 To people online, to our audience here, welcome to Post Cards from Saturn. I'm very pleased to have Linda Spilker today. My name is Brian Schmidt. I'm the Vice Chancellor and President of the Australian National University, but I am a cosmologist by training, helping be part of a team that discovered that the expansion rate of the universe was accelerating. So today we have the opportunity to see some of the most fantastic images ever taken in our solar system. This is the culmination of a series of programs that have gone out and put man-made machines out into the solar system. When I was a young kid, I got to see pioneer and then voyager go through and show us pictures of first Saturn, sorry, first Jupiter, Saturn, and then Uranus and Neptune. And these are the things that got me interested in becoming an astronomer. Linda has been there almost from the beginning, starting off in voyager. She did her degree at UCLA and straight out of getting her degree went to Caltech JPL. She has, as a physicist, someone who likes to study the dynamics of rings and if you're going to do that, there's no place better than Caltech JPL. So Linda, over to you. Give us some Post Cards from Saturn. Thank you very much, Brian, for that great introduction. Well, for 30 years, I've had the privilege to work on one of the grandest missions in the solar system, the Cassini mission to Saturn. And those 30 years of my life have intertwined with Cassini. And in fact, it's been just a remarkable journey and discovery. Cassini discovered two liquid oceans on the moons of Saturn. And those oceans might have life that exists there today. As I said, I've been with Cassini from the very beginning. And if you look at the picture in back of me, there's the Cassini spacecraft against Saturn and its rings. Now, I'm going to tell you about Cassini in the context of my own life story. And so during the 30 years I've worked on Cassini, my husband Tom and I race our two daughters. There's Jennifer in the middle and Jessica over on the left. And so that's been part of my life as well. Well, here's a very enthusiastic Cassini family. And it's a family, an international family of scientists and engineers from around the world, about 600 of them planning the science for Cassini and sharing in Cassini's discoveries. And one of the surprises we had is we also got to answer some of the questions, basic questions from humanity. Are we alone? Could there be life in our own solar system? And can we try and find it? And that's been part of Cassini's mission. Here are the eight planets in our solar system, starting out from the sun, the four rocky planets. Saturn is the sixth planet out from the sun and has magnificent rings and 62 moons. Now, Saturn is a gas giant. The atmosphere is mostly hydrogen and helium. And all we see are the cloud tops of Saturn. Now, to give you an idea of just how big Saturn is, here's the Earth and the moon to scale and the distance between them. And Saturn and its rings would just fit in between the Earth and the moon. Can you imagine a night sky with Saturn and the rings visible in that sky? Well, the idea for Cassini first came after the two Voyager flybys in the early 1980s. Voyager opened our eyes to incredible questions about Saturn and its moons and rings. And so he started to plan a mission to go back. And about the time the idea for Cassini was conceived, I had my first daughter, Jennifer. Three years later, I had Jessica. And it was during that time that I went back to school and got my PhD studying the complex interactions of ring particles at Saturn using Voyager data, part of the project I had worked on, as well. Well, in 1990, NASA selected instruments for the Cassini spacecraft shown over on the left, the Huygens probe in the center there. And if you look very carefully on your right, you can see the Huygens probe actually attached to the Cassini spacecraft. And during the seven years that it took to build Cassini, there were growing pains for Cassini, just as you'd have growing pains in a family. And what I really enjoyed is the opportunity to take my daughters to see Cassini as it was put together like a giant jigsaw puzzle. And here's my daughter, Jessica, and I were in the clean room at JPL standing in front of the Cassini spacecraft. We were also there for the launch as a family. Cassini launched in 1997. We stood there as the roar of the rockets could literally be felt in your bones, watching as the rocket lifted off the launch pad and started into space. Now, some people might say one of the greatest accomplishments of that day was successfully launching Cassini. But let me tell you, getting two teenage daughters up before dawn to go watch the launch was a great achievement in and of itself. Well, in the 13 years we were at Saturn, we got to watch the seasons change. And the seasons changed in my life as well. We arrived at Saturn in the summer. You could see the ring, where it was winter in the northern hemisphere. You could see the ring shadow in the north. At Equinox, you could just barely see the ring shadow at the equator. And in the end of the mission, it was winter in the southern hemisphere. Now, you can use the ring shadow, like a giant sundial at Saturn. By looking at Saturn, seeing the ring shadow, you know the seasons at Saturn. It takes Saturn 30 years to circle the sun a single time. So a season at Saturn is 7.5 years long. And so Cassini was there really