy Day site here: http://www.astroleague.org/al/astroday/astroday.html
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Near-Earth Objects, Part Three
Atens, Apollos and Amors
Atens, Apollos and Amors are subgroups of Near-Earth asteroids, and are categorized by their orbits. In terms of orbital elements, NEOs are asteroids and comets with perihelion distance q less than 1.3 AU. The vast majority of NEOs are asteroids, referred to as Near-Earth Asteroids (NEAs). NEAs are further divided into the following groups according to their perihelion distance (q), aphelion distance (Q) and their semi-major axes (a):
Group / Description / Definition
NEAs - Near-Earth Asteroids.
Definition: q < 1.3 AU
Atens - Earth-crossing NEAs with semi-major axes smaller than Earth's (named after asteroid 2062 Aten).
Definition: a < 1.0 AU, Q > 0.983 AU
Apollos - Earth-crossing NEAs with semi-major axes larger than Earth's (named after asteroid 1862 Apollo).
Definition: a > 1.0 AU, q < 1.017 AU
Amors - Earth-approaching NEAs with orbits exterior to Earth's but interior to Mars' (named after asteroid 1221 Amor).
Definition: a > 1.0 AU, 1.017 < q < 1.3 AU
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Atens, Apollos and Amors are subgroups of Near-Earth asteroids, and are categorized by their orbits. In terms of orbital elements, NEOs are asteroids and comets with perihelion distance q less than 1.3 AU. The vast majority of NEOs are asteroids, referred to as Near-Earth Asteroids (NEAs). NEAs are further divided into the following groups according to their perihelion distance (q), aphelion distance (Q) and their semi-major axes (a):
Group / Description / Definition
NEAs - Near-Earth Asteroids.
Definition: q < 1.3 AU
Atens - Earth-crossing NEAs with semi-major axes smaller than Earth's (named after asteroid 2062 Aten).
Definition: a < 1.0 AU, Q > 0.983 AU
Apollos - Earth-crossing NEAs with semi-major axes larger than Earth's (named after asteroid 1862 Apollo).
Definition: a > 1.0 AU, q < 1.017 AU
Amors - Earth-approaching NEAs with orbits exterior to Earth's but interior to Mars' (named after asteroid 1221 Amor).
Definition: a > 1.0 AU, 1.017 < q < 1.3 AU
NEO Groups
In terms of orbital elements, NEOs are asteroids and comets with perihelion distance q less than 1.3 AU. Near-Earth Comets (NECs) are further restricted to include only short-period comets (i.e. orbital period P less than 200 years). The vast majority of NEOs are asteroids, referred to as Near-Earth Asteroids (NEAs). NEAs are divided into groups (Aten, Apollo, Amor) according to their perihelion distance (q), aphelion distance (Q) and their semi-major axes (a).
Group / Description / Definition
NECs - Near-Earth Comets.
Definition: q < 1.3 AU, P < 200 years
NEAs - Near-Earth Asteroids.
Definition: q < 1.3 AU
Atens - Earth-crossing NEAs with semi-major axes smaller than Earth's (named after asteroid 2062 Aten).
Definition: a < 1.0 AU, Q > 0.983 AU
Apollos - Earth-crossing NEAs with semi-major axes larger than Earth's (named after asteroid 1862 Apollo).
Definition: a > 1.0 AU, q < 1.017 AU
Amors - Earth-approaching NEAs with orbits exterior to Earth's but interior to Mars' (named after asteroid 1221 Amor).
Definition: a > 1.0 AU, 1.017 < q < 1.3 AU
PHAs - Potentially Hazardous Asteroids: NEAs whose Minimum Orbit Intersection Distance (MOID) with the Earth is 0.05 AU or less and whose absolute magnitude (H) is 22.0 or brighter.
Definition: MOID <= 0.05 AU, H <= 22.0
Near-Earth Objects And Life On Earth
Although the exact process by which life formed on Earth is not well understood, the origin of life requires the presence of carbon-based molecules, liquid water and an energy source. Because some Near-Earth Objects contain carbon-based molecules and water ice, collisions of these object with Earth have significant agents of biologic as well as geologic change.
Scientists estimate that for the first billion years of Earth's existence, the formation of life was prevented by a fusillade of comet and asteroid impacts that rendered the Earth's surface too hot to allow the existence of sufficient quantities of water and carbon-based molecules. Life on Earth began at the end of this period called the late heavy bombardment, estimated to be some 3.8 billion years ago. The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier - just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did. But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth's surface, then how were these building blocks of life delivered to the Earth's surface so quickly? The answer may involve the collision of comets and asteroids with the Earth, since these objects contain abundant supplies of both water and carbon-based molecules.
Once the early rain of comets and asteroids upon the Earth subsided somewhat, subsequent impacts may well have delivered the water and carbon-based molecules to the Earth's surface - thus providing the building blocks of life itself. It seems possible that the origin of life on the Earth's surface could have been first prevented by an enormous flux of impacting comets and asteroids, and then a much less intense rain of comets may have deposited the very materials that allowed life to form some 3.5 - 3.8 billion years ago.
Comets have this peculiar duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent cometary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further. It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused a massive extinction of more than 75% of the Earth's living organisms, including the dinosaurs. At the time, the mammals were small burrowing creatures that seemed to survive the catastrophic impact without too much difficulty. Because many of their larger competitors were destroyed, these mammals flourished. Since we humans evolved from these primitive mammals, we may owe our current preeminence atop Earth's food chain to collisions of comets and asteroids with the Earth.
Near-Earth Objects As Future Resources
The comets and asteroids that are potentially the most hazardous because they can closely approach the Earth are also the objects that could be most easily exploited for their raw materials. It is not presently cost effective to mine these minerals and then bring them back to Earth. However, these raw materials could be used in developing the space structures and in generating the rocket fuel that will be required to explore and colonize our solar system in the twenty-first century. It has been estimated that the mineral wealth resident in the belt of asteroids between the orbits of Mars and Jupiter would be equivalent to about 100 billion dollars for every person on Earth today. Whereas asteroids are rich in the mineral raw materials required to build structures in space, the comets are rich resources for the water and carbon-based molecules necessary to sustain life. In addition, an abundant supply of cometary water ice could provide copious quantities of liquid hydrogen and oxygen, the two primary ingredients in rocket fuel. It seems likely that in the next century when we begin to colonize the inner solar system, the metals and minerals found on asteroids will provide the raw materials for space structures and comets will become the watering holes and gas stations for interplanetary spacecraft.
To be continued...
In terms of orbital elements, NEOs are asteroids and comets with perihelion distance q less than 1.3 AU. Near-Earth Comets (NECs) are further restricted to include only short-period comets (i.e. orbital period P less than 200 years). The vast majority of NEOs are asteroids, referred to as Near-Earth Asteroids (NEAs). NEAs are divided into groups (Aten, Apollo, Amor) according to their perihelion distance (q), aphelion distance (Q) and their semi-major axes (a).
Group / Description / Definition
NECs - Near-Earth Comets.
Definition: q < 1.3 AU, P < 200 years
NEAs - Near-Earth Asteroids.
Definition: q < 1.3 AU
Atens - Earth-crossing NEAs with semi-major axes smaller than Earth's (named after asteroid 2062 Aten).
Definition: a < 1.0 AU, Q > 0.983 AU
Apollos - Earth-crossing NEAs with semi-major axes larger than Earth's (named after asteroid 1862 Apollo).
Definition: a > 1.0 AU, q < 1.017 AU
Amors - Earth-approaching NEAs with orbits exterior to Earth's but interior to Mars' (named after asteroid 1221 Amor).
Definition: a > 1.0 AU, 1.017 < q < 1.3 AU
PHAs - Potentially Hazardous Asteroids: NEAs whose Minimum Orbit Intersection Distance (MOID) with the Earth is 0.05 AU or less and whose absolute magnitude (H) is 22.0 or brighter.
Definition: MOID <= 0.05 AU, H <= 22.0
Near-Earth Objects And Life On Earth
Although the exact process by which life formed on Earth is not well understood, the origin of life requires the presence of carbon-based molecules, liquid water and an energy source. Because some Near-Earth Objects contain carbon-based molecules and water ice, collisions of these object with Earth have significant agents of biologic as well as geologic change.
Scientists estimate that for the first billion years of Earth's existence, the formation of life was prevented by a fusillade of comet and asteroid impacts that rendered the Earth's surface too hot to allow the existence of sufficient quantities of water and carbon-based molecules. Life on Earth began at the end of this period called the late heavy bombardment, estimated to be some 3.8 billion years ago. The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier - just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did. But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth's surface, then how were these building blocks of life delivered to the Earth's surface so quickly? The answer may involve the collision of comets and asteroids with the Earth, since these objects contain abundant supplies of both water and carbon-based molecules.
Once the early rain of comets and asteroids upon the Earth subsided somewhat, subsequent impacts may well have delivered the water and carbon-based molecules to the Earth's surface - thus providing the building blocks of life itself. It seems possible that the origin of life on the Earth's surface could have been first prevented by an enormous flux of impacting comets and asteroids, and then a much less intense rain of comets may have deposited the very materials that allowed life to form some 3.5 - 3.8 billion years ago.
Comets have this peculiar duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent cometary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further. It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused a massive extinction of more than 75% of the Earth's living organisms, including the dinosaurs. At the time, the mammals were small burrowing creatures that seemed to survive the catastrophic impact without too much difficulty. Because many of their larger competitors were destroyed, these mammals flourished. Since we humans evolved from these primitive mammals, we may owe our current preeminence atop Earth's food chain to collisions of comets and asteroids with the Earth.
