welcome to the science for the public lecture series science for the public is an organization committed to bringing science information and issues to the general public visit our website for our program listings and blog good evening i'm yvonne step for science for the public and i welcome you to tonight's contemporary science program looking for signatures of life on mars to explain how that search is conducted we have roger summons professor of geobiology at the massachusetts institute of technology and a participating science in the nasa mars science laboratory mission roger summons received his phd in chemistry from the university of wollongong in australia and before joining mit in two thousand and one he held appointments at stanford australian iron and steel the australian national university and geoscience australia in a remarkable career he's developed analytical techniques and made discoveries that are today essentials in the field of geobiology along the way he's received many prestigious awards his distinctions include an appointment as a fellow of the royal society dr summons is particularly known for his investigations of biological traces in very ancient earth sediments and oil shale his contributions to the identification of earliest life on our own planet are now applied to the analysis of sediments on mars tonight dr summons explains how organic matter leaves its signature in the form of biomarkers and how that information can be decoded millions or billions of years later we are very honored to welcome roger summons thank you welcome sir thanks very much and i'd like to ask to start with what's geobiology what do you do geobiology is the study of how life on this planet has coevolved with the planet we know that earth has changed over geological time over the four and a half billion years that it's existed and a lot of the changes that we know took place on the surface of the earth being driven by life and for most of earths history that life was entirely microbial yeah that is growing slime yeah yeah microscopic organisms have dominated the planet for most of its history and are you saying that the geology wouldn't have developed in the same way if it had not been for biology and maybe vice versa exactly exactly okay all right one of the most profound changes that people recognize is that the earth was formed with no oxygen in the atmosphere yeah and now we have an atmosphere with twenty one oxygen and we know that oxygen was formed by the photosynthetic organisms that we can see around us but mostly from the cyanobacteria in the ocean they were the first they were the organisms that invented the ability to do photosynthesis yeah and produce oxygen at the same time right and that oxygen has determined how the way rocks have weathered it's determined the minerals that we can find in rocks so there's very definite evidence that the activities of microbes have profoundly affected the surface environment and probably the subsurface environment as well when we see say documentaries or books about fossils we see these things sometimes very problematic little fragments and so on and it is your field and you substantially who developed other ways to trace this early life you've worked on oil and coal and oil shale yeah and things where we don't think we see fossils could you please tell us about it well the fossil fuel that we're burning to power our cars and our homes is organic matter it's organic carbon compounds that have been formed in the past by living organisms all the organic matter practically all the organic matter we have on the planet is a consequence of the activity of life um hm so you look at a piece of coal and it's a piece of black stuff yes you look at black liquid yeah coming out of an oil well it's black stuff right but really it's individual molecules it's individual compounds that we can use chemistry to determine the structures of those molecules and the structure of those molecules are clearly related to the different organisms that have made the molecules and those organisms are doing making their living in different ways so the structure of a single compound can tell you an awful lot about the organism that made it and the process that organism was using to make a living whether it was photosynthesis or it was eating something else or eating somebody else molecules have a story to tell and that's what i've been very fortunate to be able to work on for the you know the last forty years of my career so it's this combination of chemistry and biology and i don't know what else and geology exactly all of that together but again i think most of us are just not aware that you could look at oil and coal and find a history like this and so you do this sort of chemically with looking for markers is that the idea of tracing we use a technique called gas chromatography combined with mass spectrometry and to explain that a bit more gas chromatography is a way to you can separate molecules with incredibly high resolution so you can separate molecules that only have very very subtle differences in chemical structure and the mass spectrometry part is an approach to getting a fingerprint of those molecules and we can compare that fingerprint with molecules that we can make in the laboratory or molecules that you can buy off the shelf from somebody so it's a lot of comparison sometimes we find molecules in rocks that we've never seen before and in that case we have to do a lot of chemical experiments um hm to determine the structure once we've determined the structure then we have that sort of a