So while. So welcome all of you to Oxford Physics from all of us in the Oxford Physics family, which numbers more than 1500 of us in Oxford. And this welcome is extended not just to all of you in the Merchant Wood Lecture Theatre here, but also in the adjacent lecture theatre. The Lindemann and many people that are joining us around the world live through streaming now. My name is in Chips and I've been head of Oxford Physics for the last 22 or so days.
There's less. Makes me an incredible extra nice. So this is why I'm writing the notes. So, as you know, physics provides the basis for much of modern society from the microelectronics that enable us laptops and computers to the vast array of advanced instrumentation that we find in hospitals that speeds diagnosis and facilitates cure. It's about a thousand students studying physics in Oxford at the moment, and they're pretty talented group, rather proud of them.
Three of them, Martin Rowe, Tony Leggett and Joe Michael Cosmos went on to win the Nobel Prize, and others have had a truly immense impact on our world. For example, Tim Berners-Lee invented the World Wide Web and the brilliant inspiration of Stephen Hawking. Physics works best when theorists and experimentalists work side by side to measure what is measurable and make measurable what is not so and to interpret those measurements.
We do all of those things at Oxford to learn more about a marvellous cosmos on all scales, from the subatomic to the entire universe. Tonight's lecture is the beginning of a new partnership with the Worshipful Company of Scientific Instrument Makers. To tell you about the company and a little about what they're going to be doing together. Please welcome the personnel of the company, John. Thank you. Good evening. I did have some notes here, but they've disappeared.
Fortunately, being a Boy Scout, I. I bought a spare set, so I was asked to keep it brief. So in six sentences I'm going to sell who we are, what we do, and why we are here. Peculiar to the first of all, we are. First of all, we are a trade guilds and peculiar to the City of London. We are also known as a livery company. There are 130 such livery companies in the City of London, each representing a trade profession or an industry.
And they support. And some of the old deliverers can actually trace themselves back to the 12th century. So there is quite a bit of history involved as well. We have three main roles. One is to promote the industry that we represent. So in our case, scientific instruments to support the ancient traditions of the City of London. You know, the Lord Mayor, the sheriffs, the aldermen and so on.
But perhaps the most important role that we have is to nurture our younger members who have shown interest in scientific instruments. We have to feed subjects for our industry. They are physics and precision engineering, and we try to keep abreast of the developments of both subjects. Hence, our relationship with the physics department here in Oxford.
As Ian said, this evening is the beginning of a new partnership between our West Company and the physics department here that will involve potential sponsorship and the holding of more joint events such as this this evening's lecture. So you can watch out for those. Membership of our organisation is open to anybody who has an interest in scientific instruments and there'll be more information available in the drinks reception afterwards.
So there we are. That's my six sentences and I'm now handed over to Ben, who will get things rolling. Thank you very much. One of Oxford's greatest strengths is its students. And so it's a great pleasure to introduce one of our students and astrophysicist Ben Fernando to introduce the speaker tonight. Please welcome back. Thank you, everyone, for attending.
Whether you're in this room or in one of the overflow rooms or watching online, we're delighted this afternoon to welcome Dr. Jim Green, currently the chief scientist at NASA. I had a substantial biography prepared to tell you all about the missions he's been involved in within our solar system and what he's working on now, including the time he spent as director of NASA's Planetary Science Division. However, he told me to keep the biography to two sentences. I think I've already gone over that.
So without further ado, I'd like to ask you to join me in welcoming Dr. Jim Green, chief scientist of NASA. Thank you very much. It's just a pleasure to be here in Oxford. And with me, I brought all the Nassar secret files and we are going to open them up and we are going to look inside and we are going to talk about where we really are in the search for life beyond earth. And we've made enormous progress. So to begin, I must first tell you what the definition of life is.
All right. We'll start with fundamentals. And about 15 years ago, we asked our astrobiology group that we just put together give us a definition of life. They struggled after a couple of years, a couple of conferences, debates. You know, they came back and they were so proud they'd actually distilled it. And the reason why I want to know that is I want to be able to build instruments and go out, measure it. Okay. And I said, okay, what's the definition of life?
And they said, Life has three attributes. It metabolises reproduce as it evolves. They were delighted. And I can't tell you how sad I was because I don't know how to build an instrument to make those measurements. So then I stepped back and we said, okay, let's grab the metabolism part of it. What do we need for metabolism? You have to have the energy source. You have to have the organics. You have to be able.
When you ingest food with water still to be a solvent and then and then eliminate waste. So then there are three ingredients that we could actually make measurements of. Okay, so now we're getting to know an area where we can do some things, the ingredients of life and then, oh, by the way, there's this pesky thing called time. Okay. You may have all the right ingredients that would form a habitable environment. But you have to have time to be able to have that spark, whatever that is.
And we don't know what that is. We don't know what it's taken to have to go from the right environment to have life. Okay. But if we can go out into the solar system and look for those things, we'll actually have a chance. But before we do that, I asked the astrobiologist, go to extremes on this earth, go to the driest deserts, go to places where, you know, the the acidity is huge. Or go to nuclear plants where the waste materials there and look for life.
Tell me if there's life in those regions. And they did. And it's all over the place. And the fundamental thing about it is where there's water, there's life. Now, they also went into deep mines. Two miles below the earth. And where there was water, there was life. And so we now know. Much about our biosphere. There's more. Biology below our feet in mass. More biomass of life below our feet than is on the surface of this planet. And so during times of extreme life moves into the rocks.
