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Some details about the planet and its moon plus the host star.

Star: 0.85 Sol, 0.54% of the Sun's luminosity

Planet: 0.04926 (M⊕) 4836 km, 0.34 G, Orbits the host star at 0.901 AU.

The atmospheric pressure on this planet is 0.20% of the Earth's which consists of:

85.4% O2, 9.16% CO2, 3.89% N2, 1.2% SO2, H20: 332 ppm.

Moon: 0.002 (M⊕) 770 km, 0.12 G, Semi major axis of the moon is 26415 km. Orbital eccentricity of the moon is 0.031.

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    $\begingroup$ I doubt that planet would have an atmosphere that is possible to breathe... mars is 0.107 M⊕, and we can't even use parachutes.... Maybe water bears? $\endgroup$
    – user23110
    Commented Sep 20, 2016 at 14:25
  • $\begingroup$ Is that a typo for your atmospheric pressure? If not, i don't think any thing (apart from maybe bacteria) could breathe there $\endgroup$
    – Burki
    Commented Sep 20, 2016 at 14:29
  • $\begingroup$ @Burki Well, 0.049 Earth masses and 0.20% surface atmospheric pressure does sound about right to a first order approximation. $\endgroup$
    – user
    Commented Sep 20, 2016 at 14:32
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    $\begingroup$ Stephanie, while I can appreciate that you probably made an honest mistake in this case, it really isn't considered good form to make such a drastic change as you did (0.20% of Earth atmospheric pressure to 20%) after answers have been posted. At that point, if you realize you've made a mistake like that, it would be better to post an entirely new question because the answer is going to be completely different. I won't roll back the edit unilaterally right away (I could), but I really encourage you to roll back your edit, and then post a new question with the corrected premise. $\endgroup$
    – user
    Commented Sep 20, 2016 at 14:50
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    $\begingroup$ Please read this meta question - it shows how frustrating are changes for people who answer. $\endgroup$
    – Mołot
    Commented Sep 21, 2016 at 8:31

3 Answers 3

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Atmospheric pressure 0.20% of that on Earth's surface?

Take a look at the phase diagram for water:

enter image description here

0.20% of 1 atmosphere pressure means about 2 millibar. At that pressure, liquid water cannot exist; at about -20 degrees C, it sublimates from ice to vapour. At that pressure, below -20C, water is a solid; above -20C, it is a vapour.

No higher life on Earth is equipped to deal with such conditions.

It is possible that some extremophiles may be able to survive by hibernating, but I very much doubt that they will be able to reproduce under such conditions.

So the answer is no, animals from Earth would not be able to survive and reproduce under such conditions.

And that's before we even consider the composition of the atmosphere.

In order to be able to have the three phases of water that we are used to (solid, liquid and vapour) the temperature and pressure have to be between the triple point and the critical point, so somewhere in the range 611.657 Pa (at no less than 273.16 K) to 22.064 MPa (at no more than 647 K).

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  • $\begingroup$ @tuskiomi The tardigrade is a member of the group extremophiles. And I still doubt they would be able to reproduce, so even they fail at least one of the OP's two criteria. $\endgroup$
    – user
    Commented Sep 20, 2016 at 14:32
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Well. Obviously, what is being asked is about a planet with 20% of Earth's atmospheric pressure, and its sun with 54% of Sol's luminosity. A question about a planet with 0.2% of Earth's atmospheric pressure, orbiting a sun with 0.54% of Sol's luminosity wouldn't be even minimally interesting, as the obvious answer would be, NO, too little air, too little light.

I think that your atmospheric pressure is too low for most forms of Earthan animal life; the atmospheric pressure at Mount Everest is about 30% that of sea level, and it is irrespirable for people. At least, it would be certainly lethal without previous adaptation.

But the biggest problem, that you would have to handwave, or to create an elaborate explanation for, is that a planet with so much oxygen must necessarily already have some kind of life - of photosynthetic life, to be precise. This means that a huge problem for xenoorganisms there - supposing they could physically survive - would be their interaction with the local ecological system. Plants could be toxic, microorganisms could be pathogenic.

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Regardless of the incorrect percentages in the question, there's not enough nitrogen. There's less than 1% as much as in the Earth's atmosphere, so there's going to be nothing like enough available for plants. Earth animals might survive, but only if you import all their food from off-world.

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