Ray from Gratteri Crater
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Ray from Gratteri Crater

February 28, 2011
Gratteri Crater, located about 150 kilometers to the southeast, ejected rocks that created millions of secondary craters over a region at least 500 kilometers wide.

Many of these secondary craters are concentrated in rays, or lines extending radially from Gratteri. Crater rays on the Moon are typically bright at visible wavelengths, but on Mars they are often best seen in the thermal infrared wavelengths, from temperature contrasts.

This image confirms that this ray contains many secondary craters--they are the small, sharp-rimmed craters. Since millions of secondary craters form at once, they all have the same age and same degree of modification over time.

Understanding the distribution of secondary craters provides information about impact processes, including escape of rocks that could become Martian meteorites on Earth.

Written by: Alfred McEwen

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