StarTalk Live! at the Beacon (Part 1): Chasing Comets

Neil deGrasse Tyson and Eugene Mirman explore the early solar system and go chasing comets with the help of cosmochemist Dr. Natalie Starkey (ESA Rosetta Mission) and comedians Ilana Glazer and Scott Adsit. Recorded live at the Beacon Theatre in NYC.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:14Eugene Mirman?

  StarTalk Live!

• 0:19Eugene Mirman?

  It is my very great pleasure to introduce your host, a very genial and excellent science communicator and destroyer of planets, the Galactus of Earth. Ladies and gentlemen, Neil deGrasse Tyson!

• 0:43Neil deGrasse Tyson?

  Eugene, so who's next? Yes, you have two guests of your own.

• 0:47Eugene Mirman?

  I do. It is my great pleasure to bring out from Broad City, Alana Glazer.

• 0:55Eugene Mirman?

  And from NBC's 30 Rock, Scott Axon!

• 1:02Neil deGrasse Tyson?

  Tonight's topic is on the solar system, comets, and other vagabonds, including Pluto.

• 1:17Neil deGrasse Tyson?

  And we combed the world to find someone who has just that kind of expertise. And I found in England, there is a woman who will soon be moving to California, bringing her expertise state to stateside. She's one of the principal investigators on the Rosetta mission to a comet where we landed a probe on the comet. She did that. And she has general expertise about comets and will also take us to Pluto in all ways necessary. Give a warm New York, United States welcome for Natalie Starkey. Natalie, come on out.

• 1:56Neil deGrasse Tyson?

  So Natalie, first welcome to the United States.

• 1:59Natalie Starkey?

  Thank you.

• 1:59Neil deGrasse Tyson?

  So professionally, you care a lot about comets. And I've spoken to people, much to my surprise, that there's not enough clarity when people talk about comets, asteroids, meteoroids, meteorites. So could you just straighten us out on that?

• 2:15Natalie Starkey?

  Okay, it is quite confusing, and people don't seem to understand it, because we use a lot of similar words. So what we're talking about is, an asteroid is simply a space rock that is leftover from the formation of the planets. So it's a rocky thing that formed quite close to the sun. Whereas comets, on the other hand, formed very early. They're made of gas, and ice, and dust.

• 2:38Neil deGrasse Tyson?

  Like it's frozen gases?

• 2:39Natalie Starkey?

  Frozen gases. They formed even earlier than the asteroids. So they take us back 4.6 billion years, right to the beginning of the solar system.

• 2:48Eugene Mirman?

  They're the Rolling Stones of space. Sing, Rolling Stones!

• 2:55Natalie Starkey?

  So we should also just mention a meteorite, which a lot of people have heard of. That's simply a space rock sitting on the surface of the Earth. Before it hits the Earth, it's either an asteroid, or a comet, or a piece of another planet, like Mars, or it could be a piece of the moon. But anything that arrives from space and lands is a meteorite. And we collect those all over the place and analyze them.

• 3:16Speaker 03

  Is the moon throwing stuff at us?

• 3:19Natalie Starkey?

  Yes. I know, I know, it's crazy. So yeah, but from quite a while ago. So when the moon was impacted by different things hitting it in the past, it threw off material, ejected it up, and that flies around space for millions of years until eventually it ends up hitting the Earth or another planet. So that's how we get some samples of the moon.

• 3:41Neil deGrasse Tyson?

  That was true with Mars as well.

• 3:42Natalie Starkey?

  Yeah.

• 3:42Neil deGrasse Tyson?

  We have Mars rocks on Earth that we didn't have to go there and get.

• 3:45Natalie Starkey?

  Exactly. We've never actually got a sample from Mars directly. We've only been there and done analysis on the planet rather than bringing material back.

• 3:53Speaker 03

  So we're wasting an enormous amount of money.

• 3:56Natalie Starkey?

  You could look at it that way. We get a lot of free stuff. We, you know, we don't need... No, we do need to go. We'll come on to that.

• 4:03Neil deGrasse Tyson?

  You were saying...

• 4:04Speaker 04

  Yeah, okay. So you're talking about like a meteor that's sitting on a planet?

• 4:09Natalie Starkey?

  It's a piece of rock that was, so once an asteroid hits another planet, it breaks up the rock and ejects it into the atmosphere. So then it circles around and ends up on another planet eventually.

• 4:19Speaker 04

  So you're like talking about the same stuff, but you call it different words at different points in its process.

• 4:24Natalie Starkey?

  Exactly.

• 4:25Speaker 04

  Love it. That is trippy.

• 4:27Natalie Starkey?

  Just to be confusing, yeah.

• 4:29Neil deGrasse Tyson?

  That's not any weirder than calling a little human a child and an older human an adult.

• 4:33Speaker 04

  Right.

• 4:33Neil deGrasse Tyson?

  They're both human, right?

• 4:35Speaker 04

  That's right, but just my vocabulary. I'm like, a meteor, asteroid. Are those the same?

• 4:40Natalie Starkey?

  A meteor is a little bit of an asteroid that's kind of been broken off and is circling towards the earth.

• 4:46Eugene Mirman?

  Which one makes you telekinetic?

• 4:51Eugene Mirman?

  We both want to know.

• 4:52Natalie Starkey?

  Which one? It makes you what?

• 4:55Eugene Mirman?

  Telekinetic, when you can use your mind to manipulate the physical world?

• 4:59Natalie Starkey?

  Do you know what? That's a really good question.

• 5:01Speaker 03

  I thought you were a scientist.

• 5:04Natalie Starkey?

  Yeah.

• 5:05Neil deGrasse Tyson?

  So, you spoke casually about finding a meteorite on the ground, but that meant it fell from the sky and hit. And so not all of these can possibly be good for us. So can you comment on the relative risks between getting slammed by an asteroid and slammed by a comet?

• 5:24Natalie Starkey?

  Yeah, so I mean, it's a real possibility that we will be hit by a large asteroid or comet somewhere in our future. Now, we think for the next maybe-

• 5:33Neil deGrasse Tyson?

  Can you be a little more specific?

• 5:34Speaker 04

  Yeah, where in the future?

• 5:36Eugene Mirman?

  Like 100 years or 1,000 years or?

• 5:39Natalie Starkey?

  We don't know. We think over the next 100 years, we're not going to be hit by anything really devastating, kind of like the thing-

• 5:45Speaker 04

  I know, do you always say that? Are you always like, "Ah, in 100 years"?

• 5:48Natalie Starkey?

  Yeah, it's a very scientific thing, you know?

• 5:50Speaker 04

  And like 100 years ago, they're like, "I don't know, 100 years"?

• 5:52Neil deGrasse Tyson?

  How far out can we spot one of these things?

• 5:53Natalie Starkey?