only for just two seasons. And during those 13 years at Saturn, my daughters, Jennifer and Jessica, graduated from college with degrees in engineering. And they both got jobs, and they both got married. Here's a picture of the rings, one of my favorite pictures, Saturn's rings. Saturn is all the way over on the edge off the screen there. Let me take you on a walk through the rings. First of all, you have the A ring here on this side. Then the very bright B ring in the center. Saturn's rings range in size from tiny marbles to giant mountains. In between is the Cassini division, named after the astronomer who discovered this gap in Saturn's rings, and for which the Cassini mission is named as well. As you continue across, the darker grayish ring is the C ring. And finally, the very, very faint D ring, all the way over on the edge there. And now if we zoom in on this tiny dark line here, that's a gap in Saturn's ring. And if we zoom in, that gap is created by the gravity of a tiny moon, Daphnis. The Keeler gap is held open by the gravity of Daphnis. And you can see the Daphnis has created a beautiful wave of ring particles, much like the waves on a beach. Now you see other areas of brightness here. Let's zoom in on one of those with Cassini's cameras and see what those might be. Turns out those are giant waves propagating hundreds of kilometers through the rings. There's a gravitational interaction between a moon outside the rings and this place in the ring. And so the ring particles transmit like a wave. It's like the ringing of a bell as this structure propagates through the rings. And this was part of what I studied for my thesis. So I happen to think these are very, very beautiful pictures of Saturn and its rings. Now that moon in front of Saturn, that Saturn's moon Titan, Titan is a large moon. It's larger than the planet Mercury. Had Titan formed anywhere else in the solar system, it would have been a planet. Titan has a thick, nitrogen-rich atmosphere, much like the Earth's atmosphere and also has methane. And methane is unique. Methane plays the role on Titan that water plays on the Earth. Methane can form clouds, methane can rain, methane carves river channels in the icy surface of Titan and fills the lakes and seas at the North Pole. And we wondered, could there be a very unique and different kind of life that could use liquid methane instead of liquid water there in the lakes on Titan? Now Titan also has a global liquid water ocean underneath its icy crust and perhaps life could exist there as well. Now to pierce through that haze that's a photochemical smog that methane gets broken apart by sunlight and forms a smog just like you'd find on a bad day in L.A. or Beijing. So we carried the Huygens probe provided by the European Space Agency to parachute through the atmosphere and land on the surface. And here's a movie from the Huygens probe, two and a half hour journey under a parachute to the surface of Titan. Cassini flew overhead as Huygens transmitted the data to Cassini. Huygens measured the composition of the atmosphere, the temperature, pressure and also took these wonderful images. We saw river channels. We saw mountains. We were seeing the surface of Titan for the very first time. And as we landed, we noticed rounded icy pebbles. Water flowing in rivers and streams on Earth, round the rocks on Earth and we knew here liquid had flowed on Titan. Huygens had landed in a dry riverbed and what a great introduction. We had radar also to pierce through the haze and make maps of the surface of this very interesting moon. This is of you another moon, Enceladus. Enceladus is only 500 kilometers across, about one tenth the size of Titan. But Enceladus was unusual because it was so bright and white and fresh and young looking and you can see places on Enceladus have no craters. What we discovered is that there were four long fractures. This is the south pole of Enceladus and coming out of those fractures were water vapor and water ice particles shooting out into space, geysers coming out of the south pole of Enceladus. We were so surprised. Many of the largest particles fall back to the surface just like the snow that we experienced earlier in the week here in Davos and that covers up and fills in the craters and gives Enceladus that bright, youthful appearance. Here's another view of the south pole. This is time backlit by the sun and you can see 30 individual jets going up into space. Cassini flew through those jets seven times, tasting and sampling the composition of this material. And we found that the liquid water ocean underneath Enceladus' icy crust was salty just like the Earth's ocean. It was filled with hydrocarbons. We also saw evidence of hydrothermal vents on the seafloor and so we wondered could this ocean on this tiny moon perhaps be a habitat for life. Now Cassini, we had no idea when we launched Cassini that we might find worlds that might contain life. So we didn't carry any instruments to look. So we'll take a mission to go back to Enceladus to answer that question. I'd like to be part of that mission if they go back. Now over 300 years ago a sculptor actually put together a different Enceladus and here at Enceladus shooting water upward. And here's a view, this is a picture that I took of a fountain in the gardens of Versailles and so you can see Enceladus out of his mouth is coming this jet of water going over 25 meters into the air. And