Innumerable Globes Like This One: The Search for Life Beyond the Solar System

good evening everyone this is the 16th year of the Silicon Valley astronomy lecture series my name is Andrew frac Moy I'm the astronomy professor here at Foothill College in Los Altos Hills California and it's really great for me to welcome everyone here in the Smithwick theater and everyone watching us or listening to us on the world wide web to this very exciting lecture in our Silicon Valley astronomy lecture series this series is underwritten by four very good organizations the Astronomical Society of the Pacific NASA's Ames Research Center the SETI Institute and then the Foothill College astronomy program those of you in the room have information about them on your program and everyone else I hope you'll look them up on the web tonight's lecture is a very exciting topic it's entitled innumerable Globes like this one searching for life beyond our solar system this is one of the most interesting areas and productive areas in astronomy and we're delighted to have dr. Terry Haller with us he is a research scientist in the space sciences and astrobiology division of NASA's Ames Research Center he has worked as part of the Curiosity rover science team which is exploring Mars right now and on the science planning team for NASA's new Europa multiple flyby mission Europa's a satellite a moon of Jupiter's which were very excited to explore from a biological point of view he is a Kavli frontier of science fellow a fellow of the California Academy of Sciences and was the american geophysical union 2009 Carl Sagan lecturer in addition he just told me that he won the NASA exceptional achievement award the medal that they gave in 2015 so we're happy to see his being rewarded by all these great organizations and his still making time be with us it's a real pleasure for me to introduce to you dr. Tori Halling well thank you all very much for coming as Andy mentioned I'm local and I love living in a community that values science and I have to say I've really been looking forward to this it's been fun to think about how to make this topic come alive for you guys and I hope that I can convey some of the excitement some of the sense of possibility and also some of the challenges that exist in this field so with that said and now that the exits have been firmly bolted shut and Escape is impossible I will share with you something potentially embarrassing and that is that although this is an astronomy lecture series I am actually not an astronomer oh I know you know we all have our shortcomings and I try to be a productive member of society anyway and actually now that I'm opening up to you although this is a talk about life I'm not a biologist either and so you may be wondering what kind of terrible bait-and-switch you fall and pray to what I am actually is a chemist and what I hope you'll see over the course of the next 3-4 hours or so maybe not quite that long is that this is an endeavor that will not be purely an astronomical one or purely a biological one it will ultimately require the inputs of geophysicists and geo chemists and biologists and astronomers and all of those things converge to me on chemistry that is a language held in common among all of them and I hope that you'll see by the end why we need those things and why chemistry is the language in common so this question are we alone in the universe is by no means a new one and in fact my title here in numeral numerable globes like this one Oh actually before I before I do this I put these folks up here on the title slide so I wouldn't forget to thank them and I actually just did in the spirit having said that that you know this is an endeavor that requires many people actually reached out to many friends and colleagues of mine for materials to try to help really make this stuff tangible so Natalie Battaglia is the mission scientist for Kepler that has enough so many of these exoplanet discoveries she and and the entire kepler team really do a fantastic job of visualizing their data and making it tangible to people and a lot of what you'll see about where we are now comes from Natalie Jeremy Kasdan is helping to design the next generation of telescopes that will actually let us go after this question of whether life is out there Scott Sanford and niki paronto are colleagues of mine at Ames who gave me some of the chemistry data that I will torture you with later and Vicki meadows in the virtual planetary lab so virtual planetary lab is is a group that I'm part of that really has dedicated itself to understanding the scientific context that surrounds the search for life on exoplanets that group led by Vicki meadows has has really been kind of leading the way in in understanding how we go after exoplanets and I'm pleased to be a part of that so there's title innumerable globes like this one references a four centuries old text from this person Giordano Bruno he was a Dominican friar and I'll read to you a few lines of this text because I think that it's really remarkably 4sight 'fl but before I do I want to provide a little bit of context so this was written in 1584 that's about 40 years after Copernicus told the world that in fact the earth revolved around the Sun and not the other way around it still was very contentious at Bruno's time but it was in people's minds but it was still a good 25 years before Galileo first pointed telescope at the heavens so at the time he wrote this no one had actually seen a planet through a telescope they simply were points of light in the sky that behaved a little bit differently than the stars did so with that in mind think about what Bruno wrote he said there are countless suns and countless earths all rotating around their Suns in exactly the same way as the seven planets of our system we see only the Suns because they're the largest bodies and are luminous but their planets remain invisible to us because they're smaller and non luminous the countless worlds in the universe are no worse and no less inhabited than our earth so what is unique about this moment in time is not the question we're asking it's the potential to actually answer it in a scientific way and that's what I'll try to tell you about so what about this notion that there are countless suns and countless earths in fact we have begun to count we know that our galaxy alone is host to about 300 billion stars and the observable universe is maybe 70 billion trillion stars that's a lot of real estate out there right there must be someone so we also have begun to count the planets as of about a quarter century ago and what I want you to watch is the pace of discovery so this is a little bar graph that shows you in cumulative numbers the exoplanets that have been detected beginning in 1989 and watch how this takes off and what you can see actually so you can see different methods of exoplanet discovery there are about half a dozen of them overall that have been brought to bear on this problem and two of them really dominate there's the red one down here and the green one up here and I'll tell you a little bit about those in fact I'm going to tell you mostly about one of them and that is Kepler so as of now at the end of 2015 we know about almost 2000 confirmed planets there are several thousand more that are strongly suspected to be exoplanets when I got to Ames 17 years ago there were two right it's it's amazing the pace of discovery so how do we find these things this is how Kepler finds exoplanets this is our Sun and this is the planet Venus right up here and every once in a while the planet Venus or the planet Mercury or earth for that matter transits across the face of the planet and this is actually something you can see maybe some of you have seen it if you look with the right kind of glasses that protect your eyes you can actually see the little dot of mercury or mercury or Venus moving across the son's face but what if you actually didn't get to see the Sun as a disc what if you only saw it as a point of light then what you would rely on to know that there was a planet there is not with your own eyes but watching the Sun dim just a tiny little bit and the area of this little shadow compared to the area of the Sun overall is about one ten-thousandth that's how sensitive you need to be to the dimming of the star and this is what Kepler actually does it sits and stares at the stars and it watches and every once in a while as the planet moves across the star you can see that the amount of light it sees drops just a little bit and it stays low and when the planet continues or completes its transit the light field comes back up and you see that once and it's interesting and you see it twice and you get pretty curious and if you see it three times you can be pretty convinced that maybe that's a planet right and that's actually what they do they watch for three consecutive transits transits so what you can imagine actually is that your sensitivity to planets like this depends on how often they transit if it happens once every handful of days awesome right look for two weeks and you could actually see several transits enough to say there's a planet if it happens once every year as it would if you were looking at Earth against the Sun you'd have to wait for three or four years to convince yourself that what you've seen as a planet as well it really matters what size planet