  Okay, so we think we know where all the big asteroids are and we think they're not on a collision course with Earth at the moment. So we're kind of good, but-

• 6:00Neil deGrasse Tyson?

  We think?

• 6:02Natalie Starkey?

  We're pretty sure, but we can't be 100%. So, but the-

• 6:06Speaker 03

  This is not the Bible, Neil.

• 6:07Neil deGrasse Tyson?

  I know. Sorry, it doesn't have that level of certainty. I got that. Okay.

• 6:16Neil deGrasse Tyson?

  So when you say, "I think," those are your verbal margins of uncertainty?

• 6:21Natalie Starkey?

  Yeah.

• 6:21Neil deGrasse Tyson?

  Yes, okay, fine.

• 6:22Natalie Starkey?

  Exactly. We're 90% sure, maybe.

• 6:24Neil deGrasse Tyson?

  Okay.

• 6:25Natalie Starkey?

  Around that kind of thing. But the problem is, we don't know where every single object in the solar system is. There's millions of objects, asteroids and comets. And the comets in particular come in at strange angles that we can't really predict. And we don't see them coming, they come very fast.

• 6:40Neil deGrasse Tyson?

  When you say strange angles, we have the plane of the solar system, where the asteroids come in, and the asteroid belt. But comets, just any old which way?

• 6:50Natalie Starkey?

  Yeah, pretty much. And they're coming in from much further out. So they come in with a bit of surprise sometimes. Some of them, we know where they are and we're tracking them. But there's always gonna be one that we're not gonna see, so...

• 7:01Speaker 03

  They all came from our sun.

• 7:03Natalie Starkey?

  Yes, we... yes.

• 7:05Eugene Mirman?

  Mostly.

• 7:07Natalie Starkey?

  Mostly.

• 7:08Eugene Mirman?

  We're not trying to trick you, you can just tell us the truth. But, has like, can a comet hit the Earth? Is it gonna happen?

• 7:17Eugene Mirman?

  Some of that, so explore that.

• 7:18Natalie Starkey?

  The dinosaurs were probably killed off by a massive comet hitting the Earth. So it wasn't the dinosaurs directly being hit on the head and being knocked out.

• 7:27Eugene Mirman?

  But they were all assholes, so that's not...

• 7:29Natalie Starkey?

  Right. Not all of them.

• 7:32Eugene Mirman?

  And we're great.

• 7:34Natalie Starkey?

  So the problem with these impacts is that you end up changing the whole, you know, environment of the Earth. You throw up so much dust and gases and you melt, really melt where it's hit, part of the Earth. So basically, the Earth becomes uninhabitable by many species. It didn't quite kill off everything, otherwise we wouldn't be here. But, yeah, it kills a lot.

• 7:56Neil deGrasse Tyson?

  But so just to clarify, so to just say that it melts and throws up gases, there's the energy of the comet's motion and its mass coming in and then...

• 8:07Neil deGrasse Tyson?

  It stops moving after it hits the earth. And where did all the energy go? It melts the earth. It kicks up, devastates the climate, kills the dinosaurs.

• 8:16Natalie Starkey?

  We get a big crater, you know that. We've got plenty of them. In fact, if you look at the moon, we've got loads of examples of where the moon has been completely hit by asteroids and comets in its past. The earth was hit as much as the moon, but we have plate tectonics, which means that our surface is renewed all the time over geological history.

• 8:34Neil deGrasse Tyson?

  We cover the evidence.

• 8:35Natalie Starkey?

  Yeah, we've lost that evidence, so.

• 8:38Speaker 04

  That's why the moon has like acne.

• 8:40Natalie Starkey?

  Yeah, yeah.

• 8:42Neil deGrasse Tyson?

  So, there's been discussion about the possibility of comets. Because when we analyze comets, there's interesting chemistry going on there. We find organic elements.

• 8:52Natalie Starkey?

  Exactly, yeah.

• 8:52Neil deGrasse Tyson?

  Organic molecules.

• 8:53Eugene Mirman?

  Like cheese? What do you mean?

• 8:56Natalie Starkey?

  That's the moon.

• 8:58Neil deGrasse Tyson?

  Good.

• 8:59Eugene Mirman?

  Sorry. Salami?

• 9:03Eugene Mirman?

  What kind of organic stuff do we find?

• 9:05Neil deGrasse Tyson?

  It's the moon that's made of cheese.

• 9:08Neil deGrasse Tyson?

  So, if that's the case, I mean, I remember reading speculative novels about viruses from space or microbes from space, possibly comets, seeding earth. So is that still a thing?

• 9:25Natalie Starkey?

  Yeah, I mean, this is really one of the main leading theories of how we think we're all here. We think that probably comets or asteroids delivered life to earth. Not as life like us, obviously.

• 9:38Eugene Mirman?

  Not an asteroid full of, or like a comet full of cats.

• 9:42Neil deGrasse Tyson?

  Cats.

• 9:44Neil deGrasse Tyson?

  Fully formed cats.

• 9:45Eugene Mirman?

  Fully formed cats.

• 9:49Eugene Mirman?

  And from cats came people.

• 9:50Speaker 03

  Were fetons or volcanoes involved in this?

• 9:53Natalie Starkey?

  We'll come back to the comets first. So, organic material. What we're talking about simply is carbon, hydrogen, and oxygen bonds. And this is organic material. So what we call this is like the precursors for life. It isn't life itself, but it's the material that we need to form life.

• 10:10Neil deGrasse Tyson?

  And these are common ingredients in the universe?

• 10:11Natalie Starkey?

  Yep, common ingredients. And we know that comets and asteroids contain organic material. We've actually found amino acids on an asteroid. So, and a comet, in fact, so we know.

• 10:22Neil deGrasse Tyson?

  So amino acids are the building blocks of protein?

• 10:24Natalie Starkey?

  Exactly.

• 10:25Eugene Mirman?

  If you believe Star Trek.

• 10:28Eugene Mirman?

  Real science does come up in Star Trek.

• 10:32Neil deGrasse Tyson?

  Okay, so... They come up in other places, too.

• 10:36Neil deGrasse Tyson?

  Okay, so Natalie, I have a question. If carbon, nitrogen, and oxygen, benighted as organic elements, making organic molecules, if they're common, then why do we need them to come to Earth from a comet? Why wouldn't Earth have been endowed with them from the beginning?

• 10:52Natalie Starkey?

  Okay, so one of the issues is that when the Earth...

• 10:54Neil deGrasse Tyson?

  I get like that was a good question, can I?

• 10:56Natalie Starkey?

  That's a good question.

• 10:59Natalie Starkey?

  Really good.

• 11:00Neil deGrasse Tyson?

  So there, Natalie, all right.

• 11:03Natalie Starkey?

  I have an answer, don't worry.

• 11:07Natalie Starkey?

