Planetary Radio: Space Exploration, Astronomy and Science - Saturn Update from Cassini Project Scientist Linda Spilker

Episode Date: April 1, 2013

We pay another visit to the queen of planets with Cassini Mission Project Scientist Linda Spilker. She always brings us fascinating news from Saturn, its moons and rings. Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Linda Spilker's News from Saturn, this week on Planetary Radio. Welcome to the travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. Our most frequent guest, Cassini Project scientist Linda Spilker, is back with another update from the only spacecraft we have at the queen of planets, beautiful Saturn with her rings and moons. She'll join us right after our usual conversations with Emily Lakdawalla and Bill Nye. Later, Bruce Betts with another chance to get the science guy's voice on your answering system. Emily, great to talk with you again. And it looks like you have finished summarizing your

great time at LPSC. Not quite, but hopefully by the time people are listening to this, I will have finished. Lots and lots of notes that she took at the Lunar and Planetary Science Conference this year. There is quite a collection. I've got to ask you, though, there is a geologist studying Mars named John Carter. Yeah, you know, I did a double take when I looked up. I was like, Jay Carter. Let me go find his first name. John Carter. You've got to be kidding me. I imagine that jokes have been made before, but the work that he was doing was pretty interesting. He was looking at this distribution of different kinds of clay minerals on Mars. Clay minerals come in different flavors with different cations, different, some of them have iron, some of them have magnesium, some of them have none of the above and just have aluminum.

What he was arguing was the idea that these clay minerals that we're seeing on Mars, they didn't form when the rocks themselves formed. They formed by alteration, and that the sequence that they formed in is actually very similar to what you find in certain kind of arid desert climates on Earth, where there's occasional rain, the rain wets the ground, and it leaches out some of the cations, some of those metal elements, and it takes them away from the uppermost surface, and that creates the sequence of minerals. And that's what he was arguing was occurring on Mars. Just one small example of the rich spectrum of stuff that Emily has posted at planetary.org.

Just look for her blog there. We got to mention this other, the most recent, as we speak, entry in the blog about Curiosity, which is getting ready for some dark time. But in the meantime, ChemCam did something absolutely amazing that people can see in your entry. Yeah, well, the ChemCam, of course, is the laser, the laser-equipped instrument. It shoots a laser at some target.

It vaporizes them and makes them shine in certain colors. They can determine the elemental abundances. But these guys are getting incredibly, I would say, even cocky with their aim. So they actually shot a series of six holes going up the interior of the visible part of the drill hole. Now, the drill hole is only 16 millimeters wide. I think their different shot points are only about two millimeters apart. And, of course, what they're trying to do is to get a profile from below the surface to the surface and see whether the elemental abundances change at all along that profile.

But it's really some pretty incredible shooting. But not to be outdone just after this, and it's not in this particular blog entry. I'll have to post it later. But the guys who control the scoop, I guess they're done sampling the powder that they got out of that drill hole. And what do they do with the tailings? Well, they dumped it right on top of the last couple of laser shots that the ChemCam team fired. So I think they're kind of out sharpshooting each other here. Sounds that way. By the way, ChemCam team, Captain Kirk is looking for some guys who

are handy with a phaser you can can apply in a couple hundred years. Emily, thanks so much. It is a great pleasure. That sequence of images from ChemCam is a sight to behold. It's there in the blog. It is a March 29 entry. Thanks a lot. Thank you, Matt. Emily Lakdawalla is a senior editor for the Planetary Society and our planetary evangelist.

You can learn much more from her. She's a contributing editor to Sky and Telescope magazine, and you can catch her on our weekly Google Plus Hangout. And in the last one of those, which is now available on demand, you can hear more about her experiences at the Lunar and Planetary Science Conference. Bill Nye is the CEO of the Planetary Society. In addition to being the science guy. He usually is here talking about the difficulties we're having trying to find money for the planetary science programs.

