Suppose some biological particle makes it to mars. Then we pick it up, discover that its very dead already, DNA sequence it and find that it matches the common flu. Write it off as contamination, rinse & repeat until we find something that is alive & looks like green men.
Or can science genuinely not distinguish earth contaminants vs alien life?
One possibility, perhaps very unlikely and perhaps somewhat likely, is that Earth life could actually survive and adapt to Martian conditions and subsequently destroy existing Martian life.
That seems almost comically improbable, but given that we've found that lichen can survive in the vacuum of space for a year and a half [1] and the mere existence of life on hydrothermal vents and inside Chernobyl[2], I think we can safely say that life is surprising.
So, if we accidentally terraform a planet with only microbial life, what's the downside?
The only loss I can see is the lost opportunity to study a truly alien ecosystem in detail, but if we can't study it without fatally contaminating it, that was never really a benefit we could enjoy anyway.
I doubt that the level of life succeeding enough to damage our ability to determine if there was already life there is on the same order as "terraforming a planet". I doubt there would be much upside.
Sure - by 'terraforming' I just meant 'replacing Martian life with Earth life'; terraforming from the microorganisms perspective perhaps, not from the perspective of humans. There's a lot of work involved in that, way beyond our current engineering capacity.
I'll make my thinking more explicit ...
The best case is that we either a) don't introduce microbial life, or b) it just flat-out dies. Then we can examine Mars for signs of life (current or historical).
The worst case is that we contaminate Mars with microbes that flourish there, forever destroying our ability to examine Mars for signs of life.
I'm assuming we can't explore Mars without risking the worst case. So it seems worthwhile to try; the very worst case is that we replace a Martian microbial ecosystem with one from Earth.
If there is life on mars, then it would be highly adapted for the Martian Climate over millions of years. It's unlikely that Earth Life would be able to out-compete them.
I think that's pretty reasonable, but if martian life has a completely different biochemical basis, it might be much less able to adapt. So, maybe, it has managed to hold on for a billion years, but terrestrial microbes may come equipped with a much richer genetic library, allowing them to adapt exponentially more quickly and overrun martian life.
Another way to look at it is that Mars seems to have almost no biodiversity, so it's possible that martian life forms may be well adapted to their environment, but not for competition. Terrestrial microbes have evolved in an utterly brutal competitive environment and they've been shown to adapt to extreme conditions, so it's not unthinkable that they may have a substantial edge over martian life.
Maybe. Just a laymen, so I could be totally wrong.
I know little about this stuff, but my impression is that there are so many different variations of life and also so many variations that can live in the most bizarre conditions, that we haven't even scratched the surface of classifying them all.
Something could survive the trip, grow, be found and still be entirely unknown to us. And it probably wouldn't be all that unlikely.
Take this study, that swabbed people's belly buttons and found thousands of unknown bacteria, bacteria only found before in foreign countries the person had never visited and "extremophile bacteria that typically thrive in ice caps and thermal vents"
Suppose some biological particle makes it to mars. Then we pick it up, discover that its very dead already, DNA sequence it and find that it matches the common flu. Write it off as contamination, rinse & repeat until we find something that is alive & looks like green men.
Or can science genuinely not distinguish earth contaminants vs alien life?