Source: NASA / Jet Propulsion Laboratory - Caltech
Published: October 25, 2016

Direct from a Cassini Project Science Group workshop held a mere two weeks before the October CHARM! Hear about what we know about Titan topics that were investigated early in Cassini’s mission. Learn what questions have baffled and perplexed Cassini scientists for a long while (cough cough cryovolcanism cough cough).


Jo Eliza Pitesky: Good morning, everybody, welcome to this quarter’s CHARM Cassini telecon. My name is Jo Pitesky, I’m a member of the Project Flights Team, and today we have a very special presentation. CHARM prides itself on giving access to recent science developed -- and you can’t really get any more recent than something that was just presented to Cassini’s Project Science Group less than a fortnight ago, a two-day workshop that our speaker will be telling you about in highly condensed and highly enjoyable form.

So, I’d like to first introduce our speaker. Before I do that, I’d like to remind people, please do mute your phone because it’s very easy of course to get the distracted by a dog, or something else and we do appreciate the ability to hear our speaker clearly.

Today’s speaker, Dr. Conor Nixon, is a space scientist working in the Planetary Systems Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. He is the Deputy Principal Investigator on Cassini’s composite infrared spectrometer, which we refer to as CIRS, and he first joined the CIRS team actually in graduate school, where he is one of the people who’s really been cradle to grave on this mission. He actually helped to build and test the actual instrument.

Conor studied science in the United Kingdom at Oxford and Cambridge Universities, after growing up and attending school in Belfast, Northern Ireland, as you will hear from his somewhat distinctive accent. His research interests include studying the chemical compositions of the atmospheres of Titan and Jupiter, along with developing future instruments and missions to explore the outer solar system and after hearing this talk, you will no doubt want to follow him on Twitter, indeed, possibility even join Twitter so you can follow him, at Shamrocketeer.

So, Conor, it’s all yours.

Conor Andrew Nixon: Okay, well, thank you, Jo. That’s a great introduction. I’m really excited to be talking today on this CHARM telecon. In fact, as Jo said, I’ve been on the Cassini mission since graduate school and that’s 20 years now, so, it’s been my entire career, but this is actually my first CHARM telecon. So, for that reason, I’m especially excited to (intervene) this one today and thank everyone for calling in.

So, in fact, as Jo said, this talk which I’m giving today on Titan Cold Case Files was very recent science, it was presented just two weeks ago at a workshop of the Cassini Project Science Group, and that’s when we get all the Cassini scientists together on the entire mission from all the different instruments on the spacecraft, and we get together to discuss forthcoming science planning and also to discuss results.

In the last -- in the meeting we had two weeks ago, we decided to go back and examine these cold case files, so these are topics that have been opened up very early in the mission there, and include things or expectations going into the Cassini mission, and things we find very early on that were surprising. Some of these got sold, some of them were not sold, some of them were put on the backburners. We decided to do a round-up of all the things that we were -- that we still had in these cases and see if we could determine if they were still open or closed.

So, this meeting, as I said, was held about two weeks ago and as well as just looking at these science cases, I also want to generate a discussion between the other -- between the various scientists on the team who don’t always get together, and see if by combining different instruments, we can actually get a break in some of these cases.

So, the 12 cases that I’ve selected here are listed here, and my plan is go through these one at a time, give you a very brief couple of minutes' summary as to what is the motivating question here? What is the mystery? What is the evidence, what is the initial evidence that may be caused us to be confused, perplexed, and then what’s the later evidence that came during the mission from Cassini that enabled us to solve it.

Do we think it’s a partially solved case? Or is it really still a complete mystery that’s going to have to wait for another mission to come along and solve with different instruments.

And so, I’m going to go through these cold cases and at the end of that, I’ll take any questions that you have, you can fire away, ask me whatever questions you want, I’ll do my best to answer.

And then if we have time at the end, I want to show you something else which is another project I was working on over the last couple of years with some student interns, and we created a very short, fun, educational video about Titan, which some of you may be able to use in your schools, classrooms, museums or just share to your friends and family. And we’re going to take a look at that at the end and hopefully, there will be a little bit of –a little bit of fun.

So, let’s kick it off with Titan’s Case Number 1, which I’m calling the “Wobbly Spinning Top.” So, Titan, like many of the moons in the solar system, over time, becomes tidally locked to its parent body and, in this case, that’s Saturn.

What that means, is that just as the moon’s Earth keeps its one face towards the Earth at all times, we also expect that Titan I tidally locked to Saturn, so, Titan goes around Saturn in about 16 days and during that time it does one rotation, so it keeps the same face at all times, mostly towards Saturn.

But, we don’t want to just take anyone’s word for it, we want to check these things and Titan, because it has this atmosphere surrounding it, is a little more difficult to check that than it would be if you were looking at one of the other moons, it has on the atmosphere such as Mimas or Enceladus or Tethys or Rhea.

So, we have to be able to see it under the surface and track the surface features and see if the surface features are going around in a 16-day period. Unfortunately, Cassini carries on board very capable radar system and its radar system is able to see right down to the surface.

I’m able to then look at features on the surface and see if they reappear 16 days later in the exact same space or not. And in fact, early on the mission, back in 2008, when we looked at these features, lo and behold, they appeared to be moving. Wow. So, they're not coming back to the same place at the same time. Titan seems to be wobbling, or may be speeding up.

What’s going on here? What could be causing that? Well, part of the -- part of the problem turned out to be a little bit of user error that we had, a glitchy computer program which was not making all the necessary adjustments, so this is actually a great lesson in science that you go back and you check things and recheck things. And after fixing the problem, we determined that the surface features do appear mostly what we expect.

However, once we really get into the details here, we can see that there is some detailed movement of Titan. And you can see these two plots I’ve shown you here. The first plot, this shows the -- what we call the procession of Titan’s spin pole and orbit pole, which are actually wobbling with two different periods, one, a 700-year cycle, caused due to the gravitational pull of Saturn, and also the 29.5-year cycle of Saturn and Titan going around the sun.

And so, what this means is that over very long periods, Titan is wobbling just like you would see a spinning top, perhaps not standing up straight but just wobbling with that axis of rotation processing (lined) in a -- in a circle.

And in fact, these are exactly as we predict them to be, we haven't found anything that’s different than what we predict. So right now, we have the math, we have the tools, and we have explained this case and had all really perfectly matches up with what we expect. So we’re going to call this one, Number 1 is now case closed.

So, we’re going to move on to Case Number 2, “What’s Hiding Inside of Titan?” So, one of the big questions is, what’s Titan made up of? Is Titan a solid body, does it have liquid inside?

How does it compare to the other moons in the solar system? So, from a long time ago, prior to Cassini, even prior to Voyager, we knew what the density of Titan was, we knew roughly how big it was, and we knew roughly how much mass it was and if we work that out, we get a density of about 1.8 grams per cubic centimeter.

And as you may know, water is around 1 -- is exactly 1 gram per cubic centimeter, and a rock is about three times as heavy. So, we’re talking about something that’s right in the middle, around twice as much as water, but less than rock. So, we’re expecting that Titan is going to be roughly 50/50 rock and water ice, because those are the two main things that we can use as our building blocks to build up Titan.

What we don’t know is, how is that material distributed inside? Is Titan still in a frozen state like a (common) snowball where we have ice with pockets of rock dotted throughout it?

Or was it warm enough inside during its process of accretion and formation that it was able to melt all the water and the rock was able to kind of fall downwards through the slush layer, down to the bottom and accumulated at the bottom in the core, and have the ice and water on top. So, in other words, is Titan differentiated or undifferentiated, for the technical terms we use.