Near-Earth Objects As Future Resources
The comets and asteroids that are potentially the most hazardous because they can closely approach the Earth are also the objects that could be most easily exploited for their raw materials. It is not presently cost effective to mine these minerals and then bring them back to Earth. However, these raw materials could be used in developing the space structures and in generating the rocket fuel that will be required to explore and colonize our solar system in the twenty-first century. It has been estimated that the mineral wealth resident in the belt of asteroids between the orbits of Mars and Jupiter would be equivalent to about 100 billion dollars for every person on Earth today. Whereas asteroids are rich in the mineral raw materials required to build structures in space, the comets are rich resources for the water and carbon-based molecules necessary to sustain life. In addition, an abundant supply of cometary water ice could provide copious quantities of liquid hydrogen and oxygen, the two primary ingredients in rocket fuel. It seems likely that in the next century when we begin to colonize the inner solar system, the metals and minerals found on asteroids will provide the raw materials for space structures and comets will become the watering holes and gas stations for interplanetary spacecraft.
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Thursday, April 26, 2012
Near-Earth Objects, Part Two
Asteroids And Comets
Asteroids and comets are believed to be ancient remnants of the earliest years of the formation of our solar system more than four billion years ago. From the beginning of life on Earth to the recent spectacular impact of Comet Shoemaker-Levy 9 with Jupiter, these so-called "small bodies" play a key role in many of the fundamental processes that have shaped the planetary neighborhood in which we live.
Comets are bodies of ice, rock, and organic compounds that can be several miles in diameter. Comets are thought to originate from a region beyond the orbits of the outermost planets. Scientists believe that gravitational perturbations periodically jar comets out of this population, setting these "dirty snowballs" on orbital courses that bring them closer to the Sun. Some, called long-period comets, are in elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets, travel in shorter orbits nearer the Sun.
When comets venture into the more intense sunlight of the inner solar system, the ices in the comet nucleus begin to vaporize and fall away. The evolved gas forms a tenuous atmosphere around the nucleus called a coma, while the dust previously in the nucleus forms a tail that can be thousands of miles long and sometimes can be seen from Earth. While striking the early Earth billions of years ago, comets are thought to have created major changes to Earth's early oceans, atmosphere, and climate, and may have delivered the first carbon-based molecules to our planet, triggering the process of the origins of life.
Most asteroids are made of rock, but some are composed of metal, mostly nickel and iron. They range in size from small boulders to objects that are hundreds of miles in diameter. A small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Almost all asteroids are part of the Main Asteroid Belt, with orbits in the vast region of space between Mars and Jupiter.
Some asteroids pass very close to Earth's orbit around the Sun. Scientists have found evidence that asteroids have hit our planet in the past. Usually, asteroids and smaller debris called meteoroids are too small to survive the passage through Earth's atmosphere. When these burn up on their descent, they leave a beautiful trail of light known as a meteor or "shooting star." Larger asteroids occasionally crash into Earth, however, and create craters, such as Arizona's mile-wide Meteor Crater near Flagstaff. Another impact site off the coast of the Yucatan Peninsula in Mexico, which is buried by ocean sediments today, is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. Fortunately for us, these big asteroid impacts are rare. A smaller rocky meteoroid or comet less than 100 yards in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in 1908. The resulting shockwave knocked down trees for hundreds of square miles.
Asteroids, Comets, Meteoroids, Meteors and Meteorites
In space, a large rocky body in orbit about the Sun is referred to as an asteroid or minor planet whereas much smaller particles in orbit about the Sun are referred to as meteoroids. Once a meteoroid enters the Earth's atmosphere and vaporizes, it becomes a meteor (i.e., shooting star). If a small asteroid or large meteoroid survives its fiery passage through the Earth's atmosphere and lands upon the Earth's surface, it is then called a meteorite. Cometary debris is the source of most small meteoroid particles. Many comets generate meteoroid streams when their icy cometary nuclei pass near the Sun and release the dust particles that were once embedded in the cometary ices. These meteoroid particles then follow in the wake of the parent comet. Collisions between asteroids in space create smaller asteroidal fragments and these fragments are the sources of most meteorites that have struck the Earth's surface.
Because they are readily available for study, many meteorites have already been subjected to detailed chemical and physical analyses in laboratories. If particular asteroids can be identified as the sources for some of the well-studied meteorites, a detailed knowledge of the meteorite's composition and structure will provide important information on the chemical mixture and conditions from which the parent asteroid formed 4.6 billion years ago.
Studying Asteroids
The scientific interest in asteroids is due largely to their status as the remnant debris from the inner solar system formation process. Because some of these objects can collide with the Earth, asteroids are also important for having significantly modified the Earth's biosphere in the past. They will continue to do so in the future. In addition, asteroids offer a source of volatiles and an extraordinarily rich supply of minerals that can be exploited for the exploration and colonization of our solar system in the twenty-first century.
Asteroids represent the bits and pieces left over from the process that formed the inner planets, including Earth. Asteroids are also the sources of most meteorites that have struck the Earth's surface and many of these meteorites have already been subjected to detailed chemical and physical analyses. If certain asteroids can be identified as the sources for some of the well-studied meteorites, the detailed knowledge of the meteorite's composition and structure will provide important information on the chemical mixture, and conditions from which the Earth formed 4.6 billion years ago. During the early solar system, the carbon-based molecules and volatile materials that served as the building blocks of life may have been brought to the Earth via asteroid and comet impacts. Thus the study of asteroids is not only important for studying the primordial chemical mixture from which the Earth formed, these objects may hold the key as to how the building blocks of life were delivered to the early Earth.
On a daily basis, the Earth is bombarded with tons of interplanetary material. Many of the incoming particles are so small that they are destroyed in the Earth's atmosphere before they reach the ground. These particles are often seen as meteors or shooting stars. The vast majority of all interplanetary material that reaches the Earth's surface originates as the collision fragments of asteroids that have run into one another some eons ago. With an average interval of about 100 years, rocky or iron asteroids larger than about 50 meters would be expected to reach the Earth's surface and cause local disasters or produce the tidal waves that can inundate low lying coastal areas. On an average of every few hundred thousand years or so, asteroids larger than a mile could cause global disasters. In this case, the impact debris would spread throughout the Earth's atmosphere so that plant life would suffer from acid rain, partial blocking of sunlight, and from the firestorms resulting from heated impact debris raining back down upon the Earth's surface. The probability of an asteroid striking the Earth and causing serious damage is very remote but the devastating consequences of such an impact suggests we should closely study different types of asteroids to understand their compositions, structures, sizes, and future trajectories.
The asteroids that are potentially the most hazardous because they can closely approach the Earth are also the objects that could be most easily exploited for raw materials. These raw materials could be used in developing the space structures and in generating the rocket fuel that will be required to explore and colonize our solar system in the twenty-first century. By closely investigating the compositions of asteroids, intelligent choices can be made as to which ones offer the richest supplies of raw materials. It has been estimated that the mineral wealth resident in the belt of asteroids between the orbits of Mars and Jupiter would be equivalent to about 100 billion dollars for every person on Earth today.
Studying Comets
Life on Earth began at the end of a period called the late heavy bombardment, estimated to be some 3.8 billion years ago. Before this time, the influx of interplanetary debris that formed the Earth was so strong that the proto-Earth was far too hot for life to have formed. Under this heavy bombardment of asteroids and comets, the early Earth's oceans vaporized and the fragile carbon-based molecules, upon which life is based, could not have survived. The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier - just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did. But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth's surface, then how were these building blocks of life delivered to the Earth's surface so quickly? The answer may involve the collision of comets with the Earth, since comets contain abundant supplies of both water and carbon-based molecules.
As the primitive, leftover building blocks of the outer solar system formation process, comets offer clues to the chemical mixture from which the giant planets formed some 4.6 billion years ago. If we wish to know the composition of the primordial mixture from which the major planets formed, then we must determine the chemical constituents of the leftover debris from this formation process - the comets. Comets are composed of significant fractions of water ice, dust, and carbon-based compounds. Since their orbital paths often cross that of the Earth, cometary collisions with the Earth have occurred in the past and additional collisions are forthcoming. It is not a question of whether a comet will strike the Earth, it is a question of when the next one will hit. It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused a massive extinction of more than 75% of the Earth's living organisms, including the dinosaurs.
Comets have this strange duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent cometary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further. Indeed, we may owe our preeminence at the top of Earth's food chain to cometary collisions. A catastrophic cometary collision with the Earth is only likely to happen at several million year intervals on average, so we need not be overly concerned with a threat of this type. However, it is prudent to mount efforts to discover and study these objects, to characterize their sizes, compositions and structures and to keep an eye upon their future trajectories.
As with asteroids, comets are both a potential threat and a potential resource for the colonization of the solar system in the twenty first century. Whereas asteroids are rich in the mineral raw materials required to build structures in space, the comets are rich resources for the water and carbon-based molecules necessary to sustain life. In addition, an abundant supply of cometary water ice can provide copious quantities of liquid hydrogen and oxygen, the two primary ingredients in rocket fuel. One day soon, comets may serve as fueling stations for interplanetary spacecraft.
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Asteroids and comets are believed to be ancient remnants of the earliest years of the formation of our solar system more than four billion years ago. From the beginning of life on Earth to the recent spectacular impact of Comet Shoemaker-Levy 9 with Jupiter, these so-called "small bodies" play a key role in many of the fundamental processes that have shaped the planetary neighborhood in which we live.
Comets are bodies of ice, rock, and organic compounds that can be several miles in diameter. Comets are thought to originate from a region beyond the orbits of the outermost planets. Scientists believe that gravitational perturbations periodically jar comets out of this population, setting these "dirty snowballs" on orbital courses that bring them closer to the Sun. Some, called long-period comets, are in elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets, travel in shorter orbits nearer the Sun.
When comets venture into the more intense sunlight of the inner solar system, the ices in the comet nucleus begin to vaporize and fall away. The evolved gas forms a tenuous atmosphere around the nucleus called a coma, while the dust previously in the nucleus forms a tail that can be thousands of miles long and sometimes can be seen from Earth. While striking the early Earth billions of years ago, comets are thought to have created major changes to Earth's early oceans, atmosphere, and climate, and may have delivered the first carbon-based molecules to our planet, triggering the process of the origins of life.
