Explanation:
Hurtling through space above the Red Planet,
potato-shaped Phobos completes an orbit of Mars
in less than eight hours.
In fact, since its orbital period is shorter than
the planet's rotation period,
Mars-based
observers
see Phobos rise in the west and set in the east -
traveling
from horizon to horizon in about 5 1/2 hours.
These three images from the Mars Global Surveyor (MGS)
spacecraft
record the oval
shadow of Phobos racing over
western Xanthe Terra on August 26, 1999.
The area imaged is about 250 kilometers across and is seen
in panels from left to right as
red filter, blue filter, and combined color composite views
from the MGS wide-angle camera system.
The three dark spots most easily seen in the
red filter image are likely small fields of dark
sand dunes on crater floors.
Standing
in the shadow of Phobos, you would see the
Martian version of a solar eclipse!
