Astronomy Picture of the Day
January 12, 2013

Moments of Thebe
Moments of Thebe

Credits: NASA/JPL/Cornell University and Dr Paolo C. Fienga/LXTT/IPF for the additional process. and color.

These two images of the Jovian Inner moon Thebe were taken by the NASA - Galileo Spacecraft's Solid State Imaging System in November 1996 (left frame - Sx) and June 1997 (right frame - Dx), respectively. North is approximately up in both cases. Thebe, whose longest dimension is about 116 Km (or approx. 72 miles) across, is tidally locked (---> meaning that Thebe rotates synchronously with its Orbital Motion) to its Parent Planet, so that the same side of this satellite always points towards Jupiter, (and just like it happens to our own Moon, which always points its so-called "Near Side"- or Nearside -  towards the Planet Earth. Moving in such a tidally locked state, one side of Thebe always points in the direction in which Thebe moves as it orbits about Jupiter, and this Side (or Hemisphere) is called the "Leading Side/Hemisphere" of the moon (and here it is shown in the left image). The frame on the right, instead, emphasizes the Side/Hemisphere of Thebe that always faces away from Jupiter (which is the so-called "Anti-Jupiter" Side/Hemisphere).

If you watch carefully the two frames (even though their quality is not perfect), you will notice that there appear to be at least 3 (three) or maybe 4 (four) very large Impact Craters on this small moon - very large in the sense that each of these Impact Craters is roughly comparable in size to the Mean Radius itself of Thebe (given that the approximate dimensions of Thebe are 116 x 98 x 84 Km, its Mean Radius, therefore, should be about 49,3 Km, with an approx. of ± 2 Km).

This frame (which is the Original NASA - Galileo b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 01075) has been additionally processed and then colorized, according to an educated guess, by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Galileo Spacecraft and then looked outside, towards the Jovian moon Thebe), 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 Thebe, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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