7 ms·

Billion-year-old air reveals surprise about oxygen on ancient Earth

207 points by miraj 10y ago

IanDrake 10y ago
Here's what worries me about this type of extrapolation: "The researchers also compared salt samples from other halite deposits of different ages — including the modern day — when oxygen concentrations were known and found their results matched up with known concentrations. That gave them confidence in their result, they said." OK, so you take a recent sample and it matches up. Great. But this seems to assume there is some sort of barrier at the atomic level that "traps" the atmosphere at the time the salt crystals were formed and that time and pressure will never have an impact on what components of the atmosphere remain in the salt crystal.
- phaemon 10y ago
  I suppose that's the kind of question Prof Blamey might have considered when he was a first year student back around 1975. He probably knows what he's doing by now though.
  - IanDrake 10y ago
    Well if he knows what he's doing, who am I to question any unexplained assumptions made in the article.
    - lorenzhs 10y ago
      In "Random Guy from the Internet -vs- Professor on the Subject", you can't really blame anyone for giving the scientists the benefit of the doubt. The paper is open access, btw, maybe they addressed your question or provided a citation? You can read it at http://geology.gsapubs.org/content/early/2016/07/08/G37937.1.full.pdf http://geology.gsapubs.org/content/early/2016/07/08/G37937.1...
      - IanDrake 10y ago
        I'm surprised (but not really) at the amount of resistance to to questioning these results, when at the very least you have to agree with the following: This method AND the prior method can't BOTH be right. That means at least one of them is WRONG. Had I questioned the prior method's claims and techniques yesterday I would have had the same response from the same people. Science (to some) is still about questioning everything. It scares me how many people on HN have lost sight of that.
        reitanqild 10y ago
        Smile and upvote from me on this.
        mikeash 10y ago
        Being right for the wrong reasons doesn't win you any points. If you had questioned the prior method's claims and techniques yesterday based on this same sort of "what about this obvious problem?" then you would have had the same response and deservedly so. If I declare that the Earth is round because I drew a circle on a piece of paper, I can't wave away criticism of my method just because the result is correct.
        IanDrake 10y ago
        No, I'm right for the right reason. All extrapolations of this type are difficult to prove out. They are based on a lot of assumptions. Those assumptions may not all be right and some critical components might be missing. The model being used to compute slippage over time might be overfit to the parameters. If I declared the world to be flat then proved it by going to a truly flat field to provide parameters to a mathematical model that showed I was correct, it wouldn't make me correct no matter how convincing my credentials or my paper.
        mikeash 10y ago
        You have no idea if you're right or if this conclusion is actually correct. If the conclusion is wrong, you have no idea if it's wrong because of the problem you posted, or if it's wrong because of something completely different. Virtually all science is wrong in some respect. You can get a great batting average by just saying "no, wrong" to everything you see. That doesn't make it useful, nor does it make your reasons for saying "wrong" correct.
    - bsder 10y ago
      First, you need to go read the actual paper, rather than some journalistic paraphrase, and them come back. After that, you can ask a specific question about what was done and what was not done. Generally with an eye toward a useful mechanism that might explain things. Then, you need to come up with a prediction based upon that question that can be tested. At that point, you are contributing to the discussion. "Could invisible sky fairies could have contaminated the results?" is not a useful question. "Is it possible that nuclear decay could have transmuted something into oxygen trapped in NaCl? (answer, no, for various reasons)" is at least in the vein of a useful question.
  - pbhjpbhj 10y ago
    Oh great an appeal to authority that'll set it right. /s If what you say is correct then there's most likely a paper that's been widely cited and remains unfalsified that shows there aren't any changes in the ratios of gases in these crystal interstices (or the changes are well known and quantifiable). Such a citation would be a suitable rebuff.
    - mikeash 10y ago