how surprised the sculptor would be to realize that the real Enceladus is doing exactly that. This is one of my very favorite pictures. You can see tiny Enceladus here in the E-ring, the very tiniest particles actually go on and create this beautiful ring around Saturn. You can see Saturn with its halo of rings. Now it's not easy to get a picture like this. You have to have a solar eclipse. And in this case Saturn is covering up the sun so we can get this glorious view of Saturn and its rings. And there's actually something else in this picture. It turns out if you look carefully this tiny dot right here is the Earth and the Moon. So we're getting a picture of our own planet from 1.5 billion kilometers away. And this picture just makes me appreciate how precious this world is, the only world we know of that has life. And we now think that perhaps two other worlds, Enceladus and Titan, might be potential habitats for life. And this Cassini was running out of fuel that told us that we had to be careful once Cassini was out of fuel, not to allow her to run into either Enceladus or Titan. So our engineers found a way to go in between the gap between the rings and the planet. Twenty-two orbits we labeled the grand finale to get back incredible science and on the final orbit to end the mission. Now imagine yourself holding on tight to Cassini and I'm going to show you a little movie of one of those orbits. So here you go over the North Pole of Saturn, 120,000 kilometers per hour diving between the rings and the planet. And imagine the incredible detail and the knowledge we got about Saturn and its rings. Diving between 22 times until finally on the final orbit, the Cassini mission ends. And on September 15th of last year, that was Cassini's last day. We were all gathered at JPL and I was there with my family again. And this is Jennifer and Jessica. And this time my granddaughter Audrey was there as we watched the end of Cassini. And it was really a very bittersweet moment because we had such triumphs and such success with Cassini. And yet it was very hard to say goodbye to such a dear friend. And tears flowed and we hugged each other and went on and thought about what were the next possibilities. Well, I'd like to show you a video and this is about the wonders of Saturn. It's the pictures taken by Cassini set to music. Think of it as the picture postcards from Cassini to the people of Earth. Now to truly reveal the wonder of Saturn, we had to go there. And I personally would like to go back. You see missions like Cassini help us bring hope to a fractured world as together we experience the beauty and the grandeur beyond Earth. Thank you. Thank you Linda. Truly inspiring stuff for those of you, the audience of those in your online. If you'd like to ask a question, please go to weft.ch slash beta zone. You can enter your questions there. If you're in the room here, you can raise your hand. We will do it old fashioned ways. But you can also go through and upvote things. If you think someone else's question is one that you would like answered. So I'm going to start with the first question and then we'll go out and we'll get going. So Linda, seven years from the time you launched Cassini until it actually got to Saturn. What did you do in those seven years? Do people go out and become baristas? Do other PhDs? What happens? Well, it turns out we had a lot of planning to do. We hadn't written a lot of the software we needed to actually make the intricate measurements that we needed to do with Saturn. So we planned the software and the scientists decided let's plan the first four years of the prime mission and have that all done. So when we get there, then we can analyze the data and decide what we want to do next. And actually those seven years flew by. So we had a lot of hard work to do that we had waited until after launch to accomplish. Very good. I will take a question inside. You, sir. My question is a lot of the space exploration depends on NASA, which is then again funded by the government. And correct me if I'm wrong. Under the Bush administration, there was funding to the NASA, but the Obama administration actually virtually cut it off. Do you see that space exploration nowadays is limited by that? And then where do you see the private sector actually coming in and really taking off space exploration? Well, it turns out the current administration is very much in favor of NASA and exploration. And so that is continuing. I'm really encouraged by the private sector. I think that'll bring the cost down and allow more missions like this to happen. A mission like Cassini is really a very small part of the NASA overall budget because there's a large portion that goes to manned missions and other missions as well. But I think we have a very healthy and exciting program and in part that supported by the people that are very interested. We're also partnering with the European Space Agency, the Japanese Space Agency, because together we can launch more capable instruments and payloads. And hey, it's a lot of fun to work on an international mission as well. Very good. So we're going to take one from online. What was the biggest surprise for you of the Cassini mission? I think without a doubt the biggest surprise was finding active geysers on Enceladus. Everything we thought we knew about how moons would work, this tiny moon should have been frozen solid long ago. And we knew it got