Planetary Radio: Space Exploration, Astronomy and Science - Mars’ Atmosphere…Lost in Space!

Episode Date: April 5, 2017

Mars was once a warm and wet world. Then its dense, protective atmosphere mostly vanished. Learning why was one of the greatest mysteries in planetary science. The answer has just been delivered by the MAVEN orbiter.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Lost in space. That's the air of Mars, this week on Planetary Radio. Welcome. I'm Matt Kaplan of the Planetary Society, with more of the human adventure across our solar system and beyond. What happened to the red planet? Why did it lose the comforting blanket of air that made it warm and wet? Now we know the answer, and Bruce Joukowsky of the MAVEN mission will share it with us. The night sky above Earth is crowded with planets. We'll let Bruce Betts be our guide, as we also give away just one more rubber asteroid. We learned last week that Planetary Society CEO Bill Nye the Science Guy has taken on a new project. Bill, welcome back.

Some folks might be a bit puzzled by the Planetary Society's involvement with the upcoming March for Science. But I don't find it surprising at all. Well, neither do I, Matt. There, next topic. No, so we are the American Association for the Advancement of Science. Many other the Geophysical Union, many other science scientific organizations are marching because we want to promote the idea that science is good for the economy. Science is good for all of us. Science gives us these remarkable innovations that enable the United States and every country that celebrates science and invests in science to have a higher quality of life for its citizens. So there's been a movement of late to set science aside, to set the process of science that enables us to make discoveries, to create technology that serves so many of us.

discoveries, to create technology that serves so many of us. There's been a movement to set it aside. So we're marching to remind everybody that it's important. This is worth funding. This is worth investing in. This is worth celebrating. And as we like to say, may the facts be with us. Sounds good to me. Speaking of celebrating, how about that SpaceX success? Hey, man, they stuck the landing, as we say in gymnastics. Wow. So the idea, everybody, years ago, our own, the Planetary Society's own Scott Hubbard was very much involved with this, Jim Bell a little bit. Elon Musk, SpaceX. Jeff Bezos from Blue Origin. Virgin Galactic, George Whitesides.

These guys and gals asked, what do we need to do? We want to go to Mars. What do we need to do? And the answer was, roughly from the experts, lower the cost of getting to low Earth orbit. That would free up NASA to map Mars, to do other things without having to spend a lot of the NASA budget on this ferrying service. And it's happening. And so one of the visions at SpaceX was to reuse the first stage of the rocket. Why throw it away?

All these beautiful turbo pumps and plumbing, all this wiring, the giant, expensive, amazing rocket nozzles. Why not reuse that? And so they reused a booster and it worked. And they used a charming turn of phrase, flight proven, flight proven booster. Not used or previously owned. And so, man, more power to them.

That is just cool. And the thing landed right there on the platform just as the plan called for. And so now they say they're going to use at least two of them on the first Falcon Heavy, which is an extraordinary claim. But I got to say, why not? We went to the hangar. We got several of us from the Planetary Society were allowed into the hangar where they have the boosters to be reused while we were there for the launch of OSIRIS-REx, a mission going out to asteroid Bennu, named by the Planetary Society. It's very impressive. I mean, these boosters look like they've been used, but they look great.

The only thing is the nozzles are a little bit sooty, the rocket nozzles, the business end of the rocket. Fly them again, sure. It is a spectacular accomplishment. Our congratulations to them. Bill, I wish I was going to be marching down the street with you or walking down the street in Washington, D.C. on the 22nd. That's a few weeks away, everybody. But if you're a Planetary Society member, check out, am I allowed to say this? Check out the T-shirt, Science is Universal.

And come March, we just want to remind everybody how important science is for the public health and for our economy. That's part of our Omaze account. And you can see Bill modeling that t-shirt. Oh, yes. I look sharp and surprised. You do. You look very surprised. Oh, it's funny. That's the idea. It catches your attention. Hey, Matt, this is cool. We hope to see you in Washington or one of the hundreds, latest count was over 400 sister marches around the world. I'll be marching with you virtually arm in arm, Bill. Thank you very much for all of this.

I'll talk to you again soon. Thank you, Matt. That's Bill Nye. He is the CEO of the Planetary Society and a co-chair of the March for Science on April 22nd. On now to another terrific success, the report just published from the team behind MAVEN that tells us what happened to the air on Mars.

