Planetary Radio: Space Exploration, Astronomy and Science - News from Saturn and a New Companion for Venus

Episode Date: April 17, 2006

The Planetary Society's Emily Lakdawalla reports on the arrival of Venus Express; Cassini Deputy Project Scientist Linda Spilker has news from Saturn.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Transcription by CastingWords the final frontier. I'm Matt Kaplan. A busy show today as we take you from Earth's cloud shrouded sister all the way to the mighty ringed behemoth. There is big news from both planets. In a few minutes we'll get a Saturn update from Linda Spilker, one of our favorite solar system explorers. Linda is Deputy Project

Scientist for the Cassini mission which continues to surprise and delight denizens of Third Rock with amazing discoveries. A special report from the Planetary Society's Emily Lakdawalla is just around the bend. Our Q&A correspondent is back from Germany, where she witnessed the arrival at Venus of the European Space Agency's Venus Express orbiter. Of course, we'll also check on the night sky with Bruce Betts

and see if we can give away just one more Explorer's Guide to Mars poster. And as if that wasn't enough, there are these headlines. Is Xena, warrior princess, taking steroids? The Hubble Space Telescope has just confirmed that the proposed 10th planet, still known officially as 2003 UB313, really is bigger than Pluto, though not by much. It's a difference of 100 kilometers or so, but that difference may make all the difference to the International Astronomical Union as it debates whether the faraway object will get planetary status. The details are at planetary.org. Attention, E.T. Shine your light our way.

The world's first dedicated optical SETI instrument is up and running. You may remember our conversation with Paul Horowitz and Andrew Howard of Harvard a couple of weeks ago. Well, their big watchful eye was dedicated at an April 11 ceremony. Bruce Betts was there and will give us a quick report during his What's Up segment, and there's more at planetary.org. NASA had such a great time blasting a comet with the Deep Impact mission. Let's do it again, but closer to home this time, huh, guys? The space agency has announced a mission to our moon

that will send a two-ton impactor into a crater at the South Pole where permanent shadows may be protecting water ice. A second craft will then fly over the impact area hoping to catch a whiff of water vapor sent spaceward by the big crash minutes before. Watch for it in October of 2008. Before we move on to Venus, an apology. One or two of you reminded us of an event we forgot to mention last time. We should have marked the 45th anniversary of the first human spaceflight. It was April 12, 1961. Sorry about that, Major Gagarin. Rest assured, you're always in our hearts.

The European Space Agency is celebrating. Emily Laktawala is the Planetary Society's Science and Technology Coordinator. We talked with her shortly after her return from Darmstadt, Germany, where the Venus Express team had gathered to witness the picture-perfect arrival of that spacecraft. Emily, Mars Express, Huygens, now Venus Express, I guess Europe has good reason to be proud. They're very proud. They've got several active spacecraft now,

and they're returning to Venus for the first time in 14 years. So tell us a little bit about the experience being there in Darmstadt. Well, it's kind of funny because the last time I was in Darmstadt was for the Huygens probe landing, and the emotions were really running high for that event because it had been so long in the making, nobody knew it was on Titan, and everybody just didn't know what to expect and whether it would even work. In contrast, Venus Express orbit insertion was surprisingly routine.

They'd pretty much done it before with Mars Express because the spacecraft was nearly identical. And although they were, you know, a little bit apprehensive, they kind of expected everything to go well, and it did. So no outpouring of joy at the moment that we first got telemetry back from that orbiter? Of course there was an outpouring of joy. Everybody was very happy. But I think that they were more happy that they were just ready for data to start coming back

so that the scientists could start getting to work. So now the work does begin, and in fact, some images have already started to come back, and many of them are visible on the planetary.org website, and we'll especially refer people to your blog, which is quite informative on this and other subjects. Talk a little bit about what we're already seeing and learning from Venus Express. Well, the first images are going to be unique for the mission because they're taken from a uniquely distant viewpoint. Venus Express is going to have an elliptical orbit that goes very close to the North Pole and much more distant from the South Pole, but their very initial orbit goes about

four times as far from the South Pole as their final mapping orbit will. So this is the only time in the mission when they're going to get a really distant view where they get the whole planet in one field of view. And that is the first image that they released from the Virtus imaging spectrometer, was a view of the entire south pole of Venus looking on both its day side, the side that's illuminated by the sun in ultraviolet and infrared wavelengths, and also they can see deep within Venus' atmosphere on the night side, so they see thermal radiation coming from Venus' hot atmosphere on the night side of Venus.

