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Dan Reisenfeld from the University of Montana joins us this week to talk about his work with three different NASA missions (Genesis, IBEX, and Cassini), and Jessi from Animal Wonders brings along Ginger and Maui the Green Cheek Conures!
Hosted by: Hank Green
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Hank: Hello and welcome to SciShow Talk Show, that day on SciShow where we talk to interesting people about interesting stuff.  Today, we're talking to Dan Reisenfeld, professor of physics and astronomy at the University of Montana, who has worked on a number of space missions.  

Dan: Yes.

H: Currently working on one, maybe two, kind of.

D: Three, actually.

H: Oh, jeez.  Right now, Cassini is in the news and I see also on your shirt.

D: Yes.

H: Which is a probe that has been hanging out around Saturn for a long time now.  When was the launch, it was in, like--

D: The launch was in 1997.

H: Oh my gosh.

D: And it took seven years to get to Saturn.  

H: And it's about to end its mission, which is why it's starting to be more in the news.

D: It is.

H: You've got two other missions that you're actively working on?

D: Right, yes.  Mhmm.  There's the IBEX mission, which stands for Interstellar Boundary EXplorer, and it's currently orbiting the Earth, but it's studying the region in space where our solar system ends and the rest of the galaxy begins.

H: So you say it's exploring the boundary--the interstellar boundary.

D: Yes.

H: But it's not really exploring it.  It's just looking at it.  Studying it.

D: Fair point.

H: Yeah.
D: Okay, yes, so--

H: But IBEX is a really good name, so let's not mess with it.

D: Yes.  Well, it's part of the Explorer program at NASA.  There's a lot of Explorers, starting with Explorer 1 way back in the, you know, the first thing that we did in space.

H: Sure, okay, yeah, yeah, yeah.

D: And it's been going on ever since, so there's one of the many explorer missions.

H: Cool.  And the other one?

D: The other one is Genesis, which is a discovery mission, and Genesis is--was actually launched in 2001 and it went into space and was stationed at a point between where the Earth's and the Sun's gravity cancel, called the L1 point.  It sampled the solar winds for two and a half years.  Basically, the solar winds came in and it had these collectors, which were deployed with a bunch of tiles on them, and solar wind particles, which travel at hundreds of kilometers per second, crashed into these tiles and embedded themselves in, and then the whole thing folded itself back up and came back to Earth.

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H: Oh, wow.

D: In 2004, and it was supposed to have a soft landing in the Utah desert.  Parachutes were going to be deployed and a helicopter was going to snatch it up out of the air, but then the parachutes didn't deploy.  It implanted itself into the Utah desert but, so--

H: So you just got a bunch of dust that you're studying.  Pieces of tile.  

D: Well, not--the pieces--the tile pieces were, they were fragmented.

H: Yeah.

D: But they were still in fragments and fortunately the solar wind imbeds itself so deeply into it that it's easy to distinguish between the solar wind and Utah.  They are shared with laboratories around the world and the idea is that you can do a much better job of figuring out the abundances of the elements that make up the solar winds in a ground-based laboratory than you can in space

H: Right.  

D: And the ultimate goal of the mission was to understand the primordial composition of our solar system because 99.9% of the mass of our solar system is in the Sun, so if you know the solar composition, then you will know the primordial planetary solar system.

H: So, I mean, you always hear like, like, the percentages of elements in the Sun.

D: Yeah.

H: You, like, it's this much hydrogen, this much helium, this much other stuff, and--but--

D: Yes, but we don't know how much molybdenum is in the Sun.  Say that three times fast.

H: Did you say molybdenum?

D: I did, molybdenum, and so the whole periodic table exists in the Sun.

H: Ri--does it?

D: Yes.  

H: Wait.

D: No, really.

H: Not the periodic--'cause there's a bunch of elements that we just made up.

D: Well, not the--okay, not the radioactive, unstable ones.

H: Yeah, yeah.

D: But up to uranium.

H: Yeah, all the (?~3:36)

D: Everything, yep, everything up to uranium is in the--any stable or anything that has a half-time that's life of more than like, a few billion years.

H: Right, bismuth is also, just because--

D: Yeah.

H: So you're finding, you're figuring out all the percentages of all the things, 'cause like, these atoms are getting thrown out of the Sun.

D: Right.

H: Whenever like, all the time.

D: Continuously.

H: Yeah.

D: At a steady, sort of, pace.  

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It's called a solar wind.

H: Yeah.

D: And it carries out with it everything.  The trick is, the reason I'm still employed, I don't do the analysis in the laboratory of the samples, I'm a solar physicist.  The abundances in the solar wind aren't quite the same as the abundances in the sun itself, and there has to be a correction made to understand the (?~4:20) between the sun and the solar winds and so that's where I come in is, I help interpret the laboratory results to under--to translate the solar abundances that they're measuring--sorry, the solar wind abundances that they're measuring to the solar abundance that ultimately is what they seek.