  So when the Earth formed, it formed really close to the Sun. So we're talking about a really hot, chaotic environment next to the Sun. Everything was flying about at the beginning of the solar system. It was really energetic. Now, what this meant was that we didn't really have rock. We had magma of rock, like we get at volcanoes.

• 11:23Neil deGrasse Tyson?

  Melted rock.

• 11:24Natalie Starkey?

  Melted rock. So this, we're talking kind of 1,200, 1,600 degrees Celsius. This is really hot. So, as you can probably guess, these simple volatile elements, like carbon, hydrogen, and oxygen...

• 11:37Neil deGrasse Tyson?

  The volatile elements that won't, that if you heat them, they become gas.

• 11:41Natalie Starkey?

  Yeah, exactly. They're not gonna survive in that kind of environment. So, we think when the Earth formed, that we couldn't have began with all the things we needed for what we've got now, including water. We don't know where all our water came from. We take it for granted, you know, we drink it all the time, but we don't actually know where it came from. So not only did comets potentially deliver organic material, but they might have also brought our water in.

• 12:04Neil deGrasse Tyson?

  So we need comets?

• 12:06Natalie Starkey?

  Probably, yeah. I mean, they killed off the dinosaurs, that's bad. Maybe, maybe we wouldn't be here otherwise, though, but actually, we might not be here without them anyway, so...

• 12:14Neil deGrasse Tyson?

  So, so we have this love-hate relationship with this thing that can kill us, what enabled us in the first place?

• 12:19Natalie Starkey?

  Yeah.

• 12:20Neil deGrasse Tyson?

  Like our parents.

• 12:25Neil deGrasse Tyson?

  Alright, so you specialize in comet dust. What is that gonna tell us?

• 12:32Natalie Starkey?

  Okay, so I work at a really, really small scale.

• 12:35Neil deGrasse Tyson?

  Because usually when you study an object, it's to learn about the object. But every time I hear people, yourself included, talk about studying comets, it's so that we can learn about other stuff.

• 12:44Natalie Starkey?

  Well, yeah, and the comets themselves. What's important is that the objects I study, you can't really see because they're so small. I have to use really specialized instruments to study these bits of dust. I'm talking 10 micron particles. So if you take a single human hair, it's about 100 microns. So these grains are a tenth of a human hair. So they're very small.

• 13:07Neil deGrasse Tyson?

  And where do you get them?

• 13:08Natalie Starkey?

  Where do we get them? They come from comets, we think, and asteroids. So this is the problem. I have two types of samples. But quite luckily, they just arrive on Earth quite naturally.

• 13:19Neil deGrasse Tyson?

  Where do you...

• 13:19Natalie Starkey?

  I know, I'm like...

• 13:20Neil deGrasse Tyson?

  Sorry, where do you get them? Oh, you're getting there.

• 13:23Natalie Starkey?

  I'll get them.

• 13:26Natalie Starkey?

  So about 40 tonnes of space dust arrives on Earth every single day.

• 13:30Neil deGrasse Tyson?

  Oh my god, what can we do?

• 13:31Natalie Starkey?

  Huge amount of stuff, loads of it. And NASA have these high-flying aircraft, a bit like the U2 spy plane. And it's called the ER2. And they fly high in the stratosphere, about 60,000 feet. So they're in astronaut suits and everything. It's like right on the edge of the Earth. And they just fly along, and it's quite a simple technique. They've got little sticky pads on the wings. I kid you not. It's made of silicone oil. So it's a special oil that is sticky and slows down these particles as they enter from space through the atmosphere and hit these collector plates. So then we get effectively free samples of comets without having to actually go in.

• 14:14Neil deGrasse Tyson?

  Yeah, it sounds very inexpensive.

• 14:19Speaker 04

  Fifty thousand, that's crazy. It's like I'm picturing Swiffer hands. That's unbelievable.

• 14:25Neil deGrasse Tyson?

  So this is like flypaper or something, except for comet dust.

• 14:28Speaker 04

  Honestly, how much is it? What are we talking?

• 14:30Natalie Starkey?

  How much dust or how much?

• 14:31Speaker 04

  How much a scoop of comet dust? I don't know.

• 14:34Natalie Starkey?

  Oh, not very much.

• 14:36Neil deGrasse Tyson?

  What's the street value of comet dust?

• 14:38Speaker 04

  I know, it really looks like a drug.

• 14:39Natalie Starkey?

  If I tried to sell it to you, you wouldn't be able to see it. So you probably, I could sell you anything. I should be like, hit some.

• 14:50Speaker 04

  I'll buy it.

• 14:51Eugene Mirman?

  Well, that's the thing. Are you saying scientists are invisible drug dealers?

• 14:56Neil deGrasse Tyson?

  No, dealers have invisible drugs. That's different.

• 14:59Eugene Mirman?

  You're right.

• 14:59Speaker 03

  Scientists are like mechanics, though. They can tell us anything and we'll just go, yeah, okay.

• 15:05Eugene Mirman?

  Yeah, once I saw a microwave, I was like, okay, anything's possible.

• 15:09Neil deGrasse Tyson?

  But wait, wait, just to clarify. So that's one way to get space dust. Whether or not it's from a comet.

• 15:15Natalie Starkey?

  Yeah.

• 15:15Neil deGrasse Tyson?

  You don't know.

• 15:16Natalie Starkey?

  We can't ever be sure, no.

• 15:18Neil deGrasse Tyson?

  Okay, however, you studied an actual mission that went to a comet. So now you're studying the Stardust mission.

• 15:25Natalie Starkey?

  Yeah.

• 15:25Neil deGrasse Tyson?

  And what was that mission?

• 15:26Natalie Starkey?

  This landed back in 2006 in a little capsule in the desert. And in that capsule, we had real samples of a comet. For the first time, we collected actual samples.

• 15:38Neil deGrasse Tyson?

  I've got to get back to Eugene's question. How did it get comet samples?

• 15:41Natalie Starkey?

  Okay, so.

• 15:42Neil deGrasse Tyson?

  You just said it landed in the desert and it had comet samples.

• 15:46Natalie Starkey?

  Just arrived, yeah. So this space mission used, again, quite a simple collection technique. It was almost like a tennis racket. This collector comes out and a big, it's about kind of this big, a meter or so. And made up of these little blocks of called aerogel, which I think NASA developed specifically. And this gel is basically silica and it decelerates the particles. Because the thing is, this mission just flew through the tail of a comet, which I can explain what that is. And the particles coming off the comet that form this tail are going at about six kilometers per second. So this is like faster than a speeding bullet. They need to be slowed down as they are collected, otherwise you're going to destroy them all.

• 16:31Neil deGrasse Tyson?

  You need to slow them down slowly.

• 16:33Natalie Starkey?

