Planetary Radio: Space Exploration, Astronomy and Science - Flying Through the Geysers of Enceladus

Episode Date: March 31, 2008

Flying Through the Geysers of EnceladusLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Flying through the geysers of Enceladus, 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. to us on how those plumes smelled and what we're learning about the forces that power them. We'll also speculate about the chance of life below the surface of Enceladus. Emily Lakdawalla will tell us how Cassini's path through the Saturn system allows it to do such amazing things. Bill Nye the Science Guy has learned that more than half the stars in our galaxy may have rocky planets circling them, planets that could be like Earth. And Bruce Betts looks out halfway across the universe at the brightest light

anyone has ever seen, up there with the regular cast of characters in our What's Up Night Sky report. So where's Alan Stern? Some of you may have heard me say that NASA's Associate Administrator for Science would be our guest on this week's show. Well, that was before he announced his resignation. Alan has taken a rain check on his return to planetary radio, but we expect to have him back in our microphone before long. Here's part of what Lou Friedman, Executive Director of the Planetary Society, had to say about Dr. Stern's service. During his tenure, Alan made significant changes that have helped restore the importance of science in NASA's mission.

He also worked to undo the separation that has occurred between science and exploration in previous years and redirected the Mars program to focus on Mars sample return. At the same time, he was working under extraordinarily difficult budget constraints, dealing with many issues beyond his control. We wish him the best in his future work. The full statement is at planetary.org. Welcome home, Endeavor. The shuttle and its crew return to Florida after 16 days in space and a record five spacewalks at the International Space Station. Here's Bill Nye. Hey, Bill Nye, the planetary guy here, vice president of the International Space Station. Here's Bill Nye.

Hey, Bill Nye, the planetary guy here, vice president of the Planetary Society. And I hope you, as a listener to Planetary Radio, as a reader of the Planetary Report, as a user of planetary.org, have noticed that the planets in our solar system, Mercury, Venus, Mars, Saturn, Jupiter, all follow each other, all go through roughly the same path.

They go along the same plane in the sky above us. That's because they were all formed from the same disk of gas. And I asked my old professor Carl Sagan about this. You see, our planets were formed by gravity, by the gravity of dust. That's right, even on bookshelves, the dust is pulled to the shelf, as well as the shelf being pulled ever so slightly up to the dust. And you see, this dust formed a disk, and within that disk are little whirlpools, and those whirlpools are us. They become the planets, because as the dust comes together in space, it's going to have some what we call angular momentum. It's going to have some off-center spin, some imbalance, and that becomes

a flat disk like a compact disk or a digital video disk or one of those old vinyl records. Well, as astronomers look at the disks on other stars, the proto-planetary disks, the before-planet disks, we have observed now that at least 20% and perhaps as much as 60% of those disks are set to form rocky planets like ours instead of big gas giants like Saturn and Jupiter. Oh, they're out there at five astronomical units, but 20 to 60, maybe as much as half of those disks are going to become rocky and perhaps Earth-like planets. You see, this greatly enhances the chances of finding a planet that might have life.

If we found that, my friends, it would change the world. So keep an eye on your protoplanetary disks. This is Bill Nye, the Planetary Guy, for Planetary Radio. On March 12 of this year, the Cassini spacecraft came within a hair's breadth of Saturn's moon Enceladus, just 52 kilometers, or 31 miles, above the surface. What's more amazing is that it flew not once but twice through the jets that spew from the little moon's south pole. Two weeks later, members of the Cassini science team were ready to report their early findings about that flyby, which allowed instruments like the ultraviolet imaging spectrograph and the ion and neutral mass spectrometer

to almost literally taste the fountains of gas and dust. John Spencer of the Southwest Research Institute's Department of Space Studies is a member of the Cassini science team. We asked John to return to Planetary Radio to talk about what Cassini has told us about this moon and its surprising geysers. John, that was one exciting event that you guys on the Cassini science team were able to report on last week. What are we looking at with Enceladus? Is this just one big comet circling Saturn? Oh, no, it seems to have some things in common with a comet. As we were saying, it kind of smells like one or tastes like one,

but it's definitely very different from any comet we've ever seen. I think the biggest difference, the most obvious one, is that comets are powered by sunlight warming the surface, and that causes the ice to evaporate. And Enceladus has internal combustion, and there's something going on inside there that is producing the heat. There's no way that ice would evaporate on its own at that distance from the sun.

