 Okay, well welcome again to the November webinar for the NASA Night Sky Network. Every month we highlight an activity related to the webinar topic. This month we're looking at one of the icy moons of Jupiter, Europa. There's a really cool activity called the ice balloons, which people of all ages find engaged. Here's Vivian with the details. Hello, hello. Hi, everybody. I'm going to bring you this activity and show you a little bit about how we run this. If you look on the website where this video will be posted, you'll see the write-up. It's from the NICE network, or you can look up the Exploratorium. If you look up ice balloons at the Exploratorium, it's a science nugget. So these are really fun. It's easy to make. Let's see. Are you going to show? Yeah. Let's see if we show. All right. So this is the facilitator guide. It tells you how to make these. You just fill a balloon with water. You can add sprinkles. You can add anything you might want, some confetti or glitter to that, and then freeze it. It takes about two days to freeze something this size. So after you freeze it, you just cut it open, and it's this beautiful ice ball. Well, you don't cut the ice off. Well, you don't cut. You cut the balloon open. Thank you. Cut the balloon off of it, and you end up with this ice ball. Here's some tips about how to do so, so it kind of stays round. This is what we call an inquiry activity, and it's a really fun way to explore our natural or material world. It allows for your visitors to make discoveries on their own and kind of search for understanding. It's not one of our more traditional activities, but it's a really fun way to allow natural exploration to happen. So what you do is you start off with just your ice orb and some sort of tray that will catch the water as it comes off. You can give a magnifying glass and also a flashlight. Okay. Let's see what this looks like. A little hard to tell, but oh, and the background's pretty awesome. But check out what you can see here. I don't know if you guys can see all of this detail in here, but if you just give your visitors a little bit of time to explore and notice what they can see inside there. Tell them to come up with some questions and instead of just answering all of their questions like we like to do, like I know I like to do, instead maybe ask them how do they think they could find that out when they ask a question or say that's really interesting. What do you think? So they might notice that there are lines in here or bubbles and kind of talk about how ice forms, some of ice's amazing properties. This does relate to our topic tonight. This relates to the search for life on watery worlds or ice worlds and there are a lot of questions that come up with that. I will let you look at the facilitator guide online to kind of give you an idea. I'm going to get the lights back up if you would and I'll show you some fun stuff you can do with this. So once they're done exploring it with just the magnifying glass and flashlight, you can also give them some really fun things such as our very favorite, like you can tell I've been using it all day because my hands are covered, either in some liquid watercolor or food coloring is one of my favorites and you can see that shirt. You can see some of these patterns that it makes. It might look something like what we have here. They've got images of Europa. They've got images of some other icy worlds that you can print out. This of course is from the Galileo mission, but it tells you a little bit about the huge ancient impacts on Europa. We'll see some things like this and you start to investigate some of what is going on inside. So this gives us another way to kind of make a false color on our planet here, our ice planet. Here it's not of course an exact analogy to an icy planet, but it does give us some way to talk about how we use different tools to discover what these worlds are like. So it's a, oh, whoa. Oh that's different. That's because the greens not. Okay. Come back, come back. It was good a minute ago. All right. Oh magic. Okay. It's because I used green. That's about that part. Anyway, they look amazing and there are just a lot of fun to play with. So I really encourage you. It's filled with stars, Vivian. All of these planets are filled with stars. We forgot to tell you. It's really fun and a great way to just do some investigation. You'll love the questions that come up from this and I encourage you to just give it a try out. You should try it out at your own house. If nothing else. It's really a fun activity. It's really fun to spend here in the office. Probably a half an hour. Everybody huddled around in the dark. Exploring what this looks like. So I encourage you to use this and enjoy the questions that come up. All right. Thank you, Vivian. And now for our featured program. Dr. Robert Papalardo is the project scientist for NASA's Europe, a clipper mission at the jet proportion laboratory, California Institute of Technology. He also served as the project scientist for the Cassini equinox mission at Saturn. For which he received NASA's exceptional service now. He served as a member of the National Research Council's space studies board and as a co-chair of its committee on the origins and evolution of life. He received a BA in geological sciences from Cornell University in 1986 and a PhD in geology from Arizona State in 1994. His research focuses on processes that have shaped the icy satellites of the outer solar system, especially Europa and the role of its probable subsurface ocean. Please welcome Robert Papalardo. Just one second. It looks like you're muted. Two shakes. Okay. I think you're good to go. All right. Good. Can you hear me out there now? Yeah. Welcome. Great. Thank you, Brian. Vivian. Let me share the screen here. Hopefully you're seeing that. This is an experimental format for me. So. See how. That goes. I'm going to attempt to monitor the chat as we talk and multi-task best we can from here in my office at JPL. So that I get a feel for what you're thinking out there. I'm very happy to be talking with you about Europa, one of the most fascinating objects in the solar system. Because we think at Europa, there is probably a subsurface ocean under its ice, probably about 20 