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Definition: Deimos from The Columbia Encyclopedia

(dī'mŏs), in astronomy, one of the two moons, or natural satellites, of Mars.

Summary Article: Deimos
from Collins Dictionary of Astronomy

A satellite of Mars, lying farther from the planet than the slightly larger satellite Phobos. Like Phobos, it was discovered in 1877 by the US astronomer Asaph Hall. Deimos is an irregular body measuring 15 × 12 × 11 km, and orbits above Mars' equator at a distance of 23 460 km from the center of the planet in a period of 1.26 days. It orbits with its long axis radially aligned with the planet. Like Phobos, it may be a captured asteroid of a type similar to the carbonaceous chondrite meteorites. However, it appears to have none of the grooves and crater chains found on Phobos and many of its craters are less distinct, probably because of infilling by crater ejecta that may lie tens of meters thick on the surface. The larger craters, such as Voltaire and Swift, measure only about 1.3 km across. See Table 2, backmatter.

© Market House Books Ltd, 2006

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