Prof Sara Seager: Signs of Life beyond Earth

[Music] well good morning good afternoon or good evening depending on where you are in the world welcome to astrofest 2020 a collaboration between sci-fest africa south africa's national science festival which is presented virtually this year and the south african astronomical observatory which celebrates 200 years of existence as an astronomical observatory this month congratulations to our colleagues at the sao my name is anja fari i will be your chair for today and in my other lives i am a friend of cypheas africa and sao and project director of broader impacts at the national radio astronomy observatory in charlottesville virginia in the usa a few front of house rules and requests before i introduce our speaker we welcome viewers today on zoom as well as on the sci-fest africa and saa sao facebook pages so if you have any questions for our speaker please post these in the q a box at the bottom of your screen if you are using zoom or in the comment sections if you are joining us via facebook please also understand that because we are broadcasting on these three platforms the questions will be moderated and we may not have time to ask you a question so please don't hold us too responsible for that however what i can tell you is that professor sarah seeger has a surprise for those of you who ask the best questions which i will ask you to announce when i hand over to her in a bit so on 14 september 2020 an international team of astronomers and planetary scientists presented evidence that the cloud tops of the planet venus contain traces of phosphine a toxic and rancid gas that is produced by microbial life and some industrial processes that we have here on earth but the chemicals presence is a mystery because no known non-biological processes can actually create phosphine in the conditions found on venus which really isn't very surprising considering that the surface temperature on venus is 370 degrees celsius or 700 degrees fahrenheit that it has 90 times the atmospheric pressure of earth and that the clouds are primarily made up of sulfuric acid which is pretty nasty the alternative is that the phosphine could be the result of some unknown unknown chemical process which would really be interesting in its own right it's my privilege to introduce to you today professor sarah seeger one of the scientists on the international team that published this discovery and was selected by breakthrough initiatives to lead the investigation to confirm the evidence and its implications for the search for life beyond earth sarah is the class of 1941 professor of planetary science professor of physics and professor of aeronautics at the massachusetts institute of technology otherwise known to most of us as mit an institution which is ranked as the best university in the world for the last six years and really is recognized as a scientific research powerhouse by those who work in astronomy and space research exoplanets are planets orbiting a star outside the solar system or the milky way and as a 20 october the discovery of exoplanets confirmed stood at 4292. now sarah is create is credited with laying the foundation for the field of exoplanet atmospheres while her current research focuses on exoplanet atmospheres and the future science the future search for signs of life by way of atmospheric biosignature gases such as the one found on venus she was a part of the team that co-discovered the first detection of light emitted from an exoplanet planet and the first spectrum of an exoplanet and of course the detection of phosphine she has authored and co-authored over 200 research publications and if you're in academia you know that that is quite a feat she's also authored four books the latest is titled the smallest lights in the universe and this is a memoir of sarah's search for meaning in the work of her husband's unexpected death and as she scours the universe for a one in a billion world enough like ours to be able to sustain life ladies and gentlemen a virtual round of applause and welcome please for professor sarah seeger over to you sarah thank you so much everyone and good afternoon good morning good evening depending on where you are can you all hear me okay we can all right so today i'm going to talk about exoplanets i'm going to talk about venus and the search for signs of life so for thousands of years people have wondered what is beyond earth when i was a child i grew up in a city in toronto canada actually and there we could see basically no stars we actually when i was about 10 years old i got to go on my first camping trip and i could see the dark night sky full of so many stars i wish i could see all of you because i would ask how many of you have seen the truly dark night sky well i hope you can go and see it soon or see it again because we know now we think that every star has planets all stars are suns we know of thousands of planets around other stars we call them exoplanets and it's just incredible how many many planets we know about it turns out that that uh we have found so many planets but we haven't yet found a solar system copy and that's a bit perplexing because it's starting to look like our solar system is quite rare although it is actually very hard to find but in our search for life around other planets we're we're banking on the the fact that life on earth uses chemistry to extract store extract energy from the environment to store energy and that life on earth anyway releases gases into the atmosphere so a few billion years ago cyanobacteria on earth discovered photosynthesis and eventually re and eventually re-engineered our atmosphere to fill it with oxygen without vegetation and photosynthesis our earth would virtually have no oxygen in its atmosphere so there is an intelligent alien species orbiting a planet around a nearby star with the kind of telescopes we're hoping to build and they look back at earth and see that our atmosphere has 20 oxygen by volume the aliens will be highly suspicious that we might have life on our planet earth so for today i'm going to be um talking about exoplanets first then i'll get to phosphine on venus followed by next steps so as our hostess was saying i actually will have a prize for the best question and this is my new memoir which describes a journey through outer space and also one through inner space but because i am aware that many of my astronomy colleagues from around the world are also listening in i have a second prize actually for the best what i call technical question now this book has a lot of physics it has derivations and physics from all topics of exoplanets so i hope you enjoy these books so on to my first topic i have some kind of introductory information first before i get and i'll have a few technical details mixed in so in our search for signs of life uh we want to find eventually find another planet like our own the problem is not so much that an earth itself is so hard to find but that the earth is right next to a big bright massive sun so i want you to imagine for a moment i'm actually ready for pull one that your job now is to try to help find another earth but i want you to know that our earth is a hundred times smaller than our sun it is three hundred thousand times less massive and 10 billion times fainter than our sun so if my host is able to launch poll one poll number one please go ahead because i was going to ask you in the audience which technique would you choose would you choose one that involves planet size that's the most favorable combination it's poll number one you're