kilometers beneath the surface, enveloping the whole globe of Europa. And I'm the project scientist for the Europa clipper mission. I'll see if the spacecraft model shows up behind me. I'm not sure if it does, but we'll talk a little bit about here. Got the small one. We'll talk a little bit about the Europa clipper mission, which is in development and what it can do to explore Europa and shed light on its ocean and what makes it tick. So we know Europa as one of the four Galilean satellites spotted by Galileo in January 1610. And which at the time really changed our sense of place in the universe. Galileo came to understand that Jupiter was a center of motion around which the moons of Jupiter orbit. And so why can't the Sun be a center of motion and Earth be a center of motion around which our moon orbits. And that really brought about the Copernican Revolution. Today we know of the four Galilean satellites named for Galileo, Io, Europa, Ganymede, and Clisto as places that are quite distinct with their own geological personalities. Io, the most mechanically active body in the solar system. Of course, Ganymede and Clisto are about half ice, half rock, Io is essentially all rock. And Europa actually is a rocky body with a skin of H2O, kind of a hybrid in between. And is really an incredible object worthy of a flagship mission to understand what makes it tick. And not only is there an ocean or to confirm an ocean, but to understand is that ocean, could that ocean be habitable for microbial life? See? Oh, there we go. There's just a little animation, a little Galileo spacecraft down here, which orbited Jupiter from 95 to 2003. And so the images you'll see are essentially all from, well, mostly from the Galileo spacecraft during that time, which made about a dozen flybys of Europa. So here are some examples of Europa's surface close up, seeing the variety of landforms, and we'll talk in more detail about each of these. The bright planes that you see near the poles, and they're elsewhere as well, are made up of crisscrossing ridges and grooves. With the sun high in the sky, we see the albedo, the brightness differences show up very well. And it's just a mishmash of ridges and grooves that are cross cutting. There are these chaotic terrains, which may be places where the surface has at least partially melted. There are very few impact craters. You can see on that global image at the left, the one that's blown up here on the right, it's called quill, or if you're Welsh, sure if you're Welsh you pronounce it much better than I can. But there are very few impact craters overall. In fact, we know the rate of impactors, cometary objects that are in the kilometer size class out in the outer solar system at distance of Jupiter. So we know that one of these would hit Europa about every four million years to create a 10-ish kilometer-size crater. We can count up the number of such craters and say that Europa's average surface age is probably about 60 million years, only 60 million years, 1% of the age of the solar system. So in that time, something has repaved most of Europa because we don't see a lot of ancient terrain. We don't see a lot of craters. Europa's probably geologically active today. And then we see these spots, these lenticule, we'll talk about them as they relate to motion of ice, most likely in the interior, in the ice shell of Europa. This is what we think Europa is like on the inside based on what we understand from Galileo data. From tracking the spacecraft as it made flybys of Europa, we could measure the detailed accelerations of the spacecraft, how it sped up or slowed down, and essentially map out the gravity field of the satellite from those 12 flybys. And that tells us how centrally condensed the object is. So we're pretty sure that Europa has an iron core and a Rocky mantle and then an icy layer, something like 100 kilometers thick. But that layer, really I should have said H2O layer, some of it's probably liquid water and some of it's ice. The gravity data themselves don't tell us that. There are other observations that tell us that the ice shell is probably about 20 kilometers thick above a subsurface ocean. Actually, the best evidence for an ocean came from magnetometer data that we'll see in just a moment. First, this is a nice comparison of the volume of water in all of Earth's oceans compared to the volume of water that we believe exists in Europa's global oceans, probably about two times the volume. And so Europa, well on Earth, essentially everywhere there's water, there's evidence for life. On Europa, if there is liquid water, could it be a habitable environment? Could it be a place we could find life today? Mars, of course, has been a target of NASA's exploration and Mars rovers have shown evidence for past conditions for life. We're still trying to understand could there be life today, but most of the science community thinks Mars more likely past life. Europa probably has the conditions for life today. How salty or fresh that water is, we're not sure of, but we're pretty sure it's at least somewhat salty. And that relates to the evidence for Europa's ocean. Now I'm a geologist and geologists were looking for geological clues as to the existence of an ocean, and we'll see some of those. But the best evidence for an ocean at Europa, actually, if you're a New York Times reader, you probably saw the story on Margaret Kivilsson, who turns 90 years old this month. It's still quite active in the field and a member of our Europa Clipper science team. She led the magnetometer team for the Galileo mission. And in making flybys of Europa, the magnetometer team noticed something odd, a signal of a magnetic field, a magnetic disturbance like at Europa. So was that a magnetic field related to Europa itself? It turns out no, because that magnetic field illustrated in this movie at bottom right actually varies. There's a line in there that's representing the magnetic field of Europa and how it's moving, it's swinging, as it's actually rotating. Sorry, that vector is actually the Jovian field felt at Europa, but then you can see those little lines around Europa and they're actually moving and pulsating and twisting. So the Galileo spacecraft measured that magnetic field a couple of