[swagasaurus-rex]

The samples mined from the Ryugu asteroid were contaminated by earth microorganisms some time between sampling and analysis. That makes it hard to tell the difference between potentially alien microorganisms and just regular earth microorganisms

[asdff]

You can still tell the difference through dna evidence. In this case it would be like a ship returning with an alien book, a worker left an earth based book, you have no clue what book is which but one book shares 99% textual similarity with the king james bible. That one probably originated on earth.

[jfengel]

Which is why I'd just as soon we waited a few extra decades before landing people on Mars. We're chock full of bacteria and they will surely get out. Unlike robots we can't be sterilized.

Once we can be certain that there is no native life, go nuts. Until then it's an irreplaceable bit of data.

[pavel_lishin]

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.)

[eru]

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.

[harshreality]

What's the point of all that effort if those habs are going to be one-way trips for the people going there? What are they going to accomplish in their floating or underground habitats? They're not getting back to anywhere useful from either place. They're not going to survive without frequent Earth resupply[1]. Whether habs could exist is an interesting thought experiment, but that's all it is for the foreseeable future.

Even a sizable Mars colony probably won't survive without frequent Earth assistance. The Mark Watney fantasy of growing food in Martian dirt with a little added fertilizer: mostly debunked[2]. The most sustainable case—for the foreseeable future—is probably a Biosphere2-like environment, where everyone hopes there's no accident, sabotage, or environment-caused damage. How many Starship missions would it take to get enough materials to Mars to build one Biosphere2 to support 8 people?

I agree with you that meaningful colonization of Mars is not serious. I just think the prospects on the inner inner planets are even more absurd than on Mars. In a floating Venusian hab, you could generate breathable air and not much else. Underground on Mercury, getting breathable air might be a problem, but you can import—at great cost, that delta-v is brutal—anything you can fit on a suitable rocket.

There's no point to any of this except as research stations or jump-off ports, and for that Mars is the obvious choice: we can make hydrocarbon fuel there, and the surface isn't equipment-melting. But where would we be jumping off to? We have nothing planned, and no particular reason, to send humans to Europa or anywhere else.

[1] How do you resupply a floating habitat on Venus? Even if you could, the constraints and resource limitations of a floating hab would be even more severe than for an underground, resource-poor Mercury hab.

[2] https://www.sciencenews.org/article/mars-farming-harder-mart...

[gambiting]

I've been saying this for ages - if you want to see if humans can survive in a completely sealed underground habitat(and it would have to be underground on Mars), just try building one at the bottom of the ocean.

And if you want a permanently occupied base in space....put one on the moon first?

[eru]

Yes, 'moon first' is indeed a strategy people discuss a lot.

[lmm]

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.