Planetary Radio: Space Exploration, Astronomy and Science - Cassini at Saturn: An Update From Linda Spilker

Episode Date: October 13, 2008

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Another report from Saturn, 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 of the Planetary Society. Linda Spilker once again throws her hat into the ring, or rings. The deputy project scientist for the Cassini mission has another of her semi-regular updates for us. Bill Nye the Science Guy is back. He reports from Cornell, his alma mater, where the annual meeting of the American Astronomical Society's Division for Planetary Science

just finished. Emily Lakdawalla will continue her Q&A on the storms of Jupiter and Earth, and Bruce Batts will join us for another What's Up examination of the night sky. We'll also give you a preview of our sixth anniversary contest coming up in just a week. Stand back, everyone. We've got hypergolic space headlines coming your way. By the time you hear this, NASA should have announced its reformulated plans for fixing the Hubble Space Telescope. The shuttle repair mission was put on hold when a critical computer on the venerable instrument failed. The space agency is expected to try to switch operations to a backup system this week. to try to switch operations to a backup system this week.

Emily Lakdawalla reports in her blog on NASA's decision to stick with a 2009 launch of the Mars Science Laboratory. The big and very sophisticated rover has run into its share of development problems, including cost overruns and redesigns of its motors and actuators. Emily does her usual great job of telling the story at planetary.org. The International Space Station's Expedition 18 crew has rocketed into Earth orbit aboard a Soyuz capsule. The astronaut and cosmonaut are joined by American civilian Richard Garriott, the latest person to pay the Russian Federal Space Agency

for a nine-day sojourn on the ISS. I'll be right back with Linda Spilker. Here's Bill. Hey, hey, Bill Nye the Planetary Guy here, Vice President of the Planetary Society. Today I'm speaking to you from the campus of Cornell University in Ithaca, New York. Now, Cornell, of course, is where Carl Sagan, one of the founders of the Planetary Society, was a professor. And it's where I went to school. But here's the thing. It's where the Division for Planetary Sciences is meeting this week. And last week, I was in London. I was in Scotland, in the UK, at the Astronautical Federation meeting, the Congress. And everybody in the world gives me the impression, maybe not

directly, but gives me the impression that they want the National Aeronautics and Space Administration, the United States Space Agency, to lead. These will be people from the Indian Space Agency, the Chinese Space Agency, and especially the European Space Agency, the Japanese Space Agency. They want the United States' space organization to lead the way. So I would say to everybody, as taxpayers and voters, as we come up in these very difficult economic times and this pivotal election, I want you to think about the direction that we want us to go. We want the world to go in space. But here's the deal, everybody. We've got to explore space, and we have to use our

resources wisely. So I'm asking everybody at NASA to really evaluate how you're going to spend your money, not just for yourself and for your pursuits, whether it's near-Earth objects like asteroids, distant objects like the Plutoids or distant stars and galaxies, but for the good of all humankind here on Earth because everybody wants the United States to take the lead. It's a hard thing to put your finger on, but you can feel it everywhere you went at these two conferences. And that way we can make the most efficient use of resources around the world to understand our place in the cosmos.

So I hope you'll keep your eye on the Planetary Report and the Planetary Society website. Read Emily Lakdawawa's blog. Think over what we need to do in space so that we can go forward efficiently and make new discoveries and change the world. Well, thanks for listening. I'm Bill Nye the Planetary Guy.

Cassini has done it again. Just a few days ago, the bus-sized spacecraft nearly grazed the surface of Enceladus, the small moon of Saturn that has packed big surprises for scientists. As we finish this week's show, there is very little on the Cassini website about the October 9 flyby other than raw, unprocessed images. We've got the link for you at planetary.org slash radio. It was only a couple of days before this event that I got Linda Spilker on the phone for another of her Cassini updates. Linda is the longtime deputy project scientist and a principal scientist on the mission.

She spoke with me from her office at the Jet Propulsion Lab near Pasadena, California. Linda, welcome back to Planetary Radio. I was just telling you offline, I think that you probably have the record for appearances on this radio show. And I'm delighted to come back for another update on that mission that is still circling Saturn. I'm delighted to come back for another update on that mission that is still circling

Saturn. I'm delighted to be here, Matt. So as we speak, we're still a day or two out from Cassini's next encounter with Enceladus. I am flabbergasted that you're going to be flying, what, 25 kilometers above the surface, 16 miles? Right. That's the very closest we've yet flown to any of Saturn's moons. Not only are we coming close, we're going to be diving through the icy plumes that we've discovered on Enceladus. First of all, you discovered the plumes, as you said. You've had at least one previous experience, right, in August, where you were able to learn a little bit more about them, including where they come from? right, in August, where you were able to learn a little bit more about them,

including where they come from? Right. We were able to get some very, very high-resolution images of the south polar region, this area we call them tiger stripes. It's actually fractures at the south pole, and we know that jets of material come out of these fractures, and so we got a close-up look and could even see boulders on the edges of some of these fractures. It was a very exciting flyby of Enceladus. We also noticed hints that maybe some of the areas weren't quite as warm as they might have been on previous flybys. So we're still trying to sort through and understand those data.

That will tell us something about how these plumes change with time. Some amazing images also from that flyby, which I don't know how the spacecraft managed to grab those, but my understanding is that this time the goal is not so much imaging? Right. With this flyby, what we're doing is we're not going to be pointing our cameras at the South Pole for the closest part of the flyby, but rather we'll be lining up our ion and neutral mass spectrometer and the cosmic dust analyzer and the other fields and particles instruments so that they get a really good chance to, in a sense, taste the material coming out of the plumes.

With the ion and neutral mass spectrometer, they'll have their best signal-to-noise ever, their highest signal because we're in so close, and they hope to get new composition results about just what exactly, besides water, is coming out of those jets and the plume coming out from Enceladus. And then the Cosmic Dust Analyzer actually has two different goals. It wants to look for material that's being sputtered off of Enceladus' surface by

micrometeoroids, in the sense we could sample some of the old surface of Enceladus, as well as to measure the plume particles and to look for their sizes and densities, as well as their compositions. And then there's some hope with CDA, depending on how we fly through this region, that they might actually sample individual jets. We know from the images that there are a series of individual jets coming out of these fractures, and maybe we'll get lucky and actually cross through one of the individual jets and see the particle counts go way up and then come back down as we go through the other side of the jet. In a sense, are we going to be getting a chance to look below the ice that covers this little moon?

Well, in a sense, you're doing that. By looking at the material coming out of the plumes, you're getting a chance to sample what's coming out from inside of Enceladus. And scientists are fascinated by this tiny moon that might even have an ocean of liquid water beneath the surface. And just the possibilities for habitability are very exciting as well. These instruments that you're using that will be especially useful in this next close-up flyby, did anybody expect that you would be able to use these basically by immersing them in the material that they're going to be analyzing?

No, we had no idea because we didn't know Enceladus had an active plume like this. And, you know, if we could go back, you know, if we send another mission back to Saturn, then we'll take this. And for instance, it'd be great to have a larger mass range for the ion and neutral mass spectrometer. It only goes up to 100 Dalton. You know, it's like 100 protons. That's not very far. And have something that goes out to say 1,000 or 10,000 would be, you know, very interesting. And for Titan as well, to have an instrument that could cover a broader range. And I think we'll be thinking through before we go back to the Saturn system again

just what kinds of instruments we want to bring. But we had no idea that we'd actually be, we thought we'd be sampling, you know, like bits of Titan's atmosphere, and that's what we built the ion and neutron mass spectrometer for. But to come in and have a whole, you know, other place for it to do its sampling is just amazing. Is there much danger to the spacecraft flying through these particles? Oh, that's a great question. We have detailed models.

We think that most of the very large particles, in this case large for Cassini would be a few hundred microns, the very largest particles, just come up and tend to fall back onto the surface. And so we think that what we'll be flying through are those particles that primarily make up the E-ring. The E-ring particles, which are fed by the plumes coming from Enceladus, are only a micron or so in size. And these are small particles that are not large enough to harm the spacecraft, even though we're flying by at a very high velocity.

You've got yet another flyby in late October, a little bit farther out? Yes. Actually, we're calling these two flybys of Enceladus our doubleheader. But there's another flyby on October 31st. And in that case, we're going to be a little bit further away, about 200 kilometers away. We're going to be a little bit further away, about 200 kilometers away. And we'll be focusing our optical remote sensing instruments, our cameras, spectrometers, taking thermal measurements as well with this flyby. So you can think of these as complementary flybys, one to dive deep in, taste the plume,

and the other to, from just a little bit farther distance, they're really not that far away, to get high-resolution pictures. In fact, some of the highest resolution might be as good as 8 meters per pixel, really seeing very fine detail at the south pole of Enceladus. Let's turn away from this somewhat less mysterious moon than in the past, but still a very fascinating orb, and talk about some of the other recent developments from the mission. I read a little bit about more work that Cassini's been able to do to learn about the planet's most famous feature, those rings, and some of them discovered near little tiny moons.