you're voting for here or would you choose the method that involves mass would you in choose a method that involves planet brightness so just for if you don't make measurements it's so hard to make a measurement one part in 10 billion almost no one on the planet earth has ever made a measurement to that many decimal places all right it looks like about 39 oh people haven't voted we might have a oh we're getting vote here so so far people are heavily voting for planet mass they you could go back okay let's see what's going on with the poll so actually people are also answering my poll number two which we'll come back to later it looks like right now the winner for which planet finding method would you choose is actually looking like number two planet mass okay we can end the poll and let's see if the the results will split display my favorite one by the way is the one part in 10 billion the reflected light and i might be able to get to that in the q a if you ask me a question a lot of people voted for planet mass still harder the answer to there's no right answer here but the method astronomers are using most commonly today actually is the easiest one that involves the method that involves planet size all right thank you we can stop sharing the poll now and here i'm showing you for those that don't know what a transiting planet is i'm showing you an artist's conception showing you the planet going in front of the star can you see that star planet going in front of the star and on the bottom it shows you the transit what we actually measure so we measure a planet star brightness the star's brightness as a function of time looking for that tiny drop in brightness that shows a planet that's going in front of the star i actually just stepped down from my job as deputy science director of the mit led nasa mission test and tess stares at a giant strip of the sky 24 by 94 degrees and tess monitors 20 000 stars at high cadence and another million stars at low cadence and downlinks all that data to earth once a month and the test team finds a hundred new planet candidates every month with the transit technique it's a very popular technique so it turns out we try to make our life even easier on exoplanets and we do that by actually not just trying to find an earth around the sun but focusing on small stars small red dwarf stars and here's a a real image of our sun with a fake planet in front of it the size of earth and on the right side i'm showing you a small star a fake image of a small star it's called that particular star is actually called trappist one it's a very small very cold star any smaller and colder and it actually wouldn't be able to have fusion inside it wouldn't be called a star but you can see the same size planet on it cuts out a much bigger area its planet to star area ratio that is the transit depth the drop in brightness is about one fact is about one part and a hundred which is actually relatively straightforward to measure for our earth and sun that value would be one part in ten thousand we're interested in studying the atmospheres of exoplanets and the atmosphere is so tiny it's like the skin of an onion on an onion and for a red dwarf star the planted atmosphere might cut out one part in ten thousand but on a sun-like star it's a much harder thing to observe so your takeaway here is that most of our focus in exoplanets in the search for life is on planets transiting very small stars to explain that to you a bit further let's go on a journey to a small planet orbiting a small red dwarf star this is an artist's conception but i want you to imagine for a moment we were able to get in a spaceship and travel to this planet first of all the sun or the star might be very big in the sky because the red dwarf stars give off very little energy so like the analogy of if you're have a very small campfire you have to be very close to stay warm the planet has to be quite close to the star now a consequence of the closeness to the star is that strong tides from the star on the planet do something strange to that planet like on earth earth here we have ocean tides but over time the planet would go into a very special orbit just like our moon shows the same face to earth at all times the uh planet would rotate one time for every time it orbits what this means is that one side of the planet is always in daylight and one side's always at night so if we could be visiting this planet you could choose would you visit where it's always daytime or if you're an astronomer you would want to go where it's always night permanent night radio astronomers could probably choose where they want to go another thing about these planets is so close to the star by kepler's third law they orbit the star very quickly so one year might only be about 10 days long now in second thought it wouldn't be such a great idea to get in a spaceship and visit these planets if we could even do that these red dwarf stars have flares lots of flares so we couldn't flip out our phones be constantly using them because the high energy radiation would destroy our phone's electronics what kind of sunscreen would we bring some of these red dwarf stars have flares equivalent to the giantess flare we've ever received on earth from our sun it was called the carrington event and they're receiving flares like that something like once every 80 days actually the trappist 1 star appears to have giant flares once every 80 days so although we're focusing on emdorf stars because they're easier to find planets around and study the atmospheres we're not 100 sure that they're the best places to look for life mostly because of the flares on those stars so i still have a bit more background info for this talk and i wanted to share with you how we study exoplanet atmospheres today the main way that we study exoplanet atmospheres you'll see on the top right the artist's conception of a planet in front of its star this is a transiting planet planets are aligned just so so that the planet goes in front of the star as seen from the telescope well this is showing you a glowing atmosphere and that atmosphere is being backlit by the star and that's the artist's conception of what's happening we actually measure the star by itself then we measure the star with the planet in front of the star and we're able to subtract that and through a lot of careful complicated data analysis get out a signal of the planet atmosphere now i want to take like one or two minutes this is for the casual enthusiasts out there to explain to you like a somewhat complicated concept and that is that the i want you to imagine this uh planet being observed for its atmosphere at a wavelength where the atmosphere is completely transparent in that case the planet has a fixed certain size as superimposed on a star now imagine that the we're observing the planet at a wavelength where a molecule of interest is very strongly absorbing now the atmosphere is no longer transparent it's now blocking light and the planet will look a tiny bit bigger that's the whole concept behind studying exoplanet atmospheres i know that was a little complex so you don't have to understand this to understand the rest of the talk but i wanted to share with my astronomy colleagues like this kind of cherry pick best case scenario one of our best transmission spectra for transiting planets this is a hot saturn exoplanet it's very low density it has an incredibly puffy atmosphere so it ends up getting a very big signal what you're seeing here is the transit depth you can think of that as kind of like the planet size as a function of