Phobos from Mariner 9
Phobos from Mariner 9 Mariner 9 captured this view of Phobos on December 1, 1971. Stickney crater takes a bite out of the upper left edge of the disk; the large Hall crater, right of center, is close to Phobos' south pole. The side of Phobos that always faces Mars is the upper hemisphere; the lower hemisphere always faces away from Mars. Phobos is 26.00 km x 22.78 km x 18.14 kilometers in size. NASA / JPL / Emily Lakdawalla

The image has had blemishes removed, then was enlarged by a factor of 3, and sharpened.

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