Planetary Radio: Space Exploration, Astronomy and Science - Analyzing Alien Atmospheres

Episode Date: April 7, 2008

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How's the air up there? Exoplanet Atmospheres, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. This week that final frontier is 63 light years away, where water and methane have been found in the atmosphere of a planet circling another star.

Our guest is Mark Swain, leader of a team that has just announced discovery of the first organic material on a so-called exoplanet. Bill Nye, the Science Guy's commentary says we can start saving up for a ticket to space, while Emily Lakdawalla's Q&A explains why virtually every large object in space

is round like a U-head, as Columbus once told Bugs Bunny. We'll wrap up the show with Pluto plasma and edible space debris shared with our friend Bruce Betts, who will share his and our view of the night sky and a new space trivia question. Mars is at the top of our headline review. If you dig the red planet, you'll probably like the extensive report on Spirit and Opportunity

by my colleague, A.J.S. Rail. It's at planetary.org. You'll learn that Spirit is weathering her third Martian winter in better than expected fashion, while Opportunity continues to explore the vicinity of Victoria Crater. And both rovers are safe from what appeared for a few days to be a major budget challenge. By the way, we expect Steve Squires, the Mars Exploration Rover Principal Investigator, to be our guest on next week's show. Turning to Earth's other next-door neighbor,

Emily Lakdawalla's space blog reports that the European Space Agency's Venus Express is still looking for signs of volcanoes under the thick clouds of second rock from the sun. That's at planetary.org as well, naturally. NASA has decided to push back the next space shuttle launch, but just by a few days. Delivery of the big external tank was delayed by all the bad weather the eastern U.S. has been suffering through. Discovery is now scheduled to lift off on May 31st with a big Japanese module for the increasingly international International Space Station. Here's Bill Nye. Hey, hey, Bill Nye, the planetary guy here, vice president of Planetary Society.

For many years, I applied to be an astronaut. I wanted to fly in space and show my viewers the world below them. Well, now people are selling tickets to fly in space. These are not $20 million rides with the Russian Space Agency. No, these are $200,000 rides. That's a factor of 100 cheaper. And you say, how popular could that be? Who's got $200,000?

Well, my friends, over 1,500 people have signed up for this ticket with spacecraft developed by Scaled Composites and funded by Virgin Galactic, which is based on Virgin Airways, which I guess is based on the Virgin Islands. It's in the spirit of exploration. So these people who buy these tickets will get what they say is five minutes in space. That's five minutes of black sky. And many, many seconds of those five minutes are going to be in weightlessness, zero G. And when you look down, you will not see a big expanse like a nice flat map you might put on your desk or dashboard.

No, you will see the curve of the earth below you. So it is to be presumed that these people's perspective of our planet will be changed forever. And then perhaps they will live and work among us and change us all through the spirit of exploration by flying in space. It's a remarkable time to be alive. The price has come down by a factor of 105 years. Who knows what will happen in the next 10? Well, thanks for listening. Bill Nye, the Planetary Guy, here on Planetary Radio. It's mind-boggling, really. How can we be learning so much about faraway planets no one has actually seen? The count is way over 200, and last summer a team of scientists announced that they had found water vapor in the atmosphere of one of these exoplanets.

Now we hear from the journal Nature that this same gas giant, circling a star 63 light-years away, has methane. My colleague Amir Alexander wrote a great article about this a couple of weeks ago. We'll link to it from planetary.org slash radio. Methane isn't much of a molecule really, but it is organic. And under the right conditions, you can end up with amino acids, the so-called building blocks of life. JPL research scientist Mark Swain led the team that made this discovery. I traveled to the big NASA lab just a few days ago so that I could sit down with Mark and learn more. Mark, I'm glad we could get together to talk live here once again at JPL, where so much of the action takes place. And it was only a few weeks ago that you guys had this

article that appeared in Nature that had more to tell us about this very romantically named exoplanet, HD 189733 b, which we learned last summer has water vapor, and now we find it has organics. That's right. What we've just detected is the presence of methane together with the water vapor, and that's really exciting because this is a stepping stone to what we'd really like to do, which is to study organic molecules on planets where life could exist. Now, I want to be clear from the outset, this is a really hot planet and there's no life here. But it's a very important demonstration of the techniques that we'll use

to study the types of planets which might be more hospitable. This is a crazy place. I mean, it's bigger than Jupiter. It's ridiculously close to its star. It goes around it in 2.2 days. I mean, no wonder it's hot. That's right. If you were to stand on – well, you'd actually have to float in a balloon because there's probably no surface as we know it on this gas giant.