wavelength in microns so the left part of the plot leftmost part of the plot is visible wavelengths the middle is near infrared the white points are hubble space telescope data points and the curves the colored curves are models now what you see in the middle there is a up and down you're seeing a feature of water vapor actually and remember what i said before that the planet looks a tiny bit larger at wavelengths where the atmosphere is strongly absorbing this giant planet has water vapor it doesn't have water oceans it just has hydrogen and oxygen which on a giant planet want to be in water form and you you have to see this plot if you don't understand anything i said then all you have to do is agree with me that the white points in the plot are different from a straight line and if you agree with that you're actually agreeing that this planet has an atmosphere that happens to have water vapor in the atmosphere now each molecule more or less has a special fingerprint and if you look at the model here and some of the data you'll see like several features from water vapor and it looks like at least two or three of them are well marked out by the data this feature by the way the big feature in the middle if you were to read the y-axis and try to guess like eyeball how strong that signal is it's about one part in a thousand and from one of my previous slides i mentioned that for a small red dwarf planet the atmosphere signals about one part in ten thousand for a small planet orbiting a red translating a red dwarf star so we still have to do way better now it turns out that today one of our workhorses for exoplanets is the hubble space telescope which we use to study hot giant exoplanet atmospheres soon we'll use the james webb space telescope to push to much smaller exoplanet rocky atmospheres now there are literally hundreds of astronomers in the exoplanet community who are planning to use the james webb space telescope in good news an article crossed my news feed today saying that the james webb space telescope is still on schedule to launch to launch in 2021 that's next year in the bad news is astronomers we're still working out just how well we think the james webb space telescope can do for small rocky planet atmospheres you know one part in ten thousand one part and a hundred thousand it's a very very um very tiny signal we'll have to wait and see how the first round of data does but we're all pinning our hopes on trying to find trying to be able to study those small rocky planet atmospheres in this picture i'm just showing you the nasa mission tests it won't be with james webb it's just here for to remind me to tell you that tess is very busy finding these small planets transiting small stars so now the question is when we are able to study small rocky planet atmospheres what kind of gases do we want to look for we want to know yes actually there's a question about this um we'd like to know what gases should we look for i already mentioned oxygen where oxygen fills our atmosphere to 20 by volume but it turns out that on our planet oxygen was only significant at 20 by volume for the last billion years that actually sounds like a long time one billion years but earth has been around for four and a half billion years so we don't really know on an exoplanet what molecules we should consider now my second poll question which we don't have to do again but i asked you you know have you received a crazy theory have you sent a crazy theory please don't send me your crazy theory in physics and astronomy we get crazy theories every day so we had a 75 response that said people had received a crazy theory and we had a 25 response saying you sent a crazy theory and so i was pondering this question what kind of gases should we really be thinking about and i came up with my own crazy theory and that crazy theory was that perhaps all molecules that are in the gas phase perhaps they're all produced by life when i thought about the molecules i knew before i stud this was before i had to study chemistry all over again like humans we breathe out carbon dioxide ozone is actually made inside some cells life makes nitrogen and nitrous oxide and methane and all the gases i could think of well who does the mit professor go to with the crazy theory i could actually spam everyone i know but i had to go to the next highest level to a nobel laureate and i actually had recruited two biochemistry colleagues to work on this theory and we actually went um across the river this is before the pandemic when we actually went to work but we worked on our theory we had some slides we asked this nobel laureate his name's jack shastack and he nobel laureate in medicine so we went and asked him about biology and it was really interesting because we presented the theory that perhaps all like life makes all molecules and he crushed the theory he actually found a counter example a simple molecule that is definitely not made by life and we were were crushed well we went back to work and still wanted to make a giant list of molecules what are all the molecules we should think about how could we filter them and this image now is showing you a sea of molecules because we did a giant combinatorics literature search and we came up with the point that they're actually well over 14 000 molecules that are in gas form at earth's temperature room temperature and pressure and we actually filtered all of these we found that about a quarter of them are made by life on earth so it's not all but it's still a large amount and we have very complicated algorithms that work through which molecules are of interest which are not we want to be prepared for any kind of biosignature gas detection and it's a little too detailed to get through this actually there's no possible way i could explain all the years of work and algorithms that went into here suffice to say we made some really interesting findings with our giant database one of them is not related to astronomy in any way but it is that some molecules or molecular fragments appear to be never made by life we're following that up as a non-astronomy project but a large part of this database now either molecule by molecule or giant classes of molecules that can take care of hundreds of molecules my team is studying as bio signature gases and one of them the more interesting ones we came up with that checked all the boxes for useful biosignature gas that is has unique spectral features that is likely doesn't seem to have any false positives that is um is actually can accumulate in an atmosphere of some kind and is actually detectable one of the first ones from this giant database we started working on was phosphine gas so phosphine is a really interesting gas i'm kind of guessing that a lot of you at least until our host or hostess introduced the talk you might not even have heard of phosphine it is a gas that actually it's a very interesting gas but first of all phosphine is a phosphorus atom and it's attached to three hydrogen atoms so on a planet like earth where we have oxygen and carbon dioxide phosphorus usually wants to be with oxygen it doesn't want to go with hydrogen so phosphine is a gas that people don't usually talk about they don't usually hear about it the element phosphorus all life needs it we usually use it as phosphate which is a phosphorus attached to oxygen atoms phosphine initially in our database um initially at least appeared to be almost completely absent from biology life hardly ever appears to use or produce phosphine and so when we first started looking into phosphine we had to deal with