[ut.stardate] StarDate: August 11: The Discovery of Phobos and Deimos

dipper@utastro.UUCP (Debbie Byrd) (08/18/84)

The moons of Mars were discovered just 107 years ago.  More on Phobos
and Deimos -- right after this.

August 11:  The Discovery of Phobos and Deimos

During this night 107 years ago, an astronomer named Asaph Hall made a
remarkable discovery.  He discovered the first of two moons for the
planet Mars.

Hall had searched with a telescope for many weeks -- and almost had
given up.  His wife, Chloe Angeline Stickney Hall, urged him to keep
trying -- and on the night of August 11, 1877 -- Hall saw a glimmer of
light from a previously unseen source.  Unfortunately, just at that
moment, a dense fog rolled in -- and Hall was forced to stop working.

The sky didn't clear again for five long days.  But when it did, Hall
turned the telescope on Mars and quickly found the point of light.
Within two hours, he had established that it moved in the sky with the
planet and thus was not a fixed star.  It was really a Martian moon --
the first ever to be discovered.

Soon afterwards, Hall noticed a second moon.  He later named the two
moons Phobos and Deimos -- Fear and Panic -- for the horses of the war
god Mars in Homer's Illiad.  These moons are among the smallest worlds
in the solar system -- they're only about five and ten miles across --
and may actually be asteroids captured into orbit by the gravity of
Mars.

By the way, many years later, when spacecraft visited the planet Mars,
they photographed a large crater on the moon Phobos -- which was
subsequently named Stickney for Chloe Angeline Stickney Hall -- who
encouraged her husband to search "just one more night" for the moons of
Mars.




Script by Deborah Byrd.



(c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin