Planetary Radio: Space Exploration, Astronomy and Science - Flowing Water on Mars? Not So Much

Episode Date: December 27, 2017

Mars scientists dubbed them recurring slope lineae or RSLs. They sure looked like evidence of liquid water flowing down hillsides and ridges on the Red Planet. New research led by USGS Planetary Geologist Colin Dundas says otherwise.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Flowing water on Mars? Maybe not. 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. Recurring Slope Lineae, RSLs. They gave us hope that at least a little liquid water still makes it to the surface of the red planet. A new paper says, think again. We'll talk with lead author Colin Dundas of the U.S. Geological Survey. There's a mythic edition of What's Up Ahead when we'll once again mix it up with Bruce Betts. Senior editor Emily Lakdawale is here for the start of our journey

that takes us to a comet and to Saturn's moon Titan. You may have heard us talk about NASA's three classes of missions. The most ambitious and expensive are the flagships. The least expensive and supposedly most frequent are discovery missions. In the middle are the New Frontiers efforts, like the New Horizons mission to Pluto and beyond. middle are the New Frontiers efforts, like the New Horizons mission to Pluto and beyond. The space agency has just picked two finalists for the next New Frontiers spacecraft. Emily,

before you tell us about which of these two exciting missions may actually be headed out across the solar system, I just got to say, I'm selfish. I wanted to see not just both of these, but all the other missions that were up in this New Frontiers program. Oh, don't we all, Matt? And I particularly have to shout out to my poor, forsaken planet Venus that got shafted again in this choice. No Venus mission selected, none in the last discovery round. It's a planet we really need to understand. We need to understand why it's so different from Earth, even though it's made of the same stuff. You know, we're discovering all these exoplanets that could be Venus-like or could be Earth-like.

And if we don't know what makes our two Earth-sized planets different, then how are we ever going to understand exoplanets? All right. Rant over. Our colleague, Jason Davis, who wrote about this new Frontiers Down Select in a December 20th blog entry at planetary.org. He actually includes some great tweet posts on this exact topic of Venus getting short shrift once again. But listen, for now, tell us about the two that are still in the competition. The two that got through the Down Select are both proposing to go back to places that we have visited and even landed on before, but that's where any similarity ends. One of them is called Caesar.

It's a comet sample return mission, and it proposes to go to the comet that Rosetta visited, 67P or Churyumov-Gerasimenko, and land on it and bring samples back. Comet surface sample return is one of the priorities in the decadal survey. The Dragonfly mission, by contrast, seeks to land on Titan and deploy a quadcopter to go explore through Titan's atmosphere, visit several little spots, touch down in different spots on Titan, and carry out an entirely different kind of mission that has never been attempted before on anybody, much less an outer solar system planet. It's really very audacious. Sending a drone to Titan to check out that little world? I mean, both of these missions are exciting, but I want to volunteer to be on the surface of Titan with that drone remote control.

Yeah, I think everybody is really thrilled about the prospect of a quadcopter on Titan. But the fact that it's so crazy sounding may not bode well for its future in selection. By contrast, Caesar is a very high heritage mission. You're talking about a spacecraft that looks a lot like the OSIRIS-REx mission that's already on its way to an asteroid. You have a very seasoned principal investigator in Steve Squires, who's the principal investigator for the Mars Exploration Rover missions. You have a comet that's been studied very up close before, whereas the landing on Titan, while impressive, was only in one little spot by one relatively incapable lander. Also on Dragonfly, we have a younger principal investigator. Her name's Elizabeth Turtle. She would only be, I believe, the second female principal investigator ever in NASA mission history.

And the team of people that she assembled also has a lot of women scientists on it, which is really rare. And these are all, like, I know them all. They're incredible scientists, and they really deserve a chance. It's a contrast between a seasoned design and an audacious new plan. Most of the people that I talked to seem to think that Dragonfly is really going to have to prove an awful lot to make it to the selection. But I know these people, they're going to really try to make it to the finish line. I have invitations out and congratulations to both Steve Squires and Elizabeth Turtle. I hope that we will be talking to them on Planetary Radio in the coming weeks and months.

Emily, we'll watch to see what happens. Have you seen when this decision might be made by NASA? I actually don't know. Well, I'll be waiting and seeing. It'll be sometime in 2019, though. Thank you so much, Emily. It's great to talk to you on this last program of 2017. And I look forward to having you join us again for an

extended conversation with our colleagues, Jason Davis and Casey Dreyer for the first show of 2018 next week, when we will look back at 2017 and look forward at the coming year. Can't wait. That's Emily Lakdawalla, Senior Editor for the Planetary Society, going on now to talk about news about a feature on Mars that, well, may not be as wet as a lot of us were hoping. There is an enormous amount of water on Mars. We've seen it just centimeters below the surface, and we've detected massive amounts much deeper in the soil of the red planet. Essentially, all of it appears to be ice.

