Click for full image.
Today’s cool image comes from today’s Mars Reconnaissance Orbiter’s (MRO) high resolution picture of the day, rotated and cropped to post here. The original was taken back on March 28, 2017.
What formed those strange circular ridges and the many small cracks and hollows? The caption provided is somewhat vague and I think confusing:
This formation looks like a crater from a meteor impact rather than an ancient caldera of a volcano. Connected to the crater is a carved-out area that resembles a lake bed. At high resolution, we might be able to determine the likelihood of a water lake bed or lava bed. This observation will give insight into some of the interesting geology of this area.
The crater this caption is referring to is not visible in the image provided. It can be seen to the west of this location, in the MRO context camera picture below.
Click for full image.
The white box marks the location of the photo above. The crater referred to in the caption is the rimless round crater to the west of the very irregularly-shaped depression. The caption says that crater was probably created by an impact, but the lack of a rim suggests otherwise.
I think the answer, based on our presently very limited amount of information, is hinted at by the location, which is at 80 degrees south latitude, only about 400 miles from the south pole, as shown by the green cross in the overview map below and to the right. The answer is also indicated by the many glacial-like features that seem to permeate the crater, the surrounding terrain, and the primary photo above.
What we have here might be an ancient volcanic caldera or dried lake bed — as suggested by the caption — but I think the influence of glacial ice has been far more important to its formation. The surface features seen throughout these photos all appear to be glacial ice, with some showing layers signaling many cycles of formation and then sublimation. Those cycles likely worked to not only erode the crater, they carved out the irregular depression.
In the photo above we are getting a close look at some of that ice, which appears possibly exposed so that much of it can sublimate away when the Sun hits it. Thus, the cracks and hollows.
The particular location in the top photo also appears to be the resurgence for ice leaking from that irregular depression. The multiple ridges near the photo’s bottom also suggest multiple glacial flows, each traveling a shorter distance and thus leaving multiple moraines forming those ridges.
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