      IMO an appeal to authority is a perfectly reasonable response to an assumption of incompetence. It's tiresome to always see comments assuming that such-and-such science is flawed because a mainstream news article doesn't spell out every single detail. If it were phrased more neutrally, like "I'm amazed that this stuff can be contained without any contamination for hundreds of millions of years, how do they know that it works that way?" I wouldn't have a problem with it. Start assuming that you've missed something, not the scientist who does this for a living. Maybe the scientist has missed something, they're certainly not perfect, but to me it's ridiculous and counterproductive to be "worried" about the results of years of professional work based on one popular article and five minutes of thought (if that).
      - jdmichal 10y ago
        If your complaint is not the message, but rather the phrasing, then I'd say that you're not being very charitable.
        mikeash 10y ago
        It's both. The phrasing contains a message of "these scientists didn't consider this obvious problem."
        jdmichal 10y ago
        That's fair. To the point, this person [0] doesn't seem to be having any issues with downvotes, even though the comment raises the same basic issue -- the reliability of the crystalline entrapment. [0] https://news.ycombinator.com/item?id=12186872 https://news.ycombinator.com/item?id=12186872
- zdkl 10y ago
  I don't know who downvotes this because parent does have a point: there are extensive chemical transfers involved in the creation of minerals and crystals, it's not obvious at all that the atmospheric bubbles where chemically isolated from the encasing crystal afaict
  - akamaka 10y ago
    I don't even need to read the article or paper to see that the commenter didn't think through what he was saying. He specifically uses a quote that says "different ages - including the modern day" were used, but then suggests that the researches only used one "recent" sample.
  - maxerickson 10y ago
    I didn't down vote the above comment, but when the paper is available, complaints should usually be about something specific in the paper, not hand wavy concerns about methodology. http://geology.gsapubs.org/content/early/2016/07/08/G37937.1.full.pdf http://geology.gsapubs.org/content/early/2016/07/08/G37937.1... The paper discusses the type of crystal they studied and how they formed (and cites further work on those topics).
- chris_va 10y ago
  Not a bad question, and they attempt to address it in the paper with their multi-sample calibration: It is highly unlikely that oxygen could have been injected into halite inclusions without evidence of morphochemical disruption, and we must conclude that Cretaceous atmospheric oxygen was most likely higher than present-day levels. The tests performed on the modern, Messinian, and Cretaceous halites support halite’s robustness as an atmospheric oxygen archive.
TimGremalm 10y ago
"What they found may have implications for the origin of complex life. The air, which has been preserved, undisturbed, in tiny pockets in the crystals for about 815 million years, appears to contain 10.9 per cent oxygen — just half the amount in the atmosphere today. But it's about five times more than scientists expected for that time period, which is about 200 million years before the first known multicellular fossils."
- Udo 10y ago
  > 200 million years before the first known multicellular fossils This is a weird angle for the article to pursue. We have a monocellular fossil record that dates back 4.1 billion years, and I don't think anyone is proposing that we assumed up to this point oxygen levels took off because of multicellular life. A high oxygen level is probably one of many prerequisites for complex life, but that doesn't mean the genetic machinery was available as soon as it reached a certain concentration.
  - omarchowdhury 10y ago
    Wouldn't oxygen producing organisms such as plants and trees be a cause for oxygen levels taking off?
    - Udo 10y ago
      They're certainly sufficient but not necessary. There's no reason why single celled organisms couldn't do that. Maybe not at 20% but close.
    - adrianratnapala 10y ago
      I thought even today phytoplankton produced more oxygen than all the multicellular plants put together. I might just be imagining that factoid though.
      - HCIdivision17 10y ago
        That was my understanding as well. The idea being that there is a lot of volume in the first few meters of ocean surface area churn. It's not hard to imagine that does better in surface area than (even a lot) of plants.
keithwhor 10y ago