Okay. So those are really great attributes. Those are things that we can go after because we see extremes in space. Okay. But there's another dimension. We live on this planet. This planet is 4.6 billion years old. And it hasn't always had life. All right. It's gone through enormous changes. There's been five mass extinctions. We need to also look at this time dimension. Okay. And to look at the time dimension we really need to look at. How bright our sun is and what is our sun doing?
What is the evolution of our star? So since the sun came together 4.6 billion years ago. It has brightened. In fact, we believe the luminosity may be as much as 25 to 30% less back then than it is today. And so from an astronomer perspective, looking at stars and looking at the heat from the stars, they have defined a region around a star. Where the temperature is such that if you had an Earth sized planet.
With water. One could expect in this green area, this habitable zone area, water to exist in three phases liquid solid vapour. They defined that as the habitable zone. That was the first step in taking a look at where exoplanets are being found today, where there might be a possibility of life. I wish it was that simple and I think you'll see how difficult it's gotten. But I think we're also making a lot of a lot of progress in this concept.
But this was the first initial concept, a really good start to doing that. So then when we look at our sun as it is, increased intensity over time, that habitable zone that has moved out. So when we look at Mars and we look at Venus and we look at its past. And when it was in the habitable zone.
Where the conditions were such that that light from the sun could produce an environment where water could exist in those phases, and therefore life could have company that one sees then that it's only in the future where that habitable zone will eventually reach Mars. Okay, so maybe we shouldn't have looked at Mars for life. And that's one of the fallacies of this concept. We have to be smarter than just use the concept of a habitable zone to look at it.
All right. So let's go through our solar system, not only in the space starting from mercury, but in time. In time. And and compare what we're finding out with what this picture tells us of how the habitable zone moves outward. There's also another line in this area. It's called the snow line. Okay. And to visualise what the snow line is. Let's say you had an ice cube out at Pluto and you move the ice cube closer and closer to the sun.
And finally you got to the point where the lattice couldn't hold it together and the molecules were popping off, and that's called sublimation. And you go from solid to vapour. That's the snow line. Well, actually, it's a sphere around the sun. And that snow line today exists out in the asteroid belt.
And so from a planetary scientist perspective, when we approach these things at least ten years ago, the concept is, well, if there's water in the outer part of our solar system, it's going to be ice. It's going to be solid. Okay. Well, that's a real downer because we need some liquid water to be able to do this metabolism thing. And so we're going to have to watch what happens with that, too. All right. Mercury and mercury, indeed, is our our our first planet.
It's larger than the moon, but it's not a large planet. It has its own magnetic field. It's nearly tidally locked. And it's incredibly hot it out gases and from messenger data we believe we can determine that mercury really didn't have any substantial atmosphere. And therefore the probability of having life or liquid water on it is very low. So. So Mercury probably never had a chance at being habitable. We look at the next planet. What is Venus like today? Well, Venus is our sister planet.
It's as large as the earth. But indeed, the Russian Soviet Union landing on the venerable missions, looking at the atmosphere and the temperature. It's really hot. It's an extreme. Okay. It's where the surface is hot enough to melt lead. And the pressure on the surface is 90 times our atmospheric pressure. You have to go deep into the ocean to get 90 atmospheres. You know, the bathyscaphe could probably barely be able to survive it if we landed it on Venus.
All right. So this is a really tough planet. And with our Magellan data piercing the clouds and doing radar and getting an idea of its surface, you know, this planet is very volcanic. And we believe there's indications that it's still volcanic and still kicking out the CO2. Okay. Now has lost a magnetic field if it had one in the past. But it has this an enormous thick atmosphere. And and the surface tells us there's hardly any craters that have survived.
And it's resurfaced itself probably many times in its past with huge dome structures, some of which from our ISA spacecraft that have been at Venus indicate. These are hot zones. And so they may still be active or at least have been active in the last several thousand years. So without water. Okay. Venus also is not a likely candidate to day to day to day. And so our picture of Venus has been a timeline of its creation like Earth.
And then today and then and a lack of understanding of what happened to Venus over the last 3.6 billion years, right in the middle of its evolution. So we took some of the top climate modellers, those people that have been working out, you know, the greenhouse effect on Mars and understanding CO2 and its effects here on Earth. And they turned their attention to Venus because we made a critical measurement, and that measurement is called the D to H ratio. Okay. Now, D is deuterium.
Deuterium is a hydrogen atom with a neutron stuck into the proton in the in the centre of it. Okay. So it's a it's a heavy hydrogen called name of deuterium. And a water molecule could have one of these DS okay. H2O with with it with a deuterium. Now you can go in our ocean and you can bring out a slug of water and we can go through that and we can pull out all the water molecules that have deuterium in it. And we can former ratio so we know what the ratio is on earth today.
And now that we made the measurement of the age at Venus and the D is huge compared to the age, we then realise, Hey, Venus has lost the water. Deuterium in water molecules makes it heavy. Water molecules with just H2O are lighter and therefore they go up to higher altitudes and can be stripped away by the solar wind. And that's what changes the ratio. So let's put the water back. And so these modellers put that water back on.
They put that water back so that we can do the modelling in this in-between state. All right, we want to fill that in like we have filled in what our knowledge of the earth is. So for the Earth, using that same timeline perspective, after the Earth was created in it cooled down and it was bombarded with more material in a place in a time we call the late heavy bombardment, bringing a lot of organic material to the surface of the earth.
And in many of these asteroids and comets that hit the earth brought water with them. So a lot of water and asteroids, it turns out. And in fact, some some of us believe that perhaps anywhere from 20 to 60% of the water in our oceans today came from this bombardment period, came from exterior sources rather than interior sources. So that's hotly debated still. And then life began about 3.6 billion years ago. So right in the sweet spot where life began here. What the heck was Venus doing?