And the way we do that is we measure what’s called a “moment of inertia” and really, that’s just the distribution of mass, is the mass concentrated in the center, or is it spread evenly throughout? And we do that by using Cassini’s radio science equipment which tracks Cassini’s location really precisely as Cassini flies by Titan, and any deflection in Cassini’s course due to Titan can be measured really precisely, and that would give us an idea as to where the mass is located, if it’s centrally located or distributed.

So what we find is that Titan’s moment of inertia factor is about 0.34, and that’s just a number and what that means is, that it’s higher than Ganymede which has a really differentiated interior, but it’s lower than Callisto, that we believe, is undifferentiated (coursing) through larger satellites of Jupiter.

So we see that Titan’s something in the middle, and that means Titan is probably partially differentiated, but there are a number of different models that could explain this in different ways, and what we’d clearly be sure of was does that really mean that there’s a liquid layer or no liquid layer? Because there’s a couple of (thermals) within.

But in addition, we can measure something else. And this is the way Titan flexes, which means that it kind of squishes like these balls that you would stretch at your desk if you were having a rough day. And Titan flexes a little bit, and when we measure that flexing, we could look to whether it has zero flexing, like solid ball or if it had a lot of flexing, like a water balloon. That would be the maximum possible case.

And in fact, Titan is in the middle, so it is flexing, and that indicates that Titan is not rigid, it’s not completely rock and absolutely frozen ice, it has to have some liquid layer, it’s going to line the crust to flex back and forth a little bit.

So in this case, we cracked it again, Titan does have a water ocean inside, and that’s really great news because dummies had known Titan is a two-ocean world, it has liquids inside, and as it (would adhere by) -- also liquids on the surface which are different.

So, we’re moving from Titan’s interior a little bit here to the surface and the interaction between the interior and the surface. And so, in this case, we’re wondering, does titan have active tectonics of volcanism? So, the Earth, of course, we know, has its warm inside and the rock -- magma comes up and we have volcanoes. And there’s one other place in the solar system we could be sure about, which is Io, which has rock volcanoes and perhaps a couple of the other moons such as Triton and Pluto.

But Titan we didn’t know about and (particularly) again because we have this atmosphere in the way, it makes it much harder to tell. Why do we think they might actually be active volcanism?

Well, one of the issues is, that Titan’s atmosphere is supported by methane and the methane is being destroyed by sunlight, and if you add up how much methane is in the atmosphere today, and you add up how much sunlight is hitting it and destroying it, we find that there’s only about 1 percent of the methane that it would to last for the age in the solar system. In other words, the current Solar Flux will destroy all of Titan’s methane in about 10 to 20 million years.

So, we think, maybe this methane, they came out of the interior, maybe there’s volcanoes and we have this wonderful early picture from the VIMS team in 2005 on the last year where they saw this bright, icy feature which they called the “Snail,” and then there’s kind of a graphical depiction as to what that might look like.

So, we’re wondering if maybe this has some kind of (flowfront) features that would be like an erupting volcano.

But as time went on, more evidence was accumulated, and the radar team went back and looked at this terrain, in fact, they found nothing strange at all, they couldn't see anything that looked like the VIMS feature. And it just looked like totally flat, undifferentiated terrain and there’s nothing resembling a volcano.

So in this case, we have to send everyone back to the -- back to the computers again. And in the course of the mission, scientists on many of Cassini’s teams have looked really, really hard to see if we could find any other active volcanic features, and at this point, we still can’t be sure.

So, after a couple of examples here, with the one on the left, shows some bright, ice terrain which we call Tui Regio. And this looks icy, so it may be something that’s young, that’s maybe just erupted out of the interior.

And on the right here, we have this really intriguing 3D visualization here of a feature that was mapped by the radar team and it appears to be kind of a mountain peak which you see towards the top of the picture, and then right beside it to the -- to the left, there’s kind of a steep hole. These appear to be about 1-1/2 kilometers in size, both the mountain the hole beside it, which may be some kind of crater.

So, these are really the best candidates that we have right now for volcanism, but unless we see something actually erupting or changing, it’s really hard to be sure if this is really active volcanology or not, or maybe these are just artifacts that are left over from a long time ago.

So in this case, we’re going to call it Case is Open. It’s -- this is actually, perhaps the -- one of the biggest cases that we have on Titan right now. And there’s something that was hypothesized going into the Cassini Mission that we knew we were going to look for this case despite (all the things we have) done. We haven't found anything right now that’s really conclusive. So this is a really -- it is one of the great reasons we have to go back to Titan.

So, Case Number 4, we’re going to look at some of those icy features on the surface in a little more detail. And in this case, we’re going to ask, do we see water ice on Titan’s surface? Right? So, in Case 2, we said that Titan is partially differentiated, which means that the rock is mostly in the center and the water ice is mostly on the surface or the crust. But does that mean we can actually see water ice or not?

So, one of the really interesting facts about Titan is that because it has its atmosphere, because it has its methane, there’s a chemical environment which is going on all the time and as the methane gets destroyed by sunlight, it gets turned into more dense, complicated hydrocarbons which are really like petroleum or other types of organic materials, and we knew that these are going to come down on the surface and (cut) the surface. And these are fully going to obscure whatever ices are there.

So the question comes down to, are there places on the surface where we can see other ice that would be indicative perhaps, of the volcanology, or is everything really just covered up and disguised by the -- with that material. And this map that I fit here, this is again from the VIMS team from early in the mission. And you can see really the diversity of terrain that’s beginning to merge on Titan, we can see some very dark regions, we can see some brighter regions, we think the darker regions are a bit more organic material, and the brighter regions are the icier material.

But, in terms of the detailed composition, we need something else to tell us what the composition is, and that tool is spectroscopy. So again, I’ve indicated a couple of the bright regions here. And when we look at Titan’s spectrum, so, really, what we’re doing here is we’re just looking at the rainbow of different wavelengths of light. So, different colors of heat, as it were. And this shows part of the VIMS spectrum here for different regions on Titan. In particular, the red line here that I’ve shown is really indicative of a typical Titan characteristic.

Now, you can see that there are some bumps showing up here at around 2.8 and 5 microns of wavelength. And in fact, these are places where we knew that water ice is really strongly absorbing. So, if there’s water ice on the surface, these pieces should be dark, and in fact, they reflect this. It does not indicate that there may be an ice there, but it may not be water ice. And it’s been a really difficult task to find and unravel, is there a specific ice that could be causing this? And at this point, we still don’t have all the answers.

But what we do know is, that we haven't found anywhere that we can conclusively say that there is absolutely exposed water ice on the surface. So in this case, the case for the water ice is closed, we do not see water ice on Titan’s surface. But what are the ices is still the open part of the question.

Okay. So, we’re going to move right along to Number 5. And this is one of the most fascinating aspects of Titan. So, more than 30 years ago, when people realized that Titan was producing all these chemicals in the atmosphere that were raining down on the surface, there is an immediate conclusion that there have to be lakes and pools of the more volatile chemicals and in particular, the main material that methane gets turned into is a slightly heavier molecule called ethane and the ethane really, we know, must be filtering down through Titan’s atmosphere and forming the droplets and then raining out on the surface. And the initial expectations were that if this process had really been going on for 4-1/2 billion years, that Titan would be -- hello?

Patricia Bresee: Can you hear me Okay?

Conor Andrew Nixon: Yes.

Patricia Bresee: Conor?

Conor Andrew Nixon: Yes?

Patricia Bresee: I’m sorry. I’m very sorry to interrupt, but I cannot understand you right now. Are you walking away from your microphone, maybe, or ...

Conor Andrew Nixon: No, I’m outside the phone. I’ll just try -- just try and speak up a bit.

Patricia Bresee: You’re all underwater here. Okay. Is this a good time to ask a question?

Conor Andrew Nixon: Sure. Go ahead.

Patricia Bresee: All right. I’m sorry to interrupt. The obvious thing for me is the timeline for Cassini. If you have already given it to us, I’m sorry, I missed it. But I’m up here in New York State. We want to know what the timeline is for Cassini. We want to know what it’s doing for the next few months and how long it’s going to be there.

Jo Eliza Pitesky: I think that’s a question we’ll be able to address offline, because that’s something that is -- this particular CHARM is going to be focused on Titan results. And I’m sorry, I didn’t catch your name?

Patricia Bresee: Okay. I can barely understand you, but you said you can’t give it to us right now?

Jo Eliza Pitesky: The focus of the particular telecon for today is just about Titan, as opposed to being an overview about the entire timeline of the mission. But if ...

Patricia Bresee: Okay.

Jo Eliza Pitesky: ... you can give me your name, I can contact you afterwards and we can hook you up with people who can give you those resources as well.

Patricia Bresee: Okay. I’m sorry. My name is Tish Bresee.

Jo Eliza Pitesky: Okay.

Patricia Bresee: And I’m a system ambassador up here in Vestal, New York. And ...

Jo Eliza Pitesky: Okay.


Patricia Bresee: ... observatory. And yet…


Patricia Bresee: …right to me.

Jo Eliza Pitesky: Sure.

Conor Andrew Nixon: Okay, and Tish, I would also suggest that if you look at the Cassini website, there’s a lot of information online about the Cassini mission. It’s a really great resource. But I’m sure if you can’t find the information on there, somebody from the project, Jo or somebody else would be really happy to help you find the information you’re looking for.

Patricia Bresee: All right.

Conor Andrew Nixon: Well, I hope everybody else can hear me. That maybe that’s just a problem with the local line up there. So I’m going to keep going. Yes, please interrupt me if there’s any other problems.

But for now, I wanted -- I want to keep (somebody’s) latencies on Titan, because the expectation right after the Voyager mission, which was really the first close-up visit of the Titan back in 1980, was that Titan should be covered in really deep oceans of ethane. So, this is one of the main reasons that Titan -- that Cassini carried a radar instrument, was to be able to look at the surface and see what’s going on there.

So, it took us a while, actually, to find any liquids on the surface at all and this was really, really surprising result. So, you have to remember, we thought the Titan would be absolutely hundreds of meters deep in a global ocean of ethane has been produced over the age of the solar system. And in fact, what we find was some really big lakes on Titan’s north pole, which you see on the left here. Very, very little in the site, just one lake which looks a little bit different in site, you can see there in the bottom of the southern hemisphere (plot). But we didn’t see these global oceans, and that was -- that was a real surprise.

And we’re going to come back to that in a layer -- in a layered case book. For now, the case that I want -- the thing I want to examine here is why these lakes in the north are not on the site? Because if you think about the Earth, it’s not like we just see lakes in the northern hemisphere and not in the southern hemisphere. So, we need something to explain this.

And in fact, it turns out again, this is due to the orbit that Titan has going around Saturn and the orbit that Saturn has going along the sun. So, Saturn has an eccentric orbit, that means it’s an oval orbit, it’s not a circle. That means at certain points, it’s further from the sun and a lot of ties it’s closer to the sun. When it’s further from the sun, it’s moving slower, going to Kepler’s (loss), and when it’s closer to the sun, it’s moving faster.

And what it seems is that at the present time, when Titan is closer to the sun, that happens to be when it’s southern summer, when the southern hemisphere is tipped towards the sun. And that means that the southern summers are both shorter, but also more intense than the northern summers, and you can see that on the top number, A, that I’ve put there which shows this brighter, kind of white region around 270 on the X-axis, which is in the sides, and you can see that the corresponding time period in the north, around 45 LS in the north, is not reflecting that.

So, I hope you can see that those two (counter) brightnesses are not symmetric, so the southern summer, when it comes around the southern summer at 270, it’s a lot brighter and hotter than it is in the north around 45. But there were times it reverses and there’s about a 31,000-year cycle to that, and that means that if you go to the middle (plot), you can see that these two brightnesses have now reversed.

And now it’s the north, when it comes be summer, it’s hotter and the southern summer is less hot. And what that means is at the present day, the liquids are really just going to evaporate more rapidly in the south, and they're all going to rain out in the north, but then when the northern summer comes along, it’s not going to be as hot and it’s not going to evaporate or lose liquids back to the south again.

So it’s going to be an asymmetry to the pattern of evaporation there. And on the extreme right-hand part there, actually the north pole and south pole, kind of the way the peak heating is from 100,000 years ago through the present day and you can see that they’ve traded places a little bit. And that right now, the south is that red line and south is in the ascendancy, so the southern peak insulation is hotter.

And a little wrinkle to this is that methane and ethane, which are two things that can both compose the lakes, the methane is about 10,000 time more easy to evaporate than the -- than the ethane, so the methane is really going to move around while the ethane is going to stay still. Okay, so in this one, we have -- we have cracked their case, yay. Case cracked.

And we’re going to look in a little bit more detail about this ethane questions on Case 6. So, we’ve kind of got this map of the lakes, we have more lakes in the north, you have less lakes in the south. But we’re still seeing vastly, vastly, vastly less lakes, less organic material on the surface than we would expect if Titan’s had this active full chemistry, it’s almost like a giant chemical factory that’s spewing out chemicals over 4-1/2 million years and there’s just not nearly enough organic material on the surface to account for that.

So in this kind of like, bookkeeping game of accounting, someone is fiddling the books. There’s 99 percent of our -- of our carbon is missing. So, I’ve put here, Titan is producing about 15 million kilograms of ethane per day, if you add that up, we should be hundreds of meters deep in ethane, but we don’t see that. A lot of the other organic materials on the surface we see as well as these lakes and seas, are that we see these dune fields, and I hope you can see in this figure that I’ve put here these linear features going from the bottom left to the top right and if they encounter these icy kind of hammocks, they appear to either be blown and divert around the hammocks.

Or, in some cases, they just kind of come to a stop. And this surface that we’re seeing, kind of longitudinal dunes here, which are very similar to the sand dunes you see on the Earth, particularly Namibia, has been held as an Earth comparison example. But in this case, we’re seeing organic material, dry, flaky organic material. And it’s wafting around on Titan’s surface winds. But even if we had to (pull) this organic material, which is not even liquid, we still don’t have enough organic materials. So, Titan’s ethane must be going somewhere. Or is it?

So, one of the clues we have is when we looked at Titan’s poles, we find that Titan’s poles are shrunken, so Titan is a little bit squished compared to the poles or squished compared to equator by about 300 meters. And one hypothesis which is a really intriguing hypothesis is that the ethane can be leeching into this water ice crust. And inside this crust, there are little cages. These little cages, you could see in the lower right-hand side of this figure here, we have these little red circles, and they're in these little cages of water ice.

This is methane and what happens is, when the ethane, which is the two black circles, the molecule that has two black circles, comes down and percolates inside these cages. We call these “clathrate cages.” And it pushes out the methane and displaces it and puts itself in there and that allows the methane to move to come back in the atmosphere, and it also gives these (slidey) holes where the ethane can hide out in the crust.

And this also means that the crust now becomes denser, because it’s a heavier molecule, than it did before, the crust is going to get denser, it’s going to sink and subside a little bit under its own pressure, and that means that could explain the fact that the poles are now squishing down because they're getting heavier compared to the equator and in fact, we know that the rain is occurring at the poles so that’s a really great story if it works.

Now, if we look at the squishing of the poles, we can account for perhaps about 300 million years up to 1,200 million years of ethane production, and that’s about a quarter of the age of the solar system. So that gives us a pretty good hypothesis that if ethane is only being produced for about a quarter of the age of the solar system, we may be able to explain it.

But at this case, we really don’t know how long a time this had an atmosphere, so we don’t know if that is going to be enough to explain this accounting irregularity. So while we have a very good break in this case, we cannot, at this time, say, “Case is over and closed.” So, case open for Number 6.

So, moving on along to Number 7, we’re still on these liquids here, and in this case, we have something really remarkable, which we’re going to call “The Magic Island.” And very dramatic, you can see here in these figures, which I have put on the slide, that we have a feature which seems to not exist and then it exists, it appears, and then it may be -- it’s even going bigger.

Is this what was going on here? Is this some kind of a peninsula which is a merging from Titan’s Ligeia Mare, which is one of the large polar seas? Or is this something else? Is this -- what could it be? Could it be something in a circle? Could it be -- could it be waves? Could it be bubbles? Could it be a frothy, frothy organic bubble material? I mean, it looks like the rest of the bright material which we think is the dryer land, the icy land. But there’s something that’s coming and going here while the rest of the surface is not doing this disappearing act.

So what’s going on here? So in fact, this was a project which became a project for our graduate student, Jason Hofgartner up at Cornell University working with researchers up there on the radar team. And they were able to study to detail on the -- in their paper at seven possible hypotheses, which I’m not going to go into in all the possible details. These included things like the lake surface actually rising and falling, or maybe even the lands could be rising and falling. I mean, we left no stone unturned in this case.

And Hofgartner would (inaudible) in real detail, and he concludes that the most likely thing is that the lake -- the lake bubble is not rising or falling, and neither is the land, but it has to be something this occurring in the liquids, and this could either be a floating or suspended solids, or could be some kind of bubbles, or it could be waves, which is the most likely explanations.

And based on what we see on Earth, looking down on Earth with radar, radar tends to see rougher material. So when we get a reflection like that, it’s because the surface is rough, it’s reflecting the radar back towards us. When the surface is smooth it appears dark because the radar is not reflected back towards us. That appears radar, so if we were looking in a mirror, we would something that’s radar-dark. If we were looking at a very flat, unperturbed surface of the lake, we would see something that was radar-dark.

When we see something that’s radar-bright, that means we’re either seeing a rough surface, or we could be seeing rough whites on a liquid. So, the most likely explanation here is something that is able to appear like that, seems to be that we’re seeing some waves develop, and this could be where sea is shallower or it’s passing over something subsurface and this is causing waves to break.

So this is -- I’ve put in this picture here of the proposed mission, this was a few years ago, and this mission was called “TiME,” the Titan Mare explorer. This was a probe that’s going to float like a boat, and it was going to land on one of Titan’s seas and further on for several months and tell us a lot about what was going on in the surface, take picture, measure tides, measure waves if the probe is bobbing up and down, like atmospheric measurements, and even suck in some of the lake material and do a chemical analysis.

And really, we were -- (tons) that NASA didn’t pick this mission, picked a different mission instead for this opportunity, but maybe this mission will come around again and be proposed at a future date. So we know that this magic island inclusion is not exactly Las Vegas magic, but we really don’t know for definite what it is yet. Our best hypothesis at this point is that it’s raised.

Okay, I don’t know where you’re living in the U.S., maybe you’re living somewhere that’s very sunny all the time, and maybe it’s -- maybe you’re living in Seattle, but on Titan, we have this problem of too many sunny days. So, Titan, as we’ve said, is shrouded in haze, but right down at the bottom of the atmosphere, there’s something else, and these are clouds, and these are the clouds of the methane and ethane that form the rainfall.

And in this plot here, this color-coded counter plot, this shows, over time, where we expect the latitudes on the (center) for the rainfall to be -- so you could see back in January 2004, down in the lower left-hand corner there, we expect a lot of precipitation in Titan’s south, and as we go through years, as Titan undergoes this 29-1/2-year cycle, going around the sun with Saturn, that the precipitations will move into the central latitudes near the equator and then finally move into the north.

But what we see, is in fact, the -- so that’s what the model says we should see, but what we see is in fact, these black circles, these black dots, and these are indicated where we’ve seen clouds on Titan, and you can see that there’s a humongous outburst right around January 2010, but the rest of the clouds have been really, really patchy and hard to see. Part of this we know as an observing effect, because (we are) not observing Titan all the time, so we only get a chance, maybe every 30 days or so, to fly by Titan and actually look for clouds.

But even so, we’re not seeing nearly as many of these clouds as we expect and in particular, in the later stage of the mission, if you look towards the upper right here, where the orange and yellow contours are, we’re seeing hardly any clouds forming on top of this.

So we expect that right now, Titan should be going really (clean) having a lot of rainfall begin to happen in the north and this is due to the insolation and the south -- the south is going into summer, it’s being driving off any liquids in the south. And that these would be carried to the north, and then rain and condense out on the surface, and we’re just not seeing that.

What is going on? Why is Titan so sunny? Why don’t we have enough clouds? So, even as we’ve begun to think about this problem, we saw something else strange. And this is very recent, this is from Juno this year, 2016, and on the left here you can see a photograph taken by the Cassini VIMS team, the infrared camera which principally (looks) 1 to 5 microns.

So that’s the infrared. And on the right here, you can see a shorter wavelength image from the Cassini imaging camera team. And what we see is we see these really bright spots appearing on the VIMS image and we don’t see anything in the image in there that are visible. So, what’s going on here? How can we be seeing a cloud, a lot of clouds in the north, and yet we’re not seeing them with another instrument at almost exactly the same time? And this is a really big mystery. I mean, this really has us stumped right now because, in fact, this is about the opposite of what we expect.

We would expect that it might be possible to see clouds appear with the imaging cameras, but they could be invisible through the longer wavelengths because the particle -- if the particles are small enough, they might be transparent at the longer wavelengths, but in fact, we see something that is only seen at the longer wavelengths and not at the shorter wavelengths. And this is just truly perplexing to us.

So, in this case, we might have taken what was already a mystery of not enough clouds, and now we’re seeing clouds and at the same time, we are not seeing clouds, so there’s really going to be some explanation. Required here. And this one is definitely a case open. And of course, we’ll be looking very intensively for clouds during the remaining one year of the Cassini mission.

Okay, so we’re on to Case Number 9, the “Tilted Pole” of Titan. So, this is something, again, really remarkable. Now, in this case, we’re talking about Titan’s rotation, but we’re not talking about the rotation of the solar body which is what we talked about all the way back in Case Number 1 with the Wobbling Pole. In this case, we’re talking about the atmosphere.

So, on this slide here, what I’m showing you is contours of temperature. So we’re looking on the north pole on the left, and we’re looking on the south pole on the right.

You can see here is that the south is warmer at this time, the north is colder, this was from early in the mission when the north was still at the end of its wintertime, and the south was in its fall, before it went into -- before it went into winter. The north was just coming out of its spring, so the north is still cold and the south was -- had not yet cooled down.

What we’d expect is that the atmosphere should be going around Titan in a symmetric way, so as we go further in latitude, it should get colder, but in fact, these -- what we call contours, or these circles or ovals of temperature, are not lined up.

So, the -- where the atmospheric pole effectively is not on top of where these solid body pole of Titan is, so in fact, at about -- instead of a 90 degrees north, it’s at around 86-1/2 degrees north, is where the atmosphere is -- the point where the atmosphere is rotating around. And that’s really strange. Why would that be happening? Titan is a slowly rotating world and there’s no reason why the atmosphere should be tipped over compared to the surface.

So one theory was is that this could be due to the sun where the sun is forcing the atmospheric pull a little bit away from the solid body pole, from the direction of the (instance) of sunlight. And ...


Conor Andrew Nixon: Yes, go ahead.

