It is clear that any form of life is to be expected on any planet. People tend to belevie that life on other planets has a lot in common with the life on our little planet... but as long as we keep finding new forms of (extinct) life on Earth, we should let go of any presumptions about the unknown life elsewhere.
If we look at Mars for example we look for places where life could (have) excist(ed) according to the biological rules of Earth. I think this way of looking at Mars is only useful for cononization purposes.
If we are looking for life on Mars, forget everything what is known about life as we know it first. And, I cannot stress this to much, we have to be exremely careful with sample return missions from any place. (Yes Zach, I know about the cross contamination that most likely has taken place many times before, but as this article is pointing out as well, It might not take such a long time for "new" life forms to emerge).

LOL, ok Prozac, I won't 'correct' you=)
I agree totally that we should still be very careful when dealing with sample returns. We don't want to bring life back from Mars and a scientist say 'Hey, thats a microbe from Earth!' and it actually be from Mars. As I've stated, I believe that any life we find on Mars will in fact have DNA and at least be distantly related to us. However, if we aren't extremely careful, we won't know if life we find is geinuine or contamination in a clean room.

I was just reading the side bar on Desolate Earth to stand in for Red Planet Exploring Mars -- in HANKSVILLE Utah Mars Desert Research Station operated by the Mars Society.
Began wondering if a dome and temperature control atmospheric simulaization was also possible to due (a biosphere 3) research for plant life experiment at this location.