a couple of like major arguments against phosphine as a biosignature gas one of them is that phosphine is very toxic and unstable it turns out that phosphine actually was used as one of many one of dozens and dozens of of gases as chemical warfare in world war one the other one people like to complain about against phosphine is that there's no actually confirmed species that produces phosphine so it turns out that in terms of it being toxic and unstable that is really true but it turns out only to be true in oxidized environments in terms of not being produced by any life it's true we do don't know exactly which species of life it looks like it's some kind of strain of e coli that produces phosphine but there's incredibly strong evidence people take cultures of mixed bacteria into the laboratory and they've measured phosphine coming off of that people and though people have also found phosphine gas coming off of environments where there is life these are oxygen free environments such as wetlands or sludges and phosphine has been fined in the guts of many different animals it's actually in guts they find it in feces in fact there's a funny study saying that phosphine is a very high concentration in penguin poop over penguin colonies once i got to go to chile and i actually got to see some penguins actually it was i understand there are some penguins in south africa so you could test out this theory of phosphine being very strong over penguin colonies if you ever get to visit a very concentrated colony so what we do in exoplanets and by the way you don't have to understand this graph to understand the rest of the talk we make complicated simulations of exoplanet atmospheres and we simulate the noise budget that we might expect with the james webb space telescope and what you're seeing right now is transit depth as a function of so you can think of then gat as a proxy for planet size as a function of wavelength in microns so this is mostly the infrared and the purple area is one instrument on the james webb the green area is another you're supposed to by eye compare the white curve and white symbols with the blue curve and blue light blue curve and light blue symbols to the top versus the bottom and the bigger features are what happens when the atmosphere has phosphine in it now it might look like by eye that you can see that if that's your real if that turns out that our data is as good as this data that that could be your real a really great signal but if you look at the y-axis you'll see it's a very tiny amount it's going to be a challenge now the one thing that we've discovered in all of our computer simulations of biosignature gases is that a lot of the gases that are not big on earth they can accumulate in an atmosphere without oxygen because oxygen and its byproducts oxygen's byproducts rather are terrible for gases the hydroxyl radical oh it is the garbage eater of our atmosphere and literally destroys almost every molecule so we like atmospheres that don't have oxygen because we're finding that gases can accumulate much more easily but a major negative we're finding just for my astronomy colleagues out there it's it's kind of um depressing to admit this out loud but it may not be surprising to you is we're finding that to have a hope of detecting a biosignature gas life would have had to re-engineer the atmosphere like the cyanobacteria did for oxygen on earth we would need a life form it's not going to be penguins with penguin poop but we need some kind of life form that can produce so much gas huge amounts of gas that could help re-engineer the atmosphere and so a kind of quantitative way to look at that is the gas molecule that would be the biosignature has to be produced faster than anything destroying it so that's usually related to the ultraviolet photons coming from the star that would break up a molecule create a radical that would destroy the gas and we're finding this with a lot of so by the way for phosphine in this image we need a huge amount of phosphine 10 to 100 times more than the amount of methane being produced every year on earth but actually less than than what's over a penguin colony and so just to kind of conclude this biosignature gas summary for part of the talk this is showing you a bar chart of the blue bars are gases my team has studied recently the yellow bars are earth's level and the units on the y axis are it's the biological surface flux like how fast is life producing it as a rate you can just kind of eyeball the curves though and on the bottom it's telling you the different gases we've studied phosphine isoprene ammonia and it's comparing it to oxygen so you see for the blue bars in every case we've studied so far we need way way more gas produced by life on another planet than the gas that's being produced by life on earth actually so all this is still going on there are other groups around the world working on bio signatures we'll just have to keep chugging along all right so now perhaps the moment some of you have been waiting for what if we search for phosphine much closer to earth okay this is a pretty interesting story that i'm going to launch into because unbeknownst to my team we've been working on phosphine for a number of years and it's pretty obscure for astronomers let alone anyone to to be working even biologists to be working on posse we had no idea but um there was another person working on phosphine and that is professor jane greaves professor jane greaves actually found some obscure biological papers that did say that phosphine is associated with life on earth and by the way i forgot to mention it's not produced any other way on earth it's produced by us humans as like an insecticide but it's uh it's actually not able to form on earth's temperatures and pressures on its own so professor grieves read about that and she very boldly purposefully decided to search for phosphine gas on venus and she applied to the james clerk maxwell telescope which i've got to visit by the way in hawaii it's on a mountaintop in hawaii and she her proposal was first rejected actually because you know it's a crazy idea to look for life on venus it's considered incredibly fringe and just not not really a thing to do so she did the second time around actually get time on on the telescope and she found a signal of phosphine and as professor jane grieves tells us she was more surprised than anybody but the signal was actually somewhat weak so she needed to get a stronger signal around that time someone a mutual contact connected my team and there's a lot of people on my team um working on this with professor jane grieve's team and so we all work together to write a proposal to alma a much larger radio observatory high in the deserts of chile above all the water vapor that causes trouble for radio observatories i haven't got to visit chile i would actually love to go and see alma it's so high up i understand it's like 17 000 feet where it's very hard to breathe it's purposely at one of the highest driest places on earth and it's just an incredible facility alma has about 66 telescopes 50 of them are the main array each of them have about 12 meter diameter and they act together as a single telescope now most people don't observe solar system planets with it so it's not not a common thing to do but we helped jane with a successful proposal to alma to look for phosphine and we found phosphine gas and now i'm going to tell you a bit more about that so venus is a very crazy planet we actually used to call it our sister planet because it's about the same mass and size as earth but