Electronic Observing Aid
MARS member Craig MacDougal came across an interesting snail mail that other members might like to review. It concerns an electronic device to assist those who record video of their observing sessions. It is a box that inserts a time display into the video signal using a GPS device (not included) as its time source. It would be good for occultations, eclipses and the like. Craig scanned both sides of the brochure and place them as JPEG files on his web space.
Here is page 1:
http://mysite.verizon.net/macdouc/osd0001.jpg
…And here is page 2:
http://mysite.verizon.net/macdouc/osd0002.jpg
Please check it out!
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MARS IS COMING, PART 6
Just as a reminder, Mars will be closest to Earth on December 18/19 and will finally reach opposition with Earth on December 24. As we anticipate these dates please enjoy the next installment on the Red Planet Mars.
Surface Features, Part 1
We know about the character of the Martian terrain from spacecraft photography and altimetry. The Viking orbiters imaged the entire planet at a resolution of roughly 250 meters (820 feet) and selected areas at resolutions down to 10 meters (33 feet). Later the Mars Global Surveyor spacecraft imaged selected areas with resolutions of 1.4 meters (4.6 feet), but it covered only a small fraction of the planet. However, the topography of the Martian surface was determined very accurately with the laser altimeter aboard Mars Global Surveyor, which mapped elevations with a vertical resolution of a few meters.
Despite its small size, Mars has a greater range of elevation than Earth. The lowest point on the planet, within the Hellas impact basin, is 8 km (5 miles) below the reference level. The highest point, at the summit of the volcano Olympus Mons, is 21 km (13 miles) above the reference level. So the elevation range is 29 km (18 miles), compared with about 20 km (12.4 miles) on Earth (or, from the bottom of the Mariana Trench to the top of Mount Everest). Because Mars has no oceans, a reference level for elevations had to be defined in terms other than sea level. At first, in the early 1970s, the elevation at which the atmospheric pressure is 6.l millibars (about 0.006 of the sea-level pressure on Earth) was set as the reference. Later, when Mars Global Surveyor acquired more accurate elevation data, a better reference was needed, and the planet's mean radius of 3,389.51 km (2,106.14 miles) was chosen.
As we noted in our first installment, one of the most striking aspects of the Martian surface is the contrast between the southern and northern hemispheres. Most of the southern hemisphere is upland and heavily cratered, resembling the battered highlands of the Moon. Most of the northern hemisphere is lowland and volcanic with few craters. The difference in mean elevation between the two hemispheres is roughly 6 km (3.7 miles). The topographic boundary between the hemispheres is not at the equator but in a very jagged line around 30° north latitude. In some places the boundary is broad and irregular; in other places there are steep cliffs. Some of the most intensely eroded areas on Mars occur along the boundary. Landforms there include outflow channels, areas of collapse called chaotic terrain, and an enigmatic mix of valleys and ridges known as fretted terrain. Straddling the two hemispheres on one side of the planet is the Tharsis rise, a vast volcanic dome standing 8 km (5 miles) above Mars's mean radius, 12 km (7.5 miles) above the northern plains, and more than 2 km (1.2 miles) above the surrounding cratered southern highlands. On or near the Tharsis rise are the planet's largest volcanoes (see the section Tharsis and Elysium, below). Conspicuously absent in either hemisphere are the types of landforms that on Earth result from plate tectonics—for example, long linear mountain chains similar to the Andes, oceanic trenches, or a global system of interconnected ridges.
The reason for the differences between the hemispheres is one of many unexplained Martian mysteries—it may have formed when one or more large asteroids collided with Mars early in its history or as a result of internal changes that occurred when the planetary core formed. Gravity data acquired by Mars Global Surveyor suggests that the Martian crust is much thicker under the southern highlands than under the northern plains.
The number of very large craters in the southern highlands implies the surface is very, very old. Planetary scientists have established from lunar samples returned by Apollo missions that the rate of large asteroid impacts on the Moon declined rapidly between 3.8 billion and 3.5 billion years ago. Surfaces that formed before this time are heavily cratered; those that formed after are less so. Mars very likely had a similar cratering history. Thus, the southern highlands probably formed more than 3.5 billion years ago.
The southern terrain has many different types of craters—huge impact basins; large, partially filled craters with shallow, flat floors and eroded rims; smaller, fresh-looking bowl-shaped craters like those on the Moon; and rampart and pedestal craters. Hellas is the largest impact basin on Mars. According to Mars Global Surveyor altimetry data, the feature is about 7,000 km (4,400 miles) across, including the broad elevated ring that surrounds the depression, and 8 km (5 miles) deep—much larger than was previously thought. Most of the craters measuring tens to hundreds of kilometers across are highly eroded. Because larger craters tend to be older than smaller ones, erosion rates on early Mars appear to have been much higher than on later Mars. It is one reason why we think the climate on early Mars was very different from what it was for most of the planet's later history.
