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Tanzina Vega: You're listening to The Takeaway, I’m Tanzina Vega. We're going to end today's show by moving away from life on earth to possible life on the planet next door. On Monday, scientists announced they've detected the gas called phosphine in Venus's atmosphere. Here on Earth phosphine is a toxic gas that's made by microorganisms and so the presence of phosphine in Venus's clouds means there's a chance that life could be there too. We're not talking about the aliens we see on movies and TV, We're talking about tiny microbial life forms.

Though it's too early to say that life does indeed exist on Venus, scientists have yet to find any other explanation for why the gas phosphine is present. For more on this, we're joined now by Dr. Martha Gilmore, a planetary geologist, and professor at Wesleyan University. Martha, thanks for joining me.

Martha Gilmore: You're very welcome. I'm happy to be here.

Tanzina Vega: As someone who's studied the planet Venus, were you surprised by this finding?

Martha Gilmore: Oh, certainly. We're always surprised to find evidence of life elsewhere. Also, the surprise is in the fact that the potential signal for life was detected in the clouds. Since we have so far, we think about life as being related to surfaces, planetary surfaces and so it expands our horizons to think that perhaps the clouds of Venus, or Earth, or another planet might be a niche for life.

Tanzina Vega: Now we mentioned at the top, we're not talking about aliens and as much as people may want to imagine, flying saucers and things like that, we're not there yet. We're talking about tiny little particles, aren't we? When we say life, what do we mean?

Martha Gilmore: We all probably think of Lando Calrissian in the Cloud City and that's probably not what's happening.

Tanzina Vega: Yet.

Martha Gilmore: Well, that's right. That would be great. No, whatever life lives in the clouds, in particular, has to take advantage of what's available to it, and to live in the cloud, you need to be small enough to probably adhere to a droplet, to be able to take in water and other nutrients that you need.

On earth, the microbes that we see in the clouds of the earth, which do not spend their entire life cycle but some of them hang out there for a little while, are lifted up from the Earth's surface. They're small enough to be carried by the winds and the clouds. Our expectation is that it must be small because it needs to be buoyant and float and take advantage of the materials available to it in the cloud.

Tanzina Vega: We talked a little bit about a gas called phosphine. What is it? I understand it doesn't smell too great.

Martha Gilmore: Yes, we've all started by looking at what is phosphine?

Tanzina Vega: You're not alone? This is encouraging to know.

Martha Gilmore: No, it's a nerve agent, it's actually very difficult to work with. It is the reason why cops have to be careful going into crystal meth labs because it is one of the things that is produced with crystal labs.

Tanzina Vega: Wow. What’s happening on Venus, doctor?

Martha Gilmore: I know, really. That's a whole other story, but it is a simple molecule, it is phosphorus with three hydrogens and this is a gas. One of the reasons why this is a compelling gas for biota is one, is because the things that life needs as far as we know to exist, there are several elements.

Carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Phosphorus is strange. Our teeth are made of phosphorus, it's a pretty important element, but it's derived from rock.

Life has to somehow find a way to pull the phosphorus out of rock to use it for its lifecycle. Phosphine is a gas and so it offers the opportunity to provide phosphorus for a potential life that live in a gas phase.

Tanzina Vega: About a little more than 50 years ago, scientists, including Carl Sagan, had speculated that life would exist in Venus's clouds, but a lot of that attention, at least in the past couple of decades, has really been on Mars. What's happening on Mars, should we go to Mars, is Mars inhabitable or not? Did we overlook Venus?

Martha Gilmore: Well, Mars is wonderful because of its thin atmosphere, we can see the morphological evidence of rivers and deltas. For example, the Mars 2020 is on its way to a delta in an ancient lake. We can measure the mineralogy from orbit, we can see the processes associated with water.

Venus is harder in that way because it's the cloud cover prevents us from using conventional methods like visible light to look at the surface. That's coupled with the fact that the Venus surface itself is as far as we know pretty uninhabitable. It's 450 degrees Celsius, that’s pretty much all you need to say actually.

Tanzina Vega: It’s all too hot for me personally.

Martha Gilmore: It’s too hot for water and water is one of the building blocks for liquid water for life. It's been overlooked as an astrobiological target, but a couple of things have changed in the last couple of decades.

One is the appreciation of life that spends some of its lifecycle in the clouds, as I mentioned before on earth. Also, the rise of the discovery of so many exoplanets around the galaxy which was the impetus for this study by Greaves.

They were trying to tune some of their telescopes to be able to look at the clouds of other planets and Venus is the one example where we can both look at the light coming from the atmosphere, which is what we can detect at exoplanets, but we can also visit it because it's right next door.

We can then compare what we measure inside the atmosphere if we go on a mission to what we see on the top of the atmosphere. What exoplanet that scientists want to learn is, what are the signatures of the atmosphere of a habitable or inhabited planet? Phosphine now enters that list of potential compounds that could indicate life.

Tanzina Vega: Martha, we've got about a minute left but I just want to ask you, does this indicate that there could be life on other planets potentially?

Martha Gilmore: Well, I hope so. Every discovery we make on another planet forces us to reconsider the origin of life on the earth, which we still don't understand.

We know that life exists in the universe, we're right here, but we still don't have the basic understanding of how Earth went from a lifeless planet to one that is teeming with life.

The discovery of how organic materials on other planets, how they can come together to take advantage of the environment particular to that planet is going to tell us a lot about how life evolves, in general.

Tanzina Vega: We’ll pay attention to that. Dr. Martha Gilmore is a planetary geologist and professor at Wesleyan University. Martha, thanks so much.

Martha Gilmore: You're very welcome.

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