And yet, a few years ago, scientists working with the amazing HiRISE camera aboard the Mars Reconnaissance Orbiter showed us tantalizing images of a progressive change in the shape and color of certain Martian hillsides and ridges. You can actually see in a series of photos what looks for all the world like a flow running downward. These flows are observed on portions of the red planet enjoying their warm season. Later, they return to their original shading as if they had dried out. It didn't take a great leap of faith to believe we were looking at liquid water running downhill. Now a new paper has cast doubt on that conclusion. Research geologist Colin Dundas of the United States Geological Survey is its lead author. Colin, welcome to Planetary Radio. It's a pleasure to have you on the show.

Thanks for having me, Matt. Let me start with a feeling that I'm going to guess is shared not only by me, but by a lot of our audience. You had to go and be spoil sports, huh? Well, I mean, RSL have been a problem for quite a while. They've been a puzzle. And it's always been clear that Mars is a challenging place for liquid water and our results fit in with those challenges. I note that at the end of your paper, at the conclusion of the paper, when you present this data, you basically share the thoughts of one of the Planetary Society's founders, Carl Sagan. Extraordinary claims require extraordinary proof. Yeah, I think that that's a true statement. As I said, RSL have always been a real challenge for us to understand. And I think that the evidence we found is pointing us in some useful directions. Give us the background here. I think probably almost everyone listening to this show

is somewhat familiar with these so-called RSLs. But tell us what it is that was found on the surface of Mars. I think originally by the Mars Reconnaissance Orbiter, that amazing high-rise camera, right, that you're part of the science team for. Yeah, that's right. RSL were first reported in 2011, and they're flows that occur on warm slopes. 2011. And they're flows that occur on warm slopes. They're darker than the surroundings, and they creep slowly down the slope over the course of usually weeks or months, and then fade away and recur annually, or Mars annually. And so those behaviors were very suggestive of liquid water, sort of what you expect out of seeping water, but it's been a real puzzle to understand how you could get liquid water on the Martian surface today. It's extremely cold and dry.

I saw that there was another study by other researchers who had already determined that these RSLs probably contained no more than 3% water. And it sounds like what you guys have come up with puts the figure even lower than that. Well, I would say that what we've come up with shows that essentially what we're seeing in high-rise images are granular flows. There may be water involved in triggering them in some way. That's not fully understood. I don't think that from our results, we can put a hard number on abundance, though. How are you able to come up with this conclusion? And I hope you'll talk about this central concept called the angle of repose. Essentially, the idea is that if you heap up granular material or any material high enough, it will eventually get to a point where it's too steep to support itself and then it will fail and slump down the slope. So, for instance, if you imagine pouring a pile of sand onto a table, you would heap up the sand into a cone and then eventually the sand would get too steep and slump down the slope.

And sand dunes actually work much the same way in that the slip face of a sand dune is controlled by sand heaping up as it blows in the wind and eventually failing and slumping down that steep slip face. And it produces a fairly characteristic angle. It depends a little bit on the type of sand and the angularity of the particles, but that's called the dynamic angle of repose. You know, when I was a kid hanging out with my friends at our favorite Southern California beach, we had a game. We would pile sand up, dry sand around a stick, and then scrape away the sand to see how long we could keep the stick standing. And obviously, you could scrape away a lot more if that sand was wet. Yeah, that's right. So the dry angle of repose is relatively characteristic. The wet angle of repose, when you have sand, of course, it gets sticky.

What we found is that the RSL occur on slopes that are, or they end on slopes that are essentially the dry angle of repose for sand. You said though, that there's a possibility that water may still play some kind of a role, but it, it's not the amounts of water that, that I'll admit a lot of us wanted to believe might be in these slopes. Yeah. So there are, there has been a detection of hydrated salts in RSL at several locations. So those are salts with water bound into the structure. And then there's also clearly there's something that's making them behave in a seasonal manner so that they recur and fade every year. And so water in some form, whether it's as hydrated salt or maybe a trace of liquid, may be involved there. hydrated salt or maybe a trace of liquid may be involved there. But it's very difficult to see how large amounts of liquid water would be consistent with these slope results that we found.