times and realized that it's not a stagnant magnetic field associated with Europa itself, but that it's what's called an induced magnetic field. It's magnetic field formed in response to Europa moving through Jupiter's immense magnetic field. And Europa is generating a field to essentially counter Jupiter's field. That's something that happens to conductors, materials that are essentially conducting electricity. So something inside Europa is making Europa behave as a conductor as it moves through Jupiter's magnetic field. And that conductor is in the shallow portion of Europa. It's not the deep core. That would be too far away to have a magnetic effect that was measured. So the logical conclusion is that it's a salty ocean causing that magnetic field associated with Europa in response to Jupiter's field. That's the best evidence that we have today that there's an ocean inside Europa essentially discovered by the magnetopner instrument. If you haven't seen that article on Margaret Killison, I recommend you search science for that article in New York Times just a week or two ago. What could maintain an ocean in Europa today? Europa is about the size of Earth's moon. So it should have cooled off by today. It's small enough that the heat from its formation, radioactive decay, most of that should be lost by now. And like the Earth's moon, Europa should be cold and dead. But this group, at least some of you probably know about tidal heating. This illustration on the lower left, not to scale, is showing that Europa has an eccentric orbit. It's a non-round orbit. And so Europa gets slightly farther and slightly closer to Jupiter as it orbits in an 85-hour orbit. It takes 85 hours to go around three and a half Earth days. And as it does, when it gets closer, it gets stretched out more. And when it's farther, it contracts a bit. It's also nodding back and forth as little yellow dots on that Europa is showing. So all this pulls and pushes on Europa and generates heat, generates frictional heat. So again, not to scale, exaggerated. But if there's indeed an ocean down within Europa, as we think there is from the MAG data and also from geological evidence, then Europa should flex by about 30 meters every time it orbits around Jupiter. So the movie at the bottom right is illustrating what you'd see if you're traveling around with Europa. It's stretching because it's closer to Jupiter and contracting when it's farther, and it's nodding back and forth a bit. And this is generating heat. We know that the heat is concentrated in the ice shell. And it could possibly be concentrated also in the rocky interior. It's meant to be ambiguous in this movie as to whether the rocky interior is heated by this tidal meeting. It depends on how stiff and warm that interior is to start with. But there's at least heat generated inside that icy shell, which can make geology that we see on the surface. So this is essentially the cause of Europa's heat. A way to illustrate this is bending a paperclip back and forth and you touch it to your lips because your lips are very sensitive to that and you can feel that it warms up. There we go. This is a Galileo mosaic of some of the ridged plains on Europa's surface. And we're zooming in on one of those ridges. And I say one, but you see two, they travel around in pairs. They're essentially a double ridge with a trough in the middle. The sun's coming from low on the right here. And this ridge has deformed the previous surface somehow. You can even see evidence of little blocks. Little rocks have rolled down off this thing. There's a little tiny impact crater there. Although these double ridges are probably Europa's most common feature, there isn't full consensus as to how they form. But it probably relates to cracking of the surface. And then as related to that tidal flexing and then probably movement of warm, soft ice up into the crack to push the surface upward. At least that's one model for how these might form. But in any case, the fact that Europa's surface can crack is again related to this squeezing as Europa gets closer and farther to Jupiter. I'm not going to answer all the questions I see popping up, but I do notice something that tells me that you're interested and I appreciate it. And we'll come back to some of those in the Q&A at the end. If I can think fast enough, I'll try to answer as I go. This is an example of what we call a band on Europa's surface. You can see the ridge planes in the background. Hopefully you can see the arrow pointing a little bit. And then there's this swath of reddish stuff that cuts across the surface. If you look carefully, those pre-existing features look like they've been separated, literally pulled apart. And pre-existing features of various orientations are pulled apart. So what we can do is go to literally go to Photoshop and cut these things out and push them back together and the pre-existing features fit back together perfectly. In fact, there's this old band back here and here and that fits back together and this one and this one fit back together. So something cut through the cold, brittle, upper surface of Europa and then it was just pulled apart to form this band. It probably didn't cut all the way to the ocean. It's hard to get a crack all the way down to the ocean. We think the ice shell is 20 kilometers thick from impact craters and from thermal arguments, the arguments of how much title should be put into Europa. What I'm going to show on the right is an illustration, computer model that postdoctoral researcher here at JPL working with me, Sam Howell has put together. There was a press release on this a couple of months ago on his model. He's looked at a model of Europa's interior where the white layer is the surface and the bottom is where the ice ocean boundary is and this blue stuff, that's not supposed to be water. That's supposed to be warmer ice that can actually flow on geological time scales whereas this red layer up top is the colder stiffer ice and he runs his model for a million years and pulls on the sides, very sophisticated model of the interactions of particles. What you're going to see is some white stuff where at the bottom which represents material from the ocean that gets entrained in the warmer flowing ice and ultimately gets to the surface. Here we go. I'm going to yank on this for a million years and the surface is breaking but the bottom is representing warm ice that is flowing like ice in a lava lamp. I'm going to play that again. That's like the blobs in a lava lamp rising up, stirring up, mixing up and then ultimately getting to the surface and the white bits are representing stuff that was in the ocean and we find it's fascinating that in these bands may be stuff that was in Europa's ocean about a million years prior to formation of that band. I'm trying to go to the next slide, but to play in the movie, try that. There we go. There are lots of places where Europa's surface is pulled apart. Well, what about places where it has pulled together and probably know from Earth's geology that there are some induction zones. There are places where one plate of the Earth's crust has pushed down below another and gets subsumed into the mantle, the rocky, warm, rocky mantle of the Earth. Well, at Europa, a similar thing may happen. There's geological evidence of some places that are marked here in this illustration where essentially there's missing material where it seems like the surface has pushed together, kind of opposite of those bands that are pulled apart, pushed together and there's stuff that's missing if you do the reconstruction, stuff that has disappeared into the interior of Europa. So we think those might be somewhat like subduction zones on Earth and could balance all the places we see where Europa's surface has pulled apart. I mentioned impact craters before. I mentioned quill or pooch. Here is a closer-up view. As I mentioned, there are not many impact craters, but here are some of the most prominent ones. Quill is about 20 or 25, oh, I forget exactly, 22 or so kilometers diameter. Here's Mananen, which is of similar size, the rim of it, and you're probably saying, well, I don't really see a crater there. It's not very evident, which is the point. These craters don't have a lot of topography. Here's a smaller one that does go Mananen here. That must be what? About 10 kilometers of scale bar, common scale bar for these images. So small craters seem to be nice and bowl-shaped like craters on the moon, our moon would be, but bigger craters are sensing deeper, warmer portions of this ice shell of Europa. And like pushing on a cake that's still in the oven or just came out of the oven, they'll rebound and fill in somewhat and end up looking somewhat shallow. So these craters tell us that the ice shell is probably warm down there. The biggest such impact structures are Tire and Kalanish, and we can look at them and estimate where the original crater was, because there are these weird bullseye features, and we can trace older structures and then suddenly older structures disappear at a diameter that's about 40 kilometers. Well, a 40 kilometer crater would penetrate down to about 20 kilometers. We think these bullseye-like impact features actually made it all the way to the ocean. Penetrated through the ice shell caused the icy crust to flow inward rapidly until that hole in the ice shell and created these bullseye-like features by breaking that cold brittle ice. Oh, I mentioned cold. Well, cold is, the surface of Europa is about 100 degrees Kelvin, and I still don't know that in Fahrenheit. I apologize, but it's really minus 200 some odd Fahrenheit. At Europa, cold ice is like rock on Earth, but down below the surface, the ice is much more like glacial ice on Earth. Come on. There we go. I mentioned the ice shell acting like a lava lamp, so there's no little illustration of that. These things that we call lenticulate, lenticulate Latin for freckle, probably form from lava lamp-like behavior. Blobs of warm ice moving up from where the ice is warm near the base of the ice shell up toward that colder, differ surface and pushing it up to form a dome or actually coming out onto the surface to form one of these dark spots that we see. If the ice shell is about 15 or 20 kilometers thick or thicker, and we think from other reasons like those impact craters that it's about 20 kilometers thick, then the ice should come back, and the warm ice should rise up and make it to the surface. So it's all pretty self-consistent there. If there are any bugs, any microbes down in that ocean, we may be able to sample them at the surface someday, not with this mission, but with a future mission. The last major type of geological feature on Europa is the aptly-named chaos terrain, and we're looking at blocks. This block is about five kilometers across. We show this next to picture Providence, Rhode Island, where as a postdoc years ago, similar to downtown Providence, Rhode Island, these fractures are similar scale to a highway to an interstate. And these blocks, some of them have seemed to have tilted, have moved around, right? The old bridge plains was essentially mobilized, probably partially melted by some warm stuff from the interior, maybe a huge blob of that warm, mobile ice. That block I pointed to that's Providence-sized is blown up here on the right, and you can see there's a little block next to it that seems to have tilted and partially sunken here. There's such detail in this image. There are a lot of tiny craters here. Most of those are actually craters that were thrown out of quill a thousand kilometers away, secondary craters that were blasted out. There are actually tens of thousands of tiny craters that are thought to be these secondary craters. And yes, a geologist colleague counted them all up to look at their distribution on Europa. How does this chaos-train form? We think probably that this, the warm, let's see, the warmest places in Europa's ice shell are where the tidal heating is actually going to concentrate. And so it could actually get so much heat that it runs away and melts. And it may be that chaos-train forms above a big lake in the ice shell. If part of Europa's ice melts out, then the volume decreases, right? Ice is greater volume than water and will cause the surface to collapse down on top of it. And then this would freeze up again and dome that chaos back up. And so that may have to be how we form some of these chaos regions on Europa. Sorry, I'm hearing there might be an echo