It got blown into space. It's crazy. We first reported on the MAVEN mission a couple of months before its 2013 launch. MAVEN, that's the Mars Atmosphere and Volatile Evolution Mission. The orbiter reached the red planet in September of 2014. Two and a half years later, the team behind it has just announced results that are both sobering and astounding. Astounding in part because MAVEN's instruments have revealed a cataclysm that began more than four billion years ago, and they've done so by studying the upper reaches of the Martian atmosphere. Bruce Joukowsky of the University of Colorado Boulder is the principal

investigator on the mission. He generously agreed to tell us more. Bruce, welcome back to Planetary Radio, and congratulations on this momentous publication, the findings that you have just announced about what happened to the atmosphere of Mars. Thank you, Matt. I really think this is one of the exciting results that will come out of MAVEN. It's one of the things that really tells us qualitatively and quantitatively what happened to the Mars atmosphere. And isn't that what we went there to learn, why you sent this spacecraft? Well, that's what MAVEN is all about. All of the geological evidence, the mineralogical evidence we see on the planet,

based on previous missions, of course, points to there having been liquid water flowing over the surface. To get liquid water, you really need a thicker atmosphere that can trap in the heat. And one of the puzzles for Mars going back some 30 or 40 years has been where did that atmosphere go? Where did the water go? Where did the carbon dioxide go? We don't see any evidence of carbon-bearing minerals in the crust, for example, that would contain enough gas to account for an early thicker atmosphere. So MAVEN was designed to determine, to explore what role loss out of the top of the atmosphere to space played in the history of the atmosphere. So that's really what we're trying to

get at. We're studying the top of the atmosphere and how it interacts with the sun, because that's where the gas is that escapes, and the sun is what drives the loss to space. Would you review for us how one particular gas in what's left of the Martian atmosphere gave you the clues to what happened to all the other gases? We looked at argon as an indicator of what really happens. Argon is an important gas because it doesn't react chemically with anything. So once you put it in the atmosphere, it stays there unless you can physically knock it out of the atmosphere. So this tells us about a process called sputtering, where ions get picked up or energized by the solar wind and can be slammed back into the planet at high velocity and physically knock stuff off. Argon at the top of the atmosphere, even though it

doesn't chemically react, is susceptible to being physically knocked out. I think of it as analogous to a break shot in shooting pool. Yeah. The cue ball in at high velocity and it knocks everything every which way and some of them go to the other end of the table and are lost in the corner pocket. That's what happens with the argon. The other reason that the argon is important is that it has two isotopes. That means that they're both argon gas, but they have different masses. The lighter isotope is preferentially removed by this process, so we can look at the enrichment that causes. As you preferentially remove the lighter isotope, it leaves the heavier one behind, so the remaining gas becomes enriched in the heavier isotope. We can use that enrichment

to tell us what fraction of the argon has been lost to space. So argon is a great indicator of this physical process, and it lets us quantitatively determine how much gas has been lost. Is this process continuing as we speak? It is operating today. We've seen the evidence for it, although it's really hard to measure the stuff that comes out, because the stuff that comes out is neutral, and those are very difficult atoms to observe. But we see it happening. We see the drivers of it today. Now, the loss rate today by sputtering is extremely low. It would take billions of years to remove an amount of CO2 equivalent to what's in the atmosphere today. But early in Mars history, the sun in the ultraviolet was more intense, the solar wind was more intense,

and we think that loss would have been much greater early on. So we're seeing the very tail end of this process today, but we learn how it operates and we can use that to extrapolate back to what was lost earlier. So what we've been doing with the argon is looking at the fraction of gas that escapes, and it provides a clear indication that loss to space has been a major process, if not the major process, in evolution of the atmosphere. But we're also looking at the individual processes that drive escape, and we're learning how they operate today. Once we understand that, we'll be able to extrapolate those back in time and determine exactly how much gas has been lost through time. Has this then also been able to tell us how much of the atmosphere, what fraction of

that ancient atmosphere, is locked away in the soils of Mars. This doesn't tell us that directly, but all the evidence points to the amount of gas still remaining on the planet being a small amount. There's some gas locked up in carbon-bearing minerals, carbonates, or in the polar ice caps, or bound up in the regolith, especially at the high latitudes where it's colder. The best estimates are that this is only the equivalent of maybe 50 or 100 millibars. So not enough to have created that early thick atmosphere, but enough to be of interest. Also not enough to be able to mobilize and put back into the atmosphere to terraform the planet today. Ah, the dreams of some of us

for the distant future of the red planet. So what does this tell us then about the window for life as we know it on that planet billions of years ago? I mean, how long did it have an atmosphere that might have sustained life as we know it? Well, first, let me tell you the specific results coming out of the argon. Quantitatively, it says about two-thirds of the argon that was ever in the atmosphere was removed to space.

