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Phobos (moon)

natural satellite of Mars

Phobos (or Mars I) is one of Mars' moons. The other is Deimos.

Phobos
Phobos colour 2008.jpg
Enhanced-color view of Phobos obtained by Mars Reconnaissance Orbiter on March 23 2008.
Discovery
Discovered byAsaph Hall
Discovery dateAugust 18, 1877
Orbital characteristics
Epoch J2000
Periapsis9235.6 km
Apoapsis9518.8 km
9377.2 km[1]
Eccentricity0.0151
0.31891023 d
(7 h 39.2 min)
2.138 km/s
Inclination1.093° (to Mars's equator)
0.046° (to local Laplace plane)
26.04° (to the ecliptic)
Satellite ofMars
Physical characteristics
Dimensions26.8 × 22.4 × 18.4 km[2]
Mean radius
11.1 km[3]
(0.0021 Earths)
~6100 km²
(11.9 µEarths)
Volume5680 km³[4]
(5.0 nEarths)
Mass1.072×1016 kg[5]
(1.8 nEarths)
Mean density
1.887 g/cm³[4]
0.0084–0.0019 m/s²
(8.4-1.9 mm/s²)
(860-190 µg)
11.3 m/s (40 km/h)[5]
synchronous
Equatorial rotation velocity
11.0 km/h (at longest axis' tips)
Albedo0.071[3]
Temperature~233 K
11.3[6]
Orbits of Phobos and Deimos (to scale), as seen from above Mars

Phobos is the larger of the two moons, and is only 27 kilometers in diameter. This is about as far as a car can travel on the highway in 15 minutes. It is covered with craters, as Earth's moon is.[7]

It is named after the god Phobos in Greek mythology. Its name means "fear".

Phobos is trapped in tidal drag, with its orbit lowering roughly 1.8 meters per century. In about 50 million years, Phobos will reach the Roche limit, where it is likely to be torn apart. Some fragments will fall on Mars and some will form a planetary ring or rings around Mars.

The other moon, Deimos, is the smaller of the two.

SpacecraftEdit

The Soviet Union sent at least two space craft to this moon, Phobos 1 and Phobos 2. Both failed or lost contact with Earth, but Phobos 2 managed to take some pictures of the moon in 1989 before dying.

FeaturesEdit

There is one large crater on Phobos called Stickney. It is   the size of the moon itself.

ReferencesEdit

  1. NASA Celestia
  2. "Mars: Moons: Phobos". NASA Solar System Exploration. 2003-09-30. Retrieved 2008-08-18.
  3. 3.0 3.1 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2006-07-13. Retrieved 2008-01-29.
  4. 4.0 4.1 "Mars Express closes in on the origin of Mars' larger moon". DLR. 2008-10-16. Retrieved 2008-10-16.
  5. 5.0 5.1 use a spherical radius of 11.1 km; volume of a sphere * density of 1.877 g/cm³ yields a mass (m=d*v) of 1.07×1016 kg and an escape velocity (sqrt((2*g*m)/r)) of 11.3 m/s (40 km/h)
  6. "Classic Satellites of the Solar System". Observatorio ARVAL. Retrieved 2007-09-28.
  7. Gater, Will (2009). Space 3D. Bristol Magazines. p. 67.