LISA KALTENEGGER: And now you're telling me that this is not an amazing time to be alive. Let me go and introduce the next speaker, who will in this beautiful cosmic shore focus a little bit on this other amazing world that we just have on our doorsteps-- not even among our next stars, but among our own stars. Because what we're bringing together also at this point in time is this expertise that we've developed by going to our closest planets, moons in our own solar system, that gives a part of this puzzle of what habitable worlds could be like, and combining that with the amazing possibilities and the statistics that we have about how many worlds are out there around other suns. And every bit that we learn let us discover, as this picture shows, new wonders.
And so, in that spirit, I would like to introduce Jonathan Lunine, who is a David Duncan professor here, and the director of the Center for Radiophysics and Space Science at Cornell, and one of my co-conspirators, if you want, at the Carl Sagan Institute.
And so Jonathan has been on numerous NASA missions-- Cassini, for example. He's part of JWST, Juno mission, and he's proposing as we speak several other ones, because he wants to put in some more of the pieces of us understanding the moons and planets in our own solar system.
And just very recently he got the medal after-- well, he actually got so many medals. Sorry. But he basically got, very recently, the Cassini medal of the European Geophysical Union. And this is just what I wanted to share, because this is an endeavor that doesn't just need astronomers. What we're doing we're needing planetary scientists. We're needing biologists. We're needing chemists. We're trying to understand our planet as a whole. And we need engineers to give us better techniques and better measurements. And so I wanted to just mention that Jonathan just got that to show you that now we're putting these pieces together to understand other worlds, but also hopefully our own place in the universe. And with that, Jonathan Lunine.
JONATHAN LUNINE: Well I'm not sure what I can do after that introduction. That was much too generous. But anyway, thank you, Lisa, and it's an exciting day. Dr. Batalha talked about three different pathways toward discovering life, and I want to talk about the first of those pathways. And I want to do without quite this much amplification, because I tend to talk loudly anyway. That's better.
I want to talk about exploring the planets in our own solar system. And here we have an opportunity, even though the number of planets-- eight or nine, depending on which camp you're in for Pluto --is much smaller than the number of planets that have been discovered around other stars, we can actually go to those planets. We can visit them. We can touch their surfaces. We can sample them. And that provides us with a different way of looking for life, and if we don't find life, trying to understand why it is that those planets are lifeless.
Now I'm not going to concentrate on all the bodies of the solar system, because we've had a long history of planetary exploration already, a history in which Carl Sagan played a pivotal role in many, many different ways. And from that, we have some understanding that there are a few places today which may in fact harbor life, places where it may be possible to actually go and sample life, and study it. And I'm going to focus on four of those, and I like to think of these as suspects, because we don't really know yet if they're guilty of harboring life. We only suspect that they are. And you may have your own favorite suspects. And if you do, let me know, and we'll bring them in for questioning. But these are the ones that in my view and in the view of many are the most likely-- Mars, Europa, Enceladus, and Titan.
And in these short 20 minutes that Professor Kaltenegger has given me, I will try to cover all four of them. Not easy to do. Mars, of course, is the place that we think of the most when we ask the question, is there life elsewhere in our solar system. Mars has had a remarkable history. It's not too far from the Earth. It gets less sunlight than we do by a factor of two, but that's not a huge difference. It's a much smaller planet, though. And it's had a difficult history of trying to hold on to an atmosphere, and maintain liquids on its surface, that 40 years of Mars exploration have now drawn out and described for us in great detail.
And as far as the history of surface exploration of Mars, directly from the surface, that history began with the Viking 1 and Viking 2 Landers in the mid-1970s, missions that Carl Sagan had a very profound role in-- a very important role. And this history has culminated in the exploration of this very elaborate machine, the Curiosity Rover-- Mars Science Lab, MSL, which landed just about two, three years ago, in 2012 in Gale Crater.
And Gale Crater is a very special place on Mars, because it contains in its center a mound of sedimentary deposits that make for a huge mountain. And those sedimentary deposits are potentially accessible by a capable rover. Curiosity will try to get there. And there are sedimentary layers there that will tell us certainly about when Mars began to dry up, and how it dried up chemically. And maybe they harbor clues to life. Maybe there are fossils there. Probably not, but we don't know.