H: And then is there another person who then tries to figure out what the sun was like four and a half billion years ago?  Because I imagine the composition has changed.

D: It has not changed, not the outer surfaces of the sun.  Only the core of the sun is there change and there's no mixing with the core.

H: What?  There's no mixing?  

D: With the core.

H: The core of the sun does not mix with the outside of the--

D: No.

H: With the surface of the sun ever?  It must eventually.

D: Not in our sun, no.  Other stars maybe do have mixing all the way down to the convection--

H: Convection.

D: But our, we have a convection zone that goes about 30% of the depth of the sun and so the top 30% of the sun is mixed continuously, but then you go into the radiator zone, which is radiatively stable, meaning that it doesn't--it just is static and so all the fusion--

H: How the heck do you know that, Dan?

D: 'Cause I read it in a book.

H: And by you, I mean us.  

D: I took a course called--

H: Humans.

D: Humans, how do we know this?  Well, I mean, in a way, stars are very simple.  I mean, they start out as, as far as their behavior is concerned, they start as big balls of hydrogen and some helium and all the other stuff that I was just talking about doesn't really play much an effect in the evolution of the star, although it does to a certain extent, but for the most part, you just have a big ball of hydrogen and the only thing that distinguishes one star from another star for the most part is its mass.  

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How much hydrogen came together in the first place, and so then you just throw the laws of physics at it and let it evolve in a computer simulation.

H: Right, okay.

D: Or something, and then you figure it out.  Now, we do have ways of checking our models, though, because the sun does give out something called neutrinos, which are part of the nuclear reactions that occur in the core of the sun, and we can detect those neutrinos and the neutrino number, how many neutrinos we detect are related to these models and so we can--

H: Right.

D: Correct or check our models.

H: Be like, ahh, it looks about right.

D: Yeah.

H: Okay.  So, there's a layer of the sun that hasn't changed in four and a half--like the composition hasn't changed in four and a half billion--

D: Correct.

H: It's just hot.  It's not even fusioning.  

D: Right.  

H: Ahh.

D: You got it.

H: So you're doing that, but then--

D: That's Genesis, right, yes.

H: But then you've got IBEX.

D: Then there's IBEX.

H: We're gonna get to Cassini, I promise, but there's--it's also good to talk about things that people aren't necessarily talking about right now, and this is you're learning about the, basically the boundary between our solar system and then our not-our-solar-system anymore.  

D: Right.

H: Which is not necessarily an easy place to distinguish.

D: True.

H: And it is always like, I feel like every two years, people are like, Voyager has left the solar system, and I was like, that happened.   That already happened.

D: Right.  Yes, yes.  

H: But different--

D: In fact, the Voyager team, the scientists on the Voyager mission, which is still going on and still operating, and our team, the IBEX team, we interact quite a lot.

H: Right, because they're out there actually exploring and having some data.

D: It's the same--right, so you're getting single point measurements.

H: Right.

D: As they pshew, go through this interstellar boundary region, and it has different layers to it, which is why you hear different like, the first exciting thing that Voyager did was it got to what's called the termination shock, which is sort of a fancy word for the innermost layer of the boundary region.  Technically, it's a place where the solar wind goes from being supersonic to sub-sonic.

H: Okay.  So how do you study that layer without being there?

D: Well, um, so--

H: 'Cause IBEX is just orbiting Earth.

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D: IBEX is orbiting Earth.

H: Is it a space telescope?  Like, what is it?

D: Well, it's a telescope but it's not detecting light.

H: Not seeing light.  Okay.

D: Yes, it's looking at neutral, neutralized atoms.  We have a name for it, we call them energetic neutral atoms.  Basically, they're solar wind particles that went out as ions and then when they interacted with the interstellar gas, they became neutralized and their trajectories carry them around the magnetic field that's out there and they spiral around in that field.

H: When they're still ions.

D: When they're ions.

H: Okay.

D: And when they become neutralized, if they happen to be pointing in this direction when that happens, then they just travel in a straight line back to us.

H: So like, the moment that they're neutralized, they have sort of an equal chance of going in every direction.

D: Yes.

H: And some of them head back to us.

D: Right.

H:: And then you are detecting these energetic neutral somethings.

D: Atoms.

H: Atoms.

D: Yes.  

H: I mean--

D: We call them (?~8:52)

H: And so you can--what can you tell from them?  You can tell their trajectory, you can tell their--

D: Energy.

H: Their speed, basically, is that what you mean by energy?

D: Right, they--well, we measure their, right, we measure their energy, their kinetic energy, and we know where they're coming from and our instrument has different energy channels so that we can look at their energy distribution and also their density.  How many are coming tell us something about the density of the region that they are being formed in.

