Planetary Radio: Space Exploration, Astronomy and Science - Cassini's Linda Spilker With Another Report From Saturn

Episode Date: December 27, 2010

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Cassini Project Scientist Linda Spilker is back, this week on Planetary Radio. Welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. It's been too long since we last checked in with Linda. She'll bring us up to date on that big spacecraft that continues to orbit Saturn, whizzing past its most interesting moons now and then. We'll hear about that possible ice volcano on Titan, among other things. When Bill Nye says scram, he doesn't want you to go away. He's just excited about the latest success in

development of a scramjet and its possible combination with a rail gun. Don't worry, the science guy will make all things clear. So just how random are Bruce Betts' random space facts? Very, very random, as you'll hear during today's What's Up segment, when Bruce and I will also give away a signed copy of Mike Brown's new book, How I Killed Pluto and Why It Had It Coming. Of course, we know who you really want to hear. It's Planetary Society Science and Technology Coordinator and ACE blogger, Emily Lakdawalla. Emily, happy holidays. I hear some children in the background there. Is your shopping all done? Our shopping's done. Our baking is just starting, though. We've got a lot of work to do in the kitchen.

Okay. Well, I'm sure that by the time people hear this, everyone will have been delighted with all those baked goods. Let's talk about some of the highlights from the blog last week, beginning with yet another Akatsuki update and a possibly very courageous, not to say foolhardy, option when it returns to Venus. Yeah, you know, they're trying to figure out what exactly went wrong with the spacecraft, and they're dealing with the possibility that part or all of that main engine nozzle may have broken off. And so they're not sure how much power they're going to be able to thrust with once they do return to Venus in six years, assuming, of course, the spacecraft is still healthy then.

once they do return to Venus in six years, assuming, of course, the spacecraft is still healthy then. It has been suggested, I think, more by members of the press than from internally in the mission, that perhaps they could actually try to aerobrake into orbit around Venus, which is when you dip a spacecraft into the upper levels of the atmosphere in order to create friction that slows you down into orbit. It's not really very good for spacecraft health to do this with a spacecraft that's not designed for it. Akatsuki was not designed for it. On the other hand, you could learn quite a lot about Venus's atmosphere by doing it. But the project manager said, we have to decide whether we would have more science to gain by attempting orbit in this way and risking the death of the spacecraft, or by taking what is a scientifically healthy spacecraft and doing just a flyby mission of Venus in six years. So they've got a lot of time to make this decision and figure out what the status of the spacecraft is. So they just have to take it slowly and carefully. And just having watched the movie 2010 for the first time in many years, if you want to see a bone-chilling sequence of aerobraking, that's the movie to watch.

Check it out. Let's go farther out, out to Saturn. And I don't know about your family, but in mine, there is always someone, usually a particular uncle, who needs to be in every photo. Kind of the same thing happened to Enceladus the other day. Yeah, the kids these days call it photobombing. And Mimas photobombed Enceladus during Cassini's recent flyby. The spacecraft was taking photos of the plumes against blackness of space with the sun nearly behind it. So that's the geometry where you can really light up Enceladus' plumes.

And boom, all of a sudden, Mimas wanders into view. What's interesting to me about this picture, apart from the fact that it's just really cool, is that Mimas and Enceladus are very close to the same size. But in the picture, they don't look the same size because Enceladus is so much closer to the spacecraft than Cassini is. Do you have any idea how far apart they were actually in that photo, one orbit inside the other? I actually, well, Mimas and Enceladus have adjacent orbits, but, you know, depending on the geometry of Cassini and the two moons, it could be anywhere in the neighborhood of, you know, a couple tens to a couple hundreds of thousands of kilometers.

It's not a bad group shot, and you even include the original so people can see the magic that you did to make it look as pretty as it does. It's all in the blog. We'll put up the link. Finally, that Advent calendar, doors just keep opening. That's right, and mine's a non-denominational Advent calendar. I'm carrying on opening doors right through to the New Year. New Year is what I'm aiming for, so keep returning to the blog until January 1st for the last image in the Advent calendar. Thanks, Emily. Look forward to talking new year. New year is what I'm aiming for. So keep returning to the blog until January 1st for the last image in the advent calendar.

Thanks, Emily. Look forward to talking to you and Bruce next week when we will review 2010 and look forward to 2011. Emily Lachter-Wallace is the Science and Technology Coordinator for the Planetary Society and a contributing editor to Sky and Telescope magazine. Bill Nye is up next. Then Linda Spilker takes us back to Saturn. Telescope magazine. Bill Nye is up next. Then Linda Spilker takes us back to Saturn. Hey, Bill Nye, the planetary guy here. We're always looking for ways to get into space more cheaply, using less fuel, including more people around the world. Well, the National Aeronautics and Space Administration, NASA, has run another test very successfully of the scramjet. has run another test very successfully of the scramjet.