The process of these jets expanding supersonically into the vacuum of space is pretty similar to a comet, and it looks like there are some intriguing chemical similarities. We're not quite sure what to make of that yet. And, of course, it's bigger than any comet we've ever seen, but it's really a rather remarkable thing that we're trying to deal with here and trying to figure out. Well, let's start with that heat,

which the instrument that you're on the science team for, the composite infrared spectrometer, during this flyby you were able to map these hot streaks on Enceladus with much higher resolution and gave them interesting names. Well, I can't take credit for the names because those were already assigned by the International Astronomical Union. Yeah, the names of the four tiger stripes, which is the informal name that we've been using since we discovered them, I guess it's three years ago now almost, their official names are Damascus,

Baghdad, Cairo, and Alexandria, which are named not after recent news stories, but after places mentioned in the Arabian Nights, way back in Voyager days, it was decided that place names on Enceladus should be taken from the Arabian Nights. Each of the moons in the outer solar system has a naming theme. So we have, I think, King Arthur on Mimas, North Gods and Legends on Callisto and so on. It's interesting. They're all in, these are A, B, C, D in their initial letters, but they're not in alphabetical order, which causes confusion. Nevertheless, they are hot spots or hot streaks,

much like their earthly co-named places. Right. This is the first time we flew past when we actually knew in advance what we were getting into and what we were going to be looking for. We got enough data on the flyby in July 2005 to know that the area of the Tiger Stripes was warm. We got a few scattered views from closer up to see that the heat seemed to be concentrated along the fractures. Whenever our field of view crossed the fracture, we'd get a spike in the heat. But we didn't get any kind of comprehensive map. So our number one priority this time was to cover as much of that south polar tiger-striped region

with our thermal mapper as we could in the very limited time we had available. And we got about 85% of it. We missed a little bit on one side. We just didn't have time to do the whole thing. But we were very pleased with what we got, and we confirmed that we really do have all this heat coming out along these major fractures. A few additional fractures nearby are also active. So we have this great map now of where the action is on Enceladus and a great roadmap for planning what we do next and where we look at in more detail next. and a great roadmap for planning what we do next and where we look at in more detail next. There is a large illustration in the article written by my colleague Emily Lakdawalla at Planetary.org that overlays the approximate locations of these plume or geyser outlets,

and they line up pretty well with your tiger stripes. Indeed. We've known for a while from work done by people on the imaging team that the individual geyser jets, to the extent that you can separate them out, it's a complicated three-dimensional problem looking at that forest of jets and trying to sort out which is closer to the spacecraft, which is further away. Anyway, they were able to look at that and identify, I think, eight individual prominent jets that you could see in multiple images and triangulate and see where they were on the surface. Those do all line up very nicely with the Tiger stripes. They tend to be in the warmest regions

of the Tiger stripes. So it's not perfect, though. Some of the warmest regions do not include the major jets. But there's one area which, by good luck, we happened to look at particularly closely when we were at our closest to Enceladus, which has both some of the most intense heat and two of the major jets that have been identified. And we really looked at that closely and got some very nice temperature measurements from that region. Let's turn to some of your colleagues there, the folks who work on the INMS and the UVIS instruments, who were pretty amazed by the composition of these gases that your spacecraft flew through.

Yes, because we now knew the plume was there, we knew where it was, and we decided there wasn't too much hazard to the spacecraft. We were able to fly the spacecraft directly into the plume. Last time we went by, we just skirted the edge of it, and it whetted our appetites. We got some very interesting compositional information, but this time, flying through with a mass spectrometer, we got fantastically better quality data. It was really spectacular stuff. There was just so much more gas to analyze going closer. And so there is a much more detailed view of the composition of this thing. And yeah, it's dominated by water vapor, which we knew from the previous observations. And there's methane, carbon dioxide, and then there's all these organic molecules,

really some pretty interesting looking organic molecules. I'll say, yeah, there's a little list of some of these in Emily's article and showing their rough, the rough proportion of their presence within the plume. It's pretty amazing what was found. Yeah, I mean, there's a real chemical factory in there. That's John Spencer of was found. Yeah, I mean, there's a real chemical factory in there. That's John Spencer of the Cassini Science Team. John will tell us more about the recent Enceladus flyby 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 that reach around the globe. I'm proud to be part of this greatest of all voyages, and I hope you'll consider joining us. 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. Our nearly 100,000 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.

