صورة اليوم الفلکیة
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.