Astronomy Picture of the Day
Discover the cosmos! Each day we feature a different image or photograph
of our fascinating universe, along with a brief explanation written by a
October 3, 1995
Deimos: A Small Martian Moon
Mars has two tiny moons,
Phobos and Deimos. Pictured above is
Deimos, the smallest moon of
Deimos is the
smallest known moon in the Solar System
measuring only 9 miles across.
The diminutive Martian moons were
discovered in 1877 by Asaph Hall,
an American astronomer working at the
US Naval Observatory
in Washington D.C.
The existence of two Martian moons was predicted around 1610 by
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 actual discovery.
Tomorrow's picture: The Sun Spews X-rays
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