out there but I apologize for that. Hopefully my computer sounds off. Should be. There. I'll make sure I don't know if that's any better. There may be plumes at Europa as there are plumes at Saturn's Moon and Celadus. We know that the Cassini mission, the Cassini mission has flown through them, sampled material that came from the interior of Celadus. We'd sure love to do that at the Europa. But we may have plumes as well. There is evidence from the Hubble Space Telescope. It's just at the limit of our resolution that suggests a glow of hydrogen and oxygen that's a few times been seen, maybe half a dozen times, seen on the limit of Europa suggesting there might be activity there. And there was another technique where some astronomers looked at Europa against the backdrop of Jupiter and far from dark regions suggested to possibly be plumes. That would be exciting because then we could fly right through it with this mission and sample material that may have originated from the ocean with less processing from Europa's radiation that bombards the surface of Europa and alters that surface material. So, Europa we think probably has the so-called ingredients for life. On the right is showing a movie from Black Smokers on the Earth's ocean floor. Places where there's warm rock just below the surface and where water seeps in, contacts that warm rock and comes out charged with chemical nutrients to the point that there are these little ecosystems surrounding on these little shrimp and two worms and crazy critters like that. Could something like that exist at Europa? Maybe it's not just microbes, maybe it's even larger organisms. You probably know from past discussions like in the exploration of Mars that we want to look for the ingredients for life. Water, essential elements from which organic molecules can be built, chemical energy that can drive metabolism. And we want to know that we're talking about a stable environment, one that exists long enough for life to develop. Well, we're pretty sure Europa has the water in its ocean, much more than all of Earth's oceans and even within the ice shell. Essential elements, things like carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur are probably there from Europa's formation and from impacts. So we don't know if they're concentrated in the rocky region and whether they've leached out into the water. So we want to understand the chemistry at the surface of Europa and ideally if there are plumes at the subsurface to understand are those elements really there? All the necessary elements. Chemical energy is a tough one. Is there, since we can't depend on sunlight to power life below Europa's ice shell, are there the right chemistry to permit redox reactions, essentially a simple chemical reaction that could power life? Well, at the surface of Europa is bathed by radiation from Jupiter. Jupiter's very powerful magnetosphere. Particles that are blasted off of Io get ionized, charged and then get spun up into Jupiter's magnetic field. Jupiter's acting like a giant particle accelerator and those particles are just slamming into Europa and they break apart the H2O into H and O. The H floats away. The O is left behind and there's literally oxygen and other oxidants sitting on the surface of Europa as a potential fuel for life if they can get into the interior of Europa and we think geological processes can get them down into the interior. Well, that's what we need to find out for the future. And there's also the potential for black smoker-like activity at Europa down there on the ocean floor if the rock is hot. But even if it's not, reactions between water and even cool rock can form hydrogen-rich materials, reductions that would react with the oxidants and could power life. We think Europa's been stable over the age of the solar system. This ocean is probably an ancient one. We're not sure of that. We're monitoring the very subtle motions of the other Galilean satellites, well, the other two on either side of Europa, Ganymede and Io, and Europa as well, and how their orbits are changing over time can give us hints as to whether this activity really has been going on for billions of years. So that leads into the Europa clipper mission and its science objectives. And our main science objectives relate to the ice shell in the ocean, composition, geology, current activity, because those are the ways that we'll get at the potential habitability of Europa. We also will be able to do reconnaissance for potential future lander, understanding what the surface looks like at a very small scale so that we can better design a lander in the future and put it safely onto the surface where we could literally scoop up some of that dark reddish stuff to understand what it is. It's probably sulfur compounds or maybe even salt, NECL, even that are coloring the surface. And we want to know if there are organics in there, and that's something we can search for over the Europa clipper mission, we literally scoop some of that stuff up and put it in a mass spectrometer with a lander that would be even better in the future. And if there are plumes, of course, then we can sample that material and tell if there are organics there. And for that matter, organics being blasted off the surface we can measure as well. The little bubbles on this chart are representing our instruments, 9 or 10 depending on how you count them. We break them into in situ which measure materials right where they are in place or measure fields, such as magnetic fields in place. And the remote sensing instruments, the ones where we're looking and taking a picture or measuring light that's been bounced off the surface or heat that's coming from the surface. So let me speak to these briefly. I'll start with the remote sensing ones. We have an ultraviolet spectrometer. So like the Hubble Space Telescope we'll be able to search for plumes and variations in the atmosphere of Europa. It'll also tell us a bit about the composition of the atmosphere and the surface. We have the Europa imaging system, ICE, which is actually an instrument suite. So there's two there that's depending on how you count it. There's a narrow angle camera and a wide angle camera. Both of them have color. Both of them can do stereo imaging in