Male: The numbers on the bottom, are those degrees -- are those kelvin?

Conor Andrew Nixon: Yes. Absolutely, yes. It was a kelvin, yes. Okay. So, what we find is, as we go along in the mission, we would expect that this pole which is tipped away from the sun, as we begin to go around the sun, it would remain in an inclination which is tipped away from the sun, and in fact, guess what, it doesn’t do that at all, Titan has just fooled us yet again.

Titan’s polar tilt of the atmosphere is staying exactly where it is, so as Titan goes around the sun, and it’s not responding to the sun at all in any way, so it looks like the atmosphere is staring at the stars while the surface is doing its own thing.

So, in this case, we’re -- we -- I was on a team, we put out a theory for this, and it turns out our theory is not working, so it’s back to the drawing board, and case open on the tilted atmospheric pole.

Okay. So, moving right along here, Case Number 10. “The Fugitive, Methane.” So, this case, what we find is that the top of Titan’s atmosphere, and in fact, it’s one of the most (solitary) atmospheres, there’s a -- there’s a point where the atmosphere transitions to space, and we call this the “Exobase.” So, anything that’s above that is the exosphere, exo meaning, “outside.” So, it’s outside of the gravitational pull of the body and loose molecules can escape into space.

And over time, the atmospheres do get eroded from the top of the atmosphere from the exobase and these can be from different processes. And on Titan, we can see that there’s methane and hydrogen that’s escaping, but the curious thing about the methane is that the methane is really escaping, and the methane is escaping much, much faster than it should be escaping.

The escape of methane should be pretty slow at the present day, because Titan has presumably been around for a long time, and the very fast escape process which would have occurred in the early solar system, has not come down. And in fact, what we’d expect is that a process called “Jeans Escape,” nothing to do with your blue denim pants, but names after an astronomer, Sir James Jeans, proposed that molecules which are a little bit faster than other molecules is the fastest of the fast, so the ones that are going to escape, most of the molecules are going to stay put.

And this is what we call “Jeans Escape,” a very, very energetic molecule is able to have enough velocity due to its temperature and is able to reach the escape velocity and then just cross over that exobase into space and drift away. But the amount of methane escaping is really much, much more than that.

So, the two plots that I’ve put here really just show different models compared to observations of argon, for the argon on the left and methane on the right. And this is a little of a complicated story, but the bottom line is, that if we can do something which works for argon, it doesn’t work for methane. And if we do something that works for methane, it doesn’t work for argon, so, the two things should be pretty well-mixed. And it’s just not like that, so what’s happening is that the methane is somehow speeding up and escaping.

So, we have several possible explanations here. We have the methane is escaping from the atmosphere at this really truly incredible rate of 2 times 10 to the 27 molecules per second. And if we look at the normal escape velocity method of letting molecules escape, that run explains 1 times 10 to the power of 19, subsequently, eight orders of magnitude too little to explain how much methane is escaping. And even if we include what’s called “sputtering” and that means, sputtering is really the solar wind coming in. The solar wind is these fast, energetic particles of protons and they're bumping into molecules and they can just bump from so that they get bumped off Titan. The sputtering process can get you up another five orders of magnitude, but it’s still 1,000 times too weak to explain the amount of methane that’s escaping.

And the only possible way we can explain this is by invoking something called, “Hydrodynamic Escape.” Not literally means that the atmosphere is being heated up so much, but the entire atmosphere is swelling up just like a -- I don’t know, like a balloon being pumped up and the atmosphere is actually actively being pumped up and the molecules are being -- are being forced, the entire atmosphere is being forced through this gravitational boundary of the exobase and being forced into space.

I mean, this is something that we know happens to be at the early period of transformation, but we just don’t expect that that’ll be happening today. And if this is occurring, then Titan’s methane could be a -- tend to be disappearing really rapidly. So this is a really perplexing mystery. And this case, we really don’t know where -- one of the things we’re looking at is our observations of the argon and methane that we really understand those and if so, we still have a mystery in our hands.

Male: Question.

Conor Andrew Nixon: Go ahead.

Male: Would this imply that the top of Titan’s atmosphere would be warmer than expected?

Conor Andrew Nixon: Yes, I mean, (inaudible) that there’s heating going on that’s driving the expansions again. So, that’s the model that we have to put in place to explain this (game).

So, we have a mystery with methane, but we also have a mystery with hydrogen. Of course, hydrogen is a very small light molecule. We know that hydrogen is escaping from total times atmosphere, in fact, that we’ll make an account for, but hydrogen is doing something else really bizarre. And (what timing) is that hydrogen has a percentage of about 0.4 percent on top of the atmosphere, but only by 0.1 percent at the bottom of the atmosphere.

And that implies that something is subtracting hydrogen from the bottom of the atmosphere, and when this was modeled, it appeared that the only way to explain this was that the hydrogen just seems to be just disappearing into Titan’s surface, like it’s just being sucked in. And that’s really surprising. There was a hypothesis, actually, that tentatively suggests that if you have certain life forms, they could take hydrogen on the (settling) and turn it back into methane. But, when you add up the numbers, this really doesn’t seem to be a good explanation.

So -- and even more strange, is that the hydrogen is varying in latitude, so the figure that I’m showing you here, just shows the variation of hydrogen with latitude. You can see that it’s peaking up to higher values over the north pole and that it’s lower on the equator and the south. And so, there’s something -- not only is it low, right at the surface, but it’s not the same all over Titan’s surface.

So, one possible theory that could explain this high value in the north could be again due to Titan’s circulation. So, on here you see Titan compared to the Earth. Because the Earth is a faster, rotating world, we don’t tend to see just a single atmospheric circulation cell where the air rises in the southern hemisphere and sinks in the northern atmosphere. It tends to get broken up into different zones we have, an equatorial zone and then we get to the mid-latitudes and then we get up to the polar cells.

But on Titan, because it’s a slowly rotating body, that means that the evaporation that occurs in the south, that enriched air flows around to the north and then sinks in the north. And that’s during the southern summer and northern winter, and then that would reverse.

And during the period where these two things are transitioning, you have the case -- you can see it in the lower left, that’s where we have the sunlight on the equator, where the air is rising in the equator, it’s (causing pause) in the equator -- and then it’s flowing to both poles. So, in general, the air is going to be rising on one hemisphere and sinking in the other hemisphere.

Well, that could be a potential explanation for this hydrogen case. So, if we go back to our previous slide here, again, you can see the hydrogen is higher in the north hemisphere which is on the left-hand side here. And that could be because of the circulation which is rally pulling down air from the higher parts of the atmosphere, and is pulling down the air, this air which is enriched in hydrogen is being pulled on into the lower parts of the atmosphere. And that’s enriching the lower parts of the atmosphere due to the circulation.

So, in this case, we may have an explanation as to why there’s a little bit more hydrogen in the north than in the south, but we don’t know why it’s so low overall in the lower part of the atmosphere. And this is a really major mystery and this page, it’s still an unsolved Titan Cold Case.

Okay. We’re coming onto the last case here, I know that we’re going pretty quickly, there’s a lot to take in. I hope you’re able to get an overview here. If you move along to the last page, we’re going to look at the floating and sinking haze of Titan. So there’s some really beautiful pictures here.

In fact, the picture on the left -- this is from right back in 1980. And one of the things you can see here is that Titan is orange, so you’ve just got a little bit of the edge of Titan here on the right-hand side of that left picture. And above the main part of the atmosphere, you can see that there’s this blue haze, and this is something similar to what you would see on the Earth on a -- on a hazy day, but then right above that, there’s a gap and then there’s another haze and then there’s floating haze there. This is floating above the main part of the atmosphere.

This is really strange. How can you help something that is separated like this? Because if you -- even if you have some air that was blowing upwards, why would it not form a continuous profile? Why would it form this distinct layer?