That means that the bulk of the atmosphere has been lost to space. We can extrapolate to other gases like CO2. CO2 is important because it's the dominant greenhouse gas we're going to be looking at to have created that early, warm, clement climate. So we think that the bulk of the CO2 has also been lost to space. The loss was driven early on by the sun in the ultraviolet and by the solar wind. We think that the turn on of stripping of the atmosphere was something that accompanied the turn off of a global magnetic field. That is, early on, Mars had a magnetic field. It protected the planet. It caused the solar wind to go around

it. It acted like an umbrella or a shield. So that turning that off about 4.1 billion years ago would have turned on stripping of the atmosphere. More than likely, the action was very quick. The bulk of the atmosphere would have been lost in a few hundred million years at most because this process was pretty effective back then. The action was probably over by 3.7, 3.6 billion years ago. That rapid removal is consistent with what we see in the geology, whereby 3.7, 3.6 billion years ago, the evidence for that early warmer environment was disappearing. So we think that all the action took place in the first few hundred million years after Mars had a clement climate. And we think that all the action took place in the first few hundred million years after Mars had a clement climate. And we think that that's the dominant set of processes that would have turned it from a warm, wet, early environment to the colder, drier planet we see today.

MAVEN Principal Investigator Bruce Joukowsky. When we return, Bruce and I will talk about the possibility of past life on Mars and whether that life could have adapted as the atmosphere disappeared. This is Planetary Radio. Where did we come from? Are we alone in the cosmos? These are the questions at the core of our existence. And the secrets of the universe are out there, waiting to be discovered. But to find them, we have to go into space. We have to explore. This endeavor unites us.

Space exploration truly brings out the best in us, encouraging people from all walks of life to work together to achieve a common goal to know the cosmos and our place within it. This is why the Planetary Society exists. Our mission is to give you the power to advance space science and exploration. With your support we sponsor innovative space technologies, inspire curious minds, and advocate for our future in space. We are the Planetary Society. Join us. Welcome back to Planetary Radio. I'm Matt Kaplan. Well over three years after its launch, MAVEN is in great health.

It continues to examine Mars and sample the planet's air high above the dusty surface. Examine Mars and sample the planet's air high above the dusty surface. Principal Investigator Bruce Joukowsky of the University of Colorado Boulder leads the MAVEN team. That team has just announced its conclusions about the disappearance of the once thick Martian atmosphere. Do we now have a better idea of how long Mars looked much more like our own, you know, warm, wet planet. So Mars had of order three, four, five hundred million years with a climate that could have allowed life to have existed at the surface. Now, since then, there's still the possibility that there could be liquid water beneath the surface. liquid water beneath the surface. So there's still the possibility that life, if it ever originated or ever existed on Mars, could still be there, but below the surface. And it would have had a few hundred million years to adapt to this change, it sounds like. That's right. And life on Earth,

we see, is very adaptable. In a few hundred million years on Earth, we saw life go from the first life to something that was very widespread, very abundant, and occupying very different ecological niches. So it's very plausible that life could have existed on Mars. This doesn't say it did, but it says the environment, based on what we know about life on Earth, the environment was able to support life. That's why I think it's an important scientific question to go find out whether there ever was life on Mars. If we find life, or if we find evidence for ancient life, it tells us that conditions really are suitable for life and that the environment as we understand it to be necessary is all that's necessary. That'll tell us a lot about the possible distribution or the possible abundance of life in the universe. Now, if we go to Mars and we find no evidence for life, it says there's something fundamental about an origin of life or the type of environment necessary to support life that we're missing.

So Mars is really a powerful indicator of how well we understand early life. Either way, if we find this evidence of life that was below the surface, managed to adapt, or if we find no evidence of it, that will be pretty exciting science. That's a great way to put it, Matt. I think this is one of the fundamental questions we're asking, and Mars is a great place to get the next clues as to what's going on. great place to get the next clues as to what's going on. How did Curiosity, the Mars Science Laboratory rover, contribute to this discovery, which has been documented in science just a few days ago? What we're doing is looking at the ratio of argon-38 to argon-36 in the Mars atmosphere. In order to derive the amount of gas that has been lost, we need to know what the initial ratio was, what the current ratio in the bulk of the atmosphere is, and what the structure of the upper atmosphere is. It's the structure of the upper atmosphere

