Astronomy Picture of the Day
January 18, 2013

A colorful Good-Bye to Io
A colorful Good-Bye to Io

Credits: NASA/JPL/Univ. of Arizona - Galileo Project - Credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/IPF

To say "Good-bye" (but just for now...) to the Jovian volcanic moon Io, we chose to show you, in today's APOD, the unbelievable features of Culann Patera: one of the most active and colorful Volcanic Centers of Io. This mosaic was obtained by putting toghether a few of the best High-Resolution Color Views of Io ever returned by the NASA - Galileo Spacecraft; it was constructed from images taken through the Red, Green, and Violet Filters of the Camera onboard the Spacecraft and, finally, it has also been additionally processed (first by NASA, and then by the IPF) in a way and manner that were fit not only to enhance, but even to render as much realistic as possible the color variations of the whole pictured Landscape. The resolution of the mosaic is about 200 meters per picture element, North is towards the top and the images forming it were taken on November 25, of the AD 1999, during Galileo's 25th orbit (at a distance of approx. 20.000 Km - such as about 12.420 miles - from Io).

The Mosaic shows the complex relationships existing among the diffuse Red and Yellow Deposits, the more confined Green Deposit, and the various (multi-colored) Lava Flows existing and active in this Region. Culann's Central Caldera (above and to the right of center of the mosaic) has a highly irregular, scalloped Margin and a pale gray/green-colored Floor. Lava Flows spill out of the Caldera on all sides: a dark red, curving line extending North/West from the South/Western tip of the Caldera may mark a "crusted-over" Lava Tube feeding the dark (and hot) Silicate Flows which are heading to the North/West. Unusual dark red Flows to the South/East of the Caldera may be Sulphur or Silicate Flows whose Surfaces have been modified. The diffuse Red Material vissible around the Caldera is believed to be a compound of Sulphur that was deposited by a Gas-Plume, while the outher halo of (also diffuse) Yellow Material should be a huge blanket of pure Sulphur (with, most likely, traces of other Sulphur Compounds). 

Furthermore, Culann's Caldera and several Lava Flows extending from the Caldera itself appear to be coated by greenish Materials. Green Material can also be seen in the Caldera to the lower right of the image, in an area named "Tohil Patera". The greenish Material often has sharp boundaries, so it is apparently confined to the Caldera Floor as well as to the Dark Flows. Galileo scientists investigatied for a long time the possibility that the greenish Material formed a coating of Sulphur-rich Material on just warm Silicate Lavas, but a final and trustworthy answer to this question is still far away from being reached.

This picture (which is an Original NASA - Galileo Orbiter false color image mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 02535) has been additionally processed and then re-colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Galileo Orbiter and then looked down, towards the Surface of the Jovian moon Io), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Io, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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