Planetary Radio: Space Exploration, Astronomy and Science - Getting Ready for Titan with Chris McKay

Episode Date: October 25, 2004

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A Titanic Encounter with Chris McKay on Planetary Radio. Hi everyone and welcome back to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. When we last talked to Chris McKay, it was about Mars. This time the famed planetary scientist joins us to discuss Saturn's moon Titan, just in time for a close encounter with that hazy

sphere. Bruce Betts has yet another space trivia question for you in this week's What's Up. And it all begins with these space headlines. A pesky steering motor isn't keeping Mars rover Spirit from continuing her exploration of the Columbia Hills. Once thought to be a one-time anomaly, the pesky problem resurfaced last week. Opportunity remains in better health

than her sister and is even catching a bit more life-giving sunlight as she traverses Endurance Crater. Now nearing 300 Martian days are Sol's. Both rovers have lasted three times as long as their warranties. Detroit, are you listening? As we prepare this week's show, Cassini-Huygens is in good shape too, with the spacecraft's handlers at the Jet Propulsion Lab practicing for a very close flyby of Saturn's moon, Titan. By the time many of you hear this broadcast, there should be high-quality images posted on JPL's website. You'll also see them on the Planetary Society's site at planetary.org. That's where you can get to know JPL's director, Dr. Charles Elachi, even better.

Elachi, who was our guest on Planetary Radio last week, provides an intimate look at decades of experience that led to his leadership of the renowned facility. By the way, old Albert has done it again. NASA researchers announced last week that Earth's gravity drags space-time along with it as our home planet rotates, just as Dr. Einstein predicted about a century ago. Right on, Albert. I'll be back with Chris McKay right after Emily tells us not to take any wooden meteorites.

Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, how can I tell if a rock that I found is a meteorite? Many people discover strange looking rocks and wonder if they might be meteorites. Meteorites are the primordial remnants of the formation of the solar system. They formed in the vacuum of space from the same materials that make up the rocky planets. A key characteristic of nearly all meteorites is the presence of iron metal. Even stony meteorites usually contain flecks of iron metal within their crystalline interiors.

Natural metallic iron is quite rare on the Earth. The presence of iron makes meteorites more dense than most natural Earth rocks, so they feel heavier, and the metal in a meteorite will usually attract a magnet. But not all heavier magnetic rocks are meteorites. Stay tuned to Planetary Radio to find out more ways to tell meteorites from meteor wrongs. Dr. Chris McKay really gets around. You may find him at his NASA Ames Research Center office in Northern California, or doing geology in the Antarctic, or meeting with European colleagues

as they prepare for the January entry of the Huygens probe into the thick atmosphere of Saturn's moon Titan. We caught the planetary scientist just after he arrived in London last week, and just days before Cassini's close flyby encounter with Titan. Chris McKay, thanks for joining us once again on Planetary Radio. My pleasure. Tell us about Titan. What is it about this moon that makes it so fascinating? Well, Titan is the largest moon of Saturn,

and the thing that makes it so fascinating is that it's the only moon with an atmosphere. And the atmosphere of Titan is even thicker than the atmosphere of the Earth. It's one and a half times the pressure at the surface of Titan than the pressure at sea level on Earth. And the atmosphere of Titan is also composed of nitrogen, the only other atmosphere in the solar system that's composed of nitrogen like the Earth's major constituent. What makes up the rest of that atmosphere? Well, on Earth, of course, nitrogen and oxygen make up the atmosphere, whereas on Titan, nitrogen makes up over 90% of the atmosphere, and the remainder is mostly methane.

And does that have anything to tell us about what studying Titan might be able to tell us about, if not the contemporary Earth, Earth a long time ago? Indeed, Titan, because of the methane and nitrogen in its atmosphere, has chemical reactions going on which produce complex organic molecules. On Titan, these molecules come together to form solid organic haze, which floats in tightens the atmosphere, creating an orange haze. This haze eventually settles down to the surface. Well, these sort of reactions, photochemical reactions producing complicated organic molecules, may have played a role in the origin of life on Earth, in the pre-biological stage of Earth, when the organics were produced non-biologically,

and then somehow the organic soup that remained, or that was produced, prebiological stage of Earth, when the organics were produced non-biologically, and then somehow the organic soup that remained, or that was produced, went into forming the first life forms. Well, on Titan, we're seeing maybe the ingredients of this prebiological organic soup. Is anyone, you or any other researchers, suggesting that Titan might actually be a hospitable place to find life. Well, Titan is similar to the early Earth, maybe in the sense of the organics that are being produced there. But there's one big difference, which is that Titan is so cold that there is no liquid water on its surface. And that is the big difference.