venus is a very hostile place for life due to a massive carbon dioxide greenhouse atmosphere venus's surface temperature is so hot at 700 kelvin no life could ever survive at the surface but starting with carl sagan over half a century ago people have been speculating about life on venus and this is because away from the surface above the surface far above the surface at about 50 to 60 kilometers venus has the right temperatures for life not too hot not too cold just right for life and this cartoon is showing you venus's atmosphere if you look on the left it's showing you altitude in kilometers going from zero to 100 kilometers the cartoon image is showing you the cloud deck up where that's where people have speculated there's life but it's still an incredibly nasty environment because we do think that life needs some kind of liquid to survive so that chemical reactions can happen but in this venus cloud deck there are not water droplets but there's acid droplets hydrosulfuric acid which no life as we know it could survive there nonetheless we did find phosphine in the atmosphere now i'm going to just explain this for a moment but what we're seeing in this i'll explain this figure in a moment but what's going on is that the sunlight hits venus some of it gets to the atmosphere and surface and heats it up just like if you go outside on a hot summer day the pavement can be extremely hot and the pavement isn't hot because it has its own like energy source it's the sun that has heated it up but the pavement is giving off heat so venus's surface and atmosphere are giving off heat from reprocessed sunlight that's what we're measuring actually but within that heat coming off of venus there are absorption features where gases are removing some of that radiation from our view and this plot here is showing you on the x-axis you can think of it as frequency but in radio astronomy astronomers typically like to use velocity instead and the y-axis is a normalized ltc means line-to-continuum ratio where continuum is this average the average value kind of going across zero and the line ratio the line is that drop in brightness that you're seeing so what's interesting here is that i actually put a few notes in on the on the side for you to read but again just to oversimplify this is that if there were no phosphine on venus this would be a straight line effectively the fact that there's a drop in the signal at exactly the frequency where phosphine absorbs is why we're claiming we have found phosphine on venus now a lot of work went into getting this spectrum it was years and years of work from professor jane greaves her team alma experts and a lot of people have contributed this and i don't i'm going to come back to this figure in a moment and i know there's a lot of good questions and i will come back to those we'll have we'll have a good amount of time for questions at the end now one immediate point to make is that phosphine does exist on jupiter and saturn these planets we always think of jupiter as being a very cold planet but in fact not too far beneath jupiter's atmosphere it's actually incredibly hot the atmosphere traps energy that jupiter had since it was born energy that's been slowly leaking out throughout its billions of years of existence well right beneath that atmosphere it's very hot pressures are high and there's a lot of hydrogen because jupiter's whole composition is dominated by hydrogen and so phosphine wants to form it doesn't need life the temperatures pressures and amount of hydrogen are all there to make phosphine well our team had to work through a lot of scenarios to find out why might there be phosphine on venus we thought about volcanoes and surface minerals i have a lot of notes here it's not have time to go into all the details i just wanted you to know that the team has really thoroughly considered all possibilities and we haven't found any that are able to produce phosphine at the levels we have measured you know lightning is another one we looked at it just turns out that venus like earth is what we call oxidize venus doesn't have oxygen in its atmosphere but it has carbon dioxide and everything we know about the planet points to there being enough oxygen around that all the elements want to be in their oxygenated form so that's why it's so hard to produce phosphorus no matter what you know no matter what scenario you want to consider meteors we also thought about that that meteorite delivery you know we get tons of meteorite material here as does venus and these could actually add some phosphorus element but even then it's not enough to populate the atmosphere with phosphine and in our paper we actually worked out all the quantitative numbers for you so um it always falls short by sometimes in this case 100 million times so yeah so we do have a lot of really good questions and um just to summarize the phos venus phosphine part of the talk we're not claiming we have found life on venus we are claiming that we have detected phosphine gas whose existence is a mystery either it's unknown chemistry or possibly life production because remember on earth phosphine is only associated with life so just to um quickly go through that we get a lot we were overwhelmed when we announced this hundreds and hundreds of people all around the world um like wrote to all of the different team members a lot of them were people we knew saying wow this is awesome but probably more where oh you forgot about this or what about that and there were people who not surprisingly they didn't have time to read the paper in detail to absorb everything we had been thinking about this for some of us two years some of the team five years and people had only had five hours they went kind of crazy on us and it's still been going on all in the last month so one of the criticism was there's only one line if you remember back to the transmission spectra i showed you we saw a lot of different water vapor features we want to see more than one line but unfortunately alma only has one line one of our friends invented a new term for us called kemp's laning everyone wants to send us their favorite theory and that's great because science we want you to we want it we'd be i don't know if happy is the right word happy or sad or both that if we can find a way to explain the presence of phosphine on venus by chemistry we're welcoming people to have theories check the papers write your own paper get it peer reviewed we get the contaminant question it could be a contaminant again we worked really hard to rule out any other molecules we actually didn't find that there are any that are absorbing that the same frequency as phosphine any molecules or isotopes of molecules present in venus's atmosphere now just a quick aside to this is that when we work in the optical and infrared especially the infrared actually there are so many lines molecules are rotating and vibrating like molecules are rotating molecules are rotating and vibrating and it's such a crowded field but out in the radio typically things are much more spread out because we're only seeing rotational features not rotational vibrational features now this last one it's too much to unpack here today but there's very specific criticisms about the data analysis i want to reassure you that what the team has done is standard in the field for decades we detected an expect expected line of deuterated water using the same procedure and as a sanity check we searched our data with the same process for absorption lines at other frequencies and found no signal now some of you are okay so let me