that tells us how the 36 is preferentially removed relative to 38. We know the starting value because almost everything in the solar system has the same initial value, except where it's been modified by things like escape from the Mars atmosphere. Curiosity told us the ratio at the bottom of the atmosphere. So it tells us the bulk atmospheric value, the ratio in almost all the mass left on Mars. And then MAVEN provided the structure of the upper atmosphere that would then tell us how to compute the fraction lost. This would seem to be an excellent demonstration of why it is important to have multiple missions active at the red planet, both above the planet and down on the surface. Absolutely. And I'm going to even go a step

farther. Every time we send a spacecraft to Mars, we're discovering a fundamentally new planet because we're sending something to make measurements we haven't done before. If we want to understand Mars as a planet, we really need to understand all the different components from the deep interior to the bedrock geology, the shallow, uh, surficial geology, the atmosphere, the polar caps, the upper atmosphere, the interactions with the sun. And it's really only through the whole range of spacecraft that we've sent that we can do this. So Mars fills a gap that we've had in our understanding by studying the upper atmosphere, but it really contributes to this broad understanding of the

whole Mars environment. Bruce, is there a lesson in this for all of us on Earth other than don't lose your magnetic field? Even if we lost our magnetic field today, it wouldn't make much difference because the solar ultraviolet and the solar wind have diminished significantly from the early history of the solar system. So in this area, the Earth is not at risk.

The real lessons here are in terms of how we understand how planets work. We're really still exploring our solar system and understanding each of the planets. This is a new aspect of something that controls the habitability of a planet, and it has specific application to Mars. But we can also look at what this tells us about the habitability of planets around other stars. It's another set of processes we need to think about. This is going to sound odd, but by looking at the upper atmosphere of Mars, the thin, extremely tenuous top that most people ignore, we're really learning about the geology of the surface and astrobiology and the potential for life. And we're learning about what controls the habitability of a planet, both in our solar system and elsewhere.

Is MAVEN's work above Mars anywhere near being done? We've just scratched the surface. We have observations now of one Mars year, but no two Mars years are alike. We're into our second year. We want to global dust storm and what it does to the system. And we're also now looking at a different part of the 11 year solar cycle. We're trying to understand the role the sun plays in influencing escape. And we need to look at it both when the sun is strong and when it's weak. We've seen it when it's moderate. We're now coming up on solar minimum. I would love to have observations continue until the next solar maximum early in the 20s

in order to really see what can happen. We're still in the process of trying to define what the range of behaviors is. You've made me think of conversations with Linda Spilker and the Cassini mission, which of course is about to come to an end. But she talks frequently about how incredibly valuable it has been to have that orbiter examining Saturn and its satellites and its rings for such a long time. You just get a lot more great science. Absolutely, and we're looking forward to what comes next. Bruce, thank you so much for, first of all, talking to me on very short notice about this story, which has only just been announced a few days ago.

And congratulations once again to you and the entire MAVEN team on this tremendous accomplishment that has filled in one of the greatest mysteries about Mars. Thank you, Matt. It's a real pleasure to chat with you. Evolution Mission, led by the University of Colorado Boulder, where Bruce is a professor at the Laboratory for Atmospheric and Space Physics, or LASP. We're going to talk to another Bruce, Bruce Betts, for this week's edition of What's Up. That other Bruce, the one that we talk to every week, Bruce Betts, he's the Director of Science and Technology for the Planetary Society. Yeah, he's back on the Skype line right now to share the night sky with us.

And maybe the last rubber asteroid. Boo-hoo. Now I'm just the other Bruce? No, you will always be the Bruce. You know, we did have discussions at some point of having Bruce Murray and Bruce Betts and Bruce Joukowsky and maybe throwing a Bruce Banner at someone else and doing all Bruce paper, but it never came to fruition. Oh, that's too bad. That would have been outstanding. I hesitate to ask what the topic would have been. I think that's why it never went into reality. But Bruce Joukowsky, who you had on, has done a wide variety of planetary

science, so we could have fit something. All right, there's still hope. How about the night sky? The night sky, we've got all five planets that you can see with the unaided eye are visible, but they are spread across the sky and spread across the night. So we've got Mercury low in the west shortly after sunset. And then up above that is Mars looking reddish. And then Jupiter now dominating the evening sky, super bright over in the east and south in the early evening. Saturn coming up in the wee hours of the morning. And then Venus now in the morning, but very low in the east. And you can see super bright Venus in the pre-dawn. And there are also, if you want to get out binoculars, telescopes, cameras, there are a couple comets that are going right now, but they're not unaided eye visible.