chain of connections that we can make to through biochemistry basically um hm to the organisms that made those compounds when the rover drills a hole in a rock or in the soil in mars you can really look at this you don't have to see the fragments in a rock these that's we are usually shown with fossils when we think of fossils yeah so the best way to think about the msl mission i think is think of it as a geologist a robotic geologist yes on wheels yes and the msl or the curiosity rover has a whole suite of tools that a geologist would normally have it for example has a hand lens yes and the hand lens produces beautiful photographs it's just this most spectacular instrument takes little selfies takes selfies and takes mosaics it's a brilliant brilliant camera yah yah and were there microscopic organisms on mars that hand lens would be able to see them i mean they would need to be a certain size before it could resolve them from the rest of the rock but it with a hand lens you could see your you know a moderately sized small fossil if they existed that's amazing well i've got a cartoon of the rover and the cartoon explains that what the primary mission is the primary mission is not about detecting life ah the primary mission is about determining whether life could have existed in the past at some place on mars we can't explore the whole of mars obviously it's very very difficult right right but there was a very detailed selection process that chose a place where they thought they knew a significant amount of the geology uh huh there's no point going to a place where you have no context yes because in this sort right right of work context is everything so a lot of selection went on to choose a place where they thought they would have rocks that could preserve life signatures had they had they been formed at the time right i see and as a consequence they chose gale crater okay as the landing site all right and within gale crater then the tasks that curiosity was charged to perform curiosity and of course the team of scientists that runs the mission is to evaluate the biological potential of that place to understand the geology and geochemistry and their interrelationships particularly to try to understand the role of water in that particular environment hm hm and because life is profoundly affected by radiation yes both beneficially and deleteriously if we get too much solar radiation it's not good so evaluating potential for life to exist really depends on understanding the entire environment including the radiation environment okay so that's the mission yes not to detect life but to see if life could have existed okay this is the another cartoon of curiosity and it's got the various instruments labeled such as mask cam kim cam marty these are all imaging systems yeah yeah i think there's altogether nine cameras so the mask cam takes big images it's stereoscopic and color images uh huh there are hazard cameras that on the wheels that the rover drivers can use to evaluate danger like that yes and it also shows the instruments that are inside the rover the main chemistry instruments there are two of them one of them was called sam yes sam for analysis on mars and that's the experiment that i was selected to work on okay and then another one called kimin which is an xray instrument that can determine the minerals that are present and the minerals that are present give you a lot of context so if you get the information about what minerals quartz olivine carbon eight those sorts of things it helps you evaluate the information that you're gonna get from sam sam collects data on soil samples on sediment that would be drilled by the drill sam also has the capability of looking at the gasses in the atmosphere the gasses in the atmosphere comprise carbon dioxide um hm water vapor a little bit of oxygen argon some nitrogen and those gases and their isotopic compositions can tell you an awful lot about the history of the atmosphere so the mission is not just about looking for organic molecules um hm umhm but evaluating the context of the samples that we're analyzing okay it's an ongoing evaluation process uh huh they're using data that's collected by the rover itself they're also using data imagery from satellites that are orbiting mars and taking high resolution images of the surface of the planet i see so it's a combination of information on the ground using the cameras and information from above using the satellites ah right to place the rover in a position where they might find an interesting rock and it's not no point in looking at any old rock when you're interested in those rocks that best preserve organic matter uh huh and on earth the typical place we would look would be in a shale that is a very fine grain sedimentary rock we don't find organic matter typically in a basalt ah or granite or an igneous rock i see and we don't find it in a sand stone because the grains are so big anything that was in there would leak out it's very fine muddy silty sediments that best preserve organic matter also laminated sediments layered sediments that have been put down over a period of time if the cameras can show us a layered sediment that's another indication that the sediment was deposited underwater yeah it's one of the main factors that we look for on earth to find organic matter whether we're doing it to find coal or oil or whatever it's no use looking in sand in the sahara desert yeah that's exposed to the atmosphere that wasn't deposited underwater we're looking for fine grain sediments deposited under water that stayed or had low