But if you were to be on 189733B and look up into the sky, the sun would be about 15 degrees across. So that's kind of like holding up your arms at arm's length and that's about the diameter of two and a half basketballs. If this planet hadn't been found, would we be far enough along? In other words, are these characteristics of this little solar system so special that they've allowed us to make these discoveries sooner than we might have otherwise? Well, yes and no. And there's a subtlety here. This is the best target to study. It has a very deep transit.

It's close by. It's a bright star. So it has many characteristics that make it easy to observe. But one of the really exciting things we learned from these observations is that the Hubble Space Telescope today has enough sensitivity to make similar types of measurements for about a half dozen exoplanets. Wow. And that's really exciting. We're looking forward to starting that process. And when you say we, you are part of a team. In fact, you were just on the phone to London a few moments before we spoke to one of your colleagues. That's right.

Giovanna Tienetti, who's our theorist who works on our team. And what she does is model the physics of how these atmospheres work. When we measure a spectrum, we actually have to use a model to figure out how much water there is, how much methane, what the temperature profile is. And so the physical modeling is an absolutely integral part of this team effort, and it is essential to making the results what they are. In spite of the fact that you're using some of the best instruments ever available to humanity, we're basically talking about good old-fashioned spectroscopy here. Absolutely. That is one of the

real breakthroughs in exoplanet science in the last, I want to say since 2004, a pair of papers by Drake Deming and David Charbonneau, which showed that infrared emission could be detected from these exoplanet atmospheres. And they did that with regular infrared cameras. And this really launched the whole field of kind of light curve analysis of emitted radiation. Now, we're making an absorption spectrum. And that's, again, there was a visible counterpart of this that was done by David Charbonneau clear back in 2001, 2002, and detected sodium in the atmosphere of 209458b, another famous exoplanet.

sodium in the atmosphere of 209458b, another famous exoplanet. And so the application of existing instruments, just learning how to use them better, and this work has been done by a number of teams, has really given us tremendous observational progress in learning about these exoplanets. Det detection of molecules is really significant because molecules act as probes of the atmosphere, and they allow you to characterize the composition and the conditions and the chemistry. All of a sudden, it's a whole new set of questions, and it's bringing us a much more detailed understanding

of what's going on on these planets. You said absorption, which I guess is because we're really looking at the light or the heat from this star as it interacts with the atmosphere of this planet? That's right. This measurement was made during a transit. So from our point of view, during a transit, the planet seems to move across the stellar face. The orbit has a fortunate inclination, and so the planet crosses the parent star's face from the point of view of Earth. When that happens, the starlight filters through the planet's atmosphere right around the edges, around the limb of the planet. And what we do is we measure the absorption of the molecules that are in the planet's atmosphere as the starlight filters through.

You can also use one of these systems where the orbit has this fortuitous alignment. These are transiting systems. You can make the measurement as the planet goes behind the star. And that gives you an emission spectrum. So you take the difference of star plus planet and just star. You subtract off the stellar component. And that is, we're actually working on an emission spectrum for the same planet right now.

Wait a minute, that sounds like the making of another paper. We'll ask JPL scientist Mark Swain about that possibility when Planetary Radio continues in a minute. I'm Robert Picardo. I traveled across the galaxy as the doctor in Star Trek Voyager. Then I joined the Planetary Society to become part of the real

adventure of space exploration. The Society fights for missions that unveil the secrets of the solar system. It searches for other intelligences in the universe and it built the first solar sail. It also shares the wonder through this radio show, its website, and other exciting projects

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Our nearly 100,000 members receive the internationally acclaimed Planetary Report magazine. That's planetary.org. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Exoplanets, or extrasolar planets, they circle distant stars. We found almost 300 of them.