Right, right. It's beginning to look like every time you have a little tiny moon, that moon then sheds bits of itself and actually creates rings or arcs of material that then orbit around with the moon itself. And so that's very exciting. We're trying to understand that process of how that material comes off of the tiny moons. And then we're in a phase of the mission. we call it the Cassini Equinox mission. We call it that because we'll actually be observing a very interesting time next fall, as the sun actually moves from the south side of the rings through the ring plane to shine on the north side of the rings. And that'll give us an interesting opportunity to look for perhaps long shadows cast by some of these wave features that are in the rings that might be

vertically extended or look for any warping in the rings. And also watch how the ring particles heat up and cool off as the sun moves from one side of the rings to the other. We'll have more from Saturn and the Cassini mission's Linda Spilker when Planetary Radio continues. Hey, Bill Nye the Science Guy here. I hope you're enjoying Planetary Radio continues. passion, beauty, and joy of space exploration. You probably do too, or you wouldn't be listening. Of course, you can do more than just listen. You can become part of the action, helping us fly solar sails, discover new planets, and search for extraterrestrial intelligence and life elsewhere in the universe. Here's how to find out more.

You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Linda Spilker is the Deputy Project Scientist for Cassini-Huygens,

which is now well into an extended mission, flying among the mysterious moons and magnificent rings of Saturn, helping us gain new understanding of and appreciation for our solar system's second biggest planet and its companions. Are we getting a better understanding of how these rings both achieve and sort of maintain their structure? Oh, it's a very interesting question. We've learned so much with Cassini. We've gone to thinking of the rings as individual particles that gently do a cosmic dance around Saturn and bump into one another, to something that looks like

in the A and B rings primarily, you have clumps of material, something we call self-gravity wakes, and that these clumps can be maybe tens of meters wide to maybe 100 meters wide, and the particles stick together. But we think it's not permanently sticking together, but rather transient. They stick together for a while, broken apart, and then re-stick together in a very different idea of the rings than we had, say, from the Voyager flybys 25 years ago. Okay, let's go to Titan, where I don't know about you, but I'm ready to do some, maybe not water, but liquid skiing.

Oh, yes. Titan has turned out to be a very fascinating place with all of the lakes at the North Pole, and even a with all of the lakes at the North Pole and even a few lakes that we found at the South Pole as well. And we think that these lakes are composed primarily of hydrocarbons, liquid methane and ethane. And one of the things we're very excited to watch as the sun continues, as it goes from winter into spring in the North Polar region, do these lakes perhaps start to evaporate and maybe create clouds and perhaps have storms then at the south pole?

So we're very interested in looking as the seasons change to see if we might be able to actually see some changes in the lakes themselves. Lots and lots of lakes apparently, but where are the oceans that some people expected? That's an excellent question, the oceans. Initially, we thought as we were going there with Cassini, we'd find Titan, a moon covered with oceans of liquid hydrocarbons. And now we're wondering if maybe they're perhaps underneath the surface a bit or some other processes are going on that have processed what might be liquids. We found dunes on Titan, very reminiscent of the sand dunes we see here on Earth. Only those dunes are composed, we think, of complex particles of these hydrocarbons.

So maybe some of that material is locked up now, perhaps, in these dune particles. All right. We haven't yet talked about the planet itself, the body at the center of this rather amazing and complex system. What has Cassini unveiled recently about that planet? Well, Saturn is very interesting, especially if you look in the near infrared. It gives you a chance to look through the haze, basically, that surrounds Saturn. And if you look in the near infrared, Saturn starts to look a lot like Jupiter, very complex storms and bands of atmosphere rotating in different directions.