Would be interesting to hear a discussion about how this impacts the timeline of the Great Oxygenation Event [1], and where there's conflict with what's proposed. If there's somebody a little more familiar with the geological evidence it would be great to know a little more. [1] https://en.m.wikipedia.org/wiki/Great_Oxygenation_Event https://en.m.wikipedia.org/wiki/Great_Oxygenation_Event
- peter303 10y ago
  You are talking about seperated events, one 800 MY and other 2400 MY.
- peter303 10y ago
  You are talking about seperated events, one 800 MY and other 2400 MY.
rebelde 10y ago
I see articles like this one every once in a while. A chemistry professor once told my class that due to the rate of diffusion, that we had just learned, the test of the "old air" would be wrong. I don't know chemistry well. My question is if the salt completely stopped all diffusion over the last billion years. Maybe somebody here can answer.
- deleted 10y ago
  [deleted]
- bduerst 10y ago
  If I remember correctly, NaCl atoms are packed pretty closely together in crystallized form. They seem to be only looking at large crystalline structures, which do not have evidence of disruption. Of course, they also said they used the same method with modern salt, and the O2 levels were lower than atmosphere by 9.2% for one of those samples. It seems fairly legit but it would be great if they could test salt from the same period but from a different mine.
smcg 10y ago
So... how did it smell?
- philbarr 10y ago
  It couldn't. It had no nose...
misiti3780 10y ago
Does this affect any of the conclusions in Nick Lane's books (for anyone here that has read them)? (It seems like it doesnt to me)
known 10y ago
Earth is ~4 billion years old
- deleted 10y ago
  [deleted]
Zenst 10y ago
Nice to measure it but wasn't there already proof of larger amounts of oxygen in the past and the earliest life (one of from what we know) was a bacteria that produced the first oxygen in abundance and explains the higher levels and is indeed thought why, or least factor in why early mammals were larger and during the dinosaur days (sorry but easier to call it that for many) the oxygen levels were higher than today by far. Nice article to matchup with this http://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/ http://www.scientificamerican.com/article/timeline-of-photos...
- smhenderson 10y ago
  Well this is talking about 200,000 years before the explosive emergence of life on Earth. Before this discovery it was thought that there was much less oxygen at that time (the Neoproterozoic era according to the article). And that life had to wait until more oxygen came along before it could happen. Now they are basically saying the oldest fossils we have found are probably not the oldest we could find. Time to look for older signs of life!
  - _kst_ 10y ago
    I think you mean 200 million, not 200 thousand.
  - mirimir 10y ago
    There were lots of anaerobic bacteria, however. And photosynthetic ones produced the oxygen. What oxygen enabled was evolution of complex multicellular life.
adamkruszewski 10y ago
But how do we know that those crystals were formed during "normal" conditions? ie. why is it valid to interpolate the air structure for the whole "ancient Earth"? I'm just curious how is it done?
northisup 10y ago
Click bait headline.
dghughes 10y ago
What I find so interesting is why is the oxygen on Earth 21% why not 5%. I can understand why not 90% since it's so reactive but 21% seems so high. Even more so now in modern times with seven billion people and billions of other animals plus industrialization I'd expect atmospheric oxygen to be falling rapidly. We humans are pretty lucky to be able to breath, thank you ocean algae! Honorable mention to trees, good job.
- dmd 10y ago
  Just to give some scale here: A human uses about 0.84 kilograms O2 per day. There is about 5e18 kg O2 in the atmosphere. Excluding all other sources of O2 consumption and replenishment, it would take about 500000 years for the current population of humans to "use up" all the current O2.
pvaldes 10y ago
Dissolved oxygen in water decrease when temperature and salts increase. Sea water have two hydrogen by each oxygen, and contains also atoms of sodium, chloride, magnesium, sulphur, among other. Therefore, saltwater will not have a 21% of oxygen normally, and a 10% of oxygen in salt should not be translated as: "wow, in that time there was only the half of the current oxygen in the air, how animals could live?". Aquatic organisms are adapted to the normal rate of between 6 and 12 mg of dissolved oxygen for each L of saltwater. On the other side, if saltwater becoming brine releases gradually its oxygen, maybe the oxygen in an unknow mass X of water, could be trapped and slowly accumulate in a bubble under tons of silt.