H: Right, and are you looking in all directions, not just--

D: Yes.  It takes six months for us to map out the whole sky once, and we make these sky maps of this boundary layer and it's been doing this since the beginning of 2009, so we're on our 8th sky map now.

H: And so you can--can you just see the sort of wake that's being formed as the sun plows through the interstellar medium?

D: Mhmm, right, yes, yeah, but it's kind of like imaging the skin of a bubble from the inside.

H: Right.

D: It's a very thin region of space compared to solar system scale and so we're still in fact learning how to interpret our data.

H: Right.

D: Because there's no dataset like it.

H: Is it a super thin region, like, like, all of these ions get neutralized roughly at the same area of space?

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D: Well, fro--on the scale of this region, yes, but it's still thick compared to say, the distance between the Earth and the sun.

H: Okay.

D: It's about, maybe 50 times, actually.

H: Oh, okay.  So that's a--

D: So it's still a pretty thick, beefy area.

H: Okay.  Fascinating.  How's Cassini?  

D: Just fine.  

H: What's your favorite Saturn moon?  

D: Enceladus.

H: Yeah.  Enceladus is, that's the watery one.  Is that the ice one?

D: Yes, well, it's the one that's spewing water out into space, yes.  Many of the moons have a lot of water on them.

H: But they--but is Enceladus like, 100% ice?

D: Not 100%.

H: Oh, okay.

D: But it's, it's, I mean, it has a rocky core.

H: Oh, right, but it, on the surface (?~10:47)

D: The surface is entirely encased in ice, yes.  

H: And there's some kind of probably salty ocean hanging out down there?

D: We think so now, yeah.  

H: And that's new Cassini information?

D: Yes, I mean, we've started--we basically knew something had--like that had to be going on with Cassini when Cassini discovered these plumes of water shooting out of the south pole of Enceladus in 2005.

H: Were you working on Cassini then?

D: Yes.  

H: Was that a good moment?

D: Yeah, no, that was fantastic.  I--I--I--the way, there's a really interesting story about how the water was discovered, because ultimately, we actually could make--take images of these plumes, but originally, it was the magnetometer team that discovered that something was up with Enceladus.  Up until Cassini, Enceladus was just one of Saturn's many moons and nobody particularly thought there was gonna be anything exciting going on there and then when we did a relatively close fly-by of Enceladus early in the mission, the magnetometer team noticed a bleep in their data that--they were measuring Saturn's magnetic field and for some reason, the field was being significantly distorted when it got near Enceladus and nobody expected that because in order to do that, magnetic fields to be affected need to be interacting with a plasma or something, so this implied that there was a plasma around Enceladus, a fairly dense plasma, and so that was like, hm, why would there be a plasma around Enceladus, and so then a couple orbits later, they redirected the Cassini spacecraft so that it made a much closer approach and then our instrument, which was or is an ion mass spectrometer, it detected the existence of lots of ionized water molecules right near Enceladus.

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Now we were seeing water molecules actually all over the place, but the density of water went way up when we got near Enceladus and so that was like, oh really, that's really interesting.  So we now know that there is a watery atmosphere around Enceladus and then finally the cameras were able to detect these plumes coming.  There's fissures in the ice near the south pole and jets of water were shooting out of it like geysers, so it's like Yellowstone National Park.

H: And like, with enough velocity that they like, escape?

D: Oh yeah.

H: The moon.

D: Right, yes, yes.  

H: I mean, I guess it's not--

D: They're very high speed of like, 200km/sec.

H: Wow.  So then it shoots out and it hangs out around the planet and then does it, like, the solar wind, like, plasmafy it somehow?  Is that why it's interacting with the magnet field of Saturn?  

D: Well, when it shoots out, it's neutral, you're right, and then it gets ionized because Saturn has a very strong magnetic field and it has--Saturn has what we call a magnetosphere, which is a region of space--the Earth has a magnetosphere and Jupiter has a magnetosphere, those are the three big ones in our solar system, and it's a region where the magnetic field of the planet traps ions and electrons and these ions and electrons can become very energetic and they can ionize neutral atoms, and so once the water shoots out from Enceladus, mostly electrons will hit these water molecules and ionize them, and so then they become ions.

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H: And that was our first clue that there was maybe a liquid ocean?

D: Well, obviously, there's neutral, I mean, you know, well, yeah, neutral water coming out of it and so that implies there's a heat source and that it would be liquid somewhere.  At first we didn't know if there were little pockets of water or if it was something more, you know, moon-wide, but later analysis of gravit--they can determine the strength of gravity.

H: Right.

D: Around the moon and this led them to infer the existence of a whole ocean underneath the surface.

H: Because ice, ocean, rock.

D: Yeah.

H: You can sort of tell the density and so you're guessing that something is bringing the density up, so it's not just water.  

D: Correct, yes.  

