Chris McKay (CM): Thanks Margarita, it’s a pleasure to be here. I am going to try just speaking because the acoustics in this room are pretty good. And if I put my mic' on I'll trip over it, fall off the stage - it will be embarrassing for all of us. It's safer this way.

Well what I want to talk about tonight is the prospect of sending, bringing life to Mars. Tomorrow in the Geology department I'll give a seminar about searching for evidence of past life, looking backwards in Mars' history. Tonight I want to look to the future of Mars' history. And first let me - I am from NASA, I have to show a NASA-style view graph chart we all can show. And I am showing this for a reason: NASA is starting a program, which is called "astrobiology". And astrobiology is got in the announcement that Headquarters put out they listed six questions. That they were calling for proposals to address those six questions. And the first five questions were the same old hat. Things we've been doing, not that they weren't good. Its good that we're doing these things, habitable worlds, living systems, the origin of life, recognizing other biospheres, understand the history of the Earth, understanding the effect of humans on the Earth in short time scales. Those five questions were ongoing programs within the agency. The things we have been doing for decades. Good things and they are exciting things. And I am glad we are doing them.
     But the last one was brand new. What is the potential for survival and biological evolution beyond the planet of origin. When the announcement, when this came from Headquarters I was so flabbergasted that the bureaucrats in Washington could have such vision as to look into the future and to ask the question. What it's, what it is going to be like when life expands beyond the Earth? I was stunned and I became a big fan of the program. And we have been pushing very hard to emphasize this part of it because I think this is the first time NASA as an agency has looked into the future in the sense of life leaving the planet. What does that mean? And I think that’s very exciting.
     The future is, the past is exciting but the future is always more exciting because we are going to eventually experience it first hand. And so that this is the context in which I am now trying to frame the question of life going to Mars. The question of bringing life to Mars is part of a broader question of what is the future of life on Earth. What is our, what is our role as humans and as life from Earth. In a more general sense in the cosmos, do we have a role and what is it? And that's the question. I think Mars is the first step in answering that. So what I want to do is address that.

How are we approaching that and what does it mean? What I would like to do is keep it informal. If people have questions or derogatory comments or editorial that they want to insert let's just do it in real-time and keep things informal. I am going to have to give a little background on what we know about Mars and it's history.

We always thought that Mars was the planet that was most likely to give us information about life and which is why in '76, years ago Viking landed on Mars to search for life. It had a robotic arm it took some dirt did some simple biology experiments and basically found that the surface is dead, "Its dead Jim!" was the main result from Viking. Why is Mars dead?
     Fundamentally the reason we think Mars is dead, the reason we are willing to extrapolate from this one little hole in the sand to the whole planet is that nowhere on Mars today do we see water in the liquid form. We see water as vapor, we see water as ice, but it's never as liquid. Fundamentally the reason is that the pressure is too low. Water on Mars behaves like dry ice does on Earth. And one lesson that we know about life on Earth is that it requires liquid water on a planet. No liquid water on a planet, no life, that’s the end of the story.
     And if that was the end of the whole story Mars would not be a very interesting place from a scientific point of view. But we know that billions of years ago Mars did have water. Lots of water. This is, these images like this one here some three hundred and fifty kilometers across showing well developed dendritic channels flowing downhill, evidence of a low viscosity liquid flowing is the best evidence of water we have anywhere else beyond the Earth. This is it, this is the closest we came to finding evidence of life beyond the Earth, is evidence of water. Water being a critical part of life. Up to this year that was the best picture we had from Mars for the case that the liquid which carved these channels was indeed liquid water. Now we have even better images from Mars Global Surveyor. This is a canyon, sort of a mid-sized canyon on Mars it's about two and a half kilometers across about the same size as the Grand Canyon in Arizona. And just like the Grand Canyon in Arizona we can see what looks like a channel, a river channel in the bottom of the canyon. Telling us, showing us a process that’s very familiar to us here on Earth. A small river flows over a long period of time and carves a big canyon. It's not something that happens quickly, it indicates long sustained flow of liquid water. Mars had water. It had water a long time ago. It had water when the Earth had water when the Earth was first forming. And that is the focus of the scientific interest on Mars is this comparison between early Earth and early Mars.
     We know that early Earth had water, dry land, volcanoes under a thick CO² atmosphere. We think that at the same time Mars had the same features, thick CO² atmosphere, liquid water, dry land and volcanism. And we know that at this time when they were similar Mars had life. So our fundamental science driver and the reason we have more missions to Mars than all the other planets put together is the search for Mars' early history and the evidence for life there. And to understand what Mars was like when it might have looked like this three and a half billion years ago. This picture by Michael Carroll, many of you I am sure have seen, is a representation of the amount of water required to explain the channels that are observed, placed on the current Mars topography. So this is a realistic rendering of Mars with it inventory of water. Clearly when you look at this picture it must remind you of Earth from space, the famous blue marble pictures. And that’s the point, this picture is really the quest that we are on to understand Mars when it was like Earth when we had two blue marbles in our solar system. And the particular question is to see did it have life when it had water since we know from the history of Earth that life appeared very quickly after the formation of the planet. Did the same thing happen on Mars? So that’s the underlying story.

