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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.

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

Olympus Mons on Mars: The Largest Volcano

Explanation: The largest volcano in the Solar System is on Mars. Olympus Mons rises 24 kilometers high and measures 550 km across. By comparison, Earth' s largest volcano, Mauna Loa in Hawaii , rises 9 km high and measures 120 km across. Such large volcanoes can exist on Mars because of the low gravity and lack of surface tectonic motion. Olympus Mons is a shield volcano , built by fluid lava. Over the next three years, Mars Global Surveyor , which arrived at Mars last week, will photograph the planet at such high resolution that objects only 100 meters across will be visible. The above image was taken by Mariner 9 , which orbited and photographed Mars during 1971 and 1972.

Date September 15, 1997
Credit Credit: Mariner 9, JPL, NASA
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.