concentrations of oxygen if you got a lot of oxygen in the environment organic matter is good food for bacteria so it would be consumed eaten oxidized it would ultimately disappear so we're looking for places where organic carbon and other signals are preserved it's called the science of taphonomy it's a long word taphonomy hu taphonomy is understanding all the processes that lead to the preservation of a fossil whether it's a molecule or a microbe or a bone or a human skull taphonomy is the science of understanding where best to look for wellpreserved material look at that and we apply the science of taphonomy to looking for the ideal places on mars where something useful i see i see or interesting might be preserved so there's an ongoing process every day members of the science team are looking at the images evaluating where the rover is evaluating targets to look at in the future and then they develop a list of priorities um hm those priorities are uploaded to curiosity and it goes through its steps doing the experiments one after the other the designs team have determined is going to optimize the data that they're going to get down so it's ongoing well when their mission first started it was twenty four hours a day yeah now they've gone down to five days a week oh i see twelve hours a day a couple of days off for the a couple of days off for curiosity yes and for the scientists yes yes i guess so you have written about the difficulty i think you just mentioned it also on a planet like mars radiation is a really serious destroyer so how do you get around that and first of all i think you mentioned there's not really an atmosphere like we think of atmosphere now so it would be worse it's an atmosphere that's very thin aha and earth has an atmosphere we call seven yeah one atmosphere mars has an atmosphere about one of earths atmosphere ah right yeah yeah so for every hundred molecules in earth's atmosphere there's one molecule on mars and that atmosphere is not dense enough to stop or to inhibit the radiation okay and consequently the surface of mars is getting a full dose of solar radiation right so even though mars is a little bit further away from the sun than earth yeah that radiation is not stopped by the atmosphere okay so that's one thing so that you would have to go internally so you pick a rock and you know you have to dig for this correct yes when you get the samples and the project is sending you the data sending this enormous team of people all this data you have the machines in your lab to do i think you said analog yeah kinds of experiments could you tell us so here's some data that looks interesting yes it's part of the whole the process of groundtruthing ground truth truthing ground truth yes and you know all science relies on ground truth you have hypothesis yes you do an experiment and then you query that experiment you try to find fault with it your job is to disprove yourself and so there are many people on the sam team doing these experiments daily not just at mit but there's a large group of people at the goddard space flight center in greenbelt maryland there's people in houston johnson space center all doing analog experiments and testing various aspects of the results that are coming down um hm and one of the things we do is make a mineral or a mixture of minerals that we call an analog soil for example um hm or an analog sediment we take the information that we've got from the rover about the mineral composition and we make a similar mixture in our lab uh hm and we run the experiment as close as we can to the way it's been run on mars and it's those experiments then determine or inform how the experiment might be done on mars better than it was last time so for any rock that we look at on mars we might look at it do six or seven experiments based on a combination of the results that came from mars but also the results that came from earth there's actually a sam instrument testbed instrument that it's operating under mars atmospheric conditions in a chamber at goddard space flight center oh and that's the main place where analog experiments are done i see i see using an instrument that's almost identical to the one that was flown and that way they can test the software they can test many many more aspects of how the experiment works and check them for truth yeah and it's a constant backwards and forwards of experiment on mars some experiments on earth redo the ones on mars redo the ones on earth and you're finessing your understanding right i understand right and obviously a lot of crosschecking among the scientists themselves correct yes so that's one of the most interesting things that i read about your work with looking at fossil life is that dna and other proteins don't preserve well and certainly would not do on mars yes then you look at lipids can you tell us about this and what's lipid what's lipid this picture shows some chemicals that we might find on mars okay um hm and on the top row um hm are very very simple molecules acetic acid vinegar uh hm there's a straight chain hydrocarbon simple hydrocarbon that you might find in gasoline for example and then the compounds with the rings called poly aromatic hydrocarbons and those sorts of molecules can be made by all sorts of processes not necessarily involving biology okay they are formed through biological activity but they're not diagnostic for i see biological activity i see we find those molecules for example in meteorites that land yeah on the earth or in interplanetary dust it's always landing on the earth so they're not particularly