There was one image in particular that was sort of a split screen between visible light and infrared that was very dramatic. That's right, and that split-screen view is actually all one observation by that Virtus imaging spectrometer. It's able to see Venus in about 200 different wavelengths. When it looks in the more visible and infrared wavelengths, or the ultraviolet wavelengths, it's seeing only reflected light from the sun. So you only see half of Venus, the side that's lit from the sun.

But when it looks in the more thermal infrared, and because Venus is a very hot place, you don't have to go to very long wavelengths to see that, only about 1.7 or 2 microns. You can see the entire planet is sort of lit up from within by the heat that's emanating from inside it. Emily, isn't there some hope with this spacecraft that as with we now have seen on Titan, there are ways to peer possibly right through those clouds down to the surface? It can. The windows aren't quite as good. And one problem with Venus is that Venus has a lot more topography than Titan does,

and the temperature varies a lot. So in order to really understand what we're seeing from the surface, they're going to have to correct for the variations due to topography. But yes, they should be able to see right down to the surface, although perhaps a little bit more fuzzily than Cassini does at Titan. We won't have much time to review this very successful mission in this conversation. We'll have to get a project scientist or someone else on from ESA pretty soon. But you did get a chance to talk to a lot of your ESA colleagues while you were there.

What is next for the Europeans? Well, it's going to take a little more than a month to get the spacecraft into its final mapping orbit. During that time, they'll be turning on all the instruments and making sure that they work individually. And then in another month following the orbit insertion, they're going to test the instruments together and make sure that when they're all operating at the same time, they work well together. And that's when they'll settle down to their science orbit, where they just start taking lots and lots and lots of data, just like any other orbiter. You won't see immediate science results coming out right in the first week.

They'll slowly be built up over the course of several years. Okay, Emily, we're out of time for this quick conversation, but once again we'll refer people to your blog at planetary.org, where they can read lots of details. You get some rest. I know you're still feeling a little bit under the weather. Our appreciation is all the greater for taking a couple minutes to join us on Planetary Radio. You're very welcome.

Emily Laktawala is the Science and Technology Coordinator for the Planetary Society in Pasadena, California. She has just returned from Germany, where she witnessed up close and personal the orbital insertion of ESA's, the European Space Agency's, Venus Express orbiter. We'll be right back with Linda Spilker, another acquaintance of Emily's. Linda is the deputy project scientist for the Cassini mission, now circling Saturn. Up next is Emily Lakdawalla with this week's edition of Q&A. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked,

Have we found liquid anything currently sitting anywhere off of our home planet? Earth is bathed in liquid water, but a search across the rest of the solar system yields few other places with liquid at the surface at the present time. In fact, there is only one place in the solar system where we have conclusively spotted actual liquids sitting on the surface, and that's Io. Jupiter's innermost large moon has extremely active volcanoes, which generate glowing hot lava lakes just like the liquid pools of lava inside some Earth volcanoes. Other places in the solar system look like they once had liquids flowing across their surfaces.

There are lots of apparently water-carved channels on Mars, methane-carved channels on Titan, and lava-carved channels on the Moon, Venus, and Mars. But none of these have ever been seen filled with liquid. Liquids are actually extremely common in our solar system, but where are they hiding? Stay tuned to Planetary Radio to find out. 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. We didn't just build it. We attempted to put that first solar sail in orbit, and we're going to try again. You can read about all our exciting projects and get the latest space exploration news in depth

at the Society's exciting and informative website, planetary.org. You can also preview our full-color magazine, The Planetary Report. It's just one of our many member benefits. Want to learn more? Call us at 1-877-PLANETS. That's toll-free, 1-877-752-6387. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio, where we are about to venture out a billion miles to Saturn.

The Jet Propulsion Laboratory's Linda Spilker joins us every now and then to report on the latest data and discoveries from the Cassini orbiter. She is the Deputy Project Scientist for the Cassini orbiter. She is the deputy project scientist for the Cassini-Huygens mission, a four-year up-close-and-personal examination of not only Saturn itself, but its many moons and those beautiful rings. The big spacecraft has stayed very busy since its companion, the Huygens probe, plopped down on the surface of Saturn's big moon Titan over a year ago.

You'll find lots of stunning images and science at planetary.org on the web. A couple of discoveries announced in just the past two weeks gave us more than enough to talk about a few days ago. Linda, welcome back to Planetary Radio. I'm very happy to be here, Matt. Well, we're always happy to have you, and I'm also happy to be able to congratulate you. Something that I discovered just before we started this

conversation. You guys, the Cassini-Huygens mission team, has gotten an award, the Aerospace Laurel Award from Aviation Week and Space Technology. Yes, we're very excited to get that. Thank you. I know that must make you feel good, but I'll bet that the science you guys are coming up with is making you feel even better.

