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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.

A cratered object is shown that shows on really large crater on its right side. Please see the explanation for more detailed information.

Mimas: Small Moon with a Big Crater

Explanation: Whatever hit Mimas nearly destroyed it. What remains is one of the largest impact craters on one of Saturn 's smallest round moons. Analysis indicates that a slightly larger impact would have destroyed Mimas entirely. The huge crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel , spans about 130 kilometers and is featured here . Mimas ' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described as a big dirty snowball. The featured image was taken during the closest-ever flyby of the robot spacecraft Cassini past Mimas in 2010 while in orbit around Saturn .

Interactive: Take a trek across Mimas
January 14: Zoom APOD Lecture hosted by the Amateur Astronomers of Association of New York

Date January 12, 2025
Credit Image Credit: NASA , JPL-Caltech , Space Science Institute , Cassini
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.