Phosphine found in Venus clouds leads to more questions

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Today has one story and only one story. But it is the kind of story where I want all of you to look around and put into your mind where you are right now because this may be the first day we really admit that there could be life elsewhere in our solar system.

Today, a peer-reviewed paper was published in the journal Nature Astronomy announcing that a molecule considered to be biosignature for life has been found in the atmosphere of Venus. This molecule, phosphine (PH3) has no known, naturally occurring sources capable of creating the amount of phosphine that is being seen other than anaerobic life. The implication is that there is chemical evidence of life within the atmosphere of Venus. Such a finding had previously been theorized down to the prediction of phosphine. Observational confirmation of these theories comes from both the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Clerk Maxwell Telescope. Jane Greaves is the lead author of this work.

Since the 1990s, NASA and other funding agencies have supported researchers who are trying to define the observable signatures of life in all its stages. From chemical imbalances in an atmosphere to technological signatures such as infrared excess, researchers have put out paper after paper stating, “If you see these things, life has probably found a way.”

Phosphine is a chemical that, on Earth, can be created through industrial processes, but naturally occurs only as a byproduct of anaerobic life – life that thrives without oxygen. It is created through the breakdown of organic materials. It’s thought that phosphine in modest amounts will be detectable out to an order of ten lightyears. That will allow life in the atmospheres of warm, gassy planets to potentially be detectable using the James Webb Space Telescope. While this observation will be challenging, taking up to ten hours or more of telescope time, it is doable.

Here’s the thing: phosphine requires an atmosphere, but it doesn’t require an atmosphere in another solar system. So while people have been figuring out that phosphine can be used to find life in other solar systems, other researchers, including Planetary Science Institute’s own David Grinspoon, Massachusetts Institute of Technology’s Clara Sousa-Silva and Sara Seager, and NASA’s David J. Smith, have all been part of research looking at the possibility of phosphine being produced by life existing in the atmosphere of Venus. 

In recent months, we’ve seen paper after paper and popular article after popular article on the topic of possible life in Venus’s atmosphere. That said, I have to admit that I haven’t read any of those articles because I, for one, was in the “there is one place there can’t be life, and that is Venus” camp. It appears I lack creativity in my own thinking. This means I’m playing a whole lot of catch up on the science behind this story.

These papers all made careful predictions based on some simple facts: Venus has a mean surface temperature of 737 K (464°C; 867°F). At an altitude of 47.5-50.5 kilometers, those spacecraft-melting temperatures drop, so that at that higher altitude, the temperature is just 60°C and the pressure is one atmosphere, the same pressure that we have here at sea level on Earth. 

At lower levels down in the atmosphere, things ramp up. They get worse, but that mid-altitude temperate region allows us to begin to imagine a potential cycle where life (microbes) has the ability to billow up through gravity waves – waves in the atmosphere of Venus. And then, as they rise, they seed moisture around them. As the amount of moisture grows, within this moisture, life can do life things until eventually, the droplet gets too big to be supported by the air, and gravity begins to pull it down.

Now the way this gets imagined is you have, down at the lowest levels around 33 kilometers, a temperature that is capable of desiccating any life that gets down there. At this lower point in the cycle, you have spores. These are in the haze layer of Venus that we don’t really understand. And then rising up out of this haze layer, those spores collect moisture around them, and as they arise and build that droplet, the spores come back out and are capable of going through their biotic processes of replication. Eventually, the droplets get too big and begin to fall down. As these droplets fragment, the life desiccates back down to the spores.

This is a life cycle.

Now, this isn’t the first work to consider the possibility of life on Venus. This is the first work to predict phosphine, which has now been seen, and to describe a life cycle within this atmosphere. But there has been other work that said there could be life as an explanation to what we’re seeing on Venus.

Just over a year ago, on August 26, 2019, The Astronomical Journal contained an article by Yeon Joo Lee and collaborators. They pointed out that the dark albedo features in Venus’s atmosphere appeared to not be explainable. According to Lee: The particles that make up the dark splotches, have been suggested to be ferric chloride, allotropes of sulfur, disulfur dioxide and so on, but none of these, so far, are able to satisfactorily explain their formation and absorption properties. 

