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Alright, so there are traces of Phosphine in the atmosphere. But what makes the association with life a credible claim? There are a number of possible inorganic

Alright, so there are traces of Phosphine in the atmosphere. But what makes the association with life a credible claim? There are a number of possible inorganic synthesis paths leading to that molecule. How can those be ruled out?

mlnj 6y ago
http://www.sci-news.com/astronomy/phosphine-biosignature-gas-07957.html http://www.sci-news.com/astronomy/phosphine-biosignature-gas... Something along the lines of: > To do this, they spent the last several years running many species of phosphorous — phosphine’s essential building block — through an exhaustive, theoretical analysis of chemical pathways, under increasingly extreme scenarios, to see whether phosphorous could turn into phosphine in any abiotic way. > The scientists found that phosphine has no significant false positives, meaning any detection of phosphine is a sure sign of life.
- PopePompus 6y ago
  Phosphine was detected in Saturn's atmosphere at the Caltech Submillimeter Observatory (right next to the JCMT) decades ago (http://www.ericweisstein.com/research/papers/dps93/ http://www.ericweisstein.com/research/papers/dps93/). I don't recall anyone screaming "Life on Saturn" back then. I think this is being overhyped.
  - ncallaway 6y ago
    From the other thread about this, people were saying there are known abiotic chemical pathways to generate Phosphine on gas giants, so detection of Phosphine on Saturn and Jupiter is much less interesting. Apparently those know pathways don't work on rocky planets, which is why a detection on Venus is more interesting than a detection on Saturn. I still expect the outcome to eventually be: "we have found a new pathway to Phosphine, that's consistent with a rocky planet", but it definitely seems like a discovery that warrants attention and further study.
    - Robotbeat 6y ago
      I have often thought of Venus as halfway between a gas giant and a rocky planet.
      - sedatk 6y ago
        Why?
        Robotbeat 6y ago
        Because like a gas giant, the surface is effectively unreachable or at least absolutely uninhabitable (if it even exists for a gas giant). The atmosphere of Venus, like a gas giant, becomes a very hot, supercritical gas as you go deeper. Like a gas giant, the only potential habitable area is in the atmosphere. Venus still has a sensible surface, although it's unclear if that concept makes sense for a gas giant. "Gas dwarfs" exist, which have a thick atmosphere around a rocky planet (i.e. around Earth's mass), but Venus probably doesn't qualify for that. It's sort of a continuum, though, so the dividing line is somewhat arbitrary.
        saberdancer 6y ago
        In an colonization sense perhaps, but the environment is very different. Pressures while high on Venus are orders of magnitudes lower than in gas giant atmospheres.
        Robotbeat 6y ago
        In a broad, habitability of life standpoint, with human settlement being a subset of that.
        ncallaway 6y ago
        I think looking at it as a continuum makes some amount of sense, though in this case the authors of the paper seem to have done lots of due diligence in terms of doing the chemistry to check known production paths. As in, there is known chemistry that produces phosphine at the temperatures and pressures that exist on Saturn and Jupiter, but there is not known chemistry that produces phosphine at the temperatures and pressures that exist on Venus. So for this particular chemistry, the difference between "gas giant" and "rocky planet" is still a helpful one.