  Yeah, exactly. But we didn't slow them down quickly enough. Does that make sense?

• 16:39Neil deGrasse Tyson?

  Slowly, oh.

• 16:39Natalie Starkey?

  Slowly enough, or whatever. Because actually, we lost the volatile components. So we mentioned these kind of, the organic components in the samples earlier. So we just get the rocky bits of that comet, the dust rocky bits. But this is the only sample returned mission we've had from a comet. So it's the only samples we've ever had. And it's been quite a change for us in our understanding of comets. We've learned a huge amount from this mission.

• 17:07Neil deGrasse Tyson?

  Just, it's amazing. We launched something from Earth. We pass it through the tail of a comet. Bring it back, land it in the desert, you open it up and analyze it.

• 17:17Natalie Starkey?

  Yep.

• 17:17Neil deGrasse Tyson?

  Okay. Now, there was a movie called The Andromeda Strain, which was exactly that plot.

• 17:21Natalie Starkey?

  Okay.

• 17:22Eugene Mirman?

  Yeah, but she's more like the scientists in Thor.

• 17:27Speaker 03

  Now, if the volatile stuff had not been decommissioned, what was your hypothesis of what you would find among that material?

• 17:37Natalie Starkey?

  Good question. I like this one. Well done.

• 17:50Natalie Starkey?

  Okay, so I-

• 17:51Neil deGrasse Tyson?

  I want to get "good question."

• 17:55Natalie Starkey?

  I explained at the beginning that comets formed from this very early material in the solar system, the very earliest material from our sun. And it's all the earliest dust and gas. Now, we think that they formed really far away from the sun. That's where they're cold and they have a lot of ice in them. And we think the asteroids under the hand, the rocky bits that were left over from the planets, so the hot inner solar system stuff, formed in the inner solar system. But what stardust taught us is that we're a little bit wrong. There seems to be a bit of a continuum between comets in the outer solar system and asteroids, because we found basically little pieces of the inner solar system. Solar system within a comet. Now, this was a complete game changer. We didn't expect this.

• 18:40Natalie Starkey?

  And so it's really kind of led to a change in our thinking of how the whole solar system formed, how things were moving about over huge distances.

• 19:10Speaker 04

  Can I ask a question? I'm still having trouble picturing this. Like, is it like the dust? Is it like astronaut ice cream when you get it? Like, what, is it invisible to you when you're measuring it?

• 19:23Natalie Starkey?

  Invisible to the naked eye, yeah. But if we put it in one of our instruments...

• 19:27Speaker 04

  But you get it on slides?

• 19:28Natalie Starkey?

  Yeah, we get it on, like, literally one piece of dust on a normal glass slide you'd see in a biology lab. And I have to put it under a microscope. People always find this hilarious. And I use a little needle and a micro manipulator, literally just a little needle. And I have to bring it really close to the sample, and it shakes. And then you just attract the sample onto the needle. And then I have to move this and drop it onto a sample holder. It's ridiculous. I don't breathe when I'm doing this sample preparation. It's so stressful. And you can't, you know, sneeze, you'll just lose everything.

• 19:59Speaker 04

  But it's so cheap, I thought.

• 20:01Neil deGrasse Tyson?

  You could exhale, and the space dust lands on the ground somewhere.

• 20:05Natalie Starkey?

  And you'll never find it. I have, don't tell NASA, I have lost a few pieces.

• 20:11Eugene Mirman?

  Space dust, do you collect in your space airplanes?

• 20:14Natalie Starkey?

  It literally just depends how long you fly for. So they're up there anyway, doing other scientific missions, measuring environmental things, clouds.

• 20:25Eugene Mirman?

  That's just one of the things they do is collect the dust.

• 20:27Natalie Starkey?

  They just stick these little collectors on as a by...

• 20:29Eugene Mirman?

  And have you tried making them twice the size of whatever the size is?

• 20:33Natalie Starkey?

  There are two sizes, actually. They've got small ones, which are about this big.

• 20:36Eugene Mirman?

  Considered a third bigger size?

• 20:38Natalie Starkey?

  Yeah, but then the plane might not be able to take off, you know.

• 20:41Eugene Mirman?

  So how big are the collectors?

• 20:43Natalie Starkey?

  They're about, maybe, two foot, maybe, across for the bigger ones? Yeah, something like that.

• 20:50Eugene Mirman?

  So, yeah, two feet sounds impossible.

• 20:52Natalie Starkey?

  Yeah.

• 20:56Eugene Mirman?

  I understand now.

• 21:04Neil deGrasse Tyson?

  Before we break to segment two, I just wanna find out from you. If you make a solar system, we get that. And of course lately, we've been looking for other star systems with the Kepler telescope, which released a list of a thousand exoplanets recently. But one got headlines. And that was, they call it Earth 2.0.

• 21:24Natalie Starkey?

  Yeah.

• 21:25Neil deGrasse Tyson?

  So, tell us about Earth 2.0.

• 21:28Natalie Starkey?

  Okay, so I think this official name is Kepler 452b.

• 21:33Neil deGrasse Tyson?

  Boring!

• 21:36Natalie Starkey?

  So we call it Earth 2.0. So what we're looking for with exoplanets, because everybody wants to know, are we alone in our universe? Solar system, galaxy, everything. Is there anyone else out there? So we're looking for planets or exoplanets outside of our solar system that might be in that right area to actually contain life.

• 21:58Neil deGrasse Tyson?

  Like a Goldilocks zone or something?

• 21:59Natalie Starkey?

  Exactly. It's not too hot, it's not too cold. And what we're really looking for is, does it contain liquid water on the surface? Because we believe that to have life, we need water. It might not be true, but in our current understanding...

• 22:15Neil deGrasse Tyson?

  But life as we know it.

• 22:16Natalie Starkey?

  Life as we know it, exactly. But I think if you start to think about all other forms of life, we can't really imagine it because we don't have any evidence for it. So we exist and all other forms of life on Earth have required water. So we think that we're looking for water.

• 22:32Neil deGrasse Tyson?

  Okay, so it's in the Goldilocks zone, but that shouldn't be enough to make it Earth 2.0, right? What else was true about it? There was champagne on it.

• 22:43Neil deGrasse Tyson?

  Just a guess. I mean, about its size or...

• 22:46Natalie Starkey?

  Yeah, so we believe that we need to be kind of Earth-sized in order to...

• 22:51Neil deGrasse Tyson?

  To have Earth-like life.

• 22:53Natalie Starkey?

  Yeah, exactly.

• 22:54Speaker 04

  Do you agree? I'm like, water and size? Like, that's us being like, we know what life is, right? I'm like, that's...

• 23:03Neil deGrasse Tyson?

  I like the little body as...

• 23:07Natalie Starkey?