Most asteroids are made of rock, but some are composed of metal, mostly nickel and iron. They range in size from small boulders to objects that are hundreds of miles in diameter. A small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Almost all asteroids are part of the Main Asteroid Belt, with orbits in the vast region of space between Mars and Jupiter.
Some asteroids pass very close to Earth's orbit around the Sun. Scientists have found evidence that asteroids have hit our planet in the past. Usually, asteroids and smaller debris called meteoroids are too small to survive the passage through Earth's atmosphere. When these burn up on their descent, they leave a beautiful trail of light known as a meteor or "shooting star." Larger asteroids occasionally crash into Earth, however, and create craters, such as Arizona's mile-wide Meteor Crater near Flagstaff. Another impact site off the coast of the Yucatan Peninsula in Mexico, which is buried by ocean sediments today, is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. Fortunately for us, these big asteroid impacts are rare. A smaller rocky meteoroid or comet less than 100 yards in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in 1908. The resulting shockwave knocked down trees for hundreds of square miles.
Asteroids, Comets, Meteoroids, Meteors and Meteorites
In space, a large rocky body in orbit about the Sun is referred to as an asteroid or minor planet whereas much smaller particles in orbit about the Sun are referred to as meteoroids. Once a meteoroid enters the Earth's atmosphere and vaporizes, it becomes a meteor (i.e., shooting star). If a small asteroid or large meteoroid survives its fiery passage through the Earth's atmosphere and lands upon the Earth's surface, it is then called a meteorite. Cometary debris is the source of most small meteoroid particles. Many comets generate meteoroid streams when their icy cometary nuclei pass near the Sun and release the dust particles that were once embedded in the cometary ices. These meteoroid particles then follow in the wake of the parent comet. Collisions between asteroids in space create smaller asteroidal fragments and these fragments are the sources of most meteorites that have struck the Earth's surface.
Because they are readily available for study, many meteorites have already been subjected to detailed chemical and physical analyses in laboratories. If particular asteroids can be identified as the sources for some of the well-studied meteorites, a detailed knowledge of the meteorite's composition and structure will provide important information on the chemical mixture and conditions from which the parent asteroid formed 4.6 billion years ago.
- Asteroid: A relatively small, inactive, rocky body orbiting the Sun.
- Comet: A relatively small, at times active, object whose ices can vaporize in sunlight forming an atmosphere (coma) of dust and gas and, sometimes, a tail of dust and/or gas.
- Meteoroid: A small particle from a comet or asteroid orbiting the Sun.
- Meteor: The light phenomena which results when a meteoroid enters the Earth's atmosphere and vaporizes; a shooting star.
- Meteorite: A meteoroid that survives its passage through the Earth's atmosphere and lands upon the Earth's surface.
Studying Asteroids
The scientific interest in asteroids is due largely to their status as the remnant debris from the inner solar system formation process. Because some of these objects can collide with the Earth, asteroids are also important for having significantly modified the Earth's biosphere in the past. They will continue to do so in the future. In addition, asteroids offer a source of volatiles and an extraordinarily rich supply of minerals that can be exploited for the exploration and colonization of our solar system in the twenty-first century.
Asteroids represent the bits and pieces left over from the process that formed the inner planets, including Earth. Asteroids are also the sources of most meteorites that have struck the Earth's surface and many of these meteorites have already been subjected to detailed chemical and physical analyses. If certain asteroids can be identified as the sources for some of the well-studied meteorites, the detailed knowledge of the meteorite's composition and structure will provide important information on the chemical mixture, and conditions from which the Earth formed 4.6 billion years ago. During the early solar system, the carbon-based molecules and volatile materials that served as the building blocks of life may have been brought to the Earth via asteroid and comet impacts. Thus the study of asteroids is not only important for studying the primordial chemical mixture from which the Earth formed, these objects may hold the key as to how the building blocks of life were delivered to the early Earth.
On a daily basis, the Earth is bombarded with tons of interplanetary material. Many of the incoming particles are so small that they are destroyed in the Earth's atmosphere before they reach the ground. These particles are often seen as meteors or shooting stars. The vast majority of all interplanetary material that reaches the Earth's surface originates as the collision fragments of asteroids that have run into one another some eons ago. With an average interval of about 100 years, rocky or iron asteroids larger than about 50 meters would be expected to reach the Earth's surface and cause local disasters or produce the tidal waves that can inundate low lying coastal areas. On an average of every few hundred thousand years or so, asteroids larger than a mile could cause global disasters. In this case, the impact debris would spread throughout the Earth's atmosphere so that plant life would suffer from acid rain, partial blocking of sunlight, and from the firestorms resulting from heated impact debris raining back down upon the Earth's surface. The probability of an asteroid striking the Earth and causing serious damage is very remote but the devastating consequences of such an impact suggests we should closely study different types of asteroids to understand their compositions, structures, sizes, and future trajectories.
The asteroids that are potentially the most hazardous because they can closely approach the Earth are also the objects that could be most easily exploited for raw materials. These raw materials could be used in developing the space structures and in generating the rocket fuel that will be required to explore and colonize our solar system in the twenty-first century. By closely investigating the compositions of asteroids, intelligent choices can be made as to which ones offer the richest supplies of raw materials. It has been estimated that the mineral wealth resident in the belt of asteroids between the orbits of Mars and Jupiter would be equivalent to about 100 billion dollars for every person on Earth today.
Studying Comets
Life on Earth began at the end of a period called the late heavy bombardment, estimated to be some 3.8 billion years ago. Before this time, the influx of interplanetary debris that formed the Earth was so strong that the proto-Earth was far too hot for life to have formed. Under this heavy bombardment of asteroids and comets, the early Earth's oceans vaporized and the fragile carbon-based molecules, upon which life is based, could not have survived. The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier - just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did. But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth's surface, then how were these building blocks of life delivered to the Earth's surface so quickly? The answer may involve the collision of comets with the Earth, since comets contain abundant supplies of both water and carbon-based molecules.
As the primitive, leftover building blocks of the outer solar system formation process, comets offer clues to the chemical mixture from which the giant planets formed some 4.6 billion years ago. If we wish to know the composition of the primordial mixture from which the major planets formed, then we must determine the chemical constituents of the leftover debris from this formation process - the comets. Comets are composed of significant fractions of water ice, dust, and carbon-based compounds. Since their orbital paths often cross that of the Earth, cometary collisions with the Earth have occurred in the past and additional collisions are forthcoming. It is not a question of whether a comet will strike the Earth, it is a question of when the next one will hit. It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused a massive extinction of more than 75% of the Earth's living organisms, including the dinosaurs.
Comets have this strange duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent cometary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further. Indeed, we may owe our preeminence at the top of Earth's food chain to cometary collisions. A catastrophic cometary collision with the Earth is only likely to happen at several million year intervals on average, so we need not be overly concerned with a threat of this type. However, it is prudent to mount efforts to discover and study these objects, to characterize their sizes, compositions and structures and to keep an eye upon their future trajectories.
As with asteroids, comets are both a potential threat and a potential resource for the colonization of the solar system in the twenty first century. Whereas asteroids are rich in the mineral raw materials required to build structures in space, the comets are rich resources for the water and carbon-based molecules necessary to sustain life. In addition, an abundant supply of cometary water ice can provide copious quantities of liquid hydrogen and oxygen, the two primary ingredients in rocket fuel. One day soon, comets may serve as fueling stations for interplanetary spacecraft.
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Wednesday, April 25, 2012
Pi Puppids in Progress
We are just at the end of the Pi Puppid meteor shower, a southern-hemisphere shower. This shower is not regularly visible to the naked eye, though it can be seen on radar. Meteors from this shower fall from April 21 to 26 with the peak on April 24/25. The meteors have an irregular rate, but average 40 per hour. The meteors appear to radiate from a point near the star Pi Puppis in the constellation of Puppis, the Stern (deck) (RA 07hr 28min, Dec -45°). The parent of this shower is comet 26P/Grigg-Skjellerup. The shower was discovered in 1972 and has been observed about every five years, when the parent comet reaches perihelion. The next perihelion will be July 6, 2013, so next year's shower may give the southern hemisphere a good show. To learn more about meteors, check out these helpful URLs.
Meteor Showers: Shooting for Shooting Stars (a NASA Asteroid Watch news release): http://www.jpl.nasa.gov/asteroidwatch/newsfeatures.cfm?release=2010-118
Asteroids, Comets, Meteorites (a NASA Asteroid Watch article): http://www.jpl.nasa.gov/asteroidwatch/asteroids-comets.cfm
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Meteor Showers: Shooting for Shooting Stars (a NASA Asteroid Watch news release): http://www.jpl.nasa.gov/asteroidwatch/newsfeatures.cfm?release=2010-118
Asteroids, Comets, Meteorites (a NASA Asteroid Watch article): http://www.jpl.nasa.gov/asteroidwatch/asteroids-comets.cfm
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Near-Earth Objects, Part One
With all of the recent news on meteors and Near-Earth Objects, I thought this would be an excellent time to dust off my old presentation on the topic and, of course, update some of the numbers along the way. So, here we go. The presentation will take a few installments to get through, so sit back and enjoy...
The Barringer Meteorite Crater (also known as Meteor Crater) near Winslow, Arizona was the first crater to be identified as an impact crater. Between 20,000 to 50,000 years ago, a small asteroid about 80 feet in diameter impacted the Earth and formed the crater. The crater is the best preserved crater on Earth and measures 1.2 km in diameter. For many years, scientists had denied that there were any impact craters on Earth. The origin of this crater has been a source of controversy for many years. The discovery of fragments of the Canyon Diablo meteorite help prove that the feature was in fact an impact crater.
