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ORBONIX · MARS SYSTEM
PHOBOS
The larger and closer of Mars's two
small natural satellites.
PHOBOS · MARS'S INNER MOON
9,378 km
AVERAGE DISTANCE FROM MARS
22.4 km
AVERAGE DIAMETER
7 h 39 min
ORBITAL PERIOD
~27 × 22 × 18 km
APPROX. DIMENSIONS
~1.9 × 10¹⁶ kg
ESTIMATED MASS
IRREGULAR
SHAPE
MARS'S INNER MOON
Phobos is the larger and closer of the
two natural satellites of Mars.
It is an irregular, heavily cratered body
with a surface dominated by impact debris
and grooves.
Phobos orbits Mars extremely quickly.
It completes one orbit in only about
7 hours and 39 minutes, meaning that it
travels around Mars faster than Mars
rotates.
From the surface of Mars, Phobos would
appear to rise in the west and set in
the east.
Scientists believe Phobos may be a
captured asteroid or could have formed
from material ejected by a massive impact
on Mars.
RAPID ORBIT
Phobos completes an orbit around Mars
in less than 8 hours.
STICKNEY CRATER
The enormous Stickney crater is the
largest impact feature on Phobos.
DOOMED MOON
Phobos is slowly spiraling toward Mars
and is expected to eventually break apart
or impact the planet.
DID YOU KNOW?
Phobos orbits Mars so quickly that it can
rise and set more than once in a single Martian day.
IMAGE:
NASA / JPL-CALTECH / UNIVERSITY OF ARIZONA /
WIKIMEDIA COMMONS