Okay, so we have the topography of Venus. We put back the water. We had the initial conditions of the Earth. But Venus is much closer to the sun. The sun was increasing in intensity in its early time, and we let the models evolve. But we let the models evolve. And this is what we found. Venus for perhaps as much as 2 billion years, could have maintained an ocean. And it's only been in the last 800 million years where the runaway greenhouse effect began to evaporate the ocean.
And because Venus doesn't have a magnetic field, gets stripped by the solar wind and changes the planet forever. So this tells us Venus could have been habitable in the past. Even though it rotates slowly. Clouds form. Huge cloud structures form at the sub solar point, reflecting that sunlight for long periods of time until it's overcome by the increased intensity. And of course, we don't exactly know the volcanic activity and what's happened, but that has to be factored into.
But these simulations are the start of some new concepts of Venus being habitable when Venus would have been in the habitable zone, as we've defined it by the astrophysicist. So today, Venus is not what we would call habitable, even though it's in just at the edge of the habitable zone. It's the habitable zone is it continues to move outward over time. The sun's intensity is going to increase. It's what our stars do.
And and it's been stripped of material like crazy, even though there's an enormous amount of atmosphere and it keeps getting dumped in. The lack of a magnetic field is stripping this atmosphere away. So this planet is going to evolve very, very differently in the future. Of course, here's our blue marble teeming with life. And as we talked about over its history, it's had quite a changing climate.
In fact, as a planetary scientist, I can tell you the climate has done nothing but change OC sometimes faster than at other times. So it's really all about the rate of change. And it has to do with a variety of, of, of how life has taken hold. How life has produced oxygen. And how that's changed the overall chemistry of of our atmosphere over time. But when we tease out a couple parts to the to to the earth and we look back.
We find that the Earth went through some enormous changes in its climate. There's two eras here. One at about 750 million years ago and another one at 2.4 billion years ago where the climate was so severe that the ocean started to frost over. We call that time period. Snowball Earth. Okay. And we have geological indications that the Earth went through this period. Snowball Earth. Okay. And and fortunately, life survived through that.
Earth looked more like Europa than it did the blue marble that we know of it today. But fortunately, life made it through. And right now, today, Earth has a very nice magnetic field that is protecting it against the solar wind. And it it is what we believe is an important element for the survival of life in the long run. Honour on earth. Let's go to Mars. So Mars is much larger than the moon, but certainly smaller than the Earth's by half the size of the earth.
All right. And it's a runt in terms of terrestrial planets. And it's a front because of Jupiter. It's a runt because of Jupiter. And in fact, between Mars and Jupiter is the asteroid belt. This is an area of debris, of material that's trying to become a planet. But it never happened. Making planets is all about the accretion process where objects collide and then they reform and then they collide with other objects and reform into larger and larger objects.
But in the asteroid belt, which is so close to Jupiter, these collisions occur, and then Jupiter pulls them apart because of its gravity. So the big guy on the block, Jupiter, is creating an environment where Mars is a runt and the asteroid belt is like going back in time and looking at material that's that. It's the very beginning of accreting going from going from Planetesimals to Protoplanets to then planets. And we have examples of what those those objects are. And we visited with Dawn.
We were at Vesta and Ceres, two major and members of the asteroid belt that are providing tremendous information for us. So we've had a number of missions at Mars. And so we can geologically tease out what's occurred over time on Mars. So in the very early stage, the No archaean. This is an area of time for which it's clear to us Mars had an enormous amount of water early on in its history.
Early on in its history. In fact, two thirds in the northern hemisphere, we believe, was under water at places it was a mile deep or more. Okay. And then it went through. Rapid climate change. Now, we don't know exactly why. We have some indications of that. Perhaps along the way it had a magnetic field and we know it did. It lost that field and the solar wind started to strip that that field away. We're not quite sure. But today it's very dry and arid.
Okay. The pressure the pressure on Mars is about 1% or less than the pressure here on Earth. Now to give you an indication of the size of the ancient ocean. This is a mercator map of Mars, and it shows where our what we've landed on Mars successfully that interrogated it, looked at it. And the blue areas are the lowlands. This is where the water would be. And the red and the white areas are the high elements, the the high features on it.
And so, as you can see, significant part of the northern hemisphere is where the ancient ocean is. And a lot of our missions are going right to the shoreline of the ancient oceans. Those places where life may have started. And and indeed, curiosity, which you can see right over here is is in Gale Crater. We're about ready to land another mission. It's called Insight. And Insight is just a few degrees north of curiosity.
Insight will be in the ancient ocean. Curiosity is in a crater called Gale Crater. Gale Crater, which indeed its rim was breached with water from this ocean pouring into the crater. And so when Curiosity landed. And began to drill into Mars and then allow us to take that drilled filings and bring it in and then tease out the mineralogy, tease out the chemical composition. The first thing we saw, which for many of us, and I'll be the first to admit I was one of them.
I was shocked. When we drilled into the ground, grey material came out, you know, that this oxidised surface right below the surface is what Mars is really like in its past. It's grey Mars. And those soils we brought into our instruments and we measured them. And they had carbon hydrogen, oxygen, nitrogen, phosphorus and sulphur. That's all the elements we are made of. It's all the right stuff. And it's sitting in a region that was full of water.
And in fact, the sediments in this in this area that we can tease out tells us the water. If we went back three and a half to 3.8 billion years, we could drink it. If we brought microbes and put them in there, they would have survived. So Mars, its atmospheric pressure was much larger to be able to support water as a liquid. The heat had to be extensive compared to what it is today. One day on Mars is a change of temperature of about 170 degrees Fahrenheit.