  Yeah, it's tricky, right? I'm not sure. I'm kind of thinking, well, maybe we shouldn't limit ourselves with just our imaginations. Maybe we're just not good enough, you know?

• 23:17Speaker 04

  Like, we don't know what aliens drank or whatever.

• 23:22Eugene Mirman?

  But if we found water, it would be pretty likely that there would be life? Or...

• 23:27Neil deGrasse Tyson?

  I saw a New Yorker comic-

• 23:28Eugene Mirman?

  Have we found a place with water? Is there a lot of water in space? There is?

• 23:30Natalie Starkey?

  Yeah.

• 23:31Neil deGrasse Tyson?

  There was a New Yorker comic-

• 23:32Natalie Starkey?

  I don't know, like, it's unreal.

• 23:33Neil deGrasse Tyson?

  Where a flying saucer crash-landed and these aliens are- And it was like in the desert, right? And these aliens are crawling out of the crashed saucer. And one of them says, "Ammonia, ammonia."

• 23:45Natalie Starkey?

  Exactly, exactly. And actually, we have, um, what we call- I do like the word "extremophiles." So we've got certain bugs, essentially, on Earth that like really bizarre environments that we can imagine surviving at. So you've got them surviving at huge pressures and depths where there's no light source or- And so, basically, we're discovering these bugs that actually can survive in space as well. Um, they do experiments on the International Space Station. Where they take some of these bugs, some of them come from a cliff in Iceland. There's some weird bugs that live on this cliff. And it so happens that they can survive in space, on the side of the space station. Now, we couldn't. If you put us out there, we wouldn't survive.

• 24:29Natalie Starkey?

  Not only because of the vacuum and everything else, but there's too much radiation in space, which is the main issue for any living cells. So, I think, you know, we shouldn't limit ourselves. Although, you know, we have to have a theory that we can test, so-

• 24:44Speaker 03

  But life as we know it, we might be surrounded by life as we don't understand it.

• 24:47Natalie Starkey?

  Hmm.

• 24:48Speaker 03

  We might, right now, be surrounded by things that are alive. We have no, like, uh-

• 24:52Eugene Mirman?

  Wrap it up, hippie.

• 24:55Natalie Starkey?

  Are you talking about, like, wormholes?

• 24:57Speaker 03

  Theater chairs. Theater chairs could be living beings that survive on farts.

• 25:06Neil deGrasse Tyson?

  Theater chairs surviving on flatulence.

• 25:08Speaker 03

  They're out there.

• 25:09Natalie Starkey?

  Methane.

• 25:10Eugene Mirman?

  Yeah.

• 25:12Speaker 03

  There must be a reason for it.

• 25:12Eugene Mirman?

  Explain Broadway any other way.

• 25:16Neil deGrasse Tyson?

  I can't rebut that hypothesis.

• 25:22Neil deGrasse Tyson?

  That was not, that was an accidental pun. So Natalie, you not only worked on the Stardust mission, you couldn't stay away, and you were a principal scientist on the Rosetta mission to yet another comet where we landed on a comet. I say "we", it was the European Space Agency, not NASA, okay? You mean mankind.

• 25:49Neil deGrasse Tyson?

  So, tell us about that. That made very good headlines here, even stateside.

• 25:53Natalie Starkey?

  Yeah, I feel...

• 25:54Neil deGrasse Tyson?

  So congratulations on that. First time we've ever soft landed on a comet.

• 25:57Natalie Starkey?

  Yeah, it's amazing. Yeah!

• 26:02Neil deGrasse Tyson?

  So Rosetta is the name of the mission, and then the probe that went down was named...

• 26:05Natalie Starkey?

  Philae.

• 26:06Neil deGrasse Tyson?

  Philae. So where do we get these names from?

• 26:09Natalie Starkey?

  So these names actually come from Egypt. So they always try and name missions interesting names, and I think they were looking for something interesting. The aim of the Rosetta mission was to unlock the secrets of the solar system. Quite a big subject.

• 26:24Neil deGrasse Tyson?

  You said earlier that comets hail from the beginning of the solar system.

• 26:26Natalie Starkey?

  Exactly.

• 26:27Neil deGrasse Tyson?

  Understand them, we got some clues.

• 26:28Natalie Starkey?

  Exactly. So they kind of wanted an analogy for unlocking secrets. And actually, the Egyptians used hieroglyphs. But we didn't understand how to read this language that they used. But it was the Rosetta Stone that was found in Egypt that actually had all the languages on, plus a couple of other languages that we could understand what the hieroglyphs meant. So that's the Rosetta Stone. So it's basically unlocking the secrets of Egypt. But in relation to that, the Philae is an obelisk.

• 26:56Neil deGrasse Tyson?

  P-H-I-L-A-E.

• 26:58Natalie Starkey?

  Correct, yeah.

• 26:58Neil deGrasse Tyson?

  Philae.

• 26:59Natalie Starkey?

  So this is an obelisk, so just a really tall, needle-like statue. I don't know why they made them, but this also had some of this language on. And it helped us with the Rosetta Stone to unlock the secrets. So you needed both of them. And actually, you can go and see this. It's in the UK. I think we kind of stole it from Egypt.

• 27:18Neil deGrasse Tyson?

  Kind of, yeah.

• 27:19Natalie Starkey?

  So, but you can go and see it.

• 27:21Neil deGrasse Tyson?

  Through war or borrowing?

• 27:23Natalie Starkey?

  I think we borrowed, borrowed, yeah. That's very you guys.

• 27:29Natalie Starkey?

  So yeah, you can go and see it in Dorset in the UK. There we go. Look it up.

• 27:34Speaker 03

  That's probably what they had in mind when they built it.

• 27:36Natalie Starkey?

  Yeah, exactly.

• 27:38Speaker 03

  Dorset?

• 27:38Natalie Starkey?

  Yep.

• 27:40Neil deGrasse Tyson?

  So you, uh, so the name of this comet was what?

• 27:44Natalie Starkey?

  Okay, so the comet is called 67P Churyumov-Garasimenko.

• 27:50Neil deGrasse Tyson?

  So presumably named for the two discoverers.

• 27:52Natalie Starkey?

  Yes.

• 27:52Neil deGrasse Tyson?

  And that sounds very Russian, I presume.

• 27:54Natalie Starkey?

  Um, they aren't Russian, I forget now.

• 27:56Neil deGrasse Tyson?

  Well, they're not Russian.

• 27:57Natalie Starkey?

  No, I think Ukrainian.

• 27:58Neil deGrasse Tyson?

  Ukrainian.

• 27:59Natalie Starkey?

  I'm gonna go with. Oh, I...

• 28:00Neil deGrasse Tyson?

  Touchy subject.

• 28:01Eugene Mirman?

  I did it, it sounded a little satellite country to me.

• 28:08Natalie Starkey?

  This is normal.

• 28:08Neil deGrasse Tyson?