And then there's the Saturn poles, the North Pole and the South Pole, very different. At the South Pole, we see a hurricane-like storm circling around. And at the North Pole, see a hexagon. The hexagon was something that Voyager actually first saw, and it looks like it's lasted all the way up until Cassini has arrived. And right now in the tour that we're in, we're in a really great set of orbits and very high inclinations, about 70 degrees inclination, giving us a great chance to look down both on the North and South Poles

and get really detailed measurements of those poles. And with the planet as well, we're interested in watching as the seasons change. Does the storm activity change? Does it move from the southern hemisphere to the northern hemisphere? Are there other changes related to Saturn seasons as well? Linda, what is the state of Cassini's health? Cassini is in excellent health. Everything is operating nominally.

We're ready to go and looking forward to more exciting science, both in the Cassini-Equinox mission and perhaps if we get funding from NASA. In additional years that will follow on, we think we have enough fuel perhaps for another maybe even seven years of a mission after the end of the Equinox mission. Wow. So four years already, and now you're into this two-year extension, the Equinox mission? That's correct. I'm using the word a lot because I think it's absolutely applicable to this mission overall. But it is a rather amazing performance by this spacecraft,

considering where it is and what it has been doing, the challenges that it has faced, and the fact that you're looking forward to returning lots more science. And I take it there are still many, many questions to be answered. Yes, there are many questions about the Saturn system, about the planet, the rings, you know, Titan looking for seasonal change. Enceladus, can we understand more about these plumes and the activity that's coming from Enceladus? Can we understand more about these plumes and the activity that's coming from Enceladus? And does it change with time? So as we go into the future, we'll be focusing in particular on Titan and Enceladus, as well as the rest of the Saturn system, and trying to put together the puzzle that Saturn and understand the complete global picture of what we have in this amazing system.

With all of this happening, you've got a new colleague there, Bob Pappalardo, who's been a guest on this show. Yes, that's right. He's the new project scientist for Cassini. Linda, how long have you been working on this again? You've told us in the past, but I forget. Oh, I've actually been working on Cassini before it even had a name or was a project since the late 1980s. So I've been here about 20 years. Still having as much fun as ever? Oh, absolutely, absolutely. It's a wonderful mission to be a part of and to have the opportunity to see the new discoveries that we make with Cassini

as we get close to these objects. And I just look forward to many more years with Cassini. It is also always wonderful to speak with you, and I hope we can do it again in a few months. Then again, maybe sooner, depending on what happens, particularly with these two Enceladus flybys. And I look forward to having you back. Okay. Thank you very much, Matt. Linda Spilker is the Cassini Deputy Project Scientist and a Principal principal scientist on that mission that continues to explore that beautiful planet and its wonderful system of moons and rings and other stuff out there a billion

miles from our little blue-green planet. We'll be talking with Bruce Betts in just a couple of minutes. That'll be after a visit with Emily Lakdawalla for this week's Q&A. for this week's Q&A. Hi, I'm Emily Lakdawalla with questions and answers. Last week, I answered a listener's question about the difference between storms in Earth's and Jupiter's atmospheres. But the air is not the best place on Earth to look for analogs to Jupiter.

The natural scale of systems in Earth's atmosphere, what experts call the first Barrow Clinic radius of deformation, is about a thousand kilometers, or a tenth the circumference of the planet. The natural scale of systems in Jupiter's atmosphere is also about a thousand kilometers, but Jupiter has more than a hundred times as much real estate as Earth does. So Jupiter's storms have much, much more room to play than storms do on Earth which is why Jupiter's storms last so much longer. You can find better analogs to Jupiter in Earth's oceans where the natural scale of systems is closer to a hundred kilometers

meaning that Earth's ocean basins are as giant as Jupiter when you compare them to the size of their storms. And if you look at Earth's oceans, you can find perfect analogs for Jupiter's red and white spots. One example is in the Atlantic, where salty Mediterranean seawater slides down and breaks off, forming beautifully shaped, high-pressure whorls called Mediterranean salt lenses, or METIs for short. Oceanographers have placed instrumented floats into METIs and tracked their stately motions for years. Earth even has an analog for the great circumplanetary jet streams of Jupiter, the Antarctic circumpolar current which circles the globe unimpeded by continents,

transporting more water than any other current on Earth. So Earth's oceans help it bridge the divide between terrestrial and giant planets. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Standing by to bring us up to date on what's up in the universe is Bruce Betts, the Director of Projects for the Planetary Society. We've got him... Woo! Bane at the universe.

