Astronomy Picture of the Day
September 14, 2013

Europa's Maculae
Europa's Maculae

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

This image-mosaic of Europa's Southern Hemisphere was obtained by the Solid State Imaging (CCD) System onboard the NASA - Galileo Spacecraft during its 6th orbit of Jupiter. The upper left portion of the mosaic shows the Southern Extent of the so-called "Wedges" (---> Wedge means "triangle-shaped" ) Region of Europa: an area that, according to the speculations made by some NASA Scientists, should have suffered, in a very remote time of Europa's Geological History, an extensive disruption. South of the Wedges, the Eastern Extent of Agenor Linea (nearly 1000 Km - or about 621 miles - in length) is also visible. Thera Macula and Thrace Macula are the dark and irregularly shaped Surface Features visible to the South/East of Agenor Linea (just below the center of the image).


This mosaic was used by Planetary Scientists to build a Global Map of Europa by tying these (and way many other) Galileo images together with other images obtained in the AD 1979, during the Fly-By of the Jovian System that was done by the NASA - Voyager 1 and 2 Spacecrafts. The Lower Resolution images taken by the two Voyager Spacecrafts also provided the context needed to better interpret the Higher Resolution ones taken by the Galileo Spacecraft during both its "Nominal Mission" and the upcoming "Europa Mission".


North is towards the top of the frame and the Sun illuminates the Frozen Surface of Europa from the right. The mosaic, which is centered at about 40° South Latitude and 180° East Longitude, covers an area approximately 675 by 675 Km (such as about 419,175 by 419,175 miles). The finest details that can be discerned in this picture are about 3,3 Km (2,04 miles) across. The images forming this mosaic were taken on February, 20, 1997 at 12 hours, 55 minutes and 34 seconds Universal Time and when the Spacecraft was at a distance of approx. 81.700 Km (such as about 50.736 miles) from Europa.


This frame (which is an Original NASA - Galileo Spacecraft b/w image published on the NASA - Planetary Photojournal with the ID n. PIA 00875) 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 - Galileo 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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