just this is the kind of unplanned part of the talk well some of you are on social media or astroph that's the astronomers i know other people are too but you'll be getting this in your feed that today a team put on the archive an unrefereed paper saying that they had re-analyzed the alma data using this kind of slightly different process and they're claiming they did not found phosphine they did not find phosphine gas well i'm not going to be able to respond to that point by point i just want you to know that it's sort of a very natural thing in science where one team says we found this and then everyone else is trying to say you didn't find this or you didn't find that or it's this chemistry or it's that chemistry so this will all take some time to play out i do have a really exciting reassuring point of information to share with you though and that is that a team went back and looked at pioneer venous data that hadn't been looked at before it hadn't been checked for any signs of phosphine and this particular instrument actually it blew apart all the molecules and it looked at what fragments of molecules what ions were present and they found three or four fragments of phosphine that could only be associated with phosphine so we actually do have some corroborating evidence but big discoveries of this kind they take a long time to settle out in the community so next steps i'm so proud to be leading a concept study for a mission to go to venus and to look in the atmosphere directly we're actually studying three separate ideas one is what we call small mission one is medium one is large the small one we would we are planning to team up with rocket lab who have already claimed that they're going to launch mission to venus in the year 2023 which for space is actually very very soon this mission would be small in that the payload the actual scientific instrument aboard the survey craft would only be about three kilograms that's actually really tiny but we could send a tiny spectrometer that could look in the atmosphere directly for phosphine and other gases our medium mission and our large mission is inspired by the russia vega balloon missions where there's a model shown on the the right picture and this balloon has a payload that's the thing dropping off the bottom and our large mission concept could even include a microscope so in the meantime astronomers are using ground-based telescopes at infrared wavelengths to also try to search for phosphine but ultimately only going to the venus atmosphere directly will help us figure out what's next okay so i just have a couple more slides i just wanted to say that for exoplanets i didn't have time to get into this part of my talk but we have a wealth of new telescopes waiting to observe small planet atmospheres but i wanted to just you know summarize by saying that it's an incredible time for discovery this plot is showing us on a log scale distance away from our sun there are the terrestrial planets close to the sun there's jupiter saturn uranus neptune further away and all of our planets are have many of them have renewed interest as astrobiological sites but beyond our solar system there are voyager 1 and voyager 2 which are still making new discoveries and outside of our solar system are the very nearest stars the ones we're trying to find planets around that around bright enough hosts so we can get enough photons to search for signs of life so to summarize there are thousands of exoplanets are known to orbit nearby stars small rocky planets are established to be common we have next generation telescopes that i mentioned focused on the james webb space telescope that will give us our first capability of observing atmospheres of small planets for water vapor and biosignature gases venus is the new frontier inspired by phosphine gas there's a huge renewal on venus we hope that we've moved the needle so that current missions under competition under study will get a chance to go to venus and find out what is is really happening there thank you for your attention thank you very much sarah so what we have done sarah is just to moderate and to group some of the questions there were plenty of questions and i think this could probably go on for quite a while so what i've done is just to you know group them in terms of the types of questions and as they relate to your talk and the first set of questions is really about um the nature of life um as well as you know that the nature of life outside of of our solar system um the first question is from camille thank you camille has asked a lot of questions the first is how do you define what life is what would molecules on another planet look like how do we test for something that we don't yet know how to define um yes should i would you like me to answer that one that's fine continue so yes we don't know how to define life i personally don't in astronomy we cheat on that one and we don't bother answering it all we say is that life metabolizes at least life on earth uses chemistry and as a byproduct has gases and so if there's some other kind of life or we don't know what it's made of we're still hoping that life use that we're assuming that life somewhere uses chemistry and as long as that life outputs a gas that can accumulate in the atmosphere we have a chance of detecting it but all other kinds of life are off the table for us now part b when we talk about venus specifically now we have a new environment sulfuric acid which our own dna amino acids and proteins cannot survive in and there we can make some concrete steps to figure out what kind of life could survive there we can do experiments where life might be inside a protective shell like waxes or graphite or lipids so that's a harder one we stay tuned for an answer okay and then the question from chris was would it be reasonable to assume that microbial life found on venus would be carbon based we don't have any reason to not assume it's carbon-based and it's kind of beyond what biologists can do today to you know construct other life-forms but carbon is incredibly common element and venus has a lot of it so it's probably a good starting assumption okay chantally i think um sarah has answered your question about you know the elements we may not know are present um you know and how they would be invisible to to our spectroscopes another question is it possible for life to begin exist and die only in the atmosphere of venus and never reach the surface of the planet you know that's a tough one we don't we don't know the answer to that i think the favorite theory is that if there's life on venus it has initiated on the surface a long time ago when venus had water oceans and as venus warmed up and went through a catastrophic greenhouse the oceans evaporated and life moved to the atmosphere here on earth by the way we do have life in our atmosphere bacteria floating around inside inside or outside cloud droplets but it only stays up for a few days so people do speculate on whether like meteorites could deliver material that gets absorbed in the clouds and maybe that's enough to start life but we don't have a worked out theory so it is a really good that's one of the that's a really good question okay that came that was from camille as well from julian could the phosphine signals not be another chemical with the same absorption properties right now we don't have any there are not any chemicals with the same absorption properties that are also present in the venous atmosphere so we have carefully carefully done our very best to rule that out and at radio wavelengths most