SCOTT DETROW, HOST:
It is time now for our science news roundup from Short Wave, NPR's science podcast. And I am joined, as always, by the show's two hosts, Regina Barber...
REGINA BARBER, BYLINE: Woo (ph).
DETROW: ...And Emily Kwong.
BARBER: (Laughter) I'm so sorry.
EMILY KWONG, BYLINE: Hey, Scott.
BARBER: Hi.
DETROW: I'm going to guess you have brought three different science stories to talk about this week. Am I right?
KWONG: Yes. The discovery that our human ancestors probably made out with Neanderthals.
DETROW: OK.
BARBER: Yeah. And why scientists sent moss spores to space.
KWONG: And a planetary whodunit about the object that made the moon.
DETROW: We all know that I'm into moon content.
BARBER: Yes. Yes (laughter).
DETROW: So I appreciate that. But let's start with - let's start with the making out.
KWONG: Yeah. Under some prehistoric mistletoe.
DETROW: How...
KWONG: (Laughter).
DETROW: How did science address this question? Like, I don't even know where to start with that.
KWONG: Yeah. So many animals kiss. So birds, fish, insects, especially primates. And by kissing, scientists define that as nonaggressive mouth-to-mouth contact that does not involve passing food.
DETROW: That's an important aspect.
KWONG: (Laughter) And Matilda Brindle at the University of Oxford wanted to know how far back in evolutionary history does this go?
MATILDA BRINDLE: 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.
BARBER: 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.
DETROW: How do you even begin to see if somebody was kissing somebody 21 million years ago?
BARBER: (Laughter) Yeah.
DETROW: Like, was there a fossilized mid-kiss? I don't know.
BARBER: That would be really cool.
KWONG: Yeah.
BARBER: But no.
DETROW: No.
BARBER: (Laughter) 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.
KWONG: Which they did by determining which primates kiss and which do not. So Matilda had to watch a lot of video footage of primates locking lips.
BARBER: (Laughter).
KWONG: 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.
DETROW: Why does that matter?
BARBER: Well, most humans of non-African descent have a very small amount of Neanderthal DNA.
DETROW: OK.
BARBER: 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.
BRINDLE: 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.
DETROW: What a romantic image.
BARBER: I know.
DETROW: Equally romantic in my mind is moss spores in space.
KWONG: Ooh.
BARBER: Right. Yeah.
DETROW: (Laughter) How did this experiment come about?
KWONG: 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.
DETROW: 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.
BARBER: Yeah. You want them for things like oxygen production, maybe to help terraform a planet once that becomes possible. And for many people, aesthetics.
DETROW: Right. Right. That's true. But why moss in particular?
KWONG: 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.
TOMOMICHI FUJITA: 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.
KWONG: This is plant biologist Tomomichi Fujita at Hokkaido 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.
BARBER: 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.
DETROW: So the moss spores passed the UV test on Earth. How did they do in space?
KWONG: They did shockingly well, says Magdalena Bezanilla, a cell biologist at Dartmouth who was not involved in this work. Her lab just happens to study the same moss.
MAGDALENA BEZANILLA: I was really surprised. I mean, the spores just went out. They were just phenomenal.
KWONG: 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 iScience.
DETROW: So are we going to terraform with them?
BARBER: Well, the paper points out that moss and other briophytes 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.
KWONG: 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...
DETROW: Got it.
KWONG: ...In space under this extreme radiation.
DETROW: Finally, we're going to talk about a moon. This week it's our moon.
BARBER: Yes.
DETROW: A close-to-home moon.
BARBER: Yes.
DETROW: I - Gina, I'm always pro-moon stories. Tell me about this week's.
BARBER: Yes, Scott. OK. Right now, in the sky, there's a moon.
DETROW: True.
BARBER: OK. And then in the beginning, when the solar system was forming, there was a Proto-Earth and no moon.
DETROW: No moon.
BARBER: 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.
KWONG: 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 Prissel put it. She's a geochemist from Purdue University who didn't work on this study.
KELSEY PRISSEL: For me, this paper reads kind of like a planetary whodunit where we're trying to figure out how do we form the Earth-moon system.
DETROW: All right. So how - where did Theia the Earth smasher...
KWONG: (Laughter).
BARBER: Yeah.
KWONG: That's a good name.
DETROW: It's like a mythological phrase.
KWONG: It's like a...
DETROW: ...Come from?
KWONG: ...Marvel villain.
DETROW: Yeah.
KWONG: 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 Earth. So Theia was born in the inner solar system.
BARBER: Scott, the call is coming from inside the house, OK? And it - this also gives us a clue about maybe the origins of water on Earth.
DETROW: Water? How so?
BARBER: 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.
DETROW: But now I'm curious. Where did Earth's water come from?
BARBER: So I asked that to the lead author of this study. His name is Timo Hopp and he's from the Max Planck Institute in Germany.
TIMO HOPP: Theia could not have brought a lot of water to the Earth. That means that water must have come from another type of material or process later or earlier. Likely earlier.
KWONG: 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.
BARBER: But sadly, technology to withstand, like, the harsh surfaces of Mercury and Venus and actually travel there efficiently and back, it - our technology is just not totally there.
DETROW: That's Regina Barber and Emily Kwong from NPR's science podcast, Short Wave. You can subscribe now for new discoveries, everyday mysteries and the science behind the headlines. Thanks to both of you.
BARBER: Thank you.
KWONG: Thank you.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