informative about the processes that made them mm mm now the second row of molecules uh hm are typical of the structures that are formed by biology and on the left we have amino acids mm mm and the one shown there is alanine so it's part of our proteins for example of that twenty that make up life here on earth is it's one of the twenty okay has another feature to it and that is a handedness aha what we call homochirality yeah and all the amino acids have the same configuration that's a very very different thing to the sort of nondescript or not that that's a bad word but less informative characteristics to the molecules on the top row aha the molecules on the bottom row have structural complexity that can only be imparted by biology okay and the molecule on the right large complex molecules with threedimensional qualities and the one i'm showing there is cholesterol yaha and we wouldn't be here without cholesterol yes cholesterol is essential to making our membranes work it's a very complex molecule and it's made by a complex series of reactions in our cells in biochemical or biosynthetic reactions and this is a lipid as opposed to the protein is that correct yeah the molecules on the left are amino acids because they have the chemistry makes those amino acids rather unstable over billion year timescales aha stable over our lifetime yes and we could find them in fossil humans right from olduvai gorge for example places where people looking for early hominids they are stable over that sort of timescale but they're not stable over billion year timescales which is what we're looking at in mars because gale crater we think was formed about three and a half billion years ago three thousand five hundred million that's a lot different to a human timescale yes but also that would be true for earth when you were looking back three billion years on earth at what you hope are fossils or something you are you emphasize the these lipids as opposed to the protein right the protein i just need to understand doesn't last so well protein dna sugars right okay nucleotides all of those sorts of molecules right they're unstable for several reasons there's a chemical reason ah that they have what we call functional groups that are easily attacked by bacteria but they're also good to eat because they have nitrogen and phosphorus yeah they have elements in them that microbes like to eat so if we've found an amino acid in a very old rock you'd have to be really suspicious why didn't someone eat it in the that have gone on i see but it's much much more difficult to eat a molecule like cholesterol wow i often use the example that when we're dead and buried and we sit in a coffin for i don't know a couple of hundred years most of our biomass will have been consumed the thing of us or the part of us that's the most recalcitrant type of material are our lipids so our cholesterol is going to last a lot longer than we do that is quite interesting yeah and so therefore that's what you're looking for we're looking for molecules that are very difficult right right for organisms other organisms to eat but they would still clearly signify biological or i don't know if prebiotic but something along those lines right they would preserve the qualities that we associate with okay all right all right that is quite interesting has that gone on for a long time and the rest of us just don't know it that you've known this about fossil residuals anywhere the field really took off well it was started in the forties and fifties in a little way yeah a gentleman by the name of alfred tribes identified a molecule in rock that he could relate to chlorophyll and of course chlorophyll we wouldn't be here without chlorophyll yes right right and identifying a molecule it's called a porphyrin which has got the center of a chlorophyll or that's found in the center of a chlorophyll i see clearly tells you that the organic matter had something to do with biology and then for the next fifty years people explored that idea in greater and greater detail and you can ultimately show that every molecule in every drop of oil on this planet was formed by life at some time in the past not only that the type of life on earth has evolved over time yeah we started out with mostly bacteria those bacteria or parts of them were incorporated in more complex organisms to form algae yeah those algae evolved into more complex organisms we call plants and that process of evolution can be traced in oil the composition of oil has also changed over geological time corresponding to the way the plankton in the ocean has changed over geological time so so it's a very faithful marker of the evolutionary process yeah and it's totally complimentary to the fossil record the visible fossil record yeah and the micro fossil record yeah so we have colleagues who study microscopic organisms in sediments and they can see the evolution in plankton through time yeah yeah and just the same as they see rocks dominated by cyanobacteria for example and later at some later time rocks with green algae and then at some later time more complex algae like diatoms yeah uh huh and dinoflagellates you can see those transitions in the fossil record but you can also see those transitions in the molecular record which is amazing yeah yeah that's because that's a very very accurate i guess kind of markers it's accurate makes sense too yes yeah i mean we all science is about making sense of the environment right around you and making sense of the phenomena we experience and we live in a very very complex planet and it is very complex largely to do with the presence of life yeah and the history of earth is very very different that we now know to the history of mars largely as a consequence of mars being smaller than the earth and mars having lost its water it may well have had as much water in the beginning as earth had but that radiation from the sun and the smallness of the planet means it lost its heat more quickly than the earth did and didn't develop the cycles that the earth has developed that help us preserve the water um hm the water in the atmosphere are what's blanketing us and protecting us in a large degree from solar radiation as well as the magnetic field mm mm mars probably had a magnetic field very early on but also lost that so it lost the ingredients that would have made the planet habitable we know that mm mm what we're trying to do is understand something about the very early history of mars uh hm uh hm and when it still might've had a magnetic field and might've had an atmosphere mm mm might've had an ocean mm mm and that's the sort of logic that curiosity is trying to develop and of course curiosity is just one theme in a long history of exploration uh hm of planets by largely driven by nasa but increasingly by eastern the european space agency right and now china and india right everybody will be in on it everybody's in the game but it's all about sharing knowledge yes and that's the other thing the sort of a real community maybe peace will break out or something big in this community because there seems to be a fair amount of sharing with i think science as with like arts and music yeah there ways of soft diplomacy yes exactly and that's why i but pretty effective well that's why i love being a scientist because you can interact with people in any country yes in the world on common ground and we're not concerned about our differences we're concerned about our common ideals and our common hopes exactly yeah and i think that it's one of the great joys of being scientists and that's why i would recommend that science as a career for young people well said back to mars for a minute there has been this controversy around methane yes i don't know whether it's controversy but that methane can be they're always careful with the modal can be an indicator of life but it isn't necessarily can you explain that to us and then in the last several weeks sometime in the last several weeks that was sort of confirmed a methane like cycle on mars what do you think of that and first of all though about the methane itself so now i'm showing a picture of sam okay and the sam instrument is really three instruments yeah it's a gas chromatograph which i explained yes is used to separate molecules it's a quadrupole mass spectrometer which is used to identify those molecules and it's a tuneable laser spectrometer tls is the acronym mm mm that can look at gases and it can measure the spectrum of gases okay and it's been used to largely to evaluate the atmosphere but if we heat a soil up or a crushed up rock and heat that in the system the gases that are evolved can be looked at in the tls okay and of course there had been reports of methane on mars in the past okay based on information from telescopes on earth as well as orbiting telescopes or spectrum a combination of telescope with a spectrometer so it has this equipment it can identify and presumably it was instrumental in determining this thing but what is the issue then with the methane well the issue with the methane is that it had been detected from earth but when you look through earths atmosphere there's methane yeah in our atmosphere yeah so the difference between the signal they are looking for is teeny weeny on top of a much larger signal from our own atmosphere so if you're using oh i see a telescope i see i see yes on earth you're hoping to see through the atmosphere but there'll be methane in that and see a little bit more signal right when you look at a particular place on mars so there were a lot of controversy about how real was the little signal when it sits on top of a much bigger noisy signal right and being able to measure it in situ yeah in mars atmosphere on the surface of mars was considered to be a much more reliable measurement and so the instrument takes in a sample of atmospheric gas freezes out the carbon dioxide and some of the other components to enrich the sample and ultimately they've made i think four measurements where methane is just a little bit above the background of the instrument so in all of this work you're looking for a signal on top of inevitable background i see what we call it yeah signal to noise ratios okay okay and the signal that they're getting from methane on mars is very tiny it works out to be about seven parts per billion so it's minuscule compared to the amount of methane ah that's in the air we're breathing okay okay very very small amount all right and not only that it was not there in the early part of the mission the rover got to a certain place and suddenly they made four measurements four or five measurements where they got this small amount and just as quickly as it appeared it disappeared hm and the appearance and the disappearance of the methane does not correlate with any other measurements that curiosity's made it doesn't correlate with day night it doesn't appear to correlate with the amount of radiation mm mm it doesn't appear to correlate with what month of the year there's no other measurement that curiosity's made that bears any relationship to the appearance and the disappearance of the methane so that bothers people you