So while Titan may have the steps that represent the organic synthesis that leads to life, it certainly doesn't follow through with life the way, at least life as we know it, which is very much dependent on liquid water. And while it may not have any water seas, there has been speculation that it may have seas of another type. That's right. One of the products of the photochemistry on Titan is ethane. And indeed, there's so much methane on Titan that we think it's condensed on the surface too. So we expect that there may be seas or at least very large lakes of liquid methane and liquid ethane on the surface of Titan. These molecules are unfortunately not very suitable as a basis for life they don't dissolve

organics very readily non-polar molecules unlike water which is a polar molecule which makes them not very good solvents so we don't expect them to be very interesting biologically it might be to our surprise that there is some biology in there but we're not expecting it we It might be, to our surprise, that there is some biology in there, but we're not expecting it. We don't really know as much about Titan as we might like,

in spite of the fact that astronomers have been studying it for a long time. I was interested to see that you can go back over 100 years to the first, I guess, inkling that there was this thick atmosphere around Titan, but it's that atmosphere that really, I guess, has prevented us from learning more about the surface. That's right. In the 80s, the Voyager spacecraft flew by all the moons of Jupiter and Saturn and gave very nice photographs of them. But Titan remained a mystery because it is shrouded in this organic haze, which blocks our view of the surface. in this organic haze, which blocks our view of the surface. So the only way to really know what's going on on the surface of Titan is to send a probe through the atmosphere down to the surface,

which is now what we're doing. That probe, built by the European Space Agency and launched as part of the NASA ESA mission, will fly down through the atmosphere of Titan in January of 2005. And you are a co-investigator on one particular instrument on that little probe. Well, it's the Atmospheric Structure Experiment, or HASI. How do you pronounce that acronym? We pronounce it HASI, and it's an Italian instrument.

It's built to analyze the atmospheric temperature and pressure on Titan as the probe goes through the atmosphere and on its way to the surface. And it will tell us a lot about the temperature structure and the dynamics and stability of the atmosphere. And I'm one of the co-investigators who will be involved in looking at that data and trying to figure out what it means. Now, as I read about it, even though it's referred to as a single instrument, it apparently is a package of quite a number of little sensors. That's right. The heart of the instrument is an accelerometer, which measures the rate at which the probe slows down as it comes through the atmosphere.

It also has pressure sensors and temperature sensors that will measure the pressure and temperature through the atmosphere. And it is only one of many instruments on the probe. Some of them will measure the composition of the atmosphere. Some will collect samples of the haze and analyze that. Some of them will look at the spectrum of the light from the sun as it filters through the haze. And that same instrument will also photograph the surface as it gets nearer. I was also interested to see what your instrument might be able to tell us

if it happens to come down in one of those hydrocarbon seas. That's right. The accelerometer on the HACI instrument should easily be able to tell the difference between a crash into solid surface and a splash into a liquid surface. And the probe has been designed to float even in liquid hydrocarbons, liquid methane, and liquid ethane. So if the probe does splash down, we should see it bounce up and back as it settles to its floating position. And we should see that trace in the accelerometer very clearly. Is there also an imaging device, a camera, on the Huygens probe? That's right.

One of the instruments will take pictures, and because the haze is so thick, it will actually bring a headlight. So flash onto the, turn the lights on, look down at the surface, and then take pictures as it comes down close to the ground. You know what? I just happened to put it together in my head that your instrument, H-A-S-I, could also be pronounced as hazy. Was that intentional? No, I don't think so.

Hazy is the way we pronounce it, but it could be pronounced hazy, I guess, especially if you stuck another S in there. Well, how appropriate that might have been for not this imminent flyby of Titan, where we expect to learn much more about this mysterious moon, but this descent of a probe, the Huygens probe in January, that Chris McKay has so much to do with. Chris, if we can, we're going to take a quick break and then come back and talk a little bit more about Titan and what we hope to learn about it.

We hope you'll stay with us on Planetary Radio. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to

explore Mars. We're tracking near Earth asteroids and comets. We sponsor the search for life on other worlds, and we're building the first-ever solar sail. You can learn about these adventures and exciting new discoveries from space exploration in The Planetary Report. The Planetary Report is the Society's full-color magazine.