The scramjet, what's that? Okay, here's the idea. There's a jet, jet engine, goes along, pulls in air from outside, compresses it with these fans, and then sets it on fire with a greater air density, more oxygen molecules per cubic centimeter, and it burns hot, and the jet goes down the runway and flies around the world. All good. Well, suppose you could get rid of the fans and just ram the air in there. Well, you can do that with a ramjet,

but you have to get going pretty doggone fast for the air to get compressed enough. Wait, wait, there's more. The scramjet brings the air in at supersonic speed. This is faster than molecules travel between me and the microphone, between your speaker and your ear. And then they get hot. They shock. They go into a place where they don't want to go any faster and they get really hot. And you exploit that hot place to make the scramjet scream. That is to say, to go really fast. So this latest test of the X-43 went over 10 times the speed of sound. That's pretty cool. Well, then how would you get it up that fast to even start with? Well, here's the

idea. Use this electromagnetic field to shoot the rocket down this rail, like a railroad, till it's going really fast. Then you turn on the scramjet and then you go around the world in about two hours. That would be pretty cool. So even though the old X-43 tumbled and fell apart because the materials aren't yet strong enough, the test was pretty successful. This could change the world. This is exciting. This sort of technology could become commonplace in the next few decades. I get got to fly really fast. Bill Nye the Planetary Guy. As you regulars know, Linda Spilker is now the project scientist for Cassini,

the giant spacecraft that has been circling and revealing Saturn, its rings and its moons, for six and a half years. Cassini is now well into its extended, extended mission phase. Solstice Mission is a much catchier name. We like to get Linda on Plan Rad at least a couple of times a year, and that time has come again. This time she called me from her office at the Jet Propulsion Lab, where she and the rest of the Cassini team manage the mission

and regularly serve up the most amazing data and images from the great ringed planet. Linda, welcome back once again. One of your regular visits to update us on the Cassini mission, and happy holidays. You're here for our very last show of 2010. Well, happy holidays to you too, Matt. I'm happy to be here. And we have lots to talk about. We'll start with this.

It came up in conversation with Emily on last week's show, and that is this pretty exciting thing which has turned Emily from a skeptic into almost a believer, a believer in ice or cryovolcanoes. Oh, that's great. That's great. Yes, from some radar images that we made of the surface of Titan, we could make a three-dimensional topographic map. And in looking at one of these maps, we noticed that there was this peak about 3,000 feet tall. It's about 70 kilometers across at the top, and also it had a depression next

to it. And we started thinking about it, realizing, hey, this is our best evidence to date of a cryovolcano, or basically an ice volcano, icy material, a slushy water-ice mixture made with some gases in it, coming out and putting flow patterns down on the surface of Titan. It's almost geology or titology or whatever you would call it there that is making everyone think that, yes, we found one? Right, right. In the Sotra region, Sotra Facula is what it's called,

we think we now have perhaps one or even maybe a series of volcanoes with a tectonic feature along with it, very similar to some of the volcanic activities that we would see on the Earth. So that's a very exciting find for us. And yet, of course, this is a very different, well, is it a different mechanism? I mean, we're talking about very, very cold stuff instead of molten magma. Right, right. It would be basically something inside of Titan is warm enough to melt the ice, produce liquid water or liquid, a very runny kind of hydrocarbons, and those would come out and flow through

the volcanoes. And what's also very exciting is that this process then is a way to get methane into the atmosphere of Titan. We know that Titan's atmosphere has methane, that the sunlight breaks down the methane, We know the Titan's atmosphere has methane, that the sunlight breaks down the methane, and over about 10 million years, all of the methane would be gone if there wasn't some way to replenish the methane. And these cryovolcanoes or ice volcanoes present one way to get the methane from inside Titan into Titan's atmosphere.

So Cassini solves yet another mystery out in the Saturnian system, it sounds like. Right, right. So certainly it's just very tantalizing, and we're hoping to, as we go through the next seven years of the Solstice mission, to look for other examples of ice volcanoes on Titan, and to watch and see if maybe we'll catch some activity. We don't know how long ago these volcanoes were active. It could have been a very long time ago. But with Cassini, we're going to keep an eye on it and see if we see any changes. Another advantage also of having a long-term visitor in that system. Let's look to another moon. No ice volcanoes there, but some pretty active features.