Rampart craters and pedestal craters may be unique to Mars. A rampart crater gets its name from the lobes of ejecta—the material thrown out from the crater and extending around it—are bordered with a low ridge, or rampart. So the ejecta apparently flowed across the ground, which may indicate that it had a mudlike consistency. Some scientists have suggested that the mud formed from a mixture of impact debris and water that was present under the surface. Around a pedestal crater, the ejected material forms a steep-sided platform, or pedestal, with the crater situated inside its border. The pedestal appears to have developed when wind carved away the surface layer of the surrounding region while leaving intact that portion protected by the overlying ejecta.
The high-resolution Viking images showed us an additional characteristic of the ancient southern terrain—the many networks of small valleys that look like the terrestrial drainage systems that are created by flowing water. Examples include Nirgal Vallis, located in the southern hemisphere north of the Argyre impact basin, and Nanedi Vallis, located just north of the equator near the east end of Valles Marineris. Scientists have suggested two alternative methods for their formation, either the runoff of rainfall on the surface or erosion by the outflow of groundwater that seeped onto the surface. In either case, warm climatic conditions may have been required for their formation. A major surprise of the Mars Global Surveyor mission was the observation of small, fresh-appearing gullies on steep slopes at high latitudes. These features look very much like water-worn gullies in Earth's desert regions, but their origin is still hotly debated. Although the discoverers initially proposed they were caused by water erosion, this was challenged by other researchers.
Next time: “Surface Features, Part 2”
Bibliography
Mars. (2007). In Encyclopædia Britannica. Retrieved October 26, 2007 , from Encyclopædia Britannica Online: http://www.britannica.com/eb/article-9110149
Mars (2007). In The Columbia Encyclopedia, Sixth Edition 2007. Copyright 2007 Columbia University Press. Retrieved October 26, 2007 from Encyclopedia.com
http://www.encyclopedia.com/doc/1E1-Mars-ast.html
Planets: Mars. In NASA Solar System Exploration, Last updated October 23, 2007. Retrieved October 26, 2007, from the NASA Solar System Exploration website, maintained by NASA's Jet Propulsion Laboratory:
http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mars
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THE SKY THIS WEEK
Dec 12 – the Moon occults Asteroid 4 Vesta
Dec 13 – Peak of the Geminid meteor shower
Dec 14 – the Moon occults the planet Neptune
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THIS WEEK IN HISTORY
Dec 10, 1950 – St. Louis meteorite fall, which hit a car
Dec 10, 1974 – Launch of the Helios 1 solar orbiter mission
Dec 10, 1984 – Claxton meteorite fall, hit a mailbox
Dec 10, 1992 – Mihonoseki meteorite fall, 15th anniversary, which fell through the roof of a house in Japan
Dec 10, 1999 – Launch of the X-ray Multi-Mirror Mission (XMM-Newton)
Dec 12, 1961 – Launch of Oscar 1
Dec 12, 1967 – Pioneer 8 launch, 40th anniversary
Dec 12, 2004 – Landing of Mars Exploration Rover “Opportunity”
Dec 13, 1867 – 140th birthday of Kristian Olaf Bernhard Birkeland
Dec 13, 1904 – Birthday of Sir William Hunter McCrea
Dec 13, 1972 – Apollo 17 lifted off from the moon; 35 years since a human walked on the moon
Dec 14, 1546 – Tycho Brahe’s birthday
Dec 14, 1962 – Mariner 2, Venus flyby, 45th anniversary
Dec 15, 1965 – Launch of NASA’s Gemini 6, Earth-orbital mission with astronauts Walter Schirra and Thomas Stafford
Dec 15, 1966 - Audouin Dollfus' discovery of Saturn’s moon Janus
Dec 15, 1970 – Landing of Soviet probe Venera 7 on Venus
Dec 15, 1984 – Launch of Vega 1, the Soviet Venus/Comet Halley mission
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MUSICAL DIVERSION
Bunessan is a small village on the Ross of Mull in the south of the island of Mull on the west coast of Scotland. The village name in Scottish Gaelic is Bun Easain, meaning “Foot of the little waterfall,” referring to a nearby waterfall. The village was originally a small community of farmers that practiced the Scottish farming tradition called crofting. In crofting, the landowner or their tenant, called the crofter, worked their holding, the croft, to make a living from the fruit of the land and the fruit of their labors. In many crofting communities the adjacent crofters practiced different endeavors that complemented and benefited each other. Until the 1900s, Bunessan had a mill, weavers and a small fishing fleet.
Not far from Bunessan, in the crofting community of Ardtun, lived Mary Macdonald (1789 – 1872), the daughter of a Baptist cleric who wrote songs and poetry in her native language of Gaelic. One of her songs told the story of the birth of the baby Jesus, who was foretold by prophets, announced by angels, lord of all, yet sleeping in a humble feed trough. Macdonald set her words to the tune of a traditional Gaelic melody. She called the song “Leanabh an Àigh” (Child in the Manger).
Leanabh an Àigh
Leanabh an àigh, an Leanabh aig Màiri
Rugadh san stàball, Rìgh nan Dùl;
Thàinig do’n fhàsach, dh’fhuiling ’n ar n-àite
Son’ iad an àireamh bhitheas dhà dlùth!