That's one day. It's an enormous change. It's not like that Mars is past. Mars was a blue planet. When Earth was a blue planet. When Venus was a blue planet. All three of those planets early on in their history had plenty of water and had environments that we would call habitable, whether they were in the habitable zone or not.
And so we recognise how complicated this system is and it requires knowledge of the atmosphere, the knowledge of the composition, the knowledge of energy input, and the ability to maintain an environment that would provide us liquid water. So what's happened to Venus or sorry, Mars over its history is now being teased out by a spacecraft called Maven. So Maven's been or orbiting Mars now for several years. And that solar wind is just ripping the upper atmosphere away.
In fact, we see what Mars actually from Curiosity is actually fairly human. There's a water cycle on Mars. It's it's not like anything like ours, but it's measurable. Okay. It snows during the winter again, not just CO2, but water. We believe that under certain conditions, craters that have opened up aquifers, that those aquifers weep when the sunlight has sublimated the ice plugs and the water pours down the crater size.
The length of the crater. And we measure those and they're all over the place recently with an E submission. We've teased out an underground lake in the in the southern hemisphere, which I think is the start of really looking at the underwater resources on Mars. It was, although Mars has lost its ocean. A lot of that water is into the ground and into the aquifer systems. And where there's water, there's potentially life. Now Curiosity is also measuring methane.
It's measuring methane above any background. And that methane is very cyclic. Methane can be generated by biology. Okay. And methane can be a biotic generated with olivine and and an intense heat and water deep in its core can generate methane that can leak out. And so we see blooms of methane coming from certain regions. Curiosity, which is sitting in this hole called Great Gale Crater. During the day, it measures methane. But the wind patterns during the day are leaving the crater.
And so the methane that's generated many, many degrees difference away aren't getting into Gale Crater. It's got to be leaking through the soils. So is is curiosity sitting over an aquifer where there's life and and methane is being generated is leaking through the soils. We don't know. Or it could be generated, Abiotic. We just don't know. So these are really exciting measurements. That tells us a lot different story about about Mars.
So what about the northern polar cap? This is a permanent polar cap. You can get its spectra and you can measure also water. So what we have is a veneer of CO2 over an enormous. Water ice cap. Okay. An enormous water ice cap. And here's the radar observations of the ice cap right here down in the corner, right hand corner. So you can see the the layers of material that's built up and it's huge. You know, some of these places that a kilometre of an eye of ice over very large regions.
It's a large amount of water with this veneer of CO2 that's actually keeping that water from sublimating. But what will happen over time? We've started model this. So if we increase the temperature of Mars. Okay. So here we have a time in the future. Where the temperature because the sun's temperature is increasing the heat. Mars will receive will increase and the ice. Dry ice, CO2 ice veneer will sublimate.
That will increase the atmosphere, which increases its greenhouse effect, which as temperature continues to rise, will melt the water. And one seventh of Mars is ancient. Ocean will return. We'll return. And it will look like that. Okay. So now we have. Our modern views of these planets and an inkling from the modelling that we've done of their past. To be able to see how they've evolved. Not in a habitable zone, but in a habitable state. Okay. Mercury never had a shot at it.
Venus, we believe, as it evolved, moved into a habitable state because of the water it had. But then due to a runaway greenhouse effect, it lost it. Earth almost popped out of a habitable state twice. Snowball Earth almost popped it out. Okay, but it managed to stay in a habitable state. We're now well situated in the habitable zone or in the habitable state. But over time, that must change. Due to natural circumstances unless we do climate engineering or something else.
But when Earth moves out of the habitable state, we better be on Mars. Okay, so Mars is moved through a habitable state. It's dry and arid, although a lot of water is trapped under the ground. And indeed, as we talked about, we envision through the modelling that we've done that it will pop back into becoming habitable. So this has really changed our view of how the terrestrial planets have evolved over time and where life exists or could have exist. So life on Mars may be just holding on.
Maybe tenuously there or not. It's a toss up, but it had plenty of time and the right environment in its past. To have had life. To have had life. So our plans are bringing back samples and interrogating the rock record, looking for why Mars went through the rapid climate change it did. And if we get lucky, might have some sort of indication of life. There are 4700 minerals you can define here on Earth, and three or 400 of them can only be done if you've got life.
So the rock record can tell us an enormous amount about its past. And we need to get it into our laboratories where we can study it. And we're on the cusp of doing that. The mission that's going to Core Rock will launch in 2020 land in 21, and over the next several years, NASA, ESA and some of the other agencies are getting together to bring those rocks back. And it will be critical because it will tell us everything about the past and allow us. To figure out its future and the future of Earth.
Okay. So I hope you see what I talked about that we are so lucky to have Venus. And Mars. Because what's happened on Venus can happen on Earth. What's happened on Mars can happen on Earth. Okay. Comparative climatology. Is critical for us to continue to do so that we can understand the fate of this planet. While we're understanding the fate of the sister planets that we have.
Another fantastic thing happened over the last several years, in the last ten years, in particular, completely changing the planetary scientists view of what goes on beyond the snow line. And that is we have found ocean worlds. Okay. Entire bodies with huge amounts of water around the giant planets. Now the giant planets Jupiter, Saturn, Uranus and Neptune. They have water in them. There's plenty of water out there. Okay. But to have it as liquid water, you have to go to the moons.
That's where we're going to be finding it. So if we go to the Jupiter environment, here's one of the fabulous observations from Juno of Jupiter. This is real, a real image taken from a really unique perspective. It's a beautiful planet. And we're teasing out a lot of a lot of things about Jupiter, and we know a lot about its Galilean moons. These are the moons IO, Europa, Ganymede and Callisto that Galileo saw in 1611. Now we have visited them. Now we understand them in many different ways.
