Instrument Scientist extraordinaire Dr Helen Maynard-Casely talks planetary bodies and why she's a scientist!

In this AM Live episode, Dr Helen Maynard-Casely takes us on a journey through the solar system on the eve of the United Nations Day of Women and Girls In Science (11 February 2017).

Jodi Rowley: Welcome everyone. My name is Dr Jodi Rowley. I'm the curator of amphibians and reptiles here at the Australian Museum and at the University of New South Wales. It gives me great pleasure to welcome you to the latest in our series of Night Talks. I'd like to begin by acknowledging the Gadigal people of the Eora nation whose land we are meeting on tonight. I would also like to pay my respect to their Elders both past and present, and extend that respect to all other Aboriginal and non-Aboriginal people here tonight.

Our Night Talks series features incredible minds sharing their ideas, their discoveries and their passions, most Thursday nights this year. So be sure to check up our website and subscribe to our monthly newsletter to find out when they're on.

On 21st March, for example, we'll be hearing about the dangers of spiders both real and imagined. From a clinical psychologist, a toxicologist, and an arachnologist. There's also an arachnophobia treatment workshop with clinical psychologists on Saturday 25th March, so maybe if you're a bit traumatised by the talk… And if spiders are not your thing, we also have a range of events surrounding the Scott Sisters exhibition, and a massive day of rich, diverse and free programming across the whole museum on Seniors Day, which is March 9th.


I'd also like to invite you to try our Culture Up Late events. The museum is open until 9pm every Wednesday this month, with an exciting line-up of demonstrations, workshops and live music. It's a different way to visit the museum, with a glass of wine in hand—although I guess that's quite similar to tonight. But a chance to meet just a few of our scientists and conservationists who work behind the scenes, and there's quite a lot of us.

But tonight's talk is held in celebration of United Nations International Day of Women and Girls in Science. Over the past 15 years the global community has made much progress in inspiring and engaging women and girls in science, and it's something we're really passionate about here at the Australian Museum. In fact, our Executive Director and CEO, Kim McKay, is the first female in this role in our almost 190 years. Our Director of Science and Learning, the fantastic Rebecca Johnson, and I'm the first female non-assistant in the Department of Herpetology. But while we aremaking some fantastic progress, women and girls continue to be excluded from participating fully in science. The probability of female students graduating with a bachelor's degree, master's degree or a PhD in science related fields is still much lower than for males. We don't yet have gender equality in science.

Tonight is a celebration of women in science and we're thrilled to welcome Dr Helen Maynard-Casely, an instrument scientist at the Australian Nuclear Science and Technology Organisation. ANSTO is one of Australia's largest public research institutions, focussing on supporting human health, understanding the environment and supporting innovation for industry.


Helen's expertise lies in the study of small molecules and ices under the conditions found in the outer solar system. Much of her work is motivated by the wish to understand the surface and interiors of planetary bodies.

Helen is also exceptional in her promotion of science to a wide audience, and I'm sure many of us have read her column in The Conversation, 'The Shores of Titan'. Tonight Helen will talk to us about her exciting work exploring the solar system by examining planetary bodies at the molecular level. Please join me in giving her a very warm welcome.

Helen Maynard-Casely: Gosh, thank you very much. And I would like to extend the thanks for all of you being here because I am quite aware I have very stiff competition tonight with David Attenborough speaking just down the road. So I will endeavour to be as entertaining, and I'll endeavour to get my credit towards getting a snail named after me.

Before I start, Matt asked me to talk a little bit about, given that this is a celebration of the first UN Day of Women and Girls in Science, I just wanted to say how important I think the promotion of role models are. I know why I'm a scientist. Aged 8—as you can probably tell, I'm British originally—when I was 8 the very first British person in space was a woman called Helen Sharman. And I wandered up to see my dad after hearing this momentous news and said, 'Dad, I'm going into space, because that's what Helens do.' And I really can't tell you how important that moment was for me, and it drove me to want to be a scientist and to want to explore space.


