Phobos


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Related to Phobos: Deimos

Phobos

(fō`bŏs), in astronomy, innermost moon, or natural satellite, of MarsMars,
in astronomy, 4th planet from the sun, with an orbit next in order beyond that of the earth. Physical Characteristics

Mars has a striking red appearance, and in its most favorable position for viewing, when it is opposite the sun, it is twice as bright as
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.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

Phobos

(foh -bos) The innermost and larger of the two satellites of Mars, both of which were discovered in 1877 by Asaph Hall. Observations from Mars-orbiting spacecraft show it to be an irregular potato-shaped body, measuring 27 × 22 × 19 km with a mass of 1016 kg and a density twice that of water. It orbits above the equator of Mars at a distance of 9380 km from the center of the planet every 7.65 hours, keeping its long axis pointing toward Mars. The low density, together with a low albedo of 0.06, suggest that it resembles the water-rich carbonaceous chondrite meteorites, although it is difficult to see how such an object could have formed at the distance of Mars from the Sun. Possibly Phobos and Deimos, Mars' other small satellite, formed as more distant asteroids and were later captured by Mars in some way. The orbit of Phobos is decaying (contracting) because of tidal drag and the satellite may fall from orbit within another 100 million years.

Phobos has a regolith-covered cratered surface with the two largest craters, Stickney and Hall, having diameters of 10 and 6 km. A network of pitted grooves, typically 100–200 meters wide and 20–30 meters deep, radiate around the satellite from Stickney and are thought to have arisen from severe internal fracturing and heating caused by the impact event that formed the crater. Chains of small craters parallel to the orbit of Phobos possibly represent the secondary impacts of clumps of material swept up from orbit around Mars after being ejected from the satellite during earlier primary impacts. See Table 2, backmatter.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Phobos

 

the innermost satellite of the planet Mars, located at a mean distance of 9,380 km from the planet. According to photographs obtained by the space probe Mariner 9 in 1971–72, Phobos is an irregularly shaped body pitted with numerous craters. It measures 26 km in length and 21 km in width. Its period of revolution around Mars is 7 hr 39 min, that is, less than the period of rotation of Mars about its axis. The albedo of Phobos’ surface is close to the albedo of the darkest areas of the moon (about 5 percent). Phobos was discovered by A. Hall in 1877.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

Phobos

[′fō‚bȯs]
(astronomy)
A satellite of Mars; it is the larger of the two satellites, with a diameter of about 15 miles (24 kilometers).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The Mars probe imaged Phobos, the larger of the two Mars moons at 16 miles (26 kilometers) across, passing in front of the Sun on March 26, according to (https://www.nasa.gov/feature/jpl/curiosity-captured-two-solar-eclipses-on-mars) NASA's website .
A new study bolsters the idea that strange grooves crisscrossing the surface of the Martian moon Phobos were made by rolling boulders blasted free from an ancient asteroid impact.
In 1971, NASA's Mariner 9 spacecraft revealed both Phobos and Deimos as irregularly shaped, heavily cratered shards of cosmic debris that are among the least reflective objects in the entire solar system.
[USA], Jul 21 ( ANI ): NASA's Hubble Space Telescope has captured Phobos, one of Mars' two moons, during its orbital trek around the Red Planet.
Those moons, long since reclaimed by Mars, could have herded remaining debris in the sparsely populated outer part of the ring to form Phobos and Deimos.
It was a tricky shoot as Phobos and its sister moon, Deimos, are closer to Mars than our Moon is to Earth, so they shoot across the sky relatively quickly.
Last November, Russia launched the Phobos-Grunt spacecraft to explore Phobos, one of Mars's two moons.
Phobos: Mayan Fear provides the fine book in the Mayan Prophecy series, arrives just in time for 2012, and will be enthusiastically greeted by any who enjoyed his prior DOMINION and GOLIATH.
The Phobos-Ground was designed to travel to one of Mars'' twin moons, Phobos, land on it, collect soil samples and fly them back to Earth in 2014 in one of the most daunting interplanetary missions ever.
Roscosmos predicts that only between 20 and 30 fragments of the Phobos probe with a total weight of up to 200 kilograms (440 pounds) will survive the re-entry and plummet to Earth.
It is designed to travel to the Martian moon of Phobos, scoop up soil and return the sample to Earth by 2014.