you're looking at if you saw something that was like this size right moving against the Sun that's a big dimming of light and it's easy to see if you're looking for a diminishment of light of one part in 10,000 right that's not easy to see especially if the Sun has variability and things are going on so I want to show you the same data that I showed you before the number of exoplanets discovered through time but in a slightly different way so here on this axis is the orbital period how long it takes the planet to go around the star earth is here right and I and I circled where earth would be in red and on this axis is how big the planet is so this is one times earth radius four times and 10 and watch the pattern of how this plot gets filled in as the years go by so initially all this stuff is up here these are planets that are very very big everything up here is bigger than Jupiter right and close in so relatively short little theories those are the things that are easiest to discover right and here's where we stand as of 2015 although it seems like maybe I have forgotten something that's what Kepler has given us right amazing and here's earth and now what you notice is these exoplanet discoveries are beginning to push out in this direction longer periods and down in this direction smaller planets and there are a couple that are even right in the neighborhood of Earth and so this starts to get interesting and we have enough discoveries that we can actually look at this in kind of a statistical way so here's a plot of planet size if Earth is one so Earth would fall into this bin then these are planets that are from about one-and-a-half to two times the radius of Earth and up from there this is the number of planets per star so saying there's point three planets per star is like saying you have two and a half kids it doesn't actually happen that way right but it's it's a it's an average of statistical average and there are a few things that you can take home from this right the first is here in the bin that has earth 121.4 Earth radii and here 1.42 two if you add those two up basically it means that that every other planet every other star has a planet about the size of Earth right that's kind of amazing there are lots and lots of planets out there and there's some other cool stuff right Kepler its mission has been to look for habitable planets but it has been this absolute treasure trove of data about exoplanets this stuff that you see here these grey sizes we don't have anything like that in our solar system so all of the rocky planets our solar system kind of falls into nicely into two categories right there's all the stuff in the inner solar system that are rocky planets like Mercury Venus Earth Mars and then everything in the outer solar system that's big and gassy and icy and so forth so that's here and out here and we don't have anything that looks like this in between what are those guys right still trying to figure that out but as we've crowded in on this part of the plot as we've gotten to smaller and smaller planets a few years ago we started getting stuff like this right this is actually taken from the press release NASA's Kepler discovers first earth-sized planet in the habitable zone of another star so what is the habitable zone anyway and why go to the trouble of wording it in this very particular way why not just say NASA discovers habitable planet no NASA discovers first earth-sized planet in the habitable zone of another star so what is the habitable zone this is this idea sometimes referred to as the Goldilocks zone that there's a distance away from the star that is just right for life and what just right means in this case is that the temperature at the surface is right for liquid water right water can exist in a liquid form at the surface and the idea is if there's a blazing hot Sun over there and I walk this way which I promised I wouldn't do too much and I walk this way I get hotter because I'm closer to that star and I go this way and I get a little bit cooler because I'm farther away from the star and in the middle I'm just right and I can have water at the surface and you see several things represented here so on the bottom this is the radius of the orbit of the planet where Earth is 1 so there's earth right there but then you see this funny thing over here right what are these there's this little red guy there's this sort of giant white guy stars of course come in different shapes and sizes some of them are smaller and cooler and dimmer some of them are larger and burn much brighter and hotter and so the distance that is right for their planet to be away in order for water to be liquid varies depending on the kind of star that planet is orbiting here the planet can be very close in if it's something like our own Sun it's a middle distance and as you get to bigger brighter stars it would have to move outward so this idea of the habitable zone sometimes gets some flack from people right so and II told you I'm involved in planning this mission to Europa which is you know way out here outside the habitable zone but the interest in that mission is understanding whether Europa is habitable and in fact inhabited right so so why this notion of the habitable zone when we know for sure there can be places outside it that are habitable the point is that that it becomes important to think about places where water is liquid on the surface because we are not trying with this Grahame to say where life is possible we're trying instead to say where we could detect it and I'll try to come back to that point a little bit later on that's the reason for having the habitable zone idea where do you look to have a chance of detecting life so what can we say right now based on things we can actually observe and what can't we say well we can say a lot about the star because we see the star we see its light we can say how far away it is what size it is how big what type of star that tells us something about its light spectrum we could even tell the age of the star and knowing something about the age of the star we know enough about the physics of stars and and their evolution that we can say something about its history right was a tempestuous in its youth what did it cause problems for any planets orbitting so we actually can say a lot about the star but what about the planet right that's down here remember you don't get this big spatial view that shows you the planet as a disc all you get is a tiny little point of light that you see periodically dimming so what can we say well we can say something about the orbital period and that lets us know how far away it is so we do know how far from the star these planets that we're finding are and what's cool is there are these two main methods of finding stars there's the Kepler method that I showed you there's another one called radial velocity it also gives the orbital period but instead of saying how big the disk is it actually tells you something about how massive the planet is and if we know those two things we can make a statement about densities so if we have both of these working in concert we can make a statement about density and that at least gives us some constraint on what the planet might be made of in bulk right is it mostly metal is it metal and rock like we are is there a lot of water or gas or whatever so this allows us to actually constrain something about the planet without actually seeing it or visualizing it what don't we know based on what we can do right now we don't know anything about the surface or atmosphere composition because we can't actually see it all we're looking at as a shadow and I put a little asterisk here because that's not entirely true there are a few planets out there for which we've actually been able to do this it's just they're not the ones that are interesting to us from the perspective of looking for life so if we don't know anything about that composition don't know for example whether or how much water is there right if there's no water there to begin with it really doesn't matter whether the planet is close enough to the Sun for water to be liquid there's just no water we don't know anything about whether there might be greenhouse gases in the atmosphere whether there are ingredients for life we don't know how reflective that planet might be why mention this by the way why mention who cares how reflective the planet is or if there are greenhouse gases in there this is the reason right what we really want is a statement about the temperature at the surface of the planet the idea of the habitable zone is that we're trying to say if there's water there would it be in the liquid form are there oceans and lakes or is the entire thing completely frozen over as a ball of ice so what determines that if we ask that question for our own earth it's a couple of things so the main one that we just talked about is how much energy is received from the star right how close is the planet to the star how much energy is it getting but we know that if we can see the planet at all we look up in the sky and we see Venus as a you know as a morning star or an evening star or Jupiter things like that some of that sunlight is getting reflected away right so it matters not only how much energy is received but also how much is reflected back out into space that's energy that the planet absorbs and then as the planet heats up it radiates some of its energy back out to space so it matters how much the planet radiates out to space and we know from our own planet that we have a greenhouse effect which is like a blanket that serves to hold in some of that heat all of those things collectively are what determine the surface temperature of our planet they are what control whether water is liquid or not here on earth and which of these things can we know about for exoplanets based on what we can actually observe now only this one right we don't know about the others we don't know how much is reflected back out to space because we don't know how reflective the planets are we have no idea about greenhouse gases in the atmosphere or about the the radiant energy of the planet and that's why we're careful about these statements that's why we say that the planet is in the habitable zone right we think it's in an area where where the conditions might be right to keep water liquid at the surface but we don't know for sure and just to give some perspective on these numbers I mean maybe these are throw aways right who cares you know how reflective of the planet is or how much greenhouse there is we can actually look to our own solar system for some sense of perspective we need look no further than Earth Venus and Mars so the main parameter that we talked about how close to the Sun are you how close to the campfire right is how much sunlight are you getting so if we think of the earth as one Venus gets almost twice as much because it orbits much closer in Mars I think I've lost my laser pointer Mars gets only about half as much light right so you know that tells you something about the planets but then if you look at how reflective they are earth reflects away about thirty percent of its light Venus more than twice as much so actually the amount of sunlight that Venus actually absorbs is less than we get here on earth despite the fact that it's closer okay Mars reflects much less of it light and so so it absorbs a reasonable amount of sunlight as well but what really explains the temperature of these planets is the amount of greenhouse warming and this is actually instructive to look at right so Earth has a natural greenhouse even a exclusive of what we're doing pumping carbon dioxide into the atmosphere earth has a natural greenhouse that comes mostly from water vapour in the atmosphere and it gives us about 3334 degrees centigrade of extra warming warmth that we wouldn't have otherwise Venus has the same thing but it has an atmosphere that is 90 times as big as our own and made almost entirely of carbon dioxide that's worth a greenhouse effect of more than 500 degrees Celsius that world is scorching hot at the surface and Mars has a stream Li thin atmosphere and very little greenhouse effect and it's cold on the surface water couldn't exist in a liquid form there and I put this up only to be instructive about the fact that it matters to consider these parameters and these are parameters that we just don't know yet because we don't have the ability to observe them but this is what Kepler has shown us so far this is a habitable zone seen in green here all of these planets I got the pointer back so the solid blue ones these are planets we know about and are confirmed the yellow open circles are things we we think our planet candidates and these are planet candidates here and actually there are quite a few in the habitable zone so just in the small patch of sky that Kepler has actually looked at it's discovered quite a few planets and here you see Verna Venus Earth and Mars for reference and some of these are actually quite close so some of these are really pretty similar to where earth lies in the habitable zone and pretty similar to Earth in size so we know enough about these things we've discovered enough of them to have sort of a statistical view of how common these habitable planets might be and Natalie Battaglia has a really great analogy for doing this so if you think about the Milky Way galaxy our galaxy has scaled to about the same size as the United States and you ask the question how far do you have to go from this spot before you find the first earth-sized planet in a habitable zone of its star right what distance would that be so by show of hands who thinks we have to leave the state of California to get there don't be shy you all have to raise your hand for something who thinks we have to go outside the Bay Area right maybe up to Lake Tahoe it's kind of nice up there outside of Mountain View so actually you could get there walking back to your car it's about a quarter mile from here by the time you reach the parking lot you'd have reached the first habitable planet there abundant and we won't have to look very far to find them and actually Kepler hasn't looked in our little particular neighborhood of the galaxy but we can use those statistics to say the first habitable planet we encounter should be about three parsecs that's about 10 light-years from us and so if we look out to about three times that distance okay this is about 30 light-years from us these are all the stars within that radius of us and statistically speaking there should be about 25 or 30 planets within the habitable zone of their stars right so this is stuff we can actually see we actually have a potential to look out and get some answers to these questions so let's go right I want to make the point though that looking for life beyond the solar system is a lot different than looking for life within it and that may seem like an obvious statement but I will try to make that point in as heavy-handed away as I can what can we do within our own solar system we as a species over the last five decades or so have sent tens of spacecraft toward Mars we have mapped it so effectively with orbital imagery that you can tour it in Google Mars and actually a lot of that imagery is way better in resolution than what you find in Google Earth for example we have driven more than a marathons worth of distance on the surface of Mars we have lifted up rocks and turned them over to peek underneath we have drilled holes in the ground and looked inside and we have filmed ourselves doing it this is actually a picture of the Curiosity rover right here descending on its parachute has captured by a spacecraft orbiting 250 kilometers above that is one of the most remarkable images I've ever seen and it shows you that even NASA is not above the occasional selfie that one did any of you happen to catch the lecture last year by Carolyn Porco really excellent lecture last year some of you I'm glad that a few of you did so Carolyn is the imaging lead on the Cassini spacecraft that has gone to Saturn and it was an hour full of some of the most stunning imagery I think I've ever seen and she had a cherry pick it from among hundreds or even thousands of comparably stunning images there are movies of storms on Saturn there are pictures of waves in the Rings there are jets from the moon Enceladus really extraordinary stuff and that's just the imagery the science yield from the other instruments is comparably good and that's what you can do when you take a spacecraft the size of a school bus and load it full of cameras and capable science instruments and let it drive around the Saturn system for a dozen years amazing what you can do when you're in your own neighborhood but what if all you get to see is just a tiny little point of light which actually many of you can't probably see from where you are so what if that's all you get little pinprick of light or this are those habitable is there life there how would you know right in fact one of these is decidedly not habitable one of these might be somewhere under the surface and maybe was in the past and this one is not only habitable but there's reasonable evidence that there's life there the point is when you're in the solar system it's tangible you can pick up you can look at you can ingest and analyze when you're looking outside the solar system all you get is light but light is actually a lot right and actually this picture is a modern-day cousin to what I think is an absolutely iconic image this is what Voyager 1 saw from about four billion miles away as it looked back toward home and right up here where the arrow is that's our planet Earth that's what Carl Sagan called the pale blue dot and he actually wrote quite poetically about it but you can begin to see some of what the problem is so it's not just a little dot hanging out by itself it's actually kind of obscured and lost in the hazy glow or whatever that is and it tells you part of what the problem is because if I look at two things on the horizon a star and a planet and I start to back away from them they appear to me to get closer and closer and ultimately they'll be very difficult to resolve and actually we can visualize this so suppose we take the Hubble Space Telescope that has given us these extraordinary images of deep space and we bring it to bear on this problem and we put it at a distance of Mars and ask it to look back at the earth and moon it would look something like this that's actually pretty remarkable if you think about it right looking from tens of millions of miles away and you still see this much but what if you move it out to 20 astronomical units that's about the orbit of Uranus it would look like this you can actually still see the moon a little bit and you can resolve some of the detail on earth now suppose we go ten times farther away Voyager one is about a hundred and thirty-four astronomical units from Earth suppose we go out to two hundred now you see it as a faint dot but still a pretty well resolved dot and now we go a hundred times farther still and you begin to see the problem creeping in now the planet starts to get lost a little bit in the glow of the star and if we go ten times farther still so this is the distance now between us and the very nearest star Alpha Centauri so if we looked back at our solar system from Alpha Centauri this is what we would see I put a circle where earth would be and you can see that it's completely lost in the glare and actually Bruno told us that this would happen we see only the sun's their planets remain invisible to us how bad is this problem the star is about ten billion times brighter than the planet that's how much brighter the Sun is than Earth and if you think of the sky as representing a hundred eighty degrees from Horizon to Horizon the distance between them that you would perceive is about two ten thousandth of a degree so that's a bit of a fly in the ointment fortunately the astronomers are real smart don't tell them I said that because they'll get swell heads about it but there's a little brain power that they can bring to bear on this problem and we have engineers who can gently put down a mini-cooper sized rover on the surface of a planet a hundred million miles away by lowering it from a hovering rocket so they'll they'll they'll take care of this and in fact there are a couple of concepts that are in development now and that are showing real promise for this and they both amount to kind of doing this so the spotlight is there if I want to see who's in the back I put my hand up like this right and I block out the light simple one of those happens inside this cow inside the telescope the other actually happens outside the telescope and that's the one I'm going to show you now because frankly it seems more like something that comes out of a 60s era Bond movie than an actual thing so look at this here's the telescope and this thing here's the telescope this thing that's unfolding in space is a star shade right here's the part where the evil supervillain holds the earth ransom by blocking out the light of the Sun so watch what happens as the star shade moves in front of the star so first there's the glaring light of the Sun we put this star shade in front of it and we can actually resolve the planets and what's really cool about this so this star shade you have to imagine something that's about half the size of a football field its massive and it's it's about 50,000 kilometers away from the telescope but what's neat about that is if you move it a few centimeters at a distance of 50,000 kilometers from the telescope you have incredibly fine control on how you're controlling the size of that disk against the star and a few of you may be wondering why that sort of you know interesting flower looking pattern instead of just a plain disc so it turns out that light can actually turn corners a little bit like kind of bends around objects and if you put just a plain disc in front of the star you have a problem that light bends around so the last decade or so has been spent understanding how to construct the edges so that you eliminate that problem right and in the in the video what you saw is that you know the star disappears and you can see jupiter-like planet orbiting and that kind of thing that's not how it look in real life of course but if we do this right and it works the way that it's projected to work we might actually see something like this if we looked back at our own solar system so here's the residual light from the star and there's earth actually peeking out and the astronomers would be thrilled to get an image like this right to have that little dot of light on which to make a discrimination is there life on that planet or not so what about Bruno's final prediction the countless worlds in the universe are no worse and no less inhabited than our earth is that true if we can make these telescopes work the way we think we can we actually may be able to address that question and the idea behind how we're gonna do it is actually very simple right it's so simple that we can demonstrate it here as a group okay and this demonstration works best if everybody takes part so I hope you will right here's what I want you to do take a breath and hold it okay so several important things just happened the most important from my perspective at least is that an entire auditorium full of people was literally waiting in breathless anticipation of what I was going to say next thank you all for being the fuel of that little ego trip but there are some other less narcissistic things that also happened when you did that you changed the composition of the atmosphere in the room what you breathed in came out looking different and as a result the composition chemically speaking of our environment changed and it changed in ways that alter the light that would come off of our planet right it's something that we could see if we looked with the right kind of eyes you did that using an energy source that could just as well fuel life that is wildly different from our own energy for me is energy for anything right doesn't matter but and I hate to be the one to break this to you what you just did was a little bit boring from the perspective of looking for life so this is a whole bunch of assertions that I'll try to back up for you over the next handful of slides and really what this boils down to is we need to make our discrimination based on light right we need to look with the right kind of eyes and say based on a little bit of light from the planet is there life there so most of you probably know what we perceive as white light from the Sun is in fact composed of many different colors of light representing many wavelengths so if you were to pass light through a prism as did the noted English physicist Pink Floyd in their now famous Dark Side of the Moon experiments you would find that the white light is broken in two colors right and instead of being sort of you know the the several distinct colors violet indigo blue and green yellow orange and red in fact it's a whole continuum of colors and it wouldn't matter how finely you chopped up that spectrum you'd see that this little slice was slightly different from that little slice and when we perceive color so suppose that we look at a leaf and this is a maple leaf just in case any of you were wondering because I'm half Canadian didn't want you to look at the Pink Floyd album cover and get the wrong idea about what that might be if you look at a life if you look at a leaf and you see green what's happening is this so here's a plot of wavelength on this axis that's what controls the color of the light we see and I've put them here right so here's violet indigo blue and green this is the part of the light spectrum that we see okay and what happens is the white light comes in and when it interacts with the matter of the leaf it changes so a little bit of the light is absorbed here I've lost this so a little bit of the light is absorbed over around 700 or so a little bit of the light is absorbed around 450 or so that's chlorophyll doing its job it's actually extracting energy out of the light that hits it and what's left is mostly green and that bounces back and that's what we see and the point of saying this is we perceive color or things like that that's actually chemical information and if you break it down in this way if you spread the spectrum apart and look at it in this kind of graph that's chemical information that you can actually see so what we perceive as color is information about molecules and many of you probably know that that what we see the part of the electromagnetic spectrum that we see is only a very fine sliver of it right if you go way out in this direction over here to much shorter wavelengths that's x-rays for example and if you go over there there are radio waves or microwaves or so we perceive only a very fine part of that spectrum but there's value in looking with different eyes and I'll direct your attention to this part over here so I've said that we see mostly green here because that's the part that bounces back to us but look at this feature here right the most reflective part of the leaf is not the green part right here it's way out in this red light that we don't even see with our own eyes but fortunately there are cameras that can see so what would we perceive if we looked at that what would we see if we look through different eyes you can actually take infrared photographs this is what we would see the green of the leaves is gone because the single most reflective thing is that infrared light that we don't perceive with our own eyes but it's there and there's valuable chemical information in it what if we look a little bit further into the infrared if we could see through different eyes we would see that we all glow with our own light isn't that a nice thought all of us are glowing with our own light of course everything else is - anything that has a temperature greater than zero is glowing but it's information right there's energy coming out there's a potential for energy to be extracted and if we see the interaction of matter with those wavelengths of light we can make some interesting statements about what's there so the experiment we just did I made the claim that you breathed in you change the chemical composition of the room around you so how would we actually see that now that we know we can see information by looking at the light so this is exactly the same kind of plot that I just showed you it's wavelength here only now we're looking way out into the infrared okay and here is how much light shines through so in this case I took a little bit of air and I passed some light through it and I asked how much light came through so if all the light passed through if none of it interacted with the molecules in the air you would see a line right up here right a hundred percent but what you see actually is some interesting hair or fuzz so there's a little bit over here there's a peak sort of in the middle and then there's a peak out on the far end and what you're seeing is places where the energy of the light has been absorbed by molecules in the atmosphere in this case its water that's absorbing some light in this case carbon dioxide and in the far case water again so we're actually seeing what molecules are in the air and not only that but how many of them are in the air by looking in this different region of the spectrum by looking with different eyes so this is what the air looked like before we did our experiment what about after we breezed out so I did this experiment I breathed into the instrument that did these measurements and here's what happened right certainly different very different right there is much more water much more carbon dioxide much more water here maybe not surprising I mean that's kind of the way you would think of it thank you very much for the laser pointer we'll actually be able to see again so much more of all of these things but there's more of what was already there there's not anything new and that's why I said what you did was a little bit boring because when the earth breathes as it does through volcanoes it breathes out about the same thing that you do carbon dioxide and water so you are doing something that was going to happen anyway and from the perspective of looking for life that's kind of boring and I have to tell you actually I worked really hard to make this interesting because I knew this would be the main result so right before I did this experiment I took a couple of cloves of raw garlic and I crunched them up right and then right away I breathed into the spectrometer and I was really hoping that I would see those garlic odor molecules show up in the spectrum and I have to tell you for three hours afterwards even those of you in the back of the room would have known what I did but it didn't show up here right and it makes the point we are looking for signals that are big and bold and a major change so what is it that we're looking for I mean if what we just did is boring and ineffective from the standpoint of looking for life what are we looking for and in the most general terms I can offer we need things that we can see right meaning it needs to be a planet scale change that happens at the surface and affects the light that's reflected either off the surface or through the atmosphere it needs to be something big and it needs to be something that we can't explain by any process or means other than biology right we have to exhaust all other possible explanations for what we see in the case of the earth the co2 the carbon dioxide and the water that we breathed out can also be made by volcanoes and other stuff right there's easily another explanation for it we're looking for something that could not exist or we can't explain otherwise and that's a tall order because we're asking to understand planets that are occurring up the processes that are occurring on planets that we really don't know very much and this is where it becomes important for the geochemists in the geophysicist and the atmospheric chemists all to become involved in this problem and understand the system as a whole so what is it that make makes earth look unique relative to its peers in the solar system if you look at Venus and this is exactly the same kind of graph right so here's wavelength here and here's the amount of light that's absorbed so if you look at Venus Venus has a very thick atmosphere of carbon dioxide and some of the light in that part of the spectrum is put out by co2 so we see the co2 we look at Mars it's the same thing but those are both frankly boring for exactly the reason that I said what you did was boring Earth has that same boring aspect but this is interesting right this for those of you who can't see in the back is ozone and ozone comes from oxygen it is what makes earth look unique from a distance and how did it get here right we sort of take for granted that we have an atmosphere filled with oxygen but we didn't always earth started out as a planet with no oxygen and and spent that way for about two billion years or so we have these to thank so we think of oxygen as coming from photosynthesis which comes from plants right but the plants learned how to do it from these cyanobacteria that predated them by a billion and a half years or so these are tiny little micro organisms can't see them with the naked eye but Louis Pasteur the French microbiologist who knew a thing or two about the capabilities and microbes said the power of the infinitesimal can be infinite you could fit a trillion of these things in the palm of your hand that's how small they are but over geologic time they took a planet with no oxygen and they filled the atmosphere to the 20% oxygen that it now has right that's what we are looking for we have a very difficult time explaining the presence of that oxygen on our earth in any other way and there's enough of it there that we could see it from light-years away if we looked with the right kind of eyes that's actually the reason for the whole concept of the habitable zone just to come back to that point remember I said the habitable zone is not meant to exclude the possibility for life in places like Europa or whatever else it's meant to say where could water be liquid at the surface and this is the reason if you want to do photosynthesis if you think that photosynthesis is the only way to get this planet scale signature that's really difficult to to obtain any other way or explain any other way you need two things you need sunlight and you need water and those things have to coexist at the surface that's why we have the concept of the habitable zone that's what its purpose is it's not to say where could life be possible it's to say where could we have a chance of finding it so let's actually talk a little bit more about oxygen because oxygen turns out to be pretty instructive and there are three questions that I want to ask a lot of the focus gets placed on oxygen and so I want to talk a little bit about it and the first is is oxygen and obligate product of photosynthesis if you have photosynthesis emerge does it always make oxygen so the first answer is easy no right here's a picture of two things so these green guys are the cyanobacteria that we just talked about they're green because they have chlorophyll and they do oxygen producing photosynthesis and cozied up right next to them these tiny little purple things they photosynthesize but they don't make oxygen right there are actually several kinds of photosynthesis that that don't make oxygen at all and this one biochemically is quite a lot simpler than this one and in evolutionary terms it predated so this non oxygen producing photosynthesis predated oxygen producing photosynthesis by maybe a billion years or so so if you think about our planet for about half the history of life on Earth which dates back maybe 3.8 billion years or so ago we had life we even had photosynthetic life but we had no oxygen that could be detected from far away so that's one of the key problems facing us now and even in my research group is what other signatures of life are there what else does life make that can be seen on the surface or makes its way into the atmosphere and how does the planet process those things what form do they ultimately take and what would we see if we looked at a telescope is oxygen a unique product of biology is it a uniquely biogenic signature and the bad news is it's not actually there are at least four different ways identified four different processes that will fill a planet's atmosphere with oxygen right if we look in the air around us there's water h2o carbon dioxide co2 there's oxygen there right in locked up in molecules and if there's a way to free it like for example if a photon from the Sun bangs into it really hard and breaks it apart you actually couldn't get oxygen right and we need look no further than our next-door neighbor there's actually oxygen there on Mars not a lot but a little and there surely isn't photosynthetic life at the surface so we know we actually have an example of a place where processes like this are happening and it can give us these false positives these red herrings as we search for life so the good news is that if we understand the context so if we understand something about the kind of star it is and what its light field looks like if we understand how the planet operates at least as much as we can say and we look for other molecules things in conjunction with oxygen like carbon monoxide or methane or other molecules we can have some clues as to the source right if we looked at oxygen on a planet like Earth knowing what we know about the Sun and the geologic context we could say that must come from life right and if we look on other places we have the potential to use these other things other molecules other bits of context to also say is that oxygen unique to life so lastly is oxygen emblematic of our being unimaginative or parochial in the way we think about life does anyone know what that is out of curiosity it's the Horta right the Horta comes from the original Star Trek and it was a creature made out of silicon right this idea that life could be made out of something very different sticks like a splinter in the mind I don't think I've ever given a public talk where this question didn't come up at the end of it so I was part of a panel discussion once actually about five years or so ago public panel discussion and it was three proper astronomers and me and they had to raid us kind of from the most here and now to the most sort of you know out in the future kind of science so I was sitting down at the far end and we did our discussion and a question came from the audience about you know could life be made of something very different and actually it was phrased in kind of an out-there sort of way and this question comes and the three astronomers in perfect unison I mean as if they had rehearsed it all went Tori so this is my niche apparently right I'm the leftfielder of the exoplanet community but people are interested I understand and actually Carl Sagan summed up the problem really nicely as he often did he said there's a famous book published about 1912 by Laurence J Henderson in which Henderson concludes that life necessarily must be based on carbon and water and habits higher forms metabolizing free oxygen I personally find this conclusion suspect if only because lawrence henderson was made of carbon and water and metabolized free oxygen henderson had a vested interest so but but you know is it possible could life be made of something else so the truthful and and but unsatisfying answer is that from the standpoint of exoplanets it actually doesn't matter all that much it matters a little but remember that what we're looking at when we look for evidence of life is not going to be the life itself it's not going to be the molecules of which the thing is made it's going to be what the thing does right does it make oxygen or does it spit out carbon dioxide or something like that doesn't matter so much what it's made of it actually matters more to think about what the life is made of and what its requirements are to know where to point your telescope in the first place and I guarantee you that if we have you know if we look out our sort of 10 parsecs or so and we have several dozen worlds that we could point our telescope at we're gonna go for the ones where we know have Kitka conditions that are suitable for life originating we're going to go for the ones that we know have water that we know have carbon because that's where we know life can survive but I understand that's an unsatisfying answer and people want to know about this so there actually has been some serious scientific thought dedicated toward this and there was a National Research Council study convened around this actually a number of very prominent scientists participated in this and they address themselves to this question if we think as broadly as we possibly can you know what could life be made of and they published a report which you can download right if you're fascinated by this topic and you want to read a hundred fifty pages about it you can go and download that it's easy to find on the web but I'll summarize for you they said they said if you think as broadly as you can really really the only absolute requirement for life is energy everything we understand about physics and chemistry dictates that life requires a source of energy it's probably made of carbon so they made the point they think it's carbon and actually Carl Sagan kind of said that he thought of himself as a carbon chauvinist despite the statement that I just made and not so much a water chauvinist and actually that's a reasonably consistent viewpoint so this is how I would have looked at it as well a handful of years ago we've asked that question and they said it requires a liquid but they went out of their way to say that there's no fundamental reason that liquid has to be water so this was the the summary view point of this this group of people is that life probably as made of carbon probably doesn't need to have water really could be any liquid at all and we have examples even our own solar system of other places where there are liquids other than water Saturn's moon Titan is covered by seas of liquid methane and ethane right and according to this report no sure it's possible here's my own two cents I tried to think about this like a chemist right and I have to say as a person who likes to believe that he has some imagination I really would love to find an example of life that is very very different from own from our own that's based on some fundamental difference in the chemical principles of how it operates but my own two cents when I think about it as a chemist is that it's not just a liquid we need it's a solvent that we need and a solvent dissolves things and it mediates their interactions and for a number of reasons that fill their own one-hour lecture I actually think that the properties of water or something very like water are critical to the interactions that confer life like chemistry so I actually have become a water chauvinist where I was not before I think that water is important and because that solvent mediates the chemistry of life it kind of constrains what else life could be made of so I have a colleague who went through the exercise of showing in principle that silicon which is everyone's favorite sort of second choice can make a lot of the molecular forms that carbon can however if you put any of that chemistry in liquid water yet either spontaneously combusts or explodes right so it matters very much what the solvent is and those things put together to me suggest that water still is the place to be looking so if we do our job if we build the right kind of telescopes if we find the right places to look someday we may see something like this this is one of these light spectra again wavelength on this axis only it looks different than what I showed you before and it looks cluttered and ugly right there all these error bars which are a measure of how uncertain those measurements are right and we could sort of see some waviness in there but nothing like the sharp Peaks I showed you before right so this is what we can hope to get and actually we can directly improve that picture if we invest in bigger telescopes we actually can resolve that picture better we can collect more photons have more certainty in our measurements so those are choices that we'll have to make will have to decide what wavelengths do we look in right what molecules do we really care about seeing as evidence of life and how big a telescope do we build because the bigger the telescope the farther out we can look and the more worlds will have a chance of investigating for life so these are the choices that lie ahead of us as we think about looking for life and just to wrap this up this is a Hubble Ultra Deep Field image so Hubble stared at a tiny little patch of sky for a long time and everything that you see in this picture is a galaxy every little bit of light that you see in that picture is a galaxy there are 70 billion trillion stars in the observable universe and we know that life has originated around one of them we don't know whether life has originated around any others and there are people working very actively on this question how frequently does life emerge given the right set of conditions it's one of the hardest problems in science and we actually now have the potential to bring observational evidence to bear on that question by looking around us finding the right set of conditions and asking is life there so thank you very much for your attention I hope this was fun and interesting I'll be happy to take any questions so you showed the two plots the one very crisp plot of Earth which showed ozone carbon dioxide and water why was there no oxygen peak in the you know really crisp plot that you showed earlier in the talk and you know you expect to see it in the less well resolved plots from a much further distance yeah so that's a great question if it partly depends where in the wavelength range you are looking because the same molecule will interact differently with different wavelengths of light and one of the reasons is so so part of why the absorption of light happens is that you can imagine a molecule as let's say two atoms on a spring connected and and when they absorb energy what happens is that they start to vibrate so that's where the energy goes into that process happens much more effectively if the two atoms differ in their charge so if one is a little bit negative and one is a little bit positive right that creates a dipole that allows them to absorb that energy and and do this sort of thing so it's actually hard to see oxygen across a lot of the spectrum because it lacks that dipole in exactly that way ozone is much easier to see do we expect to see ozone where oxygen has been produced yes we do we do for for four reasons for the same reasons of photochemistry that we get goes on in our own atmosphere ultraviolet light can break up water molecules into oxygen and hydrogen with the hydrogen light and left to escape the gravity of the planet over you know a long period of time millions and billions of years so how do you tell oxygen produced in this non-biological way from oxygen produced organically yeah that's a great question and actually it's a it's a little bit easier to answer that question with the other main way that you get oxygen so I remember I said that that we have o in the water around us but we also have oh in the co2 around to us right so a lot of what we see on Mars for example the oxygen that we see in the atmosphere comes from that same process you describe the ultraviolet breaking of the molecule into carbon monoxide and oxygen and so if you see a lot of carbon monoxide around as an example that would be a telltale sign that this process has been going on so what you do in order to understand the process is look for look for its residuals so the great thing about chemistry and physics is that they work the same way everywhere right as long as you understand the environment well enough so if you understand the process and how it works and can look for telltale residuals of it like the carbon monoxide for example then you have a potential handle I'm a physicist an electrical engineer but I'm also a cynic could you tell us what is the total budget as everyone involved in this project and once you've told us that tell us whether you think the homeless guy in San Jose cares two hoots whether you have discovered life compared to his life here yeah I think I think that's an important question for us all to ask ourselves you know the the the total budget for the science going forward at the moment is not very much because what we're doing is trying to create the science context around what we will do if we decide that that's an important enough question to address I think that one of the things that makes us who we are as people and as a species is our curiosity about what lies beyond and I think that it's worth pursuing questions just for the sake of that fundamental knowledge that's my personal view on it and not everyone shares it absolutely there are there are differences in the way that we prioritize our spending and I think it's it's important for all of us to consider that so I I think it's a good question and one that's important to have raised when will that sunjae project so actually the the thing you know that you you can always see videos and and think that looks nice you know in the little animation but when is it actually going to happen so actually there is a scale model built at JPL the Jet Propulsion lab out of flight qualified materials and and to flight specifications so they know that they can make it and and they know that it can operate when it actually happens I think it's still a ways off and and typically the way these things work is that there will be smaller scale kind of technology demonstrations but I know that there is an operable scale model that actually exists now and that's I think that's as much as I personally know about it thank you for a good talk two things I hear your part about Europa mission um I heard that Galileo mission had some problems with radiation at Jupiter environment um is there any concern about how the mission might have to change at Europa that's one question I have any others about the Webb infrared Space Telescope and I was wondering about plans in that to use light from covering up the start from transitive star to look for signatures of molecules in the spectrum yeah two very good questions so first the Europa one yes there is a very intense radiation environment at Jupiter it's very high energy electron radiation that wreaks havoc with electronics and even you know even things like glass in optics and stuff like that what's fortunate is that we understand that radiation environment really quite well and and the mission is designed around it and you heard Andy refer to it as a multiple flyby mission so instead of putting something in orbit and just going around and around and around it actually orbits Jupiter and just makes these very brief passes by Europa and that's by design because it spends very little time at Europa it's going fast and it and it moves off to somewhere else in the orbit so the first and best way that you deal with the radiation is to not spend very much time in it and then you find ways to shield and you build with components that you know are radiation heart so the second question about the Webb telescope actually I stalked myself with all kinds of extra stuff here so James Webb Space Telescope is a telescope that will launch in about two years you know fingers crossed hopefully just for scale so the 100 all the way over on the far left is Hubble which is about this size or so Webb is much bigger much bigger and will collect a lot more light have a lot of capabilities and the question was well we actually be able to do some of this work some of this work of investing the the chemistry of the atmospheres by looking when the planet passes in front of its star so if you imagine there's a little ring of atmosphere around it as it moves in front of the star you've got a little bit of light shining through and you see that change the spectrum of the star absolutely that's that's part of what people are looking forward to with the Webb Space Telescope yet I think we'll do that pretty well two objects down to the size of maybe a few Earth radii or so probably not to the earth sized planets that were most interested in that will have to wait on a bigger more capable telescope thank you you showed a chart with something around 1918 exoplanets on it yes are they all from the stars in the Milky Way or if we ever detected a planet outside of our galaxy yeah so I maybe I actually have a slide for that too let's see so this is where so most of those are from Kepler right most of more than half of what we've seen are from Kepler this is where Kepler actually looks so the Sun is in this little spot over here and Kepler's field of view is is quite narrow actually it just looks at a relatively small patch of sky and out about 3,000 light-years or so so everything we know from Kepler comes within this one little patch of this particular arm of the Milky Way that's true for for many of the other methods too there is one method that I don't understand very well it's called gravitational lensing that that for which distance actually doesn't matter all that much I don't think it's discovered anything outside our galaxy so far so I think we really are limited to light that we can see as an individual star and not light that we can see as part of a bigger galaxy so I think we're sort of still thinking locally thank you for your talk and I applaud your ambitions for the Europa mission so my question is two prong one what is our most optimistic scenario with Europa and secondly speaking of optimism my generation is hugely optimistic about the future of space exploration be that in our solar system or outward however we have a much older generation in charge of the Congress and the budget so how do we galvanize the the masses or the senators and congressmen to to share that sense of on curiosity that I assume most of us in this room have yeah so two questions Europa is popular tonight so the the most optimistic scenario for Europa Europa the the multiple flyby mission is designed to assess Europa's habitability not specifically to look for life and it will be an extraordinarily capable mission for me one of the biggest unresolved things about the habitability of Europa so there's very good evidence that there's a huge ocean of salty water beneath the surface of Europa one of the most unresolved problems from my perspective is whether there's any energy that gets in there to be used for life and that really depends on whether that surface ice over turns into the ocean or not and this mission I think really will help us resolve that so we will be able to see the structure of the ice will be able to see sea with with radar the boundary between the the ice sheet and the ocean beneath we will have a very good handle on the chemistry that exists at the surface and and if any of that is a product of the ocean having come up and splashed out on the surface will characterize that quite well so best case most optimistic scenario we will learn a great deal about the habitability of Europa and and a great deal about its it's sort of geophysics besides and maybe we will find some molecules that are tantalizing and and and motivate further study as to the the question of galvanizing support around stuff like this I was having a conversation with with Andy right before the talk so he and some colleagues wrote a textbook in astrobiology and sort of dealing with space sciences about a decade or so ago and we've been revising it just these last few months the amount that's happened in that time is extraordinary that's when Cassini has visited Saturn that's when most of the exoplanets now known have become known that's when we've done most of our driving on the surface of Mars and the mapping of it and all the stuff that I described so I actually think that that quite a lot has happened and and I feel fortunate that there's as much support as there is I think this topic in particular exoplanets has such a great sense of potential at least and there's such excitement within the community that if we can find the right venues to just share that excitement you know not even sort of packaged and marketed excitement but just legitimate excitement I think that's motivation to go and look okay so you mentioned gravitational lensing for a moment there which is like really out there method for detecting exoplanets and technically notes that aren't even orbiting stars is there any similar idea with methodologies that don't include spectrographic data to detect life around other planets is there anything that you're aware of that's really out there for doing that well so so in in what I've discussed I haven't discussed SETI at all of course so so that's I I think of myself as a settle person I would be happy to find life no less intelligent life so that's just subtle exclusive of SETI is there a way to do this that is not spectroscopic so what we get from the star we will not in any of our lifetimes actually physically go and sample right Voyager 1 which is now the most distant object from the Sun left earth when I was in first grade or something like that which is longer ago than I'd care to admit to get to the nearest star to us we'll take another 80,000 years moving at its current 30,000 miles an hour or so so we will not physically go there barring some amazing thing what we get to use as our evidence is light and and what we can say with light we can say best when we break it apart pink floyd style and and see how it is interacted with matter on its path of travel from the star to the planet to us so I I don't perhaps as a failure of my imagination I don't see a way to do it other than that because what we get to deal with is light maybe so my cushy noise why doesn't NASA work with different countries regarding space exploration as does China India Russia maybe you in France working on missions on Mars Europa so if we combine the budgets of all those nations we might be able to find more things yeah that's a good question so I'm I'm not a policy maker for NASA and I don't speak in an official way for NASA I can say that there are many examples of that sort of cooperation so for example the the Curiosity rover has several instruments that are contributed from other nations there are examples the other way around where missions sent for example by ISA or JAXA or other international space agencies have involved instruments built by u.s. scientists or you know or involve those scientists in one way or another so there certainly are examples of that sort of cooperation and collaboration even at the mission level and I agree you know this is sort of a human-scale endeavor not a national scale endeavor and I think it's important to think about how to make that happen okay three more questions talking about methane I believe you mentioned earlier that that would be one of the gases that you would be looking for methane is a very volatile gas of course and needs to be reproduced constantly so methane has been found in the Martian atmosphere but the Curiosity rover has not been able to detect any methane on the ground it's an explanation for that well so so curiosity has seen some very low levels of methane with occasional spikes as it goes along so there there are two observations here one is there are telescopic observations that said there's methane in the atmosphere of Mars and and those have been debated for a long time so there are things you can point to that suggest maybe those aren't real and and people have been looking forward to curiosity to answer that question you know it looks like curiosity has seen some low levels of methane with these spikes but the question actually raises an important point so people used to say used to even a you know less than a decade ago used to say if you saw oxygen and something like methane together that's an absolute smoking gun for life can't happen any other way we see oxygen and methane together on Mars it's really a question of degree because as you said those two things tend to combine and react with one another so so one or the other will hold sway but not both and if you see them both in abundance it means that there's a mechanism for making each of them sufficiently rapidly that that you know that they actually arrives to a detectable level and and that one of the things one of the hallmarks of life is that it does things much more rapidly than would happen in the absence of life so that's something that you would look at and say that's awfully hard to explain any other way why you emphasized search HEPA tight planet or stars like earth sized not something bigger size or smaller smaller sized another question is when NASA will send the mission to Europa by what year what time yeah so I'll answer the second one first if things go as we hope they will go and as they were planned to go it would happen in the early 2020s which which in terms of instrument and mission development timescales is frighteningly close actually so fingers crossed that that happens as to the second one that's a great question actually how does planetary size affect things and I think the honest truth is that that if we are presented with a range of options from which to choose and there's a choice that looks a lot like Earth we always will go for that choice because it's what we understand the best but that doesn't mean that people haven't about your question and and you know tried to provide the scientific context around it so a lot of people think for example that having a way of recycling the planet's crust like we have on earth with plate tectonics might matter a lot we know that can operate on earth on a planet of our size how would it operate on a planet with you know twice that size and and eight times that mass do the geophysics work the same way you know you can add there was a paper you know two papers that came out around the same time and one said of course it works and the other said of course it doesn't you know and and it's things that people are debating if the planet is too small you know does it does it run out of the internal energy to keep that process going and one of the things that's really weird so remember there are these these sort of two bars on the bar graph for planets for which we have no you know comparable example in our solar system we have either small rocky planets that are made out of metal and rock or we have the big gas giants that are you know there are predominantly ice and gas and so forth but nothing in the middle and we have no idea how things would work on these planets except that we know that physics will work the same way everywhere and and we can at least try to model and predict and what becomes very interesting is when you look at the densities of some of those things so the density of our planet is is you know reflects a mix of you know of iron basically and rock the density of Saturn reflects a composition primarily of gas for these things you've got densities quite in between you know that look like maybe some of them are mostly made of water you know a small rocky core and thousands of kilometres of water how would a world like that work right at the pressure of a bottom of an ocean that's thousands of kilometers deep water at any temperature actually becomes a solid and that that changes the dynamics a lot so it's a great question and all I can say is that people are actively pondering it and and we hope that that context will be there when we actually have a choice to make last question um could there have been life on Mars sometime in the far distant past well so that's also a question that we're that we're trying very hard to answer we have the great thing about Mars is that it's because our because it's our next-door neighbor we have been able to send a cadence of spacecraft there every 26 months or so and it's allowed us to design a program that works its way successively toward answering that question so up to the present with the Curiosity rover we've been trying to address the question was Mars habitable in the past or is it now and the answer that question seems to be yes it you know it seems to have been a environment that supported liquid water at the surface in its past it may be an environment that supports liquid water in its subsurface at the present could life have evolved there or originated there those are the conditions that we feel are suitable for life and we have an example here on our own earth of life having originated under such conditions how frequently life arises when the conditions are right we really don't know and so there's another chance just like with the exoplanets to bring observational evidence to bear on that and and there is the potential at least within the next decade maybe to do the sort of science on Mars or on samples returned from Mars that would actually help us address that question

Channel: SVAstronomyLectures

Views: 36,021

Rating: 4.7948718 out of 5

Keywords: astronomy, science, astrophysics, science news, astrobiology, solar system, history of astronomy, exoplanets, search for life in the universe, life in the universe, planetary astronomy

Id: CdSyGpikn5I

Length: 80min 19sec (4819 seconds)

Published: Tue Feb 23 2016