Planetary Radio • Jun 03, 2020

Crew Dragon Thrills While Mars Chills

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On This Episode

Edgard rivera valentin

Edgard Rivera-Valentín

Staff Scientist for USRA Lunar and Planetary Institute

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Kaplan mat headshot 0114a print

Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

This episode opens with a special message about The Planetary Society’s response to recent news, followed by a period of silence that marks the unjust loss of George Floyd and other black men and women. In our regular coverage, we celebrate the successful launch and arrival of the Crew Dragon spacecraft at the International Space Station. Then it’s off to Mars with planetary scientist Edgard Rivera-Valentin. A team led by Ed has learned that it may be safer for robots and humans to visit the Red Planet than was thought.

Liftoff of Bob Behnken and Doug Hurley
Liftoff of Bob Behnken and Doug Hurley A SpaceX Falcon 9 rocket lifts off from Kennedy Space Center, Florida carrying NASA astronauts Bob Behnken and Doug Hurley on 30 May 2020. The mission, known as Demo-2, is the first human spaceflight to the International Space Station from the U.S. since the end of the Space Shuttle program in 2011.Image: NASA / Joel Kowsky
The SpaceX Crew Dragon approaches the International Space Station
The SpaceX Crew Dragon approaches the International Space Station Astronauts Doug Hurley and Bob Behnken of NASA's Commercial Crew Program were aboard the SpaceX Crew Dragon as it approached the International Space Station. The Crew Dragon's nose cone is open revealing the spacecraft's docking mechanism that would connect to the Harmony module's forward International Docking Adapter.Image: NASA
Two New Expedition 63 Crew Members
Two New Expedition 63 Crew Members NASA astronauts and Expedition 63 crew members (from left) Bob Behnken, Doug Hurley and Chris Cassidy during a news conference on the International Space Station.Image: NASA
Recurring slope lineae in Newton Crater, Mars
Recurring slope lineae in Newton Crater, Mars This image from NASA's Mars Reconnaissance Orbiter show recurring slope lineae — narrow (0.5 to 5 meters, or 1.6 to 16 feet wide), relatively dark-toned features that form on steep (25-40˚), southern-hemisphere slopes, and that appear in early spring. They grow longer in the downslope direction during spring and summer, and fade during autumn and winter.Image: NASA / JPL / UA / Emily Lakdawalla

Related Links

Trivia Contest

This week's prizes:

A Celestial Buddies “Little Earth” plush toy just like the one on the International Space Station that will be brought home by Bob Behnken and Doug Hurley when they return to big Earth in their Crew Dragon spacecraft.

Little Earth Buddy on ISS held by Bob Behnken

This week's question:

What was the last two-person, orbital spaceflight launched from the United States?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, June 10th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

Who is scheduled to be the first non-American astronaut to launch on a SpaceX Crew Dragon spacecraft?


The winner will be revealed next week.

Question from the May 20 space trivia contest:

Approximately how many days did LightSail 1 spend on orbit?


LightSail 1 spent 25 days orbiting Earth.


Mat Kaplan: Crew Dragon thrills while Mars chills this week on Planetary Radio. Welcome. I'm Mtt Kaplan of the Planetary Society with more of the human adventure across our Solar System and beyond. That opening teaser line about thrills and chills would normally have been a very appropriate way to start this week's show. But events of the last few days have made it seem somewhat trite. It has been a week of triumph and shame of humanity at its best and very nearly its worst.

Mat Kaplan: Like many of you, all of us at the society believed this would be a time to celebrate as humans returned to space on a new ship. It is that, of course and we will celebrate shortly. But the success of SpaceX and NASA with Crew Dragon has been overshadowed by other news, we've struggled with this. Planetary Radio and The Planetary Society generally look outward and upward. But we do this in concert with and on behalf of men and women around the world.

Mat Kaplan: Our mission statement begins with empowering the world's citizens. Yet there are too many of the world's citizens for whom empowerment is far beyond their reach, for whom even survival is not a reliable outcome. My colleagues and I have spent the last few days considering how we can do more to advance true empowerment, the kind that will create security, respect, honor, and opportunities that will give everyone space in their lives to look up in wonder. We have some great ideas, but we're just getting started.

Mat Kaplan: I hope you'll also read the statement by our CEO Bill Nye. Most of all, I hope you'll hold us to this commitment. It begins with a small gesture here on Planetary Radio. Like many other podcasts, broadcasters and networks, we will now offer eight minutes and 46 seconds of silence. That's how long it took for George Floyd's life to end in agony against the pavement. I'll be back immediately afterward with all of what would have been this week's episode, including a conversation with planetary scientist Edgard Rivera-Valentin about surface water on Mars. Yes, a little of Robert Behnken and Douglas Hurley's trip to the International Space Station. This is Planetary Radio.

Mat Kaplan: (Silence).

