If we were to discover oxygen on an exoplanet, say with the Webb Telescope, would that necessarily indicate life there?
IIRC, water is the only essential. Oxygen can exist with or without life, and life can exist with or without oxygen. Unless oxygen can only be generated via plants, but I’m pretty sure some mineral/chemical reactions can make it, sans life.
Oxygen can react with a lot of other atoms and get locked away. Water, rust, carbon dioxide, etc. Anything that oxidizes puts oxygen away.
So if we are seeing atmospheric oxygen, odds are something is “recharging” the oxygen in the atmosphere.
Photosynthesis aka life is what does it here, but there are some abiotic processes too. Still, it’s a sign.
To the best of our knowledge, water is essential for life, but that’s not too big a deal: There are plenty of places with water. Finding a planet with water is interesting, but might not mean anything.
Also to the best of our knowledge, life is essential for significant amounts of elemental oxygen. So if we find a world with oxygen, that’s much more interesting.
That said, other methods of getting an oxygen-bearing world have been discussed, but it’s not clear how plausible they actually are. If we ever discover one, expect a lot more talk about that.
I was going to post what @Babale did. Students of chemistry find out quickly that oxygen is incredibly reactive (thankfully not Fluorine bad -shudder-) and thus is rare to find in concentrations without something -else- creating a surplus.
However, considering the immensity of the universe, they and @Chronos are absolutely correct that there could be some abiotic process that would result in a surplus of free oxygen observable in the atmosphere.
Sadly, since we have no vaguely plausible methods to travel at any substantial fraction of c, or FTL, it’s going to be a ‘gee golly wiz, I bet there’s life there, sadly it’ll take 400 years to get a probe there, and another 400 at best before we get any confirmation’.
I hate physics (don’t tell my wife the soon-to-be Physics PhD).
Just wait until they find a planet with a molecular fluorine atmosphere.
We may be able to detect life without travelling there using the recently launched James Webb Space Telescope (JWST).
The JWST, as it is called, may be able to look for signs of alien life - detecting whether atmospheres of planets orbiting nearby stars are being modified by that life.
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The basis for this search may lie in JWST being so sensitive to light that it could pick up so-called “atmospheric chemical disequilibrium”.
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Because of this, searching for signs of oxygen (or its chemical cousin ozone) has long been thought to be a good way of finding life. But this does rest on the assumption that extraterrestrial life runs by the same biological rules as our own.
It might not. Therefore, assessing atmospheric chemical disequilibrium - looking for other gases and figuring out how far out of kilter from "normal’ a planet’s atmosphere sits - could be key to finding alien life of any kind. SOURCE
“How to say you haven’t read the OP without saying that you haven’t read the OP.”
One of the more interesting ways that a planet could have a thick oxygen-rich atmosphere is through the existence of a deep water ocean, with an even deeper high-pressure water-ice mantle underneath. This would mean a very high water vapour content in the atmosphere, which could be split via photolysis into oxygen and hydrogen. If the escape velocity allows the hydrogen to escape, that could increase the oxygen content to detectable levels and this oxygen might persist longer than on Earth because it could not easily penetrate the ice mantle.
Waterworlds of this kind may be far more numerous than Earth-like planets with life (if we are particularly unlucky), so the detection of oxygen may be a false positive in the majority of cases.
This was what prompted my question. Not really my area of expertise, but it seems to me if we find an oxygen atmosphere there must be recharging agent. Not that that has to be life.
I got distracted and forgot. Ah well…the article is still interesting.
Not directly related to the OP but of interest, I think, is people dying who go into a chain locker on a ship if they do not wear breathing apparatus (it has happened). The oxygen in the locker is captured by the metal as it rusts until no oxygen is left.
It shows how easily oxygen can be removed if nothing replenishes it.
(Not to de-rail my own thread but…) How does that happen. I guess what I asking is, wouldn’t you be able sense something is wrong and leave? They don’t seem to be that big of a place.
First thing to go in a low-oxygen situation is your ability to think. That prevents you from realizing your danger.
It’s due to our biology. Our “needs to breath” sense is based on a surplus of CO2, not a lack of O2. In the critical moments, your oxygen level drops before your carbon-dioxide level rises. And lowered oxygen means you’re not producing as much carbon dioxide, reducing your instinct to breath, which creates a death spiral.
And your hampered brain function prevents you from figuring it out.
The guidelines about securing your own oxygen supply first before helping others on an aircraft is more important than many people realize.
Interesting. Thanks.
There’s practically a cottage industry of people thinking of ways that potential biomarkers might be spoofed by non biological mechanisms. Even high concentrations of molecular oxygen have had proposed abiogenic origins. Even when referring to microbes, the phrase “aliens are literally the last hypothesis” seems to be the rule.
You could say that the presence of free oxygen is a good marker for entropy running backwards. Something needs to be fighting it’s natural tendency to reach for lower energy states.
Life as we know it pretty much demands that it is using some energy source to locally reverse entropy. So it isn’t a huge jump to put some form life on the list of reasons for other apparent local entropy violations. But is certainly isn’t the only one. Stars are good energy sources and can supply all manner of energy quanta, solar winds, and so on. Plenty of grist for the mill for coming up with abiotic processes.
Nor is an excess of oxygen an absolute marker for a local entropy reversing process. It might be an artefact of something weird in the primordial genesis of the planet. There might not be enough stuff around for it to oxidise. Unlikely but I’m sure someone has worked out a way it could happen. The ice/water planet above is a start on the ways.
You may be interested in reading accounts from people who have climbed Mt. Everest. The upper part of the mountain is an interesting place, insomuch that it’s sufficiently low on oxygen to muddle the thinking, but not so low as to be immediately deadly. Several people have published first-hand accounts of what happens.
Not just rust but paint also oxidizes enough to deplete the O2. In the navy it’s SOP before entering a void space that’s been closed up for a while to either ventilate it with fans or wear an OBA if time is pressing.
For a less extreme version of the phenomenon: The top of Mauna Kea is the best spot on the planet for watching the skies, which is of course why there’s an observatory there. Some astronomer colleagues of mine who’ve done work there have, during breaks in their work, stepped outside to take in the view of the night sky with their naked eye… and reported that it only looked about as impressive as the sky from a light-polluted city. Until, at least, they took a hit from a supplemental oxygen bottle, and the heavens opened up to the most spectacular thing they’ve ever seen. Apparently, one of the first effects of low oxygen is a decrease in visual sensitivity, so you can’t see any but the brightest stars.