Astronomy Picture of the Day
August 29, 2015

Dione (Part II)
Dione (Part II)

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

This beautiful view obtained by the NASA - Cassini Spacecraft shows us highly cratered and irregularly-shaped terrain on Saturn's moon Dione that is entirely (and ONLY!) lit by reflected light coming from from Saturn (a phenomenon known as "Saturnshine"). Imaging Scientists set a relatively short exposure time (10 milliseconds) for this and other views obtained during this fast Fly-By in order to avoid smearing the images. Despite the short exposure time, the light from Saturn was sufficient to provide a good look at many Surface Features located on the Dione's Night (or even "Dark") Side.


The image was acquired in Visible Light with the NASA - Cassini Spacecraft Wide-Angle Camera during a close Fly-By of the Dione which took place on August, 17, 2015. The view was acquired at an altitude of approximately 600 miles (such as about 965,604 Km) above Dione and has an image scale of about 190 feet (such as approx. 57,912 meters) per pixel. North on Dione is located toward the upper right (Dx) corner of the frame.


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 19652) 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 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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