It's a compelling story and I think it’s the story that’s going to take humans to Mars. I think that’s the scientific story that’s going to be the attractor that’s going to bring scientists, humans to Mars that are going out and study, study the planet. And then that leads to where does it go from there? Humans go to Mars for a variety of reasons, they will probably set up fairly self sufficient bases getting their resources of air, water and food from the environment. And it's logical to ask what does that lead to in the future. So this is this is up to now everything has been in a sense an introduction. Now we get to the heart of the matter what is the future for Mars. I have been saying that Mars is a planet with a past, a very interesting past, maybe a biological past. We have some understanding of how it might have got to the cold dry state that we see today. And the question is, could we bring back the warm environment that it had in the past. Could we do CPR on this dead planet, just recently dead planet, only three billion years. Does Mars have a future? Well that’s what I want to talk about tonight. Could we bring Mars back to life or could we bring life there. Let me put in a short footnote here. Even though it would be great to think that there is life still on Mars in a dormant or sub-surface form. But unfortunately an objective look at the facts leads me and many others to think that there is nothing alive on Mars today. Nowhere on the surface and nowhere on the sub-surface. For a variety of reasons most of which trace back to radiation killing any dormant stages over billions of years. So unfortunately we think Mars is lifeless. So what we are contemplating is the notion of bringing this lifeless world back to life, sharing with it the genome from Earth.

Questioner (Q): Sir, does that include also bacterial life?

CM: Including bacterial life.

Q: Why are they worried about the contamination issue then? Bringing samples back to Earth?

CM: Because we are not sure that it's dead. The question is if we think Mars is lifeless why do we worry about bringing a sample back to contaminate the Earth with Martian life, if we think it's lifeless. And it’s the difference between thinking something is true and haven proven that it's true. The difference between a logical certainty and a demonstrated fact. We think that Mars is lifeless, that is not a demonstrated fact. And bringing a sample…

Q: But that coupled with previous experiments that sampled the ground in surrounding areas, because, same thing right?…

CM: Well previous missions we haven't brought any thing back. We have only investigated Mars. The vehicles that went there were sterilized so that we wouldn't get a false positive from an Earth organism. But brining samples back we will keep them in containment. Well how do we, what is the fundamental reason we think this is possible. I would say there is two reasons. One we can look back at the past and see that Mars had a habitable state years ago. We don't have to imagine something completely out of whole cloth to make it habitable once more. And secondly when we look at Mars we realize that the fundamental challenge to make it habitable is to make it warmer and we know how to warm up planets, we are doing it on Earth. Its probably not a good idea to be doing it here on Earth, but we know how to do it. We can point to what we are doing on Earth and say, hmmm I wonder what that would do if we did it on Mars. Now I'm talking about Mars and you can say what about other planets besides Mars. And I think the simple back of the envelope calculation shows none of the other worlds are even close to being habitable. None of them. None of the others can be made, this is Venus. Trying to spin up Venus it's ridiculous. Human, human civilization does not have the technology to alter any of the physical properties of the planets. We can alter the climate of planets and then only in certain cases. And Mars happens to be one of those cases. Mars is just within the capabilities that we have. None of the other planets come close. Question there.

Q: What about Europa?

CM: Europa is one of those planets that could have water, could have life. But making it habitable for Earth like life and any resemblance to the Earth is just beyond out technology. It’s the surface temperatures of Europa is something like minus 100 centigrade and it's got no atmosphere. So it's hard to imagine it as an Earth like planet in any stretch of the imagination. Titan probably after Mars is the best candidate. But even that the temperature on Titan is 95 Kelvin right now, minus 180 something centigrade. It's very cold and if you calculate just how much energy is required to warm it up you have to postulate something like cold fusion actually working not just cold fusion but cold fusion working and then you can imagine Titan warm enough. So all the other planets are way beyond our technological capability, you have to get into antimatter and what not. So Mars is the candidate. Question here.

