If we dug a really big hole on Mars, how long would it last?

How long will a 400 km wide 30 km deep pit (trench or crater) with a relatively shallow (for stability) gradient of slope of 20 degrees from the edge to the surface of the planets crust be expected to last on Mars before geological & climate processes close it.

Rock plasticity under the weight & pressure of the rocks above is one potential concern that's been identified for me, I think only 30 km depth may avoid that but I'd like to be sure.

I'd prefer 41 km deep (as that should give us an atmospheric pressure roughly equivalent to a height of 6 km on Earth where our highest plants grow) & with an average crust thickness of 50 km thought that should be OK .. until it was suggested to me anything lower than 30 km would slowly fill back up from the bottom to a depth of 30 km, but at least 30 km should still put us below the Armstrong limit.

How long could we expect the structure to remain viable & retain a depth of at least 29 km?

posted over 4 years ago

Pelinore‭

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