So when Cassini came along, one of the things we wanted to find out was, is this layer still there? And you can see a beautiful image here from Cassini back in 2005, which shows that beautiful detached haze there extending from the north really a substantial way around the disc of Titan. So you can see the main orange haze there and then fading, and then this beautiful detached haze there at about 500 kilometers above the surface.

But why? Do we -- do we have an explanation why?

Well, the two main theories for this could be that it’s produced by either, number one, a particular chemistry, which occurs 500 kilometers in altitude or, B, it could be due to a dynamical explanation. When I say dynamics, I mean, winds, I mean, air blowing materials. It could be that there’s some kind of circulation, which is drawing this material along the edge of Titan at around 500 kilometers altitude or it could be a mixture of both. It could be that this chemistry on dynamic is occurring.

But then something strange (sort of) happened. So, in fact, the haze began to -- the detached haze began to sink. And I’m not going to wish you had -- I drawn some lines on this figure, but if you look here on the left-hand side, 2006, you can see that there’s some red at the bottom and then it goes blue, and there’s a gap, and then you see some more kind of lighter blue and white. And that lighter blue and white towards the upper left-hand corner is the detached haze there.

And as we move through the seasons going from left to right across that image, you can see that this detached haze around 2009, 2010 begins to bend downwards and it eventually just blends into the main haze, so by 2012, 2013, we no longer have that gap region above the main atmosphere with the detached haze floating on cloud.

And right now if we were to take this right out to the present day, we would see that something is happening. It appears that the detached haze is actually reappearing again, so there’s definitely something seasonal going on here on Titan with this detached haze, which is causing it. But as to how much is due to the chemistry and how much is due to dynamics, we still need to work out these details.

Okay. So this one is still a case open. So, what I’ve put on my last slide here for the main presentation is -- oops, I hope it’s going to not freeze up on me.

Okay, good.

So I’ve taken the 12 cases, which I’ve put forth here. And we’re going to see which ones are close and which ones are open, and right now we have four of our cold cases -- case closed. We’re very happy.

And in the other case -- the case is still open -- this gives us a score on here of Titan (eight signs) is four. Titan is still winning at the end Cassini, but, you know, the great thing is that even those cases that we call “case closed,” that doesn’t mean that there’s not further study to be -- to be done, for example, with the surface ices. You know, we know that there’s no water ice exposed to the surface, but we don’t know what the ices are, you know, with the -- with the magic island. We think we’ve got an explanation, but we’re not completely sure.

With the lakes and seas, we got a really great explanation as to why we’re seeing more lakes in the north up the present time and not on the site. That’s a really good case, but we don’t know why there’s not more liquids on the surface of Titan overall. So we’re saying the sun is not quitting.

We have another year left of Cassini. We have been now in orbit around Saturn for 12 years and we’ve got another year before we go into our final dramatic plunge in the Saturn’s atmosphere. And during this time, we have a couple of more flybys of Titan close up and then we have a lot more flybys of Titan at further distances, so we still have a lot of Titan science to do.

One of the key things that we’re doing in this last year of the mission is really look for those clouds -- those missing clouds and see if we can -- see if we can figure out are there more clouds appearing, will they finally line up with our models or is this mystery going to continue?

So, what I’m going to do is I’m going to stop here. I want to, first of all, acknowledge the other science on the team here who are really responsible for the science in each of these individual cases, which are presented today. And I want to take any questions you have. And then I would like to, right at the end, go on and show you this short video we have to present today.

So thanks for your attention so far. I hope you find this interesting and intriguing, and I hope if you -- there’s still plenty of mystery there. So I’ll go ahead and take questions.

Male: Okay, yes. You mentioned that the wobble of Titan now -- as you know, the Earth itself wobble on its pole. Are the two mechanisms related?

Conor Andrew Nixon: That’s a really great question. As far as the Earth goes -- not being an earth scientist, I’m not completely sure what the mechanisms are for that. I know that that would be the gravitational interaction between the Earth, the Sun and the Moon.

And, you know, on Titan, it’s due to the -- to the parent body, which is due to Saturn’s equatorial bulge pulling on Titan, and I’ll switch you to the sun. So I think, in general, it is the same mechanisms.

The -- on the -- on the earth, we have these long period cycles that are known as (Chrome) Milankovitch cycles. And, in fact, that was what inspired scientist Odette Insin to try and come up with an explanation for the -- you know, for the -- for the Titan polar wander, so it was by looking at the Earth that we’re able to see if the same mechanisms are at work on Titan.

Male: Great. Another question, now you’ve concluded that Titan does have a water ocean at Yay. Would this be similar to the ocean, we think, is under Europa or on Enceladus?

Conor Andrew Nixon: Okay, that’s a really good question. So the ocean’s on these worlds may be similar, but not identical. So one of the real questions is that when you have an ocean, which is frozen by water on top, what is on the bottom of that ocean? And is it going to be ice on both sides so you just have a layer where it’s warm enough and at the right pressure to have water with bond to the above and below by water ice or is bonded just by water ice on top but bonded by something like rock on the bottom? And that would lead to differences in the chemistry of those oceans.

So, on Europa and Enceladus, the hypothesis that they are bonded on the bottom by rock, and on Titan, we believe, that it’d be bonded on the bottom by water ice, so that would mean there may be less of the mineralogy, but we could get from the rocks going into Titan’s water ocean, so there may be some differences.

Enceladus, of course, we know is active enough that it has these jets out of these geysers on the side pool. Europa, we think, we’re seeing some geysers, but we’re not sure. Titan, there’s definitely no evidence of that. So I would say that there’s a similarity and a difference in what the chemical makeup of that ocean is.

Male: Thank you very much. One more question. So with regards to the missing hydrogen, and I presume you’re talking about molecular hydrogen, H2. As, you know, on Earth, there is a sink for carbon, so a lot of carbon on the Earth is physically locked into these sink areas. Would a similar mechanism be fair for the hydrogen on Titan that it’s to say could there be a large hydrogen sink where, on Earth, there’s a large carbon sink?

Conor Andrew Nixon: Well, it’s a good question. So the carbon sink on the Earth is that formation of carbon at rocks, and that forms a very volatile substance in which you can trap your carbon. So on Titan, we have to have a chemical process. We are taking the hydrogen on binding it up into something that was heavy enough to not be volatile. So, in principle, you could react the hydrogen maybe with an unsaturated hydrocarbon, so a hydrocarbon that doesn’t have all of the possible bonding positions use that. That could be something like a polyacetylene. And, you know, that -- you know, to me, that could be a possible explanation.

I don’t know how much that we looked on detail. I mean, in general, hydrogen gas, of course, is very volatile, so unless you’re able to bind it up into, you know, heavy material, it’s going to -- it’s going to just mix back into the atmosphere again.

So, you know, I agree with you, there could be an analogy there. It’s a great question.

Male: I seem to be asking a lot of good questions here.

Conor Andrew Nixon: Very approving questions. Thank you, yes.

Jo Eliza Pitesky: Conor, it’s Jo, and I have a more meta question. And I -- since Cassini’s flybys, as we know, are coming to an end, what do you see, if any, of the role, if any, of ground-based facilities of James Webb coming online, hopefully, and other space-based observatories in possibly closing off some of these mysteries.

Conor Andrew Nixon: Well, that’s a good question, Jo. So, you know, maybe we can do something with clouds.

I’m currently involved in observation (tonic), the James Webb Space Telescope for Titan, in particular, and looking at Titan. But, of course, for James Webb Telescope, despite being such a large, great facility is, you know, a heck of a lot further away than Cassini is on Titan. That means we don’t have the ability to see small clouds coming and going. If there were some kind of really big cloud outburst, we could definitely see it.

