Astronomy Picture of the Day
November 3, 2012

Phoebe
Phoebe

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

Phoebe's possible true nature is partly revealed in this image-mosaic of two frames taken during the NASA - CASSINI Spacecraft's Fly-By that occurred on June 11, 2004. The image shows evidence for the emerging view that Phoebe may be an ice-rich Celestial Body coated with a thin Layer of Dark Material (probably Dust). This phenomenon has been observed on other Icy Satellites, such as Ganymede, in the Jovian System: when an impactor slammed into the Surface of Phoebe, the collision excavated fresh, bright Material - probably Water Ice - underlying the Surface Layer of Dust and other rocky debris. A further evidence supporting this hypothesis can be seen on some Crater Walls where the darker Material appears to have slid downwards, so to expose more light-colored Material. However, some areas of the image that are particularly bright - especially near the lower right - are just over-exposed. Small bright Impact Craters visible in the picture are probably fairly young Surface Features.


In addition to that, a number of interesting circumstances seem to indicate that Phoebe may have originated in the Outer Solar System. In fact, Phoebe's highly irregular and Dark Surface, its retrograde orbit, the presence, on its Surface, of a huge variety of large and small Impact Craters and, last but not least, its extremely low Average Density, appear consistent with the hypothesis that Phoebe was once part of the Kuiper Belt, before being captured by Saturn's Gravity (which is, most likely, the same origin of quite a few Minor moons of the Gas-Giant Planets Uranus, Neptune, Saturn and Jupiter).


This spectacular view was obtained at a Phase, or Sun-Phoebe-Spacecraft, Angle of 84°, and from a distance of approximately 32.500 Km (such as aabout 20.200 miles). The image scale is approximately 190 meters (624 feet) per pixel.


These image-mosaic (which is made of two Original NASA - CASSINI Spacecraft b/w frames published on the NASA - Planetary Photojournal with the ID n. PIA 06064) have been additionally processed and then colorized, according to an informed speculation carried out by Dr Paolo C. Fienga (LXXT/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 Outer moon, Phoebe), 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 other things, the existence of different Elements (Minerals) present on the Surface of Phoebe, each having a different Albedo (---> Reflectivity) and Chemical Composition.



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