Astronomy Picture of the Day
February 22, 2014

Wispy Terrain (EDM - The 'Straight Line')
Wispy Terrain (EDM - The 'Straight Line')

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

As we wrote in yesterday's APOD, this is a really well detailed image that was taken by the NASA - Cassini Spacecraft during its closest approach to the Saturnian moon Dione, which occurred more than nine years ago (such as on December, 14, 2004). The Context (CTX) Frame was centered on the so-called "Wispy" (---> thin) Terrain of the moon and, to the surprise of the Cassini Imaging Scientists, the aforementioned Wispy Terrain did not (seem to) consist of thick Ice-rich Deposits but, rather, of extremely bright Ice Cliffs, most likely created in a very remote time (but, Geologically speaking, they appear quite recent!), by the action of powerful Tectonic Processes (---> i.e.: Surface Fracturing).

As far as the "curiosity" (one the many, as usual) that we talked about in yesterday's APOD is concerned, we, as IPF, noted a very unusually-looking Feature on the Surface of Dione (very well shown in this Extra Detail Magnification) and said Feature does NOT seem to be (of course, in our humble opinion) a Tectonic Fracture. If you notice, its simple orientation, for instance, is completely inconsistent (please, if you wish, verify this element by yourself) with the orientation of all the other Wispy Fractures that can be seen nearby and which were were captured in the Contextual Image.

As a matter of fact, this bright and "Straight Line" (actually, we believe that it is a really thin Crater Chain) that is so well visible here, could reasonably be the final result of a Cometary Impact (like we have already seen that it occurred on the Jovian moons Ganymede and Callistus) or, maybe, the visible effect of a series of sequential impacts caused by the fragments of a of a Celestial Object (other than a Comet) which did not successufully pass Dione's "Roche Limit".

This means that the incoming Celestial Object, during its approach to Dione - or, perhaps, even earlier -, broke into pieces and then these pieces, one after the other, fell on the Surface of this Icy Saturnian moon (just like it happened for the "alleged" - and, if they ever actually existed, short-lived - "Rings" of Rhea) leaving behind this almost perfect bright and "Straight Line" of tiny Impact Features.

If you have a different opinion about the (possible) true nature of this Surface Detail, please share it with us. The only thing you have to do is to write a message to this address: . Every opinion shall be taken into duly consideration, and evaluated in good faith.

This image (which is a crop taken from an Original NASA - Cassini Spacecraft b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 06163) has been additionally processed, contrast enhanced, magnified to aid visibility of the Surface details and then colorized 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 others, the existence of different Elements 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, way lower than it has been shown (or, better yet: interpreted) here.

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