Is there any good news in this? I mean, there was some talk in your paper about what it might mean for planetary protection. Well, I think that that's an area that may need more research, but certainly if there's less water and if the water is only a small amount of Delacroix solution and very salty, it would be a less habitable environment. Meaning maybe that it might be safe or at least safer to run a rover up to areas like this? Yeah, potentially. I think that that's something that now really needs to be given some consideration. What do these findings say about what we know about the amount of water that is, if not on the surface, at least not far from the surface, not far below the surface of Mars?

Mars is, in one sense, a water-rich world because there's a lot of ice, but it's also very cold and dry. And so we've known for quite a while now that there's ground ice widespread and shallowly below the surface. The Phoenix mission dug it up a few centimeters down at their landing site. But overall, this finding of essentially dry flows really helps RSL actually fit in with the way we understand the rest of Mars as a cold, dry place. Colin Dundas of the U.S. Geological Survey. When we return, I'll ask him about the good to be found in this dry report from Mars. This is Planetary Radio. Hi, this is Casey Dreyer, the Director of Space Policy here at the Planetary Society. And I wanted to let you know that right now, Congress is debating the future of NASA's budget.

The House has proposed to increase NASA's budget and also increase planetary science in 2018. The Senate, however, has proposed to cut both. You can make your voice heard right now. We've made it easy to learn more if you go to planetary.org slash petition2017. Thank you. Learn more if you go to planetary.org slash petition2017.

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Welcome back to Planetary Radio. I'm Matt Kaplan. We had such hope. Recurring slope lineae sure look to a lot of people like evidence of water, occasionally running down hillsides on Mars. A study led by Colin Dundas has thrown sand on that conclusion. He led a team that worked with data from the wonderful HiRISE camera on the Mars Reconnaissance Orbiter. We've got a link to their paper in the journal Nature

on this week's show page at planetary.org slash radio. Rich Zurich, the Mars Reconnaissance Orbiter project scientist, said about this report that it's likely that on-site investigation of these sites will still require special procedures to guard against introducing microbes from Earth. And he says, really, unless we get a close-up look at them, we may not fully be able to answer what's going on here. I mean, would you agree with that?

Yeah, I think that's true. What we found is consistent with RSL having little or no liquid water, but that's a difficult thing to definitively prove. And obviously planetary protection, we want to be careful in our exploration and not contaminate any possible water. And so although what we found is consistent with very little or no water, it may still be necessary to take precautions before exploring RSL. All right. So even if you and your co-authors have removed some of the excitement from this

particular feature that is found on Mars, has it reduced your enthusiasm for the red planet at all? I mean, you study a lot going on in that world. Not at all. I think I actually find it very exciting and interesting that Mars is so different from Earth. We often say that Mars is an Earth-like planet, but I think some of the things we're finding lately show that Mars is really a Mars-like planet. It's got a lot of its own unique processes and features, and some of them resemble features formed by liquid water, some of them don't. And I think it actually makes it more of an interesting puzzle that way. I saw in your bio that one of the other things that you look at is the evidence of floods, long-ago floods in Martian outflow channels. And can there be any doubt now with all of the work that has been done that this was once a water-rich world with lots of liquid water on the surface? I think that the evidence for ancient water is a lot stronger than the current and recent past.

For instance, a lot of the things that the rovers have found, curiosity and opportunity, appears to require groundwater or flowing surface water. So that points to an ancient Mars that was very different and wetter than the current surface. to an ancient Mars that was very different and wetter than the current surface. What would you most like to see happen in research that is yet to come on Mars? Well, I think that the overall direction of the research is for NASA and the community to decide. But I think it's very interesting to explore these uniquely Martian processes and understand how the current planet works. And it's one of those truisms of geology that the present is the

key to the past. And so working out all these current processes that we see on the surface today is an interesting component of that. I'd like to hear about some of the other work that you're up to. And there's a term that I came across that I'd love for you to explain, mass wasting. What does that mean? Mass wasting is essentially a fancy term for material falling down slopes. So things like landslides and debris flows and rock falls, it's a catch-all for all of those processes that affect the evolution of slopes and material going downhill. So exactly what we've been talking about. Right. So RSL are one component of that. But on Mars, there's a number of other mass wasting processes as well, active currently and active in the past. For instance, we've seen changes

in gullies and new rockfalls as well. You also look at lava flows on Mars and lava volatile interactions. Are you looking forward to the lander that's going to be reaching Mars next year that's going to be looking at sort of how geologically active Mars still is? Yeah, so insights will be very interesting. Some of my studies do relate to large lava flows on Mars. And that's an interesting subject. Mars has very large, very high flux lava flows in the geologically recent past. So millions or tens of millions of years ago. And insights, insights, insights into the structure of the crust and the nature of the mantle, I think, will help us understand the lava and volcanic eruptions on Mars. And so that's something I'll be watching very curiously.

