Astronomy Picture of the Day
January 29, 2013

Tyre Crater
Tyre Crater

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

This unbelievably complex Surface Feature located on the Jovian moon Europa was originally seen as a dark, diffuse Circular Patch on a previous NASA - Galileo Spacecraft's global image of Europa's Leading Hemisphere taken on April 3, 1997. The "Bulls-Eye" pattern appears to be a 140- Km-wide Impact "Scar" (about the size of the island of Hawaii) which formed as the Surface of Europa fractured minutes after a (probably) mountain-sized Asteroid or Comet slammed into this fascinating Celestial Body.

This approx. 214-Km-wide picture is the product of the combination of 3 (three) images which have originally been processed in false colors, so to enhance shapes and compositions of the photographed Surface. North is toward the top of this picture, which is illuminated from Sunlight coming from the West. This composite reveals a sequence of events which have deeply modified the Surface of Europa. The earliest event was the impact which formed the Tyre Structure, located at 34° North Latitude and 146,5° West Longitude. The impact was then followed by the formation of the brown/reddish lines superposed on Tyre. The brown/reddish color, in fact, designates areas that are probably made of (or covered by) some kind of a "dirty" Water-Ice Mixture. On the other hand, the fine light blue-gray lines crossing the whole Region from West to East appear to be Ridges which (obviously) formed after the Crater.

The images forming this composite were taken on April 4, 1997, at a resolution of 595 meters (1950 feet) per picture element and a range of approx. 29.000 Km (such as about 18.000 miles) from Europa. The frames were taken by Galileo's Solid State Imaging (CCD) System.

This frame (which is the Original NASA - Galileo Spacecraft false-color image composite published on the NASA - Planetary Photojournal with the ID n. PIA 00702) has been additionally processed and then re-colorized, according to an educated guess carried out 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 Surface of the Jovian moon Europa), 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 Europa, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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