different ways to understand the landscape in three dimensions. The wide angle camera will give us broad swaths across the surface and stereo in color. And the narrow angle camera can view from far away but also when we're swooping close to the surface as close as 25 kilometers we'll be able to get super high-resolution images. About a half a meter per pixel is what the camera team is guaranteeing that they can do. Ephemus is a thermal imager that'll search for hot spots and also even tell us about surface characteristics, how blocky the surface is. MISE is our infrared spectrometer to look for the chemical fingerprints of infrared light reflected off the surface to tell us composition, map out composition. Reason is our ice penetrating radar. We're going to be able to blast Europa with two different wavelengths of radio wavelengths and then record the signal coming back. And ice, cold ice radar signals can penetrate right through and then bounce off liquid water and come back to the spacecraft. So we're going to be able to look for reflectors under the surface of Europa that indicate liquid water. And perhaps that radar will even penetrate all the way down to the ocean. For the in situ instruments we have a mass spectrometer which will sniff the atmosphere to tell us in extreme detail about the gas composition. SUDA is a dust analyzer looking at dust that's been blown off the surface by tiny impacts and can search for organics that way. Mass specs can also search for organics that are essentially in the gas phase. And if there are plumes, mass specs and SUDA are going to tell us in detail the composition of them. Ice MAG is our magnetometer which will again get at the Galileo experiment of measuring the magnetic field in the vicinity of Europa. But with many, many flybys, we're talking more than 45-ish, we'll be able to tell not just that there is an ocean but we'll be able to tell the thickness and the conductivity of the ocean. Conductivity is a measure of just how conductive the ocean is and that can tell us how salty the ocean is. So we'll know the thickness and the saltiness of the ocean. Combined with the other compositional data, really get a feel for the composition of that ocean. PIMS is a plasma instrument, tells us about the charge particle environment around Europa, how the type of plasma that's there and that's in addition to understanding that plasma, it tells us what the magnetometer needs to know to best get at the magnetic signature and that plasma causes all kinds of havoc with the magnetic signature. This is the representation of our spacecraft. I'll hold it up to the camera again. I should get our good one from the back there. It's probably too hard to see behind me. Our new model of our spacecraft. The solar panels are quite evident. Model in my hands. Whoops, I just lost a radar antenna to the floor. These illustrations show four. We now have five solar panels. These panels are being built by Airbus in the Netherlands. So we're solar powered mission. The instruments are most of the remote sensing instruments are what we call nadir pointed toward Europa as when we're in the flyby position. And when we're in that position, the mass spectrometer, the mass spectrometer, mass specs for the gases and for the dust are facing in the direction the spacecraft is flying. We're flying into the stuff they're trying to collect and analyze and we're looking down at Europa so that we can take measurements with all the instruments at the same time, which is good both for efficiency. It's high radiation environment. We don't want to be wasting time. We're not taking measurements because we're all taking measurements at once. And then all those measurements can be compared to each other. On the right is an illustration. Oh, sorry, I have to point out the radar antennas. There are two different types for those two wavelengths. There are VHF antennas that are these little things we call diving boards. They're four of them hanging off the solar panels. And there are two longer ones. These long 16 meter long metal rods, essentially, for the longer wavelength and those VHF, that's for the shorter wavelength radar signal. And that illustration is showing the position of the radar during the flyby. The solar panels articulate. So when we're not doing a flyby, we can optimize point toward the sun and charge up our batteries. And then the flyby itself is done on batteries. And on the right, you're seeing representation of those 45 or so flybys. And the warmer colors are illustrating more and more radiation through the mission with a total radiation dose of about three mega ads. So that's what we're designing too. Excuse me while I pick up my radar antenna. It was that thing. There we go. This is illustrating the flyby paths. And you can see all on one 3D image there as it rotates around. I think you'll see Jupiter go by in the back here. And you can see that we cover parts of Europa better than others. It's really hard to get the... Oh, there's Jupiter. We can get the side of Europa facing toward Jupiter and facing away from Jupiter very well. But the parts of it coming around now, this is the leading hemisphere and the opposite trailing. We can't cover those as well because then we'd be crashing into Europa. We'd be heading into Europa. We've got to buy it instead. But nonetheless, we can make observations from afar of those regions as we're coming and going. And the maps on the right are showing the coverage of the various remote sensing instruments as we make these flybys and the trajectory paths represented for reason with little dots for where those trajectories cross. So I just wanted to touch on what this multiple flyby architecture really means for us. We get what we sometimes call global regional coverage. We get coverage of regions across the whole globe. 