Q: Do you have an idea, the way you are proposing to heat it is to trap heat that is coming from the sun right?

CM: Well you haven't seen how I am proposing, that’s five or six slides down. You have to bear with me.

Q: OK, OK.

CM: I didn't want to - OK. Let me get to that, because I give a lot of information on how we're how I propose to heat it up. But first let me talk. Before I talk about how to heat it up we have to define where we want to be. What does it mean to be made habitable? We imagine warming up Mars, making it look like this, what does that really mean? And it's important to keep in mind that even looking at the Earth we realize that there is two distinctly different habitable that the Earth has experienced in time.
     Throughout most of Earth's history the planet was not like it is today. Throughout most of Earth's history Earth had a thick atmosphere. Like this case with a little bit of nitrogen and a small if not negligible amount of oxygen. Through most of the pre-Cambrian Earth's atmosphere was not breathable by humans. It was dominated by CO². That is the original atmosphere of the Earth and in fact human beings are bringing back the CO². We are restoring the Earth to this original condition, the environmentally correct environment on Earth. And this is important because this is the way the Earth was, this is the way Mars was. The atmosphere on Earth today is the second habitable state. A thick one with an oxygen-nitrogen atmosphere with CO² kept low. If CO² gets above about 10 millibars it becomes poisonous to humans. Nitrogen has to be high enough to provide a buffer gas and oxygen has to be high enough to breathe. But there is at least two distinct states that we can imagine when we warm up Mars that we get. One is a, one is good for plants and microorganisms that is like the Mars as it was billions of years ago. If we just bring back Mars to life. Just literally bring it back to the way it was we would have an atmosphere like this and that would be good for plants and animals. But it would not be so good for humans. Humans would still have to be inside the bubble. I'll come back to that because, jump a little bit ahead because that looks like it's easy to do. It's easy to bring Mars back to the way it was. Making it so that you could take away the bubble on the humans, two the second type of atmosphere is a little more difficult. And many reasons it's a lot more difficult is because human beings and animals in general have a very low tolerance for CO². CO² above small levels acidifies the blood, basically turns your blood into soda pop. It's not a good idea and a, it's a, and this just shows that in detail. This is the, what happens if you expose people to CO², they can take fairly high doses over short periods of time, above levels of here you get dizzy and become unconscious and that level decreases over time. So you can take a high dose over short periods of time and a longer lower dose for a longer period of time and a long term dose of no effects is down here. The dose of adaptation is there and any thing higher than that would be toxic to humans and most animals. And so that puts a limit on what you can imagine as a breathable atmosphere for human beings. You can't have CO² very high, if the CO² is not very high it's not very warm. Which means you have to keep making these other super greenhouse gases. And I'll come back to that point later. But what we have to keep in mind is the distinct differences between a CO² Mars and an oxygen Mars. Two separate worlds and they represent the separate histories of the Earth. The oxygen Earth we have today and the CO² Earth that existed in the pre-Cambrian before the transition of oxygen. So that defines the end states, where the two different possible types of habital Marses. Mars of CO² and Mars with oxygen. The next question of logic is, is there enough material on Mars to build those worlds. Either of those worlds or both of those worlds. Are there enough bricks to build the building because atmospheres are big things. It isn't possible with current technology to carry one from one planet to another. Just the amount of mass required to carry the nitrogen say to build an atmosphere on Mars from Earth. I did the calculation, is something like a million million, a million times a million shuttle launches. It's just ridiculously big. No way congress would go for it. Even if the democrats were in congress. So we have to rely on Mars to have the basic elements there already. We really don't have the technology to move planetary scale masses around. So it's important to look at the inventory that’s on Mars. But, but what do you need to make a planet. Well then, here is one estimate. The amount of carbon, nitrogen and water needed to make a biosphere I put up here, Carbon dioxide in current un of hectaPascals, millibars is the same thing. Nitrogen as well, and water in equivalent layer of water covered over the planet. These numbers are all small compared to what the Earth has of each of these gases, but they would do the job. If Mars had this much of all those three essential elements, C, N, carbon dioxide, nitrogen and water