Other planets atmospheres

[sherminator]

ok prob complete science fiction here. But if we found another planet and its make up was 'like' ours in that it was oxygen and carbon dioxide that made up the atomosphere theh how different could the percentage split be of each chemical and our bodies would be ok there?

like say its a 90:10 split just now if it was say 80:20 would that make a colssol difference or could we survive and adapt on such a planet?

hope that makes sense!

[Backdrifter]

By the way our atmosphere is mostly nitrogen and oxygen.

Do you mean, as ours is 78% nitrogen and 21% oxygen, and we found a planet that was say 90% nitrogen and 10% oxygen, would we survive there? If that's what you're asking, no we wouldn't.

[sherminator]

yeah sorry couldnt remember exactly what ours was and what the split was.

but ok so what if it was like 70% nitrogen and 29% oxygen? could we survive that and what difference would it make to us?
and perhaps the better question is what could we survive in? where is the limit of what our bodies can stand?

[jake-the-peg]

The pressure is important as well as the composition.

Oxygen in too high a concentration is toxic to us. When sports diving there's a limit of 50 meters because of this.

I think it's about 90 meters which is the absolute limit below which it's really bad.

That's about 10 atmosphere's pressure abolute so we could manage with a 100% Oxygen atmosphere provided the pressure wasn't much above say 1.8 that on Earth.

Although the fire risk on such a planet would be really bad

As for the other end of the spectrum - well the highest inhabitations are at about 5300m where there's about 1/2 the atmosphere

So if the pressure was the same we'd need at least 10% Oxygen

[sherminator]

Cheers guys! So we could then survive on other worlds!!
Am guessing the chances of finding one exactly the same as ours are infinitely small so just hoped that if we do ever find one we could settle?

[R1Geezer]

Further to the atmospheric pressure/content another consideration is the temperature, the Earth is in the goldilocks zone, ie not too hot, not too cold so making it another magnitude of rareity. The sheer number of planets and stars even in this galaxy means there are still plenty out there but all too far to reach unfortunately! However we have around 5billion years left here so ok for now, we'll probably self distruct before then anyway!

[sherminator]

It really will be quite extraordinary to find a planet like ours then!!!
Ok.... IF we did find another planet very similar to ours.....is there any rationale for determining whether there would be life on it.
for example we find another planet exactly same conditions as ours, would that guarantee life on that planet?

[chakka35]

Since we still don't know how life came about on this planet there can be no guarantee of life elsewhere. If, as is likely, it came about by the chance meeting of the right chemicals in the right conditions, then there is certainly no guarantee that that will happen elsewhere, though it might.

[Milvus]

There is a calculation that was devised in the 60's to predict the numbers of planets that would develop life and the numbers of life forms that would develop far enough to enable some form of communication. This was developed by Frank Drake and not surprisingly is known as the Drake equation. Wikipedia has a good section on it

[jake-the-peg]

Remember too that the Earth did not originally have free Oxygen in it's atmosphere that was a by product of life.

If you find a planet with an oxygen rich atmosphere there is almost certainly life already on it

[chakka35]

Very good point, jake.

[sherminator]

Thanks Jake that s what I meant. I so long for the day that we get to see a planet like that. Just to get everybodies imagination going!!