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.

September 6, 1996
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The Largest Impact Crater
Credit: The Clementine Project

Explanation: What is the largest known impact crater in the Solar System? Over 1300 miles across, the South Pole-Aitken Basin on the farside of Earth's Moon holds that distinction. Circled above in a false color mosaic of Clementine images it was caused when an asteroid or comet sized object crashed into the surface, penetrating the lunar mantle. In general, the rocky terrestrial planets and moons are scarred and battered from frequent repeated bombardment by large objects during our Solar System's early years. On Earth, continuous geological activity has hidden much of the damage, but the surface of the smaller, less active Moon bears testimony to a shared history of fierce and frequent impacts. At the present time in the vicinity of Earth, the bombardment continues - fortunately at a greatly reduced rate.

Tomorrow's picture: Two Billion Years After the Big Bang

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA).
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
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