Astronomy Talk: Life in the Universe - The Science of Astrobiology

thank you very much Hilton for that generous introduction and thanks to all of you for coming out on this lovely lovely evening astrobiology to me isn't a field it's a calling as Hilton said when the press conference was held at NASA headquarters in 1996 it was August 7th 1996 I remember the day and there were people on the stage on a stage very much like this one in the auditorium at NASA headquarters saying we think we have found evidence of life in a meteorite that came from Mars I thought wow this is something I really want to be a part of and at that time I had somehow managed never to have taken a biology class I had I had managed to avoid it in high school I had managed to avoid it in college and by the time I got into a graduate program to get my PhD in chemistry of course they didn't care whether or not I knew any biology so as as Hilton says I've started off to learn biology and it wasn't really self-taught I found some wonderful teachers to whom I will be forever grateful and some wonderful courses and programs and I have been a student of biology ever since and I think I will be a student of biology to my dying day so it's really exciting to share this amalgam which astrobiology is it's an amalgam of the biological sciences the astronomical sciences the geological sciences combined with chemistry with physics and frequently with philosophy and ethics and theology as well as you're about to see so thank you all for coming out for this I hear you ask what is astrobiology this is the way I like to characterize astrobiology it's the study of the potential of the universe to harbor life beyond Earth now that is a question the potential of the universe to harbor life beyond Earth that people have asked about and wondered about probably pretty much for as long as there have been people so here's a quote this is a quote from Epicurus he was a Greek who lived around 300 BC and what he wrote is that there are infinite worlds both like and unlike this world of ours we must believe that in all worlds there were living creatures and plants and other things we see in this world a very strikingly modern view modern perspective on the universe there were other perspectives this is a perspective of theologian st. Thomas Aquinas who lived in the 13th century he wrote that when it is said that many worlds are better than one this sort of better does not belong to the intention of God because for the same reason it could be said that if he made - it would be better that there were three and thus ad infinitum Thomas was not a fan of there being virtually an infinite number of worlds but as I'm sure most members of this audience know the number of worlds out there is very very very large and although it is not infinite it is an extraordinarily large number today we are privileged to be able to bring the tools of modern science to bear on these age-old questions the three fundamental scientific questions of astrobiology are how does life begin and evolved does life exist elsewhere in the universe and what is the future of life on Earth and Beyond in order to address those questions we bring together five interconnected areas of science and this slide is basically an outline of the rest of the talk this evening that you'll hear in the next half hour or so we're going to start off speaking about the diversity of life on modern earth then we're going to talk about the four billion year coevolution of life and our planet the earth is four-and-a-half billion years old and life has existed on earth almost since its very beginning so we're going to talk about that coevolution of life in the planet will then go outward and talk about the diversity of solar system environments and let me just say that the reason we start with understanding life on Earth is that in order to understand the potential of the universe to harbor life we really have to understand the one planet which we know for sure harbors life and that planet of course is Earth and we have to understand the nature of life and at least have some theories about how life came to be on the earth and that then informs our study of potentially habitable planets around other stars so we start by understudying the earth and its life then we move out into the solar system to look at the diversity of solar system environments to understand if based on our understanding of life on Earth whether there are habitable environments elsewhere in the solar system to which we can actually send spacecraft then of course we now know that there are planets around most stars and so we also inquire about the planetary environments around other stars and then of course the one of the most fundamental questions we can ask how does a planet go from nonliving to living the origin of life where and how are the raw ingredients for life made and how may that transformation from nonliving to living let's start with the diversity of life on Earth if you study biology a few decades ago and you were studying the diversity of life on Earth you were probably presented some version of this diagram this is the tree of life in the five kingdom perspective so each of these sections of the diagram is a kingdom of life and you were taught that at the base of the Tree of Life is a form of life called minora these are simple single-celled organisms that don't have cell nuclei that don't have compartments in there so then you were taught that the next most complex form of life was also single-celled life but a form called protists that are larger cells typically 25 times larger than the Manar and these are cells that have cell nuclei and they have other compartments in the cells and then you were told that the real diversity of life however was in the so called crown kingdoms of life fungi animals and plants now this perspective on life was developed both by looking at the organisms looking at the microscopic organisms these unicellular organisms under the microscope and then looking at fungi animals and plants frequently with the naked eye and of course one can see there is a tremendous amount of diversity and so when one formulates a perspective on the diversity of life based on what you can see as well as how organisms reproduce you're led to this conclusion that most of the diversity of life is up here at the top of this tree of life among the fungi animals and plants well this is a modern version of the Tree of Life this version is based not on how organisms look or how they reproduce but this is based on their genetic information that is this is based on their genomes this is based on one particular gene that is present in all living organisms and it turns out that all of the fungi animals and plants are all represented by those three twigs on this genetic tree of life we are here movemove that II up to there that's us that little twig which is labeled Homo represents all the animals this little twig right there which is labeled Zeya represents all the plants and this one here labeled copra nice represents all the fungi this domain of life this tree of life shows that there are in fact three domains this domain is called Eukarya all the rest of the Eukarya here those are the protists it turns out that the menorah are everything up here the menorah are actually two distinct domains of life one that we call bacteria and one that we call archaea so the Manar turn out to have the bulk of the genetic diversity of life what a surprise instead of being uninteresting and all the same it turns out that the bulk of the metabolic diversity of life is here in the mana in bacteria and in archaea and it turns out as well that this genetic diversity carries with it a tremendous amount of physiological diversity and metabolic diversity and it is that physiological diversity and metabolic diversity that we find in the bacteria and the Archaea in particular that allows life to inhabit virtually every habitable niche on earth so places that we never thought were habitable are in fact inhabited so for example we thought that the floor of the ocean would be uninhabited there would not be ecosystems on the floor of the ocean because after all everyone knows that the ocean that life requires light and it's dark on the floor of the ocean so there's not gonna be life down there unless something swims down from above in which case it's gonna swim back up well in fact that's not the case I think probably most people in this audience know that there are thriving ecosystems at hydrothermal vents on the sea floor this is a picture from one of them these are tube worms these are typically a metre or two meters long and if this was a larger picture you would be able to see that there are little crabs and shrimp that feed off of the tube worms and they are this ecosystem is powered by energy that is coming out of the earth combined with oxygen that is in seawater the brought down from the surface and we're going to talk more about oxygen in just a little bit this is a picture of grand prismatic spring in Yellowstone National Park there are many such Springs that they are very hot typically the temperature in the center of the spring might be around 90 degrees centigrade which is very close to the boiling point of water some of these Springs are acidic approaching the acidity of battery acid so you have boiling sulfuric acid and the water in the center of these is crystal clear blue it surely looks like it must be sterile and guess what it's not it's teeming with microbial life and again it is this genetic diversity that allows these environments to be inhabited this is a rock from the wall of a dry Valley in Antarctica where it never rains where there is no it there doesn't appear to be any accessible water and these are living organisms microbes right underneath the surface of that rock who managed to extract water just from the atmosphere in these very very dry environments so wherever life can exist on earth it does and it is because of this tremendous amount of genetic diversity that we see I mentioned that the genetic diversity corresponds to a great deal of metabolic diversity and what we have in this diagram is an illustration of how many metabolisms there can be for life so let's just think about our metabolism for a second if you don't photosynthesize does anybody in the audience photosynthesize okay no one photosynthesizes here so what that means is that we need to eat a fuel and we call those fuels reductants and we need to combine our fuel with something that we call an oxidant now us humans and all animals use as our oxidant oxygen which has the chemical formula o - and we see that right over there and our fuel is glucose we eat sugars and we convert starches into sugars and we combine that sugar with oxygen and we breathe out carbon dioxide and water that's our metabolism now the amount of energy that an organism derives from its metabolism is shown by the vertical distance between the fuel or the food on the left and the oxidant on the right so you notice glucose is way up here oxygen is way down here the vertical distance here is almost as large a vertical distance as you can have on this diagram and what that tells you is that we have a very energetic metabolism it produces a lot of energy it's what enables us to grow big and strong there are lots of organisms that use metabolisms that are not quite so energetic so for example one metabolism whoops didn't mean to do that one metabolism that is very common is and metabolism that it particularly may have been very common on early Earth as a metabolism where hydrogen is the fuel and carbon dioxide is the oxidant and there are organisms that use that combination and they produce methane they're called methanogens and there are lots and lots of methanogens in this room with us anybody know where in our guts exactly so again this just illustrates how many environmental niches there are for organisms with different kinds of metabolisms and in fact if you take any fuel on the left-hand side of this diagram and any oxidant on the right-hand side of this diagram if the arrow connecting them goes down to the right then there is an organism someplace on this planet uses that metabolism so that shows you the range of metabolisms that are available to organisms and that is really central to enabling organisms particularly microbes because the we are largely talking about microbial metabolisms here this is what enables so many of these environmental niches including our guts as an example to be inhabited by microorganisms so let me move on now to the coevolution of life and the planet what you are looking at here are pictures of rocks that are 3 and 1/2 billion years old now the earth is four-and-a-half billion years old these are among the oldest rocks on the planet these are rocks in Western Australia in a region called the Pilbara and take a look at these structures in the rocks there is a pocketknife for scale this structure is a couple of feet high maybe two and a half three feet high there's two of them they grade gradually into this larger dome here you see another structure not quite the same shape rather more conical these are fossilized microbial communities these were photosynthesizing communities of microbes that grew up word toward the sunlight this is why they have this domed shape and this conical shape because they were trying to grow upward to to get the light these have been studied in great great detail and we're quite certain that they are in fact evidence of rather thriving microbial communities three and a half billion years ago now one of the things that helps us appreciate that these are in fact evidence of biology is that we can see the same kinds of communities alive today this is also a picture from Western Australia this is from Shark Bay this is just a few hundred kilometers away from the Pilbara where this was taken just look at the similarity here this is two and a half three feet high that's also about two and a half three feet high just about the same size and in fact we believe that this is a modern version of that life has existed for a long time at least three and a half billion years we think life may be older than four billion years one of the early forms of life but by no means the earliest are these organisms this is of course a picture of modern cyanobacteria taken in a laboratory but these organisms were around on earth at least two and a half to three billion years ago possibly even longer possibly as much as three-and-a-half billion years ago and these are tremendously important organisms they photosynthesize but the most important thing is that they were the first oxygenic photosynthesis these were the very first oxygen producers on our planet now the production of oxygen has been a profoundly important aspect of the history of Earth all of the oxygen and Earth's atmosphere is the result of life and oxygen wasn't around on earth until these organisms evolved these are rather complicated photosynthesizers there were simpler photosynthesizers that didn't produce oxygen hundreds of millions of years before cyanobacteria came along so one of the things that we can look at is we can look at the history of oxygen on earth and this is a very simplistic perspective on that this side of the graph P stands for pressure and so this is the pressure of oxygen in units of the current atmospheric pressure on earth so atmospheric pressure on earth is one atmosphere by definition and 20% of our atmosphere is oxygen so this is the modern level of oxygen on earth and this is a scale in which each unit goes down by a factor of 10 so prior to the development of cyanobacteria there was zero oxygen it was all the way down and then at some point and in this particular graph it suggested that it was maybe 3.2 billion years ago cyanobacteria evolved they started generating oxygen but oxygen didn't immediately start filling up the atmosphere there was a lot of reduced material remember what was on the left hand side of that metabolism diagram that we called reductants there was a lot of that kind of stuff around and that just eats up oxygen chemically so there was a lot of reduced iron in the oceans for example and that reduced iron just soaked up this oxygen and in fact it made in the process the iron ores that we utilize today in fact in a way you can say that cyanobacteria were responsible for the industrial age because they provided the oxygen that led to the deposition of the ores that we mined today as the primary sources of iron well after the all of those reductants got soaked up or soaked up the oxygen then finally oxygen rose again something on the order of two to two and a half billion years ago we think it was about 2.4 billion years ago and it rose up perhaps to modern levels perhaps it dipped down again but the point is that the oxygen that we see today on earth was not always there now this is really important when we talk about exoplanets because you will frequently hear people when they're speaking about exoplanets say well if we can find oxygen on an exoplanet that means that there must be life because we know that all the oxygen and Earth's atmosphere was produced by life and therefore if we see oxygen on an exoplanets atmosphere well there's a good chance that it was produced by life well that's an OK argument except that if you had observed earth if you were an astronomer on that exoplanet looking back at Earth three billion years ago or three and a half billion years ago you wouldn't have seen any oxygen how could you have told that there was life on Earth so when we look at exoplanets now we have to think very carefully about what kinds of characteristics would tell us that there was life on that exoplanet because Earth has had many different characteristics over the course of its history the abundance of oxygen in the atmosphere is just one of those and there are many others the diversity of solar system environments and I'm going to talk about four objects in particular I'm going to talk about Mars I'm going to talk about Europa a moon of Jupiter and I'm going to talk about two moons of Saturn Titan and Enceladus so here's a picture of Mars this is one of many pictures it was sort of a random picture I took it I chose it because it's just visually so striking but what it shows you is that shows you the remarkable complexity of the geology of Mars you see many many layers you see a tremendous amount of erosion a very very complicated geological history one of the things we've known about Mars for many years actually since the first missions to Mars in the late 1960s and the early 1970s is that there has been a great deal of water flowing on Mars at least in the distant past here is an example this one happens to be taken from a spacecraft that eisa flew to Mars called Mars Express ISA as the European Space Agency and this one shows channels these are channels that were almost surely carved by flowing water flowing downhill into this lower area you can see an area here where the support in the ground seems to have been removed and we think what happened here is there was subsurface ice melting occurred the ground collapsed the ice melted and water flowed out in a chance into this lower region and you can see evidence of many other channels and this is something we've known about Mars for many years starting in the 2000s we had a series of Landers on Mars this is just one of those the Opportunity rover that landed on Mars in 2004 this is the opportunity Rover just having rolled off the landing system that delivered it to Mars this landing system used airbags you can actually see the airbags if you look carefully they are retracted and folded under and you can actually see the bounce marks because this was surrounded by airbags when it landed and those airbags deflated after landing you can actually see the bounce marks there where the spacecraft bounced before depositing the Opportunity rover on the surface of Mars and we sent the opportunity Rover to a landing site that we saw from orbit showed evidence that there were minerals that were formed in water and sure enough when we looked at the landing site what we found are these small blueberry sized spheres which we call blueberries although they're made out of rock they're made out of an iron ore called hematite and these are in fact examples of the kind of rock that gets formed in water and these rock these blueberries are embedded in this rock and as this rock erodes these blueberries basically fall out of the rock and this happens to be a little depression which the team that was running the rover called the blueberry Bowl now we sent other Landers to Mars this is the Phoenix lander the image taken by a camera on an arm of the Phoenix lander looking under the lander now unlike the opportunity Rover the Phoenix lander was sent to high latitudes close to the North Pole of Mars and it used retro rockets rather than airbags as its landing mechanism so this was more of the classical Lander that you expect that fires a retro rocket and then lands on legs but when you fire a retro rocket one of the things that you do is you blow away some of the surface immediately underneath the spacecraft where you're landing so the retro rockets from the Phoenix lander blew away a few inches of Martian dust and look what it exposed ice right underneath the surface this is just one of many pieces of evidence that there is lots and lots of water on Mars today most of it frozen but not all of it frozen and here's an example of water that's not frozen and was there on Mars and is probably still there on Mars these are the struts the legs of the Phoenix lander and look at these droplets the way those droplets formed we believe is that there is a salt in the surface of Mars it happens to be a salt which bears a chemical resemblance to common table salt sodium chloride this is not a chloride but it's a perchlorate it's got chlorine in it but chlorines combined with oxygen and that salt like table salt absorbs water very very readily but perchlorate really absorbs water so even though there is very little water in the Martian atmosphere there was ice right underneath the lander there was some water vapor in the atmosphere even though it's very cold and that salt absorbed enough water vapor out of the atmosphere to form liquid water droplets on the struts of the lander so not all the water on Mars is frozen and there's other evidence that there may be at least small amounts of liquid water relatively close to the surface in certain areas that get heated by the Sun the most reefs Lander that we've landed on Mars is the Curiosity rover that landed on Mars in 2012 it's taken a number of selfies we sent it with a selfie stick it's got a long arm with the camera on the end of it so you don't see the selfie stick here the selfie stick seriously of course is an arm that carries several scientific instruments and it enables the rover to place these scientific instruments up against rocks to do very detailed analyses but it can also take a picture of the rover itself which it has done here and one of the very first things that the curiosity mission discovered at its landing site which we thought was a place where there had been water at least in Mars distant past a place called Gale Crater that spelled GA le and sure enough one of the very first things that the Curiosity rover found were stream deposits and the way that we know this is a stream deposit is that it's a conglomerate of rocks this isn't a solid rock this isn't a piece of bedrock this is more like a piece of cement where you have lots and lots of little pebbles that have all gradually gotten cemented together just by the natural processes of being exposed to weather and in fact this and other information that it's been gathered from the Curiosity rover tells us that it probably landed in an ancient lake bed in the toward the edge of Gale Crater and it was a lake bed that was fed by some streams that were coming off a central mountain that I'll show you in just a second called Mount sharp and coming off the walls of the crater flowing down into the crater at a time when there was much more liquid water on Mars than there is today curiosity was sent to Gale Crater because in the center of Gale Crater is this mountain called Mount sharp Mount sharp is roughly the same size as Mauna Kea measured from sea level not from the floor of the ocean is a large mountain and curiosity is in the process of climbing up into the lower reaches of this mountain it's going up toward this side and moving up in that direction and as it goes up it is studying the rocks to understand what was the history of water in this part of Mars because the lower regions of the mountain are of course the older regions and as you go up you go to successively younger regions and so the mountain serves as something of a time machine and as curiosity climbs up the mountain and studies rocks at different levels on the mountain we will be learning about different periods in Mars history this is a picture I just like to include just because I just find this picture it's so powerful it makes you feel makes me feel that I'm standing there on Mars that is the wall of Gale Crater this is a sand dune we're looking at the downwind face of a sand dune this is the kind of terrain that the Curiosity rover is traveling over we try very hard not to drive the Curiosity rover into a sand dune because that would not be good but in fact we can get it up really close as you can see so and this is just part of a 360 degree panorama you can find this the image from which I took this and many many other images from curiosity and the other missions on the web so they're not too hard to find typing Mars images into Google will be a good start or just typing in Curiosity rover mission further out in the solar system to Europa moon of Jupiter if you looked at Europa with your naked eye it would look something like this it would almost look like a cue ball in a in a billiard set if you enhance the resolution if you enhance the trust a little bit you would find that it looked a little bit more like this and you would see that there were modelled areas you would also see that there were some linear areas this is an object roughly the size of Earth's moon so this is not a small object and if you look at the surface more closely in fact it was my PhD thesis back in 1972 that told us that all of this white material is frozen water that's water ice and when we look at the surface more closely and this was from the Galileo spacecraft in the late 1990s we find that the surface particularly those modeled areas are areas in which the icy surface appears to have been heated and broken up and you can see that chunks of ice have sort of drifted off and because one of the things that is very common on the surface are these ridges which are frequently double ridges you can actually sort of put the pieces back together so for example that double Ridge was once connected to that double Ridge but it separated and this piece of ice floated off if you're having any trouble seeing the topography here this face is facing the Sun and there's the shadow so the Sun is coming in from the right and there is the shadow of this particular piece of ice sticking up this is sticking up perhaps a hundred metres and this is perhaps a kilometer or two kilometers across what we think is going on here is that there is a relatively thin frozen ice covering and there is a liquid water ocean under that ice covering a hundred kilometres 60 miles deep there is as much water in this global ocean on Europa we believe as there is in all of Earth's oceans combined what a fascinating place wouldn't you like to get into that ocean and find out if there's anything swimming I sure would let me move on to Saturn this is Titan a moon of Saturn it's covered by a photochemical smaug sort of what I used to see when I was observing a Mount Wilson which looks down on Los Angeles in the 1970s and I looked down during the day and what I saw was something that looked very much like Titan and not until the sunset did I start seeing the the streets because the photochemical smog at that time was was very great but we can see through haze of Titan with radar and we've done this with the Cassini spacecraft and what we have found is that there are lakes and rivers on Titan this is not a radar image this is actually an image taken directly by the Huygens probe which was carried to Titan by the NASA Cassini spacecraft the Huygens probe was built by the European Space Agency and this is an image showing River channels on Titan with the evidence of rain and in fact we know that there are storms on Titan and those storms involve rain with rivers that then flow down and fill up lakes and small seas however the liquid is not water it's way way too cold for water does anybody know what that liquid is liquid methane exactly we have methane seas methane lakes methane rivers and methane rain on Titan now one of the questions I sometimes get asked after a talk like this is well we are always talking about water and looking for water as signs of life could life exist in some other solvent well the answer is yes life could exist in other solvents and one can have some interesting speculation about whether or not there could be life in methane as a solvent and one mission proposal is to land on one of the methane lakes on Titan and investigate what's in that lake and see is there perhaps evidence of life in methane lakes on Titan and this is a picture that was not supposed to ever be taken this is a picture from the Huygens Lander ash it landed on the surface of Titan it wasn't supposed to work after it landed on the surface it was being lowered on a parachute but it was designed to function only while it was descending on the parachute and here we have a picture of rocks in the foreground these rocks are made of water ice on a surface which in fact is a surface that has probably been wetted by methane although it's a little bit hard to tell whether it was wet with methane at the time that Huygens touched down on it another moon of Saturn a much smaller moon called Enceladus and Enceladus is another moon that we have learned has a subsurface ocean and an icy surface but on Enceladus the ocean is in part escaping into space there are jets coming out of the south polar region of Enceladus we have been able to study these Jets from the Cassini mission we've been able to actually fly through the Jets and measure their composition we know that the Jets are mainly composed of water but there are salts in the Jets there are also organic compounds in the Jets and there is evidence of the kind of interaction of water and rock that we think might have helped life get started on earth four billion years ago and there is evidence of some of that same chemistry going on on Enceladus and there are some people who think that Enceladus may be one of the most likely candidates in the solar system for a body that might Harbor life in an ocean beneath its frozen surface let me move on now to planets around other stars the first planets around other stars were detected in 1995-96 and as Hilton mentioned were part of my inspiration for going into astrobiology and the Keck Observatory has been absolutely fundamental in these discoveries particularly in discovering planets by the Doppler method in the Doppler method and in both methods of detecting planets that I will speak about and I think people in this audience know about you don't actually see the planet planet is unseen but what you see is the gravitational effect that the planet has on the parent star as the planet moves around the star the star actually also moves and we can see the star moving alternately toward the observer on earth and away from the observer we call this a blue shift we call this a red shift we can actually detect that this is a sample spectrum taken with one of the instruments at the Keck Observatory the high-res instrument and it is by this means that hundreds of planets around other stars were discovered and hundreds of them from the Keck Observatory the other method is the transit method and I know you've heard about that recently as well this is the method that one can take advantage of when the orbit of a planet is aligned so that the planet as it goes around its parent star passes in between the star and you the observer when it does that as shown in this artist's conception it blocks out a little bit of the light this can be done from the ground but in order to detect earth sized planets this way which block out only one part in 10,000 of the light from the planet so you have to detect a dimming of the star excuse me light from the star you have to detect a dimming of the light from the star of one part in 10,000 that's really small you need to go into space to do that the Kepler mission is doing that and the Kepler mission has discovered thousands of planet candidates most of which are real planets but frequently you need ground-based observations to confirm that something that Kepler identifies as a potential planet is and much of those ground-based observations are also done on Mauna Kea and particularly at the Keck Observatory what we are really interested in and what Kepler in particular is focused on is finding planets in the habitable zone of their parent stars the habitable zone is defined as the distance from a star at which liquid water would be stable on the surface so it's sort of the Goldilocks zone if you're too close to your star it's too hot if you're too far away from your star it's too cold but in this green region liquid water could potentially exist and of course the habitable zone is at a different size depending upon whether you're looking at a really hot star or a star like the Sun or a really cool star like the red M dwarfs that I'm sure you have heard about so Kepler is particularly focused on finding planets in the habitable zones and the observatories on Mauna Kea in particularly including Keck have played an important role in following up in those observations and today we know that someplace between a fifth and a quarter of all sun-like stars have an earth-sized planet in their habitable zone and this is an estimate of course because we're just beginning to discover these but what we are learning is that earth sized planets potentially rocky planets appear to be common most stars are at least something on the order of 20% of sun-like stars and perhaps even larger percentages of other types of stars have may have planets that are roughly earth size and could potentially be habitable a the last of these topics is the origin of life I'll say just a few words about this one could talk about the origin of life for a long time it is one of the great mysteries of the universe one possibility that we are aware of is that the raw materials of life may have come from space when we use telescopes such as the telescope's of Mauna Kea particularly the radio telescopes and look for example at interstellar clouds we find evidence of the molecules that ultimately are important for life we then also can study meteorites and that is samples of interstellar material that coalesced into solid bodies around forming stars and eventually fell to the surface of the this is a meteorite that fell to earth in 1969 in Australia and near a town called Murchison so it's called the Murchison meteorite it's a kind of meteorite we call a carbonaceous chondrite because it's got carbonaceous material in it and it turns out that that carbonaceous material includes amino acids and nucleic acids amino acids are what make up our proteins nucleic acids are what make up our DNA so some of the raw ingredients for life are being made in interstellar space and in circumstellar space in planetary systems as they are forming and that material is being delivered to earth today and it was being delivered to earth and much greater abundance four billion years ago when there was a lot more of this debris leftover so earth may have been seeded with the raw materials that it needs for life possibly from space the raw materials for life can also be made at hydrothermal vents and we have experiments that we're doing in the laboratory to show how some of the raw ingredients for life can be made and even how chemical systems can develop at hydrothermal vents that emulate cells that actually emulate in in small compartments in the minerals that form that actually emulate a primitive cell even though it is strictly a geochemical phenomenon at a hydrothermal vent so we think that life could have arisen deep deep in the ocean at a hydrothermal vent or perhaps life could have arisen back at the surface but in a tidepool one of the problems in the origin of life is that many of the molecules that we need for life are formed as polymers that is there are individuals smaller molecules that we call monomers and they have to link up together to form a polymer well when you link up monomers to form a polymer commonly what happens is a water molecule is extracted from those two monomers in order to join them well it's very hard to extract that water molecule when you're bathed in water as you are in an ocean so one of the things that helps is if you can dry out some time because as you dry out the environmental water goes away and it becomes easier to form those polymers and sometimes the rocks that you are that the molecules are resting on and attached to are clays that are formed by the action of water on rock and those clays can be catalysts for the formation of those polymers and so a tide pool and this is a tide pool in portugal today but tide pools which get wet at high tide and then dry out at low tide as the Sun shines on them and then get wet again at the next high tide they may have played an important role in the origin of life so we don't know for sure how life began on earth but we have a lot of theories so I'd like to just finish up with the question how would we recognize alien life if we found it now it would be really nice of course to have a tricorder and to have bones there and Jim and you know Jim could ask bones well bones is that a life it's that a life form and and bones could say yes Jim that is definitely alive see this reading here on our tricorder well of course we don't have a tricorder now there is also the Supreme Court theory for life and that is we'll know it when we see it let me close this talk with another possibility let's just think about the types of molecules that life uses again the only life that we really can say things about definitively is life on Earth so let's just start with life on Earth and let's just sort of generically think about the type of molecule well we know that life uses several types of molecules we know life uses sugar glucose is an important one we use some other sugars we can eat fructose we can eat sucrose so there are few other sugars we have a particular sugar in our DNA called ribose which is a different kind of sugar but it's important for us we use amino acids and our proteins we use nucleic acids in our genetic material but those are very specific types of molecules and we use very specific versions of those molecules so we can think of a biological distribution of molecules as being spiky we would have you know a few different kinds of sugars a few different kinds of nucleic acids a few different kinds of amino acids so it would be a spiky distribution so if in some sense we plotted the abundance of different types of molecules and this is just the relative number of those molecules of the relative abundance we would find a spiky distribution abiotic processes in comparison tend to produce relatively smooth distributions that is they'll produce all kinds of amino acids all kinds of sugars all kinds of nucleic acids not just the kinds that we use but let us say that we went to Mars or any other planet where we could access material and we looked for molecules without any presuppositions and we found a spiky distribution of molecules but it was a different spiky distribution than the spiky distribution for Earth life we might think that that's a clue that there might be biology at work and we should look deeper into that question and with that I would be happy to answer any of your questions

Channel: W. M. Keck Observatory

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Id: oY2itQu5hnI

Length: 52min 4sec (3124 seconds)

Published: Wed Apr 06 2016