Now admittedly, and mainly because my sister broke my collar bone when I was 7, I'm probably not going to get into space. However, it doesn't stop me from doing science, which is hopefully exploring a lot more about our solar system. So I certainly think in Australia we have some incredible women, especially—I'm a physicist in the basis of my science—people like Michelle Simmons at UNSW and Tanya Munro. I feel that we should give them all the support and get them out there as role models for girls in the future.

So, with that done, I'll start taking you on a little bit of a journey on the solar system. And hopefully by the end of this you'll see a bit more about the solar system from my eyes. So I'm interested in what is the stuff that makes up the planets. And to do that we need to go all the way back to the sun and we need to have a think of what are the building blocks.

So the building blocks of course are the elements that we have in the solar system. And the solar system's a little skewed in terms of what elements it has. There's a lot less of some and a lot more of others. And that, how it spreads through our solar system, does change the chemistry. For instance, a lot of those middle metals and the silica are sort of trapped in the inner solar system, where at that point when our planets first formed, it was cool enough—or at least warm enough—for these kind of quite rocky and metallic things to condense and start to form the planets that, well, for instance we call home.

But if you get further beyond the solar system, so once you get further out of the solar system, once you get beyond the asteroid belt, there's a big change. And that change happens around five astronomical units. And that's what's known as the ice line in our solar system.


And that's the point, when our solar system was first forming, that water ice condensed straight out of the solar nebula.

And that changed how planets formed quite dramatically, because what would happen is you'd suddenly get lots—there was a lot of hydrogen and oxygen, as you can see, there's a lot there to soak up. And large planetesimals would form, mainly of icy cores, or at least I should say this is the theory. And then essentially they got so big that they could start gravitationally grabbing hydrogen and helium straight out of the solar nebular. And what happened was we got the gas giants literally blowing up like balloons in what is thought a very short time, around 10,000 years.

And so of course there was a lot of small molecules left over from that, and that's what led to the icy moons and the diversity of moons and planetesimals out there. You'll probably also notice that I tend to talk about moons as planets, and hopefully by the end of it you'll see why, because I think especially the icy moons in our solar system are every bit as interesting as the planets.

So I need to talk a bit about how I do my science, and for that I need to talk about a good Australian hero. So here are two gentlemen: William Henry Bragg on this side and William Lawrence Bragg on the other side. So William Lawrence Bragg was actually born in Adelaide, while his father was over being a professor at the University of Adelaide. These gentlemen, along with Max von Laue, pioneered the science of crystallography. And this is the science of how we know the structure of all the materials around us. Anything that's crystalline and indeed now non-crystalline as well is characterised by these techniques.


And the idea is—I could say is relatively simple, but essentially the experimentation that I do is not changed very much from what the Braggs did a century ago, where they took a source of radiation—in their case they were looking at x-rays—they tried to make it into a beam, and then they put a sample, a crystalline sample in the way and got a diffraction pattern. Now from that diffraction pattern they were able to tell exactly where all the atoms in the crystal structure are. Now once you know that you can calculate how strong it is, where it's going to transform—basically you can start pretty much telling anything about the physical properties of materials from that.

And that's essentially what I do today. Now we've moved on a little bit from just x-ray sources. We've now got an amazing source. We can actually do the same physics works with neutrons as well. For us here in Australia our source of neutrons is OPAL, the Open-pool Australian Lightwater reactor (a picture of it is here) and that produces the neutrons which feeds about 13 different instruments, four of which do basically the same thing that the Braggs did for essentially different purposes, one of which I work on and it's called Wombat. You can ask me why later.

We also have an amazing source of super high energy x-rays down in Melbourne. And actually I was there only earlier today, and I used to work there. It's known as the Australian Synchrotron. It's about the size as an Australian Rules football pitch and it is able to generate incredibly bright and very, very precise beams of x-rays to do similar studies.


And essentially it means that we can move on from what the Braggs did 100 years ago and start to look at various stranger samples. We can put samples under extreme conditions, we can start to recreate planetary surfaces. But also we can start to do some really neat physics as well.