Is this data that we just haven't really had in the past that InSight's going to be able to give us? Yeah, InSight is going to have a very good seismometer and will also be able to investigate the heat flow from Mars, which tells you about the temperature gradient and the crust and the depth to melting and so on. If you don't mind, before we close out this conversation, what first got you interested in Mars? Was it geology on Earth or have you always been a Red Planet fan? on Earth, or have you always been a Red Planet fan? I've always been a Red Planet fan. You mentioned Carl Sagan, and I actually remember reading some of his stuff when I was a kid. And I've always found Mars particularly fascinating, partially because it's Earth-like

and partially because it's not. It's always seemed like a very fascinating place to explore. You'll get no argument from me or anybody who listens to this show. Colin, in spite of the downer that it has been for some of us, thank you for doing great science. I should thank you and the team behind this paper.

Just say, keep up the good work, no matter where it takes us. Well, thanks for taking an interest. Mars is a fascinating place, and we're really enjoying trying to work out how it works today. Well, thanks for taking an interest. And Mars is a fascinating place, and we're really enjoying trying to work out how it works today. Thanks again. That's Colin Dundas. He is the lead author of this paper that has changed our view of these recurring slope lineae or RSLs on the Martian surface that probably do not contain the amount of water that a lot of us were hoping for.

But after all, science is not about hope. Science is about finding out what is. And that's plenty exciting all in itself. We're going to go on now to talking about an exciting night sky as we do every week with Bruce Betts. Time for What's Up on Planetary Radio. Bruce Betts, for the last time this year, well, he's the Director of Science and Technology. That's not going to end.

But it is the last time we'll be talking in 2017, although many of you will be hearing this in 2018. Welcome back. Happy New Year! Happy New Year indeed. Hey, we got this from Adam Kojokar in Calgary, Canada. He loved the beach setting for What's Up. Remember when we were on the beach in Coronado recently? Oh, yes. He says, you should make up a game called Where in the World, like Where in the Solar System, where we would have to guess where you are talking to Bruce. I love that idea. I'd like that, too. We'll have to come up with some mystery locations.

Well, they can try to figure it out today. It'll just be boring. It'll be really boring today. But the night sky is never boring. Oh, what a segue. Please tell us about it. Way to segue. Pre-dawn. That's where the action's happening. Pre-dawn in the east. We already had Mars and Jupiter up there. Mars is the farthest to the upper right, but again, this is low in the

east in the pre-dawn. Looking reddish, Jupiter is the super bright object that's to its lower left. They are going to get super duper close on January 6th and 7th. So you can watch them getting closer and closer together. And Mercury, making one of its apparitions, is lower down. If you kind of draw a line between Mars and Jupiter and head it towards the horizon, you will find pretty bright Mercury. But again, always tough to see Mercury because you're going to have to look low to the horizon not too long before sunrise. And then we've got another meteor shower coming up, the Quantra Tids. Always one of the most fun to say or challenging.

It peaks on January 3rd and 4th. So 3rd and 4th has a relatively sharp peak. In other words, you want to look during that time around the third, fourth. There is some moonlight that'll make it trickier, but it's a pretty good meteor shower. Speaking of meteor showers, John Leindecker in Aurora, Colorado. Matt and Bruce, I just wanted to say that I was on a flight from Denver to Minneapolis on the evening of the 13th, December 13th, and had a spectacular view of the Geminids meteor shower, easily one per minute, if not more. He estimates he saw 30 to 40 meteors on that

flight. Neat idea. We'll book one next year. Yeah, that'll be a great mystery location. Indeed it will. We move on to this week in space history. It was this week in 2004 that the Stardust spacecraft flew through the coma of comet Wild 2 and collected samples, which were then returned to Earth for analysis. We move on to Random Space Fact! All right, I've got my final in the episodic telling of Random Space Facts, what's happened since the beginning of planetary radio that started in November of 2002. We moved to the moon. Amazingly, there have been 13, or depending on how you count different pieces of missions, you can get a little bit bigger, a little bit smaller number, but 13 missions from five different space agencies that have gone to the moon since the beginning of planetary radio. Good job, Matt. Thanks for making that happen.