  Touchy subject.

• 28:09Natalie Starkey?

  We name comets after their discoverers, so... But they also get, um, a code. So we tend to call it 67P because, um, their names are quite long and hard to pronounce. I maybe just completely pronounced it wrongly, sorry if I did.

• 28:22Neil deGrasse Tyson?

  So Churyumov-Garasimenko.

• 28:25Natalie Starkey?

  Yeah.

• 28:25Neil deGrasse Tyson?

  Yeah, okay.

• 28:28Neil deGrasse Tyson?

  Just checking. So you were responsible for the Ptolemy instrument?

• 28:32Natalie Starkey?

  Well, I can't really take the credit, so I should just explain. With space missions, and I'm sure many of you know, they take a huge amount of time to plan, and then to launch and get to their object in space, wherever it is, takes quite a bit of time. So the Rosetta mission was planned over 20 years ago. So, you know, I was at school at the time, so I obviously wasn't involved in the mission then, I wasn't some whiz kid, so unfortunately. Um, and then it launched 10 years ago. And the problem is, over this huge timescale...

• 29:03Neil deGrasse Tyson?

  So all the people who designed it, they're dead now, and so a whole next generation...

• 29:07Natalie Starkey?

  Or retired, exactly. We need to bring young people in.

• 29:09Speaker 04

  Make way for you.

• 29:10Natalie Starkey?

  Yeah. So I kinda helped. So I didn't design it.

• 29:14Neil deGrasse Tyson?

  Okay.

• 29:14Natalie Starkey?

  But, um, so I can't take the credit.

• 29:15Neil deGrasse Tyson?

  But you should be designing something now, so that when you're dead, someone else will come in and do that.

• 29:19Speaker 04

  I know, were you involved in their death?

• 29:23Eugene Mirman?

  Yeah, do scientists kill and then take the place with the people they kill?

• 29:27Speaker 04

  Just to get on experiments? That's scary, that's hard.

• 29:31Natalie Starkey?

  That would be scary, yeah. No, I know.

• 29:33Eugene Mirman?

  Thank you for not answering and avoiding...

• 29:36Speaker 04

  I love that, that's mysterious.

• 29:38Eugene Mirman?

  No! But also know your day is coming.

• 29:42Speaker 04

  Right.

• 29:46Neil deGrasse Tyson?

  So it was launched in 2004, it took 10 years to get there.

• 29:49Natalie Starkey?

  It did, yes.

• 29:50Neil deGrasse Tyson?

  But it seems to me it shouldn't if you gave it enough fuel, so what was going on?

• 29:54Natalie Starkey?

  Yeah, so I mean, this is one of the problems. When we launch things into space, it is expensive because we need a lot of fuel. So we try and make everything very small. We try and miniaturize instruments so that they're light and they're small so that we use less fuel. But part of the problem with the Rosetta mission is that this comet was really, really far away, so...

• 30:12Eugene Mirman?

  How far away?

• 30:13Natalie Starkey?

  Well, it actually, the spacecraft went on a journey of over 3.4 billion kilometers. Now, when it was really far from the sun, the solar energy at that time is just, is none effectively. So you have massive solar panels on the Rosetta orbiter.

• 30:30Neil deGrasse Tyson?

  When you say massive, you mean large?

• 30:31Natalie Starkey?

  Yeah, so they're about the same...

• 30:33Neil deGrasse Tyson?

  Not literally massive, you want them as light as possible. No, it matters here!

• 30:36Natalie Starkey?

  Yeah, yeah, yeah. So they're about the same...

• 30:39Neil deGrasse Tyson?

  She didn't mean ma... Because we're talking about the mass of the spacecraft! You can say massive panels, they're like big panels!

• 30:44Eugene Mirman?

  It's gonna be fine, Mr. Literal.

• 30:46Neil deGrasse Tyson?

  Okay, fuck!

• 30:53Eugene Mirman?

  But I do think she means large.

• 30:54Neil deGrasse Tyson?

  Okay.

• 30:55Natalie Starkey?

  Okay. They're about the same size as an A320 plane. They're like, you know, a smallish plane, but still can fit in like 200 people, so quite large. But, the problem we have is...

• 31:08Neil deGrasse Tyson?

  A320 is like a Boeing 737.

• 31:11Natalie Starkey?

  Oh, I'm sorry. I'm sorry!

• 31:14Neil deGrasse Tyson?

  This is America!

• 31:21Neil deGrasse Tyson?

  Welcome to the United States. Go on.

• 31:23Eugene Mirman?

  It's like 1 million Yorkshire puddings!

• 31:29Eugene Mirman?

  Now I know what you mean!

• 31:32Natalie Starkey?

  I've lost my train of thought. Where are we going with this?

• 31:34Neil deGrasse Tyson?

  Where are we going? So, highly extended solar panels.

• 31:37Natalie Starkey?

  Yes.

• 31:38Neil deGrasse Tyson?

  Because it's far away and it needs...

• 31:39Natalie Starkey?

  It's far away, so it needs to be...

• 31:40Neil deGrasse Tyson?

  And they're very, very heavy.

• 31:41Natalie Starkey?

  They need to be large enough so that they can take every single bit of solar energy that they can get. But, what we had to do during this time is also shut down most of the spacecraft. It went into hibernation for about three years because it just, it didn't want to use up power and it didn't need it. So then we had a whole waking up procedure, which was very scary. They didn't know it was gonna wake up. It literally had an internal alarm clock on it that was set on launch. And it was just ticking away, waiting for this wake up time.

• 32:10Neil deGrasse Tyson?

  It had one job in life, to wake it up.

• 32:12Natalie Starkey?

  Thank goodness it worked, and there was no backup for that. So if it hadn't worked, mission would have been over.

• 32:16Neil deGrasse Tyson?

  But that doesn't account for why it took 10 years to get there.

• 32:19Natalie Starkey?

  Okay, we can't just take off from Earth and go directly to a comet. What we need to do is get onto the same orbit as the comet. And I think we just explained earlier that comets have a different orbit to all the planets. So what we actually had to do was be a bit ingenious with it and use some of the planets as gravitational slingshots. So this means just getting close to a planet, and we went around Earth three times and Mars once, to just build up velocity to get out on the right trajectory. So it's kind of like using gravity to get some power for free.

• 32:56Neil deGrasse Tyson?

  You're stealing orbital energy from planets.

• 32:59Eugene Mirman?

  And then you send it to where the comet will be in like 10 years, basically.

• 33:03Natalie Starkey?

  Exactly, so I mean, they had to do all this math to figure out, sorry, math. I apologize. We just used the one.

• 33:13Neil deGrasse Tyson?

  Because America, math is singular in America. Or non-existent, one of those two, yeah.

• 33:40Neil deGrasse Tyson?