that would be enough. Well what we know for sure is what's in the Mars atmosphere which is this line right here. Its nowhere near enough we know this. Mars atmosphere is nowhere thick enough to support a biosphere. But we think there is a lot of these materials tied up in the crust and in the polar caps. As ice for example as nitrates as carbonates and as absorbed as CO². But how much do we think that could be tied up that way? Well the estimates vary a lot. This is the case where we don't have any data, Where we have a lot of theories and the theories are all over the place. But the theories allow for there to be as much as is required in all cases. So it's likely and not just because it fits but for other reasons, I think the best guesses are on the high end. That we think that Mars has enough of these volatiles to sustain a biosphere, that they haven't escaped to space. There are reasons we think the amount that have escaped to space are small and that there is probably enough water trapped as ice, nitrogen trapped as nitrates and carbon trapped as carbonates or even better as frozen ice or absorbed in the regolith to create a biosphere. So we think that Mars has the right stuff. It has the material needed to create a biosphere. Now we come to the question how? How do we warm it up? We know where we want it to be. We know that we think it's got the right materials. How do we warm it up? It goes with the question how are we warming the Earth with these super greenhouse gases. On Earth with out even trying we discovered gases that are thousands of times more efficient at keeping a planet warmer than CO². And that they have long lifetimes in the atmosphere and so they stick around for a long time. There is almost as if we were designing a way to warm up the Earth. We couldn't have done, almost couldn't have done a better job. These gases some of them are shown here. Many of them contain chlorine, bromine and fluorine are gases that can a thousand times more efficient than CO². Here is the temperature increase due to a part per billion of these gases. Just a part per billion, trace levels. Imagine if you put them in at a part per million, which would be a thousand times bigger. These changes wouldn't scale by a thousand they would change roughly by the square root of a thousand. But still the square root of a thousand is thirty. Point two to point one degrees times thirty is 3 or 6 degrees. For a part per million we get on the order of ten degrees warming for one of these gases. That’s a big effect for a part per million. These gases are great for making planets warmer. Some of them unfortunately have side-effects that we don't want. Like ones with chlorine. Chlorine ultimately destroys ozone, we want ozone on Mars. No planet should be without it. So we wouldn't want to use these, but some of them don't have chlorine. Some of them are pure fluorine compounds like CF⁴ for example. One can imagine putting those together and coming up with a mixture that would keep a planet warm. Let me just show in more detail as the question came up, how they, how do they work. They work by blocking the infrared radiation going out from the Earth. This is a kind of technical plot, but it's a useful one. It shows the infrared radiation leaving the Earth is this solid line here, the line that goes up and down. And you can see that not much radiation leaves in this weird region. Or in this region because it is blocked by CO² and here it is blocked by water. But in this region, here a lot of radiation leaves the atmosphere. This is what's called the window region. It’s a hole in the blanket of the Earth's atmosphere in terms of keeping energy in. It would be like having a blanket with a hole in it. And that’s the main way in which the Earth loses its heat that it receives from the sun is by streaming out from this spectral region. 800 to 1200 wavenumbers or 6 to 10 microns. That's the way the Earth is cooling. If you could plug up the hole in that region then you could block heat very effectively. And these gases have strong absorptions in those wavelengths regions. And that's why they'd be so good at warming up Mars. So we've done some computer calculations as to what we would have to do to warm up Mars. How much of these gases would we have to add to Mars to make it warmer? And this is the dotted line shown here that if you add these gases to Mars the temperature starts climbing. And you can crank it up from 217 up to 20 to 30 degrees warmer. Warm enough to trigger the melting of the polar caps and release the CO². CO² is not a very good greenhouse gas by comparison, but its free, it's there, there is a lot of it. So if you can warm it up with these other gases and enhance the release of CO² you create a thicker atmosphere and a thicker atmosphere will release more CO². So that's the general scheme. And I don't know if that answers your question but may be now is the right time to ask a question in terms of Warming up. The scheme is to release these gases to make them on Mars. Not to carry them from Earth. Make them on Mars and have them, the warming from those gases generate a feedback effect which releases more CO².