It has been a pleasure. Can we do this again for our 16th anniversary? Sure. It's fine. I mean, it's interesting for me because, like with the moon, my gut feeling was not that there were 13 missions to the moon, but, by gosh, there were. Yeah, with many more to come. Indeed. We move on to the trivia contest. I asked you, in mythology, who is the father of Phaethon,

for which the asteroid 3200 Phaethon is named? How'd we do? You did both pronunciations there, Phaethon or Phaethon and Phaethon or Phaethon. And that was very good of you because as we heard from Daniel Cazard, he makes a compelling argument citing the original Greek that the correct spelling and pronunciation are Phaethon. Yeah, I was a little confused by that. We'll say that either one is correct, and since it's not the answer,

we don't really care how people say it. Phaethon! Wesley Combs in Johnson City, Tennessee, responded with, Phaethon was the son of Helios, the sun god. He adds his mortal mother, Climene, always thought he was a very bright child. Is he correct about this with his answer of Helios? That is correct. Helios, indeed. Congratulations, Wesley.

You are a first-time winner of the Space Trivia Contest. And that means you're going to be getting that stunning Planetary Society T-shirt and a 200-point itelescope.net account. Wesley says he loves the show. Congrats on 15 years. That's right. Yay. I got a few more. Bob Klain in Chandler, Arizona.

He says Helios' reaction seems a little bit extreme. He just had the chariot keys taken away for a week for doing the same thing. Nathan Hunter, Portland, Oregon. Phantom was also, he says, the name of a type of carriage, a Volkswagen automobile, and a hypothetical planet whose destruction supposedly led to the creation of the asteroid belt. Hasn't that sort of been discounted, that theory? Yes, that has been discounted. It's thought the asteroid belt never was assembled into one big object and then broke apart, although individual asteroids have been broken apart. All right.

We got a little bit of competition for our poet laureate, Dave Fairchild, this week. It came from Kay Gilbert in Manhattan Beach, California. Said Phaethon to Helios, Dad, let me drive the sun chariot. Rad. But he threatened the earth, skills not given at birth. So Zeus gave him the thunderbolt. Sad. But we did hear from Dave Fairchild as well.

Phaethon was his father's son and stole his daddy's car. He tried to drive it in the sky, a flaming solar star. While Helios exclaimed in rage, you foolish teenage dolt, Zeus was forced to shoot him down with crackling thunderbolt. And we still have one more, because it's just nice and profound. From Andrew Planet, yes, in Gibraltar. Or is it in Gibraltar or on Gibraltar? It's the Rock of Gibraltar. He simply says, begotten from such stars are we all children of some celestial titans. Oh, that's nice.

The name was given to Phaethon because it was the closest asteroid perihelion at the time and still has the closest perihelion or closest inner point to the sun in its orbit of any named asteroid. So hence they picked son of Helios, sun god. How very apt. Speaking of apt, actually it says nothing to do with apt. What was the last successful Soviet mission to the moon? Last successful Soviet mission to the moon. Go to planetary.org slash radio contest.

You have until the first Wednesday in January. That's January 3rd at 8 a.m. Pacific time to get us this answer. And we will send you, this is really cool, an itelescope.net account, of course, which as you probably know now, you can donate if you like to an astronomy club or a school or anybody else if you don't want to use it yourself. But feel free to use that worldwide network of telescopes operated on a nonprofit basis to do your own research. It's a couple hundred dollars.

And then I have another great gift. Wait, though, I have to get it. It's behind me. Don't go away. Here on the desk. As you will remember, we had a, what do you call it, a white elephant gift exchange at the holiday party at the Planetary Society. We did indeed. Well, our colleague Barbara donated her gift as a planetary radio prize. So here it is. It's, you know, those magnetic poetry

kits that you can, you get all kinds of words and phrases and you can put them up on the refrigerator or wherever else you like. Well, this one is the Space Series from the makers of the original magnetic poetry kit, over 200 free floating word magnets. This will be yours if you get the answer right and you're chosen by random.org. It's really cool. This will be yours if you get the answer right and you're chosen by random.org. It's really cool. It took all of my willpower not to just open this and keep it and start spelling stuff out on our refrigerator here at home. I'm impressed.

Anyway, those are the prizes for this week. And I think that wraps us up. All right, everybody. Go out there, look up the night sky, and think about your space New Year's resolutions. Thank you. And good night. I'm going to have to think about it. It may take me about a year to come up with my resolutions for this year, but happy new year regardless.

He's Bruce Betts, the Director of Science and Technology for the Planetary Society, who has joined us once again, as he did 52 times in 2017, for this edition of What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its mythic members. Daniel Gunn is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. Help us close the year in great form by giving Planetary Radio a rating or review in iTunes or wherever you hear us.

I'm Matt Kaplan. Clear skies!