And, of course, we've talked about Enceladus and its jets before. Did you get a better look at the base of some of these tiger stripes? Yes, we got very close to Enceladus recently, and we're able to make a very detailed thermal map along one of these cracks or tiger stripes and got some of the highest temperatures that we've seen so far. Temperatures are around 170 Kelvin. That's about minus 150 degrees Fahrenheit, so very warm activity. And so we're seeing now perhaps more about the very narrow regions from which this material is coming in. And actually, it's

interesting. Enceladus does have cryovolcanoes. It's just that they don't develop into these huge peaks like we see on Titan. But there's certainly some process warming up part of the interior, turning it into liquid water. And then this water and ice shoots out of the tiger stripes. So really, I was wrong. These are not so different from this ice volcano you may have found on Titan. Right, right. this ice volcano you may have found on Titan. Right, right.

The difference is that the material is coming out, and it just doesn't build up into a classic volcanic mountain shape. And you're still flying the spacecraft right through these things. Right, right. We have a number of Enceladus flybys coming up over the next several years. And, yes, we go very close flying through them. Literally, you can think of touching and tasting the material coming out of these fissures on Enceladus. Let's head inward toward the planet, but we won't quite get there yet.

We'll stop at the rings, which I know are a personal favorite of yours. And I did see a piece just recently, I think it was a couple of guys who've come up with a new theory that may explain why the rings look the way they do and are made of what they are. And not surprisingly, they relied on your Cassini data. Yeah, what we found with Cassini and also knew a little bit about from Voyager back in the 1980s is that Saturn's rings are mostly water ice, probably 95% or more water ice. And the question is, how do you form rings made of such pure material? We had some ideas that maybe a comet or a moon got too close to Saturn and was torn apart, but that still doesn't explain how you could get such a pure water-ice mixture. And one theory that's floating around now is that perhaps a Titan-sized moon evolved,

its orbit evolved inward towards Saturn when there was still a lot of dust and gas in the Saturn system. And as it got closer to Saturn, Saturn's gravity literally pulled it apart. This moon had differentiated, which means that the rocky material had gone toward the middle of the moon, leaving very pure ice on the outside. And as this moon got closer to Saturn, perhaps Saturn's gravity tore off the ice mixture as it got closer, and then the rocky fragment then fell on into Saturn's atmosphere and burned up there. And so you would leave then a disk of nice icy material to form the rings. And you might even have some left over to form some of the inner moons in the Saturn system, some of which have

very, very low densities, which just means they're made of a lot of water ice as well. That's Linda Spilker, the project scientist for the Cassini mission at Saturn. We'll hear more from her when Planetary Radio continues. Bill Nye the Planetary Guy here. On behalf of all of us at the Planetary Society and Planetary Radio, thanks. We're in our ninth year of this show, so thanks to all of you who join us each week as we explore the universe and do what we can to, dare I say it, change this world. Perhaps you want to join this band of planetary brothers and sisters. I don't want you to lose control, but a gift of $50 or more will get you a Planetary Radio t-shirt. That, along with our great interviews, Emily Lakdawalla's timely and fascinating updates, Bruce and Matt's What's Up segment, and my own modest contributions to the series.

So if you're of a mind, you may want to click around planetary.org slash radio, download a few past episodes and learn more about your place in space. So once again, thanks. And everyone on the staff at the Planetary Society says, Happy Holidays! Welcome back to Planetary Radio. I'm Matt Kaplan. Linda Spilker has returned to the show with lots of holiday goodies delivered directly from Saturn, its mysterious moons and its beautiful rings. Linda is the project scientist for this enduring mission.

That means she's the boss and the person most responsible for getting the maximum amount of science out of the spacecraft while making sure it stays safe and healthy. We were talking before the break about a new theory that may explain why those rings are mostly water ice. How is this new theory of the ring formation being received by other scientists like yourself? Well, I think it's a very interesting new theory, and this new model does explain the icy composition of the rings. And we'll be looking to see if we can find other clues, perhaps, that something like this might have happened by looking further into the Cassini data. All right, let's go right down to the planet itself. And you were telling me,

just before we started recording this conversation about these interesting events. You called them plasma explosions that somebody came up with a hypothesis that I guess has been proven not to be. What's going on with these? We had what we thought was the rotation period or the length of day on Saturn. And then with Cassini and also going back to Voyager measurements, we realized that this period appeared to be changing, which meant that Saturn would have to be either speeding up or slowing down. Not likely. Very, very hard to do with the planet that week. So we started

looking for other answers. And one of them is that there are periodic explosions of a hot ionized gas that we call plasma. And these periodic explosions, you can think of it like an unbalanced load of laundry that spins around and thumps in a very periodic way. And we now know that the period of this signal is exactly what we thought might have been Saturn's rotation rate. So we sort of answered the question of how, why did Saturn's period appear to change? It's because it was a different phenomena not linked to the planet. But now it really leaves open the question of what really is the length of Saturn's day.

