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Cool image time! While finding recent impacts on Mars is not that unusual, the image to the right, found among the November image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), was dramatic enough that I decided that more people besides planetary scientists should see it. For scale the photograph is exactly 500 meters wide.
The photograph, taken September 26, 2019, also illustrates all the typical aspects of impact craters, and how they change the landscape.
This impact took place sometime between July 17, 2012 and January 4, 2018. We know this because it wasn’t there in a low-resolution image taken by the wide angle survey camera on MRO on the first date but was there when that same camera took another picture on the second date. Below is a side-by-side comparison of that July 17, 2012 image with the high resolution 2019 image above.
The low resolution of the 2012 image makes it impossible to tell if the small craters in the high resolution 2019 image are new. Several look fresh, including the three inside the dark splotch. One or two beyond might have their own small dark aprons, suggesting they might be secondary impacts.
At the same time, this impact could have been caused by a relatively small bolide, which would then have been vaporized on impact and would have therefore left a very small crater. On that assumption, none of the craters here are new.
The asymmetric shape of the splotch itself suggests the three craters within it are new. To my eye it appears all three occurred at the same time, as the splotch seems extended sideways, as if it was made by three overlapping splotches centered on each crater.
To answer these questions, however, requires an understanding of impacts beyond my pay scale. It is possible that a researcher who studies these things would be able to estimate the bolide size from the size of the splotches, and thus determine whether or not the craters were produced by three simultaneous impacts from a object broken into three pieces.