Monday, July 02, 2012

Io's Heat Flow Is Baffling

The above image is a mapping of thermal emissions on Jovian moon Io. The emissions are from erupting volcanoes. A logarithmic scale is used to classify volcanoes on the basis of thermal emission: the larger the spot, the larger the thermal emission. Image credit: NASA/JPL-Caltech/Bear Fight Institute

A new study finds that the pattern of heat coming from volcanoes on Io's surface contradicts the generally-accepted model of internal heating.  The heat pouring out of Io's hundreds of erupting volcanoes indicates a complex, multi-layer source.  These results come from data collected by NASA spacecraft and ground-based telescopes and appeared in the June issue of the journal Icarus. The journal may be visited online at this URL:

A map of hot spots, classified by the amount of heat being emitted, shows the global distribution and wide range of volcanic activity on Io. And we are talking big booms, here. Most of Io's eruptions dwarf their contemporaries on Earth.

This study of Io's volcanic thermal emission is the most comprehensive to date. The work was led by Glenn Veeder of the Bear Fight Institute, Winthrop, Washington. The multi-faceted team included Ashley Davies, Torrence Johnson and Dennis Matson of NASA's Jet Propulsion Laboratory, Pasadena, California, Jani Radebaugh of Brigham Young University, in Provo, Utah, and David Williams of Arizona State University, Tempe, Arizona. The team examined data primarily from the NASA's Voyager and Galileo missions, but also incorporated infrared data obtained from telescopes on Earth.

The team was most fascinated about the unexpected findings regarding Io's heat flow. Specifically, that the distribution of Io's heat flow does not match the currently preferred Io model of tidal heating at relatively shallow depths. Instead, the main thermal emissions occur about 40 degrees eastward of their expected positions. The pattern points to a complex heating process within Io, with a mixture of both deep and shallow heating.

A mystery has also emerged.  The team found that active volcanoes accounted for only about 60 percent of Io's heat.  This component mostly emanates from flat-floored volcanic craters called paterae, a common feature on Io.  But where is the "missing" 40 percent?  The team is investigating the possibility that there are many smaller volcanoes that are difficult, but not impossible, to detect. Currently, they are puzzling over the observed pattern of heat flow.

Understanding this will help identify the tidal heating mechanisms not only within Io, but also may apply to neighboring Europa, a high-priority target for NASA in its search for life beyond Earth. 

And now, the mission particulars...

The Galileo mission was managed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, for the agency's Science Mission Directorate. The mission was launched by the space shuttle Atlantis in 1989 to Jupiter, produced numerous discoveries and provided scientists decades worth of data to analyze. Galileo was the first spacecraft to directly measure Jupiter's atmosphere with a probe and conduct long-term observations of the Jovian system. NASA extended the mission three times to take advantage of Galileo's unique science capabilities, and the spacecraft was put on a collision course into Jupiter's atmosphere in September 2003 to eliminate any chance of impacting Europa. JPL is a division of the California Institute of Technology in Pasadena.

For more information about the Galileo mission, visit: .

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