Hello, friends!

Over the last decade or so, Mars has been trying really hard to convince us that he can (and does) support life.  We’ve seen evidence of liquid water on the Martian surface, and traces of methane have been detected in the Martian atmosphere.  These things are highly suggestive, but none of that proves Martian life exists.

It would be nice if we knew of a chemical that clearly and unambiguously proved that a planet has life, wouldn’t it?  According to this paper published in Nature Astronomy, phosphine (chemical formula PH3) might be the clear and unambiguous biosignature we need.  Here on Earth, phosphine gas is a waste product produced by certain species of anaerobic bacteria.  It’s also produced by humans in our factories.  Either way, the presence of phosphine in Earth’s atmosphere is strong evidence that there’s life on Earth.

And according to that same paper from Nature Astronomy, astronomers have now detected phosphine on another planet.  No, it wasn’t Mars.

Okay, we humans do know of non-biological ways to make phosphine, but they’d require Venus to be a very, very different planet than she currently is.  For example, Venus would need to have a hydrogen-rich atmosphere, or Venus would have to be bombarded constantly with phosphorus-rich asteroids, or the Venusian surface would have to be covered with active volcanoes (more specifically, Venus would need at least 200 times more volcanic activity than Earth).

None of that appears to be true for Venus, so we’re left with two possibilities:

  • There is life on Venus.
  • There’s something we humans don’t know about phosphine, in which case phosphine is not the clear and unambiguous biosignature we hoped it was.

In either event, Venus is about to teach us something.  Maybe it’s a biology lesson.  That would be awesome!  Or maybe it’s a chemistry lesson.  Personally, I’m expecting it to be a chemistry lesson.  There must be some other way to make phosphine that we humans never thought of.

P.S.: Now I’m sure a lot of you are thinking: “Wait a minute, don’t Jupiter and Saturn have phosphine in their atmospheres too?”  You’re right.  They do, and we’ll talk about that in Wednesday’s post.

14 responses »

  1. Kate Rauner says:

    We may all have a touch of phosphine fever right now.

    Liked by 3 people

  2. Spacerguy says:

    Phosphine every day helps you work rest and play! We’re lucky we have what we need on earth because so far no visitors and maybe thats a good thing.

    Liked by 3 people

  3. Emily Faith says:

    This is really cool!

    Also, I love your little cartoons. They’re so cute!

    Liked by 2 people

  4. I thought Venus was known to have a lot of volcanism. Although maybe not 200 times what Earth has, and maybe not as recent as it’d need to be for what we’re detecting.

    Liked by 2 people

    • J.S. Pailly says:

      That was the first bit of fact checking I did after reading that Nature Astronomy paper, because I thought we had recently discovered Venus does have active volcanos. Apparently that’s not confirmed yet, and even if it were, it sounds like it’s a very small number of volcanos.

      Venus’s surface is surprisingly smooth, which means it must have been paved over (so to speak) with fresh lava fairly recently. But that’s recently in geological terms. Something would have to keep producing phosphine on a daily basis to explain the amount of phosphine in Venus’s atmosphere.

      Liked by 2 people

      • Thanks. That’s what I suspected.

        That said, sometime after I made this comment, I came across a tweet to this paper.
        https://arxiv.org/abs/2009.11904

        We propose an abiotic geological mechanism that accounts for the abundance of phosphine detected by Greaves et al., 2020. We hypothesize that trace amounts of phosphides formed in the mantle would be brought to the surface by volcanism, and then subsequently ejected into the atmosphere, where they could react with water or sulfuric acid to form phosphine. To investigate the plausibility of this hypothesis, we carry out an order of magnitude calculation. We suggest that active volcanism today could produce a rate comparable to that required to produce the phosphide-source of the phosphine. Our hypothesis requires that Venus be currently experiencing a high rate of basaltic volcanism, one that is consistent with spacecraft observations and laboratory experiments.

        I’m not versed enough in planetary science to evaluate it. And it’s a hypothesis in a preprint, so caution is warranted.

        Liked by 2 people

      • J.S. Pailly says:

        I just skimmed through the paper you sighted. I’ll read it more thoroughly later. My first impression is that it sounds like a plausible enough hypothesis, but I wish there were harder evidence of active volcanos.

        On the other hand, if possible life and possible volcanos end up being the only available explanations, I think Occam’s razor would tell us to go with the volcanos.

        Liked by 3 people

  5. Simon says:

    I think this will be a chemistry lesson too – but either way we need to understand it.

    Liked by 2 people

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