Astronomy Picture of the Day
September 16, 2013

Moving towards the Limb of Europa...
Moving towards the Limb of Europa...

Credits: NASA/JPL - Voyager 2 Project - Credits for the additional process. and color.: Dr Paolo C. Fienga/LXTT/IPF

This image of Europa (as you know, the smallest of Jupiter's 4 (four) so-called "Galilean Natural Satellites"), was acquired by the NASA - Voyager 2 Spacecraft on July 9, 1979, at a distance of approx. 242.367 Km (such as about 150.600 miles) from the its Frozen Surface. Europa, the brightest of the aforementioned four Galilean Natural Satellites of Jupiter, has a density slightly lower than the one of Io, and this circumstance suggests that Europa contains (---> is - also - made of) substantial quantities of Water. Many Planetary Scientists previously speculated that the Water must have cooled from the interior and formed a mantle of Ice perhaps about 100 Km (such as about 62,1 miles) thick, but it is also VERY possible (according to the latest discoveries on this Subject) that, due to the phenomenon known as Tidal Friction (a phenomenon which, basically, is fit to "warm up" the interior of a - relatively - small Celestial Body as a consequence of the passage, in its proximities, of its - here, gigantic - Parent Planet), somewhere, deep inside Europa, an Ocean made of liquid Water - and, perhaps, containing some kind of Exotic Lifeforms... - could still exist.

The extremely Complex Tectonic Patterns visible almost all over the Surface of Europa tell us that such an Icy Crust suffered a countless number of Fractures, and that the Cracks resulting from the Fractures were filled, at some point, with some kind of (still unknown) Dark Material coming from the Sub-Surface of this moon. Very few Impact Craters are visible on Europa, and this means - among other things - that some Geological Process is still occurring on its Surface and that it is fit to modify the whole exterior appearence of Europa itself. Furthermore (and as a matter of fact), the Tectonic Patterns seen on Europa's Icy Surface differ drastically from the - very large - Fault Systems which can be found on Ganymede (where huge pieces of its Crust seem to have - somehow - moved from their original positions - as relative to one another). On Europa, instead, the Crust - quite evidently -  suffers heavy Fracturing Processes, but the pieces resulting from these catastrophic events, remain (roughly - and for reasons still unknown) in their original positions.

Also, and still very well visible, at 6 o'clock of the frame, there are the same two Unnamed Maculae. that we had already spotted in yesterday's APOD.

This frame (which is an Original NASA - Voyeger 2 Spacecraft b/w image published on the NASA - Planetary Photojournal with the ID n. PIA 01503) has been additionally processed, contrast enhanced, magnified to aid visibility of the Surface details and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga/LXTT/IPF, in what they should be its Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 2 Spacecraft and then looked outside, towards the Jovian moon Europa), 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 Europa, each having a different Albedo (---> Reflectivity) and Chemical Composition.

Note 1: 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 Europa - 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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