Ged a bhios leanabain aig rìghrean na talmhainn
An greadhnachas garbh is anabarr mùirn,
’S geàrr gus am falbh iad, ’s fasaidh iad anfhann,
An àilleachd ’s an dealbh a’ searg san ùir.
Cha b’ionann ’s an t-Uan thàinig gur fuasgladh
Iriosal, stuama ghluais e’n tùs;
E naomh gun truailleachd, Cruithfhear an t-sluaigh,
Dh’éirich e suas le buaidh o ùir.
Leanabh an àigh, mar dh’aithris na fàidhean;
’S na h-àinglean àrd’, b’e miann an sùl;
’S E ’s airidh air gràdh ’s air urram thoirt dhà
Sona an àireamh bhitheas dhà dlùth.
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A few decades later, the song was revived by a fellow Scott, Lachlan Macbean (1853 – 1931). Macbean edited The Fifeshire Advertiser, a newspaper in Kirkcaldy. In addition to his day job, Macbean had a passion for resurrecting nearly forgotten Gaelic songs. One of his published collections, entitled “Songs and Hymns of the Gael” (Edinburgh, Scotland: 1888) included an English translation of Macdonald’s song of the child in the manger. In her memory, Macbean named the song’s melody “Bunessan,” after the nearby village.
Child in the Manger
Child in the manger, Infant of Mary,
Outcast and Stranger, Lord of all,
Child Who inherits all our transgressions,
All our demerits on Him fall.
Once the most holy Child of salvation
Gently and lowly lived below.
Now as our glorious mighty Redeemer,
See Him victorious o’er each foe.
Prophets foretold Him, Infant of wonder;
Angels behold Him on His throne.
Worthy our Savior of all our praises;
Happy forever are His own.
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In 1922, English author Eleanor Farjeon (1881 – 1965) wrote a poem entitled “A Morning Song (For the First Day of Spring). The words were set to the “Bunessan” melody, creating the hymn we know today as “Morning Has Broken.” Though not all of the words are typically sung today, the full text follows.
Morning Has Broken
Morning has broken, like the first morning
Blackbird has spoken, like the first bird
Praise for the singing, praise for the morning
Praise for the springing fresh from the word
Sweet the rain's new fall, sunlit from heaven
Like the first dewfall, on the first grass
Praise for the sweetness of the wet garden
Sprung in completeness where his feet pass
Mine is the sunlight, mine is the morning
Born of the one light, Eden saw play
Praise with elation, praise every morning
God's recreation of the new day
(Below is the second have of Farjeon’s text.)
Cool the gray clouds roll, peaking the mountains,
Gull in her free flight, swooping the skies:
Praise for the mystery misting the morning
Behind the shadow, waiting to shine.
I am the sunrise, warming the heavens,
Spilling my warm glow, over the earth:
Praise for the brightness of this new morning
Filling my spirit with Your great love.
Mine is a turning, mine is a new life;
Mine is a journey closer to You:
Praise for the sweet glimpse caught in a moment,
Joy breathing deeply, dancing in flight.
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In 1969, a Jesuit priest, Rev. James Quinn, published a collection of new songs entitled, “New Hymns for All Seasons” (London). One of his songs was set to the “Bunessan” melody. The text, called “St. Patrick’s Breastplate,” is a morning prayer for strength and guidance through the coming day. The song is also called by its first line, “This Day God Gives Me.”
This Day God Gives Me
(St. Patrick's Breastplate)
This day God gives me Strength of high heaven
Sun and Moon shining, Flame in my hearth
Flashing of lightning, Wind in its swiftness,
Deeps of the ocean, Firmness of earth.
This day God sends me Strength as my guardian,
Might to uphold me, Wisdom as guide.
Your eyes are watchful, your ears are list’ning,
Your lips are speaking, Friend at my side.
God’s way is my way, God’s shield is ‘round me,
God’s host defends me, Saving from ill.
Angels of heaven, Drive from me always
All that would harm me, Stand by me still.
Rising I thank you, Mighty and Strong One
King of creation, Giver of rest.
Firmly confessing Threeness of Persons
Oneness of Godhead, Trinity blest.
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Today, the Scottish village of Bunessan has a population of roughly 200, and includes surrounding areas of Millbrae, Fountainhead and Ardtun. There is a monument to Mary Macdonald near the village, on the road toward Craignure, just after the Knockan crossroads. The ruins of her house can still be found nearby.
To see and hear more on the hymn, “Leanabh an Àigh,” visit this page of "The Cyber Hymnal" - http://www.cyberhymnal.org/non/gd/leanabh.htm
To see and hear more on the hymn, “Child in the Manger,” visit this page of “The Cyber Hymnal” - http://www.cyberhymnal.org/htm/c/h/childman.htm
To see and hear more on the hymn, “Morning Has Broken,” visit this page of “The Cyber Hymnal” - http://www.allspirit.co.uk/morning.html
To view the text of the hymn, “This Day God Gives Me,” visit this Web page:
http://www.janson.com/info/prayer.html
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