207 points by miraj 10y ago

Here's what worries me about this type of extrapolation: "The researchers also compared salt samples from other halite deposits of different ages — including the modern day — when oxygen concentrations were known and found their results matched up with known concentrations. That gave them confidence in their result, they said." OK, so you take a recent sample and it matches up. Great. But this seems to assume there is some sort of barrier at the atomic level that "traps" the atmosphere at the time the salt crystals were formed and that time and pressure will never have an impact on what components of the atmosphere remain in the salt crystal.

phaemon 10y ago
I suppose that's the kind of question Prof Blamey might have considered when he was a first year student back around 1975. He probably knows what he's doing by now though.
- IanDrake 10y ago
  Well if he knows what he's doing, who am I to question any unexplained assumptions made in the article.
  - lorenzhs 10y ago
    In "Random Guy from the Internet -vs- Professor on the Subject", you can't really blame anyone for giving the scientists the benefit of the doubt. The paper is open access, btw, maybe they addressed your question or provided a citation? You can read it at http://geology.gsapubs.org/content/early/2016/07/08/G37937.1.full.pdf http://geology.gsapubs.org/content/early/2016/07/08/G37937.1...
    - IanDrake 10y ago
      I'm surprised (but not really) at the amount of resistance to to questioning these results, when at the very least you have to agree with the following: This method AND the prior method can't BOTH be right. That means at least one of them is WRONG. Had I questioned the prior method's claims and techniques yesterday I would have had the same response from the same people. Science (to some) is still about questioning everything. It scares me how many people on HN have lost sight of that.
      - reitanqild 10y ago
        Smile and upvote from me on this.
      - mikeash 10y ago
        Being right for the wrong reasons doesn't win you any points. If you had questioned the prior method's claims and techniques yesterday based on this same sort of "what about this obvious problem?" then you would have had the same response and deservedly so. If I declare that the Earth is round because I drew a circle on a piece of paper, I can't wave away criticism of my method just because the result is correct.
        IanDrake 10y ago
        No, I'm right for the right reason. All extrapolations of this type are difficult to prove out. They are based on a lot of assumptions. Those assumptions may not all be right and some critical components might be missing. The model being used to compute slippage over time might be overfit to the parameters. If I declared the world to be flat then proved it by going to a truly flat field to provide parameters to a mathematical model that showed I was correct, it wouldn't make me correct no matter how convincing my credentials or my paper.
        mikeash 10y ago
        You have no idea if you're right or if this conclusion is actually correct. If the conclusion is wrong, you have no idea if it's wrong because of the problem you posted, or if it's wrong because of something completely different. Virtually all science is wrong in some respect. You can get a great batting average by just saying "no, wrong" to everything you see. That doesn't make it useful, nor does it make your reasons for saying "wrong" correct.
  - bsder 10y ago
    First, you need to go read the actual paper, rather than some journalistic paraphrase, and them come back. After that, you can ask a specific question about what was done and what was not done. Generally with an eye toward a useful mechanism that might explain things. Then, you need to come up with a prediction based upon that question that can be tested. At that point, you are contributing to the discussion. "Could invisible sky fairies could have contaminated the results?" is not a useful question. "Is it possible that nuclear decay could have transmuted something into oxygen trapped in NaCl? (answer, no, for various reasons)" is at least in the vein of a useful question.
- pbhjpbhj 10y ago
  Oh great an appeal to authority that'll set it right. /s If what you say is correct then there's most likely a paper that's been widely cited and remains unfalsified that shows there aren't any changes in the ratios of gases in these crystal interstices (or the changes are well known and quantifiable). Such a citation would be a suitable rebuff.
  - mikeash 10y ago
    IMO an appeal to authority is a perfectly reasonable response to an assumption of incompetence. It's tiresome to always see comments assuming that such-and-such science is flawed because a mainstream news article doesn't spell out every single detail. If it were phrased more neutrally, like "I'm amazed that this stuff can be contained without any contamination for hundreds of millions of years, how do they know that it works that way?" I wouldn't have a problem with it. Start assuming that you've missed something, not the scientist who does this for a living. Maybe the scientist has missed something, they're certainly not perfect, but to me it's ridiculous and counterproductive to be "worried" about the results of years of professional work based on one popular article and five minutes of thought (if that).
    - jdmichal 10y ago
      If your complaint is not the message, but rather the phrasing, then I'd say that you're not being very charitable.
      - mikeash 10y ago
        It's both. The phrasing contains a message of "these scientists didn't consider this obvious problem."
        jdmichal 10y ago
        That's fair. To the point, this person [0] doesn't seem to be having any issues with downvotes, even though the comment raises the same basic issue -- the reliability of the crystalline entrapment. [0] https://news.ycombinator.com/item?id=12186872 https://news.ycombinator.com/item?id=12186872
zdkl 10y ago
I don't know who downvotes this because parent does have a point: there are extensive chemical transfers involved in the creation of minerals and crystals, it's not obvious at all that the atmospheric bubbles where chemically isolated from the encasing crystal afaict
- akamaka 10y ago
  I don't even need to read the article or paper to see that the commenter didn't think through what he was saying. He specifically uses a quote that says "different ages - including the modern day" were used, but then suggests that the researches only used one "recent" sample.
- maxerickson 10y ago
  I didn't down vote the above comment, but when the paper is available, complaints should usually be about something specific in the paper, not hand wavy concerns about methodology. http://geology.gsapubs.org/content/early/2016/07/08/G37937.1.full.pdf http://geology.gsapubs.org/content/early/2016/07/08/G37937.1... The paper discusses the type of crystal they studied and how they formed (and cites further work on those topics).
chris_va 10y ago
Not a bad question, and they attempt to address it in the paper with their multi-sample calibration: It is highly unlikely that oxygen could have been injected into halite inclusions without evidence of morphochemical disruption, and we must conclude that Cretaceous atmospheric oxygen was most likely higher than present-day levels. The tests performed on the modern, Messinian, and Cretaceous halites support halite’s robustness as an atmospheric oxygen archive.

