more at http://scitech.quickfound.net/astro/mars_news.html As the Mars Curiosity rover looks skyward, Phobos passes in front of Deimos. "This video depicts NASA's Curiosity rover observing Mars' two moons, then shows one moon passing in front of the other." Public domain film from NASA - Jet Propulsion Laboratory. The film was silent. I have added music created by myself using the Reaper Digital Audio Workstation and the Independence and Proteus VX VST instrument plugins. http://en.wikipedia.org/wiki/Phobos_(moon) Phobos (/ˈfoʊbəs/ FOH-bəs; Greek: Φόβος; systematic designation: Mars I) is the larger and closer of the two natural satellites of Mars. With a mean radius of 11.1 km (6.9 mi), Phobos is 7.24 times more massive than the second moon Deimos. It is named after the Greek god Phobos (which means "fear"), a son of Ares (Mars) and Aphrodite (Venus) . Both moons were discovered in 1877. A small, irregularly shaped object, Phobos orbits about 9,400 km (5,800 mi) from the center of Mars, or about 6,000 km (3,700 mi) from the Martian surface, closer to its primary than any other known planetary moon. Phobos is one of the least reflective bodies in the Solar System, and features a large impact crater, Stickney. It orbits so close to the planet that it moves around Mars faster than Mars rotates. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 h 15 min or less, and set in the east twice each Martian day. Due to its short orbital period and tidal interactions, Phobos's orbital radius is decreasing and it will eventually break up into a planetary ring... Discovery Phobos was discovered by astronomer Asaph Hall on 18 August 1877, at the United States Naval Observatory in Washington, D.C., at about 09:14 Greenwich Mean Time (contemporary sources, using the pre-1925 astronomical convention that began the day at noon, give the time of discovery as 17 August at 16:06 Washington mean time). Hall also discovered Deimos, Mars's other moon, on 12 August 1877 at about 07:48 UTC. The names, originally spelled Phobus and Deimus respectively, were suggested by Henry Madan (1838--1901), Science Master of Eton, based on Book XV of the Iliad, in which the god Ares summons Dread (Deimos) and Fear (Phobos). Physical characteristics Phobos has dimensions of 27 × 22 × 18 km, and is too small to be rounded under its own gravity. Its surface area is slightly less than the land area of Delaware. It is one of the least reflective bodies in the Solar System. Spectroscopically it appears to be similar to the D-type asteroids, and is apparently of composition similar to carbonaceous chondrite material. Phobos's density is too low to be solid rock, and it is known to have significant porosity. These results led to the suggestion that Phobos might contain a substantial reservoir of ice. Spectral observations indicate that the surface regolith layer lacks hydration, but ice below the regolith is not ruled out. Faint dust rings produced by Phobos and Deimos have long been predicted but attempts to observe these rings have, to date, failed. Recent images from Mars Global Surveyor indicate that Phobos is covered with a layer of fine-grained regolith at least 100 meters thick; it is hypothesized to have been created by impacts from other bodies, but it is not known how the material stuck to an object with almost no gravity. Phobos is heavily cratered, with one of the craters near the equator having a central peak despite the moon's small size. The most prominent surface feature is the crater Stickney, named after Asaph Hall's wife, Angeline Stickney Hall... http://en.wikipedia.org/wiki/Deimos_(moon) Deimos is a natural satellite of the planet Mars with an average radius of 6.2 km (3.9 mi), and an escape velocity of 5.6 m (18 ft)/s (20 km (12 mi)/h). It is the smaller and outer of Mars's two known moons, the other being Phobos. 23,460 km (14,580 mi) distant from Mars, Deimos takes 30.3 hours to orbit the planet at an orbital velocity of 1.35 km (0.84 mi)/s. Its systematic designation is Mars II. In English Deimos is pronounced /ˈdaɪməs/ DY-məs; also /ˈdiːməs/ DEE-məs; Greek: Δείμος; also DAY-moce or DEE-moce. In Greek mythology, Deimos was the twin brother of Phobos and personified Terror...

• published: 22 Aug 2013
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