But now and then, one unadulterated piece of good news, I hope. There may be some people who have a problem with this. Did you see this lovely piece of this pellet of glowing orange plutonium-238 in space news. Yeah, yeah, yeah. Now, let me just talk again briefly about me. One of the very first things I did when I took the job as executive or director, now CEO of the Planetary Society, was sign a letter encouraging Congress to restore the uranium-238 uranium, plutonium-238 program. Plutonium-238 is not 239. It's not what you use as one fewer neutron. It's not what you

use for making weapons. It's what you use for powering spacecraft. And it's extraordinary stuff. It would not exist without our fundamental understanding of nuclear processes, without our fundamental understanding of how stars make energy and how we all got here. This is turning swords into plowshares. We're able to use this technology that was developed largely for weapons 60, 70 years ago into this material that can power spacecraft. Now, spacecraft like Curiosity are powered by these sort of solar cells that instead of responding to light, they respond to heat. So they convert the heat of plutonium, 238 decay into electricity. Well, now the next generation of these things is going to have a Stirling cycle

engine, which goes back to the 1800s. 1807 is when the Stirling brothers got a patent on this thing. It's a type of heat engine that instead of using steam, it uses another working fluid and makes electricity by running a generator around in a circle. Spinning, a spinning synchronous machine. Very cool. So it's an exciting time in space, Matt. But overall, no matter where you are in the world, we want to get the funding for this stuff steady so that everybody can just work on these things without fits and starts,

without stopping and starting again. That's Bill Nye, the science and planetary guy. He's CEO of the Planetary Society. Where should we go next? How about Saturn? It is such fun to visit with Linda Spilker at JPL. The Cassini Project scientist always brings us amazing news from the vast system of rings, moons, and swirling clouds offered up by Saturn.

This time I caught her right after her vacation. Thanks once again for coming by to give us this update on the Cassini mission. It's a pleasure to be here, Matt. We've got to start with a vacation that you just took. You're just back from Iceland, and I think the greatest thing about this is that now you've been able to enjoy the aurora up close and personal on two worlds.

Yes, that's right. Oh, we had a fantastic opportunity to see the aurora in Iceland. They were from the horizon to overhead, just beautiful, lasted about five hours. And also, there are these spectacular aurora at Saturn, and I'm sure they're even better than the aurora at Iceland, even more spectacular. And we have an auroral campaign coming up where we're going to be using Cassini

to look at the south pole of Saturn, which is now in darkness, and ground-based observatories and Hubble to look at the north pole of Saturn and to have a joint campaign while the sun is very active in this solar max period to see just what's going on with the Saturn aurora. So it should be great. So this is another example of how instruments that are way out there at Saturn can really work in coordination, very close collaboration, with other tools here on this planet. Absolutely. It's a very

powerful thing to do. The Saturn storm was another example of a joint campaign with Cassini and ground-based and Hubble, and that worked out very well also. All right, let's talk about some of the other recent results, but maybe first, how's the spacecraft doing? What's the health? The spacecraft health is excellent. We still have one instrument, the Cassini plasma spectrometer. It's been turned off. It had some problems, and we're in the process of trying to figure out what might have gone wrong, and if it makes sense to turn it back on or if we just leave it off. But we're still working that particular issue. But otherwise, the spacecraft is in great health. Isn't that, I mean, it must still amaze you as it does me, is in great health.

Isn't that, I mean, it must still amaze you as it does me, almost nine years at Saturn, not even including getting there. It's amazing. Yes, we're coming up in July on our nine-year anniversary, nine years to study Saturn and its moons, to take those moons, some of which were just pinpoints of light, and turn them into worlds that are recognizable now and very different from one another as well. Really diverse community of satellites there at Saturn.

I still have to kick myself now and then because, I mean, even getting ready to talk with you, it's like, oh my God, yeah, we humans, we have this machine out there at Saturn. It's mind-boggling. Yeah, very capable machine. A chance to really help us explore and learn more about the Saturn system and more about ourselves as well. All right, let's talk about those results. And I want to start with this press release, which came out just, I think, a couple of days before this conversation. And it has to do with the age of the moons and rings that Cassini has been studying for years. That's correct. Our visual and infrared mapping spectrometer has looked in detail at the moons and the rings.