The Near-Earth Object Program
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Near-Earth Objects
Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighborhood. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter. The scientific interest in comets and asteroids is due largely to their status as the relatively unchanged remnant debris from the solar system formation process some 4.6 billion years ago. The giant outer planets (Jupiter, Saturn, Uranus, and Neptune) formed from an agglomeration of billions of comets and the left over bits and pieces from this formation process are the comets we see today. Likewise, today's asteroids are the bits and pieces left over from the initial agglomeration of the inner planets that include Mercury, Venus, Earth, and Mars.
As the primitive, leftover building blocks of the solar system formation process, comets and asteroids offer clues to the chemical mixture from which the planets formed an estimated 4.6 billion years ago. If we wish to know the composition of the primordial mixture from which the planets formed, then we must determine the chemical constituents of the leftover debris from this formation process - the comets and asteroids.
Earth in the Crosshairs
On a daily basis, about one hundred tons of interplanetary material drifts down to the Earth's surface. Most of the smallest interplanetary particles that reach the Earth's surface are the tiny dust particles that are released by comets as their ices vaporize in the solar neighborhood. The vast majority of the larger interplanetary material that reaches the Earth's surface originates as the collision fragments of asteroids that have run into one another some eons ago.
With an average interval of about 100 years, rocky or iron asteroids larger than about 50 meters would be expected to reach the Earth's surface and cause local disasters or produce the tidal waves that can inundate low lying coastal areas. On an average of every few hundred thousand years or so, asteroids larger than a kilometer could cause global disasters. In this case, the impact debris would spread throughout the Earth's atmosphere so that plant life would suffer from acid rain, partial blocking of sunlight, and from the firestorms resulting from heated impact debris raining back down upon the Earth's surface.
Since their orbital paths often cross that of the Earth, collisions with near-Earth objects (NEOs) have occurred in the past and we should remain alert to the possibility of future close Earth approaches. It seems prudent to mount efforts to discover and study these objects, to characterize their sizes, compositions and structures and to keep an eye upon their future trajectories.
Because of the ongoing search efforts to find nearly all the large NEOs, objects will occasionally be found to be on very close Earth approaching trajectories. Great care must then be taken to verify any Earth collision predictions that are made. Given the extremely unlikely nature of such a collision, almost all of these predictions will turn out to be false alarms. However, if an object is verified to be on an Earth colliding trajectory, it seems likely that this collision possibility will be known several years prior to the actual event. Given several years warning time, existing technology could be used to deflect the threatening object away from Earth. The key point in this mitigation process is to find the threatening object years ahead of time so that an orderly international campaign can be mounted to send spacecraft to the threatening object. One of the techniques suggested for deflecting an asteroid includes nuclear fusion weapons set off above the surface to slightly change the asteroid's velocity without fracturing it. High speed neutrons from the explosion would irradiate a shell of material on the surface of the asteroid facing the explosion. The material in this surface shell would then expand and blow off, thus producing a recoil upon the asteroid itself. A very modest velocity change in the asteroid's motion (only a few millimeters per second), acting over several years, can cause the asteroid to miss the Earth entirely. However, the trick is to gently nudge the asteroid out of harm's way and not to blow it up. This latter option, though popular in the movies, only creates a bigger problem when all the pieces encounter the Earth. Another option that has been discussed includes the establishment of large solar sails on a small threatening object so that the pressure of sunlight could eventually redirect the object away from its predicted Earth collision.
No one should be overly concerned about an Earth impact of an asteroid or comet. The threat to any one person from auto accidents, disease, other natural disasters and a variety of other problems is much higher than the threat from NEOs. Over long periods of time, however, the chances of the Earth being impacted are not negligible so that some form of NEO insurance is warranted. At the moment, our best insurance rests with the NEO scientists and their efforts to first find these objects and then track their motions into the future. We need to first find them, then keep an eye on them.
Crater Example One: Chicxulub
A large body of scientific evidence now exists that support the hypothesis that a major asteroid or comet impact occurred in the Caribbean region around the time of the Earth's geological boundary between the Cretaceous and Tertiary periods. Such an impact is suspected to be responsible for, or at least a contributor to, the mass extinction of many floral and faunal species, including the large dinosaurs, that marked the end of the Cretaceous period. This extinction is often described as the Cretaceous/Tertiary Extinction, or K-T Extinction. The geohydrological feature (Cenote Ring) of Northwestern Yucatan, was discovered through NASA Ames Remote Sensing technology, and represents a prime candidate for the impact site of a global catastrophic event.
The above image is an artist's concept of the impact in Northwestern Ycatan. Artist: Don Davis
The above composite satellite image shows Chicxulub Crater, Yucatan Peninsula, Mexico. The Cenote Ring is marked. Image Credit: NASA
This is a radar image of the southwest portion of the buried Chicxulub impact crater in the Yucatan (pronounced “yoo-kah-TAHN”) Peninsula, Mexico (Chicxulub is pronounced “CHEEK-shoo-loob” and is named after a local village). The radar image was acquired on orbit 81 of space shuttle Endeavour on April 14, 1994 by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X- SAR). The image is centered at 20 degrees north latitude and 90 degrees west longitude. Scientists believe the crater was formed by an asteroid or comet which slammed into the Earth more than 65 million years ago. It is this impact crater that has been linked to a major biological catastrophe where more than 50 percent of the Earth's species, including the dinosaurs, became extinct. The 180- to 300-kilometer-diameter (110- to 180-mile) crater is buried by 300 to 1,000 meters (1,000 to 3,000 feet) of limestone. The exact size of the crater is currently being debated by scientists. This is a total power radar image with L-band in red, C-band in green, and the difference between C- and L-band in blue. The 10-kilometer-wide (6-mile) band of yellow and pink with blue patches along the top left (northwestern side) of the image is a mangrove swamp. The blue patches are islands of tropical forests created by freshwater springs that emerge through fractures in the limestone bedrock and are most abundant in the vicinity of the buried crater rim. The fracture patterns and wetland hydrology in this region are controlled by the structure of the buried crater. Scientists are using the SIR-C/X-SAR imagery to study wetland ecology and help determine the exact size of the impact crater.
The above image is a SIR-C Radar image of Chicxulub Crater, Yucatan Peninsula, Mexico. The image was taken April 14, 1994. Image Credit: NASA
Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR), the major partner in science, operations, and data processing of X-SAR. Research on the biological effects of the Chicxulub impact is supported by the NASA Exobiology Program.
Crater Example Two: Barringer
The above image is an view from the air of Barringer Meteorite Crater. Image Credit: NASA
The Barringer Meteorite Crater (also known as Meteor Crater) near Winslow, Arizona was the first crater to be identified as an impact crater. Between 20,000 to 50,000 years ago, a small asteroid about 80 feet in diameter impacted the Earth and formed the crater. The crater is the best preserved crater on Earth and measures 1.2 km in diameter. For many years, scientists had denied that there were any impact craters on Earth. The origin of this crater has been a source of controversy for many years. The discovery of fragments of the Canyon Diablo meteorite help prove that the feature was in fact an impact crater.
The Near-Earth Object Program
The purpose of NASA's Near-Earth Object Program is to coordinate NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. The NEO Program will focus on the goal of locating at least 90 percent of the estimated 1,000 asteroids and comets that approach the Earth and are larger than 1 kilometer (about 2/3-mile) in diameter, by the end of the next decade. In addition to managing the detection and cataloging of Near-Earth objects, the NEO Program office will be responsible for facilitating communications between the astronomical community and the public should any potentially hazardous objects be discovered.
NEO's Discovered So Far...
As of April 22, 2012, 8931 Near-Earth objects have been discovered. Some 839 of these NEOs are asteroids with a diameter of approximately 1 kilometer or larger. Also, 1301 of these NEOs have been classified as Potentially Hazardous Asteroids (PHAs).
Potentially Hazardous Asteroids
Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threateningly close approaches to the Earth. Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs. In other words, asteroids that can't get any closer to the Earth (i.e. MOID) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHAs.
As of this writing, there are 1307 known PHAs.
This “potential” to make close Earth approaches does not mean a PHA will impact the Earth. It only means there is a possibility for such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the close-approach statistics and thus their Earth-impact threat.
To be continued...
NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Tuesday, April 24, 2012
Asteroid-Mining Venture Announcment Today
This story just smacks of so much "coolness" that I have to share it, and quickly. It seems that the dream of asteroid mining is about to get a major shot in the arm. A brand new company, called Planetary Resources, Inc., is dedicated to expanding Earth's resource base by exploring and exracting from non-Earth resources--translation, asteroid mining. And at 1:30 PM ET today, the firm is expected to announce to the world how they are going to do that.
A number of the firm's investors are notable for their entrepreneurship and interest in space, exploration, and research. Some also have previous involvement in space research. The known investor list includes Google co-founder and CEO Larry Page, Google Executive Chairman Eric Schmidt, and explorer and film-maker James Cameron.
The idea that asteroids could be mined for resources has been around for years. Asteroids can be thought of as the "leftovers" from the planet formation stage of our solar system. These chunks failed to successfully clump together with other chunks to make a planet. Most of these remnants became the main asteroid belt between Mars and Jupiter, but some pieces are occasionally pushed out to roam the solar system.
Asteroids are made mostly of rock and metal, and range from a few meters wide to nearly 10 miles across. Planetary Resources plans to target the asteroids that pass near Earth, called near-earth objects (NEOs). The company seeks to extract from these NEOs the rare earth metals that are used in such products as batteries, electronics and medical devices.
Water can be broken down in space to liquid oxygen and liquid hydrogen for rocket fuel. But water is very expensive to launch into space, so the plan is to take it from an asteroid to a point in space where it can be converted into fuel. From there, it can easily and cheaply be shipped to Earth orbit to refuel commercial satellites or spaceships from NASA, ESA, and other countries.
There is no information yet on how much the project would cost, but company representatives have stated that Planetary Resources expected to build and launch quickly, and to operate much more cheaply than NASA.