42 is our nominal number of flybys right now, over three and a half years from Jupiter orbit insertion to the end of the nominal mission. Hopefully there'll be an extended one, I think there will. It minimizes time in the radiation environment. We fly by and get out. And the idea is simple repetitive operations. We try to do the same thing with each flyby. Often asked when we might launch. The earliest we could launch would be in the summer of 22 with we might have an Earth. Let's see, if we go on a conventional rocket we're calling that is a delta four heavy or a Falcon heavy, actually the Atlas is out. So we should eliminate that one. It's not big enough to carry the payload. Then it takes as much as seven and a half years because we'd need to do an Earth Venus Earth Earth gravity assist to get out to the outer solar system swing by those other bodies as Galileo the Galileo spacecraft in the Cassini spacecraft did. But as you may know, NASA's developing the space launch system the SLS, which launch period would open a similar time in summer of 22 and we could go on a direct trajectory 2.7 years and that way we can get there before my retirement age, which I would like. Did I mean in orbit of Europa? We're not actually orbiting Europa. We're orbiting Jupiter and flying by Europa many times. We originally did study a Europa orbiter. So you've probably heard the term Europa orbiter a lot but then you're in the spacecraft bathed in the radiation environment for the whole time the mission would last months instead of years. This way we gather lots of data and then broadcast it back in the outer parts of those pedals as we refer to them. And then we'll finish up essentially so with an animation of what the clippers going to do. Things pretty cool. I hope it comes through on the broadcast well enough. This is showing one example flyby the spacecraft solar panels are facing the sun. So it's charging. We're doing ultraviolet observations there as we start to zoom in which instrument is on is illustrated in the lower left and there are also words on the top to illustrate that. Thermal calibration at scan. There are the solar panels rotate and we put the nadir deck facing Europa facing down essentially and start the encounter. There are some instruments that don't move themselves scan themselves we scan the spacecraft across Europa there instead. The orange is the thermal the blue is the high the narrow angle camera the purple is the ultraviolet that flash was the wide angle camera there's another the magnetometer and the plasma instrument are on all the time solar panels are now rotating but the radar and the flyby configuration and away we go with all the instruments on at the same time flying by from somewhere between 25 and 100 kilometers depending on which flyby number it is and we're trying to optimize that balance and then on the way out we do the same thing but backwards in and heels and and observe Europa on the way out we're trying to keep the operations as simple as possible and you'll see that joint scan coming up again for the thermal instrument and the ultraviolet and we'll probably get a beautiful global color picture at the same time there and now that was all done on batteries and with that bounty of data that has been sent from the instruments into the spacecraft's computer brain we can get ready to downlink that back to Earth during the it's about every two weeks we'll make a flyby so we have nearly two weeks to transmit but not all the data will be transmitted in that couple of weeks some of it might wait for the next orbit and as that builds up we might have to when we're doing let's see some flybys of boring old Clisto sorry Clisto we might be transmitting some of that Europa data back and then to finish up we are looking at the ability of a lander for the future to search for evidence of life with clever missions looking for habitability a lander would search for evidence of life to assess the habitability using techniques on the surface and and to characterize the surface for to enable future exploration as well so with that be happy to take questions for the time that we have to do so there's our website which is kind of a placeholder for now we're going to be revealing a brand new website in the next month all right thank you so much we have a plethora of questions here so let's get right to it and so we have Robert asked a question a long time ago any estimate of the thermal profile of the ocean from top to bottom some let's see depends on whether the ocean is well mixed or if it's stratified essentially compositionally but the thought is the ocean is probably pretty well mixed so there's not expected to be a whole lot of temperature variation across it you know it's not too far from the freezing point of water just above the freezing point of water so yeah let's just keep it that it might be warmer pocket if there really are black smokers down on the ocean floor okay so there was a lot of gravitational pushing and pulling there and so David notes or asked is Europa title locked to Jupiter yes just like Earth's moon where's my little Europa Europa is always showing one face toward Jupiter and race and Sarah are kind of well-known features and they mark the point that's facing away from Jupiter so if you know Europa's geography or want to they're along the 180 degree line and then this is the hemisphere opposite that that's always facing toward Jupiter so Europa has a leading and trailing hemisphere because it's always showing one face to Jupiter as it orbits around like our moon does at the Earth okay and Christopher asked the question are any areas on the surface of Europa thin enough that can penetrate at least to some extent or is it just too thick all over most likely the thickness is pretty similar from place to place and sunlight can only make it down 10 centimeters to maybe a meter light will not penetrate very deep within ice so it really is not going to be a good power source for life so it will shallow subsurface but it's depth instead okay and Kevin asked and so I know that there's a large spectroscopy analysis being planned here but he notes that or he asks is are you planning on spectroscopic analysis of the bands did you determine the content of the water whether it's purely geological or potential biogenic so that's main purpose of the infrared spectrometer my is to look for the spectral fingerprints of light reflected off the that dark reddish stuff to try to identify it's composition and for that matter since we're flying so close with mass specs and pseudo the dust the gas analyzer and the dust detector we might we will be able to identify surface features that are associated with