| MadSci Network: Astronomy |
This is a good idea, and provides an opportunity to experience a bit about how science works in practice. If you think about it, it is pretty clear that small-scale ruins could certainly be obliterated (or more likely just covered up) by the blowing dust which is common on the planet. So our first answer would have to be, "Yes, maybe". But if we stop there, we are left with a desire for a more definite, more satisfying, answer.
But we could re-phrase your question in a way that would allow us to say something more interesting:
"How big would any possible Martian ruins have to have been for dust to have not covered them and for us to be able to see them?"Then we could do some investigation and come up with an answer like,
"If there were ruins on Mars more than X meters high, we would have seen them, given what we know about the dust environment",where "X" is some definite number, maybe 30 or 200. Of course the interesting part of the job is to find X; if it turns out to be 2000, we haven't learned very much (after all, there are no ruins on Earth so huge), but if X=10, we have pretty much ruled out anything comparable to human artifacts on Earth.
Besides just dust, you have to think about other issues as well that could affect the results. The most obvious is how well have we really surveyed Mars, even in the absence of dust? Another is, how long ago do we want to consider? On the one hand, very ancient ruins might be more likely, since there is evidence that conditions were more favorable long ago. But many effects -- dust, meteorite bombardment, floods -- might have affected the visibility of ruins over a long time scale. If the atmosphere of Mars was once much denser than it is today, as seems likely, then dust storms in the past might have carried more material and been more destructive. Also, there is considerable evidence, still controversial, for an ancient ocean that once covered much of Mar's northern hemisphere.
Fortunately the Mars Global Surveyor (MGS) mission, now in progress, has revolutionized our knowledge of the planet, although the data are still coming in and have yet to be fully evaluated. Because of MGS, X is much smaller today than it was even two years ago, when the best information came from the two Viking Orbiters of 1976. Up until 1998 or so, it is not clear that something even the size of the pyramids of Egypt, say, would necessarily have been seen, dust or no. Now, the resolution of the MGS camera and, just as important, its systematic global coverage, will probably reduce X to a few tens of meters or less, small enough that dust could really be an important factor.
You can look up details about this information for yourself in the references. Because the third answer is, that to get a definitive answer to "What is X?" and to your question, you have to do a real scientific investigation! That is a lot of work, but also a lot of fun; so I'll leave you to pick up the trail and follow it as far as you like. I hope the references will give you a place to start.
One other thing is worthing noticing: we never really get a final answer to your question. This is very typical of real science. Early in the 20th century, Percival Lowell was convinced he saw mighty works of civilization with equipment that could not have had much better resolution than 100 km. In 1975 a student might have asked your question, and maybe decided X = 2000 m, based on data from Mariner 9. In 1985 someone might have found X = 300 m, based on Viking. Today X is probably dropping below 100 m, and dust is definitely something to consider in evaluating its significance. But of course intelligent Martian "super ants" might have once built a civilization with only small structures; or everything underground. So truly final answers are often hopeless, or at least quite rare. Yet in moving from Lowell's X of maybe 100 km a century ago, to the value of today (whatever it is, exactly) we have made highly worthwhile progress. So I hope you will agree that the process is still very valuable, even when our expectations are more modest than ultimate answers.
REFERENCES:
JPL general information on Mars and the other planets:
http://pds.jpl.nasa.gov/
Viking Orbiter data:
http://www-pdsimage.wr.usgs.gov/PDS/public/mapmaker/mapmkr.htm
General information about the MGS mission, its results so far, and links
to the images:
http://mars.jpl.nasa.gov/mgs/index.html
Information in the MGS cameras:
http://www.msss.com/mars/global_surveyor/mgs.html