The video announcement is being streamed over the Internet today at 1:30 PM ET. The announcement URL is: http://www.spacevidcast.com/live/
The home page of Planetary Resources, Inc. can be found here: http://www.planetaryresources.com/
To learn more about these potential targets of mining opportunity, the NEOs themselves, check out NASA's Near-Earth Object (NEO) Program. The program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. http://neo.jpl.nasa.gov/
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A number of the firm's investors are notable for their entrepreneurship and interest in space, exploration, and research. Some also have previous involvement in space research. The known investor list includes Google co-founder and CEO Larry Page, Google Executive Chairman Eric Schmidt, and explorer and film-maker James Cameron.
The idea that asteroids could be mined for resources has been around for years. Asteroids can be thought of as the "leftovers" from the planet formation stage of our solar system. These chunks failed to successfully clump together with other chunks to make a planet. Most of these remnants became the main asteroid belt between Mars and Jupiter, but some pieces are occasionally pushed out to roam the solar system.
Asteroids are made mostly of rock and metal, and range from a few meters wide to nearly 10 miles across. Planetary Resources plans to target the asteroids that pass near Earth, called near-earth objects (NEOs). The company seeks to extract from these NEOs the rare earth metals that are used in such products as batteries, electronics and medical devices.
Water can be broken down in space to liquid oxygen and liquid hydrogen for rocket fuel. But water is very expensive to launch into space, so the plan is to take it from an asteroid to a point in space where it can be converted into fuel. From there, it can easily and cheaply be shipped to Earth orbit to refuel commercial satellites or spaceships from NASA, ESA, and other countries.
There is no information yet on how much the project would cost, but company representatives have stated that Planetary Resources expected to build and launch quickly, and to operate much more cheaply than NASA.
The video announcement is being streamed over the Internet today at 1:30 PM ET. The announcement URL is: http://www.spacevidcast.com/live/
The home page of Planetary Resources, Inc. can be found here: http://www.planetaryresources.com/
To learn more about these potential targets of mining opportunity, the NEOs themselves, check out NASA's Near-Earth Object (NEO) Program. The program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. http://neo.jpl.nasa.gov/
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Cassini May Have Found the Next Bonneville
A recent study finds that the lake known as Ontario Lacus on Saturn's moon Titan (left) bears striking similarity to Earth salt pans such as the Etosha Pan (right). Image credit: NASA/JPL-Caltech and NASA/USGS
A new study analyzing data from NASA's Cassini spacecraft suggests that a Titan lake, known as Ontario Lacus, behaves in a manner very similar to what we call on Earth a salt pan.
Ontario Lacus is a hydrocarbon lake on Saturn's moon Titan. The lake is located near Titans south pole and it is composed of methane, ethane and propane. Ontario Lacus has a surface area of about 15,000 square kilometers (5,800 sq mi). Though it is about 20% smaller than its terrestrial namesake, Lake Ontario in North America, Ontario Lacus is the largest lake in Titan's south polar region.
A group of scientists led by Cassini associate Thomas Cornet of the Université de Nantes, France, found evidence for long-standing channels etched into the lake bed within the southern boundary of the depression. This find suggests that Ontario Lacus, previously thought to be a standing lake of liquid hydrocarbons, could actually be a depression that drains and refills from below, exposing liquid areas ringed by materials like saturated sand or mudflats. Cornet wrote about these findings in a paper, which he co-authored with Cassini team member Bonnie Buratti, and which was recently published in the planetary science journal Icarus.
The observed characteristics of Ontario Lacus make it very similar to the Etosha salt pan on Earth, a lake bed that fills with a shallow layer of water from groundwater levels that rise during the rainy season. This layer then evaporates and leaves sediments like tide marks showing the previous extent of the water.
While the liquid on Titan is not water, the cycle appears to work in a very similar fashion to the water cycle on Earth. Beyond Earth, Titan is the only other world known to bear stable liquids on its surface. There, the full hydrocarbon cycle is based on hydrogen, carbon and nitrogen, and takes place between the atmosphere, the surface and the subsurface. Titan's lakes are an integral part of this process.
This latest paper is part of an ongoing study of Ontario Lacus. Cassini has been observing the lake with multiple instruments and employing multiple methods of analysis to see if Titan, like Earth, changes with the seasons. During the time Cassini has been exploring the Saturn system, Titan's southern hemisphere has transitioned from summer to fall. The results of studies such as these emphasize the importance of comparative planetology in modern planetary sciences. Finding familiar geological features on other worlds allow the scientists to test their theories that explain their formation.
Now, if you will forgive me, the comparison of Ontario Lacus to the Etosha Plan is all very well and good. But this latest news has caused me to think of another Earth salt pan that is quite famous to lovers of speed—the Bonneville Salt Flats in Utah, where many land speed records have been set. Just dream with me for a moment. With its similar characteristics and much grander size, Ontario Lacus could very well be the next Mecca for land speed records in the solar system! Of course, I admit there would have to be some thought and work in order to make this happen. Let’s consider the basic requirements.
First, the surface pressure of Titan is 146.7 kPa, or about 1.45 times that of sea-level on Earth. So the Titan vehicle would need to be built with at least the structural integrity of an Earth submersible capable of withstanding a water depth of about 5 meters. Second, the surface gravity of Titan is just a little less than the Moon (Earth is 1.0 g, the Moon is about 0.165 g, and Titan is about 0.14 g). So the Titan vehicle would need to take some aerodynamic precautions (or should I say hydrodynamic precautions?) in order to make sure it didn't launch itself into the Titan atmosphere. But I think the reinforced vehicle construction for the whole surface-pressure issue would go a long way in helping to keep the wheels on the deck. Finally, and most importantly, there is the whole matter of perfecting the human spaceflight experience so that you could successfully survive the trip to Titan and back. I presume you would want to come back in order to celebrate your fame, sign your book deal and do all of those celebrity endorsements.
So, all of those issues notwithstanding, if someone did want to set some Titan surface speed records, Ontario Lacus would definitely be the place to do it!... Alright, stop laughing. I mean really. Come on now. It's a thought experiment! Anyway, it keeps me off the streets, and that's a very good thing.
And now, the Cassini-Huygens mission particulars...
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. NASA's Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The RADAR instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries. JPL is a division of the California Institute of Technology (Caltech) in Pasadena.
To learn more about Ontario Lacus, Titan and Cassini, visit these links.
The home page of the planetary science journal Icarus: http://icarus.cornell.edu/
For more information about the Cassini-Huygens Mission and the mission extensions, visit http://saturn.jpl.nasa.gov/
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Bolide Over California April 22nd
Meteor News... Meteor News... Meteor News...
This passed Sunday, April 22nd, there were reports of a fireball that roared over two western states and finally exploded over California's Sierra Nevada mountain range. The sound of the explosion was heard from central California to as far east as Reno, Nevada and beyond. The available data on the event has now been analyzed by NASA's Meteoroid Environment Office, and the following can now be confirmed.
First, the object was indeed a natural meteor, and not a falling piece of space junk or a UFO. A meteor of this type--an exploding fireball--is often described by astronomical observers as a bolide. Second, the analysts estimate that the space rock (meteoroid) which entered Earth's atmosphere was approximately the size of a mini-van. Third, analysts estimate the meteor exploded in the atmosphere with an energy equal to 3.8 kilotons of TNT. And, based on a triangulation of the very low frequency sound of the mid-air explosion, they determined it occurred over latitude 37.6 degrees North, longitude 120.5 degrees West, above the Sierra Nevada mountains. And the resulting meteorite fragments are possibly strewn across that mountain range.
The event took place near the peak of the annual Lyrid meteor shower. Also, analysts do not know the exact trajectory of the bolide, so they cannot conclusively state that it was not a Lyrid meteor. But even so, they think it more likely the body was a background or sporadic meteor.
Below is information on two websites that have lots of useful information on the study of meteoroids and other near-earth objects (NEOs). Please check them out.
• The NASA Meteoroid Environment Office (MEO) is the NASA organization responsible for meteoroid environments pertaining to Spacecraft engineering and operations. The MEO leads NASA technical work on the meteoroid environment and coordinates the existing meteoroid expertise at NASA centers. To learn more, visit the home page of NASA's Meteoroid Environment Office: http://www.nasa.gov/offices/meo/home/index.html
• NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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This passed Sunday, April 22nd, there were reports of a fireball that roared over two western states and finally exploded over California's Sierra Nevada mountain range. The sound of the explosion was heard from central California to as far east as Reno, Nevada and beyond. The available data on the event has now been analyzed by NASA's Meteoroid Environment Office, and the following can now be confirmed.
First, the object was indeed a natural meteor, and not a falling piece of space junk or a UFO. A meteor of this type--an exploding fireball--is often described by astronomical observers as a bolide. Second, the analysts estimate that the space rock (meteoroid) which entered Earth's atmosphere was approximately the size of a mini-van. Third, analysts estimate the meteor exploded in the atmosphere with an energy equal to 3.8 kilotons of TNT. And, based on a triangulation of the very low frequency sound of the mid-air explosion, they determined it occurred over latitude 37.6 degrees North, longitude 120.5 degrees West, above the Sierra Nevada mountains. And the resulting meteorite fragments are possibly strewn across that mountain range.
The event took place near the peak of the annual Lyrid meteor shower. Also, analysts do not know the exact trajectory of the bolide, so they cannot conclusively state that it was not a Lyrid meteor. But even so, they think it more likely the body was a background or sporadic meteor.
Below is information on two websites that have lots of useful information on the study of meteoroids and other near-earth objects (NEOs). Please check them out.