It's just one of many member benefits. You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. Chris McKay is our special guest on this edition of Planetary Radio. He is and has been for a long time a planetary scientist with the Space Science Division, NASA Ames Research Center, up north of us here at Planetary Society headquarters. But, Chris, actually, we catch you in London today. Are you there for pleasure or work?

No, I'm here on a business trip, and with phones. It's just as easy to do an interview from here as from the north of California. And we'll hope someday we can do that between here and the surface of Mars, let's say. Yeah. Let's go back to Titan, though, a little bit farther out in the solar system, and back to this topic of Titan's atmosphere, which obviously fascinates you to such a degree. We know that there are seas on Earth. We suspect there might be seas on Titan, as we spoke about a few minutes ago.

Does this also imply that there might be storms on Titan? Well, it's a good question, and there may be. Like water on Earth, methane on Titan should cycle through the atmosphere. It should evaporate and precipitate, and we would expect there to be clouds, and if there's clouds, maybe rain. But puzzlingly, we've seen very little evidence of clouds on Titan. The clouds we have seen appear to be only over the south polar cap. So there's a mystery there as to why doesn't Titan have thicker clouds? Does it have storms like the Earth does and rain? And if it does,

are they just at the south polar region? And then why would they be there and not over the tropics, which tend to be the stormiest, cloudiest places on Earth? This is one of the mysteries about Titan that I think we'll begin to understand from the flybys that are occurring here, which will take detailed images of these clouds wherever they are. I noticed in the description of your instrument, the one you are a co-investigator for on the Huygens probe, the HAZI experiment, that in that package of sensors, there are some electromagnetic sensors. And that immediately made me think, what, are they trying to detect lightning? Exactly.

Exactly. One of the questions is, if Titan has clouds, could it also have lightning? Or could the haze itself, just from the movement of the particles of the haze, generate enough static electricity to create lightning? And we've detected lightning on Earth, obviously, but we also have detected lightning on Jupiter, and there's indications of lightning on Venus. It's a possibility that Titan also has lightning, and so we have these electrical sensors on the probe

to try to pick up the characteristic electrical signals that lightning puts out. As we look at these similarities and differences between the atmospheres of Earth and Titan, other factors come to mind. I know one that you've also looked at is the greenhouse effect. Yes. Titan, like Earth, is kept warm by its thick atmosphere. Earth's atmosphere keeps our planet significantly warmer. In fact, the temperature on Earth would be below freezing on average

if it wasn't for the greenhouse effect of our atmosphere. Titan also has a greenhouse effect. But Titan has something that Earth doesn't have. In fact, Titan is the only planet in the...only atmosphere in the solar system with what we call an anti-greenhouse effect. And this is caused by the haze, the organic haze high in the atmosphere, blocking sunlight from reaching the ground. And so on Titan, there are competing effects, a greenhouse effect and an anti-greenhouse effect. People have speculated that Earth may have an anti-greenhouse effect back 65 million years ago when the asteroid impact that killed the dinosaurs. And people have also talked about this in the context of nuclear war,

and they refer to it then as nuclear winter. Titan has a naturally occurring nuclear winter effect. We call it the anti-greenhouse effect, and it'll be interesting when the probe goes through the atmosphere of Titan to measure the sunlight as it penetrates through this organic haze layer and to characterize in detail the anti-greenhouse and greenhouse effects in Titan's atmosphere. Well, this must have you wondering, and other scientists wondering, if there's some kind of dynamic equilibrium between those two effects. There probably is.

And we've studied what controls which wins, the greenhouse effect or the anti-greenhouse effect. And a key player seems to be the photochemical production of the molecule hydrogen, and then the escape of that hydrogen through Titan's thick atmosphere due to its low gravity. And so there's a lot of interesting coupling between the chemistry, the haze, and the temperature through the greenhouse and anti-greenhouse effects. We have some rough ideas on how this coupling might work, but we're hoping to get more detailed information from the HACI instrument,

from the other instruments on the probe, and also from the orbiter as it flies by Titan repeatedly over the next few years, giving us detailed maps of the surface. Yes, Dr. Elachi said last week this is just the first of many close flybys of Titan. And, of course, Planetary Radio will be covering the descent of the Huygens probe in January in depth. But to stick with these flybys as we finish up here, I wonder if you were intrigued by anything that Cassini has already learned, even though its closest flyby of Titan so far, back when it was inserted into its orbit around Saturn, was something like