should if it comes and it goes mm mm you should be able to understand why that is mm mm but that was the same as the experiments when they detect that it using earth based satellites earth based telescopes sorry that was interference yeah well it appeared and disappeared i see yes and so it appears that it's coming from somewhere but in very small whiffs i see and there's no really solid understanding of what those whiffs mean okay on earth a lot of the methane comes from biological processes right and those processes overwhelm the formation of methane from nonbiological processes okay and so even though you can identify a small amount in mars atmosphere there's no way there's enough of it to get any other information that would tell us whether this is biological or nonbiological okay so it's a really interesting and intriguing scientific yes yeah problem but it's also an enigma at this point at this point right so you were not speculating on it even there many aspects of the behavior of materials on mars that are different to earth one of the things is mars surface environment is very oxidizing ah over its history the water has been what we call focalised to hydrogen and oxygen mm mm so h2o mm mm goes to h2 and o or o2 mm mm mm mm and the hydrogen because the gravity is lower the hydrogen can be lost to space leaving the surface enriched in oxygen and that oxygen is mostly tied up in minerals like sulfates and perchlorate strongly oxidizing minerals and strictly speaking the processes that form those minerals should also destroy the methane oh yeah yeah yeah so the fact that there's some methane still there tells us that they if it's true if the measurement is real that there must be some process still generating the methane and that is even more intriguing some people would like to think it's biology but there's no evidence for it of course everybody wants to think it's biology i have to let you talk to the audience here very soon but is there anything that you would speculate on about mars in terms of this project that you'd like to tell us about it's proved very very difficult to find any organic matter mm mm on the planet mm mm and organic matter on the earth is a biosignature mm mm and the failure to find organic matter on mars might be interpreted as the absence of a biosignature mm mm but again we think it's a strong radiation environment and the presence of these oxidizing materials like sulfate and perchlorate mm mm and oxygen itself mm mm this destroyed it mm mm so the drill can only go in a couple of centimeters mm mm we can't go deep enough mm mm that where you might find material that's been separated from these nasty processes right a lot of people want to have life under the surface of something or other you know yeah i remember thomas gold he's a scientist here speculating that the earth very deep down was full of bacterial life you know it is and evidently it turned out but he was laughed out of the room when he first mentioned that i think but he also said that fossil fuels aren't formed by biological processes yes all right don't go there so he was right about the deep biosphere and very wrong about a few other things yeah but in any case people want to find life out there in the worst way do scientists sort of are they optimistic pessimistic or just totally bewildered like it's too hard to reconstruct not so bewildered again it's taken hundreds of years for us as scientists and particularly geologists to understand and put together some history of the earth required all sorts of scientific inputs like the discovery of radio activity mm mm gave us a tool to date rocks precisely mm mm people used to estimate before they had real mm mm dates from uranium led decomposition it's a very long iterative process to understand the history of the earth mm mm paleontology geology geophysics and now you need all of it seems like yeah and that same series of streams of logic and knowledge are being applied to mars mm mm but what we're finding out is mars is very very different in all sorts of interesting ways and ultimately people will come to an understanding of those processes through this mission and hopefully it continues for a few more years the rover stays alive and then that amazing this machinery by itself is and it speaks in a spectacular way to the engineering skills i agree of all the people that work yeah on developing the rover itself the delivery system yeah the landing system it's just the spectacular it's a real tribute to humanity i must say absolutely isn't it yeah yeah and a lot of those scientists are usbased but there also a lot of them based in other countries there's russian scientists and there's french scientists working on this mission so it really is international and it really is a spectacular scientific and engineering accomplishment yeah there's one other important aspect and that's leadership the leadership of the mission has been spectacular and the principal scientist john grotzinger who used to be a professor at mit oh led that mission for the seven years the most critical seven years and i think his way of getting people to work together yeah and be critical of each other without cutting each others in a positive way yeah a productive way i should say yeah the whole job your whole job there is to do good work but also to prove someone else wrong and to get people to do that in a constructive way is really a remarkable achievement yes the hole mission is spectacular i have to leave it there so that you can talk to the audience dr summons thank you ever so much for being with us