Vexer Posted August 14, 2012 Report Share Posted August 14, 2012 Was going to put this the Cosmology section, but seemed better here: Bit of a science-fiction question: are there any circumstances in which a completely lifeless planet/moon could sustain enough atmospheric oxygen to support humans? Give it water or ice, or whatever it takes. But no native life of any kind. Quote Link to comment Share on other sites More sharing options...
JMJones0424 Posted August 14, 2012 Report Share Posted August 14, 2012 Water and ice both contain oxygen, but it is bound with hydrogen. Oxygen is highly reactive, second only to fluorine in electronegativity. I don't know of any chemical processes other than life that produce substantial amounts of free oxygen. Quote Link to comment Share on other sites More sharing options...
sman Posted August 14, 2012 Report Share Posted August 14, 2012 Water and ice both contain oxygen, but it is bound with hydrogen. Oxygen is highly reactive, second only to fluorine in electronegativity. I don't know of any chemical processes other than life that produce substantial amounts of free oxygen. So, oxygen means life? Were we to detect free oxygen - by which I think you mean molecular oxygen, O2 - in an extra-solar environment should we assume life there? Can we even do anything like a chemical analysis of an extra-solar planet? Do these things give us enough light for spectroscopy? I've heard that the methane in our own atmosphere - if detected by extra-terrestrials knowing nothing else about earth - would be a definitive indication of the life here. Now, methane constitutes about .000179% of our atmosphere, compared with oxygen at about 20%. Quote Link to comment Share on other sites More sharing options...
JMJones0424 Posted August 15, 2012 Report Share Posted August 15, 2012 So, oxygen means life? Were we to detect free oxygen - by which I think you mean molecular oxygen, O2 - in an extra-solar environment should we assume life there? Can we even do anything like a chemical analysis of an extra-solar planet? Do these things give us enough light for spectroscopy? I've heard that the methane in our own atmosphere - if detected by extra-terrestrials knowing nothing else about earth - would be a definitive indication of the life here. Now, methane constitutes about .000179% of our atmosphere, compared with oxygen at about 20%. I don't know. Methane occurs naturally in the solar system without needing life to generate it. O2 is a different story. sman and Moontanman 2 Quote Link to comment Share on other sites More sharing options...
sman Posted August 15, 2012 Report Share Posted August 15, 2012 I don't know. Methane occurs naturally in the solar system without needing life to generate it. O2 is a different story. Well, I can’t remember where I read about the methane, but I was obviously confused, thanks. On extra-terrestrial oxygen I can find very little. Evidently, the standard method for identifying possible life on exo-planets is by comparing their spectra (so yes, apparently we can collect enough light to do this) with that of earth. But I did find one article in which the authors argue that this method will produce false negatives - that any “high simultaneous concentrations of O2, O3, CH4 and N2O” indicate photosynthesis, even if the planet isn’t green. In corollary I think this agrees with you and answers the OP squarely: Lifeless, virgin planets will not be teeming with free oxygen for us to breath. Moontanman 1 Quote Link to comment Share on other sites More sharing options...
Vexer Posted August 18, 2012 Author Report Share Posted August 18, 2012 Thanks for the replies, good people. Quote Link to comment Share on other sites More sharing options...
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