But if you have the right devices, you can look things up to see a couple of comets that are about seventh or eighth magnitude right now. All right, we move on to this week in space history. In 1961, Yuri Gagarin became the first human in space. And then 2001, Mars Odyssey launched. And it is 2017, and it is still cranking out data around Mars. And we are coming up on the annual celebration of Yuri's Night, the World Party for Space, which I'm very disappointed I won't be able to go to this week because I'm making a trip to the McDonald Observatory. So maybe we'll observe Yuri's Night there. But, you know, wish everybody a happy Yuri's Night, whoever you talk to.

All right, we move on to random space fact. You sound like you've been around since well before Yuri. Why, yes, I have, Matthew. Pluto's moon, Charon, has dark reddish areas, including the one called Mordor. Oh. They result from stealing bits of Pluto's atmosphere. Some methane that gets stripped from Pluto's atmosphere by the solar wind ends up landing on Charon. It bounces around figuratively until it finds a nice cold spot in the polar regions, hangs out there.

And then as it hangs out there and sublimates and gets redeposited, it gets modified by the sun's ultraviolet light, creating a reddish organic stuff called tholins, the same stuff that makes Pluto reddish. And it's the reason there are those dark reddish, or a dark reddish spot on the part we can see in the New Horizons data. Makes both of them beautiful. One dwarf planet and its companion to rule them all. You know, I've thought of taking the archive of our radio show and trying to throw it into Mount Doom. But now I'm just too enticed by the show.

I have to use it for my own purposes. Don't do that to my precious. All right, we move on to the trivia contest. I ask you, what is the only Apollo command module flown in space to be currently displayed outside the United States? How'd we do, Matt? Wow, big response for this. Easy one to look up, of course. George Wagner was one of the people who did.

George lives in Flanders, New Jersey. He said the Apollo 10 command module Charlie Brown is on the ground floor of London's Science Museum. He's right, isn't he? That is correct. George, congratulations. You have won yourself a Planetary Radio t-shirt, a 200-point itelescope.net astronomy account, and a Planetary Society rubber asteroid. George, again, George.

Again, congratulations. London Museum is also where we've got our engineering model of LightSail hanging out right now on display. Isn't that cool? And it's a great display, too. So go see them both, man, if you're in town. And even if you're not, make a trip to London just to see LightSail and Charlie Brown. We heard from Tom Hannon.

This came by Twitter, by the way. He was replying to my tweet at PlanRad. That's me. He said he listened to the show. As he listened to the show, he was on his way to the Science Museum to do some filming in front of the Apollo 10 command module. Interesting coincidence. At PlanRed, and you are? At Random Space Fact.

And Bruce tweets far, far more than I do. Worth following. Davey Van Ness, in the Netherlands, fun fact, Apollo 10 was the fastest manned or human vehicle in history at 39,897 kilometers per hour, or 24,791 miles per hour for those that only understand freedom units. Is that what they're called now? Apparently, at least in the Netherlands.

Mel Powell, he had this really interesting experience with the incomparable, that's his word, but it's true, Mike Massimino, the great astronaut, about their respective 1960s New York City acquired Snoopy astronaut dolls. Because Snoopy was the lunar module, right? For Apollo 10, yes. module, right? For Apollo 10, yes. Charles Schultz said they could use it as a mascot for some of their Apollo activities, and they called the little caps they wore inside their helmets Snoopy caps, so it was a whole lot of Snoopy fun. And who doesn't love peanuts? Finally, a poem from, yes, the poet laureate, Dave Fairchild. Stafford, Young, and Cernan crewed the flight Apollo 10. They circled around the moon, and then they headed home again. Now England has our Charlie Brown, with seats you'd say is where this crew of astronauts had placed their London derrieres.

Can we say that on the radio? I already did. We're ready for the next one. Who first noted what turned out to be Neptune? So observed it, made note of it in some form, though he is not credited with the discovery because he didn't note its movement and likely thought it to be a star. So who first noted what turned out to be Neptune? Go to planetary.org slash radio contest. Great story in the history of astronomy.

You have until the 12th. That would be Wednesday, April 12th at 8 a.m. Pacific time. To get us this answer, you will win, if you're chosen by random.org and have the right answer, you will win a Planetary Radio t-shirt, a 200-point itelescope.net account. That's that non-profit international global network of telescopes that you can use to observe the universe. And we got to reprieve one last Planetary Society rubber asteroid. And that's it. We're done. All right, everybody, go out there, look up the night sky, and think about whether fresh air is really any fresher.

Thank you. Good night. God, what can I do with that? Ha! Challenged you. Yeah. Unlike Mars, the Earth's atmosphere does not yet have an expiration date. That's Bruce Betts. He's the Director of Science and Technology for the Planetary Society,

and he joins us every week here on What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its deep-breathing members. Daniel Gunn is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan. Clear skies.