NASA’s Mariner 9 Mars orbiter becomes the first spacecraft to provide relatively close-up images of Mars’ innermost, larger moon, Phobos, from over 3,500 miles away. The irregular shape and heavily cratered surface of Phobos point up its likely origins as an asteroid that long ago came close enough to Mars to be captured into an orbit. Phobos (and its still unseen-at-close-range smaller sibling, Deimos) will be imaged at much closer range later in the 1970s by the Viking orbiters.
Mariner 9 at Phobos
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