Astronomy Picture of the Day
September 26, 2012

Eye in the Sky...
Eye in the Sky...

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

Mimas is one of the very many moons of the Gas Giant Planet Saturn; it was discovered in the AD 1789 by Sir William F. Herschel, a German-born, British astronomer and then named after the Greek Mythological Deity Mimas: a Titan, son of Gaia. However, Mimas can also be generally designated and referred to as Saturn I.

With a diameter of approx. 396 Km (such as about 246 miles), Mimas is the 20th largest moon in the Solar System and, at the same time, the smallest Celestial Body that is known to be rounded (---> oblate) in shape because of the occurrence of a phenomenon known as "self-gravitation". The NASA - Cassini Spacecraft took this suggestive picture of Mimas that shows us the huge Herschel Crater which, as you can easily notice, looks like the iris of an eye, peering out into the Outer Saturnian Space. Herschel Crater is about 130 Km (such as approx. 81 miles) wide and it covers most of the top of the image and the impact that created it must have nearly shattered Mimas: in fact, deep Surface Fractures can be seen on the opposide side of Mimas (---> as to Herschel Crater) and this circumstance made Scientists believe that these Fractures could have been created by powerful Shock Waves that generated from the Impact Site and then travelled throughout the whole moon's body. The Mimantean Surface is generally saturated with smaller Impact Craters, but no others are anywhere near the size of Herschel. In addition, although Mimas is heavily cratered, the cratering tself is not uniform: consider, for instance, that most of its Surface is covered with Impact Craters having a diameter that is larger than 40 Km (such as approx. 25 miles) but, in the South Polar Regions of Mimas, there are no Impact Craters possessing a size that is remarkable as the one of the other Impact Features that cover the rest of this fascinating Celestial Body.

The Lit Terrain seen in this frame is on the Leading Hemisphere of Mimas; North is up and rotated to the left. The image was taken in Visible Light with the NASA - Cassini Spacecraft Narrow-Angle Camera on October, 16, 2010. The view was obtained at a distance of approx. 103.000 Km (such as about 64.000 miles) from Mimas, and at a Sun-Mimas-Spacecraft, or Phase, Angle of 113°; the image scale is roughly 613 meters (such as 2011 feet) per pixel.

This frame (which is an Original NASA - CASSINI Spacecraft b/w frame published on the NASA - Planetary Photojournal with the n. PIA 12739) has been additionally processed and then colorized, according to an informed speculation 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 - CASSINI Spacecraft and then looked outside, towards the Saturnian moon Mimas), 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 Mimas, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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