Astrobiology: Liquid Water Yet No Oxygen?

[Cognitive Dissident]

This question is for anyone who reads about or has studied astrobiology, cosmology, etc., and is familiar with the requirements for so-called "organic life."

Astrobiologists seem to assume that oxygen does not exist on planets that have liquid water but do not have microbes which produce oxygen.  Why is this?  Is it impossible or unlikely that there are other ways oxygen is separated from water?

[slayerboy]

Just an FYI, water is H2O.  2 parts Hydrogen and one part Oxygen.  Without oxygen, you just have hydrogen.  What they're referring to isn't water and cannot scientifically be water without oxygen.  It can be a liquid, but not water.

[Cognitive Dissident]

Actually, I knew what I was talking about but apparently you didn't. A popular claim is that H2O existed on earth in liquid form before gaseous O2 did. They claim gaseous O2 requires a specific microbial process which came later.  Same folks also seem to jump to the conclusion that the same case would present itself anywhere else.

For more information:

One example of where this conjecture is espoused is Discovery Channel's "The Universe," Season 2 episode titled "Astrobiology."  I did see the same assertion recently on another similar presentation.

Added the word "specific," as it better embodies the sentiment in the presentation.

[ForumTroll]

I wonder if there is a natural process which could result in the production of Hydrogen Peroxide, which then decomposes into water and O2.

Maybe electrolysis of water with lightning in salt water? Hmm...

[AOD_Horseman]

I was thinking electrolysis, too, but I don't know terribly well if lightning has the same effect. I also considered a Fluorine decay, but I think F-18 may only be laboratory created. Big shrug on that one.

[Cognitive Dissident]

I was thinking as varied as nature is on this mass (planet), and those which have been explored, that it seems likely there are many ways oxygen would be liberated from liquid water.  Both anaerobic and aerobic respiration in plants cause it, but one requires CO2, if I recall, which they also seem to see as a "requirement" for organic life.

I thought some of the "latest news," that meteorites have been found, dating back some 4.3 billion years, IIRC, have been found with liquid water in them.  Apparently it is now "shown" that meteorites of that approximate age were the source of liquid H20 on this planet, which was apparently molten at the time, and probably helped cool it.  I believe that revelation was in the "other" presentation which I cannot name.

and and -> and
Added additional info...

[YixilTesiphon]

I'm not really sure what you're asking. Certainly it's possible for there to be liquid water without oxygen.

[Cognitive Dissident]

I'm not really sure what you're asking. Certainly it's possible for there to be liquid water without oxygen.

According to what I've been watching, astrobiologists seem to disagree.

[YixilTesiphon]

Unless I'm really reading poorly, this:

Certainly it's possible for there to be liquid water without oxygen.

According to what I've been watching, astrobiologists seem to disagree.

doesn't match this:

Astrobiologists seem to assume that oxygen does not exist on planets that have liquid water but do not have microbes which produce oxygen.  Why is this?  Is it impossible or unlikely that there are other ways oxygen is separated from water?

[Cognitive Dissident]

Unless I'm really reading poorly, this:

Certainly it's possible for there to be liquid water without oxygen.

According to what I've been watching, astrobiologists seem to disagree.

doesn't match this:

Astrobiologists seem to assume that oxygen does not exist on planets that have liquid water but do not have microbes which produce oxygen.  Why is this?  Is it impossible or unlikely that there are other ways oxygen is separated from water?

(this is a redo, I had to delete the original response)

I'm sorry, I misread your response.  I would think it unlikely for liquid water to exist without oxygen--for very long.  Isn't hydrolysis common enough for them to more likely coexist than exist in absence of one another?  The assertion seems to imply that it is not.

[YixilTesiphon]

Unless I'm really reading poorly, this:

Certainly it's possible for there to be liquid water without oxygen.

According to what I've been watching, astrobiologists seem to disagree.

doesn't match this:

Astrobiologists seem to assume that oxygen does not exist on planets that have liquid water but do not have microbes which produce oxygen.  Why is this?  Is it impossible or unlikely that there are other ways oxygen is separated from water?

(this is a redo, I had to delete the original response)

I'm sorry, I misread your response.  I would think it unlikely for liquid water to exist without oxygen--for very long.  Isn't hydrolysis common enough for them to more likely coexist than exist in absence of one another?  The assertion seems to imply that it is not.

Yes, some level of oxygen is likely to exist. However, previously unoxidized rocks such as those on the other planets of our solar system and Earth before large-scale oxygenation of the atmosphere are capable of absorbing a huge amount of oxygen. So, even if there is a constant source of oxygen, all the oxygen produced will be mopped up very quickly for a long time, until so much is produced (for example, photosynthetic organisms spread around the globe) that all surface rocks are oxidized - only then can it build up in the atmosphere.

[Cognitive Dissident]

Unless I'm really reading poorly, this:

Certainly it's possible for there to be liquid water without oxygen.

According to what I've been watching, astrobiologists seem to disagree.

doesn't match this:

Astrobiologists seem to assume that oxygen does not exist on planets that have liquid water but do not have microbes which produce oxygen.  Why is this?  Is it impossible or unlikely that there are other ways oxygen is separated from water?

(this is a redo, I had to delete the original response)

I'm sorry, I misread your response.  I would think it unlikely for liquid water to exist without oxygen--for very long.  Isn't hydrolysis common enough for them to more likely coexist than exist in absence of one another?  The assertion seems to imply that it is not.

Yes, some level of oxygen is likely to exist. However, previously unoxidized rocks such as those on the other planets of our solar system and Earth before large-scale oxygenation of the atmosphere are capable of absorbing a huge amount of oxygen. So, even if there is a constant source of oxygen, all the oxygen produced will be mopped up very quickly for a long time, until so much is produced (for example, photosynthetic organisms spread around the globe) that all surface rocks are oxidized - only then can it build up in the atmosphere.

That's the best explanation I've heard (the only one, actually.)  I had otherwise suspected the inability of the planet (or other body) to hold an atmosphere altogether.

[AOD_Horseman]

That's a very nice answer indeed, thank you.