So I wanted to take you on a bit of a tour of the solar system and I'm sort of going to ignore all the minerals on Earth, basically. But the first stop is we're actually going to go to Mars, because Mars is the first planet, other than the Earth, to have a diffraction machine on it. Essentially it has a machine that does exactly what Lawrence and Henry Bragg did all those years ago. It's buried inside the Curiosity rover, and this was a really fantastic thing for all of my types of scientists. We all got very excited, because suddenly here was NASA data that we knew loads about.

It's an instrument called CheMin. I'll tell you a little bit about it in a bit. The really nice thing about CheMin is that this thing didn't happen overnight. People haven't wanted to put diffraction machines—essentially diffraction is the best way that you can know the stuff on the surface. You can tell elements from other methodologies, and even spectroscopy. But they're harder to interpret. Diffraction will give you, yes, a very unique fingerprint as to material that are there.

So why didn't we have a diffraction machine out further in the solar system a lot earlier? Well the problem is that that source of x-rays is actually quite power hungry, and in space you don't usually have much power to work with. And so a group of scientists and engineers spent about 20 years miniaturising something that for—in my laboratory, so my normal x-ray diffraction machine is about the size of a washing machine.


They got it down to the size of a suitcase, and in fact here is my colleague Sasha, who has one of these machines. So it was so successful, the miniaturisation of this to get it into space, that they've actually spun it out as a product and now any geologists worth their sodium chloride can actually go off and take one of these into the field.

Now for people like Sasha this is incredibly useful. Sasha's an expert in metastable minerals, and these are minerals that she used to have to go out, dig up, and then run as quickly—or drive as quickly as she could back to her laboratory before they dehydrated, transformed or in some way changed. Now, with Terry, which the diffraction machine's affectionately known as, she can actually study them in the field while she's there. So that's fantastic.

Now the other nice, really cool thing about this diffraction machine—and I should say Curiosityrover doesn't have any PhD students or post-docs to load or prepare the samples for it, so it has to pretty much do it itself. It has that big robotic arm where it drills into the rock a little bit and then it will scoop up some of the drill tailings and then it'll…lean back on itself and tip it into its guts or whatever and swallow this dirt and that will trickle down.

Now usually when we collect data, especially diffraction data, we want to move the sample, and that helps us give a bit of powder averaging in terms of our sample. It gives us better data. Now in space you want to have as small an amount of moving parts as you possibly can, because every moving part is a potential to go quite wrong.

I really like the little innovation that they came up with in order to move their sample around a little bit.


So at for instance the Synchrotron we have a very complicated spinner that is able to both align the samples and then spin them. But it is also quite unreliable, and has a tendency to break quite a lot. So that wouldn't be useful in space.

What the NASA engineers came up with was essentially quite a posh tuning fork, so this device here is essentially a tuning fork and it's got two windows where when that dirt gets swallowed by Curiosityit sort of shakes down into those sample areas and then there's a little bar there that sort of moves and will vibrate the whole sample, and then when that whole thing's vibrating it will actually move the sample around. So it actually gets a bit of a turbulent flow going. And it actually rotates the sample, which I thought was really beautiful. Not only that, I quite like the fact that, like me, Curiosityhums a bit when it collects data. So I think we have that affinity a little bit.

And so next to it is the first diffraction pattern ever collected on another planet. It was collected in 2013, really nicely. It was announced a hundred years and a couple of days after William Lawrence Bragg had first sat down at the Cambridge Philosophical Society and gone, 'Hey, look at my diffraction patterns!' So it took us 100 years to get to Mars. Hopefully it won't take us 100 years to get to another planet.

And actually I'll just tell you a cute little story here. You can see in the middle that the beam stop is looking a bit off-centre, so you can see that sort of red area in the middle, and any diffractionist that would see that would have a small heart attack, because it means that your beam stop, which stops the direct beam from getting to your detector, isn't quite well aligned. And how many of you saw that Seven Minutes of Terror video that NASA put out with Curiositylanding? A few people are nodding.

Curiosity is as big as a car. It's absolutely massive.


And so the way they had to land it on the surface was they had this big, massive parachute and decelerated it with a horrific number of Gs. And then it had a little robot that hovered and then lowered it to the surface. And it was called Seven Minutes of Terror because it was seven minutes that the engineers and scientists would be sat at the Jet Propulsion Laboratory not knowing whether it would have crashed or not.