a little bit of energy from sort of a resonance with one of the other moons squeezing it, but we didn't think the squeezing was enough. So we're having to totally redo our paradigm, our ideas about these ocean worlds that we're finding within our own solar system. All right, we'll take another question in the room over to you, sir. Amazing images. So my question is, you said that Saturn tilts to generate the seasons like, right? So I would like to know if the rings tilt along with the planet or if they are stationary. Yes, the Saturn is tilted over. And so, yes, the rings do tilt with Saturn. So they open up more toward the sun. At equinox from the earth, the rings are just a thin line. And so it was nice to have Cassini there to look at the rings, look down at them during equinox. And we could actually see giant shadows from the largest objects in the rings. So, yeah, they tilt too. All right, again from online, what's the next big project? You get to design it. What do you want to do? What do you, what's your next big project if you get to choose it? If I could choose any project, I would want to go back to Saturn and finish up on what we've been doing with Enceladus, carry the instruments that perhaps could look for life, amino acids, fatty acids, and even bring a sample from the geysers back to the earth so we could use all the technology here to answer that question. Is there life in Enceladus' ocean? And if the answer is no, that's astonishing because the conditions appear right. Maybe it's hard to get life started. If the answer is yes, is that life like the earth? And that would be amazing. It's life, very unlike the life we have here. That would be amazing. So whatever the answer to that question will be amazed. Very good. Another question inside the room. You, sir, just wait for the microphone, please. Do I understand that the satellite was, or the Cassini was destroyed at the end of the mission? The question was, was Cassini destroyed at the end of the mission? And yes, we actually went into the atmosphere. And so why was that chosen as opposed to letting it continue like the voyagers or the pioneers? Well, we didn't, the question was, why didn't we continue like the voyagers or pioneers? We were trapped in Saturn's gravity well, and we decided to use all of our fuel to do exploration. And so we didn't have enough by the time we got to the end of the mission to break free. We could have crashed into another moon, but actually going in between Saturn and the rings gave scientists an incredibly rich new data set by going back close to the planet. Another question. How do you, how do you see work like this, you know, influencing how young people think about science, maybe young girls, and maybe you want to use your own life experience as an example? Well, I think missions like Cassini and NASA's exploration encourages young people to go into careers in science and technology and engineering. I know in the case of my own two daughters, they went into engineering and also in going out and talking to young girls, especially that middle-aged, you know, group to encourage them to keep taking math and science. And they're excited about what the potentials are to explore space. So I think it's a very good way. For me personally, I think watching, you know, humans walk on the moon, that just drew me in. And I know I really wanted to be a part of it. I had a telescope. I was looking at the planets. I knew I wanted to do something with space. Very good. So Frank asked, based on what you've learned here, how do you think differently about, for example, how life on Earth is compared to before this mission, maybe even think more broadly, life in the universe? I think before Cassini, you know, we were looking for planets around other stars. And in particular for those planets in the zone, like the Earth would be where you could have liquid water on the surface. And the big paradigm change with Cassini is that now, perhaps you should have a broader view. You could find these moons, these ocean worlds, where life might exist. So it's expanded our reach and our ideas of where life might exist. Very good. In the room, to you, find the microphone. Yes, coming back. I was just wondering when you mentioned about things that you didn't expect that were found, were there certain expectations or things that you thought might be there that weren't confirmed? A good example of something we expected and didn't find is we thought we knew the length of Saturn's day, that there was this radio signal that came out and measured by Voyager and we thought we had the length of the day. With Cassini, we got there and that periodic radio signal had changed. And we knew that Saturn couldn't speed up or slow down by that much. And so we're now back to thinking we don't really know what's the interior rotation for Saturn, because all you see are the cloud tops and different places rotate at different speeds. So here's the case, we had an expectation and now we've had to say, OK, now we have an open question instead. So there's a question about Europa, which is not around Saturn, but has another moon that seems to have possibly a liquid ocean. What do you think you might find around Europa? And how would you do a mission? Because it's got a lot of ice around it. Right. Well, there's a mission in the works from NASA called Europa Clipper. And Europa Clipper's goal is to go and try and characterize