Scott Detrow (2:15)

All right, we are back. And to start off, tell me about our ancestors making out with Neanderthals.

Emily Kwong (2:20)

It happened under some prehistoric mistletoe.

Scott Detrow (2:23)

How did science address this question? Like, I don't even know where to start with that.

Regina Barber (2:27)

Yeah, so many animals kiss. So birds, fish, insects, especially primates.

Emily Kwong (2:33)

And by kissing, scientists define that as non aggressive mouth to mouth contact that does not involve passing food that's an important aspect. And Matilda Brindle at the University of Oxford wanted to know, how far back in evolutionary history does this go? If you think about the fact that humans and our closest living relatives, chimpanzees and bonobos, all kiss, it makes sense that the common ancestor of those three species kisses as well.

Regina Barber (3:00)

So tracking back through evolutionary time, Matilda's team found that kissing was present in the ancestor of all large apes 21 million years ago. And they published these results in the journal Evolution and Human Behavior.

Scott Detrow (3:12)

How do you even begin to see if somebody was kissing somebody 21 million years ago? Like, like, was there a fossilized mid kiss? I don't know.

Regina Barber (3:20)

That would be really cool. But no, this was all done through what's called phylogenetic analysis. Matilda and her colleagues basically treated kissing as a trait and mapped it onto, like a tree of primates, which they.

Emily Kwong (3:33)

Did by determining which primates kiss and which do not. So Matilda had to watch a lot of video footage of primates locking lips and. And she compiled evidence of which of our primate cousins canoodle, she built her family tree and she discovered something else, which is that Neanderthals probably kissed too. And that is a big deal.

Scott Detrow (3:53)

Why does that matter?

Regina Barber (3:54)

Well, most humans of non African descent have a very small amount of Neanderthal DNA. And we know that Neanderthals and humans interbred after the two species split. And this kissing study gives us a little bit more insight into those relationships.

Emily Kwong (4:08)

Humans and Neanderthals were probably kissing each other, which is a way more romantic take on human Neanderthal relationships than I think we might have thought of before.

Scott Detrow (4:18)

What a romantic image.

Regina Barber (4:19)

I know.

Scott Detrow (4:20)

Equally romantic in my mind is moss spores in space.

Regina Barber (4:23)

Right? Yeah.

Scott Detrow (4:24)

How did this experiment come about?

Emily Kwong (4:26)

So as humans contemplate long term space travel, scientists want to know which plants may survive the extremes of space. Because space is cold, there is a lot of radiation, it's a vacuum. Scientists can simulate some of that on Earth, but to know how a plant will do in space, you got to put it there.

Scott Detrow (4:44)

And I assume that if you're going on a really long space travel, at some point, you'd probably want some plants with you.

Regina Barber (4:48)

Yeah. You want them for things like oxygen production, maybe to help terraform a planet once that becomes possible. And for many people, aesthetics.

Scott Detrow (4:58)

Right, right, that's true. But why moss in particular?

Regina Barber (5:01)

Well, because moss has some, like, incredible survival strategies. Bryophytes, the group of plants that includes mosses, were the first plants to move from water to land.

Scott Detrow (5:10)

We believe moss colonized on land about 500 million years ago. So they can survive for a long such period. Even dinosaur may be extinct, but still moss can survive.

Emily Kwong (5:25)

This is plant biologist Tomomichi Fujita at Hokkairu University who led the work. And he says land is a lot harsher than the ocean, with larger temperature fluctuations, higher risk of drying out, and more uv.

Regina Barber (5:37)

In ground studies before the team sent moss to space, they found that moss spores, which were enclosed in this protective coating called a sporangium, did much better with exposure to extreme heat and cold, and importantly to uv.

Scott Detrow (5:50)

So the moss spores passed the UV test on Earth. How did they do in space?

Emily Kwong (5:54)

They did shockingly well, says Magdalena Bezania, a cell biologist at Dartmouth who is not involved in this work. Her lab just happens to study the same MO. I was really surprised. I mean, the spores just went out. They were just phenomenal. After nine months in space, more than 80% of these spores germinated once they were back on Earth. From this, scientists calculate the spores could go about 15 years in space conditions and still germinate. The team published their results in the journal Eye Science.

Scott Detrow (6:24)

So are we going to terraform with them?

Regina Barber (6:27)

Well, the paper points out that moss and other biophytes can survive low light. They're great at making oxygen and fixing carbon, and they could be good at transforming other planets surfaces into fertile soil.