And it looks like, especially for the moons that they formed at the time that Saturn did, they look ancient with just this coating, perhaps from the E ring, perhaps from different sources that color them. The rings themselves, it's now up in the air whether or not they formed at the time of Saturn. It might be younger, perhaps from the breakup of a moon or a comet. But there's more and more evidence that they could be old. And one of the things that will happen at the end of Cassini's mission in 2017 is we'll measure the mass of the rings. And if they're more massive than we think,

perhaps they could have formed at the same time as Saturn and have lasted until the present day. And why will that wait till the end of the mission? Is because that's when you'll put the spacecraft in more jeopardy? Yes, that's a very exciting time. We're actually going to take Cassini and hop in between into that narrow gap between the top of the atmosphere and the innermost ring. No spacecraft has flown there before, so it'll be a real nail-biter to see what's in there and a great chance to measure the gravity and magnetic field of Saturn and also get the mass of the rings, because now you have the mass of Saturn

with the spacecraft inside the rings themselves. Wow, where no spacecraft has gone before. That really is pretty exciting. Speaking of moons, you had a pretty interesting recent flyby of one, I think. On March 9th, we had a close flyby of Rhea. We came within 620 miles, which is very close. It's our last close flyby of this icy world. The main focus was to measure the gravity field of Rhea. Is Rhea differentiated or homogeneous? Does it have a rocky core, or is it pretty much the same throughout?

So we did those measurements. We also made measurements with the Cosmic Dust Analyzer. Micrometeoroids hit the surface of Rhea, sputter off other particles, and by measuring the debris scattered from Rhea, we can get an indication of how much of this rain of micrometeoroids that basically is causing some of the colors in the rings, we think as well, what that looks like. And finally, we got some great images. If you go to the Cassini website, you'll see some wonderful images of Rhea, including a very interesting tectonic fracture or graben across the surface. So some very new and close-up images of that world as well.

So as you see more and more of these moons, do you continue to confirm that they're really very individual? Yes, they have almost their own kinds of personalities, from young Enceladus that has the plumes of material coming out and it coats the surface of Enceladus making it bright white. That material goes out and coats the surfaces of the icy moons as well. Some of the moons look very old, heavily cratered like Mimas. Others have evidence of fractures and activity that happened after they formed. Then there's Hyperion that looks like this

kind of like spongy world, very interesting kind of surface. Ancient Diapodus with its equatorial ridge and cratered surface. So just a full range. And then one of my favorites, Tiny Methone, looks just like the Easter egg moon. It's smooth, coated, no craters on its surface at all. So a full spectrum of moons at Saturn. And then I think probably one of my favorites is Prometheus. Prometheus looks like it's an icy shard maybe left over from the breakup of a moon. And it has a skirt around its equator of ring particles that it's sort of built up. So it has kind of a reddish color, very similar to the ring color itself. And it's one of the shepherds of the F ring. I was going to say it's one of those shepherd rings that keeps the rings in shape. Right, right. That's helping and helping also

generate lots of interesting structure in the main rings as well. That's Linda Spilker, project scientist for the Cassini Solstice Mission. She tells us more when Planetary Radio continues. Cassini Solstice Mission. She tells us more when Planetary Radio continues. Hey, hey, Bill Nye here, CEO of the Planetary Society, speaking to you from PlanetFest 2012, the celebration of the Mars Science Laboratory rover Curiosity landing on the surface of Mars. This is taking us our next steps in following the water and the search for life, to understand those two deep questions where did we come from and are we alone this is the most exciting thing that people do and together we can advocate for planetary science and dare i say it change the worlds hi this is emily lakdawalla of the planetary

society we've spent the last year creating an informative exciting and beautiful new website your place in space is now open for business. You'll find a whole new look with lots of images, great stories, my popular blog, and new blogs from my colleagues and expert guests. And as the world becomes more social, we are too, giving you the opportunity to join in through Facebook, Google+, Twitter, and much more. It's all at planetary.org. I hope you'll check it out. Welcome back to Planetary Radio. I'm Matt Kaplan.

