The Apollo astronauts' footsteps can remain theoretically forever on the Moon as it has no atmosphere. Mars does have an atmosphere but a very thin one. Its pressure ranges from 72 Pa (0.0104 psi) on the top of Olympus Mons to 1240 Pa (0.18 psi) in the Hellas Basin. Since this is quite a difference, I'm curious on both scenarios: how long would astronauts' footprints remain on Mars in case astronauts land on Olympus Mons, and in case they land in the Hellas Basin? Due to the low atmospheric pressures, the winds on Mars aren't by far as strong as on Earth.
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$\begingroup$ Related: space.stackexchange.com/questions/44847/… $\endgroup$– GiovanniApr 30, 2021 at 10:23
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$\begingroup$ This is a hard but interesting question! Storms do move stuff around even in short periods of time as demonstrated by these filty rovers. :-) See also Perseverance individual sample collection post-mission; what stops them from blowing away or getting covered and hidden by dust? (currently unanswered), and Brushing clean a Mars lander's solar panels and How are the Mars Rovers maintained? $\endgroup$– uhohApr 30, 2021 at 10:55
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1$\begingroup$ They could last a long time in a sheltered place, or be covered or blown after one storm. There's erosion even on the moon, as the regolith cover shows (micrometeorites and space weathering). Footprints there last +/- a very long time, but not forever. $\endgroup$– user40414Apr 30, 2021 at 11:02
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$\begingroup$ @Earthworm That's why I wrote 'theoretically'. $\endgroup$– GiovanniApr 30, 2021 at 11:04
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$\begingroup$ @Giovanni: theoretically quantitative erosion and weathering are unpredictable. Empirical models exist on Earth, but they can't experiment with that in Moon and Mars, yet ;-). So there'll be a huge span and uncertainty. $\endgroup$– user40414Apr 30, 2021 at 11:10
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3 Answers
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Several months to years, but not forever.
We (obviously) don't yet have astronaut footprints to examine, but we do have rover tracks to look at.
Here is a perfect example: Opportunity's tracks around Victoria crater.
As we can clearly see, over the span of one Martian year the tracks have faded a lot, but are still crystal clear.
Similarly, here is a close-up of the Spirit Rover's tracks during the 2007 global dust storm. In just 22 sols of severe duststorm, the rover's tracks have been 90% erased. You can still make them out, but they are mostly filled in and smoothed over.
Note that this was during an exceptionally severe storm, the like of which only occur one a decade or so. Mars does tend to have a lesser global dust storm ever 3 or so martian year, but the usual fare is not as severe as the 2007, 2018 storms were.
So realistically, expect wheel- and footprints on Mars to last 10 to 50 times as long as on Earth, but they will fade away in calendar time, not geologic time as on the Moon.
answered Sep 27, 2021 at 20:37
CuteKItty_pleaseStopBArkingCuteKItty_pleaseStopBArking
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$\begingroup$ Beautiful answer! This answer may also be helpful at Perseverance individual sample collection post-mission; what stops them from blowing away or getting covered and hidden by dust? $\endgroup$– uhohSep 27, 2021 at 23:48
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It would not last very long, as Mars is notorious for the dust storms present despite the low pressure of the atmosphere which sometimes kick up enough dust to be seen by telescopes on Earth. so technically it won't last forever like on the moon.
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1$\begingroup$ But there are little dust storms on Olympus Mons' peak, are there? $\endgroup$– GiovanniApr 30, 2021 at 10:27
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$\begingroup$ Question asks "..., I'm curious on both scenarios: how long would astronauts' footprints remain on Mars in case astronauts land on Olympus Mons, and in case they land in the Hellas Basin?" Actually I don't think we have a question like "How's the weather atop Olympus Mons?" or "Did the top of Olympus Mons disappear during the MY28 event?" yet; this might be a good time to ask! (1, 2) $\endgroup$– uhohApr 30, 2021 at 10:56
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$\begingroup$ Question asks "..., I'm curious on both scenarios: how long would astronauts' footprints remain on Mars in case astronauts land on Olympus Mons, and in case they land in the Hellas Basin?" Actually I don't think we have a question like "How's the weather atop Olympus Mons?" or "Did the top of Olympus Mons disappear during the MY28 event?" yet; this might be a good time to ask! (1, 2) $\endgroup$– uhohApr 30, 2021 at 11:02
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1$\begingroup$ This answer would be much more useful if you could provide quantitative data and/or calculatations as to what it takes to smooth, say, 10-mm 'footprint' features in Martian dust. $\endgroup$ Apr 30, 2021 at 13:06
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$\begingroup$ The answer is probably a few years perhaps in Hellas Basin. For Olympus Mons the period would be much longer may be thousands or even millions of years but the calculation would be very difficult. The true answer is we don't know in any detail or with much accuracy. $\endgroup$– SlartyApr 30, 2021 at 16:47
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As Sujay says, Mars is known for it's dust storms, therefore footprints wouldn't last long on the surface. The regional Martian dust storms tend to happen in the summers and the larger, planet wide, storms every few years.
However, while I cannot find anything categorically stating the dust storms don't reach the top of Olympus Mons. The vastly lower pressure (around 30Pa compared to around 1200Pa on Hellas Planitia) - https://planetary-science.org/mars-research/martian-atmosphere/ - makes me think that they likely don't; and even if they do, it would mean they carry vastly less material and therefore, footprints on the top of Olympus mons may be able to last an extremely long time.