Now you'd think that that was quite a dramatic thing, and that could have been the point where the beam stop actually came unaligned. No, it wasn't. It was actually they were running tests and it was just about to be launched where they realised that the beam stop wasn't quite in the right position. And I spoke to one of the principal scientists and said, 'Did you try and do anything about this?' And he went, 'Well, we did ask, but given that they'd spent about four months packing it up…' They were a bit like, 'No. We're not going to do anything about it now.'

So unfortunately they just have to live with it, but the other wonderful thing about all of NASA data is they give the scientists who collect it six months and after that it's free game. Anyone can go and grab that data. So I was there waiting for the six months to tick over. And here is one of the diffraction patterns. On the bottom is a diffraction pattern collected by Curiosity rover on Mars. And actually above it is a pattern that I collected at the Australian Synchrotron on Earth. And actually I've zoomed in for a bit of that, so you can see quite how similar they are.

So you guys are probably thinking, wow, how did she make a bit of…did she go to Mars and bring it back? No, unfortunately. The thing we've realised is that essentially as the title says, Mars is a lot like Iceland. All those minerals in there—there's a bit of pyroxene, a bit of feldspar and a little bit of a few other bits and bobs—is essentially the same thing we get in Iceland.


So for instance that sample that I collected there came from here, when I was helping out on a field trip a long time ago.

That's really useful to know because we studied Iceland for about…well, the Vikings studied it for 1,000 years. We know a lot about how the minerals change there, how they get weathered. We can now apply that knowledge to start learning a lot more about the Martian surface. So essentially one of the really key findings that the Curiosityrover has found is just quite how similar Mars is to Earth.

So that's all very well and good, but I think we should go to somewhere where it's not like Earth in any way, shape or form. And I love these guys. These are the icy moons of the solar system. Well they're the ones that we know the most about. I just say that both Uranus and Neptune also have a suite of incredibly interesting icy moons. We've just not got there yet, and we just don't know enough about them.

So Jupiter has the four Galilean moons and Saturn has…well, Titan is really, really big and unfortunately this is not to scale at all, because Enceladus is very weird. We know a lot about Enceladus, it's volcanically active. But one of the really strange things about Enceladus is quite how small it is. It's actually about the size of the UK. It really shocked me when I realised how small it was, the fact that it would probably take about six hours to get a train from one side to another (it would probably be more because there'd be snow in the way). But the real big mystery with Enceladus is how is this body, quite so small, getting so much heat to drive all of those tiger stripes, those geysers that we see?


But I'm going to leave that mystery in your heads, because I'm going to talk a little bit about Europa. And I'm interested in what are the materials on the surface. So how do I—given that I've told you there's no diffraction machine out there—how do we actually learn about the surfaces of these planets? Well there's a few methods, and one of the nice ones that we've got a big dataset for uses near IR spectroscopy. So essentially it looks at the sunlight and it looks at it in a particular energy range. And there was a great instrument called the NIMS instrument that flew on the Galileo spacecraft. This spacecraft which plunged into Jupiter in 2004, is pretty much the reason we know anything about Jupiter and its moons.

I like to use this example because it shows you how powerful this instrument was. So Galileowas on its way to Jupiter and it turned around and Australia happened to be in the way. And it took a big load of its mapping data from 50,000 kilometres. And the thing that I think's really cool—because all that's put in there is the white line, so it can pretty much tell you where the land and all the water is, which is really great. But the really cute thing is, can you see, that you can see the Great Barrier Reef up in the corner there. You can see the calcium carbonate and you even actually see the other reef that I've forgotten the name of over in Western Australia as well. That's amazing, from 50,000 kilometres that this instrument can pick up those chemical differences. But of course those chemical differences tell us a lot about Australia.

If I tell you that that instrument or Galileospacecraft got within 140 kilometres of Europa, then you can get an idea of how much better we know the surface of Europa with this instrument. It's an amazing dataset. Now, the problem, or the interesting thing about near IR data is it's quite broad.