And and it's just spectacular that what we have found out. There is a habitable state that exists. In this region around Mars and Europa is right in the middle of it. Okay. When we look at IO. IO is very volcanic. Very volcanic. Okay. And in fact, let me show you an image from Juno of IO. In the infrared. Okay. And. And there it is. At any one time, there are 100 active volcanoes on IO. IO is about the size of our own moon. This is not a small object.
It's a very large object. Okay. It's very volcanic. And that's because of the tidal forces. From Jupiter. These moons are in slightly elliptical orbits. And so as they orbit Jupiter, there's the Perry Centre. That's where it's closest to Jupiter. Jupiter squeezes it and then it moves out to its epicentre and the gravity is less. And so when you look at these moons and they get tugged and pull and squeezed, that heat is got to go somewhere.
Now, all these moons when they were created had a huge ice crossed over them. Io's ice crust is gone. Och, it it. It went. Billions of years ago. All right. But not Europa, Ganymede or Callisto. Now. Ganymede is our largest moon. In the solar system. In fact, it generates its own magnetic field. And there's indications that it has. And under crust ocean. Now we believe that ocean is deep, but it has communicated to the surface. We see the cratering record on Ganymede.
There's a lot of craters there, but a lot more have been covered up over time. And that's because when we look at Callisto. It also has a huge icy veneer over a rocky interior body. And perhaps it had an ocean of water in its past. But that hasn't come to the surface. This body shows us the impact rate that all these satellites should have had. And it is one of the most cratered objects in the solar system. And yet IO has no craters. Europa only has a couple.
You know, Danny made a couple hundred and millions on Callisto. Okay. And that's because these bodies have erased them. The ocean has communicated to the surface. Ganymede's too cold. IO is too hot. But Europa. You know, it's just right. It's right in a habitable state. So let me tell you what we know about Europa. Here it is. You can see the cracks, beautiful cracks. Coming from these cracks we now believe are huge geysers.
We now have measured these geysers from Hubble. Now, Europa is slightly smaller than our moon, so it has enormous gravity associated with it. And yet we have found some of these geysers going up 400 kilometres. Yeah, yeah, yeah. It's exactly what I said. Okay? I mean, I don't know of anything that. That's a wall of water that goes up to space station. I haven't seen that on this globe yet. And we think this is a water world. Okay. But we have flown through those with with Galileo.
And we recently discovered that data only because we didn't know what we were looking at at the time. But over time, as we understand what these signatures tell us, we can go back in the data and find it. And that's why Galileo flew through this plume. And it's clearly obvious that's what it is. It's got all the indications of it. It's unbelievable. And from Galileo data, primarily, we can tease out the size of this ocean. It has twice the amount of water than there is on this planet.
And yet this object is about the size of the moon. Okay. So it has an icy crust. With cracks where the ocean has communicated to the surface and is communicating now. It's done it in the past because it's eliminated its craters. And it's doing it now. And we see that with Hubble. We can't quite tease out yet what the circumstances are that open and close these cracks to allow this water to come out.
But with our next mission to to Europa called the Europa Clipper, it's designed to measure the ice thickness. I think we'll see the ice thickness anywhere from ten kilometres to right at the surface all over the place. Okay. As the ocean continues to communicate with the surface, there's even some indications. That as these cracks open up, the ice has to go somewhere.
There's some subduction of of that has been determined by some of these observations from Galileo of one ice plate moving underneath the other ice lake. That's called plate tectonics here on Earth. That's about a living planet. Okay. And so this moon has a lot to offer us. Okay. And the really great thing is it's been like this for 4.6 billion years time. It's got okay. And that time is critical. If it had all the right ingredients. To be able to spy on life.
So we got a really good shot at finding life on bodies like this. And some people say, well, that's only going to be microbial. It could be complex life on Europa because of the length of time that that that's occurred there. I would not rule that out. As we move further out, Saturn. You know, we've really looked at Saturn in many ways. And one of the startling things about Saturn is looking at this moon.
This moon is Enceladus. And Enceladus is what really turned our attention to what's going on on these bodies, because it's got geysers. And these geysers are coming from huge cracks in the southern hemisphere. There's four or five of these cracks, actually, we call them tiger stripes. They look like tiger stripes on on the side of a tiger. And they're not just. They're not just little geezers. They are actually walls of water that are pouring out of the body.
Now, this is a small moon, about 300 kilometres in size. And and and it it it it also is suffering tidal forces. We can see the water flowing out of these when the body is close to the planet is much less then when Enceladus is on the furthest away from Saturn. Okay. Where the water pours out.
So we can even see the tidal interactions because of the elliptical orbit demonstratively on, on Enceladus and it's because we've flown through it and we measured the magnetic field and the plasma wave data and, and tasted this water as we went through it, giving us all the data we needed to go back and analyse the Galileo data that allowed us to see that we actually flew through a plume on Europa. We just didn't know it in 1997. Okay.
Now, about 98% of all the water that comes out of the geysers falls back on this little moon. But a few percent of it actually escapes and it forms the E-Ring. Forms the ring around Saturn. So here's the E ring. Okay. And there is indeed. And Solidus. And so we really believe we understand now what's happening because we've also as we've flown through the plume. Measured little bits of rock. Okay. And we've teased apart what the composition is, and we've looked at the composition of the plume.
And we believe that's all very characteristic of hydrothermal vents that is sitting on the bottom of the ocean in the rocky material on in Solidus. So that means the rock is is interfacing with the water, which then is capped with an icy crust. And cracks are allowing this heated water to pour out of the planet, where outside the body is zero pressure and a pressure of the water that's building up inside, under the cross is building up.
