Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2012 March 27 Unusual Hollows Discovered on Planet Mercury Image Credit: NASA/JHU APL/CIW Explanation: What are those unusual features on planet Mercury? The slightly bluish tinge of features dubbed hollows has been exaggerated on the above image by the robotic MESSENGER spacecraft currently [ame="http://www.youtube.com/watch?v=UVVerBya6l4"]orbiting Mercury[/ame]. The rounded depressions appear different than impact craters and nothing like them has been noted on Earth's Moon or anywhere else in the Solar System. The above image is a section of the floor of Raditladi impact basin about 40 kilometers wide that includes the mountains of the central peak. One progenitor hypothesis is that the hollows formed from the sublimation of material exposed and heated during the violent impact that created the Raditladi basin. NASA's MESSENGER is the first spacecraft ever to orbit Mercury, and is currently scheduled to explore the Solar System's innermost planet into 2013. Tomorrow's picture: venusshine A pure guess, but on first look I wonder if these are collapsed hollow bubbles of rock, and when they're opened it shows a different rock type/element beneath? Some look like they were once shared an underground flow. MelT
Gotta be something to do with the extreme contrast of temps mercury experiences....that's my guess. Mercury gets pulled about all over the show, it'd be interesting to see if Io displays any of the same features.