TimGremalm 10y ago

"What they found may have implications for the origin of complex life. The air, which has been preserved, undisturbed, in tiny pockets in the crystals for about 815 million years, appears to contain 10.9 per cent oxygen — just half the amount in the atmosphere today. But it's about five times more than scientists expected for that time period, which is about 200 million years before the first known multicellular fossils."

Udo 10y ago
> 200 million years before the first known multicellular fossils This is a weird angle for the article to pursue. We have a monocellular fossil record that dates back 4.1 billion years, and I don't think anyone is proposing that we assumed up to this point oxygen levels took off because of multicellular life. A high oxygen level is probably one of many prerequisites for complex life, but that doesn't mean the genetic machinery was available as soon as it reached a certain concentration.
- omarchowdhury 10y ago
  Wouldn't oxygen producing organisms such as plants and trees be a cause for oxygen levels taking off?
  - Udo 10y ago
    They're certainly sufficient but not necessary. There's no reason why single celled organisms couldn't do that. Maybe not at 20% but close.
  - adrianratnapala 10y ago
    I thought even today phytoplankton produced more oxygen than all the multicellular plants put together. I might just be imagining that factoid though.
    - HCIdivision17 10y ago
      That was my understanding as well. The idea being that there is a lot of volume in the first few meters of ocean surface area churn. It's not hard to imagine that does better in surface area than (even a lot) of plants.

keithwhor 10y ago

Would be interesting to hear a discussion about how this impacts the timeline of the Great Oxygenation Event [1], and where there's conflict with what's proposed. If there's somebody a little more familiar with the geological evidence it would be great to know a little more. [1] https://en.m.wikipedia.org/wiki/Great_Oxygenation_Event https://en.m.wikipedia.org/wiki/Great_Oxygenation_Event

peter303 10y ago
You are talking about seperated events, one 800 MY and other 2400 MY.
peter303 10y ago
You are talking about seperated events, one 800 MY and other 2400 MY.