signatures of molecules are pretty spread out so it's not super easy to have another molecule at exactly the same space same place and then lastly would it be possible to return a sample of the venus atmosphere back to earth for analysis um you know to test that atmosphere very much like we saw the landing on an asteroid yesterday right the landing the asteroids scooping up material so technically we could figure out if we had enough money and time to go to venus and come back but it's really hard to come back because you'd go to venus skim through the atmosphere and you're already getting kind of entrapped by the planet's gravity and your spaceship would have to have enough fuel to then zoom back out and get back to earth so we could do that but there are incredibly sophisticated small instruments that have been developed primarily for mars that we could take to venus we could get the liquid droplets we could concentrate ingredients and we could use the instruments to see what is there so it's far more likely that that in-situ exploration will happen rather than the harder part of returning a sample you'd have to do some work anyway to concentrate the because if life is there it's probably incredibly diffuse so you couldn't bring back you know like a giant huge massive amount of air you'd have to still concentrate it anyway okay so now on to some more philosophical personal questions how do you explain the importance of your groundbreaking work to your sons when they are under 10 and that comes from heather right so right now by the way my sons are now teenagers 15 and 17. so they they've been somewhat spoiled because they've been to three or four rocket launches they've seen the solar eclipse when it came here to america a few years ago they've seen the green flash the blue flash the meteor shower so i'm not sure if i was able to or even wanted to explain the significance of them when they were children i just kind of let them you know find their own way ask and answers their own questions it almost might have been there to embed it in in the in the field of astronomy to even really understand you know how how significant it is i remember one time going out for dinner with a friend and telling the kids you know she's a black hole astrophysicist do you have any questions about black holes and a lot of our social events were with other astrophysicists so i think they had a bit of a skewed view of or they really just took stuff in by osmosis right then a very philosophical question does an event like a pandemic make you sarah even more interested in the universe or the galaxy which is so enormous um you know much bigger than us and this virus or does it make you less interested because of the urgency of our problems on planet earth seeming so enormous that's a good question too a very challenging one i think for everybody i'll have to say that both actually so there are days when i i think i should just drop everything and focus on our own problems here on earth because they're just big problems and growing you know it's not just the pandemic it's the climate it's overpopulation and all of these issues you know are probably somehow intertwined so it's definitely a tough one on the other hand i love outer space and it really helps to give us a sense of perspective you know that that it's really sad but no matter what happens here on earth we could destroy ourselves destroy the human race destroy the planet earth will survive it will still be here a billion years from now so i don't know if that's sort of cheery or depressing but the other thing i always try to keep in mind and it's not necessarily saying that about my own work but pure science is really needed to make huge improvements elsewhere if you think about like antibiotics or lasers that we you know use for laparoscopic surgery or gps we all rely on now you know all the ginormous advances were from people doing pure science you need so much pure science to happen just to get these these important advances so i try to kind of keep a mix of all those three things in my mind okay right so on to some more you know questions about methodology um from villi since the transit method only works when the orbit of an exoplanet lines up with outline of sight what percentage of exoplanets do we think we are not seeing we are not seeing most exoplanets actually and we have a formula for this that the probability for a planet to be transiting is the size of the star over the planet's distance from the star so if you were my class i could give that to you as a assignment for like a little break but for a planet very close to a sun-sized star the probability is 10 to transit so that's pretty high i guess we're getting 10 of all planets it's not exactly that but about that but if there's a planet at earth's distance from a sun-like star only one in 200 will show a transit in that case we're missing most of them so on the whole it's very few that that line up properly which is incredible you know just the thought of what is out there right so give this is from brian given the hubble space telescope resolution how far have we been able to search for life and will we be able to search further say out to andromeda that's a good question actually so you know there are despite the fact that our galaxy has hundreds of billions of stars and yes we have these you know here in the northern hemisphere we can't see the the androme we can't oh we can't so i was thinking of magellanic clouds um we can only find planets in our own galaxy right now so it's nearly impossible to find planets in andromeda in the magellanic clouds anywhere else and so if we can't find them we can't search for their signs of life in the atmospheres now it's even more difficult actually because when we think about searching for signs of life we need a bright host star we need the planet the star to be as close to our earth as possible because the signal is so weak we need enough as many photons as we can get so it's not even that we're not searching another galaxy we're not we're only sieging our own neighborhood this would be like you knowing that there are billions of people all around the globe but you can only meet people on your block and the two surrounding blocks which is that's insane okay from camille is there any correlation we can make between possible phosphine detection on venus's atmosphere and the most recently possible tech possible detection of glycine in the venus atmosphere could the presence of these give further clues for possible life on the planet they could give possible clues we're still trying to sort through all the new results on venus that are coming out so we need some more time for synthesis okay from jose most exoplanet transit surveys are heavily biased to finding hot jupiters or planets orbiting close to this their host stars with relatively short periods if one was looking at the sun from another star earth would only transit once a year are you aware of any surveys in the future that will do long-term observation in the order of years of the same part of the sky to try and find these exoplanets orbiting far from their host stars that has to be one of my favorite questions because it's about one of my projects so let me explain a little more it turns out that the kepler space telescope which is now retired it stared at one part of the sky for four years and so kepler was able to find planets with periods over three years so that has happened already and you can look that up and kepler found small planets it didn't find an earth-sized planet around a sun-like star but it