Astronomy Picture of the Day
January 23, 2015

Crescent Janus
Crescent Janus

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

Janus (approx. 111 miles - or about 178,636 Km - across), in this magnificent picture taken by the NASA - Cassini Spacecraft, seems to stare off (---> look deeply) into the distance, contemplating the boundless Beauty of the Saturnian System.

From this image, it is easy to distinguish Janus' shape from the one of a simple "sphere" and, in fact, many of Saturn's smaller moons have similarly irregular shapes that Planetary Scientists believe may give clues to their origins and Internal Structure. As a matter of fact, quite a few (but remember: just theoretical) Models - combining the dynamics of this moon with its shape -  seem to imply the existence of Mass Inhomogeneities within Janus. This circumstance, if and where confirmed, would be a surprising result for a Celestial Body as small as Janus. By studying more images of Janus, Planetary Scientists may, in the future, be able confirm this finding and determine just how complicated the Internal Structure of this truly small Celestial Body (as well as many other ones that looks just like it) actually is.

This image is roughly centered on the side of Janus which always faces away from Saturn; North is up and rotated to the right (Dx). The picture was taken in Visible Light with the NASA - Cassini Spacecraft Narrow-Angle Camera on March 28, 2012, at a distance of approx. 54.000 miles (such as about 86.904,36 Km) from Janus. The image scale is roughly 1700 feet (such as approx. 518,160 meters) per pixel.

The frame (which is an Original NASA - CASSINI Spacecraft's b/w and NON Map-Projected image published on the NASA - Planetary Photojournal with the ID n. PIA 18299) has been additionally processed, contrast enhanced, magnified to aid the visibility of the details, Gamma corrected and then colorized - according to an educated guess (or, if you wish, an informed speculation) carried out by Dr Paolo C. Fienga - 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 "Janus"), 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 Janus, each having a different Albedo (---> Reflectivity) and Chemical Composition.

Note: it is possible (but we, as IPF, have no way to be one-hundred-percent sure of such a circumstance), that the actual luminosity of Janus - as it is in this frame - would appear, to an average human eye, a little bit lower than it has been shown (or, better yet: interpreted) here.

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