Deimos, a tiny Martian moon

Credit: NASA/JPL/University of Arizona

NASA recently published spectacular images of Deimos, the smaller of the two tiny Martian moons. The enhanced-color images were acquired by the high-resolution camera (HiRISE), aboard NASA's Mars Reconnaissance Orbiter (MRO), on 21 February 2009.

Potato-shaped Deimos has a smooth surface, due to a soil of rock debris or regolith, except for the most recent impact craters. It is a dark, reddish object, very similar to Phobos, the larger Martian moon. Detailed information on Phobos can be found through the links below.

The surface of Deimos shows color variations. These subtle hues are probably due to the exposure of surface materials to the space environment, which leads to darkening and reddening.

Deimos is about 12 km across, while our Moon is 3,476 km across! It is believed to be composed of rock rich in carbon, similar to some asteroids and meteorites. The mean density of Deimos is low. Deimos orbits very close to its parent planet, at an average distance of approximately 23,400 km, but the small satellite shines merely as a bright star-like object in the Martian skies. Deimos orbits Mars every 30 hours, and like our Moon, it keeps the same side turned to its planet.

Intriguingly, Deimos frequently passes in front of the Sun, as viewed from Mars, but it does not produce total solar eclipses, due to its small size. During these Martian solar eclipses, Deimos is visible as a black dot crossing the Sun. Therefore, this effect is rather termed “transit”. On 4 March 2004, a transit of Deimos was photographed by Mars Rover Opportunity, while on 13 March 2004, a transit was photographed by Mars Rover Spirit.

 Further Reading

Solar System Exploration

http://solarsystem.nasa.gov/index.cfm

Deimos

http://www.nineplanets.org/deimos.html

Phobos

http://www.nineplanets.org/phobos.html

Mars Exploration Rovers

http://marsrovers.jpl.nasa.gov/home/index.html

Aymen Mohamed Ibrahem

Senior Astronomy Specialist