Does anybody have any idea what is generating these explosions? Well, we think that what might be generating the explosions has to do with Enceladus. Enceladus is putting out a lot of water ice and water vapor that is what we call a cold plasma. It can get ionized. Once it's charged, it's picked up by Saturn's magnetic field and this cold plasma, what it might do is you can imagine like a dripping faucet. This cold plasma stretches the magnetic field. They snap back, heats up the plasma, and then this blob of plasma goes down the tail. In a very periodic way, much like drops of cold plasma would be like drips of water from a water faucet.

So that's one possible idea, but it probably is related in some way to Enceladus. Enceladus seems to be doing a lot of things in the Saturn system. This little moon is just full of surprises. Right. It's coating the other moons with this icy material. It's creating a ring, and it's a very fascinating place to go back and visit. How is the spacecraft doing? Is it healthy? We're healthy right now.

We had a little bit of a scare. We had a safing, And that just means that the spacecraft stops what it's doing and waits to hear back from the Earth. And it turns out that there was a command that was going on the spacecraft that was corrupted. Two of the bits were flipped. The spacecraft didn't recognize what it was supposed to do with this command. And it was a vital enough command that it decided to stop everything and then just wait to hear from the Earth. So once we figured it out, got that all straightened out,

the spacecraft is healthy and operating normally again. That's a prudent move by the spacecraft, a good programming by somebody there. Is it possible that these bits were corrupted by one of these cosmic ray hits that wreaks havoc now and then with spacecraft? Yeah, that's a possibility. We really don't have a good idea for what happened, but certainly a cosmic ray hit is one possibility. We've got a little bit of time left.

Can you give us an idea of what we can look forward to from Cassini in 2011? Well, we're going to continue to have flybys of Titan and continue to map the surface with the radar. We've mapped about 30% of the surface so far, so we'll be able to continue to do that. We have more Enceladus flybys coming up in the new year, as well as some flybys of some of the other icy moons. And then, of course, just continuing to orbit and observe the planet and the rings themselves. As always, absolutely fascinating.

And our congratulations to you and every other member of the Cassini team. May it continue to tell us about the Saturnian system for many more years in this extended, extended mission. Thank you very much, Matt, and Happy New Year. Same to you. And I also hope that we can keep checking in with you maybe two or three more times in the coming year as you

get more of this great news. Oh, absolutely. It's always great to share with everyone just what Cassini is up to now. Thanks, Linda, very much. Linda Spilker is the project scientist for the Cassini mission, still out there doing amazing science, circling the planet

Saturn and telling us so much about what appears, I would say, even more and more like a miniature solar system of its own, full of mysteries still yet to be solved. We'll hope to solve a mystery or two about the night sky when we visit with Bruce Betts in just a few moments. Hey, Bruce, Merry Christmas, Happy Holidays, Happy New Year. Hope you're having a great time. I am. Happy Holidays, Happy New Year to you as well and to all of our listeners. Why, that's Bruce Betts. He's the director of projects for the Planetary Society. You can tell us what's up. Jupiter dominating the evening sky, bright star-like object over in the east. I'm sorry.

If you're upside down. Over in the west, after sunset, brightest star-like object up there, hard to miss. In the pre-dawn sky, Venus. That's over in the east, and high above it is much dimmer Saturn. We also have a partial solar eclipse I want to give people notice on that will occur on January 4th. Not for us, Matt. Not unless you're going to road trip. I think we need to make good because there was no way we were going to see that lunar eclipse. That's for sure. I saw a lot of clouds and rain though. Europe, or at least much of Europe, North Africa, Central Asia, they will all be able to see it. Go check out a website to get the

details on time and what it'll look like from your location and exact times. NASA's got a nice solar eclipse website and there are many others out there. The greatest eclipse will occur at 851 UT in northern Sweden. So that's where I thought we would go. Yeah, I'm ready. I'll pack my bag. I've got warm socks. We also have a meteor shower. The quatrantids, the ones I always have trouble pronouncing, peaking also on January 4th, although you'll want to look for them at nighttime. That's what I'm here for, these helpful little tips. Let's go on to less depressing topics since we miss all this stuff. We have to be happy for our listeners out there who are in the right places with the right weather. Nah, the heck with them.

