Deimos (moon)

Asaph Hall

Deimos (from the Greek Δείμος " terror " spoken [ dɛɪmɔs ], also Germanized [ daɪmɔs ] ), also known as the Mars II is next to Phobos one of the two natural satellites of Mars. It is named after Deimos, son and companion of the Greek war god Ares (Latin Mars).

It was in the year 1877 together with Phobos by U.S. astronomer Asaph Hall at the U.S. Naval Observatory in Washington, DC discovered.

Orbit

Deimos is the more distant of the two moons of Mars, it runs on an almost exact circular orbit of radius 23,459 km (equivalent to 20,063 kilometers above the Martian equator) and needed for a Mars round 1 days, 6 hours and 18 minutes. As the Earth's moon Deimos has a synchronous rotation, that is, he turns the Mars always the same side to. Its orbit is slightly inclined 1.79 ° relative to the equatorial plane of Mars.

If you were standing on Mars would seem a Deimos with an apparent diameter of twice the size, which has the Venus from Earth at its closest approach. He would still be seen only as a blurred spot on Mars firmament, he is also one of the darkest celestial bodies in the solar system. Deimos is seen 2.5 sol on Mars due to its orbital speed.

Properties

Deimos is the smaller of the two moons of Mars. It measures 15 × 12.2 × 10.4 km and has an average density of 1.7 g / cm ³. Because of its irregular shape is generally assumed that Deimos is just like a captured Phobos from Mars Asteroid.

The surface of this moon is like the one covered by Phobos with a dust layer, the so-called regolith. This substance is known from the Earth's moon. The Regolithschicht on Deimos is thicker than on Phobos, which has the consequence that the surface features are less pronounced on him. Deimos also has a very low albedo of only 0.07.

Ground-based observations

Due to its close proximity to Mars Deimos in the telescope is difficult to detect because it is heavily outshined by Mars. Its angular separation is during an average opposition of Mars only a maximum of 53 seconds of arc of the planet's surface, but the planet is about 14 magnitudes or more than 400,000 times brighter than the moon.

Cultural History

The existence of two small moons of Mars was already anticipated in 1727 fictitiously of Jonathan Swift, in the third part of Gulliver's Travels - Lemuel Gulliver - long before their discovery by Asaph Hall. The book tells astronomers know the laputanischen " two smaller stars, or satellites, which run around Mars; this is the innermost from the center of the planet exactly three of its diameters away the outermost five; former completes its orbit in the period of ten, the latter in twenty-one and a half hours. "

This story ran in 1750 in Voltaire's novel Micromégas in which a giant from the star Sirius visited our solar system.

In honor of these authors, two of the craters on Deimos the names of Swift and Voltaire.

Remarkably, this anticipation is not only because of the similarity in terms of distance and orbital period, but also because all other hitherto known moons ( Earth's Moon, Galilean moons of Jupiter and Saturn 's moon Titan ) have much longer orbital periods and thus difficult to be used as template in question.

The American electronic musician Larry Fast dedicated to both the Martian moons Phobos and Deimos in 1978 appeared on his album Cords composition Phobos And Deimos Go To Mars.

Deimos and Phobos are scenes of the famous computer game Doom in 1993.

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