Astronomy Picture of the Day
July 2, 2014

Dione in broad Daylight
Dione in broad Daylight

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

When imaged with the Sun nearly behind (on the back of) the NASA - Cassini Spacecraft, the heavily scarred Surface of the Saturnian moon Dione lacks the shadows that emphasize the Surface Topography (---> Vertical Reliefs and Surface Depressions, basically). However, on the other hand, this kind of Viewing Geometry highlights the variations in brightness of the Surface itself, thus providing Planetary Scientists with further evidence of Dione's extremely active and (perhaps often) violent past. The Surface of Dione (which is approx. 700 miles, or about 1126,5 Km across) is covered by Craters, reminding us of the impacts that have shaped (almost) all of the worlds of our Solar System. Dione's Surface also bears Linear Features that suggest the occurrence of a strong Tectonic Activity in a very remote past.

The Lit Terrain seen here is on the Saturn-facing Hemisphere of Dione; North is up and rotated 33° to the right (Dx). The image was taken in Visible Light with the NASA - Cassini Spacecraft'S Narrow-Angle Camera on June 27, 2013. The view was obtained at a distance of approximately 810.000 miles (such as about 1.303.505 Million KiloMeters) from Dione and the image scale is roughly 5 miles (such as about 8,04 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 17166) 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 "Dione"), 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 Dione, 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 Dione - 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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