100 times as far away. I guess it still gave us our best view ever of this moon? The first flyby gave us an interesting perspective more than anything else, because the flyby occurred underneath the south polar region. And so we were able to point the spacecraft camera straight up to look at the bottom of Titan. And that's a view that on Earth we can only get from a steep angle. And so there had been discovery of these clouds in the South Polar region, but they'd been seen so close to the edge of Titan that there was some

debate about whether they were real or not. But the Cassini images, since they came from a completely different perspective looking straight up at the South Pole, were able to confirm that indeed we did see these clouds. The resolution of the Cassini spacecraft, because it was so far away, was not that much better than the Earth telescopes. The big advantage of that first flyby was the perspective that we could get from being below Titan instead of being in the plane of the ecliptic, which we are necessarily with Earth. What do you hope to learn when this flyby from a distance of just, I think it's a thousand kilometers, takes place really even as some of our listeners hear this program?

Well, I think that the thing that I'm going to be looking for first is evidence that there are clouds in the tropical regions as well as in the South Pole. There are some interesting suggestions of the possibility of equatorial clouds, very thin, wispy equatorial clouds. And hopefully the camera on Cassini will be able to pick those up if they're really there. One last question, Chris. Can you imagine someday, with the right technology and the right protection, a human mission to this moon, Titan? Or are we going to, by necessity, going to be depending on ever more sophisticated robots? Well, it's a hard question. I think it's possible to imagine a human exploration of Titan.

The atmosphere would allow for things like airplanes and balloons, and you could imagine a spaceship that's kept warm against the cold. I'm not sure why you would do it. It's not anywhere near as compelling scientifically as, say, Mars. But if you imagine in the future there there might be some thrill seekers. You can imagine extreme exploration hobbies of the year 25, 2500 might include a trip to Titan in your specially heated spacesuit and spaceship and cruising through the atmosphere there. I think it'd be more for the fun of it than for real scientific exploration, though.

Well, maybe one of Burrutan's grandchildren will build a ship for that fun trip. There you go. Chris, we're out of time. Thank you so much for joining us, and good luck both with what is learned in this flyby and especially with that descent to the Huygens probe through that thick atmosphere of Titan this coming January. Good talking to you, Matt. Planetary Radio will be back with Bruce Betts and what's up right after this return visit from Emily.

I'm Emily Lakdawalla back with Q&A. How do you tell meteorites from meteorongs? Many people find rocks that appear bubbly and think they might be meteorites. But because meteorites formed in the vacuum of space with no gases present to make such bubbles, any rock containing such holes is almost certainly not a meteorite. Bubbly rocks usually have a volcanic or even an industrial origin. They are also usually lightweight while meteorites feel heavy. Many meteorites do have indentations in their surfaces that look as though

they were molded like clay. These indentations are known technically as regmuglips, but commonly just as thumbprints. The thumbprints create corners and edges on the meteorites that become rounded off when the meteorite suffers its fiery passage through our atmosphere. This atmospheric passage heats the outer surface of the meteorite to high temperatures, creating a blackened or dark brown fusion crust on the outside. The fusion crust may even display flow lines, where the surface of the rock melted and flowed around it as the air whistled past. But there are a variety of earthly

processes that can mimic any of these features of meteorites, producing some incredibly convincing meteor wrongs. In the end, no rock can be called a meteorite unless it has been examined and verified by a member of the International Meteoritical Society. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. It's time again for What's Up on Planetary Radio, and so we are joined by the Planetary Society's Director of Projects, Bruce Betts. Welcome back, Bruce.

Thank you very much. What's up? Well, we've got some really cool stuff up. We've got a total lunar eclipse and four planets up in the predawn sky. Total lunar eclipse on October 27th or 28th, depending on where you live in the world. It's October 27th Pacific time with the center of the eclipse, the maximum totality occurring at 8.04 p.m. Pacific Daylight Time. And that would be 3.04 a.m. on the 28th UT.

Go see the eclipse. It lasts for a long period. It's in totality for roughly an hour and a half. You can find more information on our website, planetary.org, about where all you can see it from. Basically, it's visible from the Americas, from Europe, from Eastern Asia. Well, I'm sorry, Western Asia, but you're not going to see it if you're in Eastern Asia or Australia unless you get on a plane.