We have him on the Skype connection. This is the first time in a while that we haven't done this in person, but still good to talk to you. And it's always a pleasure to talk to you, Matt. Don't sound sarcastic because I know you enjoy doing this. Oh, I do. I just am naturally a sarcastic sounding kind of a guy. Yeah, that may be. Well, tell us sarcastically what's going on in the solar system. Venus looks great. Jupiter, wonderful, fabulous, beautiful. All right, that's enough sarcasm. No, Venus actually does look lovely, as does Jupiter. Venus over in the west after sunset, getting higher and higher up as the days go along.

Brightest star-like object over in the west after sunset. And if you turn your head to the left and look towards the south, you will see Jupiter, also a very bright star-like object up in the early evening and through the early and mid-evening. And if you're up for the pre-dawn sky, you can check out Saturn in the east before dawn. And you can also, if you look low enough and have a low enough view, get a look below Saturn at Mercury, down towards the horizon for the next couple weeks. I'll mention the Orionids are coming up, a meteor shower.

It's not a traditionally very spectacular meteor shower, but we do see an increase in meteor flux peaking around the 21st. So if you want to go out and stare at the sky and hope to see some meteors, you can get at a dark side up to about 20 per hour with the Orionids. On to this week in space history. It was five years ago, seems hard to believe, that Shenzhou 5 launched the first human into space from China. Had to struggle with that. The first Chinese human into space. China. Had to struggle with that. The first Chinese human into space.

Works for me. That does not seem like five years. You're absolutely right. That seemed like maybe two years ago. And, of course, it was only just, what, very recently that they had three fellows, three taikonauts up at the same time. Yes, indeed. On to Random Space Fact.

Skype just isn't up to Random Space Fact, but we'll make it work. Few people are. Astronaut Peggy Whitson, with 377 days in space and two ISS space expeditions, has more time in space than any other American, but ranks about 20th overall. Oh, is that right? Yes, indeed. You mean there are that many Russian cosmonauts who are that far ahead of her? Yeah, pretty much.

Wow, that's impressive. Well, good on you, Russia. Well, you know, they've been doing long-term space stations for a while. So we're on to trivia. And we asked you, who was the first NASA administrator, starting all the way back in 1958? Fifty years ago, who was the first NASA administrator? How did we do, Matt? Absolutely everyone.

And we had a lot of entries this week. Everybody got it right. That first administrator actually got his start before NASA was formally established, which took place on October 1, 1958. It was Thomas Keith Glennon, who served from August 1958 until January 20, 1961. And it was Bruce Kressler, Bruce Kressler of Helvetia, West Virginia, who got chosen by Random.org and is going to be getting a Planetary Radio t-shirt. Bruce. It's a fine name. What?

Well, I told him that the name wasn't going to help him win, but hey, you know, it worked one way or another. Incidentally, he says he has been a fan for quite some time. Not sure how long, but he's collected the podcast back to September of 2004. So we got a fan out there who's going to have a Planetary Radio t-shirt to wear in his corner of West Virginia. Thanks a lot, Bruce. Bruce Kressler, not Bruce Betts. Oh, fine. I'll thank you later. All right. Well, let's do another trivia contest,

see how many Bruce's we can get to randomly win the prize. What is the most massive star within 10 light years of us where we sit right here this evening? The most massive star within 10 light years? Go to planetary.org slash radio. Find out how to enter and compete for the Planetary Radio t-shirt if your correct entry is randomly chosen. And you've got until

Monday, October 20 to get us the answer to that one. Monday, October 20 at 2pm Pacific Time, as usual. But October 20 will not be, as usual, the show that begins airing that day, our Planetary Radio episode, the next one, because we're going to start the celebration of our, you ready for this, Bruce, the sixth anniversary. Yay!

We are older than taikonauts. That's true, yeah. We've been in space longer than China. But we're going to have some good prizes. I'm not going to tell you what they are yet because it's not entirely tied down. But by next week. Well, that's a good reason not to tell people. We should know by next week.

We should be able to tell you what the various prize packages are. And next week is when we will begin that sixth anniversary show, which means we'll announce the winner of it on November 3rd, the week of November 3rd. However you listen to us, whether it's via podcast or XM or one of the many, many radio stations that we are thrilled to say carries planetary radio. And I think we're done. All right, everybody, go out there, look up the night sky, think about light switches.

Thank you and good night. He's Bruce Betts, the Director of Projects for the Planetary Society. He joins us every week here for What's Up, where the lights are always on. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.