Phobos


Phobos
/foh"beuhs, -bos/, n.
1. Also, Phobus /foh"beuhs/. Class. Myth. a son and attendant of Ares and the personification of a fear held to possess armies and cause their defeat.
2. Astron. one of the two moons of Mars. Cf. Deimos.

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 the inner and larger of Mars's two moons. It was discovered telescopically with its companion moon, Deimos, by the American astronomer Asaph Hall (Hall, Asaph) in 1877 and named for one of the sons of Ares, the Greek counterpart of the Roman god Mars. Phobos is a small, irregular rocky object with a crater-scarred, grooved surface.

      A roughly ellipsoidal body, Phobos measures 26.6 km (16.5 miles) across at its widest point. It revolves once around Mars every 7 hours 39 minutes at an exceptionally close mean distance—9,378 km (5,827 miles)—in a nearly circular orbit that lies only 1° from the planet's equatorial plane. Because the satellite's orbital period is less than the rotational period of Mars (24 hours 37 minutes), Phobos moves from west to east in the Martian sky. The long axis of Phobos constantly points toward Mars; as with Earth's Moon, it has a rotational period equal to its orbital period and so keeps the same face to the planet.

      The heavily cratered surface of Phobos is covered with a very dark gray regolith (unconsolidated rocky debris) that reflects only about 6 percent of the light falling on it—about one-half that of the Moon's surface. This fact and the satellite's low mean density (1.9 grams per cubic cm) are consistent with the composition of carbonaceous chondrite meteorites, suggesting that Phobos may be a captured asteroid-like (asteroid) object. Remarkable linear grooves, typically 100 metres (330 feet) wide and 20 metres (65 feet) deep, cover much of the surface. There is strong evidence that they are associated with the formation of the largest crater on Phobos. This structure, known as Stickney, measures about 10 km (6 miles) across. Precise observations of Phobos's position over the past century suggest that tidal forces from Mars are slowly pulling the satellite toward the planet. If such is the case, it will collide with Mars in the very distant future.

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Universalium. 2010.

Look at other dictionaries:

  • Phobos — Phobos, Greek for fear , is the root word of phobia . It may refer to:*Phobos (mythology), one of the sons of Ares and Aphrodite in Greek mythology *Phobos (moon), the larger and innermost of Mars two moons *Phobos (physics) is a nuclear physics… …   Wikipedia

  • Phobos — (v. altgriech.: φόβος phobos bzw. φοβία phobia = „Furcht“, „Angst“) kann folgende Bedeutungen haben: Phobos (Mythologie), ein Bruder des Deimos in der griechischen Mythologie Phobos (Mond), ein nach vorigem benannter Mond des Mars Fobos (auch… …   Deutsch Wikipedia

  • Phobos — Phobos, s. Deimos und Phobos …   Meyers Großes Konversations-Lexikon

  • Phobos — ☆ Phobos [fō′bəs] n. [Gr phobos, lit., fear, personified as an attendant of Ares: see PHOBE ] the larger of the two satellites of Mars: cf. DEIMOS …   English World dictionary

  • Phobos — Phobos, Personification der Furchterregung, s. u. Ares …   Pierer's Universal-Lexikon

  • Phöbos — (gr., Glänzender), Beiname Apollons …   Pierer's Universal-Lexikon

  • Phöbos — (griech., der »Leuchtende«), Beiname des Apollon (s. d.). Im Französischen (Phébus) übertragen soviel wie Bombast, Schwulst (vgl. Foix 3) …   Meyers Großes Konversations-Lexikon

  • Phobos — (grch., »Schrecken«), ursprünglich selbständiger Gott, nach dem spätern Mythus mit Deimos Sohn und Begleiter des Ares …   Kleines Konversations-Lexikon

  • Phobos — {{Phobos}} ⇒ Deimos …   Who's who in der antiken Mythologie

  • Phobos 1 — Programme Phobos Illustration de la sonde Phobos Le programme Phobos était une mission spatiale inhabitée soviétique, constituée de deux sondes lancées en 1988 et 1989, dédiées principalement à l étude de la planète Mars et de ses deux lunes,… …   Wikipédia en Français

  • Phobos 2 — Programme Phobos Illustration de la sonde Phobos Le programme Phobos était une mission spatiale inhabitée soviétique, constituée de deux sondes lancées en 1988 et 1989, dédiées principalement à l étude de la planète Mars et de ses deux lunes,… …   Wikipédia en Français


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