While Lee wasn’t able to explain the dark splotches with these normal means, sometimes you have to look beyond chemistry to biology. Collaborator Sanjay Limaye notes that: Observations of these particles show that they are about the same size and have the same light-absorbing properties of microorganisms found here on Earth. 

These dark splotches were earlier pointed out by noted biophysicist Harold Morowitz and astronomer Carl Sagan as potentially being microscopic life.

So here we have two radically different stories. We have today’s breaking news of the observational detection of the predicted phosphine in Venus’s atmosphere seen with two telescopes. And that phosphine exists in a large enough amount that it can’t be explained via photochemistry – chemistry in the atmosphere driven by interactions with sunlight. It can’t be explained in the amount that it exists by geochemical processes within Venus, as far as we know.

We see the paper from a year ago postulating that maybe the dark spots could be microscopic life.

This is all building on so many different things. The frustration is that we can’t go out and say anything definitively. But here is one final thought I want to put into your heads. Recently, our view of the history of Venus has begun to change as the possibility that 750 million years ago, it was capable of supporting life as we know it on its surface. That its climate was radically different. That there were liquid water seas.

Something happened. Something triggered a runaway greenhouse effect that destroyed this world for most life. 

Let’s consider that 750 million years ago when that catastrophic event happened, what was going on in our world. At that point, we had single-celled organisms capable of coming together in colonies to form sponges. We had, at 730 million years ago, the beginnings of comb jellies. We had life on this world. And it’s possible that there was life at the same time on Venus, and that, as that environment collapsed, it’s possible that some of the microbes took to the air and found a way to keep on going. Because life, maybe, does find a way.

Now it doesn’t have to be a story that goes that way. It could be that there is geochemistry on Venus that defies everything we currently understand, and life isn’t necessary. It could be that there is photochemistry in the complex atmosphere of Venus that does things that we aren’t creative enough to figure out, and life is not necessary. It’s possible that life formed in those clouds, originating there.

This is something that can’t happen on our world. Here on Earth, our clouds are wispy. They’re transitory. There is no standing moisture layer in the Earth’s atmosphere with persistent droplets capable of supporting life thriving in those droplets. We can’t do this. But on Venus, there is that persistent moisture; there is that possibility. We can’t know: is this unknown chemistry or is this potentially life not-to-distant from what we understand on Earth? We can’t know what the solution is until we go there and we’re able to somehow fly through the clouds and see in our samples the life under our microscopes.

Currently, there are no planned missions to Venus. Well, there are planned missions, but there are no funded, nuts-and-bolts, being put together, in the process of being built research spacecraft coming from a government-funded agency. Rocket Labs is looking to do a 15-kg microsat that would have the capability of carrying three kilograms of instrumentation with it. It’s probably not going to be what we need to say, “Yes, it’s life.”

Hopefully, these discoveries will motivate those spacecraft to come in the not-too-distant future.

This is a kind of amazing day. Today may be the day that we all look back on and say, “This is when we first realized we may not be alone in this universe.” And the place I thought most inhospitable in our solar system may be where that life is first discovered.

Remember today.

Learn More 

Possible Marker of Life Spotted on Venus

• Royal Astronomical Society press release 
• MIT press release 
• European Southern Observatory press release 
• “Phosphine Gas in the Cloud Decks of Venus,” Jane S. Greaves et al., 2020 Sep. 14, Nature Astronomy
• “The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere,” Sara Seager et al, 2020 Aug. 13, Astrobiology
• “Phosphine as a Biosignature Gas in Exoplanet Atmospheres,” Clara Sousa-Silva et al., 2020 Jan. 31, Astrobiology
• “Long-term Variations of Venus’s 365 nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope,” Yeon Joo Lee et al, 26 Aug. 2019, The Astronomical Journal

Credits

Written by Pamela Gay
Hosted by Pamela Gay
Audio and Video Editing by Ally Pelphrey
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