  Natalie Starkey, visiting from the UK, expert on comets. Welcome.

• 33:46Neil deGrasse Tyson?

  So Natalie, you were a principal scientist on the Rosetta mission. You gotta give it up for Isaac Newton's law of gravity here. Because here, we're launching something, correct me if I'm wrong, as I followed what you were saying. We are launching a spaceship from a moving platform called Earth, doing a three cushion pool shot around three planets, Earth twice, Mars once.

• 34:12Natalie Starkey?

  Earth three times, Mars once.

• 34:14Neil deGrasse Tyson?

  Arriving where a comet will be 10 years from when that launches.

• 34:20Natalie Starkey?

  Yeah.

• 34:20Neil deGrasse Tyson?

  That's badass, that's...

• 34:22Natalie Starkey?

  That is badass, yeah.

• 34:25Neil deGrasse Tyson?

  If Isaac Newton were sitting right here, his head would explode.

• 34:31Neil deGrasse Tyson?

  Because one of the greatest first uses of his equations of gravity were to predict the future arrival of what would come to be known as Halley's Comet. So comets and his laws of motion and gravity have important history in the in the birth of physics, modern physics.

• 34:50Natalie Starkey?

  It's amazing. I'm amazed that they can do this. You know, it's just, it's so clever. And then they caught up with this thing, which is speeding along and entered into orbit around this body. Now, the thing is, it's small. It's about three by five kilometers in size. I don't know that in miles, but you can guess it's not particularly big.

• 35:10Eugene Mirman?

  It's an enticket of space.

• 35:14Natalie Starkey?

  So bodies this small don't have a lot of gravity associated with them, almost none, in fact. So trying to orbit around this thing is not trivial. Basically, you have to be quite close before you can enter into orbit. So they had to do a lot of powered flight around it in a complicated motion to actually map this thing. So they had lots of cameras on the orbiter taking pictures of the entire 100% of the surface of this comet. So it's really well documented.

• 35:42Neil deGrasse Tyson?

  Plus, you have to know where you want to land, filet.

• 35:44Natalie Starkey?

  Well, that's exactly why we needed to document it. So some of the images, one pixel on the image was just 75 centimeters. So we've got the resolution that we call that. It is absolutely amazing. We've not got that really anywhere.

• 35:56Neil deGrasse Tyson?

  So one pixel is like this big on the...

• 35:58Natalie Starkey?

  Yeah.

• 35:59Neil deGrasse Tyson?

  That's pretty good.

• 35:59Natalie Starkey?

  It's really, really good. That would be the best one. So they had to come very close to the surface in order to do that. Now, there's dangers coming very close because, you know, there's material flying off this comet. It's active as it's approaching the sun.

• 36:11Neil deGrasse Tyson?

  We saw Armageddon and Bruce Willis trying to plant the explosion on the comet as it was heating up.

• 36:17Natalie Starkey?

  Yeah, that was an asteroid, but yeah.

• 36:19Eugene Mirman?

  But he was a very good...

• 36:24Natalie Starkey?

  But same thing. They're also active in some ways.

• 36:27Neil deGrasse Tyson?

  No, it was a comet. I'm telling...

• 36:29Natalie Starkey?

  Was it a comet? I thought it was an asteroid.

• 36:30Eugene Mirman?

  I think it was an asteroid, no?

• 36:31Neil deGrasse Tyson?

  Yeah, no, it's a comet.

• 36:32Eugene Mirman?

  He was very good at digging, though, right? That was what we...

• 36:34Neil deGrasse Tyson?

  Yeah, that's why they got him.

• 36:35Eugene Mirman?

  ...in space. He was like the best at digging.

• 36:37Natalie Starkey?

  He's, yeah.

• 36:38Neil deGrasse Tyson?

  Yeah.

• 36:39Eugene Mirman?

  And anyway, it did well. It's fine.

• 36:42Neil deGrasse Tyson?

  Wait, wait, so, um, okay, so presumably you didn't go to destroy it, you went to study it.

• 36:50Natalie Starkey?

  Exactly.

• 36:50Neil deGrasse Tyson?

  So what did you find?

• 36:52Natalie Starkey?

  Okay, so, um, we found out it's a huge amount. I'll try and summarize it briefly here because we're still getting data back at the moment. So the orbiter is following this comet still. It's gone very close to the sun, as close as it will go. We call that perihelion when it's that closest point to the sun.

• 37:08Neil deGrasse Tyson?

  So now you have maximum heating?

• 37:09Natalie Starkey?

  Yep, we've had...

• 37:10Neil deGrasse Tyson?

  So you get...

• 37:11Natalie Starkey?

  It's really active. Um, the orbiter is backing off. I think on the 25th of this month, it's backing off a little bit because it's going to be studying how the comet and this material that's coming off it interacts with the plasma of the sun. Now, this is something we don't know a huge amount about because we can't recreate these conditions on Earth. Um, we just can't have these plasmas.

• 37:34Eugene Mirman?

  Not even in like France where it's like, who cares what happens there?

• 37:40Speaker 04

  I love that.

• 37:41Neil deGrasse Tyson?

  Just to be clear, this is astrophysical plasma.

• 37:43Natalie Starkey?

  This is.

• 37:44Neil deGrasse Tyson?

  Which are charged, uh, very hot ionized gas, charged gas that responds to magnetic fields. And it's sometimes called the fourth state of matter. And yeah, it doesn't exist in natural states on Earth's surface, yeah.

• 37:57Natalie Starkey?

  And so what they're trying to understand is that tail of the comet, which as it's going away from the sun, the tail is obviously behind it. Um, the solar wind is coming out from the sun and it's hitting that tail. So they want to understand how the solar wind is slowed down by that tail of material. That's just the orbiter though. We obviously had the land as well.

• 38:15Neil deGrasse Tyson?

  I think it's cool that this mission is still in progress now.

• 38:18Natalie Starkey?

  It's still going, yeah.

• 38:18Neil deGrasse Tyson?

  Yes.

• 38:19Natalie Starkey?

  And until at least the end of the year, I think they've extended it even. So we've got much more data to come.

• 38:25Eugene Mirman?

  Will that ship eventually come back here with stuff?

• 38:28Natalie Starkey?

  No, it's just gonna stay with the comet, um, you know.

• 38:31Eugene Mirman?

  Will you ever send it into the sun or you'll just leave it out there?

• 38:34Natalie Starkey?

  There are plans to crash it into the comet.

• 38:37Eugene Mirman?

  Oh.

• 38:38Natalie Starkey?

  Yeah, so, um...

• 38:39Eugene Mirman?

  Ruin the comet? Then...

• 38:40Natalie Starkey?

  Yeah.

• 38:40Eugene Mirman?

  Ruin the comet?

• 38:41Natalie Starkey?

  No, well, we don't really know, but...

