Moons of Mars attention when Houston's claim was repeated in earnest by a Soviet scientist, Iosif Shklovsky, who, based on a later-disproven density estimate, suggested Phobos was a hollow metal shell. Searches have been conducted for additional satellites. In 2003, Scott S. Sheppard and David C. Jewitt surveyed nearly the entire Hill sphere of Mars for irregular satellites. However scattered light from Mars prevented them from searching the inner few arcminutes where the satellites Phobos and Deimos reside. No new satellites were found to an apparent limiting red magnitude of 23.5, which corresponds to radii of about 0.09 km using an albedo of
Kaidun meteorite several have not been found elsewhere in nature, such as florenskyite, which has the chemical formula: FeTiP. In March 2004 it was suggested that the meteorite originated from the Martian moon Phobos. The reason Phobos has been suggested is the existence of two extremely rare alkaline-rich clasts visible in the meteorite, each of which entered the rock at different times. This suggests that the parent body would have been near a source of an alkaline-rich rock, which is in particular a product of deep differentiation. This points to Mars and one of its moons, and Phobos is more likely than