Astronomy Picture of the Day
December 24, 2013

Crescent Japetus
Crescent Japetus

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

Japetus (approx. 914 miles - such as about 1470,93 Km - in diameter), as you know, is a Saturnian moon of extreme contrasts: as a matter of fact, the light and dark Surface Features which characterize this fascinating Celestial Body, gave Japetus a distinctive - and so-called - "Yin and Yang" appearance.

A few Planetary Scientists believe that a runaway migration of Ice on the Surface, perhaps triggered by a "preferential initial darkening" - and consequential warming-up - of the Leading Hemisphere of Japetus, caused by (once again: perhaps) infalling Debris coming from the Outer Saurnian moon Phoebe, might have been responsible for its unusual and striking appearance.

This view, taken by the NASA - Cassini Spacecraft, looks toward the Saturn-facing Hemisphere of Japetus; North is up and rotated 30° to the right. The image was taken in Visible Light with the NASA - Cassini Spacecraft Narrow-Angle Camera on August 30, 2013. The view was obtained at a distance of approximately 1,5 Million Miles (such as approx. 2,414 Million KiloMeters) from Japetus. The Original Raw Frame scale is 9 miles (such as about 14,48 Km) per pixel.

This 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 17142) 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 "Japetus"), 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 Japetus, 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 Japetus - as it is in this frame - would appear, to an average human eye, quite a bit lower than it has been shown (or, better yet: interpreted) here.

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