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.
2024 September 7
Small Moon Deimos
Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: Mars has two tiny moons, Phobos and Deimos, named for the
figures in Greek mythology Fear and Panic. Detailed surface views of
smaller moon Deimos are shown in both these panels. The images were
taken in 2009, by the HiRISE camera on board the Mars Reconnaissance
Orbiter spacecraft, NASA's long-lived interplanetary internet
satellite. The outermost of the two Martian moons, Deimos is one of the
smallest known moons in the Solar System, measuring only about 15
kilometers across. Both Martian moons were discovered in 1877 by Asaph
Hall, an American astronomer working at the US Naval Observatory in
Washington D.C. But their existence was postulated around 1610 by
Johannes Kepler, the astronomer who derived the laws of planetary
motion. In this case, Kepler's prediction was not based on scientific
principles, but his writings and ideas were so influential that the two
Martian moons are discussed in works of fiction such as Jonathan
Swift's Gulliver's Travels, written in 1726, over 150 years before
their discovery.
Tomorrow's picture: large galaxy Andromeda
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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.
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