Astronomy Picture of the Day
June 23, 2015

Triple Crescent in Saturn's Space
Triple Crescent in Saturn's Space

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

A single crescent Moon is a really familiar sight in Earth's Sky, but with Saturn's many moons, you can see three of them at the time, or even more.


The three moons shown here - such as Titan (that is about 3.200 miles, or approx. 5.149,888 Km across), Mimas (which is about 246 miles, or approx. 395,89 Km across), and Rhea (approx. 949 miles or about 1.527,26 Km across) - show marked contrasts from one another. Titan, the bright yellow-colored and largest moon visible in this image, appears fuzzy because we can only see its Cloud Layers. And since Titan's Atmosphere heavily refracts the light around it, Titan's crescent "wraps" just a little further around the moon itself than it would do - instead - on an airless Celestial Body (just like Rhea and Mimas).


Rhea (upper left - Sx) appears rough because its Icy Surface is heavily cratered. And a close inspection of Mimas (center bottom of the frame), though it is difficult to see at this scale, shows incredible Surface Irregularities which are due to its own violent Geological History.


This view looks toward the anti-Saturn Hemisphere of Titan; North is up. The image was taken in Visible Light with the NASA - Cassini Spacecraft's Narrow-Angle Camera on March 25, 2015. The picture was obtained at a distance of approximately 1,2 Million Miles (such as approx. 1.931.208 Million KiloMeters) from Titan.


The Image Scale for Titan is roughly 75 miles (such as about 120,7 Km) per pixel. Mimas, at the time when the picture was taken, was about 1,9 Million Miles (such as approx. 3.057.746 Million KiloMeters) away - with an Image Scale of roughly 11,4 miles (such as approx. 18,346 Km) per pixel. Last, but certainly not least, Rhea, was about 2,2 Million Miles (such as approx. 3.540.548 Million KiloMeters) distant from the NASA - Cassini Spacecraft, and its Image Scale of roughly 13,1 miles (such as about 21,08 Km) per picture element (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 18322) has been additionally processed, contrast enhanced, magnified, in order to allow the vision of the slightest details of the Surface, Gamma corrected and then re-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, toward the Saturnian moons "Titan", "Mimas" and "Rhea"), 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 (Gases and Minerals, respectively) present in the Atmosphere of Titan, and on the Surface of Mimas and Rhea, 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 Titan, Mimas and Rhea - 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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