Oh, absolutely. It is tremendously exciting, the things that we're learning with Cassini. Let's talk about one of the most recent and one of the biggest discoveries that Cassini has made, and it's about this little moon, Enceladus, and a little tiny moon, but an awful lot going on there. Oh, absolutely. The fact that this tiny moon that we thought would be frozen and dead actually has active, you can think of them as geysers, similar to what you might find Old Faithful and Yellowstone, going off, spewing water vapor out into the environment around Saturn, and now we know for sure.

Enceladus is the source of the E-ring particles that populate the Saturn system. So, as you said, nobody expected to see this kind of dynamism from such a small object. Are we pretty sure that this material we've seen geysering out is water? Yes, we are. There's an instrument, the Ion and Neutral Mass Spectrometer, when we flew very, very close to Enceladus last July, actually measured the water vapor content of the plume.

And so, yeah, we know that the main component is really and truly water. Your colleague, Carolyn Porco, who is the imaging team leader, she's at the Space Science Institute in Boulder. She said, if you're right, you have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms. Yeah, it's just incredible to think about that. If you use liquid water as the key ingredient that you would need for life. We have that liquid water there, and we also see some hydrocarbons, some simple hydrocarbons there as well.

So you might have the ingredients for life. Does anyone begin to have any ideas, any hypotheses, about how this could be taking place on this tiny moon? That's a very good question. We've sort of been searching and trying to come up with models and ideas. Maybe there's some kind of resonant forcing on Enceladus, similar to what we see on Jupiter's moon Io, which we know has active volcanoes, tidal forcing, and maybe other things have happened to Enceladus in the past. Another question is, has Enceladus been like this

since its early history, or is this something new that's just started happening in more recent times? Talk a little bit about how Cassini managed to catch these images that clearly show this material spewing out of the surface. Well, it's really a very interesting detective story that starts with the magnetometer of all instruments. They measured the field lines flowing around Enceladus in a way that was comet-like, and that gave them a clue there might be an atmosphere.

And once we knew that, we decided in July to go very close, within 175 kilometers of Enceladus. And when we did that, we found the South Pole was warm. This INMS instrument, ionineutral Mass Spectrometer, measured an atmosphere. A stellar occultation saw the plume. The Cosmic Dust Analyzer measured a whole bunch of icy particles coming out. And then, after that, we actually took some pictures at a very high phase angle where you just see a thin, narrow crescent of Enceladus. And then, bingo, for the first time in those pictures, we actually

saw the plumes. What does this discovery potentially tell us about all the other icy balls in our solar system? Well, I think one thing I've learned from it is not to take anything for granted. In other words, with Enceladus, this tiny moon having plumes, anything is possible. And so maybe we need to look more carefully perhaps at Saturn's other moons just in case there might be unexpected activity or unexpected things going on that we haven't found out yet.

I caught something else in your previous response, and that was that you decided last July to take a closer look at Enceladus, and you were actually able to redirect the spacecraft? Yes. It turns out that Enceladus is so tiny that its gravity isn't very strong, and so we could actually, I think we moved in from about initially 1,000 kilometers into 175 kilometers and could change our place we were flying and decide to go right over the South Pole to get a very good view of the South Pole.

This implies that you still have a very healthy spacecraft orbiting Saturn. Oh, we clearly do. Everything is working very well. All of the instruments are working as well as the spacecraft is, too. So we're just looking forward to several more years of taking very exciting science data, including at least one more and possibly several very close looks at Enceladus. How about Titan? Anything coming up? Any more close passes? We have a series of close passes of Titan. By the end of the mission, we'll have had 44

close flybys of Titan, and that will give us a chance to map out the entire surface. And so pretty much every month or so, we have another close flyby of Titan. And you can imagine it's like putting together a jigsaw puzzle as we get bits and pieces of Titan and trying to build up the story of this moon with this thick, hazy atmosphere and trying to understand what the surface underneath might be like. Before we run out of time, I want to bring up at least one other recent and significant discovery by Cassini, and that showed up in the form of propellers, so-called, in the rings. Right, right, these propellers. They're about three miles long, tip to tip,

and what we find is that in the middle of that propeller, right, where the center of the spinning propeller would be in the middle of that propeller, right where the center of the spinning propeller would be if it was an airplane propeller, there's a tiny moon probably about 300 feet across. And these moons are too small to open up a gap in the rings like the bigger moons, Pan and Daphnis, do with the Encke gap and the Keeler gap. But instead they open up a little partial gap, create these propellers, and the bigger the propeller, the bigger the little moon must be.