And what happens is they collect this data, for instance all those circles there are data that were collected—they take the whole big map and you can literally pick out particular spectra from every single pixel, and they try and fit them with laboratory data. So they take laboratory data, they try and replicate the conditions, and in this case this black fit is where the material that is basically a mixture of sulphuric acid and water.

Now this is where I come in. I started my post-doc at the Australian Synchrotron in 2011 and expected to be told what to do. I was told, 'No, go away and do what you'd like, but there's not much money.' I went, 'Okay. I'll have a bit of a think.' And when I was reading about this and the sulphuric acid hydrates on Europa, it came very quickly that nobody actually knew what they were. They knew they were sulphuric acid hydrates, but they didn't know their crystal structure, they didn't know basically enough physical properties about those materials.

So I had access to a very powerful diffraction machine at the Synchrotron, so I went to the lab, I grabbed a bottle of sulphuric acid and a bottle of water, I cooled it down to Europa conditions, which on a warm day is around…oh, I'm going to say 120 kelvin, which is minus 150 degrees C. And I got a material that was known in the literature, but can you see those stars there? Those stars are all from a material that no-one had ever characterised before. Now my chemistry friends hate me because they're like, 'How did you just take sulphuric acid and water and get something new? We spend months in the lab and we might not get anything new.' But I think this is my one bit of luck and that's it. It's over now.

So from that data—I actually played around with the compositions to be able to get the signal from that a little bit better. I was able to solve the crystal structure, so essentially I worked backwards with the same maths that William Lawrence Bragg had put down all those years ago, and I could tell you exactly where all the atoms are in that crystal structure.


It's actually called sulphuric acid hexahydrate. It can't be given a mineral name because it's not found on Earth yet. And it's quite interesting, you get these water layers going through and you get these sulphates sitting in the middle.

Now because it's a layered material that actually automatically makes it quite interesting. So layered materials are quite slippy, especially on Earth with all the clays. They're a point of weakness. If you think about water ice at minus 150 degrees C it's really strong. That hydrogen bond really holds it together. So this is the thing that could make the whole of the crust a bit weaker and actually could be the reason that we end up with these beautiful rafts. There is an actual picture of the surface of Europa. So I'm now taking this structure and now I know a bit about its physical properties and applying it to see if we know a bit more about the land forms on Europa.

So Europa's all well and good but for me more and more Titan's becoming a bit of the frontier. Titan is actually quite Earth-like. It's about minus 180 degrees C on the surface, but it has an atmosphere. It has an atmosphere that's mainly nitrogen. And the really interesting thing that we've discovered about Titan is it also has a lot of features that we kind of recognise. It's actually the first body other than the Earth where we can see standing liquid bodies on the surface that are lakes and seas. Now, they're not lakes and seas of water, because it's minus 180 degrees C. They're lakes and seas of methane and ethane. And it actually turns out that we think there's a whole—for want of a better term people call it an alcanological cycle, but it's a hydrological cycle that's not driven by water, it's driven by methane, and actually now we've discovered more about Pluto, it looks like Pluto might have the same thing.


So we've gone from thinking Earth is quite unique—it has, for instance, volcanism, we discovered Io so it's definitely not unique. And then a hydrological cycle we thought was unique. Now we're finding them, for want of a better term, popping up all over the place.

So it's really nice to see these processes becoming a bit more normal. However, we kind of guessed what was in the lakes. There was a bit of a mystery. We not only see filled lakes, we see dried-up lake beds on Titan. And in fact you can even equate these quite nicely to if you ever have the opportunity to fly across to Perth, which I've been lucky to, you take lots of pictures of dried-up lake beds across Australia. Now we know what's in those lakes in Australia because we can go dig it up and they're all salts and hydrates. They're basically evaporites, materials where the water has evaporated and left behind a residue.

But what's an evaporite on Titan? What can evaporate and leave behind a solid residue? We had no idea, because it's not the water that's doing this. And as I said, there's this idea of this hydrological cycle, and essentially these evaporite lakes are a sort of missing link in this cycle.

So we know quite a lot about the surface of Titan now, not just because NASA's Cassiniprobe is there and still going there; its mission will end a little bit dramatically later on this year, so they're actually due to steer it into Saturn, like Galileo was steered into Jupiter. But not only has it mapped pretty much all of the surface of Titan, but also when it first arrived it let go a little probe, the Huygens probe.


