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Mars Moons
The Phobos and Deimos are
the two moons of Mars and their orbits are
seen from above Mars' North Pole. Both Phobos
and Deimos are tidally locked with Mars,
always pointing the same face towards it.
Since Phobos orbits around Mars faster than
the planet itself rotates, tidal forces
are slowly but steadily decreasing its orbital
radius. At some point in the future Phobos
will be broken up by gravitational forces.
Deimos, on the other hand, is distant enough
that its orbit is being gradually boosted
instead. |
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Both satellites were discovered
in 1877 by Asaph Hall, and are named after the
characters Phobos (panic/fear) and Deimos (terror/dread)
who, in Greek mythology, accompanied their father
the Greek god Ares into battle. Ares was known
to the Romans as Mars, the god of war.
Mars' Natural Satellites:
| Name |
Diameter
(km) |
Mass
(kg) |
Mean
orbital radius (km) |
Orbital
period (h) |
| Phobos |
22.2 |
(27 × 21.6 ×
18.8) |
1.08×1016 |
9378 7.66 |
| Deimos |
12.6 |
(10 × 12 ×
16) |
2×1015 |
23,40030.35 |
As seen from Mars, Phobos has
an angular diameter of between 8' (rising) and
12' (overhead), while Deimos has an angular diameter
of about 2'. The Sun's angular diameter, by contrast,
is about 21'.
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