And, you know, in general, in the infrared, the overall reflectance of Titan changes by a few percent whenever there’s a cloud outburst so we don’t even have to be able to resolve Titan from (adopt) to be able to know that there’s clouds there.

So, as far as other observatories, I also work with the ALMA Telescope, which is in Chile to be able to look at molecules in Titan’s atmosphere. So one of the things we’ll be able to do is that even after Cassini has left, we’ll be able to monitor the seasons coming and going on Titan.

However, some of these things, you know, are really going to acquire different sort of missions. We’re getting down to the surface, being able to tell what the surface composition, what’s the lake composition, you know, what are the winds doing in their little atmosphere, what’s happening with hydrogen on the surface. And, you know, what’s in the crust? Is there -- is the crust really (curl up) like a sponge with ethane. (You know how) many different sorts of missions to go there and do that.

So, you know, at this time, we’ll be able to do a lot from the ground in terms of monitoring the seasonal change of Titan’s atmosphere, in particular, but I don’t think we’re going to learn too much about what’s really going on down at the surface. So, hopefully, NASA will put together a mission for that.

Jo Eliza Pitesky: We had a question online asking if you expect more mysteries to arise towards the end of the mission.

Conor Andrew Nixon: Okay. Well, I should (tell upfront) that because I picked these 12 mysteries, this is not the complete list. So, we’re actually going to put together a complete list and write an article about this and we’re up to around 16 or 17, and this is just the ones that we’ve picked out to be the most important one. So there’s a lot of open questions.

We have another question that’s a big question right now, but why Titan isn’t trailing around a trail of nitrogen atoms behind it as it goes around Saturn? And that’s something that’s been looked for and hasn’t really been understood either because Titan’s atmosphere, despite having a lot of methane, a couple of percent, it’s mostly 98 percent nitrogen, which is fairly inert. But even so the nitrogen can be lost from top of the atmosphere and should be trailing around Titan.

So there are other questions there. You could talk about questions about Titan’s potential for astrobiology for life. Is there anything that could be habitable or inhabiting the latencies or in the interior?

There’s really the questions about how old really is Titan. We’ve talked a lot about Titan being 4.5 billion years old, but is it really that old, did it form more recently.

The Saturn system, in some ways, is very strange. Saturn has these big bright icy rings. The other planets that have ring systems such as Jupiter and Uranus and Neptune don’t have these big bright icy rings. They tend to have very faint, dusty rings, which are not at all the same. And, in fact, the expectation is the icy rings probably don’t last that long, maybe only 100 million years or so.

There seems to be some kind of transient event on the Saturn system that may have created the rings. It may have even, for all we know created Titan from other moons that get banged up and join together.

So there’s really big open questions at this time as to, you know, was there some catastrophe in the Saturn system or maybe it was the fact that Titan was there for a long time, but for most of its period -- for most of its history, it didn’t have an atmosphere, and the atmosphere is a more recent occurrence, which happened -- maybe something happened in the interior. It came to a certain point where there was a new state of matter formed and this caused some kind of overturning, which led to an outburst of atmospheric gases and that therefore the atmosphere is very recent. So I mean, there’s really big open questions right now. And, you know, it’s going to take all of our -- all of our wits and all of our ingenuity to really try and crack these.

Male: Again I’d say if Titan formed out of other moons, is that -- you’re talking about a lot of other moons.

Conor Andrew Nixon: Yes. So it’s interesting theory, which is that if you look at the Jupiter system, you see that Jupiter has four moons that are about the same size. They are all pretty big. And then if -- well, let’s say they’re medium-sized moons, then if you look at the Uranus system, you’ll also see that Uranus has about four kind of medium-sized moons. They’re not as big as the Galilean moons, but if you reshow the moons Uranus to the size of Uranus, you get about the same proportion as you get taking those four big moons of Jupiter to the size of Jupiter.

Then you come to Saturn, and what you expect is that where Titan is there should be four medium-sized moons, and instead you see one really big Moon. So, you know, those are kind of like there’s some questions there.


Male: I have a question about Slide 40, the one where you scored it. Titan (inaudible) score.

Conor Andrew Nixon: Oh, yes.

Male: If you’re looking at that slide, I’ve been trying to -- so this is my personality to get a one for one relationship between these 12 and the titles that you gave in the slides. And I think I messed them up. I think Case 2, which says, “What’s hiding inside is actually (inaudible).”

Conor Andrew Nixon: Absolutely, yes.

Male: And that’s -- you show it here as Oakland, but in the slides you showed it as closed whereas the magic island underneath that you show is open in the previous slide, and here you show it as closed. So I think the labels were reversed almost to open and close.

Conor Andrew Nixon: You know, you may be right about that, yes. Yes, I think you’re right.

Male: I just want to make sure I was matching the right words with the -- as you used different words of the titles but…

Conor Andrew Nixon: I’m very glad you’re checking up on me.

Male: Okay.

Conor Andrew Nixon: Yes. If you -- if you spot anything like that, please let me know. Yes, I’ll make sure those are changed online for the final version.

Male: Right.

Jo Eliza Pitesky: Any other questions for our speaker?

Male: Regarding the fugitive methane, this made me wonder how well-quantified is the association of methane high in Titan’s atmosphere.

Conor Andrew Nixon: So that’s pretty well-understood. So we know the solar flux, so we know how much ultraviolet light is coming from the sun. And that causes a -- it’s basically give or take the solar cycle, but over a very long periods or millions of years, the sun has a -- you know, a fairly steady average life.

And that means that the amount of methane that’s being depleted is at a certain rate, and we can literally just take any U.V. photon, which is shorter than the wave length or, in other words, have enough energy to break apart methane just to add up all those photons. So, in particular, it’s the lime (and alpha) flux of the sun and cause the hydrogen in the sun, which produces -- I think it’s around 121 nanometers light, and that’s just the principle dominant flux, which is -- which is coming along and initially breaking up the methane.

Then something else happens. Once you break up methane you create this radical C2H, which is a little bit like acetylene, but it’s a -- it’s acetylene with the hydrogen removed. And this is called the ethynyl radical, and then this becomes like this predatory molecule that can just go and destroy methane just kind of like a rampaging, you know, bull in a -- in a China shop. And this causes much faster depletion of methane.

But we also under pretty well, we believe about that reaction rate. So, we believe that we’ve got a fairly good handle on how fast the methane is being -- is being destroyed. And we know how much methane is there, so if we take these two things together, we believe that the methane is only going to last anywhere from 10 to 30 million years. It can maybe stretch it to 100 million years, but, you know, it’s not going to go beyond that unless you’re generating it from the inside.

Male: Okay. Hi, I’ve got one more question. You’re talking about the various types of mass loss that Titan may be undergoing. Running the time machine backwards, how much bigger was it when it finally condensed around Saturn? How much more massive was those compared to today?

Conor Andrew Nixon: Let me see if I understand your question. So you’re saying if we run this backwards the methane is being depleted…

Male: Right.

Conor Andrew Nixon: …how much more…

Male: Methane whatever -- right, how much bigger was it way back when?

Conor Andrew Nixon: You’re talking about the atmosphere of Titan being big enough?

Male: If there -- or even the massive -- the moon itself since that seems to be a large part of its -- what makes it up, you know, how much heavier was it?

Conor Andrew Nixon: Well, the atmosphere would be a very, very small fraction of the overall mass of the -- of the Moon itself. So I don’t think the actual mass of Titan would change very much, but the size of the atmosphere, you know, which is really much less. It could have substantially change.

So there’s a couple of clues about that, so one is the fact that this methane being depleted, and we could run this backwards and say, Okay, there had been, you know, 100 times more methane in the past.