The Cassini probe continues its exploration of Saturn, its rings, and its moons. Just three weeks have passed since it skimmed the surface of the 500-kilometer moon called Enceladus. Staff scientist John Spencer of the Southwest Research Institute continues his recap of what Cassini's instruments have revealed about the plumes of gas and dust that emerged from the moon's south pole. We now know that, in addition to water, there are lots of organic molecules, including some that are fairly complex.

I asked John what it all means. It's very early days to try and figure out what this does mean. As Hunter Waite, who is the team leader for the INMS, said in the press conference, it's kind of commentary, and that's very intriguing because Enceladus is a geologically very evolved body. To really have this to be directly comparable to what's in a comet, you'd have to put all this material into Enceladus very early in its history and not really touch it very much. And then let it vent out again all these billions of years later. You look at the surface of Enceladus and it doesn't look like it's been

sitting quietly all this time. It's an intensely contorted, disrupted surface. There's been enormous geological activity there. Of course, we're seeing all this heat coming out. And the heat we see at the surface means it's probably even warmer lower down, so you'd expect a lot of chemical reactions to be going on. So the fact you end up with something that looks kind of primitive is very intriguing, and it may be just coincidence, or it may mean that we really have no idea at all what's going on down there. The one thing that we really need to sort out and don't have a clear answer on yet is the way mass spectrometers work. You only measure the mass of a molecule rather than its actual composition. And it just, by coincidence, carbon monoxide and nitrogen, which are both quite common in the solar system, have the same mass, 28 mass units.

And it's kind of hard to tell those apart. From previous observations, it had seemed like that detection in the mass spectrometer was probably nitrogen. But now with the new, much higher quality data, they're saying, no, it really looks like carbon monoxide. That's kind of more cometary because comets tend to have more carbon monoxide than nitrogen. And that's definitely pushing us in the direction of this cometary picture. But the other instruments aren't seeing carbon monoxide, and it could be they're just not sensitive enough or that we're still confused about what's going on.

But we'll have ways on future flybys that we can sort this out. We'll have definitive tests, and in a year or maybe at the outside, in two years, I think we'll have that sorted out. And that next flyby is not very far off. August 11, I think, is what it's set for. And hopefully this other instrument that there was a software problem with will be operating by then. That's right.

That is the Cosmic Dust Analyzer, a German instrument, which has been producing fantastic data on the composition of the plume particles, not the molecules, but the actual ice grains. They're mostly water, but they have other stuff in them. And just flying through the earring, which we now are convinced is composed of debris spouted out of Enceladus' geysers, they're seeing very interesting patterns in that. So it was really going to be exciting to look in close and see how those, where you had this really high-quality sample to see what the composition of those grains was.

And, yeah, we were all very disappointed that they had this software glitch and were not able to get data. But because it's a software problem, there's nothing wrong with the instrument. They ought to be able to fix it by the next flyby, and they will be having another shot at it then. The next flyby actually is, this flyby was designed, the close approach part, for measuring the composition of the plume.

It was not designed for taking high-resolution pictures, so the pictures we got were relatively low-resolution. Part of this is because after the flyby, we were in certain shadows, so there was no illumination on Enceladus. The next flyby occurs in sunlight, so we will be able to take very high-resolution pictures, and that will be the focus of that flyby for the close approach period.

But that still will allow the dust detector to get some science, and they will try and do that. And then in early October, the flyby after that, again, will be one dedicated primarily to measuring compositions, and they should, again, get really nice data then, as will the mass spectrometer. With only about a minute left, I hope you won't mind if we go really out on a limb with speculation here. I guess astrobiologist Chris McKay looked at these results and said, well, we have water, we have a source of heat, could there be life

underneath the surface of Enceladus? He said, yeah, there could be, but we're not going to learn this from Cassini. Probably not. We would like to have more sophisticated instruments that can look for more complex organic molecules. You'd love to be able to study individual ice grains and maybe see if there's biological structures in there. There's all kinds of things that could be done to look at this. But as habitats go in the solar system, it's one of the most promising we've got for a place that life could exist. It's really very exciting.

