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Humans with a level of technology roughly equal to the present day, not more than a decade or two more advanced (e.g. they might have slightly more efficient rockets, or a more miniaturized comm system, but no stargates, warp drive, or lightsabers), found a colony on the surface of Mars. Assume a somewhat stereotypical settlement infrastructure with landing pad, living habitat, hydroponic farm, research lab, etc., for anywhere from a dozen to a few dozen colonists. For some reason (because plot), the colony is abandoned (all of the people leave or die) while it is in working condition, and the colony site is then not visited by any life form for an arbitrary length of time (e.g. hundreds or even thousands of years).

How long would it take for the colony to become an unidentifiable, or barely identifiable, pile of rubble? We have a lot of archaeological data on how long stuff lasts on Earth before being effectively returned to nature, but would these measurements apply on Mars? As Mars has an active weather system (unlike the Moon), I expect that there will be significant erosion effects, but I doubt that the rate would be the same as on Earth. Would the colony last a hundred years? A thousand? Ten thousand? A million? A hundred million?

For the purposes of this question, "unidentifiable" means that the physical infrastructure has effectively returned to nature. Some remnants (e.g. scraps of metal, pieces of plastic, a screw or bolt here and there) can remain that testify to prior inhabitation of or at least visits to the area, but determining what those parts were from (e.g. telling that this aluminum board was from a Standard 12 Person Habitat (TM) manufactured by SpaceCo in 2022 as opposed to just knowing that it was probably built by humans or possibly another civilization at some point in time) would require at least a significant archaeological expedition and research project, not a casual glance.

Feel free to make any reasonable assumptions (if any) necessary to answer or simplify the problem by comparison with similar components whose properties are well-known (e.g. "If the colony was more or less a bunch of Apollo capsules welded together, based on what we know of their construction, the answer would be....")

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It would last forever (longer than humans anyway) although get covered in dust.

Mars has a thin atmosphere, so weather erosion would be negligible and it doesn't rain. Mars doesn't have microorganisms that we know of that will break things down. Mars is geographically stable it doesn't have earthquakes, volcanoes continental drift etc,. nor does it have things like weeds or vines that rip concrete and stone apart on earth. Even gravity is much weaker so stress caused by that is nothing compared to Earth.

So you're missing almost anything that would cause damage on Mars.

Judging by some comments too many people saw a martian storm in a movie and thought it was based on science instead of entertainment. I enjoyed the movie as well, but in reality the atmosphere is so thin a martian storm would have trouble blowing a piece of paper over.

Simple logic, water moving at 10 mile an hour will knock you off your feet and carry you with it, air moving at ten miles an hour is a gentle breeze, martian atmosphere moving at 10 miles an hour you wouldn't even notice. It's all about density.

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  • $\begingroup$ I was hoping for at least a little more thought. How long is "forever"? A thousand years? Ten thousand? A million? One hundred million? $\endgroup$ – Robert Columbia Mar 26 '18 at 19:23
  • $\begingroup$ It's made out of the stuff that modern-day spacecraft and space stations are made out of - so lots of aluminum, titanium, gold, and similar metals, cloth and plastic, etc. Use common sense. If you have an answer for a specific material, you could answer based on that (e.g. "I'm not sure about the plastic, but based on the work of Johnson (1970), most titanium structures would cease to be recognizable after about 10k years"). $\endgroup$ – Robert Columbia Mar 26 '18 at 19:26
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    $\begingroup$ I don't understand the downvotes. Measured rock erosion rates on Mars are on the order of 0.01 nm/year, or 0.01 mm per million years. So the answer is correct: for the colony to become unidentifiable it would take a far longer time than the human species can hope to exist. Consider all those beautiful pictures of dry river deltas: those rivers ceased to flow at least 3 billion years ago and yet the features are still clear. $\endgroup$ – AlexP Mar 26 '18 at 19:55
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    $\begingroup$ I don't understand the downvotes, either. Kilisi is fundamentally right. A longer, more detailed answer may be peferrable, but he's right, nonetheless. Look how long Roman structures have been around... and it rains on Earth. Martian sandstorms would wear down stone structures quickly, but modern metals? Wood? Yup, they'd be there for millennia and longer. $\endgroup$ – JBH Mar 27 '18 at 2:59
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    $\begingroup$ Mars' atmosphere is thin enough that it would be a creditable analog for hard vacuum in most cases. Kilisi is absolutely correct. $\endgroup$ – pojo-guy Mar 27 '18 at 15:19
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It depends on how the colony is constructed.

If the structures were build of aluminum, I would expect it to corrode, gradually being oxidized reaction with the CO2 in the atmosphere. The wind-blown sand would expose fresh aluminum surfaces, which would preeferentially bond with the Oxygen, leaving free Carbon.

But, based on some current Mars exploration thoughts (such as the Mars 1 mission), the structures brought from Earth would be temporary, to be replaced with new, larger structures fabricated with local meterials. One fabrication technique would be to 3D print a concrete-like material derived from Martian rock, dust, and water.

This material should not have a tendency to oxidize since the minerals would already be in an equilibrium condition with the atmosphere. I don't know how to gauge the wear resistance to wind-blown dust, but I would be better than aluminum sheet but not nearly as good as rock.

The power infrastructure could be a different story. Solar panels would be subject to dust erosion and scratching. A radioisotope thermal generator would degrade as the heat source decayed.

I'm going to guess that the station could be restored to operation for a couple of hundred years, recognizable as an active colony for 10,000 years, and identifiable as an intelligence created artifact for 100,000 years. I don't have any killer arguments, but it seems reasonable and could support many stories.

If the colony were built underground, it should be better preserved, but would be harder to find. We don't have active plate tectonics on Mars, so Mars-quakes shouldn't be much of a threat. The entrances would be subject to the same degradation and erosion effects.

I looked for a simple source of meteorite impacts on Mars to estimate the probability of an impact obliterating the colony, but I ran out of time. I found that the impact rate on mars was estimated to be, at most, twice the lunar impact rate paper discussing the estimation methodology, with the corresponding craters being smaller due to Mars gravity.

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It is true that there is no biology, rain rust or oxidization on Mars. But there is wind on mars,and it is moving the dust:
https://www.space.com/39776-mars-dust-burying-phoenix-lander-photos.html
https://en.wikipedia.org/wiki/Cleaning_event

Dust and wind mean abrasion, and it will wear everything down eventually. It will take a long time, longer than on earth. 100's of years for structural elements. Many of the walls will be thin sheets though, and those will be gone in 100 years tops,leaving the stronger skeleton of the building standing.

I also wonder if moving sands will bury the structures before they weather them away.

If you want remains of the colony to last longer, have colonists build stone buildings, or line their structures with stone.

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    $\begingroup$ dust erosion on Mars might destroy an exposed pound of butter in a few hundred years, but not a building $\endgroup$ – Kilisi Mar 27 '18 at 20:02
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    $\begingroup$ The top recorded wind speed on Mars is half the average hurricane wind speed on Earth. $\endgroup$ – rek Mar 27 '18 at 23:02
  • $\begingroup$ @rek sure but because the atmosphere is so thin, that wind speed would barely ruffle your hair $\endgroup$ – Kilisi Mar 27 '18 at 23:30
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    $\begingroup$ @Kilisi I know; my comment was incomplete/countering the idea that there's "wind moving the dust". Hurricanes aren't a primary source of erosion on Earth, so scale accordingly. I once read you could be in the middle of a Martian dust storm and not even know it. $\endgroup$ – rek Mar 29 '18 at 1:00

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