Q: There are two questions, the first question I was going to ask earlier. Mars if I remember correctly is at two eighty…

CM: One point five.

Q: One point five.

CM: Two.

Q: So you have about a third the size.

CM: Half the size.

Q: Half the size and you have it would take a little longer to heat up than Earth. The other question is how do you prevent it from going past that?

CM: Good question. The first question is, Mars is one and a half times further from the sun and so it does get less sunlight. You can calculate how long it would take if you introduce these gases for Mars to warm up if it had an efficiency of trapping solar energy of about ten percent is what we would expect for these kind of processes. The answer is about fifty to one hundred years. So it's not a real long time. It's not astronomically long. And it's the second question is could once you started this process of warming where would it stop? And the answer is it wouldn't stop until all the CO² came out, out of the soil and regolith. So you can't it's like opening the floodgates it's just what ever is there comes out. You warm up the planet and all the CO² will come out. How much is there is the key question. We don't know yet the answer. The current estimates is that there is only probably about one hundred to two hundred millibars of CO² exchangeable in the polar regolith or in the polar caps. Which would not warm Mars completely to Earth like conditions. It would warm it sort of Antarctic-like conditions. Which are pretty comfortable actually compared to present Mars. Minus twenty is a good deal warmer than minus sixty. You probably get minus 20 here occasionally, if you got minus sixty you would all move to Florida or something. So minus twenty would be a good step forward. So it's unlikely we would be in a situation where it would become too warm. Where there is two bars of CO² and it would come out with three bars or a Venus like state. But we don't know that and so certainly one key question is to determine the total inventory of CO². Question here.

Q: Yes how long do these gases last?

CM: These gases, the criteria you would pick for which gases for which gases you would use to warm Mars. Could be first the elements that you make the gases out of would be available on the surface. To make the stuff there. Sulfur, fluorine, carbon are all available. Nitrogen is not readily available and hydrogen is relatively hard to get to. So sulfur, chlorine and fluorine are the molecules you put together. The second criteria is that they be good, very good greenhouse absorbers. And the third criteria be that they have long life times in the atmosphere. That the bonds that hold the molecules together are strong bonds. So that they can resist UV radiation and for example C, carbon tetrachloride has an estimated lifetime of about five hundred years in the Mars atmosphere. So as long as you are trying to maintain a warming you have to make them fast enough to replenish them over a five hundred year time scale. Now if enough CO²came out of the polar cap and the ground then you could stop making them and Mars would stay warm with that thick CO² atmosphere. But if you lower the CO² down to the levels that would be breathable by humans then Mars would be too cold unless you resumed making those gases. So a oxygen atmosphere is not warm enough because Mars is further from the sun and must be supplanted, supplemented either by super greenhouse gases or by CO² levels that are above the toxic level. Question.

Q: Mars' atmosphere is about one hundred kilometers?

CM: What the thickness?

Q: Yes.

CM: Well it depends on how you define thickness. If you were to take the Martian atmosphere and compress it into a layer at the same density as the current surface it would make a layer about ten kilometers thick.

Q: I suppose to the limit where it loses quite a bit to space, if you added some of those super gases would some of those escape the envelope of the atmosphere?

CM: No, not really. No the point the top of the atmosphere you define the top of the atmosphere as the point where the mean free path is long enough that a particle can be on an escape trajectory. The exophase as it is called. That is still very high and as the atmosphere went up in pressure that base would just move. The whole atmosphere would just move up to a pressure level and it would move up as well to a higher level. Question.

Q: Is the mechanism by which Mars first lost its original atmosphere still in place?

CM: Yes. That’s a good point. You imagine here to Mars and bringing it to a state was eventually it will run downhill again. We estimate that it took about one hundred million years for Mars to run downhill. So a hundred million years is a long time. It's a good thing to spread mortgage payments out over one hundred million years. But an interesting point to think about is that the Earth isn't going to last much longer than that. If we were to bring Mars back to like we would have say one hundred million years life expectancy. The life expectancy of the Earth from now looking forwards is not much longer than that. The upper limit of the life expectancy of Earth is only forty times longer than that. Forty times one hundred million being four billion years when the sun goes red giant. So as a factor forty at most, likely the Earth will become Venus like much sooner. May be as soon as a billion years due to the brightening of the sun. The sun is getting brighter with age as we do. Maybe some of us do. And the Earth will have a runaway greenhouse in typically a billion years. That’s only ten times longer than the life expectancy on Mars. So one of the lessons here is nothing lasts forever and it's just a question of relative scale as to how long it lasts. And one hundred million years is in the right ballpark. Question.

Q: [Unheard]

CM: Well that's a good question. Let me turn to the second part of the talk, which is, which I want to call ethical issues. It is particularly appropriate to talk about that here because I first started getting interested and working seriously on it with Bob Haynes. The late Bob Haynes who was at York University. In fact my previous trip to Toronto was to visit Bob Haynes. And this is Calvin my colleague, Calvin and it points that there are other issues as you were saying. The other issues besides just, Can we make Mars habitable?