Along the way, what Curiosity has done is to locate places where liquid water has actually run across the surface billions of years ago-- a stream bed with pebbles that are sorted in exactly the way that you would expect water to sort pebbles. Chemical evidence-- and chemical evidence for standing liquid water has been found elsewhere on Mars by two other rovers, Spirit and Opportunity, which have been and continue to be guided-- at least Opportunity --by Professor Steve Squyres here at Cornell.
So Mars is a complex place, and it's a difficult place to explore. But one of the most interesting surprises that the Curiosity Rover has given us-- by the way, this is a self-portrait. It is a selfie. It's one of many. It was taken using an arm that was removed digitally, obviously, but this arm moved around and took pictures of the spacecraft. So here it is sitting on the surface.
One of the more surprising things that Curiosity has found recently is a burst of methane. There's methane in the background atmosphere of Mars. We didn't know that until Curiosity, but it was expected. Just the photochemistry of the atmosphere and material raining down to the surface would change some of the carbon dioxide and water into methane at a very, very low level. But recently Curiosity detected-- in late 2014, a burst of the methane that was about seven to 10 times the background level. And it may have detected an earlier burst as well. It's the exquisitely sensitive instruments on this rover compared to other landed spacecraft that have made this possible.
And if Curiosity were a little bit smarter than it is, it could actually describe its discoveries in poetry. I've tried to do that for it. And the key question which is embedded in this little piece of poetry-- I know I'm never going to be invited to the Poetry Center at Cornell, or any other university for that matter --but the question is this burst of methane. First of all, is it real? It probably is, but there's some possibility that it's contamination. And if it is real, is it from biological processes, or is it from geological processes?
Serpentinization is a geologic process that converts carbon dioxide and water in the presence of the right kinds of rock into methane. Now regardless of whether this is biological or geological, it's evidently a process that is active today, and something in the surface is coming out somehow, periodically. And that's not understood at all. But it will be possible with future instruments that are much more sensitive than those on Curiosity. And this is not easy to do, but it's possible to measure the abundances of the different isotopes of carbon, and to determine if another burst like this occurs when a future spacecraft is there with the right instrumentation, to tell whether this is biologically or geologically produced.
And so we actually have a hope of making a test for extent life on Mars. Now as far as the history of Mars, the possibility of life that began and then became extinct, that may be in the geologic record on the surface. And again, we may actually see some evidence of that. We may be surprised, perhaps, by Curiosity once it gets up into the sedimentary layers of that central mountain, Mount Sharp.
So one could talk an entire semester about Mars. I don't have that amount of time. Let me move on to Europa, Jupiter's Moon-sized moon. Europa is just about the size of the Earth's moon. It's mostly made of rock, like our own moon, but there's an outer layer of water. And it was presumed early on that perhaps that water would be mostly ice, but some early Voyager images showed the surface to be very smooth, and largely devoid of impact craters. And a number of different groups, including at NASA Ames, when Professor Squyres was there, worked out that the tidal heating of Europa by Jupiter would be enough to potentially melt a liquid layer underneath the ice crust.
When Galileo got to Jupiter in the mid-1990s-- the Galileo Orbiter --it took spectacular pictures like this, which showed that the crust of Europa had been fracture, rotated, very much looks like the crust is very thin. And at the same time, a device called a magnetometer on the Galileo Orbiter measured distortions in the magnetic field of Jupiter as it passed by Europa. So the spacecraft passed close to Europa. It found the magnetic field that Jupiter was twisted and distorted in just such a way that you would expect if there were a highly electrically-conducting layer inside of this moon.
And an obviously good electrical conductor is salt water. So that's pretty good evidence that Europa has an ocean. But we don't know how deep below the surface that ocean is. The geology gives an indication that in places, it may be quite close to the surface.
But how do you actually get to that ocean? How do you access it to look for life? There may be places where cracks open and close. It may be possible to sample the water there, or even make observations from fly-bys or orbits. We still don't really know. And the kicker with Europa is that that magnetic field of Jupiter is so powerful that it creates a set of radiation belts, and a radiation environment that would destroy essentially all spacecraft that linger in this vicinity for periods of weeks or months, depending on how they're designed and how they're shielded.