We're once again visiting Saturn with the best possible tour guide. Linda Spilker is project scientist for the Cassini mission that has been revealing that planet's secrets and beauty for nearly nine years. Of course, the planet itself must share Cassini's attention with the magnificent rings and moons that circle it. The largest of those moons is a dynamic world of its own, with an atmosphere that is thicker than ours and a complex system of rivers and lakes. We've got to get to big old Titan.

What's new there? Well, Titan, there's some interesting new results out that there might be ice actually floating on the surface of the lakes on Titan. That we look at radar data, we know the lakes are liquid methane and ethane. So in radar, they look very dark. We noticed that some of the lakes appeared a little bit brighter and had maybe what we thought was a grainy surface. And that grainy surface could be ice. It's cold enough to have methane ice freeze, and if you put a little bit of air in that ice, in the methane or ethane ice,

think of young sea ice on the earth with a little bit of air, then it could indeed float on the surface of these lakes. The temperatures drop, the ice might go to the surface, you might actually get a cycling of ice kind of up and down. And then now as we're going toward northern spring on Titan, that ice might melt and perhaps the character of those lakes will change and they'll become dark as that ice melts. So a very, very interesting result. Think of icebergs on the lakes of Titan. Boy, there is a travel poster I'd like to see up close and personal. We have so much to cover always when we talk to you, and of course we're rushing through these. But was there something that you wanted to say about,

I mean, I thought I read something in the weekly report that the mission team still puts out each week to tell us what has happened during the previous few days, that the Cosmic Dust Analyzer has been busy. What has that been up to? The Cosmic Dust Analyzer has been busy. What has that been up to? The Cosmic Dust Analyzer has been making profiles as we go through the equatorial plane of Saturn, in particular looking at the E-ring. The E-ring are particles that have come out from Enceladus' plumes and form this very extended ring. It goes out past the orbit of Titan, and it's vertically extended as well. And it's made of tiny, tiny ice particles, and they seem to be influenced by solar pressure and other changes. So we see now seasonal variations in the

E-ring. So the Cosmic Dust Analyzer can fly through the E-ring, make vertical measurements, and tell us more about this very interesting ring around Saturn. So even without flying through the rings themselves, we'll be able to tell quite a bit about their composition from this debris that is a little bit farther out? Right. Well, since the E ring is so broad, it spreads out from inside of Enceladus out to Titan. Very tenuous. You basically make cuts through the E ring whenever you go close to the equatorial plane. Yeah, I see. I see. So we really are going through one. You're flying through the cloud of the E ring. It's very diffuse.

The particles are very small. We've been doing this for lots and lots of orbits, and it's just a chance to make direct measurements of those particles. Let's talk about what's coming up. Your ninth anniversary is just a few months away as we speak, and there's still much more excitement to come, much of it during the summer. Right, right. In fact, back in November, we took one of these sets of images where Saturn covers

the sun, and we can then look very close to Saturn, very high, what we call solar phase angle, and we caught some images with Venus in them. Venus actually shining through the rings in November. In July, and in particular on July 19th, we're going to repeat that glorious mosaic, the iconic mosaic of Saturn, with all of the rings visible, Saturn covering the sun, and just the E ring, G ring, everything glowing brightly. We're going to redo that. And on July 19th, the Earth will once again be visible in those images. So in a sense, half the people of the Earth will be in those pictures taken by Cassini in July. So that'll be a very exciting time. And of course, that earlier image, so iconic. And I just showed you my new business card,

because the science guy let us put images on the back of our business cards, and I have that image right there. Yeah. And it is just, I already used the term mind-boggling, but it certainly is that. Do you want to talk about any of the other science that we should be looking forward to as Cassini moves toward 2017 and its eventual demise as it goes right into the planet? Right. Well, in the next few years, we'll be looking for seasonal changes, both on Saturn itself and on Titan. As the sun continues to rise in the northern hemisphere,

we'll be looking at those lakes on Titan. Do they start to evaporate? Do we see changes as the ice might melt? The sun will be going higher and higher on the rings. It's now in the northern hemisphere, the northern side of the rings. And what will we see that might be different in the rings? And just have a longer time to study these very interesting objects called propellers. There are larger-sized ring particles that try and open up gaps in the rings.

