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The Details of a Ray

What could have caused this small, bright swarm of impact craters? The fact that they are fairly similar in size and clustered together suggests that they are secondary craters, which form when material from a larger primary crater is ejected and impacts the surrounding terrain. The high albedo and sharp rims and walls of these small craters also suggest they formed relatively recently, though no large fresh craters are seen in the immediate surroundings. Instead, they appear to originate from Fonteyn crater, just over 1,000 km (622 mi.) to the east. This small, bright patch is a segment of one of Fonteyn's beautiful rays, and shows just how important a process secondary cratering is on Mercury, such that even craters around 29 km (18 mi.) in diameter can affect the surface great distances away.

Date acquired: August 30, 2012

Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington