Stop mourning Cassini! There’s still a ton of science to be made in this Great Finale
A Conversation With Astronomer Jonathan Lunine
On September 15th 2017, the much beloved and talented Cassini spacecraft will come to a violent end: succumbing to the huge attraction to the gassy giant Saturn, it will enter its atmosphere at a very high speed, plunging into its depths and becoming a ball of flames, until it’s dismembered and crushed by the pressures in those beautiful storms it photographed in the last 13 years.
It was a great affair: Cassini gave us thousands and thousands of superb images that enchanted not only the scientists, but also many millions of people from around the world. And so the world is sad. There’s even a bot on Twitter (@CassiniNooo) that just shouts its grief to its 698 followers…
“But I’m not dead yet”, said the probe last week, through the voice of a scientist from its team: professor Jonathan Lunine, director of the Cornell Center for Astrophysics and Planetary Science and a member of the Cassini science team, working on a variety of aspects of the mission, including the radar and other instruments, since the 1980’s.
“I think it is too early to eulogize Cassini on the occasion of its death, as incineration is five months away. Between now and September, there will be a ton of new science on what’s inside Saturn, how much the rings weigh, and amazing detail on rings, ring-moons and atmosphere — all made possible by these tight, ‘proximal’ orbits”, said mister Lunine in a statement to the world of space enthusiasts.
So we invited him to a virtual chat about this “quintessential discovery machine”, as he describes Cassini, but also about the many great space exploration missions in which he’s involved, like Juno and the future Europa Clipper or the great James Webb Space Telescope.
Speaking from the office at Cornell University, he was happy to talk about those missions and all kinds of space exploration questions. So here’s the long (you’re welcome) and extremely interesting talk we had about the new frontiers in our solar system.
The text was lightly edited. Please note that this was oral discussion, so the transcribed text reflects that style.
Director, Cornell Center for Astrophysics and Planetary Science
You’re involved in a lot of great missions, like Cassini, Juno, Europa Clipper, James Webb Space Telescope… You’re a very lucky astronomer.
Jonathan Lunine: (laughs) I am, that’s true. I have a very broad interest in various areas of astronomy and planetary science, so that’s number one, to have the science background in these various areas. And number two, rather than trying to take the role of, let’s say, the lead of an instrument or Principal Investigator for those missions, I’ve really chosen roles that allow me to do something significant with the mission planning and the data. But each individual role doesn’t take up all of my life, so essentially it’s a matter of choosing the right kind of role in these missions. And I’ve been very fortunate because NASA in particular has, at least up until recently, had the role of interdisciplinary scientist, and that’s the role I have on both Cassini and on James Webb Space Telescope (JWST). This is really perfect for me because I’m able to focus in certain areas of science with several instruments, rather than on a single instrument.
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Let’s talk about the biggest and most exciting now: Cassini. You said to a grieving internet: ‘Stop mourning Cassini. Not yet. It’s really a Grand Finale.’ So what can we expect from these last months?
Over the next four months and 18 days (at the time of the interview, last week) we have a lot of science to do. For me, first and foremost, being so close to Saturn, Cassini will be able to measure the very, very detailed geometry of the magnetic field of Saturn. And by being so close to Saturn and getting the magnetic field in so much detail, we’ll learn about the mechanism of generating that field in a way that we couldn’t with more distant flybys. And then the gravity field. By being so close, Cassini can sense the distribution of mass inside of Saturn, how is the mass arranged, if there’s a heavy element core deep inside the hydrogen and helium envelope, or if we could possibly detect the helium rain in someway — these are exciting prospects, that become possible with these close flybys. And then other areas of science: Cassini will be able to measure the mass of the rings as it makes its close flybys, which will give us the first ever chance to determine just how much material there is in this beautiful ring systems. Cassini will also get the closest up images of the atmosphere that any spacecraft has gotten for Saturn, the sort of resolution where the smallest thing you see might be two or three times the typical football stadium - which is incredibly small on a planet that is almost ten times the radius of the Earth! So these are great science observations that we look forward to and then also sampling the atmosphere of Saturn directly, both during these flybys and in the very last entry flyby, on September 15th.
You’re saying that, if you’re an editor, wait a few months until you publish the textbook on the solar system, because you’ll have to revise it.
That’s true. I mean, this is all new science, science that Cassini has never done before and no spacecraft has done before!
There’s a lot of excitement from the recent NASA conference on water worlds in the solar system, with announcements about hydrogen detected from the ocean in Enceladus and a very possible confirmation of plumes on Europa by Hubble telescope. But Enceladus seems to be the star — and you didn’t expect that at the start of the mission, all those years ago.
Yes, one of the most remarkable discoveries that Cassini made is that there is a plume of gas and ice pouring out of the South polar region of Enceladus, and of course we didn’t knew that before and Cassini made that discovery, but, even more remarkably, it was then able to follow up and study not only the dynamics of the plume, but the composition of the material that’s pouring out into Saturn’s orbit. Cassini made seven flythroughs of the plume, over a period from 2008 to 2015, and what was found was that the plume has, of course, water - water vapour and water ice, but the water ice is salty, the larger grains contain up to 2% salt, which is not very different from the Earth’s oceans, about half (of the value in) the Earth’s oceans. There are organic molecules, both light organics like methane, and then heavy organics whose identity we can’t quite pin down with the Cassini instruments. But these carbon bearing molecules, of course, are the stuff of life. And then Cassini discovered this population of very, very tiny grains of SiO2, silicon dioxide, silicate grains — these are sort of the cousins of what you would find on a beach, where you’d find some quartz sand. What those are telling us is that water is cycling through rock, deep in Enceladus’ interior, and pulling the silicon out of the rock, leaching it out, and then as this hot water gets back into the ocean that silicate then drops out of solution and is blasted into space as tiny grains. That was an indication that there is an ocean in contact with the rock. And during the time of these discoveries Cassini made remote sensing measurements that very convincingly told us that there’s indeed a global ocean underneath the surface that is globe-girdling between the ice layer and the rock layer, so that set up the last observations, which were in October of 2015, to try to measure the presence of molecular hydrogen, H2, which is very important because if indeed there is active reaction between the water and the rock, hot water and rock at the base of the ocean, then it would be very likely that molecular hydrogen would be produced from the reaction of the water with certain kinds of minerals. And indeed that’s exactly what was found, about a percent hydrogen relative to water, suggesting that there’s active chemistry going on today at the base of the ocean. So really this sets us up for saying that the ocean of Enceladus is the best characterised habitable environment outside of the Earth. It’s a place that we know could support life and the next question, which will require a follow on mission, is to find out if life is actually there.
There are skeptics. People were saying that, yes, we found all of these ingredients necessary for life, as we know it, but it’s too much food out there, so maybe nothing consumes it…
Yes, one of the points that was made as soon as our discovery was announced, and in full disclosure I’m a co-author on that hydrogen paper, was, well, gee, you got so much hydrogen that nothing is there eating it up. That’s possible. It’s possible the environment is habitable, but not inhabited. But another possibility is that so much hydrogen is being produced that the organisms that are there are not numerous enough to consume it. And in fact there are places in the Earth’s oceans, on the seafloor of the Earth, where there are hydrothermal systems where so much hydrogen is coming out that the organisms present simply can’t consume it all. And so, it’s too much of a feast and a lot of food gets wasted and, in the case of Enceladus, blasted into space. But it simply may be that the amount of life is limited enough that it can’t consume all that hydrogen. We can speculate on these things, but the only way to know is to go back and look for the molecular signs of life in the plume.
We’re pretty sure we’re gonna go back, it’s too much of an attractive target. With the exception of a catastrophe on Earth, I’ll bet the international agencies, NASA, the Europeans, Japanese, Chinese or Russians, will send, together or alone, a mission there, to be the first to find aliens, be they microbes.
And you did all these discoveries with ‘old’ technology, without being disrespectful to those great engineers. But, naturally, we have much better tech now. What would you put on a future orbiter to find further signs of life?
I’ve thought quite a lot about the question of the next step for Enceladus, so much so that I have a proposal into NASA for a concept called Enceladus Life Finder, or ELF. Well, the most robust way to look for life and to avoid at the same time contaminating that ocean is to do the measurements in the plume of Enceladus, to fly through the plume and not try to land and not try to go into the ocean or even perch on the edge of one of the fractures, because that always leaves open the possibility of contamination by terrestrial organisms. So in flying through the plume we have to work with very little material, tens of nano-grams, and the best technique for dealing with that kind of tenuous sample is mass spectrometry, which is just what Cassini used. But the mass spectrometers on Cassini are a quarter century old, when they were designed, and mass spectrometers that can be flown in space today are much more powerful, they have much better sensitivity and much greater mass range and they can look at the masses to a much, much finer degree, looking at fractional masses associated with binding energies and the nucleus, which allow you to distinguish molecules that might otherwise be regarded as having the same mass. So with mass spectrometry — a tried and true technique in solar system exploration — we can look for signs of life and we can also determine to a much better extent exactly how habitable and for what kind of life is the Enceladus ocean inhabitable.
And what kind of life could be there? People in the recent NASA conference joked about ‘Enceladus shrimp’. And it didn’t seem that strange, because when we hear of hydrothermal vents on the bottom of the ocean on Enceladus, we all imagine the lush environments around our terrestrial hydrothermal vents. But are we jumping the gun here, dreaming of such alien crustaceans? As a serious astrobiologist, how optimistic are you about this sea food?
Well, we’re probably jumping the gun as far as shrimp go. But if you want to imagine hydrothermal vents at the bottom of Enceladus’ ocean, where microbes, single celled organisms, are living and extracting energy from the hydrogen and other food stuffs, I think that’s entirely reasonable. We need to know how much phosphorus and sulphur are present, elements that Cassini couldn’t measure, but which could be measured by ELF. That’s very important to know, how much life could be present there, how many microorganisms could be there.
But certainly, it’s not at all far fetched to imagine microbial communities sitting at the base of this ocean, enjoying the chemical reactions going on between the rock and the water.
Tiny Enceladus was a wonderful surprise for everybody. The initial target for investigations, among the Saturnian moons, was Titan, and we’re very proud, as Europeans, of the Huygens probe. That proved to be an incredible planet. As a Titan expert, surely you wanna go back.
I cut my scientific teeth on Titan, back 35 years ago. Voyager 1 flew by in 1980 and Voyager 2 in ’81 and told us that this atmosphere of this giant moon of Saturn was very dense, that it had nitrogen and methane. But didn’t tell us about the surface. And one way to understand the data was to imagine that the surface of Titan is cloaked in a giant ocean of ethane and methane. Well, Cassini popped that beautiful bubble when it got to Titan… But it did discover that there are seas and lakes in the northern hemisphere and a few lakes in the southern hemisphere of Titan. And again, just like with Enceladus, when Cassini discovered those lakes and seas it was actually able to follow up and tell us what they’re composed of and how deep they are. With the radar system, which was really never designed to do this, Cassini was able to probe the depths of the great seas of Titan, like Ligeia Mare, or Punga and Kraken Mare. And then, by measuring the weakness of the signal coming back from the depths, could tell us that indeed these seas are made of liquid methane and a little bit of ethane and nitrogen. So an enormous amount of hydrocarbon, hundreds of times more than the known oil and gas reserves on the Earth. And then Huygens, this fantastic probe built by the European Space Agency, landed on Titan in 2005 and took wonderful pictures of gullies in a nearby hillside, an icy hill carved by methane rain into these beautiful gullies. But as soon as the probe landed, methane, ethane and some other hydrocarbons came pouring out of the ground into the heated inlet of the instrument, the mass spectrometer. So Titan is full of methane and all of the discoveries that Huygens and Cassini made tell us that there’s the equivalent of an active hydrologic cycle on Titan. When we say hydrologic, we think of water, but in the case of Titan it is methane. It forms the clouds, the rain, the rivers and the seas of Titan, and so it’s a truly bizarre and exotic world, but very, very active.
Can it also form life?
And the big question is this one, yes — could there be a form of biochemistry, a form of life that could develop and be sustained in liquid methane? And, of course, the answer to that is: we don’t know. But we also can’t demonstrate that is physically impossible. We don’t understand the limits beyond which chemistry might or might not be able to form life in a given kind of liquid. I believe that the way to go back to Titan is to land on one of the great seas and float around. It’s a mission concept that a few of us proposed a few years ago, called Titan Mare Explorer (TiME), which was unfortunately not selected. But the idea still stands, that you could splash down into one of these seas. In fact, Huygens could have splashed down if it would have been deployed to the high latitudes rather than the equator. And it would’ve floated in that material. So, send a capsule, splash it down, let it float around in the sea until it finally gets to a shore and measure the detailed composition, see if it’s anything going on that might be suggestive of life being formed or even life existing in that sea.
We published an interview last year with Ellen Stofan, former Chief Scientist of NASA and another supporter of Titan Mare Explorer. You’re also saying, please don’t forget about it, fund it, because we need another probe on Titan.
There are a lot of things that can be done in the Saturnian system. Of course, Enceladus Life Finder is, in my view, the most imperative thing to do. But getting back to Titan and landing on the seas also is critically important. To some extent, I would say that we have very difficult choices, because we’ve been so successful. Cassini has made so many discoveries in the Saturn system, that we really can’t follow up on them all, at least not in our lifetime. So it makes for some very, very difficult choices and interesting dilemmas to which of these fantastic discoveries do we follow up on first.
Isn’t it great that we got this far, to fight over such attractive targets! The most common discussion is that between Enceladus versus Europa. In popular imagination, Europa was the one place where we thought we ‘must’ attempt a landing on. You’re also involved in Europa Clipper mission, an over the pond sister of the European mission JUICE. We had a talk last week with some of the people from the JUICE team and they were excited about visiting not only Europa, but also Callisto and, mainly, Ganymede, other moons with possible subsurface oceans. But you’re going to focus all your efforts on Europa. Tell us about your mission and your objectives there.
The very first ocean within an icy moon that was discovered was of course that of Europa. It was discovered back in the mid to late 1990s by the Galileo orbiter, which was primarily a NASA mission, with some involvement by Germany as well, which orbited Jupiter from the mid 1990s ‘till about 2003. One of the really spectacular discoveries of Galileo was that Europa produces a distortion in Jupiter’s magnetic field, as it orbits around Jupiter, and it’s exactly the distortion you would expect if there’s a large body of salt water under the surface of Europa and not very far below the surface, in fact. Now, Europa is a much bigger moon than Enceladus, it’s hundreds of times greater in volume, so the water that we’re talking about is the equivalent of twice the volume of water in the Earth’s oceans. And we do know that it’s salty, but there’s a wide range of possible values for the saltiness. So that’s all we know. We don’t know the salt content in detail, we don’t know which salts are there, we don’t know if there are organic molecules in the ocean, carbon burning molecules. A lot of things we know about Enceladus we don’t know about Europa, because Galileo didn’t find a plume, and even it had, it didn’t have the instruments to follow up by flying through that plume. So, beginning in 1998–1999, many of us pushed for a mission to Europa. There was nearly one, but it was cancelled by NASA because they felt it had gotten too costly, and so here we are now 17 years after that cancellation and we finally have a mission that is being prepared to go.
Europa Clipper is designed to be a Jupiter orbiter but it makes multiple flybys of Europa, it’s got a fantastic instrument complement including two mass spectrometers that will measure the plume composition, if there are plumes, but they can even detect material that is just being evaporated off the surface, even if there are no plumes, and so with those, plus a remote sensing instruments in the ultraviolet and near-infrared cameras and so forth, we will be able to find out if there are patches of organics on the surface that have been pushed up, welled up through the water escaping from the ocean, and there’s a radar system that will make measurements that will tell us how deep the ocean is — is it down a kilometer or is it down fifty kilometers — what’s the variation. So Europa Clipper will give us everything we need to takes the next step, should we choose to do so, in directly exploring the ocean of Europa and looking for life there. But it is the essential first step, because we do not have for Europa the kind of information we have on Enceladus, from Cassini. Yes, there’s a little bit of a ‘war of the worlds’ that goes on, some people go for Europa, others go for Enceladus. My view is that nature has gifted us with two worlds in the outer system that might have life and wouldn’t it be fantastic if we went to both and discovered that not only is life in both oceans, Europa and Enceladus, but in each case some little difference in the biochemistry that tells us that these had independent origins, and indeed had independent origins from life on Earth. That would be an incredible richness of extraterrestrial biology that we could study.
You joked in one of your presentations that ‘I’m a middle aged man, so please hurry with the budgets and the missions’. But you seem optimistic about it and there seem to be plans for new missions in search for life. Who knows, you might end up as an author on the paper announcing life there…
That would really be wonderful! Joking aside, I don’t really care that much if I’m the one who writes the article, but I would like to actually find out, I would like this to happen before I die. And one’s perspective is very different at 57 than at 27, I have to say. To me, the most frustrating part of this is that the trip times to the Jupiter system and the Saturn system are very long, with the rockets that NASA has available for these missions. It’s five years to Europa and it’s ten years to Enceladus. We could image using larger rockets that are under development, both the NASA Space Launch System, or rockets in private industry. But those (travel times) are daunting, particularly for Enceladus. Nonetheless, what’s ironic is that both life detection events might happen at about the same time because with Europa we have to wait somewhat for the results of Clipper, and for Enceladus it just simply takes longer to get there even though we’re ready to do a life detection mission right now. So I would love this to be happening in the 2020s, but I have a feeling that the first detection of life in the outer solar system, if it’s there, is going to be in the 2030s.
You’re also working as a co-investigator in the Juno mission science team.
Juno is in orbit around Jupiter now, it’s the first solar powered orbiter of a giant planet, part of the New Frontiers class of medium size missions, conceived of by Principal Investigator Scott Bolton, of Southwest Research, and his science team. Juno is all about Jupiter. While we think of many giant planets missions as exploring the moons or rings and so forth, Juno is really all about Jupiter. And what we are discovering as we speak - I used to talk until now in the future tense, but now we’re there so it’s the present tense — we are discovering what the structure of Jupiter is, how the circulation patterns inside Jupiter are organised - we do that through the gravity data; we’re looking ultimately to find out whether Jupiter has a solid core, that will tell us how the planet formed — was it a lengthy two step process, with forming a kind of a super-Earth, and then the gas collapsing on top; or did it form all at once, from an instability in the disk that could have happened very quickly? We also want to understand the magnetic field of Jupiter, the geometry of it, because that will tell us whether it’s generated in the metallic hydrogen region of Jupiter, or the pressures are so great that hydrogen becomes a metal and that in turn will give us more information on the structure. We’re getting beautiful images of the atmosphere, of storm systems, of the poles, both in the optical and also in the near-infrared — a wonderful instrument built and provided by the Italian Space Agency is doing these beautiful infrared observations. And then, with another instrument, we are gradually building up the data needed to measure the abundance of water, deep inside of Jupiter. The Galileo probe, which was delivered by Galileo in the mid-1990s, did not find the amount of water we expected and the thinking is that the water was actually dried out or removed because the probe fell into an unusual region, a hotspot, where there is a lot of dry, sinking air, subsiding air. So water is the primary carrier of oxygen, oxygen is the most abundant of the heavy elements, the non-hydrogen and helium, so if we want to understand the material that went into Jupiter at the beginning, the building blocks of this giant planet, we need to determine the water abundance. Juno will do that, as well as other things, pictures of auroras, measurements of magnetic field, and the key to all of this is that Juno is in the kind of orbit that Cassini has just entered in its proximal orbits - a very, very eccentric orbit, very close to the cloud tops of Jupiter at the close point, and then it goes very far away from Jupiter the most of the orbit in order to avoid getting too much radiation from the very prodigious radiation belts of Jupiter. It’s a remarkable mission, going very well, and I think the discoveries are going to be remarkable.
We, and the rest of the public, really enjoy those fabulous images of the Jovian storms. And we sometimes think about that old question: could there be life in the clouds of Jupiter? We have life in our clouds, coming from down here. Could there also be microbes or other floating live stuff there?
Well, the honest answer is I don’t know. And nobody knows. But, of course, this is an idea that very famously Carl Sagan and his colleague here at Cornell, Edwin Ernest Salpeter, thought about, perhaps it was thirty years ago now, in which they thought about whether you could have buoyant lifeforms that would exist in the temperate regions of Jupiter’s atmosphere, where the water clouds exist, where organic molecules might provide food for these organisms and they imagined things that looked like giant blimps that would float around in this part of the atmosphere. The difficulty I have with this is how do actually form that life to begin with, because in order to have something that can maintain its buoyancy and avoid drifting down deeper into this almost bottomless atmosphere where the temperatures and pressure get so high that carbon bearing molecules would be broken up and destroyed. That requires some sophistication in terms of buoyancy control, mobility and so forth, but the earliest steps toward life could not possibly have included molecules or even systems of molecules with that kind of sophistication. So where is the cradle of life in the atmosphere of Jupiter? To me, that’s the real question, where are the places that are stable for long enough that molecules would have a chance to get together and produce very early life. I think it’s a fascinating idea, but it’s not the first place I would go look for life.
So we’re back at Enceladus. There’s another SF idea, compared with what we’re doing right now, of going to Enceladus and not only orbit and sniff out the plumes, but land, and not only land, but drill or melt our way through the ice until we reach the ocean. How far fetched does this idea seem to you and how hard would it be to avoid contamination, in both directions?
To land on Enceladus to drill and sample the ocean directly, these are not far fetched ideas, but to implement them would require a lot of money - it would be much more expensive than a plume probe like Cassini or ELF. The difficulty, of course, in landing on any surface is that you have to know what the surface is like, you have to be able to operate successfully and then you have to be able to go right where some of these jets are coming out of the fractures to be able to sample them. And then, if you wanted so sample the ocean, you would have to know how far bellow that surface the liquid water has actually come to, it’s quite possible that in the fractures the liquid water rises up to a level not to far below the surface, but still very challenging for direct sampling. So the easiest, most robust, I would say guaranteed, way to sample the ocean is to do it in the plume. Now, if you want to land, then, as you said, you have to worry about contamination and because Enceladus’ ocean seems to be really habitable in the classic sense of the word, if you threw microbes into the ocean they would actually survive. The last thing we would want to do is throw microbes into that ocean and so it would require a very, very strict sterilisation. In the case of Mars, there was always some suspicion that the surface is not where life is — even though Viking was very carefully sterilised, not all subsequent spacecraft have been so carefully sterilised. But for Enceladus you would have to be very, very careful to avoid getting even just a small microbial load into that ocean. And I think that would make the mission even more expensive and in many ways very hazardous — for Enceladus. I would see these as follow on missions to a plume probe, maybe even follow on to a sample return, if it turns out that we find evidence of life, maybe the next step is not landing but doing a collection mission where you go to a plume many times, picking up material and then bringing it back to the Earth. I like those much better than landing.
Right now, the recent discoveries and the recent focus on water worlds means that it’s a race between the outer water worlds and Mars in finding alien life. Mars, until now, gave us all the signals of a former inhabitable world. So it may mean that it’s possible we could find life in two, even three places in the solar system, with completely independent origins and evolution. How cool would that be?
I would just look back to the late 1960s when Mars appeared to be a dead world with craters from the early flyby missions when we knew nothing about the moons of the outer solar system, it was assumed they were just cold icy dead worlds. I know at that time there was a great pessimism about whether we might find evidence for life, living or dead, anywhere in the solar system. Why have things change? They changed because of planetary exploration, because capable spacecraft have been sent out to Mars, to the outer solar system and we find that these places are vastly more interesting then the early attempts as spacecraft exploration lead us to believe.
We talked about the next decades. Can we also dare talk about the next hundred(s) of years? We’re big fans of a recent American TV show called ‘The Expanse’, so we’re dreaming of the colonisation of the solar system.