Emily Kwong (6:38)

But the scientists have only shown that the spores can survive. You know, they haven't shown that the moss, the green fuzzy stuff that you see on earth, can grow in space under this extreme radiation.

Scott Detrow (6:48)

Finally, we're gonna talk about a moon. This week. It's our moon. A close to home moon. Yes, Gina, I'm always pro moon stories. Tell me about this week's.

Regina Barber (6:58)

Yes, Scott. Okay, right now in the sky, there's a moon.

Scott Detrow (7:01)

True.

Regina Barber (7:02)

Okay. And then in the beginning, when the solar system was forming, there was a proto Earth and no moon.

Scott Detrow (7:07)

No moon.

Regina Barber (7:07)

Then something maybe the size of Mars came and smashed into proto Earth. And that debris from that giant crash made the moon. And the name of this like planet smashing object was Theia.

Emily Kwong (7:19)

Now a new paper in the journal Science is attempting to figure out what this object Theia was made out of and where in the solar system it came from. Here's how Kelsey Preizl put it. She's a geochemist from Purdue University who didn't work on this study. For me, this paper reads kind of like a planetary whodunit, where we're trying.

Scott Detrow (7:37)

To figure out how do we form.

Emily Kwong (7:40)

The Earth moon system.

Scott Detrow (7:41)

All right, so where Did Theia, the Earth Smasher, it's like a mythological phrase.

Regina Barber (7:47)

It's like a Marvel villain.

Scott Detrow (7:48)

Yeah.

Emily Kwong (7:48)

Well, they looked at lunar samples brought back from NASA's Apollo missions and other meteorites from our solar system. And comparing those samples to rock samples from Earth, they found that Theia, the Earth Smasher, could have been born even closer to the sun than Ear. So Theia was born in the inner solar system.

Regina Barber (8:07)

Scott, the call is coming from inside the house. Okay. And this also gives us a clue about maybe the origins of water on Earth.

Scott Detrow (8:15)

Water? How so?

Regina Barber (8:16)

If Theia had formed in the outer solar system. So past Jupiter, where it's colder, there's ice. Some scientists thought that Theia could have delivered water to Earth during that collision. But with this study, we now know that Theia came from the inner solar system, which is drier. And that means that Theia was probably not the source of water on Earth.

Scott Detrow (8:34)

But now I'm curious. Where did Earth's water come from?

Regina Barber (8:37)

So I asked that to the lead author of the study. His name is Timo Hopp, and he's from the Max Planck Institute in Germany.

Scott Detrow (8:43)

Say I could not have brought a lot of water to the Earth. That means the water must have come from another type of material or process later or earlier. Likely earlier.

Emily Kwong (8:52)

Now, water could have come from comets. It could have formed when the Earth did. Though, to truly solve the debate, we're just going to need to gather more space rocks, because if Theia did indeed come from closer to the sun, we would need samples from Venus or Mercury to prove it.

Regina Barber (9:06)

But sadly, technology to withstand, like, the harsh surfaces of Mercury and Venus and actually travel there efficiently and back, Our technology is just not totally there.

Scott Detrow (9:17)

Just seems like it's too hot.

Regina Barber (9:19)

Yes, it is too hot.

Scott Detrow (9:20)

That's my scientific analysis right now.

Regina Barber (9:22)

Scott, it is always super fun to have you. We love talking about space with you.

Emily Kwong (9:28)

Yep.

Scott Detrow (9:28)

Thanks. As long as you keep upping the weirdness of the stories each week, I'll be right.

Emily Kwong (9:31)

I try every time.

Regina Barber (9:32)

We'll try.

Emily Kwong (9:33)

Yeah.

Scott Detrow (9:34)

Thank you both.

Sponsor/Advertiser (9:35)

Thank you.

Regina Barber (9:36)

You can hear more of Scott Detrow on consider this NPR's afternoon podcast about what the news means for your. This episode was Produced by Burly McCoy and Kai McNamee. It was edited by Rebecca Ramirez and Christopher Intagliota.

Emily Kwong (9:47)

Tyler Jones checked the facts. Zimon, Laszlo Janssen and Damien Herring were the audio engineers. Hi, I'm Emily Kwong.

Regina Barber (9:54)

And I'm Regina Barber. Thank you for listening to Short Wave, the science podcast from npr. We have too much fun this message.

Sponsor/Advertiser (10:05)

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