And when these cracks open up, it's going to just take off, okay? It's just going to take off. And that's what's happening. In a similar way. On Europa. I know what Europa's surface. At the bottom of that ocean looks like. I know what it looks like. All I have to do is look at IO. Okay. That's got to be what's happening. The bottom of the ocean of Europa hydrothermal vents. Heating the water. It's creating this environment.
And we're finding it on this man to. We also suspect several other moons with water layers. And another spectacular moon of Saturn. Is. Tighten. Now. Titan is unbelievable. It is a huge body. It is bigger than the planet Mercury. Its atmosphere is about twice the atmospheric pressure than we have here. Dominated by nitrogen. Dominated by nitrogen as trace gases of of methane and ethylene. All right. And it has bodies of liquid.
Okay. This is a radar image going through the smog, smoggy environment of the atmosphere, bouncing off the surface, coming back. And the black and blue areas are are. Very. Laminar very still compared to the rough terrain. And we now know what that is. These are liquid methane lakes. Liquid liquid methane lakes. So. Titan has spurred a whole new look at life.
All right. You know, when I talked about life, those three attributes metabolises reproduces, evolves and and for the metabolism we say water. Wonder if you didn't have water. Wonder if it was another liquid. Okay. Wonder if there's life that doesn't need water but still needs the liquid. Okay. And so the bottom line is it could be life, but not as we know it. And if there's any place to go look for. Life. Not like us. It's on Titan. It's on Titan. Okay. What a fabulous world.
So we haven't done all the modelling we needed to in the outer part of the solar system. But if we tease out. What the habitable states are for these bodies. We see that I chose to call too hot. We see Ganymede and in Callisto's too cold. And we now have a series of moons. That is right there in the habitable state. Those are the moons that we're going to emphasise and go after in the future.
So we now have the basis for a number of very important missions coming up that we're that we're thinking about doing, some of which we're building, and we will execute like Mars sample return, like going back to Europa. We have some things that we're studying in terms of getting back to Titan. And jumping around on Titan with a quad helicopter, making all kinds of measurements.
And in surveying these bodies like like we've never done before, now that we have this basis, we then can go and begin to look at exoplanets. And tease out what's happening in in other solar systems. And we are finding absolutely amazing things. So here's Kepler. Kepler works by looking at a large number of stars, by just looking at the intensity of the light. And we just look at the intensity over and over again. Okay.
So when the intensity changes over time and in a periodic way, it tells us there may be a planet there. Okay, so here's an example of a star. For which. When we look at the intensity of the light, as the planet passes, that intensity dips. And a bigger planet. Would obscure more light from the star, giving us a bigger dip. So this is how Kepler works. It takes a look at an area of the sky, large area of the sky where there were 125,000 stars and did nothing but measure their intensity over time.
Okay. And it's from those curves, these very simple light curves. We can tease out their planets. How big they are. And how far away from the star they are. The further away they are from the star, the longer that light curve will be low before it goes back up. Okay. And so at at the end of Kepler, looking at this region of sky, it's now looking at other regions of sky, and it's nearly run out of fuel, unfortunately. It's just been a remarkable mission. We can determine.
What are the most common planets? Now, I don't know about you, but this shocked me. This absolutely shocked me. I thought we were going to see Jupiter's. Okay, I thought Jupiter's. We're going to be all over the place. They're not. They're actually uncommon, okay? They're actually uncommon. And as you can see here. The most common planets are super earths or what we also call sub Neptune size sub Neptune size a super-Earth. We don't have a super-Earth. In our solar system.
This is a rocky body. Okay. That may be up to five, maybe ten times the mass of the earth. Now, that doesn't make it ten times the size of the earth because gravity will crunch it down. It might be twice the size of the earth. Okay. But the gravity can be enormous on these bodies and those are the most common planets. That's a shocker. We also can do follow up observations of these super-Earths. And we can see their size. We know what their size is.
We know what the orbital dynamics are. And and from Doppler shifts and radial velocity measurements, we can actually get the density of the planet in the only way we can get the density to work out is if we add water. And so some of these super-Earths may be water worlds. And I don't mean a little water. I mean a lot of water. Okay. With extensive atmospheres. Things we can get spectra of and really tease out and understand. And these are some of the most common extrasolar planets out there.
Okay. And of course, that water is such a key element. Is such a key element. So most recently a discovery was made and you may have heard about it. It's called Trappist one. Trappist one is a dwarf star. It's not very far away. It's 40 light years away. Okay. It's actually in our neighbourhood, just around the block, 40 light years.
And it had seven planets. And so when the astronomers do the normal calculations of, okay, the heat from that star, you know, with what these kind of planets could have water on them. So it's ice and water, liquid and vapour, you know, where's that habitable zone? Three of the seven planets could be in that habitable zone. Absolutely fantastic. Absolutely fantastic. Okay. So here's the other dimension of that that we now can bring in.
These planets are really close to the star because the star is pretty dim. It's an m-class star and it's really active. It has an enormous solar wind with flares and coronal mass ejections maybe every day. And it's hammering these planets. Okay. This is not a nice benign environment in. Oh, by the way, all these planets are tidally locked. That means they have one surface pointing to the sun all the time. Habitable? Probably not. Probably not.
That's my bet. But here's the important read, the really important element of this discovery. And that is this star, when it was created, had enough planetarium making material to make seven terrestrial planets. And it's right around the block. Okay. And so that tells us we are in an area of the galaxy where we can make terrestrial planets like crazy. All right. And stars in our initial cluster as we were created from a collapsing cloud in the several hundred stars that were created.