This is an interesting question, as to what humans will do in the next hundred years in space. Of course, it’s a little bit depressing to think about the fact that last Apollo Moon landing was actually 45 years ago. That’s almost half a century. We’ve been in low Earth orbit since then. If anyone wants to send humans to Mars, let’s say the United States in cooperation with other nations, it’s going to be a huge endeavour, it’s going to make Apollo look like a small program and it will require true international collaboration and it will require persistence over two or three decades. So I don’t know when we’ll see that, but it’s something that we have to recognise it will take decades to accomplish. Now, if we do, the question is then what happens after that, what about colonies? And a great way to test whether self-sustaining colonies are possible in space would be to try to put one on the Moon, which is much closer and allows for a quick return to Earth if something goes wrong. But I think the other point, and we cannot forget this, is that robots and computers and interfaces with humans have changed so much over the last few decades that when you think forward to a hundred years in the future you wonder if the debate about robotics versus human exploration is even relevant at all and whether in fact, either in a real physical sense or in a telepresence sense, humans and robots will simply be verged and be one effort to go out into the solar system. I don’t think we can quite image what that would look like, today, but I think we would be too conservative if we were not to imagine that it’s going to be something very different from this traditional debate about astronauts versus robotic spacecraft.
When we’ll go out there, so will our microbes. Some say it’s unethical to bring them or to intentionally cultivate Mars with them. What’s your take on that?
Sadly, we’ve already introduced microbes from Earth onto the surface of Mars, although typically in places where you don’t expect life exists today. It’s part of the equation, whether we want to go to Mars with human beings or whether we want to leave them even in Martian orbit, let’s say, and have them control sophisticated machines on the surface of Mars. But if we do decide to go and have humans on the surface it would have to be in places that have been certified previously by robots to be uninteresting from the point of view of life and where there is not a possibility that the microbes we carry could be introduced into biologically significant areas. So I think that it doesn’t rule out a human presence on the surface of Mars but it means that we have to be very, very careful about where they go and what they do once they’re there.
Final question. Please imagine three missions you would love to do: one within the budget constrains of a New Frontiers program, one flagship mission and one ideal, even SF, mission.
My immediate reaction to a new New Frontiers mission is to do an exploration of the plumes of Enceladus and look for life, and ELF like mission. ELF fits in so well in the New Frontiers program that to me that’s the obvious mission to do.
What I would actually do with a flagship mission is — and this has been studied and I helped study it — I would actually go back to Titan with a flagship mission. I would spend that particular coin on Titan, because it’s such a diverse and complex world that if you went there with an orbiter that would actually orbit Titan and do very high power radar or imaging to get surface detail much better than what Cassini did and then deploy a probe on the surface or a balloon that would float around or even a helicopter or something. But to do those in tandem, that would be an exploration of a world that in many ways is the once and future Earth — the Earth of the past, in terms of the wealth of primitive organic molecules; and the Earth of the future, in the sense that if there were ever oceans on Titan they dried up now and we’re left with a few seas, so studying the climate of that kind of place may teach us about our own future. But it really requires, in my view, a flagship to do it right.
Now, the fantasy mission that I would do if I didn’t worry too much about the budget… I would certainly go with some very capable nuclear mission to visit each of the giant planets and turn to orbit Europa, to drop a probe there, to go on to Saturn, which is probably covered by my other mission, so go right on to Uranus, find out what those moons are really like, send a probe through the atmosphere of Uranus, then go on to Neptune and finally land on the surface of Triton, which is almost certainly an object from the Kuiper Belt that got trapped four and a half billion years ago, to be able to explore the nitrogen and geysers there and understand how it’s different from or similar to Pluto and other Kuiper Belt objects. And once we got tired of those places maybe launch this magical machine out into the Kuiper Belt. It’s a long, long way away, but I would love to see what Eros is like, this other Kuiper Belt object that’s identical in size to Pluto and just a little smaller than Triton. Just to go there and see what something so far out in the Kuiper Belt, but the same size as Pluto and Triton, what is that really like?
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For 10$, you’ll get a full year (12 issues);
And 50$ will make you a lifetime member!Join the Modern Explorers Club!
You can also help by sharing this project with your friends. Thank you!
