Wednesday, February 24, 2010

Galileo I32 Terminator Mosaic

During Galileo's flyby of Io on October 16, 2001 (I32), the spacecraft's camera acquired two mosaics along its terminator that at the time ran along 175-180° West longitude.  One mosaic covered the southern hemisphere section, cutting across Michabo Patera, Tsui Goab, Culann, Tohil, and Mycenae Regio.  The Galileo imaging team released a version of that mosaic colorized with data from C21 a year later.

The other mosaic was to cover the northern hemisphere portion of the terrain near the terminator, useful for observing topographic features such as mountains.  However, during the previous Io encounter, Galileo discovered a new outburst eruption at Thor where no previous activity had been observed.  The imaging team decided to adjust the layout of this second terminator mosaic so that it would also cover Thor.  The result was the TERMIN02 mosaic that was returned following the October 2001 flyby.  What I wanted to present here is a colorization I have done of this clear-filter mosaic, combining it with color data from three orbits: E4, C21, and I31.  The full-resolution version of this color mosaic is also available.  The Thor eruption site is at top right and the Zamama plume site is at lower left.  At Zamama and at several other sites across the mosaic, we see shield volcanoes, volcanoes where lava has slowly built up a broad mountain with shallow slopes for the most part with the exception of basal scarps along their margin.  You can see similar morphology on a much larger scale at Olympus Mons on Mars.  You can also see areas where lava has craved broad channels into the sides of these shield volcanoes and onto the plains.


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