I like to use the fact that we've got 100% success rate of landing on Titan as a reason to go back there: it's really easy. And one of the things it noted as it was floating down to the bottom and it got to the bottom, it actually measured the chemistry and it noted there was quite a lot of benzene around.

Now I'm going to get you guys to all think back to high school chemistry and you can remember what the benzene is. It's a ring of carbon, six carbons and six hydrogens sitting off them. So it's a really beautiful molecule with some brilliant crystallographic history to it as well. So we've got ethane in the lakes, methane and ethane, and we've got the potential benzene. There's a few other materials there but that's the thing in mind. And a load of researchers at the Jet Propulsion Laboratory in NASA, so they're the guys who are basically taking the data directly from Cassini—and not only are they taking the data but they're trying to do experiments on Earth to try and work out what's going on. They want to know what these evaporates are, and what they'd noticed was that if you take benzene and you freeze it and you add liquid ethane—so ethane is actually only just liquid at minus 180 degrees C; it actually very nicely could play a similar role to water on Titan—and they saw quite a dramatic change. They could see actually quite nice blocky crystals all of a sudden get eaten up by the ethane. And they were like, 'Oh. That's kind of interesting.' And they had some evidence that there was something new there.

However, NASA doesn't have a synchrotron, which is a bit of a problem for them but great for me, because they were able to come to Australia and we basically recreated this experiment but with diffraction at the Australian Synchrotron. So this picture is essentially the same as those two micrographs. The blue trace is the benzene, all by itself; nice simple structure.


You add the ethane, and then Whoa! Loads of peaks appear, a forest of peaks appear, and that for me is a dream, because that's 'Woohoo, I've got something to go and solve.'

And so from that pattern there I was able to solve the crystal structure, and it's really cute. And so here are the benzene rings, and I've made them kind of big and cuddly. And they form channels in the structure. It's sort of a two-dimensional host-guest structure. It's sponge, basically. The benzene's become the sponge and the ethane sits down the channels in this structure. And so it's a really quite classic evaporite structure, because you can imagine that the ethanes at some point can pop out and potentially pop back in at some point.

That was a really nice result, done right here in Australia. So I've talked about a terrestrial planet and I've talked about icy moons and you're probably all clamouring, 'But there's a big lot of planets you're missing out. And here they are (in my face). I don't tend to talk about Jupiter and Saturn very much, because I like leaving them as a hanging question. We can't yet really recreate the conditions inside Jupiter and Saturn. And even Uranus and Neptune you have to be very specific about the questions you ask, because it's really tough to make those questions. So I always like to say that I'm probably not going to tell you what's inside of Jupiter, but anybody younger in the audience, you're going to be the ones who tell us what's inside Jupiter.

But I always like to talk about Uranus, because I think it gets a rubbish deal just because it's got a stupid name and nobody ever likes talking about it. But it's a really interesting planet. It actually rotates. It has a silly orbit. It's had a good night out and has fallen on its side and orbits a different way. And it means that seasons on Uranus last for 20 years. I think the southern hemisphere has just been through spring and is looking forward to a 20-year winter, just starting. So can you imagine that? And I lived in Scotland…


Not only does it have a weird rotation axis, it has a very strange magnetic field. Again, it looks like it's been out partying because most conventional planets, their magnetic field is generated in the centre, and it's all sort of symmetric around the centre. At least, when we say conventional we mean like Earth. Uranus and Neptune, I should say. It's not in the centre, it's nowhere near the rotation axis. It looks like it's being generated in a very different place. And one of those places—the place probably is. It has this giant icy mantle. So this is what we think is the interior of Uranus. It has an envelope of hydrogen and helium and then not very long after it has a big icy mantle of water, ammonia and methane. And these are those small molecules that I'm really interested in getting amongst and playing around with. And then you can get all the way down to potentially rocks and metals, and some people have even said because there's carbon there with the methane, could even have a diamond core—which I think is a little bit fanciful but it's kind of cool.