Share all that kind of material. And they're probably littered with planets. So we are in a perfect place to really study these objects. Now here's an example of what I'm talking about in terms of the size of this unit relative to our own solar system. And as you can see, because the star is actually fairly dim, all these planets are really close, but it's an incredibly active star. So it's an example of some of the things that we've been we've been doing. Now enters the new mission. TESS Okay.
Tess recently announced that it had gone through. It was launched in April. It's gone through its commissioning phase and it's starting to find exoplanets. First one it found already. Here's the light curve from it. This is a super-Earth. Okay. It's a it's a dwarf yellow star. Similar problems. It's probably going to be tidally locked. But it's the start of looking at these this star you can see with your naked eye. Okay. Tess is looking at all the bright stars.
Bright stars are purposely close to us. And so as it performs its job over the next couple of years, it's going to be finding a list of fabulous planets, I can guarantee you. The estimate is it may find as many as a thousand planets over the next couple of years. Those are going to be candidates for the James Webb Space Telescope to view, tease out what the atmosphere looks like, and looking for signatures in the atmospheres of these planets to determine if they have life.
So in closing, what a beautiful day was here in Oxford. It was clear, it was bright, was beautiful. Reminded me of California right now. So tonight you're actually going to see some stars. So when you go out tonight, you look up and you see those stars. I want you to realise. That there are more planets in our galaxy than there are stars. Okay. And this is a little illustration out of Scientific American a couple of years ago of the known planetary systems in the stars.
And as you can see, planets are everywhere out there. And with the set of missions that we have lined up, we're going to interrogate our local area and we're going to hunt down that planet that's most like Earth. In the in the pursuit of finding life in exoplanets. Thank you very much. So while we're setting up to pass around a mic and I've got all the people with mikes to give you a meatball, which is the Nazi symbol, if you ask a question, you get a meatball.
So that's kind of a neat incentive in that. Okay. And I want to hawk my my my podcast. Okay. So I have a podcast that's called Gravity Assist. And if you're into podcasts, this is a great way to get caught up with what's going on. So it's like sitting down with dinner with Jim Green and a scientist, and we talk about the latest things that are going on right now. We're in the second season. We're talking about some of the spectacular observations all the way from more and more and more movies.
Okay. That's a that's a asteroid that passed through our goal or our solar system that was created in another solar system. First one we ever found, you know, all the way to some of the spectacular things that are that Kepler and some of the other telescopes are finding today. The second the third season that we're going to start here in another month is all on finding life. It's all on finding life.
So if you want to keep up with what we're doing and it builds on the lecture I the talk I gave today, that's the place to go. Okay, great. So we're going to take questions in groups of three. And we've got two people here with roving mikes in the pens. And they'll just repeat your question when you ask it to make sure that the people watching on the live stream can hear you as well. I guess we have a first question up there. All right. Great.
I was just wondering, after Mars returns to the habitable zone, have you model? How long will it take to lose the newly gained atmosphere? We've started a process, so I'll let me repeat the question. It's really all about Mars coming into a habitable state in the future. That's what we predict will happen, has all the resources to do it. We've only started the process of what it would take to keep it there, and there's a whole series of ideas on how to keep it there.
You have to realise for for humans to go to Mars today is really tough. The environment is really tough, it's very cold, it has huge of temperature cycles. The pressure is very low. You've got to wear a spacesuit. But if Mars is, atmosphere can build up to ten times what it is today. So from six millibars to 60 millibars, our atmosphere is 1000 millibars. Okay. So it doesn't have to go huge amount. Then we can we can get to the point where our blood doesn't boil and that.
Okay. No, I'm just telling you what's happening. And that's a game changer that allows us to have all sorts of capability, mobility, you know, less infrastructure, the ability to move around and and do a variety of things on Mars. So there's a lot of talk about how to get it there sooner rather than later. Wait, wait, wait for the sun to do it. But the concepts of modelling right now at Mars are unbelievable.
We have a global circulation of Mars where we can predict the temperature, the the wind pressure, the wind velocity and the pressure anywhere on Mars, and watch it evolve over time. And we've even started to add the dust so we can we actually have got a good representation of of the dust global dust storms to. And we can do that now. We are where Nasser and Noel was in predicting the climate on Earth, the weather on Earth in about the late sixties, early seventies.
We're doing that right now at Mars. And we've made enormous progress in that in that particular. And we need to. So if you saw The Martian, you know why? You're only kidding. The dust storms aren't anywhere near as bad. There's a question. Thank you. Could you summarise the latest thinking on given the right physical conditions, what's the probability that life might evolve? So to really do a good job of that, we need to understand a few more things about these bodies.
We're not quite sure Europa has all the right stuff, all the right organics. We believe it does, but we're not quite sure. And that's kind of a game changer in that in that perspective. But since we don't know what that spark was, we really can't give you a probability. We have to we have to sort of rely on our our best guess. Okay. To me, I think it's so that now this is an opinion.
Okay. Take my now some meatball off and just tell you I think the universe is teeming with life and I think we're going to find it in our solar system first. And we'll have the opportunity to tease it out, see how it's related to us and make enormous progress in those particular areas. And we're hot on the pursuit to do that. So in our lifetime, we'll answer the question Are we alone? Okay. Now I'm going to close the secret files. Close the NSA's secret files.
Thanks for the talk. How good are we at measuring the magnetic fields of these exoplanets? Yeah. How good are we to measure the magnetic fields of the exoplanets? We we haven't really started doing that. Okay. One of the telltale signs of a magnetic field is when that magnetic field interacts with the winds from the stars and produce Aurora. And above the Aurora is a radio wave that's generated we generated at hours.