They're not quite big enough to open up a gap that goes all the way around. So they open up tiny gaps that look like an airplane propeller. And so we've been tracking the orbits of these objects and we find that these propeller objects' orbits sometimes change abruptly. They appear to move very quickly around in the rings and somehow they're interacting with the dusty disk of Saturn's ring particles. And maybe by understanding how this works, we can understand perhaps how planets form. If you have a sort of a mini solar system analogy of these shards being like tiny planets, and how do they grow and form in a dusty disk or a debris disk, such as the early solar system would have been composed of. Fascinating. Anyone who follows this show

or is aware of what's going on with the federal government and NASA funding knows that planetary science funding for missions like Cassini is somewhat in jeopardy as the federal government faces lots of financial challenges. I got to think that maybe Cassini gets caught up in that a little bit too. I hope not too seriously. Yes, with the planetary missions, there is really a problem with the budget, especially as we go further out in time. We just have a lot of missions to fund, a lot of new missions to get started. And so that puts pressure on how long do you keep other missions going. So Cassini is just one of those missions there trying to struggle to keep funded through its end of mission in 2017.

I hear we're going to see something from you in the Planetary Report, our magazine that goes to Planetary Society members. Yes, I'm working on an article to talk about what we've learned about Saturn's rings in particular since the Voyager era. I was actually fortunate enough to start my career at JPL working on Voyager. One of the very first things I got to do was to go to see Voyager launch and start on its journey to the planets. And it was just so exciting to see it fly by Saturn. And so I'm going to compare how much we've learned since those first Voyager flybys. Our view of the rings, a simple view of individual particles kind of floating in a cloud around Saturn, has really changed and evolved.

The rings are now clumped up in the A and the B rings with spaces in between the clumps. And so very different kinds of rings than what Voyager first saw. I look forward to reading that article. And I look forward to talking with you again. Do you think maybe we could do this again in July or soon after, to talking with you again. Do you think maybe we could do this again in July or soon after when you have those new mosaics looking back at our own planet, seen through the frame captured for us by Cassini at Saturn? Sure, that would be a great time for an update. All right, Linda. And we got to start talking about the 10th anniversary, too, in 2014. Yep, sure do. Thank you so much. It is

always a pleasure. Thanks, Matt. Linda Spilker is the project scientist for the Cassini mission. She's done that for a number of years and has been with this mission. We were talking about this before we started recording, probably since before some of the young scientists who are now using data from Cassini as part of expanding the realm of human knowledge. We're going to try and expand that a little bit further when we talk to Bruce Betts for this week's edition of What's Up in just a few moments. Bruce Betts is here. It's time for What's Up on Planetary Radio.

We're going to hear about the night sky and some other stuff. How are you? I'm doing well. How are you doing, Matt? Very well, very well. It's been a very nice holiday weekend, just finishing the Easter weekend here. Good night for stargazing? Well, it is if it's not cloudy.

Yeah, we've got Jupiter still fabulous in the evening sky. Please don't forget to pull out those binoculars or small telescope if you have them and stare at Jupiter and try to pick out the little moons, which are actually very big moons, but they look like tiny stars in a line. Saturn, like you've just been talking about, you can see it yourself

coming up in the 10 o'clock, 11 o'clock-ish p.m. type time frame over in the east, and then getting higher up and yellowish, and with a small telescope you can pick out some rings. Even though you won't have the view the Cassini has, there is nothing like looking at those photons

