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Several bars of CO2 are inhospitable to life evolved in an atmosphere of several hundred ppm of CO2, sure, but are there arguments that high levels of CO2 would
by maxander 7y ago
Several bars of CO2 are inhospitable to life evolved in an atmosphere of several hundred ppm of CO2, sure, but are there arguments that high levels of CO2 would be detrimental most possible lifeforms out there?
(CO is much more reactive, but it's harmful to us because it reacts to our hemoglobin in much the same way as oxygen. So since Earth life has managed to get on just fine with all this corrosive oxygen around, the same argument may still apply.)
- scythe 7y agoI think so, actually. The reason is that usually carbon-based life gets its carbon from CO2. But life doesn't stop growing because it's going to kill itself, cf. global warming. So photosynthesis on these planets might continue until their atmosphere is drained of CO2 and they freeze. Then again, I suppose there could be an equilibrium, but that equilibrium would require the planet to remain "uncomfortably" cold to suppress photosynthesis. Of course, that's a completely different argument from the one the researchers had.
- ailideex 7y agoHas this not happened on earth already? First plants caused ice ages, new research reveals : https://www.sciencedaily.com/releases/2012/02/120201094923.htm https://www.sciencedaily.com/releases/2012/02/120201094923.h...
- azernik 7y agoYup! And then we reached a (very-low-carbon) equilibrium.
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- yread 7y agoMaybe they're looking at us and think "What 21% O2? Surely no life could exist there, everything would just burn down immediately!" EDIT: "Especially in combination with water vapour in atmosphere - it would freeze, static charge would build up between the ice particles and the discharge would ignite everything. Indeed the fact that O2 is so high is a proof that there is nothing left to burn"
- ddxxdd 7y ago>Maybe they're looking at us and think "What 21% O2? Surely no life could exist there, everything would just burn down immediately!" I swear, this is an exact line from a Ray Bradbury story that I read as a child.
- mannykannot 7y agoAlso Clarke, in the title essay of 'Report on Planet Three'. The flaw in this argument is that an out-of-equilibrium concentration of oxygen implies a process to maintain it.
- dusbajd 7y agoO2 is a triplet state molecule, so it has huge kinetic barriers for reactions. > No alien species advanced enough to look at us would assume we’d burn just because we have 0.21 Po2 The fact that there is excess of a reactant really means that there is an ability for interesting reactions, and therefore life. Ash cannot be animate because it’s (basically) at ground level and does not have the free energy to do anything.
- simonh 7y agoWhat they should be thinking is, O2 is very reactive. There must be some active chemical process, powered by a pervasive energy source going on at massive scale replenishing it constantly. What on Xebron 5 could that be?
- dusbajd 7y agoCO and CO2 are different. Like you mentioned, CO is bad for us because of our hemoglobin. Otherwise I could imagine life using an otherwise chemically interesting molecule like CO (it can oxide further). CO2... not so interesting. Aside from the reaction to make CaCO (?) and acidic when dissolved in water it’s quite limited being fully oxidized. You need the ability to make things out of your molecules. Stuff at the ground state are boring! Plants expand energy (otherwise wasted sunlight) to convert CO2 into O2 to make an interesting molecules, namely starch with which they can do something. If they had an endless supply of starches, they wouldn’t have bothered evolving with photosynthesis - just like we don’t care for photosynthesis since we have plants.