• The NASA Meteoroid Environment Office (MEO) is the NASA organization responsible for meteoroid environments pertaining to Spacecraft engineering and operations. The MEO leads NASA technical work on the meteoroid environment and coordinates the existing meteoroid expertise at NASA centers. To learn more, visit the home page of NASA's Meteoroid Environment Office: http://www.nasa.gov/offices/meo/home/index.html
• NASA's Near-Earth Object (NEO) Program coordinates NASA-sponsored efforts to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. To learn more, visit the home page of NASA's Near-Earth Object Program: http://neo.jpl.nasa.gov/
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Monday, April 23, 2012
More Vesta for Dawn
The above image is an artist's concept of NASA's Dawn spacecraft in orbit of asteroid Vesta. The depiction of Vesta is based on images obtained by Dawn's framing cameras. Image credit: NASA/JPL-Caltech
It’s time for another NASA Dawn Mission update! The Dawn mission has received official confirmation that the current exploration of the asteroid Vesta has been extended by 40 days. Dawn achieved a stable orbit around Vesta in July 2011. The spacecraft was originally scheduled to depart in mid-July, but this extension means that Dawn will continue studying Vesta until August 26 (my birthday). And even with this extension at Vesta, the Dawn team still expects to reach Ceres at the originally scheduled target date in February 2015.
No new funding will be required for the extension because the team will be able to draw on financial reserves that have been carefully managed by the Dawn project. And the spacecraft’s efficient ion propulsion is to be credited for still getting to Ceres on time.
The mission extension allows for extra observations at Dawn’s current low-altitude mapping orbit (average altitude 130 miles or 210 kilometers). The additional time enables the gamma ray and neutron detector to build the best possible maps of the elemental composition of Vesta’s surface and improve data for the gravity experiment, the two primary scientific investigations at the low-altitude orbit. The spacecraft's camera and spectrometer are also obtaining additional high-resolution images.
Additional time will also be spent in the planned second high-altitude mapping orbit later this summer. When Dawn arrived at Vesta, much of the northern hemisphere was in shadow. But with the passage of time, more of that area will bask in sunshine. The Dawn mission team members have reported that they are very happy to take more advantage of this one-of-a-kind opportunity.
And now, the mission particulars…
Dawn's mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. For more information about the Dawn mission, visit: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov
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Sunday, April 22, 2012
NASA Mission Continuations as of 2012
Let's catch up on some great news from earlier this month regarding mission funding. As a result of the 2012 NASA Senior Review of Astrophysics Missions, several ongoing missions are being continued, and at their current funding levels. The missions are as follows.
The Hubble Space Telescope (HST) continues at its current funding levels. HST is a space telescope that was carried into orbit by the Space Shuttle Discovery in April 1990. HST is a 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble. HST was built by NASA, with contributions from the European Space Agency (ESA), and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope. The HST mission websites are: http://hubble.nasa.gov/ and http://asd.gsfc.nasa.gov/archive/hubble/ and http://hubblesite.org/
The Guest Observer budget of the Chandra X-ray Observatory is increased to account for decreases in Fiscal year 2011. The Chandra X-ray Observatory is a satellite launched July 1999 by Space Shuttle Columbia. Chandra is named in honor of Indian physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit. Prior to launch, Chandra was known as AXAF, the Advanced X-ray Astrophysics Facility. Chandra was assembled and tested by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach, California. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, due primarily to the high angular resolution of the Chandra mirrors. The mission website is: http://chandra.harvard.edu/
The Swift Gamma-Ray Burst Mission operations are extended through Fiscal year 2016 with funding for data analysis. Swift is a robotic spacecraft which was launched into orbit November 2004 on a Delta II rocket. Swift is managed by the NASA Goddard Space Flight Center, and was developed by an international consortium from the United States, United Kingdom, and Italy. It is part of NASA's Medium Explorer Program (MIDEX). The mission websites are: http://swift.gsfc.nasa.gov and http://www.nasa.gov/swift
The Kepler Mission operations are extended through Fiscal year 2016 with funding for data analysis. The purpose of the Kepler Mission is to discover Earth-like planets orbiting other stars. The spacecraft, named in honor of the 17th-century German astronomer Johannes Kepler, was launched March 2009 aboard at Delta II rocket. The mission had a planned lifetime of at least 3.5 years. Kepler is a project under NASA's Discovery Program of relatively low-cost, focused science missions. Construction and initial operation were managed by NASA's Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is responsible for the ground system development, mission operations (from December 2009), and science data analysis. The mission website is: http://kepler.nasa.gov/
The Planck Mission will support one year extended operations of the Low Frequency Instrument (LFI). Launched from the Guiana Space Centre on May 2009 aboard an Ariane 5 ACE rocket, Planck is a space observatory of the European Space Agency (ESA) and designed to observe the anisotropies of the cosmic microwave background (CMB) over the entire sky, at a high sensitivity and angular resolution. Planck was built in the Cannes Mandelieu Space Center by Thales Alenia Space and created as the third Medium-Sized Mission (M3) of the European Space Agency's Horizon 2000 Scientific Programme. The project, initially called COBRAS/SAMBA, is named in honor of the German physicist Max Planck (1858–1947), who won the Nobel Prize for Physics in 1918. Planck orbits at the Earth/Sun's L2 Lagrangian point. The mission websites are: http://www.esa.int/planck and http://planck.caltech.edu/
The Spitzer Space Telescope (SST) operations are extended through Fiscal year 2014 with closeout planned for Fiscal year 2015. Launched August 2003 aboard a Delta II rocket, Spitzer was formerly the Space Infrared Telescope Facility (SIRTF). It is an infrared space observatory, the fourth and final of the NASA Great Observatories program. The observatory was renamed in honor of Lyman Spitzer, one of the 20th century's great scientists. The mission website is: http://www.spitzer.caltech.edu/
U.S. science support of the Suzaku mission is extended to March 2015, to provide a one-year overlap with the Astro-H mission. Launched July 2005 from Uchinoura Space Center aboard a M-V-6 rocket, Suzaku (formerly ASTRO-EII) is a Japanese X-ray astronomy satellite. The project was renamed Suzaku after the mythical Vermilion bird of the South. The English version of the mission website is: http://www.isas.jaxa.jp/e/enterp/missions/suzaku/index.shtml
Funding for U.S. support of the XMM-Newton mission is also extended through March 2015. Launched by the European Space Agency (ESA) December 1999 aboard an Arian 5 rocket, The X-ray Multi-Mirror Mission - Newton (XMM-Newton) is named in honor of Sir Isaac Newton. Originally known as the High Throughput X-ray Spectroscopy Mission it is in a very eccentric 48 hour elliptical orbit. Observations are managed and archived at the European Space Astronomy Centre (formerly known as VILSPA) at Villafranca, Spain. The data are processed at the XMM-Newton Survey Science Centre at the University of Leicester, England. The European satellite XMM-Newton (X-ray Multi Mirror), built under contract to ESA by a consortium of 35 European companies with Astrium as prime contractor, by far excels its predecessor, the Astrium-built ROSAT satellite. The mission websites are: http://xmm.esac.esa.int/ and http://xmm.sonoma.edu/
The Fermi Gamma-Ray Space Telescope mission operations are extended through Fiscal year 2016, but with a 10 percent per year reduction starting in Fiscal year 2014. Formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), Fermi is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. Fermi was launched June 2008 aboard a Delta II rocket. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden. The mission website is: http://fermi.gsfc.nasa.gov/
For the business illiterate (and I mean no offence), I offer this explanation on the referenced accounting concept of the fiscal year. The schedule of NASA’s annual funding is based on the U.S. government’s fiscal year, which ends on the 30th of September of the noted fiscal year (and begins on October 1 of the prior calendar year). For example, fiscal year 2012 ends on September 30, 2012, so any U.S. funding which goes through fiscal year 2012 would end on September 30. I hope you get the idea and can extrapolate from there regarding the other fiscal years.
In addition, I must note that while some of these mentioned continuations go through fiscal year 2016, all of the decisions for fiscal year 2015 to 2016 are for planning purposes and will be officially revisited in the 2014 NASA Senior Review.
Finally, I should note that three of the referenced missions are affiliated with the Jet Propulsion Laboratory in Pasadena, California. They are the Kepler Mission, the Spitzer Space Telescope and the U.S. portion of the European Space Agency's Planck mission.
