Particles of Thought

HAKEEM: Yeah. All right, so let's go back out to space a little bit.

PETER: Sure. Let's do it.

HAKEEM: And let's go to the red planet. Because we are recording this on September 10th. And there has been an announcement from NASA, and let me read this. It's a quote. Just a few hours ago, NASA had a big press conference saying they've discovered what I quote, very well could be the clearest sign of life that we've ever found on Mars. Let me catch my breath.

PETER: Yeah, take a deep one.

HAKEEM: Bro. Seriously? Clearest sign? Clearest sign of life. I would be happy with a sign of life. There are pictures. What NASA points out in this image is something called a leopard spot. They circle this rock and say leopard spot. So I'm guessing they're not saying that a leopard spot fell off a leopard on Mars and now it's right here on the ground. It's some sort of mineral signature. So what is going on with the leopard spot that seems to make it the clearest sign of life yet?

PETER: Yeah. So understandably NASA scientists like the rest of us, we give these things nicknames. And so if you look at the photo, you can see that it's got these speckles and it kind of looks like the spots on a leopard and it looks like a sediment deposit with different kinds of minerals sort of sprinkled in there, if you will. And what's really exciting is that those minerals have very different chemical properties. And so on earth you don't usually find them next to one another unless some microbe has been involved. I want to underline the word usually.

HAKEEM: Usually, right.

PETER: This, I would not read this as a smoking gun that there was a microbe. But what it does suggest is that, like here on earth when we see these different kinds of minerals side-by-side, that chances are there's some microbe that did this. And in the case of Mars, there was a microbe that did this in the past and this became preserved in this sediment. What's exciting? That's why the NASA scientists who are publishing these data are like, this smacks a bit of what we see microbes doing on earth.

HAKEEM: So in this particular sample that NASA has produced, why is it that them being in proximity, I get it that they're in proximity, but why does life put them next to each other versus a non-living scenario?

PETER: Yeah, one of the things that I've been alluding to is this idea of life out of disequilibrium and disequilibrium from the environment. So what I mean by that is, we know, for example, that there are microbes on earth that in the deep ocean sediments, when you get a few centimeters or a meter or so into the ocean sediments, oxygen's gone. So there's no oxygen, dioxygen, right? There's no oxygen gas dissolved in the water. In many of those places, there's iron oxides, just call it rust, generically speaking different forms of it. But there are microbes that can take that rust and they can breathe it the way you and I use oxygen gas, they will breathe that rust through a really cool process. And so doing, they will produce non-rusty iron or iron two. And that's often soluble, but sometimes it reacts with elements. And I have a buddy Brandy Toner and Mrs. Soda, she loves this stuff. She's good at it.

And what she does is uses really cool probes like the synchrotron facilities, these places where we can zap things. And she looks for different mineral phases. And if you've got a rust sitting next to a non-rust, unless it's in a specific place like a vent,

Right? If you've got that sitting in deep sea sediments, there's a good chance a microbe did that.

HAKEEM: Oh, it's kind of like with uranium decaying into lead.

PETER: Yes.

HAKEEM: You see, right. And so this particular combination smacks of some microbe breathing this oxide and turning it into making this iron too. That's why the Mars, the lead scientists were excited. We see bits of this on earth.

HAKEEM: Right. So for these particular minerals that they found on Mars, where do we find the same mineral side by side on earth?

PETER: Yeah. Again, it's the same. It's underwater hot springs. It's deep sea sediments.

HAKEEM: I see.

PETER: They're iron-containing minerals, and it looks like a microbe could have been breathing one and producing the other.

HAKEEM: So is it always deep sea because on Mars, Jezero Crater is sort of like my understanding has a river delta type situation where water was flowing into a crater lake?

PETER: Yeah, great question. It's not always deep sea, but the reason on earth it's often deep sea is because we have this atmosphere full of oxygen. And the moment a microbe on the surface takes say rust and turns it into this non-rusty iron too, atmospheric oxygen messes with it. So we've got these minerals, it's unusual to find them juxtaposed. And there they are sitting side by side in this mud. So here's what I think is cool. Here's where I agree with NASA. This leans towards something less usual, unusual. It's something unusual. And so it means that these minerals, which are vivianite and greigite, I remember correctly, the fact that they're near each other is similar to what we see here on earth. It's sort of circumstantial-

HAKEEM: Circumstantial evidence.

PETER: Evidence. But it's cool. It's a good place to look.

HAKEEM: It's a step in the direction of finding life.