And astronomers and planetary scientists like Mark Swain and his international team are beginning to analyze their atmospheres. Mark is a scientist at the Jet Propulsion Lab in Southern California. He just mentioned before our break that his team is moving from transmission, or absorption spectra, to emission spectroscopy as they continue their research into a horribly hot yet revealing planet called HD 189733b. You alluded to more exciting news coming. I was going to bring this up until the end of our conversation, but could that have something to do with what you just said?

Yes, it does. The really exciting thing that we're working on in this next spectrum is localizing the molecular abundances. And so what a transmission spectrum does is it probes a very specific region of the atmosphere of the exoplanet, and that is the terminator region, the junction between night and day. Now, these are tidally locked planets, these hot Jovians, so they always have one side that faces the parent star.

And in that case, the atmosphere on that side, as we've already talked about, just gets an enormous amount of heat dumped into it. The atmospheres of these planets in some cases seem to circulate, move the heat around, they redistribute the heat, and so the night side is warmed by essentially the wind from the day side. The weather must be pretty amazing with that kind of temperature differential. Absolutely. Nonetheless, because one side is hotter and one side is colder, there are chemical differences you expect, particularly the carbon chemistry, the CO to the carbon monoxide to methane ratio can change and is in fact a – I'm sorry, the secondary eclipse spectrum localizes the abundances on the day side. So what we're going to be able to do is actually localize the abundance differences from the day side to the terminator region.

Help me with one term before we go into that one. You said secondary eclipse. Yes. Which means? The secondary eclipse is just when the planet goes behind the parent star. Oh, okay. And the transit or primary eclipse is when the planet goes in front of the parent star as viewed from Earth. So I don't know how much you're willing to say because this is a paper that has not yet been submitted, much less

published. And we're sensitive to that. But I'm assuming that this is going to be able to tell us more about the chemical makeup of this atmosphere. That is certainly our hope. Okay. All right. Well, we'll leave it at that and keep it general like that as well. And just the ongoing discovery of exoplanet after exoplanet is the fact that you guys are gradually filling in the Drake equation for us. And that, of course, this famous equation from Frank Drake that said, okay, here are the variables. Line them up, and eventually at the end, you've got life elsewhere in the universe. Well, I think that while that is true, this is just one small step in what's a much larger picture.

And I think that these particular results really anticipate the day when we're able to make the same sorts of measurements in planets which would be hospitable to life. That will probably require JWST, the James Webb Space Telescope. And even James Webb will start that job, but it won't finish it. But you can at least begin to look forward to the time when these instruments, like the James Webb scope with its gigantic mirror, are going to start to tell us things about terrestrial planets, planets that are like the one we live on. Absolutely. They'll be a little bigger, and they'll be around M stars. They won't be around G stars, so their stellar primary will be cooler, and that helps with the measurement because the contrast between the star and the planet is reduced, and the contrast ratio is really the

big problem here. It's not the absolute sensitivity. But James Webb will be able to do that science nicely. Hubble already has the sensitivity to study a Neptune mass planet around an M star. And there is one well-known one, which I'm sure a lot of people are looking forward to studying, and that's GL436b. I'm sorry, GJ436B. Not that I would have known the difference, but okay. Is there any chance that these are going to get better names than this? Oh, I'm not in charge of the naming department, and I'll be the first to admit that astronomers name their planets in a really boring way. What is intriguing about that Neptune-like planet that circles an M-class star?