To read in full detail of the 2012 NASA Senior Review report, follow this link: http://science.nasa.gov/astrophysics/2012-senior-review/
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The Hubble Space Telescope (HST) continues at its current funding levels. HST is a space telescope that was carried into orbit by the Space Shuttle Discovery in April 1990. HST is a 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble. HST was built by NASA, with contributions from the European Space Agency (ESA), and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope. The HST mission websites are: http://hubble.nasa.gov/ and http://asd.gsfc.nasa.gov/archive/hubble/ and http://hubblesite.org/
The Guest Observer budget of the Chandra X-ray Observatory is increased to account for decreases in Fiscal year 2011. The Chandra X-ray Observatory is a satellite launched July 1999 by Space Shuttle Columbia. Chandra is named in honor of Indian physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit. Prior to launch, Chandra was known as AXAF, the Advanced X-ray Astrophysics Facility. Chandra was assembled and tested by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach, California. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, due primarily to the high angular resolution of the Chandra mirrors. The mission website is: http://chandra.harvard.edu/
The Swift Gamma-Ray Burst Mission operations are extended through Fiscal year 2016 with funding for data analysis. Swift is a robotic spacecraft which was launched into orbit November 2004 on a Delta II rocket. Swift is managed by the NASA Goddard Space Flight Center, and was developed by an international consortium from the United States, United Kingdom, and Italy. It is part of NASA's Medium Explorer Program (MIDEX). The mission websites are: http://swift.gsfc.nasa.gov and http://www.nasa.gov/swift
The Kepler Mission operations are extended through Fiscal year 2016 with funding for data analysis. The purpose of the Kepler Mission is to discover Earth-like planets orbiting other stars. The spacecraft, named in honor of the 17th-century German astronomer Johannes Kepler, was launched March 2009 aboard at Delta II rocket. The mission had a planned lifetime of at least 3.5 years. Kepler is a project under NASA's Discovery Program of relatively low-cost, focused science missions. Construction and initial operation were managed by NASA's Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is responsible for the ground system development, mission operations (from December 2009), and science data analysis. The mission website is: http://kepler.nasa.gov/
The Planck Mission will support one year extended operations of the Low Frequency Instrument (LFI). Launched from the Guiana Space Centre on May 2009 aboard an Ariane 5 ACE rocket, Planck is a space observatory of the European Space Agency (ESA) and designed to observe the anisotropies of the cosmic microwave background (CMB) over the entire sky, at a high sensitivity and angular resolution. Planck was built in the Cannes Mandelieu Space Center by Thales Alenia Space and created as the third Medium-Sized Mission (M3) of the European Space Agency's Horizon 2000 Scientific Programme. The project, initially called COBRAS/SAMBA, is named in honor of the German physicist Max Planck (1858–1947), who won the Nobel Prize for Physics in 1918. Planck orbits at the Earth/Sun's L2 Lagrangian point. The mission websites are: http://www.esa.int/planck and http://planck.caltech.edu/
The Spitzer Space Telescope (SST) operations are extended through Fiscal year 2014 with closeout planned for Fiscal year 2015. Launched August 2003 aboard a Delta II rocket, Spitzer was formerly the Space Infrared Telescope Facility (SIRTF). It is an infrared space observatory, the fourth and final of the NASA Great Observatories program. The observatory was renamed in honor of Lyman Spitzer, one of the 20th century's great scientists. The mission website is: http://www.spitzer.caltech.edu/
U.S. science support of the Suzaku mission is extended to March 2015, to provide a one-year overlap with the Astro-H mission. Launched July 2005 from Uchinoura Space Center aboard a M-V-6 rocket, Suzaku (formerly ASTRO-EII) is a Japanese X-ray astronomy satellite. The project was renamed Suzaku after the mythical Vermilion bird of the South. The English version of the mission website is: http://www.isas.jaxa.jp/e/enterp/missions/suzaku/index.shtml
Funding for U.S. support of the XMM-Newton mission is also extended through March 2015. Launched by the European Space Agency (ESA) December 1999 aboard an Arian 5 rocket, The X-ray Multi-Mirror Mission - Newton (XMM-Newton) is named in honor of Sir Isaac Newton. Originally known as the High Throughput X-ray Spectroscopy Mission it is in a very eccentric 48 hour elliptical orbit. Observations are managed and archived at the European Space Astronomy Centre (formerly known as VILSPA) at Villafranca, Spain. The data are processed at the XMM-Newton Survey Science Centre at the University of Leicester, England. The European satellite XMM-Newton (X-ray Multi Mirror), built under contract to ESA by a consortium of 35 European companies with Astrium as prime contractor, by far excels its predecessor, the Astrium-built ROSAT satellite. The mission websites are: http://xmm.esac.esa.int/ and http://xmm.sonoma.edu/
The Fermi Gamma-Ray Space Telescope mission operations are extended through Fiscal year 2016, but with a 10 percent per year reduction starting in Fiscal year 2014. Formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), Fermi is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. Fermi was launched June 2008 aboard a Delta II rocket. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden. The mission website is: http://fermi.gsfc.nasa.gov/
For the business illiterate (and I mean no offence), I offer this explanation on the referenced accounting concept of the fiscal year. The schedule of NASA’s annual funding is based on the U.S. government’s fiscal year, which ends on the 30th of September of the noted fiscal year (and begins on October 1 of the prior calendar year). For example, fiscal year 2012 ends on September 30, 2012, so any U.S. funding which goes through fiscal year 2012 would end on September 30. I hope you get the idea and can extrapolate from there regarding the other fiscal years.
In addition, I must note that while some of these mentioned continuations go through fiscal year 2016, all of the decisions for fiscal year 2015 to 2016 are for planning purposes and will be officially revisited in the 2014 NASA Senior Review.
Finally, I should note that three of the referenced missions are affiliated with the Jet Propulsion Laboratory in Pasadena, California. They are the Kepler Mission, the Spitzer Space Telescope and the U.S. portion of the European Space Agency's Planck mission.
To read in full detail of the 2012 NASA Senior Review report, follow this link: http://science.nasa.gov/astrophysics/2012-senior-review/
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Saturday, April 21, 2012
Our Changing Earth
The above image shows Carroll Glacier, Alaska. The left image is from August 1906 and the right image is from September 7, 2003. The images demonstrate the change in the ice between them. Image Credit: NASA's Global Climate Change website, http://climate.nasa.gov
Happy Earth Day, everyone! Okay. Technically I'm early. Earth Day is this Sunday, April 22nd. Begun in 1970 and now celebrated in more than 175 countries, Earth Day is is an annual international event to increase awareness and appreciation of the Earth's natural environment.
Earth Day 2012 falls on this Sunday, April 22nd. In celebration of the event, NASA's Webby Award-winning Global Climate Change website has unveiled a new version of its popular image gallery, "State of Flux." The gallery presents stunning images, mostly from space, of our ever-changing planet, chronicling changes taking place over time periods ranging from days to centuries.
The image gallery, which is continuously updated, presents pairs of before-and-after images that highlight the impacts of change, including the destruction caused by extreme events such as wildfires and floods, the retreat of glaciers caused by climate change, and the expanding footprint of urban areas due to population growth.
The redesigned image gallery currently features more than 160 comparison views and is now organized and sortable by categories, including ice, human impact, water, land cover and extreme events.
Another new feature of the website is a map view, which places each image into its geographical context. Guests can zoom in to specific locations on the map, or select by region, and see where particular changes are taking place around the globe. They can also share links to each image set and download high-resolution versions of the images.
NASA's Global Climate Change website is devoted to improving the public's understanding of Earth's changing climate, providing easy-to-understand information about the causes and effects of climate change and how NASA studies it. For more on NASA's Earth Science activities, visit: http://www.nasa.gov/topics/earth/index.html .
For more on NASA's Earth Day activities, visit: http://www.nasa.gov/earthday
NASA's Global Climate Change website: http://climate.nasa.gov
The "State of Flux" image gallery: http://climate.nasa.gov/sof
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Where’s the Dark Matter?
The above image shows the arms of the nearby galaxy Messier 81. In recent decades astronomers have thought that both the universe and galaxies are held together by the gravitational attraction of a huge amount of unseen material, now commonly referred to as dark matter. Image Credit: NASA/JPL/Caltech/Harvard-Smithsonian Center for Astrophysics
For the last couple of decades, conventional astronomy has held that there’s a mysterious, invisible substance called dark matter, and though we don’t know its precise nature, it permeates much of the universe. But now this convention may have a problem.
Dark matter was originally proposed to explain why the outer parts of galaxies, including our own Milky Way, spin more quickly than they should based on the visible objects and their gravitational interactions. Since then dark matter has become an essential part of theories of how galaxies formed and evolved. It has been widely assumed that dark matter constitutes about four-fifths of the mass in the universe.
But a new study has concluded that the mysterious dark matter is not there. At least, not in or near our solar system. And that is a problem, because it should be everywhere in our galaxy. Oh, and it is greatly needed to resolve problems in many astronomical theories.
Researchers say this new study of star motion in the Milky Way, which is the most accurate study to date, found no evidence for dark matter in or near our solar system. In their study the scientists used multiple telescopes, including the European Southern Observatory’s (ESO’s) La Silla Observatory in Chile. The team mapped the motions of more than 400 stars up to 13,000 light-years from the Sun (a light-year is the distance light travels in a year). From that data they calculated the total mass, or weight, of material in the vicinity of the Sun, in a space four times larger than ever considered before.
The team measured the motions of many stars, particularly those away from the flat disc of stars that forms the bulk of the visible Milky Way. They then worked backwards using the laws of gravity to deduce how much matter of any type is present.
If dark matter existed, conventional theories hold it should surround our Milky Way like a halo, as it does other galaxies. The new findings don’t utterly rule out such a halo, but it would have to take a very unlikely shape to avoid penetrating our part of the galaxy, so things look awkward for dark matter theory, Bidin and colleagues suggested. Team members have also noted that the new results mean that attempts to detect dark matter on Earth by trying to spot the rare interactions between dark matter particles and “normal” matter are likely to fail.
The difficulties in clarifying the nature of dark matter, or in finding it on Earth, have annoyed scientists, but not to the point that most of them would doubt its existence. Future surveys, such as the European Space Agency’s Gaia mission, will be important in moving beyond these questions.
To learn more about the search for dark energy and dark matter, visit these URLs.
ESO La Silla Observatory: http://www.ls.eso.org/
Dark Energy and Dark Matter (a NASA Astrophysics article):
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Friday, April 20, 2012
Every Planet Deserves a Home
The above image from 2011 is an artist's concept of how a Jupiter-like rogue planet might appear as it drifted through space. Image Credit: NASA/JPL-Caltech
There is new research suggesting that billions of stars in our galaxy have captured rogue planets that once roamed between stars.
These nomad worlds were kicked out of the star systems in which they formed. Astronomers propose that, occasionally, they could find a new home with a different sun. This theory could explain the existence of some planets that orbit surprisingly far from their stars. It could even explain the existence of a known double-planet system.
The new study, appearing in the April 20 issue of The Astrophysical Journal, is co-authored by Haggai Perets of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and Thijs Kouwenhoven of Peking University, China. Perets and Kouwenhoven created computer simulations of young star clusters containing free-floating planets. They found that if the number of rogue planets equaled the number of stars, then 3 to 6 percent of the stars would capture a planet over time. The more massive a star, the more likely it is to snag a planet drifting by.
They studied simulations of young star clusters because capture is presumed more likely when stars and free-floating planets are crowded together in a small space. Over time, the clusters disperse due to close interactions between the stars, so any planet-star encounters have to happen early in the cluster’s history.