I've got to ask one more question because you said just before we began that you just came back from JPL, partly because you were there working on what could be the next mission to Jupiter? That's right. NASA's been considering missions to the, follow-on missions to the outer solar system for quite a while, and one idea that's been around for a long time is the Europa orbiter, because the Europa is also very interesting from an astrobiological point of view, because we think it has an ocean, and we want to go back and learn more about the crust and the ocean of Europa.

So NASA is now getting these plans quite detailed, and we have a large science definition team that's coming up with the science questions we want to ask on such a mission and how we might answer them. And we're hoping that late this year NASA will make a decision as to whether to fly the next outer planet mission back to Europa, back to the Jupiter system, or back to Titan. So there's a parallel effort going on for Titan at the moment. Well, John, best of luck. It is a delight to speak with you once again, and we look forward to doing it one more time sometime in the future.

Who knows, maybe after that next flyby of Enceladus in August. Thank you. It's been great talking to you. John Spencer is a staff scientist in the Department of Space Studies at the Southwest Research Institute in Boulder, Colorado. Prior to that, he was an astronomer with the Lowell Observatory, and he's a science team member on the New Horizons mission, which is still making its way toward Pluto. We will be right back.

We'll make our way, that is, to Bruce Betts for this week's edition of What's Up after we check in with Emily. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, Which would give Cassini a better view of Saturn's equinox, an orbit in the plane of the rings or one out of the ring plane? When the science team wants Cassini to focus on the icy moons in orbit around Saturn, it's best to have Cassini orbit in the same plane as the moons and rings

because that increases the chance of moon flybys. around Saturn, it's best to have Cassini orbit in the same plane as the moons and rings, because that increases the chance of moon flybys. But for most of the other scientific disciplines, it's best to have Cassini flying above and below the ring plane in an inclined orbit. Cassini arrived at Saturn during late summer in the southern hemisphere, so since the mission started, the Sun has illuminated the south poles of Saturn and its moons, and the southern face of Saturn's rings. The equinox arrives in August 2009. The coming of spring to a planetary hemisphere always brings big changes, but the changes should be even more dramatic on Saturn's rings,

because the entire ring plane sees only one sunrise and one sunset every year. The greatest drama should happen in the most opaque ring. The blocks of rock and ice that make up the densest B ring are so tightly packed that they don't travel from the day side of the rings to the night side of the rings as they orbit Saturn. That means that the day side of the rings is nearly 100 degrees Celsius warmer than the night side. When the sun rises on the north side of the rings, we'll see all of that change, and it could have surprising effects. When the equinox comes, Cassini will be near its closest approach to Saturn, and on the south side of the rings,

watching the sun set. Just hours after the equinox, Cassini will pass to the north side and be able to watch the sun rise over the north side of Saturn's rings for the first time in 15 years. Got a question about the universe? Send it to us at planetary radio at planetary.org. And now here's Matt with more Planetary Radio. It's time for What's Up on Planetary Radio. That means we're joined by Bruce Betts, the director of projects for the Planetary Society. And Bruce, welcome back. We're talking via Skype. Good to be back, Matt.

Daniel Kaplan, a regular listener. He wanted to get in equal time for Vonage because he works for Vonage and we only mentioned Skype. So there you go, Daniel. That's all you're going to get. He can get more if Vonage would like to underwrite the show. That's right.

You could beat Skype. What's up? Well, we've got in the evening sky, Mars high overhead, but towards the west in the early evening above Orion, getting dimmer and dimmer. Still looks like a bright star, but towards the west in the early evening, above Orion, getting dimmer and dimmer. Still looks like a bright star, but not that bright and looking orange, orangish-reddish.

