Rapid colonization of a space-returned Ryugu sample by terrestrial microorganism

Where specifically are you getting that information?

From TFA:

The nitrogen atmosphere, in which the sample was stored during this time, can be a bactericide for some, but not all, Bacillus species owing to the reduced water activity associated with the dry atmosphere (Munsch-Alatossava & Alatossava, 2014). The bactericidal effects of such atmospheres are not restricted to Bacillus, and thus provides no diagnostic information.

That is: nitrogen should generally kill bacteria, but may not in the case of some Bacillus species. That's quite some distance from saying the bacteria would thrive in that environment, and I'd presume other factors (light, food supply, some means for oxidation) would be necessary, most of which could be reasonably constrained within a sample-examination environment.

Origin determination might be made through C14 or other dating --- any extant in situ bioactive materials would presumably be comprised of primordial carbon with effectively no C14 signature, as opposed to any recently-deposited or growing organisms.

One challenge seems to be that there was very little Bacillus present, 11 to 147 individuals, which seems to have made DNA analysis impractical and would likely challenge isotopic analysis as well.

NB: Not my area of expertise, just close reading, general understanding, and some research-fu.

Chemical space is very very large. Like we can say for certain that only a very tiny percentage of all possible synthesizable organic molecules have ever existed in our universe. The combinatoric explosion is just so enormous that I think its incredibly unlikely that the only configuration of molecules that supports life is our own here on Earth. In fact, I think we know this given that there are artificial amino acids that can be incorporated into our existing protein biochemistry without a problem. Thats a small example but it points to a much larger space of chemical compositions that can support life. So an entirely separate evolutionary process would almost certainly land in a very different chemistry for things like information storage and molecular machines like protein.

Also our biochemistry is compositional, it takes small building blocks and remixes and combines them to build larger structures. I suspect that this is also a necessary feature of life in general. It’s very hard, basically impossible, for natural evolution to build huge structures like proteins just by pure uniform random selection. Instead it takes small pieces randomly, then puts them together to get complex life.

Point being, its a very very path dependent process. Any small difference in the early building blocks gets exponentially magnified when evolution uses those blocks to build life. So that leads to easily detectable, drastic differences in biochemical structure. This is evident on earth in that our biochemistry has a feature called left handed chirality that seems to be a purely random accident of the very earliest steps of life. That then was transmitted to every living being on earth. There’s probably a fifty-fifty chance that extraterrestrial biology is right handed instead. Every step in evolution also probably has random accidents just like that. Our particular biochemistry is the result of a trillion coin flips. There are probably many other biochemistries that work just fine, but look way different

You’d sequence this organism. If it came from earth you could tell. People would have either sequenced it already or a distant relative species where you could compare sequence divergence and when they shared a last common ancestor. Convergent evolution might lead to similar phenotypes but the actual sequence of genes involved is only going to be similar if those genes shared an evolutionary history.

> How would we tell?

You'd send a second mission to do analysis in situ.

Alien samples won’t have carbon-14, which is created in the atmosphere.

By that standard, any room you've even been in is "crawling with bacteria." The ISS is cleaned constantly, with a deeper cleaning once per week.

I think any odors would be more related to using dry toilets, stretching clothing in the absence of laundry facilities, and hosting a gym (2 hours exercise per day per crewmember) with no shower. No Rinse Body Bath only goes so far.

https://www.youtube.com/watch?v=JUUvlnnVMSQ

There is a reason they send rovers in places they expect to find ancient life and not present day life.

I am not opposed to it in most cases for any moral reason, but if we did accidentally contaminate an example of even incredibly simple ET life it would be an enormous scientific loss. What one second example of life could teach us would be massive. Contamination would mean we could never be sure we were studying the authentic thing.

It would certainly be interesting to see what survived.

Yeah if there’s no life there already, then we should probably go ahead and put it there and see what happens.

We’d have to be real sure that there’s no life there already though.

Even robots cannot be sterilized; we've likely already infected Mars with some form of life. (Although, it's not likely that it's gonna spread far - it's a wildly hostile world.)

Agreed. And Mars isn't even a good target for colonisation. Venus and even Mercury are better, but constructing space habitats is even better.

On Venus, the surface is crazy hostile, but the atmosphere is so dense big balloons filled with a nitrogen / oxygen mixture, aka breathable air would float rather nicely, and at a height with pretty liveable temperatures.

Mercury's surface has extreme temperature variations between night and day. But if you dig underground---which you would want to do anyway for meteor protection---you'll find that the variations average out, because large amounts of rock are a good heat buffer. Models suggest that near the poles there are underground regions with nice and liveable average temperatures.

Solar energy is obviously much stronger at Venus's distance from the sun than for Mars.

On Mercury, thanks to the consistent temperature variations, you could probably set up your standard issue steam turbine power plant fairly easily, just your sources of heat and cold would be a bit more interesting than on earth.

There are zillions of Mars-like planemos in the galaxy - hell, there are 4 pretty similar ones just in our solar system. But Mars is the only one close enough to colonise. And if we don't colonise Mars, we'll probably never get far enough to study any of the others.