  - danparsonson 6y ago
    The difference is that Saturn is a gas giant - this discovery relates to the detection of phospine on a rocky planet, which is what makes it unexpected and difficult to explain.
  - falseprofit 6y ago
    See Figure 4 of https://iopscience.iop.org/article/10.1086/506245/pdf https://iopscience.iop.org/article/10.1086/506245/pdf "-Overview of phosphorus chemistry as a function of temperature and pressure in a solar system composition gas."
- gmueckl 6y ago
  On a first pass through the paper that you linked, I see a couple of instances where they use parameters that directly match conditions on earth. I don't know how well some aspects about Venus are known (e.g. the exact rates at which trace gases are emitted by volcanic activity on Venus). My personal take on this is that the big claim doesn't seem entirely watertight. And claims like that have been taken apart quite quickly in the past.
tiborsaas 6y ago
"The paper’s main conclusion is that, if phosphine is detected in a nearby, rocky planet, that planet must be harboring life of some kind." https://news.mit.edu/2019/phosphine-aliens-stink-1218 https://news.mit.edu/2019/phosphine-aliens-stink-1218
- V-2 6y ago
  The co-author (Janusz Petkowski) stated: > This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets. > We really went through all possible pathways that could produce phosphine on a rocky planet. If this is not life, then our understanding of rocky planets is severely lacking. So it's a matter of probabilities, not absolute certitudes. My question is, why couldn't our current understanding of rocky planets be lacking? Because "must be harboring life" rules this option out unconditionally.
  - tiborsaas 6y ago
    I know it's probably not satisfying, but they spent 10 years on this research asking this very same question. If the only remaining possibility is biological origin, then we should probably take the risk of ignoring an unknown unknown.
    - V-2 6y ago
      I don't think such approach is fully consistent with scientific methodology. The abstract clearly presents the question as an alternative, not "the only remaining possibility", as you stated: "PH3 could originate from unknown photochemistry or geochemistry, or, by analogy with biological production of PH3 on Earth, from the presence of life" It doesn't strike me as scientific to "ignore an unknown unknown", which would boil down to an assumption that we already know every possible reaction mechanism there is to know. Discovering unknown chemistry would be groundbreaking of course, but the same goes for confirming extraterrestial life.
      - tiborsaas 6y ago
mrmonkeyman 6y ago
MIT and Cardiff painstakingly agonizing over every possible alternative explanation, providing ample and detailed analysis in an extensive research paper, but nope, wait hold the presses. Hackernews is onto something. They thought of something that could derail this whole project! My god, thanks Hackernews. Saved us a lot of trouble.
Tepix 6y ago
Adding to the other answers: Phosphine is highly reactive and will not last long. In other words, something is producing it.
jug 6y ago
Apparently they tried to take this into account but this couldn't explain nearly as much as is discovered in the atmosphere.