Well, in this case, the planet is cooler. It has a dayside temperature that has been inferred from some infrared measurements with Spitzer, and it's about 700 Kelvin. So it's considerably cooler than the 1200 Kelvin dayside temperature of 189733b. It probably, that planet GJ436b probably has some type of surface. At least there's some theoretical modeling that shows that it might. So it's again a stepping stone, but it's taking us, measurements of that system will take us one step closer to really being able to look at a terrestrial-type planet in the habitable zone. I've got to come back to that topic of the research that is not as far off even as the James Webb telescope. Are you hopeful that we will be able to identify more complex molecules than methane,

which, after all, is fairly simple, organic though it is? Yes, I am. I think we're actually in the infancy of exoplanet spectroscopy. And there are a number of ideas out there among the cognoscenti which are really interesting and which essentially could be summarized along the lines of this Hubble result is really just the beginning of the show. There are ideas to use different instruments, to increase the sensitivity in various ways, to use Hubble in other ways. So there are a lot of ideas out there, and we're just at the beginning. We're about out of time. Any messages for the shuttle crew that's going up there to repair the Hubble before long?

Oh, well, thank you very much for your effort and hard work. Hubble is a fantastic instrument, and I really appreciate NASA keeping it flying. Mark, thanks so much, and congratulations, and we look forward to that next paper. Thank you very much. Mark Swain is a research scientist for the Jet Propulsion Lab here in, well, near Pasadena, California, and has led a team that has found, for the very first time, organic material, methane, on a planet circling a star other than our own. What could be more exciting than that? Well, what's up is pretty exciting.

Not quite as exciting, but we'll be here with Bruce Betts for our dose of the night sky right after this visit by Emily. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, Why are planets round? We have round planets rather than cube-shaped or lumpy ones because objects with a lot of mass, including not only planets but also stars and even large moons and asteroids,

become round under the force of their own gravity. The round shape is the shape that equalizes the potential energy felt by any point on the surface of a planet. On planets and stars that are made of gases and liquids, any piece of the planet that stuck out would immediately flow like water from the high place to the low place, evening out the surface into a round shape. Even when a body is mostly solid, such flow of mass from high areas to low areas does happen if you allow enough time. The 4-plus billion-year-old age of the solar system has been more than enough time to make round worlds out of places like Earth and Mars, the asteroid Ceres, and many of the large moons. However, as you get to smaller and smaller objects, like most of the asteroids, the smaller mass means a smaller force of gravity. Once you get sufficiently small, the internal compressive stress generated

by the weight of rocks at high elevations is just not big enough to overcome the inherent strength of the materials that make up the body. So the flow never happens and the body never becomes spherical. Metal and rock are both inherently stronger than ice, so this transition from round to lumpy worlds happens at much smaller sizes for icy bodies than rocky ones. For this reason, there are probably many more round Kuiper Belt objects than there are round asteroids. Of course, even the largest planets aren't perfect spheres. To understand why that is, tune in to next week's show. Got a question about the universe?

Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time for What's Up on Planetary Radio. He's here, the Director of Projects for the Planetary Society, Bruce Betts, to tell us about the night sky and do some other fun stuff. Hey, great conversation with Mark Swain, and I think we're going to be talking to him again soon. He's got more cool stuff. But I was at JPL, so I had to pick up stuff for you.

It's the best move they ever made was moving their store to the visitor center. So smart. You alone have made it an excellent place. They make a profit every month off of me, I'm sure. I put them over the top. I'm part of the margin. Check this out, okay? What did you get? We have to get this to Alan Stern.

Ludoplasma! That's for you. Here, take it. Oh, it's for me? Yeah, you can open it up. It looks awful, doesn't it? It's gross as heck. It's got like what looks like egg white in some other kind of liquid.

It's got a gelatinous mass. Yeah, thanks. I think it might be liquid oxygen, but I'm not sure. The hazard is ways. Something for Alan, something to look for when he gets to Pluto with New Horizons. There you go. And then I got us... I'm sure it's completely scientifically accurate.

I got us these, too. Astronaut space debris. Wow, space debris. They look remarkably like knockoff M&Ms. They do indeed. No, they're not. There's no M on them. They're knockoffs.

Clearly they're space debris. They're generic. Look at that. Well, keep interviewing people up at JPL. You bring food and toys. It's an old piece of the Soyuz right here. Gelatinous as masses. No.

You want one? No Soyuz right now. Thank you. I'm going to have some. I had some for breakfast. Tell us about the night sky while I eat some of these. Okay. The night sky.