It's called a whirl killing metric radiation. And the first radio waves that we saw were coming from Jupiter with that same process. And those are called DECA metric emissions. So we need to move into the radio regime to look for these radio emissions around these exoplanets. And so I think as we find them and and as we are able to build bigger and better arrays, we'll be able to will be able to to do that. Now, they're very frequency dependent. Jupiter has an enormous magnetic field.
And that's why that radiation, the DECA metric radiation, can be seen from the surface of the earth because of the huge field generates a high frequency radio wave that's in our radio window. Our Aurora generates a rural killer metric radiation, and that's in the kill metric frequency range, which cannot make it to the surface. It comes down and gets reflected off the top of the ionosphere.
And so there's a you know, we can only do this in radio windows unless we put a radio telescope on the moon. And that's being discussed, too, particularly on the far side of the moon. All right. So there these ideas are coming forth. You know, we're really thinking about how to do the next steps, but teasing out the magnetic fields would be wonderful. I would dearly love that. And I'll tell you why. I'm a magnetospheric physicist.
I never met a magnetic field I didn't like, and I never met a planet that had a magnetic field in the past but didn't have it today that I didn't like either. So that's about it. That's everything. You know, even our sun has a magnetic field, right? Hi. Thank you. Oh, you. I just wanted to ask, what's the state of play or progress of the lunar orbital gateway and to support a human mission to Mars.
And to what degree does the current political situation between the multiple countries involved affect the development of the gateway? So we've announced a a capability, we're going to put it the moon called the Gateway. And this is a human tended system, sort of a many, many, many space station, if you will.
And it will be in a what we call Cislunar orbit that has an opportunity to be behind the moon from our perspective and be able to actually look at the far side of the moon and be available for samples that are found on the back side of the moon that are brought up to the gateway or from astronauts being able to do tele robotics to manage and manipulate rovers and get samples and do things in practice of what we will do at Mars.
Because when we land material on Mars, it needs to be built, needs to be put together. And the first set of things we will probably do will be Tesla robotics. So we'll need to practice that and do that from an orbital vehicle or we'll land on Phobos and do it from Phobos. And I've always said Phobos is the space station of Mars, let's use it. So the gateway is moving along really well.
So what's happened most recently in the last several months are a variety of invitations have gone out to other space agencies to join us. So we'll we'll see more and more international activity on using the gateway. And that's one of the frontier that you need a microphone. So you mentioned the James Webb telescope. That's been delayed several times. What's the latest prognosis on on that being launched? Because it'll be an infrared system mounted to the detections.
I am positive James Webb is going to get launched. Okay. Positive. I'll bet money on it. Okay. That's how certain I am of the fact that it's delayed. That's the current situation. But where we are right now, I'm okay with that. It's got problems. I mean, this is an enormous this is an enormous undertaking. I mean, it's just it's just unbelievable. And and and we've now wrung out the problems. We're in the process of fixing those. You know, Isa's going to launch it with an Ariane five.
We're really excited about that. They're going to participate in the program. While that's happening over the next couple of years, Tess is going to do fantastic things. Tess is going to line up a set of targets for Webb to look at. So in a way, it's going to work out and Scott, I think, work out really well because those are the objects we want Webb to look at. They're close. We'll know a lot about them. And [INAUDIBLE] go right after the atmosphere.
And it's the atmosphere that will tell us whether these bodies are habitable or not. Timing is everything, I guess. Hi. You must get, like, hundreds of proposals for different missions every year. How do you go about selecting which ones to kind of look into and go ahead with and which ones to just put aside? Yeah. So the question is, we get hundreds of proposals in the year. How do we how do we make a decision? And that's really pretty easy because we pick the best ones and we execute them.
So we have created the ability to put out a call for proposals to the community that go after certain objectives. Okay. And for instance, in Planetary, Planetary has a program called Discovery, and that's wide open. You can you can propose for a discovery mission to go to any planet or solar system body except the sun and the earth. And, you know, look at create a telescope to look in astrophysics.
It has to be a solar system mission. And that provides a tremendous amount of flexibility for our community to propose against. And then we have another call that's very targeted. We have you know, we have a set of targets we're going to go to in the targets are going to be, you know, comet surface sample return, Europa, you know, Enceladus, you know, Titan and, you know, just array of things that are that are set. And so we'll get proposals for each of those includes Venus to Venus.
We really would dearly love to have some selectable proposals for Venus, too. So by by binning them out like that and then also creating what we call strategic missions, these are the really big ones like Webb is a strategic mission. We then decide, okay, we're going to we're going to spend, you know, a lot of money. We're going to burn a hole in steel and we're going to do this particular set of science.
And it's going to be expensive when we know that. So we're going to call it a strategic mission. And then we'll we'll ask investigators to propose four instruments. This is what Curiosity did. This is what we did for the Mars 2020 rover. You know, where where we're going to put this rover down on the ground and we need your instruments. Okay. And then and then we assign we assign a centre in NASA's centre to to be able to to to create that infrastructure.
And for curiosity as an example. That was JPL. All right. So JPL went through the 7 minutes of terror, just like I did, and we landed it, and it worked great. And those instruments were from all kinds of places. And they're and we can do international instruments, too. We have a call that goes out where international partners can come in.
Okay. Okay, great. So any time we're going to move out now to the drinks reception, I've been asked to let you know that there are some freebies from NASA out there and also a few leaflets from the Worshipful Company. I'll just hand over to Ian now to close. Not trying to. You want us to look? It didn't quite close as I expected him to do. And a couple of things that were to say, yes, the drinks are outside before we actually go outside.
I want you to join me in thanking the speaker, not just because of the incredible material, but also the inspirational way in which he presented a.