Astronomers think that rogue planets are a natural consequence of star formation. The concept goes like this: Newborn star systems often contain multiple planets. If two planets interact, one can be ejected and become an interstellar traveler. But if the drifting body encounters a different star moving in the same direction at the same speed, it might hitch a ride and be gravitationally “adopted” by the new parent star.
Rather than nuzzling close to its new parent, a captured world tends to end up in an orbit hundreds or thousands of times farther from its star than Earth is from the sun. It is also likely that the new addition will have an orbit that is tilted relative to any native planets, and might even revolve around its star backward compared to the rest of the family.
Astronomers haven’t detected any clear-cut cases of captured planets yet. Imposters can be difficult to rule out. Gravitational interactions within a planetary system can throw a planet into a wide, tilted orbit that mimics the signature of a captured world, Perets and Kouwenhoven noted. Finding a planet in a distant orbit around a low-mass star would be a good sign of capture, because the planet-forming disk originally surrounding the star wouldn’t have had enough material to form the planet so far out, they argue.
Researcher say the European Southern Observatory (ESO) provided the best evidence to date in support of planetary capture. In 2006 the ESO announced the discovery of two planets (weighing 14 and 7 times that of Jupiter) orbiting each other without a star. The reasoning goes that they could have captured each other. This rogue double-planet system is the closest thing to a “smoking gun” on the theory of planetary capture. More study and statistics are needed.
Could our own Sol system harbor an alien world far beyond Pluto? Astronomers have not found anything yet. Large planets may be ruled out at this point, but some suggest it is possible that a small world might lurk on the fringes of our system. Sound like just an old sci-fi "B" movie plot? Maybe. And maybe not...
The Astrophysical Journal is a peer-reviewed scientific journal covery astronomy and astrophysics. To read more, visit the publication URL here: http://iopscience.iop.org/0004-637X
To learn more about exoplanets and NASA's planet-finding program, PlanetQuest, visit this URL: http://planetquest.jpl.nasa.gov/
To learn more about the work of the European Southern Observatory (ESO), visit their site here: http://www.eso.org/
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Thursday, April 19, 2012
The Lyrids for 2012
The above image depicts the radiant point of the Lyrid meteor shower. The Lyrid meteors will appear to radiate from apoint near Vega, the bright, blue-white star in the constellation Lyra (the Lyre). The outlines of the surrounding constellations are marked and labeled. The image was produced using Your Sky software by John Walker, available online at www.fourmilab.ch/yoursky/
It’s time, again, for the annual Lyrid meteor shower. Also called the April Lyrids, the meteors from this shower may be visible in the northern hemisphere from April 19 through 25 with the peak on Saturday/Sunday, April 21/22. A nearly-new moon on those dates will provide perfect dark-sky conditions for meteor watching.
This year forecasters estimate Lyrid rates of 10 to 20 per hour, with possible rates as high as 100 meteors per hour. Lyrids appear to originate from a point near the bright, blue-white star Vega in the constellation of Lyra (RA 18hrs 16min, Dec +34°).
The parent of this shower is Comet Thatcher (C/1861 G1). Meteors from this shower enter the atmosphere at 49 km/s, or 110,000 miles per hour. Most are of a modest brightness, but some can be as bright as the planet Venus and even leave in their wake a visible train of ionized gas.
Appearances of this shower have been traced back over 2,500 years. The earliest record of the Lyrid shower was in 687 BC. In 15 BC a spectacular Lyrid meteor storm was observed. One observer recorded that the "stars fell like rain." Brilliant Lyrid showers were also seen in 1803 and 1922, though an hourly rate of the meteors was not recorded.
Here are some helpful notes and tips for meteor watching...
In group observing for meteors, each person has his or her own section of the sky to patrol. Wide-field binoculars can help an observer confine his or her attention to their own piece of sky.
Meteor trails make interesting images. Also, amateurs with a shortwave radio receiver can "listen" to meteors. This is done by tuning the receiver to a very weak distant station, preferably above 15 megacycles. The volume is kept very low. When a meteor in the upper atmosphere ionizes a patch of air, creating momentary "reflector" for signals, the volume of the station's signal rises sharply. Doppler changes in pitch may occur. On a good morning, several hundred meteors may be heard.
Here are some neat things to include in your meteor-watching experience...
- Observe showers, alone or with groups.
- Count the number of meteors seen in an hour. If observing a shower, count the number per minute.
- On a star chart, plot the beginning and ending points of meteor trails.
- If a meteor falls in your vicinity, try to find it. Watch your local newspaper for a report. Find persons who saw the meteor fall and attempt to trace it. Cooperate with a nearby observatory or museum, if any.
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Wednesday, April 18, 2012
Cassini's April 16th Flyby of Enceladus
Raw image of the surface of Enceladus, taken by NASA's Cassini spacecraft on April 14, 2012, two days before the latest flyby. The image was taken approximately 115 miles (185 kilometers) from the surface. Image Credit: NASA/JPL-Caltech/Space Science Institute
Launched October 1997, the Cassini-Huygens Mission took on the challenge of exploring the Saturn System. The European Space Agency's Huygens probe was equipped with six instruments to study Titan, Saturn's largest moon. It landed on Titan's surface on January 14, 2005, and returned spectacular results. Meanwhile, Cassini's 12 instruments have returned a daily stream of data from Saturn's system since arriving at Saturn in 2004.
The Cassini-Huygens Mission completed its four-year assignment in June 2008. Following that, the spacecraft and team were given an extended mission, called the Cassini Equinox Mission, and successfully completed that in September 2010. Now, the still-healthy Cassini spacecraft is making new discoveries in a second extended mission called the Cassini Solstice Mission.
This mission extension goes through September 2017 and is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet's northern winter solstice, the extension will allow for the first study of a complete seasonal period.
Among the most important targets of the Cassini Solstice Mission are the moons Titan and Enceladus, as well as some of Saturn’s other icy moons. Towards the end of the mission, Cassini will make closer studies of the planet and its rings.
On April 14, NASA's Cassini spacecraft flew by the moon Enceladus at an altitude of about 46 miles (74 kilometers). This flyby was designed primarily for Cassini's ion and neutral mass spectrometer to analyze, or "taste," the composition of the moon's south polar plume as the spacecraft flew through it. Cassini's path took it along the length of Baghdad Sulcus, one of Enceladus' "tiger stripe" fractures from which jets of water ice, water vapor and organic compounds spray into space. At the time of the fly-by, Baghdad Sulcus was in darkness, but that was not an problem for Cassini's composite infrared spectrometer, which can see features by their surface temperatures and which also took measurements during the flyby.
As soon as daylight passed into the line of sight of Cassini's remote sensing instruments, Cassini's cameras acquired images of the surface. At the closest approach to the south polar plume, the wide-angle-camera image has some smearing from the movement of the spacecraft during the exposure, but still shows the surface in vivid detail.
Cassini's cameras also imaged the plume at a high phase angle as the satellite appeared as a thin crescent and the plume was backlit.
After the Enceladus encounter, Cassini passed the moon Tethys with a closest approach distance of about 5,700 miles (9,100 kilometers). This was Cassini's best imaging encounter with Tethys since a targeted encounter in September 2005. The 2005 encounter, with a closest approach distance of about 930 miles (1,500 kilometers), provided the images of Tethys with the best resolution and captured views of the side of Tethys that faces Saturn in its orbit. This new encounter examined the opposite side of Tethys, providing some of the highest-resolution images of the side that faces away from Saturn. Cassini acquired a 22-frame mosaic of this side, which features the large impact basin named Odysseus. Scientists will use these new data in conjunction with images from previous encounters to create digital elevation maps of the moon's surface.
And now, the mission particulars...
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena manages the mission for the agency's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations team is based at the Space Science Institute in Boulder, Colorado. JPL is a division of Caltech.
For more information about the Cassini-Huygens Mission and the mission extensions, visit http://saturn.jpl.nasa.gov/
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Tuesday, April 17, 2012
Monday's Solar Flare and CME
The above image shows the sun’s April 16th solar flare in progress. The image was taken by NASA's Solar Dynamics Observatory (SDO). Image Credit: NASA/SDO
Around 17:45 UTC on Monday, April 16th, magnetic fields on the sun's northeastern limb erupted, producing one of the most visually-spectacular explosions in years. NASA's Solar Dynamics Observatory (SDO) recorded the blast at extreme ultraviolet wavelengths. The event began as a large solar prominence that extended from the sun’s photosphere out to the corona. The prominence then broke apart, producing a coronal mass ejection (CME). Thankfully, the eruption, which registered M1.7 on the peak flux solar flare scale, was not aimed toward Earth. However, at the Space Weather Laboratory of NASA's Goddard Space Flight Center, analysts studied the trajectory of the cloud and found that the CME will hit the following spacecraft:
NASA's Solar-Terrestrial Relations Observatory “B” (STEREO-B)
http://stereo.gsfc.nasa.gov/
NASA’s Spitzer Space Telescope
http://www.spitzer.caltech.edu/
The Mars Science Laboratory (Mars Curiosity Rover), on route to Mars
http://www.nasa.gov/mission_pages/msl/
…and the planets Venus and Mars could also receive a glancing blow.
A movie of the event has been created using data from SDO, and is now available online. The movie shows the explosion at 304 Angstroms, a wavelength which traces plasma with a temperature around 80,000 K (143,540 degrees F): http://www.youtube.com/watch?v=MhuLpZS6fss
On an ominous note, Monday’s magnetic eruption confirmed suspicions that an active region of significance is rotating onto the Earth-facing side of the sun. Stay tuned...
To learn more about SDO and the study of space weather, visit these URLS:
NASA's Solar Dynamics Observatory (SDO), visit the mission site: http://sdo.gsfc.nasa.gov/
The Space Weather Laboratory (674) of NASA's Goddard Space Flight Center
http://science.gsfc.nasa.gov/heliophysics/spaceweather/
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