Phobos (moon)

Phobos (IPA {{IPA|/?fo?b?s/}}, Greek Φόβος: "Fright"), is the larger and innermost of Mars' two moons, and is named after Phobos, son of Ares (Mars) from Greek Mythology. Phobos orbits closer to a major planet than any other moon in the solar system, less than 6000 km above the surface of Mars, and is also one of the smallest known moons in the solar system. Its systematic designation is Mars I. The adjectival form of the name is Phobian, and in fairly common usage.

"Hollow Phobos" claims

Around 1958, the distinguished Russian astrophysicist Iosif Samuilovich Shklovsky, studying the secular acceleration of Phobos' orbital motion, suggested a "thin sheet metal" structure for Phobos, a suggestion which led to speculations on Phobos' artificial origin. Shklovsky based his analysis on estimates of the upper martian atmosphere's density, and deduced that for the weak braking effect to be able to account for the secular acceleration, Phobos had to be very light —one calculation yielded a hollow iron sphere 16 km across but less than 6 cm thick.

Related Topics:
1958 - Iosif Samuilovich Shklovsky - Secular

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Competing explanations were based on the land tides Phobos could raise on Mars. The reality of the secular acceleration itself (corresponding to an altitude loss of about 5×10-12 per revolution, about 5 cm per year) was later subjected to doubt, and the problem vanished on its own by 1969. In a February 1960 letter to the journal Astronautics, however, Siegfried Frederick Singer, then science advisor to President Eisenhower, came out in support of Shklovsky's theory, going as far as stating that " purpose would probably be to sweep up radiation in Mars' atmosphere, so that Martians could safely operate around their planet". A few years later, in 1963, Raymond H. Wilson Jr., Chief of Applied Mathematics at NASA, allegedly announced to the Institute of Aerospace Sciences that "Phobos might be a colossal base orbiting Mars", and that NASA itself was considering the possibility.

Related Topics:
Land tide - 1969 - Siegfried Frederick Singer - President Eisenhower - 1963 - Raymond H. Wilson Jr. - NASA - Institute of Aerospace Sciences

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Similar "hollow Moon" claims occurred at around the same time.

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