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black hole1
Screenshot from Mars Trek

This enigmatic crater lies in southern Utopia Planitia at 28.72⁰ N, 119.96⁰ E, is about 10 km wide and has a min. height difference between its floor and rim of ca. 1650 m.
The crater's floor has the lowest elevation of minus 6 km on Mars between its latitude and that of the northern rim of the Hellas basin.

Could it be that the structure and/or the composition of the surface material inside the crater cause it to be radiation-absorbent ?

Dark hole
Screenshot from Mars Trek

The image above shows the second "dark hole crater" in Utopia Planitia at 39.5⁰ N, 105.4⁰ E, about 900 km to the northwest of the previous one. This one is about 12 km wide and here you can clearly see its flat floor.(flat, according to Mars Trek)

As far as I know, these two craters are of the few ones on Mars that look like dark holes with bright rings.

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    $\begingroup$ Since all materials absorb some part off the EM spectrum, yes. $\endgroup$
    – Jon Custer
    Nov 21, 2022 at 0:52
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    $\begingroup$ Am I seeing things, or does the crater appear to have something that looks like a wedge inside? $\endgroup$
    – Fred
    Nov 21, 2022 at 7:53
  • $\begingroup$ You might be interested in the 5 papers being presented in Stream B during the first morning at this conference later this month, 28 November 2022. $\endgroup$
    – Fred
    Nov 21, 2022 at 8:00
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    $\begingroup$ Contrast is often enhanced on planetary photo, to see details better. So, without actual albedo info it's hard to say how dark the crater is. $\endgroup$
    – Heopps
    Nov 21, 2022 at 9:27
  • $\begingroup$ Regarding the first photo, the white material could be reflective glare. The 10 km wide crater has two smaller craters nearby; one to the southeast & the other to the northeast. Both of these have what appears to be reflect glare on their southwestern interior walls. The white stuff around the large crater appears to be on the outer wall of the rim on the right side of the crater & on the inner wall of the rim on the left side of the crater. $\endgroup$
    – Fred
    Nov 27, 2022 at 9:33

1 Answer 1

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This seems to be some unlucky stitching of two individual images taken at very different times of the day. In the first picture you can clearly see an almost vertical line stretching through the whole picture.

The left half has been taken with illumination from the left and the right half had light coming from the right. You can clearly see the difference inspecting the three small craters in the image - the light comes from different sides.

Due to the stitching we now see both (left & right) outer rims lit from the side, and both halves of the crater floor and inner walls in the shadow.

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    $\begingroup$ A simple and credible explanation, thanks. $\endgroup$
    – Cornelis
    Nov 27, 2022 at 11:33

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