Phobos

Int

Phobos is the larger and closer of the two moons of Mars, the other being Deimos. Both moons were discovered in 1877. With a mean radius of 11.1 km, Phobos is 7.24 times as massive as Deimos. It is named after the Greek god Phobos (which means "fear"), a son of Ares (Mars).

Astronomical specifications:

Discovery	18 Aug 1877 by Asaph Hall
Orbital characteristics:
Distance from Mars	9366 km
Periapsis	9,235.6 km
Apoapsis	9,518.8 km
Eccentricity	0.0151
Orbital periode rond Mars	0.318 days
Orbital speed	km/s
Inclination to Mars equator	1.093 deg
Rings	No
Physical characteristics:
Radius	11.1 km
Surface area	6100 km²
Volume	5680 km³
Mass	1.072 x 10¹⁶ kg
Density	1.876 g/cm³
Equatorial gravity	0.0084-0.0019 m/s²
Escape velocity	11.3 m/s
Rotation period	days
Axial tilt	0 deg
Surface temperature	~233 K
Atmospheric composition

Enhanced-color view of Phobos obtained by "Mars Reconnaissance Orbiter" on March 23, 2008

Exploration missions:

"Viking 1" image of Phobos, with "Stickney Crater" to the right.

The Phobos monolith (right of center) as taken by the Mars Global Surveyor in 1998.

Phobos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars. The first was Mariner 9 in 1971, followed by Viking 1 in 1977, Mars Global Surveyor in 1998 and 2003, Mars Express in 2004, 2008, and 2010, and Mars Reconnaissance Orbiter in 2007 and 2008. In summer 2005, the Spirit Rover, with an excess of energy due to wind blowing dust off of its solar panels, took several short-exposure photographs of the night sky from the surface of Mars. Phobos and Deimos are both clearly visible in the photograph. The only dedicated Phobos probes have been the Soviet Phobos 1 and Phobos 2, both launched in July 1988. The first was lost en route to Mars, while the second returned unusual data and images but failed shortly before beginning its detailed examination of the moon's surface.

Phobos missions:

Name	Launch Date	Launch rocket	Weight (kg)	Mission
Mariner 9 (USA)	30-May-71	Atlas/Centaur	975 kg	The Mariner 9 mission resulted in a global mapping of the surface of Mars, including the first detailed views of the martian volcanoes, Valles Marineris, the polar caps, and the satellites Phobos and Deimos.
Viking 1 (USA)	20-Aug-75	Titan-3E	2325 kg	The Orbiter flew 88 km by Phobos on 1977 Feb 20.
Phobos 1 (USSR)	07-Jul-88	Proton-K	-	Mars orbiter, lost en route to Mars.
Phobos 2 (USSR)	12-Jul-88	Proton-K	6.220 kg	Mars orbiter, contact lost before planned fly-by of the moon Phobos.
Mars Express (ESA)	02-Jun-03	Soyuz-FG/Fregat	982 kg	Mars Express orbiter has been making close flybys of the small Martian moon Phobos, with a record close approach of 67 km on March 3, 2010 beating the previous 89 km record set by Viking Orbiter 1 on Feb 20, 1977.
Fobos-Grunt (Russia)	08-Nov-11	Zenit-2FG	- kg	Phobos lander. After launch, Fobos-Grunt failed to ignite the propulsion module, went into safe-mode and remained in low earth orbit.

Ref.: #6m, #98 - update: 12.08.11

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