This double ring basin (top center of image) was photographed during NASA's Mariner 10's second encounter and shows two craters about 30 km in diameter which have been engulfed by smooth plains on the floor of the inner ring.

This double ring basin (top center of image), 220 km in diameter centered at 18 degrees S, 52 degrees W, was photographed on the second encounter and shows two craters about 30 km in diameter which have been engulfed by smooth plains on the floor of the inner ring. This stratigraphic relationship is common in the lunar maria and suggests that the plains within the inner ring were emplaced by volcanic processes after basin formation (FDS 166649).

The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

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