And Saturn over in more towards the east in the early evening, also very high up in the sky, also making a lovely telescopic object. Pre-dawn sky, we've got Jupiter over in the east, looking like the brightest star-like object over there. You can also check out things like International Space Station going overhead, or Hubble Space Telescope, or any number of other objects. I'd tell you where to look, but it's a local thing, or at least more local than our international show. You can go to various websites to get predictions. One that we use a lot is www.heavens-above.com. And it's very cool. We did it the other night, checked out the space station going overhead,

which is particularly easy to see looking like a bright star going past overhead. Big, big mother. It is. It is big, and it gets as bright as the brightest star in the sky. Let us go on to this week in space history. Forty years ago was the launch of Apollo 6, the last of the unmanned Saturn V tests, where they put humans back in them.

And then 35 years ago, the launch of Pioneer 11, the sister craft to Pioneer 10. On to random Space Fact! You're feeling much better this week, aren't you? I am. I'm feeling so much better. Gamma Ray Burst. So this is just such a weird random space fact to me. Normally, the farthest object you can see with the naked eye is the Andromeda

galaxy. An amazing, a staggering two and a half million light years away will appear as a fuzzy patch of light if you've got fairly dark skies. A few weeks ago was observed a gamma ray burst, which they, of course, observed first in gamma rays, which we can't see. But the effect of that gamma ray burst causes a – it heats up and all the dust and gas around it, and there's actually a visible burst as well. And this was the brightest explosion and brightest gamma ray burst ever seen. It actually would have created a visible outburst, visible to the naked eye. Now, of course, unfortunately, you'd have to be looking at the right part of the sky in the right one minute on the right day before it faded.

But the mere fact that it got slightly into the visible range, it would look like a very dim star for just a moment. The profound thing is there was a naked eye object seven and a half billion light years away, halfway back to the Big Bang. Halfway across the universe, in other words. Amazing. Pretty much.

I mean, so far beyond amazing, I truly don't have words for it. Well, okay, then that'll move our show along faster. On to the trivia contest. We asked you about the distance, speaking of distances. In this case, a shorter distance, merely the distance from our solar system to the center of the Milky Way galaxy. How'd we do, Matt?

There was an interesting range of answers this time around, and I suppose that's because we don't really know to a high degree of accuracy how far it is, but answers ranged from 24,800 light years to 30,000 light years to what I guess is called Sagittarius A, which is the ultra-massive black hole at the center of the galaxy, about which the rest of us prance on a daily basis. That's a technical astronomical term, by the way. Yeah, sometimes abbreviated as PR. At the upper end of that range was Darren Pitts. Darren Pitts out of Calgary, Alberta, Canada, who did come in with 30,000 light years.

So, Darren, that T-shirt is coming your way this time around. Michael Tiernan didn't win, but he did give us some interesting units. First of all, he told us how unscientific and unprofessional it was to talk about measuring the distance in ping pong balls. Then he gave us roughly 869 billion times 10 to the 8th smootes. Ah, the dreaded smoot. Wait, what's the smoot? I forget, but it's, you know, it's this imaginary thing from MIT that I guess is not so imaginary. But thank you, Michael.

Well, way to come up with weird units yet again, people. And the fact that, you know, in astronomy and planetary science, if you get anything within 10 percent, hey, if you get anything within a factor of two, you're doing pretty well. I love it. Better than horseshoes. And oh, so much more fun. Well, sometimes. Yeah. Let's give another trivia contest.

How about that? Back to our friend's gamma ray bursts. What was the name of the spacecraft that first detected this massive, most massive ever observed gamma ray burst? What detected it first? Name of the spacecraft. Go to planetary.org slash radio. Find out how to enter. And if you have a winning entry that is randomly selected,

you will win a Planetary Radio t-shirt. Get that answer to us by April 7, Monday, April 7 at 2 p.m. Pacific time. We're out of time. We're way out of time. All right, everybody, go out there, look up at the night sky, and think about Gumby and Pokey. Thank you, and good night. I love Gumby and Pokey.

Used to watch them on Engineer Bill. Got kind of creepy sometimes. Remember that one about the Kachina dolls? Fortunately not. Ah, you missed out. Kept me up nights for weeks. He's Bruce Betts, the director of projects for the Planetary Society. He keeps all of us up at night looking out at the

night sky and what's up. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.