uptick compositional changes that are measured by those instruments so we'll be able to say okay that stuff came from one of these dark red bands or from this chaos area okay and a number of people did ask you know there's a number of other questions having to do with a similar sort of thing so I'm having a kind of parses out my thing moving up and down as more questions come in here so Adrian had a question and you would determine something about the time and she said how is four billion years determined as the desirable simmering time is less time possible okay I didn't mean that I didn't mean to represent that as optimal but just to say it's been a long time and plenty of time as we know from Earth plenty of time for life to develop we don't know how long it takes life to develop on Earth it was relatively quick but probably hundreds don't shoot me if I get this wrong it's been a long time since I've taught astrobiology something like hundreds of millions of years a few hundred million years so that's quick right the comparison is to say Enceladus we don't know if it may be just millions or tens of millions of years for example Europa's had long enough time to simmer some think that the resonance that keeps Europa's orbit non-circular and therefore keeps Europa warm may be as ancient as the solar system itself i.e. four and a half billion years old but we're not sure of that Europa may have evolved into the present orbital configuration in the last billion or a few billion years but still billions is more than hundreds of millions we've got lots of questions here and we're not going to get to all of them because we want to protect Robert's time here too but Adrian you know you alluded to this and it reminded me that Adrian had asked about the possibility of an ocean on Enceladus having a similar possible cause are the conditions there similar to what's going on with Europa it's a really interesting comparison we're still learning about Enceladus even though the Cassini mission is now over where data is still being analyzed and understood and the global picture coming yet in fact the Enceladus new Enceladus book is just hitting the the shelves Enceladus it was thought might have had just a south polar sea but now the consensus is that it's probably a global ocean after all but that the ocean is thicker and there's more tidal deformation in the south polar region and Enceladus has lots of geological activity in the south polar region today and in two other big regions of its surface in the past how long ago is not certain but probably tens of millions of years or maybe a little longer as opposed to Europa's global activity so we're still really trying to understand what makes Enceladus tick and how is it similar and how is it different to Europa Lori notes or she asked does the region seem darker or is that perhaps an artifact of the representational colors that you're using that's exactly right the newer regions wherever Europa's been where subsurface material has been exposed Europa's darker and it may be that the stuff comes up dark but it may be that it darkens with time so for example if there's sodium chloride in there it's exposed to radiation or if it contains sulfur then that sulfur might darken and redden when it's exposed to radiation at the same time then we see old features are bright so it seems that stuff may come up darken and then slowly brighten and the brightening might relate to being coated with frost a little bit of speculation now we'll learn a lot more from the mission but that observation is exactly right Kevin asks are there provisions for retasking flyby trajectories based on geyser discoveries on prior flybys how much flexibility do you have we spend much of our science meeting this past summer discussing exactly that what we have the capability to but then that would use to modify flyby trajectory by a little bit but then that takes fuel and then it may be may have ripple effects down the line so we spent much of our meeting discussing if we were to see something would we want to change the trajectory and go after it or would we want to complete our systematic mapping of the decisions on both sides it was good to have the discussion get those opinions out on the table so that we can have a process that allows us to make those decisions once we're at Europa we've got several people that asked we'll have to make this the last question so we apologize for cutting off a lot of really great questions about the radiation environment around Europa and about the hardening of the spacecraft and how you're protecting it and just why is there so much radiation yeah the radiation at Europa would kill you would be a lethal dose in minutes to hours if you're exposed on Europa and the are radiation hard but not to the ridiculous degree they would have to be if we were an orbiter so they're somewhat standard parts in being radiation hard that terrestrial satellites use and we use a lot of shielding for the most sensitive components of the spacecraft so that can allow the the mission to the spacecraft to withstand three mega ads and for everything to be fine but we are also planning for contingencies what if we get there and some component is not working and to ensure that we have the flexibility to pull out of that environment until we understand a problem if need be or to move on without that component as appropriate alright well thank you so much for hanging in there for a little bit over time here I'm sure that we had some great questions unfortunately we couldn't get to them all but I do want to thank you very much Dr. Pappalardo for joining us tonight and this is a wonderful to be able to learn more about the mission learn more about what's been discovered in the past and I learned a lot so thank you so much thank you this is a lot of fun I appreciate all your interest and if I understand right this presentation will be available on your site it will and so this webinar is along with every other webinar is recorded and it will show up in the outreach resources section within the next couple of days we also put it on our YouTube channel and it will show up there in the next few days so it will be widely available for many many people so thank you well thank you very much