That's good. I, the heck with them. Bah humbug. That's good. I'm going to use that. We move on to this week in space history. In 1957, this week, Wernher von Braun proposed the Saturn series of launch vehicles. How'd that go? How'd that go over? They were mildly successful.

Anything else? They were very successful. wildly successful. Anything else? They're very successful. And speaking of successful, Stardust encountered Comet VILD 2 in 2004, collecting comet dust samples as well as taking lots of other data

and eventually returning those samples to Earth. Very, very successful. I'm just VILD about that mission. I'm just VILD about you. That's an honor of Werner, by the way. Werner Wild! So what's the next segment? Oh!

I hear you got another something. Brandon Cook, you haven't heard this yet. Wait till you hear. Brandon, consider how random we are. It's time once again for Random Space Fact. How do we know it's truly random? Well, first, each fact is assigned a number. That number in turn is fed into a random number generator.

The number is then divided by pi and then multiplied by Planck's constant. The results are baked at 350 degrees for 25 minutes. The numbers are processed at supercomputers at Kaplan University. The results are then fed into a mass spectrometer. Emily Locke-Dewalla processes the raw data. The results are then suspended in a Bose-Einstein condensate and accelerated at high velocities at the LHC. Bill Nye then reviews the results to guarantee that they're random. Glitter paint is then added for final presentation.

This fact is truly random. My gosh, I'm disturbed. That's supposed to be completely secret how did you find that out no no i think it was wiki leaks even down to the boz einstein condensate we go to incredible lengths we're gonna have to totally change the process anyway brandon you you've done it again uh congratulations and thank you. And we enhanced that with Bruce laughter in the background this time. I would have been laughing harder, but I wanted other people to actually be able to hear it. There are at least two and up to five solar eclipses each year, but no more than two can be total eclipses.

Totality only occurring in very small locations during the year, so they seem even rarer than that. Who makes up these laws? Jeez, I can't give out that process, too. We already have the other one discovered. We'll save that for another week. We got to go right on to the trivia. All right. In the trivia question, we asked you, during the Apollo program, how many parachutes failed on actual flight missions? How'd we do, man? Well, I think we were kind of holiday light this week in spite of a pretty good prize.

Jeff Windsor. Jeff Windsor of, get this, Dripping Springs, Texas. Wow. Yeah. Jeff came up with it. Apollo 15 was the only Apollo, as you put it, actual flight mission on which a parachute failed. And they were just fine because it can come down okay under two of those big puppies. We did have a couple of other interesting things. David Kaplan found a failure in a test drop from a B-52. But it was good old Lindsay Dawson down under who discovered that there was a mission, A-001,

which went up on a fairly small, solid-fueled rocket. Only went up about nine kilometers, but it also had a parachute failure. But thank goodness, only one and only one parachute on an actual human- I was really just looking for space missions, but I suppose I technically said actual flight missions. Well, Jeff won, and he's going to get that Year in Space desk calendar, the source of all of your This Week in Space facts. As well as having all sorts of cool pictures, and also a calendar. Yeah, that too,

and an article by both both of us actually separate articles by us brilliant how about next time it's been a while since we played where in the solar system so people tell us where in the solar system can you find something I just enjoy saying? Noctis labrinthus. Ooh. Noctis labrinthus. What world? Go to planetary.org slash radio, find out how to enter. Sounds like something out of the life of Brian, doesn't it?

You have. No. Not really? You have until the 3rd of January, 2 p.m. Pacific time on that Monday, January 3rd. And what a pair of prizes we have. We're going to give away the 2011 Year in Space calendar. But, but, how about... There's more?

Yes, a signed copy, signed by Mike Brown, the author, of his new book, How I Killed Pluto and Why It Had It Coming. And he will, once we get the name of the winner, he'll actually dedicate it or sign it over to that winner. So you won't want to miss out on this one. Do you hear the dogs next door? They're excited because Pluto's involved. Try to tell them it's not that Pluto.

He did not kill that Pluto. That would be just disturbing. Say goodnight, Bruce. All right, everybody, go out there, look up at the night sky, and think about what might make you laugh in 2011. Thank you, and good night. I think I've got a good start already. He's Bruce Betts, the director of projects for the Planetary Society, and he joins us every week here for What's Up.

Down boy. The video Bill Nye and I made about the SOFIA infrared telescope is now available right on the Planetary Society homepage, planetary.org. I hope you'll check it out. Planetary Radio is produced by the Planetary Society in Pasadena, California, and made possible in part by a grant from the Kenneth T. and Eileen L. Norris Foundation. Happy New Year! Редактор субтитров А.Семкин Корректор А.Егорова