So this is a very difficult target to search for life. And the first step in that search will happen in the next decade. Europa Clipper is a new NASA mission that's planned to go into orbit around Jupiter, fly by Europa, make the measurements that will tell us whether we need to go down and drill, or melt, or whether there are places where the ocean really is exposed to view periodically by tidal stresses.
So stay tuned on Europa. There's a lot of interesting news that will come, but it'll be in the next decade.
So I want to move on now to Saturn, and its two moons, Enceladus and Titan. Saturn is very far away. It's 9 and 1/2 times farther away from the sun than the Earth is, and so it's difficult to get to. It takes a long time. But this spacecraft, the Cassini spacecraft, has discovered remarkable things about the Saturn system. The list of discoveries that Cassini and its entry probe Huygens have made would really fill several pages. It's a remarkable mission. It's been in orbit now for 11 years around Saturn. And I want to focus on the discoveries that have been made for Enceladus and Titan. So this spacecraft, which weighs about three tons on fuel, consists of a Saturn orbiter built by the Jet Propulsion Laboratory, and an atmospheric entry probe that was detached in 2005, six months after arrival, and entered the atmosphere of Titan and descended to the surface.
Now Titan is the only moon in our solar system that has a substantial atmosphere, and it's been a target of interest for a long time.
[MICROPHONE HANDLING NOISE]
Did I do that? Wow.
It's been a target of interest for a long time. And Carl Sagan has written eloquently about this moon. In fact, in the very book that Dr. Batalha moved her to science, Broca's Brain, there is an entire essay on Titan, written in the late 1970s, decades after the atmosphere was discovered, but before Voyager 1 was able to determine for us that that atmosphere is actually quite dense and made of nitrogen.
Carl made a number of educated guesses and inferences based on knowledge of Titan at the time that were quite prescient. And indeed, he assumed that the atmosphere was fairly thick. And so he wrote in one of these essays that Titan will be the easiest object explore in the outer solar system. Nearly atmosphere-less worlds such as Io or the asteroids present a landing problem, because we can't use atmosphere breaking. Giant worlds such as Jupiter and Saturn have the opposite problem. The acceleration due to gravity is so large that it's difficult to devise an atmosphere probe that will not burn up on entry. Titan, however, has a dense enough atmosphere, and a low enough gravity. If it were a little closer, we probably would be launching entry probes there today-- 1978.
1997, the Cassini-Huygens mission, which Carl was deeply involved in, launched. But Carl never got to see it, never got to see the results. He passed away the year before that launch. Nonetheless, a lot of his work went into this, and the Huygen's probe in particular made a number of remarkable discoveries about this moon.
So from Voyager, we knew the atmosphere was mostly nitrogen and admixture of methane. The air pressure at the surface higher than the air pressure in this room. But the temperature, because of the great distance from the Sun, about minus 290 Fahrenheit. So this doesn't look like a promising place to go look for life, but in place of water, which is frozen out, methane does all of the meteorology, forms clouds, rain, and as the Huygens probe discovered, as you see in this image, there are channels, gullies, rivers, et cetera on the surface that are carved by methane.
So this is a view that the Huygens probe took. It's a mosaic of images from about 10 kilometers altitude. Here are the gullies. The probe itself landed about here. And immediately after landing, methane and other organic molecules came pouring out of the surface into the compositional instruments of the probe. And so this is a moon that has a hydrologic cycle, but not a hydrologic cycle of water, a cycle of methane.
The orbiter itself has a radar system that penetrated the opaque haze and clouds of Titan that prevented views from the Earth, and in the northern hemisphere, it was able to map out a whole series of lakes and seas that cover a good portion of the northern hemisphere. Remarkably, also-- and this was not designed into the mission, the radar was able to probe these large seas and determine both their depth and their composition. We were able to detect secondary bounces from the bottom, and the difference in power between the bounce from the top of the sea and the bottom of the sea gave us the composition.
So this was a remarkable set of discoveries, some of which was done here at Cornell, some in the University of Rome by a post-doc Marco Mastrogiuseppe, who is now working here. And one of the results is that Titan's great seas contain about 200 times more hydrocarbon than all the known oil and gas on the planet Earth. And just after the paper reporting this was published, gas prices began to fall around the country. [LAUGHTER] You've seen the result of that today. So you can thank space exploration for another economic benefit, OK.
