Will we kill or contaminate microbial life on Mars? | Hacker News Reader

Will we kill or contaminate microbial life on Mars?

kurzweilai.net

11 pointsjonbaer16 comments

One thing I wonder about is if we go to Mars and find microbial life at some later point. Will we ever be able to be sure that the microbes were there before us, or did we bring them with us without realizing, after which they reproduced until we detected them?

The concepts you are referring to are called: Interplanetary contamination[0] and Planetary Protection[1]. There are precautions that take place before a spacecraft, targeted at possible sources of microbial life is launched. The operations vehicles are basically sterilized beforehand.

>> "The aim of the current regulations is to keep the number of microorganisms low enough so that the probability of contamination of Mars is acceptable"

Contamination can happen both ways. Not only on the way to the planet but also on the way back, if a sample-return is involved. The sample must be kept sterile on the way back to earth, to the lab, and in the lab without destroying information by sterilizing it again...

[0]: https://en.wikipedia.org/wiki/Interplanetary_contamination

[1]: https://en.wikipedia.org/wiki/Planetary_protection

If we contaminated Mars with microbial life from Earth, it would have a similar genetic signature to sequenced organisms on Earth. Assuming we could get a DNA sequencing machine up there, it would probably be obvious that the organism originated from Earth unless it was some previously undiscovered Archaea.

Sure, assuming that we find life that is significantly different than life on Earth. If all we find is microbial life that is genetically similar to that on Earth, then you might be inclined to believe we brought it there, but it seems possible there might be no way to know for sure.

The Martian surface is bathed in radiation, a near vacuum, and very, very dry. If there is life on Mars, I think it is likely to be far enough underground that nothing we do short of outright terraforming the planet is likely to make any difference to it.

And yet every mission to Mars has a major component searching for evidence of life e.g. [1]. How long before space agencies stop bothering? I guess the whole "could be evidence for possible biological activity" thing is only part of the science, but it annoys me that its given such a large apparent weight.

https://en.wikipedia.org/wiki/ExoMars_Trace_Gas_Orbiter

Considering they have evolved in two totally separate (millions of miles away) environment for millions of years, I'd doubt that microbes from Earth could have any meaningful direct interaction with microbes on Mars.

Some people have seen too much Independence Day/Twilight Zone.

Could you ground that assumption in some physical reasoning? Microbes are incredibly resilient and adaptive in general. If microbes on Mars are DNA based, then contact with Earth microbes would be inherently meaningful.

Many microbes proficiently incorporate external DNA. My friend was just telling me recently about multinucleate fungi that can spawn up new nuclei in which to contain dna absorbed from their environment.

Some microbes specialize in living inside other microbes. These are called intracellular parasites, and it is thought that such relationships actually account for the development of common organelles.

If humans jump to conclusions in order to colonize Mars without careful ecological study, it will be a tragedy of ignorance.

> Could you ground that assumption in some physical reasoning? Microbes are incredibly resilient and adaptive in general. If microbes on Mars are DNA based, then contact with Earth microbes would be inherently meaningful.

I don't think I need to. True, if martian microbes are DNA based then that obviously increases the chance of cross contamination/interaction. But we don't know that any life we find outside of Earth will be DNA based at all. We look for signs of DNA based life, and environments that are conducive to DNA based life because that's the only life we know how to look for. It's the only real life we know. But it is not outside the realm of possibility that the first extraterrestrial life we find, whether orbiting Alpha Centauri or on Mars, isn't DNA based. Personally, I think it's pretty closed minded and Earth-centric to define life (complex or microbial) in that manner.

I think this would be more accurately framed as a chemistry question. Without knowing the underlying chemistry of extraterrestrial organisms, we can't really make meaningful statements about how they might interact with DNA based life.

You can certainly imagine simple, yet highly adapted, microorganisms evolving in the Martian environment where competition is scarce. In this situation, our quite robust terrestrial organisms might overwhelm native populations simply because they are much more adaptable to change and competition with foreign bodies.

This still doesn't even touch on the compatibility of the biochemistry. Perhaps life from either origin attempting to consume one another causes volatile chemical reactions, destroying one or both organisms. In this scenario it would come down to which (if any) evolves the necessary chemistry to consume and/or avoid the competition first.

More broadly, the introduction of any foreign chemistry at all could be destructive to native populations, let alone the introduction of new life forms. Given the complexities involved and lack of data, I wouldn't feel comfortable making a case one way or the other.

I don't know much about microbiology, but I'm not sure that there will definitely be a huge difference between microbes on Earth and microbes on Mars. It could very well be that life was delivered to Earth from Mars at some point in the distant past.

Perhaps the only places that microbial life exists on Mars are in places that have conditions similar to Earth. Underground water, etc.

Even if Mars seeded Earth, evolutionary pressure and the passage of time would make Earth microbes and Martian ones very different. Which goes to my point.

I wouldn't be too sure about an inability to interact. Given what we know about the fundamental laws of chemistry, it's entirely possible that the formation of life as we know it may be the only real way life can form. I wouldn't be too surprised if we discovered microbes that look and function very similarly to our own viruses and bacteria, etc., including DNA/RNA or some very closely similar molecule and mechanism.

But overall I agree with you. There are likely to be many differences, and even if they were exactly like Earth microbes the chances of them bothering us or us bothering them would be just as unlikely as a chimpanzee catching a cold from an iguana.

I think it much more likely that they could be biological irritants or even toxins, if indeed they affect us at all.

I think the main concern is that we'd want to study them as isolated lifeforms, and any Earth proteins or other contaminants would greatly hinder such studies. Even if we could clearly separate out the contaminants, we couldn't be certain if the Martian organisms had reacted to the Earth substances in some way.

> Given what we know about the fundamental laws of chemistry, it's entirely possible that the formation of life as we know it may be the only real way life can form.

Our form of life could be the only kind possible, but that's nowhere near proven as fact.

I agree with the rest of your statement though.

And since life probably formed (in the same way, in deep-sea vents) on Mars and Earth in parallel, and was later exchanged via impacts, life on Earth is probably partially Martian anyway

Historically the answer has been "Who cares?".

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