But as I said, you have to be very…you can recreate the conditions of Uranus and Neptune but you have to be very strict in what questions you ask. And I was involved in an experiment that asked the question, where has all the xenon gone? So xenon is a noble gas on Earth. There is quite a lot of it in the solar system and there doesn't seem to be enough of it in our atmosphere. We think it's all been gobbled up by the interior, and a colleague of mine was interested if maybe Uranus and Neptune have done the same thing.

And so the way that we recreate these ridiculously pressured and temperatured conditions is…not only are diamonds a girl's best friend, they're also our best friend.


Because diamonds are incredibly strong. They're also clear, so we can see what's happening to the sample, and so we've got these things, they're the workhorse of high pressure research, diamond anvil cells. And essentially this is how you set up the experiment, and you have a piece of metal gasket and you drill a little hole in it and you put your sample in there. So in there, in that sample, the black stuff is to represent some platinum, so I put the platinum in there because there's also water all around and a little bubble of xenon. And the platinum is there because the water and the xenon wouldn't absorb any energy from the high powered laser that I wanted to use to heat up the whole thing. So the platinum's there to absorb all the energy from the laser so we'd be able to get up to 2,000 kelvins, so 2,200 degrees C, but also be able to put up to pressure at the same time.

Now, it's all very well that this is a big diagram, but for scale, the picture over there shows the piece of metal that we put the hole into, and the thing that's next to it is my little finger. So this is something that you don't drink coffee before you try and load it in the mornings.

And what do we find? So what we found was…the first thing we did was we took the sample and we compressed the water and the xenon and we compressed them to 50 gigapascals. So gigapascals is quite a strange unit, but if I tell you that one fully grown African elephant on your average stiletto heel generates one gigapascal of pressure, that tells you, you kind of get some idea of how much 50 gigapascals is. And at 50 gigapascals we're starting to get into that icy mantle of Uranus.

We then turn on the laser and we get that bottom diffraction pattern. And I've labelled what we're seeing. We're seeing solid xenon, still xenon even at that high temperature.


We're seeing the platinum, because we put that in there to absorb the energy. And we're also seeing ice peak. Great! All the samples there, everything's performing as it should. At 1,600 kelvin, bam! Everything changes. New peaks again—new peaks make me very happy. And actually we decided that there's two different new materials in there: one is denoted by black circles and one's denoted by the red stars. And the red star phase we loved really great, because a soon as we turn off the laser the whole sample goes back down to room temperature and, as you can see, it's still hanging on in there, even though it should only exist at high temperature.

And what we found was—again, I'm going to break all the rules of your chemistry textbooks. You were probably told noble gases don't react with anything. But if you give them enough temperature and pressure, they will react. And even I think I heard in the news yesterday there was an announcement that people have seen helium react now at the appropriate temperatures and pressures.

So what we found was a xenon hydrite, or hydrate, and you can see the xenon actually bonding there to the waters. An incredibly crazy material. And I should say that we couldn't actually solve this crystal structure just from that data. It wasn't, compared to the data I got from the benzene–ethane material, we actually had to get some theoreticians involved, which is always good. It's always good to have more people involved.

So that brings me to the end of what I was going to tell you about. The only thing I should say is that I really like planetary science as a field because it's always growing, and we're always finding new exoplanets. There's always new conditions, new materials to find out. And there's always new people to come back to the fold. And Pluto has gone from being a bit cast out of the club to suddenly being the most interesting object that we could possibly see.


And that's thanks to New Horizons. And I'm already there. I'm taking methane and I'm putting it at 44 kelvin and I'm trying to see what's happening. And I think that this is the great thing about the field. It's only growing. There's always more data coming and more conditions to re-create. So with that I will thank and acknowledge all of my colleagues who have helped me with this work, and thank you guys so much for listening.

I know why I’m a scientist. When I was 8, the very first British person in space was a woman called Helen Sharman, and I wandered up to see my dad after hearing this momentous news and said “Dad - I’m going to space because that’s what Helens do.” I really can’t tell you how important that moment was for me - it drove me to be a scientist and to want to explore space. Dr Helen Maynard-Casely.