the ocean that we know is underneath Europa's icy crust. But there's a lot of radiation at Jupiter. So we have a mission. We have flybys rather than orbiting Europa. We have flybys to try and understand it. And we want to measure the thickness of that icy crust because a mission to go back or to land would want to know where are the best places to land. Are there geysers on Europa? Europa is just so much bigger that maybe they're little tiny geysers and they're harder to see. So we're going to look for geysers, look for places to land, figure out how thick the ice crust is and get ready for future missions. So someone online would like us to think really big and wants us to think about the Fermi, what's your take on the Fermi Paradox? For those who do not know what the Fermi Paradox is, let me briefly describe it. If you have a civilization that is advanced enough to travel between stars, that civilization would have had enough time to populate every star in the galaxy. And so the take message might be no civilization has ever done that. And maybe we should just quit even thinking about it. Your take. Yeah, very interesting question. I guess I personally think that given so many stars that there's a possibility of life and why we haven't been contacted yet, that's really a very intriguing question. So I guess we're just going to have to keep trying as always my bit. And you know what, it's always okay to be the first has been my experience. All right. Any other questions in the audience? Yes. Wait for the microphone, please. I think or we just left the microphone. Sorry. The technology has abandoned us. Right here. Just a second. Great presentation, really. What I would like to ask that you said you want to go back to Saturn. And what is the time frame for a project like that? I mean, from the time you start thinking about the new mission and to the time when you launch and then finish the project. Well, if we use Cassini as an example, we started thinking about a mission like Cassini in the early 1980s. 1990, we had funding and everything in place for the instruments and then seven more years to build Cassini. So it was almost two decades, a decade and a half from the idea to getting to Saturn. It's just that the outer planets are not easy to get to. And so it's a long journey. So Alex asks, should we be sending messages out or just listening? Oh, I think we're sending messages out whether we want to or not. All of our TV and radio signals are going out into space. And who knows who might be seeing reruns of I Love Lucy, you know, even now. So we are sending signals out into space. And in fact, we have two emissaries, the two Voyager spacecraft are leaving the solar system. They each carry a gold record. And on that record are the sights and sounds of Earth and even a map for how to find us. So if an alien civilization finds Voyager, they'll be able to get back to us. Yeah, and it's worthwhile knowing that if we, a sister civilization, existed, for example, on Proxima Centauri, where there is planet where that's possible, we could already detect our own airport radar right now. So the universe is closing in on us with our technology. All right, I think we will finish up with the question is, so if we're going to launch, I guess, how long are we talking about till we get these next missions to Saturn? I mean, it's there's a long time. Is there any way to speed this up? When can we expect the next post cards, as Carlos wants to know from Saturn? Well, we don't have any mission planned to go back to Saturn at this point in time. I'm really hopeful that with private industry and lowering the cost that perhaps there might be something, if not within NASA, within the private sector, we can go back and plan a mission and use the launch capabilities and the International Cooperation to go back a little bit sooner, but probably a decade, I'd say, at least. OK, very good. A final question for the audience. Yes. And again, wait for the microphone, please. More a comment than a question. NASA and the National Academy of Sciences in the United States has placed high priority on an orbiter for one of the gas, one of the ice giant planets, either Uranus or Neptune. Right now it looks like it's favoring Uranus, but we're looking at maybe a project start on that within the next decade. And how long does it take? I should say Tom is also from JPL, or at least used to be, right? How long does it take to get out there, to Uranus or Neptune? If you really put the pedal to the metal and you have a way that you can stop once you get there, even though you've had your pedal to the metal, you can get there in about 10 years. All right. Well, OK, I'm 50, so I have a chance still. Sounds great. All right. So time for us to wind up. I guess my take home message is these are amazing, beautiful worlds. One of the things that maybe not obvious is that you're also getting deep physical understanding the way that nature works, the way these very complex storms happen, the possibilities of life. These are big questions and they're big questions that unite humanity. And I think that's one of the things here in Davos is if you want to unite a fractured world, you have to have common purposes. And if we're going to make it through the coming century, we need to have common purposes through these international missions where we go out and be human rather than fight about being human. Thank you very much.