So we've sort of found an intermediate size of moons that are present there in Saturn's rings, and they leave this telltale propeller as a way to find them. Do these little guys tell us more about the formation, the original formation of the rings? Well, we think that these tiny bodies might be chunks or pieces left over from the bodies that broke apart possibly and formed the rings. So they're little pieces left over. And the rings, of course, are a good analogy for how the solar system might have formed. So by studying these small bodies forming or being present in the rings, we might learn

more about how our own solar system formed as well, how the planets formed in our solar system. What else, if anything, are you most looking forward to in the next year or so of this mission? Well, Cassini is now starting into a phase where we're increasing the inclination of the orbit. We've been in the equatorial plane for a while. We've had lots of good flybys of the icy moons. And as we raise the inclination, we'll start to get better views of the rings and of the poles of Saturn and slightly different

views of Titan. And as a ring scientist, of course, I'm very interested in going back and getting some more detailed looks at Saturn's rings. And a question that comes up, I know, for a lot of us at the Planetary Society, and I think you hear it too, is we're still not expecting to see individual particles of the vast majority of those particles that make up the rings. Yes, they're much too small. They're probably only, you know, some of the smallest, only an inch or so in size. And even these 300-feet moonlets, we don't see them directly.

We just see the three-mile-long propellers that they make instead. So, no, it would be great, though, to get a picture of an individual ring particle, but I don't think that's going to happen until we have a mission to go back and maybe just hover above the rings and take pictures of ring particles. Well, there's something to look forward to, and you've got much more to look forward to in the Cassini mission, which is far from over. And, Linda, I hope we can continue to check in with you now and then. Oh, absolutely. It's a pleasure.

Linda Spilker at the Jet Propulsion Laboratory near Pasadena, California, is the Deputy Project Scientist for the Cassini-Huygens mission. And we check in with her now and then. I bet there's more big news to come. And we'll have more about the night sky and other things from Bruce Betts right after this return visit from Emily. I'm Emily Lakdawalla back with Q&A. Where else are there liquids in the solar system besides in the oceans on Earth and lava lakes on Earth and Io. A good fraction of the large objects in the Solar System have liquids somewhere in their interiors. Very broadly, all bodies

in the Solar System are coldest at the outside where they touch space and warmest in the center. Their interiors also have much higher pressures than their outsides. Combinations of warmer temperatures and tremendous pressures can make liquid states much more likely than the gaseous or solid ones that we see on most surfaces. Earth has a molten iron outer core, and it's possible, although not proven, that such a molten core could exist inside the other terrestrial planets. Most of the biggest icy moons in our solar system look like good candidates for having subsurface water oceans.

Europa and Callisto almost certainly, and very probably Ganymede and Titan, even asteroid Ceres and tiny planet Pluto could have liquid inside. The ice giant planets Uranus and Neptune probably have mantle oceans of water, methane, and ammonia. And the gas giant planets are poorly named. The interiors of Saturn and Jupiter are probably almost entirely liquid, with mantles of liquid molecular hydrogen and cores of liquid metallic hydrogen. 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 for What's Up on Planetary Radio. So Bruce Batts is here. He's the director of projects for the Planetary Society. He has just gotten back into town. Welcome home. Last time we talked to you, you were getting on a jet plane. I was.

I was getting on, and then I got on some more coming back, yes. It went very, very well, the Opt SETI telescope dedication in Harvard, Massachusetts. So it's up and running. We're doing the search. It is up and running. They're doing the search. Right now they're doing things manually, working the bugs out of the system, but it is fully functional.

They will then eventually over the next weeks and few months move into a completely robotic mode where their software decides when to open their building and do the observations and will let them know if they trigger things. You can find out, by the way, of course, as always, find out lots more at planetary.org. And also you interviewed the key players, Paul Horowitz and Andrew Howard, two weeks ago. Yeah, people just go back a couple of weeks, you can hear a nice conversation with Paul and Andrew. Neat stuff. What is up?

Well, besides looking for E.T., we've got planets in the night sky. We're coming up on Jupiter being at opposition. I guess it's a little while. It's May, I believe, May 4th. That's when it's on the opposite side of the Earth from the sun. And if you think about it, what that means for us is when it's at opposition, it will rise at sunset or right close to it and set right around dawn. So it is rising earlier and earlier in the evening. It's a very early evening, comes up in the east, really, really bright.

You've got Venus really, really bright in the pre-dawn sky, and Mars and Saturn kicking around in the evening sky in the west, considerably dimmer, but still looking like pretty bright stars. Mars, of course, reddish. Saturn, of course, yellowish. All cool in a telescope. Now let's move on to Random Space Fact. A hundred and one variations.