H: I don't know that we know that much about how the solar system as a whole formed and then, you know, the systems around the gas giants of these big interesting moons, how they formed, but it seemed like they probably formed around the same time as the planets.  It's interesting to me that there would be some that are so like, that their compositions are so different and that there would be one that is, and this is the case for Jupiter, too, that it's just like, way more water than all the rest of them.

D: So you mean Enceladus has way more water?

H: Than all the rest of the Saturn moons.

D: Actually, we don't know that.  I mean, a lot of them--water is very abundant in the solar system, it turns out, and I mean, what makes Enceladus special is that it's active in such a way that the water is in a liquid state.  Other moons also have a lot of water.

H: Is--there is a lot of ice hanging out, but it's these ice ball, like these snowball moons that are just like, it seems like they're mostly water.

D: Well, yeah.  Yes, and I don't know about enough planetary formation to explain why some have so much more than others.

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But even Titan has a lot of water on it, it's--but Titan is so cold that the water is basically in a rocky state.

H: Right, it's rock, yeah, yeah, just like Pluto, and it's like rocky, sandy rock.  Well, I feel like we could talk all day.

D: Sure.  

H: But, I would also like to introduce you to some kind of animal.

D: Okay.  

H: I don't know what it is.

D: Okay.

H: I feel like I've heard a bird, so it might be that.  

D: Alright.

H: Two of them.

Jessi: Yeah.  

H: There is two of them.

D: They're birds.

J: We've got two.  And you did hear right.  These guys are birds.  This is Maui, would you like to hold her?  You can give her seeds all you want.  So these guys are both green cheek conures, but you can see they look--

H: Yeah.

J: --similar but different colors, so this is Ginger here, is the natural coloration and this is what you'd find in the wild.

H: So this is a weird coloration, 'cause it's--

J: Just tons and tons of seeds.

H: --not green cheeks.

J: So yeah, so she has the green cheeks and you can see she does have green cheeks, they're just a lighter green, so if she was born in the wild, she would not--

H: Where you going?  

J: Come here.  She would not survive.

H: Aw man.  It's okay, there's Mommy, there's Mommy.

J: Hi.  Come here you.  Do you wanna be on my shoulder?  

H: Okay.

J: Safety.  

D: She would not survive.

J: She would not survive, because she'd be like a really big neon sign saying 'eat me', right?  So she, she does not have a naturalistic coloration, so she would not pass on--there would be a very low probability of her passing on her genes and making more of these, but since she was born in captivity, she survives and we can get these really interesting color mutations.  I think there are six different color mutations of the green cheek conure.  The reason we get them is the--were able to get the mutations is because these guys are really prolific breeders and they do well in captivity, and so people, you know, they have them as pets and you know, they're small, they're quiet, relatively quiet for a parkeet.

H: For a conure, yeah.

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J: They're pretty docile and I'm gonna say that and anyone in the--that's watching this that has one are gonna be like, no, mine (?~18:07) all the time, because they can.  They can be quite bite-y when they're young.

H: They got strong jaws and pointy beaks.  

D: I like their eyes.  The white around their eyes.

J: Isn't that neat?  Yeah, so conures have that bare skin around their eyes like that, so do you know, Hank might know, do you know the difference between a parrot and a parakeet?  

D: I used to.

J: Yeah?

D: But I don't know anymore.

J: Do you know?

H: Oh gosh.

D: They're bigger.  Parrots are bigger.

J: No, false.

D: Oh, see.  Stick to my field.

J: So there are--the smallest parrot in the world is the pygmy parrot.

D: Really?  Ohhh.

J: It's about this big.  The parrot (?~18:42) is the second smallest and it's about that big, so, and then there's big parakeets.

H: Right.  Uhh, I can't remember.

J: It's their tail.  

H: Okay.

J: It's their tail, so if they have a long tail, it makes them a parakeet.  If they have a shorter tail, it is--they're a parrot.

D: Oh wow.  

J: So these guys are a parakeet from South America, so we call them a conure.  So, they're often called green cheek conures or green cheek parakeets.  You wanna do a little dance?  Yeah!

H: Ohh, that's quite a dance.

J: Yeah.  

H: It's funny when I--so I have a child now, and I'm always looking at animals and I'm like, okay, that's smarter than my child.

J: Yes.  Yes.  

D: (?~19:23)

H: At this point.

J: At this point, right.  Right, so like, a one to two year old, that's kind of where we're at with these guys.  I mean, if you can equate different species.  

H: Right, yeah.

J: But if you notice, I'm holding them different.  So I was having you hold Maui and you can see that she perches really well with her feet.  See what's wrong with Ginger's feet?

H: Oh yeah, you don't have any claws.

J: Yeah, so I am assuming her parents groomed them off of her.  That's what I think is what happened.

D: Her parents?  You mean her actual--

J: Her actual parents.  Not her owners, yeah.  

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