Someone should stop to consider a few facts about natural law before jumping to any conclusion.
The first fact, which I'd have thought to be the most obvious, is the seemingly complete lack of wood on Mars. There are no trees, nor are there
suitable environments for trees as we know them to grow. Also, if there were trees capable of withstanding such an environment to begin with, we'd
see more of them; trees tend to cover landscapes in a short amount of time, geologically speaking. So, logically, if there were trees on Mars,
they're quite rare, which would make a plank of wood even more rare; I doubt any intelligent species would leave a rare, and presumably valuable,
object just laying around in the open.
The second fact seems equally obvious. If at one point Mars were more suitable for life, and trees and such flourished on the surface (personally, I
think it quite likely), by this time every trace save the most minute or frozen traces would have been turned to dust. The sheer amount of solar
radiation, when paired with the destructive strength of the dust storms which plague the planet's surface, would have completely eradicated any
trees, twigs, or unlikely planks.
Now there are some people who may respond with a few idiotic answers such as 'Mars has no atmosphere' or 'maybe the alien dropped it', but by
simply picking up a book and putting aside conjecture these thoughts can be put to rest. Mars has an atmosphere, albeit a poor one, as well as water,
dirt, and weather; hergo, erosion occurs, and natural formations change as frequently as upon earth. And I believe I already covered why the alien
didn't drop the plank.
The last fact is something I find myself saying again and again, though. Why in the world does everybody assume that all life is carbon based? They
may very well be a thriving society on Mars standing right next to the rover, but we wouldn't recognize it; our biological studies are entirely based
upon the assumption that carbon-based life is the only means possible; hence, it is stupid to state with certainty that there is no life on Mars.
Simply because we lack the means to recognize other forms of life, and by what biological rules they abide, does not mean that they do not live.
What if I were to tell you that I'd found a creature which had no head, no heart, no skeleton, no lungs, could re-grow limbs, and had the ability to
reverse its own aging process and revert to childhood? Would you believe me, or would you laugh and demand proof? I doubt most scientists would even
give a glance to such a claim. However, what I just described to you is real. It is a jellyfish in the Mediterranean Sea called the Teratopsis (I
may have mispelled it); this tiny jelly have the ability to revert to a medusa if needed, which is a quality unique to this creature. There is no
other animal of any kingdom known to science which can turn back its own biological clock. The point is that we have no idea what organisms may exist
out there until we find them, and even then, we have no idea how they can do the things they do. We're perhaps millenia from conclusively stating
that Mars is a dead planet.
(Edit)
Just came back to say one more thing. For some strange reason, I couldn't find a single page on the web about my forementioned jelly. However, if
you want to know more about our gelatinous friend, watch the Science channel and look for a show about...well, jellyfish. Its called Super
Animals.
[edit on 5-12-2008 by Malfeitor]