Astronomy Picture of the Day
September 28, 2012

Volcanic Plains near Galai Patera on Io
Volcanic Plains near Galai Patera on Io

Credits: NASA/JPL/USGS - Voyager 1 Project; Credits fo the additional process. and color.: Dr Paolo C. Fienga/LXTT/IPF

Io's Volcanic Plains and at least 9 (nine) Paterae are shown, once again, in this really beautiful and highly suggestive NASA - Voyager 1 Space Probe image, which spans an area of about 1030 Km (such as approx. 640 miles) from left to right. North is at about the 01:30 o'clock position on the frame. A number of active Volcanic Calderae and huge Lava Flows are visible here: the most important (both for size and activity) is the dark red "teardrop-shaped" Surface Feature visible near the center of the frame, slightly to the right, which is Galai Patera, an approx. 100-Km-long (such as about 62 miles) Lava-flooded Caldera (---> Collapsed Vent). As we have already mentioned in yesterday's APOD, the exact composition of Io's Volcanic Plains and Lava Flows has not been determined yet; however, the prevalent yellow, brown, and orange materials may consist, dominantly, of Sulphur, with Surface Frosts made of Sulphur Dioxide and Silicates (such as Basalt), encrusted with Sulphur and Sulphur Dioxide Condensates. The dark red (and, sometime, almost black) spots visible all around the frame, of course including Galai Patera, are hot Sulphur Lava Lakes, which may remain molten for a long time, thanks to the intrusions of molten Silicate Magma that (probably in an almost continuous way) comes up from deep inside Io. Finally, the whitish patches visible at the upper left corner, in the center and on the lower left side of the picture are, most likely, Fresh Deposits of Sulphur Dioxide Frost.

This picture (which is an Original NASA - Voyager 1 Space Proble color image mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 00324) 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 - Voyager 1 Space Probe and then looked outside, towards the limb 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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