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Explanation: Why is this small object orbiting Mars? The origin of Phobos, the larger of the two moons orbiting Mars, remains unknown. Phobos and Deimos appear very similar to C-type asteroids, yet gravitationally capturing such asteroids, circularizing their orbits, and dragging them into Mars' equatorial plane seems unlikely. Pictured above is Phobos as it appeared during last week's flyby of ESA's Mars Express, a robotic spacecraft that began orbiting Mars in 2003. Visible in great detail is Phobos' irregular shape, strangely dark terrain, numerous unusual grooves, and a spectacular chain of craters crossing the image center. Phobos spans only about 25 kilometers in length and does not having enough gravity to compress it into a ball. Phobos orbits so close to Mars that sometime in the next 20 million years, tidal deceleration will break up the rubble moon into a ring whose pieces will slowly spiral down and crash onto the red planet. The Russian mission Phobos-Grunt is scheduled to launch and land on Phobos next year.
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: Phobos - Mars
Publications with words: Phobos - Mars
See also:
- APOD: 2024 December 3 Á Ice Clouds over a Red Planet
- APOD: 2024 November 10 Á Valles Marineris: The Grand Canyon of Mars
- APOD: 2024 September 9 Á Mars: Moon, Craters, and Volcanos
- APOD: 2024 June 5 Á Shadow of a Martian Robot
- Ares 3 Landing Site: The Martian Revisited
- Phobos: Moon over Mars
- APOD: 2024 February 26 Á Martian Moon Eclipses Martian Moon