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APOD

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.

Mercury's Caloris Basin

Explanation: Mercury , the closest planet to the Sun , has a surface with so many craters it resembles the Earth 's Moon . The largest surface feature on Mercury is the Caloris Basin, which resulted from a collision with an asteroid . The basin, which is more that 1000 kilometers across, is visible as the large circular feature at the bottom of the above photograph. Similar features, such as the Mare Orientale , are seen on the Moon. The Caloris Basin gets very hot because it is near the “sub-solar point” - the point on Mercury 's surface that is directly under the Sun when Mercury is closest to the Sun .

Date January 20, 1996
Credit Credit: NASA, JPL, Mariner 10
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.