NASA Astronomy Picture of the Day Collection

Saturn's Moon Rhea from Cassini

Each moon of Saturn seems to come with its own mystery [ http://antwrp.gsfc.…]. Rhea, Saturn's second largest moon behind Titan [ http://antwrp.gsfc.…], shows unusual wisps, visible above as light colored streaks. Higher resolution images of similar wisps on Dione indicate that they might be made of long braided fractures. Rhea [ http://www.nineplan…] is composed mostly of water ice [ http://www.mtu.edu/…], but likely has a small rocky core [ http://adsabs.harva…]. Rhea's rotation and orbit are locked together, just like Earth's Moon [ http://antwrp.gsfc.…], so that one side always faces Saturn [ http://en.wikipedia. org/wiki/Saturn_(pla net) ]. A consequence of this is that one side always leads the other. Rhea [ http://antwrp.gsfc.…]'s leading surface is much more heavily cratered [ http://antwrp.gsfc.…] than the trailing surface, pictured above. The above image [ http://photojournal…] in natural color was taken last month by the Cassini robot spacecraft [ http://saturn.jpl.n…] in orbit around Saturn.

Cassini Imaging Team [ http://ciclops.lpl.…], SSI [ http://www.spacesci…], JPL [ http://www.jpl.nasa…], ESA [ http://www.esa.int/], NASA [ http://www.nasa.gov/]

Arizona

Saturn

Dione

Rhea

Goddard Space Flight Center (GSFC)

Jet Propulsion Laboratory (JPL)

Earth

Moon

Saturn

Cassini

Titan

Dione

Rhea

moon

http://antwrp.gsfc.…

SPD-APOD-ap050215