Now, we know that some of you out there, some of our East Coast listeners, are probably hearing this a little bit too late, but we promise there will be other eclipses. And darn it, you should have listened to the show last week where we told you about it then. That's right. That's why we tried to give you guys a preview well ahead of time like that. But it's all right. Far be it from us to chastise.

Really? Yes, yes. Clearly, far be it from us. We're going to chastise you for listening to the show. Please don't leave. Remember what we talked about, Matt. Yeah. I'll be nice.

Okay. Be nice and not so needy, okay? Okay. All right. On to the pre-dawn sky. Maybe if I send them candy? Anyway, go ahead. Yes, and flowers.

Pre-dawn sky, four planets visible, really three easily. Mars is kind of tough. Look for Venus and Jupiter getting very close over the next couple weeks, just snuggling up next to each other. They will actually be less than a degree apart in the sky on November 4th and 5th. So right now you look in the predon sky, that brightest star-like object is Venus. The other really bright object, but much dimmer than Venus, is Jupiter just to its lower left. They will actually trade places in the sky, passing each other as viewed by us in that

November 4th, 5th time frame. If you look in another part of the sky, far, far, far to the upper right, continue around, you'll see Saturn, which is actually rising in the evening now, by a little bit, around 10 p.m. in the east-northeast, Saturn rises. And then Mars is tough, very far to the lower left of Jupiter and Venus, low on the horizon just before dawn. But it will get easier to see as time goes along. And this is great, because it wasn't that long ago you were saying, folks, there's really nothing to look at, goodbye.

And now it's getting better and better. It's true, it's getting nasty with planets. You still mostly have to be up before dawn, but you can pick out Saturn, which is always great with a small telescope or even good steady binoculars to see the rings. What else do you have for us? Random Space Fact! The height of the

International Space Station actually varies over time because of atmospheric drag. Even though they're basically in a vacuum, there's still little tiny bits of atmosphere that slow it down over time. They actually fire rockets periodically to reboost the height. But, for example, over the last year, the average height of International Space Station

has varied from about 355 to 380 kilometers. That's a pretty big difference. Yeah, a very non-trivial difference, and that's even with boosting in between. So there you go. It's such a spindly-looking thing. It's hard to imagine firing a rocket engine on it and not having it bend in half, but I guess they figured all that out before they put it up there, right?

Fortunately, they seem to have, yes. Yes, it seems to be quite structurally sound. Good. On to the trivia question. We asked you a couple weeks ago, where in the solar system will you find Uruk Sulcus? How do we do, Matt? Where can you find Uruk Sulcus? Well, other than in some B-grade movies made in the 1950s about Norsemen, you know, Vikings, I think,

it turns out that you can find Uruk Sulcus on Ganymede, that moon of Jupiter, right? Yes, indeed you do. One of the four Galilean satellites of Jupiter. And we found this out from a whole bunch of you who entered this week's contest. And one of you happens to be the winner. And that winner is Evan Dembski. Evan Dembski, who wrote to us from Johannesburg, South Africa. He says it's on Ganymede. Correct.

It is the lighter and presumably younger area of that moon. So, Evan, congratulations. We're going to put a Planetary Radio shirt in the mail to you as soon as you tell us what size you need. We'll be in touch. All righty. I bet Oryx Sulcus would require a multi-extra large. Really?

Go Vikings. All right, on to the new trivia question. If you want to win your fabulous Planetary Radio t-shirt, answer the following question. How many member states are there in the European Space Agency? How many member states in ESA? To give us your answer, go to planetary.org slash radio. Find how to email us your wonderful answer and your T-shirt size. And please get that in to us by Monday, November 1th.

That's November 1 in English. And we will look for it by noon on that Monday. That means that you will be eligible for that week's trivia contest that we do every week here on What's Up. Bruce, I think we've made it. Yay! Yay for everyone. Hey, everyone, go out there, look up in the night sky, and think about who was the first person to ever put lemon in iced tea. Thank you, and good night.

Pondering the great questions, that's what we do here on Planetary Radio and even when it gets kind of tart Oreck roll faster stroke stroke that's Bruce Betts the director of projects for the Planetary Society he joins us every week here on What's Up

at the very end of Planetary Radio be sure to join us next week as we recap Cassini's exciting encounter with Saturn's moon Titan. In the meantime, you can drop us a line if you'd like. We're at planetaryradio at planetary.org. That's planetaryradio, all one word, at planetary.org. Clear skies, everyone.