coming through a telescope right into your own eye. Really isn't, especially when you know they started a billion miles away. Right. That's what I find to be the profound part about seeing the rings particularly. We move on to this week in space history. 2001, Mars Odyssey was launched. Mars Odyssey that is still doing great stuff random space fact that's it okay that's all right you have a perfect right after 10 years trying something new yeah i know

it's it's kind of that you know news bulletin from the in the 40s it it's hard to find a new style after doing it well over 500 times. Now on Random Space Fact we tell you about the Saturn hexagon but first so Saturn has this massive north polar hexagonal storm system thing

that's actually hexagon shaped and a hexagon that is bigger than Earth in diameter and really weird looking that you got a hexagon that is bigger than earth in diameter and really weird looking that you got a hexagon there well turns out oxford scientists have played around in the lab and they've they've created hexagons in water tanks by spinning rotating discs at different speeds under the the water they can actually generate various regular polygons, strangely, that result out of the instabilities that are created by the different rotation rates. And Emily actually wrote a lovely blog about this not too long ago that you can always find at planetary.org and search Saturn hexagon.

So here is some basic bit of physics, fluid dynamics, that was discovered because it was first seen a billion miles away on Saturn. Well, at least, yeah, at least the confirmation part. Now, they're still debating, is that really the same process going on at Saturn? But the mere fact that you can generate a hexagon in liquids in the lab, to me, is pretty amazing. Just like seeing one on a planet. It's pretty amazing that it's not been placed there in Photoshop. I couldn't agree more. On to the contest.

All right. We asked you about the prime meridian of planets. So what surface feature on Venus, in this case, is taken as defining the prime meridian? In other words, longitude zero degrees obviously it's a somewhat arbitrary definition but but what is it matt how do we do kind of holiday light i think but but still a good number making his way through the crowd thanks to random.org was steve bruski yes steve bruski of walkerton indiana who said that for us Earthlings, the central peak in the crater Ariadne serves as the marker for the prime meridian of the planet Venus. He got this from the USGS Astrogeology website.

Always an excellent website. Yeah, he says he just wanted to thank us. He says, nice work. Love the podcast and the blogs. Steve, you've won, and we're going to get you Bill Nye's voice on your answering system, so congratulations. A couple of other interesting ones, just to go through very quickly here. Derek Calderon in San Francisco, he mentioned that until the Venera missions in the 1980s, the original Prime Meridian was said to pass through just a radar-bright spot that was called Eve.

And Kurt Lewis said exactly the same thing, but then he added that those Venusian clouds sure make this a lot harder. If only we could see the surface directly, we could just look for the lines that are printed there. Well, that's true. And if you look at the right wavelengths, it turns out you can see them. Oh, is that right? Gosh, that makes it so much simpler.

Thank you, whoever drew those. It's just all drawn in. It's very nice. It's very convenient. All right. We move on, and it's been a while, so I think it's time to once again play Where in the Solar System?

Oh, boy. See? See, I tried to make up for it. It was a balancing act with random space facts. I see. Where in the solar system is Ontario Locus? Ontario Locus, L-A-C-U-S. Tell me the body where you will find Ontario Locus in our solar system, not on Earth.

Go to planetary.org slash radio contest and fill out the form. Enter our contest. Take a chance at winning. What are they winning, Matt? It's going to be Bill Nye's voice once again. Bill Nye's voice once again. Boy, he must be getting tired. No, he loves this.

He really enjoys doing this. It's amazing how much he enjoys it. We're only going to cut him off when we finally have the new Planetary Radio t-shirt, which is in the works. So stay tuned, as they say on the radio. Say goodnight, Bruce. Goodnight, Bruce. All right, everybody, go out there, look up in the night sky, and think about chewy vitamins.

Thank you, and goodnight. Two on this. The deadline for the contest is going to be Monday, April 8th, at 2 p.m. Pacific time. He's Bruce Betts, the Director of Projects for the Planetary Society, and he will join us again next week, as he has every week, for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and made possible by a grant from the Kenneth T. and Eileen L. Norris Foundation, and by the far-out members of the

Planetary Society. Clear skies.