Cassini has also been able to tell us that there's a liquid water ocean underneath the surface of Titan. Titan's interior turns out to be squishy. As it moves in its non-circular orbit around Saturn, its shape changes in such a way that Cassini could detect that by measuring changes in the mass distribution.
And Titan is also bloated. It has a mixture of rock and ice, but that rock, based on Cassini measurements, has to extend much farther out to the surface than we had expected. And that's probably because the rock is hydrated. If the rock is hydrated-- that is, contains water --for various reasons, this ocean may not be isolated from the rock, but may actually be in contact with the rock. And that makes it interesting from a biological point of view. There might be hydrothermal systems there.
So when we think about looking for life on Titan, there are two places we can think of. One is the liquid water ocean, but it's separated from the surface by 40 kilometers or 50 kilometers of crust. That's very hard to get through. But what about those seas of methane and ethane? Could life exist in those seas? Well obviously, not life as we know it. But could chemistry evolve to the point in a methane solvent where self-organizing systems and structures might arise?
There's evidence for chemistry on the surface of Titan. We see in the atmosphere ethane, methane, acetylene, and hydrogen cyanide. We see the methane and ethane in the seas, but we don't see the acetylene and the hydrogen cyanide on the surface. We see their products. So there is chemistry going on. And maybe in the seas, that chemistry gets to the point where structures that mimic cells or viruses such as this one modeled by James Stevenson, a graduate student here at Cornell, might exist in the seas.
How would we find out? To find out, we'd have to go to land in those seas, and we'd have to measure their composition using a device called a mass spectrometer, which ingests material and analyzes the masses of the molecules present. And if there are particular preferred polymers, like this one proposed by David Usher in chemistry, they would stand out in a mass spectrum against the background of the aerosols and the major lake constituents, or sea constituents.
So we need to go to Titan, and we need to land there. But there's another moon, Enceladus-- I have two minutes, don't I? I do. [LAUGHTER] I started at 2:30, right. So Enceladus is a moon which is very tiny, much tinier than the Earth's moon, but it's in a close orbit around Saturn, and it's subject to tidal stresses. And those tidal stresses, it was speculated, might cause activity. And indeed Cassini has seen a plume of material. It discovered this plume of material coming from jets in the south polar region of Enceladus where there are these fractures. And Cassini's remarkable discoveries are that this plume of material as measured by its instruments contains organic molecules, contains sodium and potassium salts, other types of measurements that Cassini has done have confirmed that there is a liquid water ocean in that south polar region, and indeed there are particles coming out of the plume that suggest that there are high temperatures, and possibly a hydrothermal system present in that ocean.
So Enceladus has all the formal requirements for habitability-- all of them. And the material that's in the interior, in that ocean, is coming out. It's free samples. Cassini doesn't have the kinds of instruments that can determine whether this ocean is inhabited by life. The instruments are simply too old and too crude. But the next generation of instruments sent to do exactly the same thing, flying through the plume of Enceladus just like Cassini does today, could potentially detect life, could detect, for example, amino acids and the pattern of amino acids that are present in that plume.
The pattern in abiotic systems, like meteorites of amino acids, is completely different from that of biotic systems, and it would be straightforward to detect. So sending another probe to Enceladus, flying through the plume, measuring with modern instruments whether there's light present, that's the frontier today of looking for life in our solar system. And it connects up with the search for life elsewhere in the galaxy in the thousands of planets, that we see with missions like Kepler and so on. It's the ground truth part of it. It's the visceral exploration part of it.
And so in this new Institute, this new Carl Sagan Institute, we will bring together two things that Carl was passionate about, the human exploration of the solar system through robotic spacecraft, and the exploration of the entire cosmos, for life, and ultimately perhaps, intelligent life like us.
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Jonathan Lunine, David C. Duncan Professor in the Physical Sciences and director of the Center for Radiophysics and Space Research at Cornell, speaks at the inauguration of the Carl Sagan Institute, May 9, 2015. The inauguration event, "(un)Discovered Worlds," featured a day of public talks given by leading scientists and renowned astronomy pioneers.