There’s also an interesting clue with nitrogen, which is that nitrogen comes in two main isotopes? There is 14 nitrogen and 15 nitrogen. And the amount of 15 nitrogen that we have on Titan appears to be higher than we would expect at the time of formation.

What this may mean is that during the early times of science history, some of the lighter isotope, the 14 nitrogen, was preferentially escaped from Titan. It may be that by modeling that detail, there’s been attempts to do this. We could actually backtrack and say how long in the past would have been that the 14 to 15 nitrogen was exactly the way we would -- we would expect it, so something like the -- you know, the giant planets. But right now, it’s enriched, which is what we see on cases like on Mars where we know for a fact that there’s been a lot of atmospheric mass loss. So yes, we believe that Titan’s atmosphere was more massive in the past.

Just setting my memory here, I think those suggestions that may be two to 10 times more massive, the atmosphere in the past.

Male: Okay, thank you.

Conor Andrew Nixon: There’s not an action, yes.

Jo Eliza Pitesky: Any other questions for our speaker?

So now we have a bonus extra from Conor, which he will describe.

Conor Andrew Nixon: Okay. So something a little bit different here, but still on the general theme with Titan. I hope you’ll find this somewhat entertaining.

So, over the -- couple of years ago where I worked in NASA Goddard, we have a big intake of some of our interns. A couple of hundreds interns come here in the summer. A project that I dreamed up to keep them occupied as well as actually doing the science, which they’re must be doing was to do a fun project, a (nickel movie) by the time.

So the inspiration from this came from just like a travel commercial for Titan. I could take a vacation to Titan, what would it be like to actually go there. And we call this Titan Tours.

And in addition to making this movie, we didn’t just make it in a regular 2D format, we actually made in a kind of a pseudo 3D format, so we made this for Science on a Sphere, and I don’t know if any of you may have come across this or not. You can perhaps shout out if you have. But it’s a -- it’s a spherical movie projection.

And you can see here, this is -- this is like a six-foot globe, which generally hangs from the ceiling in an auditorium. It can be in a museum. It can be in a school. It can be in somewhere else. We can project images. It was originally devised by NOAA, National Oceanic and Atmospheric Administration, to show whether on the Earth -- whether on the Earth’s globe, ocean currents and things like that, and there are some really incredible movies if you ever get to see those in one of your local science centers.

But there’s been a move recently to do some planetary science versions of this as well, and this has been the medium we decided to use just to see what would it be like to put Titan on a sphere and to make our movie in this format. So, you can see here we have a combination of projections of Titan onto the surface. And then on top of that, we were able to put some kind of letterbox-style pictures, which would show people talking about Titan.

Here’s the ship’s conference showing the arrival of Titan.

And so the overall goal here was to make something that could be used for outreach purposes to give maybe a bit of visibility to Cassini but also to the science that’s coming out for Titan in general and to make sure that some of the science didn’t just get lost in scientific journals, but was able to reach out to the -- you know, to the public or K-12 or other people that might be interested to see this in a science museum, and to do it in a -- in a fun way, that might create some memorable learning moments.

So here I have pictures of some of the interns involved in the project. These are all, you know, really great young adults who, in NASA, they really got into this. They helped devise these shirts, the logo we had. And we had five student actors who, you know, acted out different scenes on the surface.

On the -- on the left here, we have beside a crater. In the center, we have on the sand dunes. And on the right-hand side, we have the dry sea beds, which are under the equator, which, in fact, is where Cassini landed a small probe called Huygens on the surface that we envisage that maybe one day there would be a museum here that you can visit.

We have to tickle (with the) artistic license here. We did away with the space suits and helmets for some practical reasons. So you have to imagine that our actors are safe inside a -- safe inside a bubble here, but they’re almost spot reporters telling what it would be like.

Each of these rotations we just need to describe very briefly what you’re seeing and then there’s kind of a fun activity. You know, you could go take a blue flight over a crater or you could go ride a dune buggy over the dunes.

An idea here is to convey the science so that people will remember, oh, my goodness, we could ride a dune buggy, and then they’re going to remember dune fields or -- in another example, here we have a nice volcano, “Hey, we can do skiing that we’re going to try to find the visual aspects of that, just the learning aspects so the people remember these key different terrains or different topographies on Titan.

Okay. So, let’s see. So we did our initial filming in summer of 2014, and then we had a bit of a hiatus while we waited to get the rest of the production done.

You can see myself here in the right-hand figure with the skis, a couple of the actors, and they’re surrounding the lady in the pink shirt who’s our acting coach. She is not in the movie, but she was one of our administrative assistants who does (inaudible) theater, and she is really great. She helped us out with the acting coach and to the other actors here. And then on the left-hand side, we have our ship’s captain who’s a real-life ex-astronaut. He’s one of our high-profile science astronauts here at NASA Goddard. His name is Piers Sellers, and he’s very active in promoting Earth global warming signs.

So we finally, in summer 2016, we were able to get another student intern this time not as an actor, but actually as a production assistant and is production assistant out of the sound effects, put everything together out of the musical score, which is rather amusing out of the credits, and did do a lot -- finished up the animation work and got it ready for the overall release.

And the 3D version -- calling to the 3D version, it’s really -- it’s really a 2D sphere version. It came out on the International Observed the Moon Night, which was a couple of weeks ago in early October. And we had a big crowd here at NASA Goddard, but, I think it was around 300 or 400 people.

Even though it was a rainy cloudy night, and we weren’t going to get to see the Moon, people came out anyway and we had a lot of activities. And that’s one of the activities not just the Earth’s Moon, we featured other moons in the solar system. And in our spherical -- sphere auditorium, we showed this movie and did a nice premiere, and we have one or two of the actors able to come back for that.

But because we realized that were weren’t going to get the widest possible audience, just having this particular medium, we also wanted to go back to the 2D version, which I mean a rectangular version, so this movie was then re-cut and was put onto YouTube. So we’re able to go on and hopefully clicked on that link.

If the link doesn’t work, I think you would be able to just go and do a search on YouTube for Titan Tours GSFC, or Goddard Space Flight Center, and that link should come right up as one of the top hits.

And since it was put online a little over a week ago, I think we’re over 6,000 views, so it was really -- was like doing any advertising at all. I mean, today is really the first time we’re actually talking about this YouTube version in public to you guys so you’re the -- you’re the official release audience for this. But we had it up in clandestine for -- by the week or so, and we’ve got some views already.

So I think given the time that we have here, we’re almost out of time. We may not have time to have you guys click on the YouTube link and then come back and ask me questions because we’re really close to the end of time.

So at this point, maybe I should just ask if you have any questions about this and just hope and encourage that all of you will go and have a look. And if you find it a good product, maybe you’ll show it to some of your classrooms or your friends and family or just be amused yourself.

And I should also add there is a link to this slide on the -- on the CHARM web page, and thanks to Jo and (Enrico) for pulling that up.

Jo Eliza Pitesky: Any questions?

I’d like to thank our speaker again. Conor, that was a really marvelous summing up. And for those of us who are in the room here at JPL who saw the workshop at the PSG, this really is a great representation of the entire thing in only under an hour and a half.

Conor Andrew Nixon: Okay. It’s gone pretty fast, but I think it’s a lot of it there, yes.

Jo Eliza Pitesky: For those who are still online, our next term telecon will be on Tuesday, January 24th. And right now, it looks like it’s going to be something extraordinarily interesting about Enceladus.

I’d like to thank everybody for joining us, and we will have eventually a recording and a transcript of the entire presentation up online if you would like to share this with other people who might have missed the presentation live. Thanks all again.

Conor Andrew Nixon: Yes, thanks again for me. Thanks everyone for dialing in.

Male: Thanks. Great presentation.



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