Okay. That's what we're in the middle of. We're in the middle of the two-year, a hundred and one variations of Random Space Fact. This time we're talking about Mars Reconnaissance Orbiter. This beast went into orbit around Mars a few weeks ago, and a Random Space Fact on it is it will return more data,

assuming it continues to be highly successful, than all other planetary missions combined. And it's the kind of thing that keeps happening. So more and more keep returning more. Yeah, there's a very impressive graph I saw where it's something like 10 times more than the ones that return tons of data like Magellan and Mars Global Surveyor. Yeah, 40 megabyte images. Yeah, they've got a big antenna on that puppy.

It's a bigger spacecraft than the other orbiters that are there, and they've got a big antenna sending back information, at least for a Mars-distanced orbiter. So there you go. Should we move on to trivia? Yeah, we should move on to trivia. And we have to mention one thing. It has been pointed out to us since we announced shame

uh we have learned uh or had confirmed once again how terminally unhip bruce and i are because we have learned we're groovy man we thought we had we were given such a cool innocent little name for the new spot on jupiter and uh we've since learned that it is a euphemism, a bit of slang, for a quite normal human bodily function. Indeed, that's a reference to our trivia contest last week. Yeah. Make us laugh and just so you know, we weren't laughing about what other people might have been. We swear.

We have no idea. We're just dumb. We're generally unhip. We're out of it. Well, we're dumb too, but this was probably... Let's put that behind us. We swear. We have no idea. We're just dumb. We're generally on a hit. We're out of it. Well, we're dumb, too, but this was probably a hit. Let's put that behind us. All right. Let's move on to a nice technical objective question.

And we asked you, what is the escape velocity from the Earth's moon? So not to get out of the Earth-moon system, but to escape the gravitational pull of the moon. And how did we do, Matt? Wonderful answers. Several different choices of units, but most people the gravitational pull of the moon. And how'd we do, Matt? Wonderful answers. Several different choices of units, but most people settled on the metric. And I think that the best one that we got was probably from Jeff Williams, a listener in England. He sent this really cool table, which I will pass over to you, comparing the Earth and

the moon, all kinds of interesting factors. So thanks, Jeff. But I am sorry to say you didn't win the toss. You didn't win the random drawing. That poster, that Explorer's Guide to Mars poster, the last one for a little while, is going to go to Dean Koska, Dean Koska of Burnsville, Minnesota, who came in at 2.38 kilometers per second. A lot of people rounded to 2.4.

I think he got it, right? Yeah, that would be it. Some people pointed out that it depended on, slightly, on whether you were launching away from Earth or toward Earth, that there was a slight difference in the escape velocity for obvious reasons. Yeah, it is complicated because it is the Earth-Moon gravitational system, but this is the basic concept I was looking for, which is getting rid of, getting off the moon itself. And it's, you know, it's ballpark 2.4 kilometers per second. Yeah.

Difference was tiny. What do you got for us next week? Well, I've got a question about the Japanese asteroid rendezvous mission Hayabusa. And Hayabusa had a very successful mission encountering, learning about it. And then its goal was to return samples back to the Earth from the asteroid. And it may still be able to do that. They're heroically trying to save their spacecraft that had issues and get it back here. My question for you, where are the samples to come back to?

Whether they come back or not, where was the scheduled landing site? Tell us that. And it's got one of those really cool names I enjoy. So tell us the landing site. Go to planetary.org slash radio. Find out how to email us your answer of where Hayabusa samples would have or will come back on the Earth. And when do they need to get us that by?

You've got until Monday, April 24th at 2 p.m. Pacific time, Monday the 24th, to get that entry into us and this time you'll be winning a Planetary Radio t-shirt if you're the randomly selected correct answer a lot of people looking forward to a t-shirt since we haven't given one away so send us your size and also

if you can I'll ask you again send us where you listen to us because we're always curious we're done I think thanks for coming back in and doing what's up with us. Hey, my pleasure. Go out there, everybody. Look up in the night sky and think about whether ET is looking back at you. Thank you and good night. I sure hope

so. I sure hope so. And maybe we'll find out. Anyway, he's Bruce Betts, just back from one of those searches for ET and he's going to join us, as always, next week for another edition of What's Up. We're out of time. Thanks so much for joining our growing worldwide audience.

And here's a special tip of the space helmet to all of you listening to us on KCHO and KFPR, North State Public Radio in California. Why not drop us a line and let us know how you hear the show? Write to Planetary Radio at planetary.org. That's planetaryradio at planetary.org. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week, everyone. Thank you.