couldn't uh it had some problems and couldn't reach that there's the test mission tess only looks at a strip of the sky for a month there's a mission coming up called plato run by issa and plato it won't look for many years but it will look for six months or longer at one given field so to describe to you one of my projects our goal is to put up a fleet of small satellites little telescopes and each telescope would look at one bright star a bright sunlight star and it would look at this star for a few years looking for a transiting earth an earth-sized planet in a earth-like orbit about a sun-like star and when the star would go behind the sun the telescope would not be able to observe it but there'd be lots of telescopes able to pick up where one left off if needed now my project our prototype we called esteria was a cubesat in low earth orbit that launched in 2017 and it survived for two years demonstrating technology of how we would point a small satellite extremely precisely in order to be able to monitor a star with enough precision to find another earth so we we managed to get that done so the short answer is no there's nothing longer answers there's a few things in the works so look out for those right there's some general questions from carol why do dwarfs have more and larger flares than our sun okay just a second um so m dwarfs actually um they have more activity because okay that that's a good question i have to sort of collect my thoughts it's one of those questions i should know the answer to but i don't have it on the tip of my tongue right now so m dwarf stars just have more activity than our sun than our um sun and other stars they um just have a more active phase they have more convection and yeah i don't have the specific answer for you okay all right then um some questions from vayner do you plan to make use of spacex um or elon musk's funds we all wish we had access to those search for outer space live so we'd all love to get access to elon musk's funds actually he we have already benefited from elon musk the test mission launched aboard a spacex falcon 9 rocket and the price tag was significantly lower actually with his rocket than other rockets that existed that could have carried tests outer space so as long as he can keep his prices down we're already benefiting of course we hope in the future he might throw in a free launch to one of our projects but we'll have to wait and see while he's launching styling right then from sonal um a curious question she said what is the possibility that life came to earth from meteorites or distant comets well people love the idea of panspermia that life originated somewhere else and came to earth from you know by delivery from the outside and by the way that's one of the theories for venus there's the question on how did you know could life have originated in venus's atmosphere people like to speculate that perhaps it somehow came from earth aboard a meteorite but on earth it didn't have to you know we don't need that theory we know that our earth has had and has all the ingredients for life so we usually don't fall back on that idea okay and then the last question which i think you probably received many times also from vanant is if there is life outside of earth why haven't we already made contact with that so i don't know if you want to talk about the nature of life i think the person each person here could have their own answer to that really i'll just give you my favorite one because i love to imagine that there actually is life and intelligent life out there because the idea that perhaps there's no life at all it's just in no intelligent life is just really it's just a lonely thought so my theory that i like is that i liken it to ants you know i'm sure you've each had an ant invasion in your home or you see them outside sometimes you see like hundreds of them all clumped together those ants are pretty sophisticated you know they send some ants out for reconnaissance if they find a bit of cat food or something then a whole lot of them come flooding in but i want you to imagine for a moment you're going to talk to those ants like what would you say to them could you communicate that we have found a signal of phosphine on venus like how would you explain the universe to those ants so i love imagining that the intelligent aliens that are out there are so beyond us as we are to the ants they are to us and there's just not really any point they have no motivation to come and visit us because it's just we're just not ready for them as neil degrasse tyson says you know why would they come looking for us anyway right so that brings our question um session to a close i am going to um sarah while you think about your two favorite questions just encourage our audience i think is how you pronounce it especially who asked about the asteroid that's due to you you know to hit the earth the day before the u.s elections that's actually asteroid 2018 vp1 and i could tell you more but i'm going to encourage you to reach out to the south african astronomical observatory one of the telescopes nasa telescopes actually looking out for asteroids you know that might be on the collision course with earth which is called atlas is actually stationed at the sao as well as other stations around the world so reach out to the sao um you know and if you have any other questions about what sarah talked about today or just astronomy and space sciences in general reach out to your local observatories you know reach out to the media houses that talk about astronomy um quite often and ask them all these all these important questions sarah do you have winners for your questions i do actually so the first winner which i'm going to give my memoir to is to camille because first meal asked a lot of questions but i love the question how does can life originate live and die all in the atmosphere of venus or any atmosphere and for the technical question and i just i hope the book is not too technical but i'm going to give that to jose who asked about are there missions in the future that could look at a part of the sky for very long time because that was a very astute question you know sort of built off the one about are transits rare or not and how will we get to those rare ones that are far from the star and don't transit very that don't have very many planets that are actually transiting well congratulations to those two for the questions so what i am going to do in um if i'm able to is just in the panelists and attendees for camille and jose is just to put an email address which is for the manager of science africa and if you could send your details to freddie he will you know make sure that that everything is coordinated and that you receive your signed copies of those two books so that brings um to close our session today with sarah sarah i know that you're in great demand at the moment in terms of public speaking and science communication thank you very very much for making time for our colleagues and our audiences in south africa but also around the world we really do appreciate the time that you've given us and good luck in your work with the breakthrough initiatives thank you so much all for attending and i'd like to finish by congratulating the south african astronomical observatory for you your 200th year anniversary congratulations from all of us in the astronomy world right that ends our session today thank you very much everyone i used to operate too right you

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Length: 67min 30sec (4050 seconds)

Published: Thu Oct 22 2020