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.

2000 July 14
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

Crater On Ice
Credit: Galileo Team, JPL, NASA

Explanation: Impact craters are common on Earth's moon but on Jupiter's large ice moon Europa, they are very rare. Over time, both bodies have been subjected to an intense pounding by the solar system's formative debris, but geological activity on Europa's surface seems to have erased most of these impact scars. This false-colour infrared image from the Galileo spacecraft's NIMS instrument shows a newly discovered crater on Europa as a light red ring feature near centre surrounding a dark core. For scale, the dark core is about 29 kilometres in diameter. Only seven comparably large craters have now been identified on Europa's surface. Red colours in the image represent a relatively pure water ice composition while blue colours indicate that other minerals are present. The crater's central dark area may contain the remnants of the impacting body. The icy crust of Europa is of great interest, as evidence mounts that it covers an ocean of liquid water, possibly providing suitable conditions for life.

Tomorrow's picture: Star Trails

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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.