mlnj 6y ago

http://www.sci-news.com/astronomy/phosphine-biosignature-gas-07957.html http://www.sci-news.com/astronomy/phosphine-biosignature-gas... Something along the lines of: > To do this, they spent the last several years running many species of phosphorous — phosphine’s essential building block — through an exhaustive, theoretical analysis of chemical pathways, under increasingly extreme scenarios, to see whether phosphorous could turn into phosphine in any abiotic way. > The scientists found that phosphine has no significant false positives, meaning any detection of phosphine is a sure sign of life.

PopePompus 6y ago
Phosphine was detected in Saturn's atmosphere at the Caltech Submillimeter Observatory (right next to the JCMT) decades ago (http://www.ericweisstein.com/research/papers/dps93/ http://www.ericweisstein.com/research/papers/dps93/). I don't recall anyone screaming "Life on Saturn" back then. I think this is being overhyped.
- ncallaway 6y ago
  From the other thread about this, people were saying there are known abiotic chemical pathways to generate Phosphine on gas giants, so detection of Phosphine on Saturn and Jupiter is much less interesting. Apparently those know pathways don't work on rocky planets, which is why a detection on Venus is more interesting than a detection on Saturn. I still expect the outcome to eventually be: "we have found a new pathway to Phosphine, that's consistent with a rocky planet", but it definitely seems like a discovery that warrants attention and further study.
  - Robotbeat 6y ago
    I have often thought of Venus as halfway between a gas giant and a rocky planet.
    - sedatk 6y ago
      Why?
      - Robotbeat 6y ago
        Because like a gas giant, the surface is effectively unreachable or at least absolutely uninhabitable (if it even exists for a gas giant). The atmosphere of Venus, like a gas giant, becomes a very hot, supercritical gas as you go deeper. Like a gas giant, the only potential habitable area is in the atmosphere. Venus still has a sensible surface, although it's unclear if that concept makes sense for a gas giant. "Gas dwarfs" exist, which have a thick atmosphere around a rocky planet (i.e. around Earth's mass), but Venus probably doesn't qualify for that. It's sort of a continuum, though, so the dividing line is somewhat arbitrary.
        saberdancer 6y ago
        In an colonization sense perhaps, but the environment is very different. Pressures while high on Venus are orders of magnitudes lower than in gas giant atmospheres.
        Robotbeat 6y ago
        In a broad, habitability of life standpoint, with human settlement being a subset of that.
        ncallaway 6y ago
        I think looking at it as a continuum makes some amount of sense, though in this case the authors of the paper seem to have done lots of due diligence in terms of doing the chemistry to check known production paths. As in, there is known chemistry that produces phosphine at the temperatures and pressures that exist on Saturn and Jupiter, but there is not known chemistry that produces phosphine at the temperatures and pressures that exist on Venus. So for this particular chemistry, the difference between "gas giant" and "rocky planet" is still a helpful one.
- danparsonson 6y ago
  The difference is that Saturn is a gas giant - this discovery relates to the detection of phospine on a rocky planet, which is what makes it unexpected and difficult to explain.
- falseprofit 6y ago
  See Figure 4 of https://iopscience.iop.org/article/10.1086/506245/pdf https://iopscience.iop.org/article/10.1086/506245/pdf "-Overview of phosphorus chemistry as a function of temperature and pressure in a solar system composition gas."
gmueckl 6y ago
On a first pass through the paper that you linked, I see a couple of instances where they use parameters that directly match conditions on earth. I don't know how well some aspects about Venus are known (e.g. the exact rates at which trace gases are emitted by volcanic activity on Venus). My personal take on this is that the big claim doesn't seem entirely watertight. And claims like that have been taken apart quite quickly in the past.

tiborsaas 6y ago

"The paper’s main conclusion is that, if phosphine is detected in a nearby, rocky planet, that planet must be harboring life of some kind." https://news.mit.edu/2019/phosphine-aliens-stink-1218 https://news.mit.edu/2019/phosphine-aliens-stink-1218

V-2 6y ago
The co-author (Janusz Petkowski) stated: > This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets. > We really went through all possible pathways that could produce phosphine on a rocky planet. If this is not life, then our understanding of rocky planets is severely lacking. So it's a matter of probabilities, not absolute certitudes. My question is, why couldn't our current understanding of rocky planets be lacking? Because "must be harboring life" rules this option out unconditionally.
- tiborsaas 6y ago
  I know it's probably not satisfying, but they spent 10 years on this research asking this very same question. If the only remaining possibility is biological origin, then we should probably take the risk of ignoring an unknown unknown.
  - V-2 6y ago
    I don't think such approach is fully consistent with scientific methodology. The abstract clearly presents the question as an alternative, not "the only remaining possibility", as you stated: "PH3 could originate from unknown photochemistry or geochemistry, or, by analogy with biological production of PH3 on Earth, from the presence of life" It doesn't strike me as scientific to "ignore an unknown unknown", which would boil down to an assumption that we already know every possible reaction mechanism there is to know. Discovering unknown chemistry would be groundbreaking of course, but the same goes for confirming extraterrestial life.
    - tiborsaas 6y ago

mrmonkeyman 6y ago

MIT and Cardiff painstakingly agonizing over every possible alternative explanation, providing ample and detailed analysis in an extensive research paper, but nope, wait hold the presses. Hackernews is onto something. They thought of something that could derail this whole project! My god, thanks Hackernews. Saved us a lot of trouble.

Tepix 6y ago

Adding to the other answers: Phosphine is highly reactive and will not last long. In other words, something is producing it.

jug 6y ago

Apparently they tried to take this into account but this couldn't explain nearly as much as is discovered in the atmosphere.