• 38:44Eugene Mirman?

  Will you learn something? Will it be like, are you crashing it because like now we'll know what it's like to crash into a comet? Or are you like, nah, [bleep] it?

• 38:53Natalie Starkey?

  Just because we can, you know. No, I think, you know, go out in a blaze of glory. But they're planning to do it because what they can do is they get really close, is take loads of images and analyze. They've got lots of instruments that can be on and transmitting data back to Earth. And it's the closest they'll get with those instruments.

• 39:09Neil deGrasse Tyson?

  Yes, crashing would be the closest you would ever get.

• 39:12Natalie Starkey?

  Pretty much.

• 39:12Neil deGrasse Tyson?

  Between an instrument and a cosmic object. Yes, just to clarify.

• 39:17Natalie Starkey?

  But I think, you know, once the mission is effectively over and the comet's getting really far away from the sun again and far away from Earth, we can't get the information back. So we might as well just, just.

• 39:27Eugene Mirman?

  Well, could you send it somewhere else? Like, how much can you direct it? Can you go like, you know what, actually, let's go?

• 39:31Natalie Starkey?

  It won't have enough power to do that, unfortunately. So it's just got to stay where it is.

• 39:35Speaker 03

  But it could go off into space for millennia and then become worshipped by some alien race, right?

• 39:40Natalie Starkey?

  It could be, yeah.

• 39:41Speaker 03

  Why not do that?

• 39:43Eugene Mirman?

  Yeah, but you need, you need. Can't we send it to an alien world to become a god?

• 39:47Speaker 03

  But, but I thought, I thought, am I wrong? Correct me, but if, if there's no resistance in space, there's no atmosphere, there's nothing to slow it down.

• 39:55Neil deGrasse Tyson?

  But it's now in orbit around a comet. Now you have to unorbit it around the comet and send it off somewhere. Everything takes energy.

• 40:01Natalie Starkey?

  Yeah.

• 40:02Neil deGrasse Tyson?

  Everything takes energy. And so just to back to your point, Eugene, because I can give a very serious answer to that. For essentially all of our planetary missions that go into orbit, there is a end of mission plan where you will then get data doing something that is in the process of destroying the craft. So when the Galileo spacecraft went to Jupiter, it's the end, the end days of it, we're crashing down through, plunging through Jupiter's atmosphere, getting data as rapidly as you can until it's crushed by the atmospheric pressures of the planet. So this is a, this actually has a, a storied past of what you do with spaceships when you're done with them.

• 40:43Eugene Mirman?

  I would love to be the one who crashes it, if that's possible.

• 40:48Eugene Mirman?

  Let England know.

• 40:53Natalie Starkey?

  But we haven't mentioned what else we found out. I should briefly mention also what the lander has found out. Because sure enough, we have loads of organic material on this comet.

• 41:02Neil deGrasse Tyson?

  As you expected.

• 41:03Natalie Starkey?

  As we expected, but we're confirming it's definitely there. And we're analyzing it still to try and understand how important it might have been in life on Earth.

• 41:13Neil deGrasse Tyson?

  Does its water match Earth's ocean water?

• 41:17Natalie Starkey?

  So this is the interesting thing, no, it doesn't. So we kind of thought, okay, we measure the water in our oceans, we know the composition. And we use isotopes to understand it's the composition of the hydrogen isotopes in the water. Water is obviously H2O. We measure the same isotopes in the comet, in the ices or in the comet, and compare them. And if a lot of comets crashed into Earth, bringing their water with them, we'd expect them to have the same composition in this isotope, but they don't. This one has a different composition. So we conclude from this that this type of comet didn't provide our water, or not a huge amount of it. It could have provided some of it and been balanced out by other compositions.

• 42:01Natalie Starkey?

  But it's still an ongoing theory. We can't really explain it, but we've only really been to a couple... Well, we've been to one comet and we've measured remotely the composition of some others with telescopes. So there's millions of them out there. I don't think we've really answered the question fully, but we know the composition of this one, which is a good start because, you know, we had no idea really before that.

• 42:23Neil deGrasse Tyson?

  In simple terms, what are the differences?

• 42:25Natalie Starkey?

  Okay, so basically, I'll go into this and you can stop me if I'm being confusing. But we have two isotopes of hydrogen.

• 42:33Neil deGrasse Tyson?

  Stop.

• 42:40Eugene Mirman?

  What's the difference between an isotope and not an isotope?

• 42:45Natalie Starkey?

  I've actually just lied a little bit. There's more than two, I'll come back to this, but we're measuring the relationship of these two. So an isotope is literally a type of an element. So just take hydrogen or oxygen. And it's basically got a different number of neutrons in its nucleus than proton. It's got the same number of protons, sorry, different number of neutrons, which gives it a different mass number. So we've got deuterium and we've got hydrogen. And hydrogen has a mass of 1 and deuterium 2. So we can measure the difference between these two, the ratio between them in different objects to try and compare them.

• 43:21Neil deGrasse Tyson?

  Just to highlight that further, so if we have more than one kind of hydrogen, and one is a little heavier than the other, they'll still make water, H2O, except one of the waters will be heavier than the other water.

• 43:34Natalie Starkey?

  Exactly.

• 43:34Neil deGrasse Tyson?

  Yeah, and so now you can say, if this puddle of water has more of these heavy hydrogens in it than another, then they can't have come from the same source. But once you are heavy water, you're always heavy water, is that correct? Okay, so it doesn't become lighter later?

• 43:50Natalie Starkey?

  They are stabilizer tapes, yeah. They're not... So isotopes, people talk about, like, you know, radioactive a lot, and you might associate that word with isotopes, but that's only the ones that decay and are unstable. The ones like oxygen and hydrogen are stable, so they stay the same over time.

• 44:06Neil deGrasse Tyson?

  Okay, so you're using this heavy hydrogen, which we call deuterium, to trace the water sources that exist on a comet or exist on the Earth?

• 44:16Natalie Starkey?

  Yeah.

• 44:16Neil deGrasse Tyson?

  And they didn't match up, so we're still clueless?

• 44:19Eugene Mirman?

  Could we drink the comet water?

• 44:21Natalie Starkey?

  You could, yeah, yeah.

• 44:22Eugene Mirman?

  And you'd be fine?

• 44:23Natalie Starkey?

  You'd be fine. I mean, if you took...

• 44:25Neil deGrasse Tyson?

  I think it would slow down, actually. It would slow down your metabolic process.

• 44:28Natalie Starkey?

  It is?

• 44:29Neil deGrasse Tyson?

  I read about...

• 44:30Natalie Starkey?

  So you'd get fat?

• 44:31Neil deGrasse Tyson?

  I haven't tried it. No, no.

• 44:33Eugene Mirman?

  You haven't drank water from a comet? And you call yourself a scientist?