rebelde 10y ago

I see articles like this one every once in a while. A chemistry professor once told my class that due to the rate of diffusion, that we had just learned, the test of the "old air" would be wrong. I don't know chemistry well. My question is if the salt completely stopped all diffusion over the last billion years. Maybe somebody here can answer.

deleted 10y ago
[deleted]
bduerst 10y ago
If I remember correctly, NaCl atoms are packed pretty closely together in crystallized form. They seem to be only looking at large crystalline structures, which do not have evidence of disruption. Of course, they also said they used the same method with modern salt, and the O2 levels were lower than atmosphere by 9.2% for one of those samples. It seems fairly legit but it would be great if they could test salt from the same period but from a different mine.

smcg 10y ago

So... how did it smell?

philbarr 10y ago
It couldn't. It had no nose...

misiti3780 10y ago

Does this affect any of the conclusions in Nick Lane's books (for anyone here that has read them)? (It seems like it doesnt to me)

known 10y ago

Earth is ~4 billion years old

deleted 10y ago
[deleted]

Zenst 10y ago

Nice to measure it but wasn't there already proof of larger amounts of oxygen in the past and the earliest life (one of from what we know) was a bacteria that produced the first oxygen in abundance and explains the higher levels and is indeed thought why, or least factor in why early mammals were larger and during the dinosaur days (sorry but easier to call it that for many) the oxygen levels were higher than today by far. Nice article to matchup with this http://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/ http://www.scientificamerican.com/article/timeline-of-photos...

smhenderson 10y ago
Well this is talking about 200,000 years before the explosive emergence of life on Earth. Before this discovery it was thought that there was much less oxygen at that time (the Neoproterozoic era according to the article). And that life had to wait until more oxygen came along before it could happen. Now they are basically saying the oldest fossils we have found are probably not the oldest we could find. Time to look for older signs of life!
- _kst_ 10y ago
  I think you mean 200 million, not 200 thousand.
- mirimir 10y ago
  There were lots of anaerobic bacteria, however. And photosynthetic ones produced the oxygen. What oxygen enabled was evolution of complex multicellular life.

adamkruszewski 10y ago

But how do we know that those crystals were formed during "normal" conditions? ie. why is it valid to interpolate the air structure for the whole "ancient Earth"? I'm just curious how is it done?

northisup 10y ago

Click bait headline.

dghughes 10y ago

What I find so interesting is why is the oxygen on Earth 21% why not 5%. I can understand why not 90% since it's so reactive but 21% seems so high. Even more so now in modern times with seven billion people and billions of other animals plus industrialization I'd expect atmospheric oxygen to be falling rapidly. We humans are pretty lucky to be able to breath, thank you ocean algae! Honorable mention to trees, good job.

dmd 10y ago
Just to give some scale here: A human uses about 0.84 kilograms O2 per day. There is about 5e18 kg O2 in the atmosphere. Excluding all other sources of O2 consumption and replenishment, it would take about 500000 years for the current population of humans to "use up" all the current O2.

pvaldes 10y ago

Dissolved oxygen in water decrease when temperature and salts increase. Sea water have two hydrogen by each oxygen, and contains also atoms of sodium, chloride, magnesium, sulphur, among other. Therefore, saltwater will not have a 21% of oxygen normally, and a 10% of oxygen in salt should not be translated as: "wow, in that time there was only the half of the current oxygen in the air, how animals could live?". Aquatic organisms are adapted to the normal rate of between 6 and 12 mg of dissolved oxygen for each L of saltwater. On the other side, if saltwater becoming brine releases gradually its oxygen, maybe the oxygen in an unknow mass X of water, could be trapped and slowly accumulate in a bubble under tons of silt.