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.

December 15, 1998
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Plains and Ridges on Europa
Credit: Galileo Project, JPL, NASA

Explanation: The ridges on Europa may be caused by cold water volcanoes. Europa, one of the largest moons of Jupiter, has been the source of intense scrutiny since speculation increased of there being oceans beneath its icy surface. Currently the Galileo spacecraft orbiting Jupiter is on an extended mission designed, in part, to study Europa's surface in greater detail. The above image highlights features common to Europa's surface: pure blue water ice beneath lighter ridges that run for many kilometers. These ridges may result from volcanic cracks in the ice where emerging liquid water froze upon exposure to the cold of deep space. The reasons for the colors of the ridges remain uncertain.

Tomorrow's picture: 3-D Mars

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U.