Click for full image.
Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken in May 2008 by the wide angle context camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists have since labeled a “peanut-shaped crater.”
What caused this unusual shape? The obvious and most likely explanation is that this was a double impact that occurred simultaneously. Imagine the ground being hit either by an asteroid with two lobes or by two similar-sized asteroids falling side-by-side.
Fast forward thirteen years to 2021. In the fifteen years since 2006 when MRO begin science operations in orbit around Mars no high resolution images were taken of this crater. Finally, on July 30, 2021, scientists finally decided to take a high resolution image of this crater’s western half. You can see that image below, rotated, cropped, and reduced to post here.
Click for full image.
This new close-up to the right now focused on what had been learned in the thirteen years since 2008, looking closely at the material in the crater’s floor as well as its interior rim where there appear to be gullies.
In the past decade, using MRO images, scientists have determined that while the equatorial regions up to 30 degrees latitude are very dry, the mid-latitudes from 30 to 60 degrees have numerous glacial and ice features on the surface, covered by a thin layer of dust and debris to prevent them from sublimating away.
The overview map below illustrates this, and why the scientists came back to take this new high resolution image. The white box marks this crater’s location. The black box marks a previous cool image posted in June 2021 of a very different geological feature.
Located at 33 degrees north latitude in the northern lowlands of Utopia Planitia, about a thousand miles to the northeast of where China’s Zhurong rover landed and north of the 30 degree latitude that divides the dry equatorial regions from the glacial mid-latitude regions, this crater should almost certainly have glacial material in its interior. And the high resolution image confirms this, with the crater floor clearly filled with what looks like typical glacial fill.
In addition, the crater’s interior rim slopes have gullies that need study, as they might also show evidence of frost, ice, or even water erosion.
When the context image was taken in 2008, however, the prevalence of glacial material and ice in the latitudes higher than 30 degrees was not yet established, which partly explains why so much time passed before a follow-up high resolution picture was taken. This crater was given a lower priority, which now has been raised somewhat by the later data.
Of course, another reason no hi-res image was taken for so long is simply that MRO can only do so much. It will likely never be able to image the entire surface of Mars in high resolution, so large areas will simply never be photographed by its hi-res camera. For example, no high resolution image has yet been taken of the splash apron that surrounds this crater in the context image above, likely caused because the impact bolide smashed into a near-surface layer of ice that quickly melted from the impact heat, splashed outward, and then quickly refroze. High resolution data of this apron would be useful, but as I say, MRO has only so many days in the week.