Could you crunch a little louder? Sure. Okay, good. We've got Mars and Saturn visible in the evening sky, Saturn over towards the west, but still pretty high up shortly after sunset, looking like a kind of bright orangish star-like object. It is above Orion, if you think of Orion such ways, you can find it there. Then if you look farther to the east, still very high, but over towards the east you will see Saturn looking yellowish and in Leo, and not

far away, within three degrees of Saturn's brightest star, Regulus in Leo. So making kind of a nice pair. In the night sky and the pre-dawn sky, we've got Jupiter. Jupiter looking like an extremely bright star like object, low in the east, not long for dawn.

You can grab some more of those while I do this week in space history. I'll take a couple more. They're not really very good. But, you know, what do you expect from space debris? It's space debris. I mean, come on. Go for it. The thrill is that they might maybe be from space.

This week in space history, of course, 1961, Yuri Gagarin becomes the first human in space. 1970, Apollo 13 launched and starts their fun. And 2001, a Mars Odyssey is launched. Mars Odyssey is launched, still functioning fabulously in Mars orbit. Apollo 13, speaking of space debris, still stuff out there, translunar, right? Oh, I don't know. He was traveling along with them. There must be some crap that's still floating around up there from them.

You're eating it right now. On to Random Space Fact! And big news. Next week, be sure to tune in. I think we're going to start a new contest based on Random Space Fact

next week, so tune in. It's going to going to start a new contest based on random space fact next week. So tune in. It's going to be fun. It will indeed. When you go out and check out in a dark sky, unlike what we usually have here, you check out the Milky Way, looking like that milky band of stuff up there in the sky. If you look off in the direction of Sagittarius, you're looking towards the galactic center. And in fact, the galactic bulge, so it's actually bigger and brighter in that direction towards Sagittarius. We actually, in our continuing story of Professor Tyler Norgren as he travels around to national parks in the United

States, making connections to space in all sorts of neat ways and reporting on our website in Stars Above, earth below. You can check out some truly spectacular pictures he took of the Milky Way rising from Texas. I saw those. They're very beautiful. From incredibly dark, apparently, parts of Texas. I wanted to be with him so much. I want to be in those parks.

Good luck. Thank you. You're welcome. On to the trivia contest. We asked you, who was the first non-Soviet, non-American person in space? Non-Soviet, non-American. And how'd we do? We did well. We did well. Got lots and lots of responses and not much disagreement about this. That's good. Well, apparently there was a Ukrainian guy, but that was when the Ukraine was still one of the Soviet Socialist Republics. So as I think you know, it was a fellow from what was then Czechoslovakia,

now the Czech Republic. Indeed, Vladimir Remek on Soyuz 28 in 1978. Was he the pilot? That's what one person, one listener said. He was actually the pilot on that mission. Someone else, actually, Torsten Zimmer, said that he is still around, and he's a member of the European Parliament. Indeed. I think actually his role was he collected chocolate-flavored spacesuits for sale three decades later.

Raised money for his campaign, no doubt. Yes, exactly. I think that's how it works. Well, John Gallant got the answer right, and he was the one randomly selected by Random.org. John Gallant, I don't have it in front of me, but I think he's from New York. Longtime listener, sends all kinds of entertaining stuff.

First time winner. John, congratulations. A t-shirt is on its way. All right, if you'd like your chance to win a t-shirt with the correct answer randomly selected answer the following question what spacecraft crashed into the moon on april 10th 1993 what spacecraft crashed into the moon april 10th 1993 go to planetary.org slash radio find out how to send us your answer. Was not a ranger.

It was a ranger that got really, really lost. 30 years late. There it is. No, there's your clue. It was not a ranger spacecraft. Please do that. If you win, you'll get a Planetary Radio t-shirt. All right, everybody.

Go out there, look up in the night sky, and think about gelatinous masses from Pluto. Thank you, and good night. Pluto plasma. Can you hear it jiggle? I'm going to crunch some more candy now. He's Bruce Betts, the director of projects for the Planetary Society. He does join us every week here for What's Up. Society. He does join us every week here for What's Up.

Join us next time for Mars Exploration Rover Principal Investigator Steve Squires. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.