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Stickney

Crater on Phobos

Mars' larger moon Phobos has an elongated ellipsoid shape, some 27km along its longest axis. Though the moon has a number of significant craters for its size, these are all dwarfed by Stickney, a gigantic impact crater at one end of Phobos' elongated form. Stickney is nine kilometres from edge to edge, a diameter that represents a third the length of the moon itself.

Stickney is marked by a series of striations running into the crater, and also outward from its rim along the surface of the moon. There are various possible explanations for these markings, but they appear to be due to deformations of Phobos as it orbits Mars, and by falls of material from within the crater's walls. Since the formation of Stickney, Phobos has been hit by another strong impact in the same area, resulting in a second smaller crater, the 2km-wide Limtoc, within the bounds of Stickney itself.

Phobos was discovered in 1877 by the astronomer Asaph Hall, encouraged in his work by his wife Chloe Angeline Stickney Hall. When this giant crater was discovered on Phobos nearly a century later, it was given the name of Hall's wife in recognition of the part she played in the finding of the moon that it so prominently marks.

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