Mat Kaplan: Thank you for staying with us. Chances are good you were watching on May 30th as Falcon 9 lifted the Crew Dragon spaceship piloted by Bob Behnken and Doug Hurley. You may also have seen their arrival at the International Space Station. If not, I've got a brief treat for you. Here are just over four minutes of heavily compressed highlights beginning, where else? With the last seconds of the countdown.

Speaker 2: Space X Dragon, we're go for launch. Let's light this candle.

Speaker 3: 10, nine, eight, seven, six, five, four, three, two, one, zero. In position, lift off of the Falcon 9 and Crew Dragon. Go NASA! Go SpaceX! Godspeed, Bob and Doug.

Speaker 4: America has launched and so rise of American spaceflight. With it, the ambitions of a new generation continuing the dream. 20 seconds into place, stage one propulsion is nominal.

Speaker 5: T-plus 30 seconds into this historic mission. Flying crew onboard Dragon and Falcon 9 and look at them go!

Speaker 6: Falcon power, tom three nominal.

Speaker 7: Confirmation of C-co second engine cutoff.

Speaker 3: Now, we are waiting for our first stage to make its way to our drone ship Of Course I still Love You.

Speaker 6: Dragon SpaceX, nominal orbital insertion.

Speaker 7: This is confirmation, nominal orbital insertion.

Speaker 2: Dragon copies, nominal orbital insertion.

Speaker 7: Station one look employ.

Speaker 3: What you're seeing on your screen is a live view of our drone ship where our first stage will be coming down.

Speaker 8: Falcon 9 first stage, successful lands aboard Of Course I Still Love You.

Speaker 3: There you can see on your screen, Falcon 9 has landed. This is the first Falcon 9 to carry humans to orbit so very exciting for us. As you can see on your right screen, Bob and Doug are still making their way to their targeted orbit.

Speaker 8: I won't need a Recovery One.

Speaker 3: So exciting today.

Speaker 8: Hi Wendy.

Speaker 7: It doesn't stop.

Speaker 3: It does not stop.

Speaker 7: So we're closing in at less than a 10th of a meter per second at this point. You can see the the surface section Draco's just doing all these very small minor attitude corrections. Really the autonomous docking system at work, making sure that the vestibule on the south capture system is lined up with IDA 2, it's the international docking adapter. We are just five meters away. Again we're racing that sunset as Dragon continues to close, four meters to go. Shadows of the space station on the vehicle, two meters.

Speaker 7: We're inside the hands off point, the chop crew hands off point, one meter to go. Soft capture complete.

Speaker 9: Dragon in sequence, soft capture confirmed. Standby for retraction and docking.

Speaker 2: And advised.

Speaker 7: And we just heard, it soft capture we have docking that coming at 7:16 AM Pacific Time with the Station and Dragon flying 262 statute miles right over the border between northern China and Mongolia.

Speaker 10: We have Bob Behnken from SpaceX demo two mission entering the International Space Station.

Speaker 11: Followed by Doug Hurley.

Speaker 6: And Station Houston, we see you. And it's a great looking photograph. So thanks for that standby, One. We'll call you when we're ready for the event the next few seconds.

NASA Administrator James Bridenstine: Station. This is the NASA administrator. Can you hear me?

Chris: We hear you loud and clear, sir. Welcome to the space station.

NASA Administrator James Bridenstine: Thank you, Chris. It's good to see you. Welcome to Bob and Doug. I will tell you the whole world saw this mission. We are so so proud of everything you have done for our country and in fact, to inspire the world.

Chris: We sure appreciate that, sir. It's obviously been our honor to be just a small part of this. We have to give credit to SpaceX, the Commercial Crew Program, and of course, NASA. It's great to get the United States back in the crewed launch business. We're just really glad to be on board this magnificent complex.

Mat Kaplan: Highlights of the launch docking and welcoming of Bob Behnken and Doug Hurley on the ISS. We congratulate NASA and SpaceX on this historic achievement, and we look forward to it becoming commonplace.

Mat Kaplan: We can thank Emily Lackawala for suggesting the return of Edgard Rivera-Valentin to our show. Emily pointed me to great research led by Ed. That may mean that Mars is a much safer place for robots and humans to visit. Not safer for the robots and humans, but for any native Martian life that could still exist on or just below the surface of the Red Planet. It was last January that Ed joined five other planetary scientists here. Each of them talked about great science goals for a world in our solar system.

Mat Kaplan: Ed took Mercury back then. This time, our conversation was inspired by his team's paper, titled, Distribution and Habitability of Metastable Brines on present day Mars, don't let that intimidate you. I think you'll enjoy this new session with Ed, who is a scientist for the University's Space Research Association at the Lunar and Planetary Institute.

Mat Kaplan: Ed, welcome back to Planetary Radio. I did not know that we'd be talking again so soon. But then I didn't know that you had this great bit of research that was about to be published in Nature Astronomy. Congratulations on this to you and your whole team.

Edgard Rivera-Valentin: Thank you. Thank you very much. Thank you for inviting me back.

Mat Kaplan: It's a pleasure, and this is fascinating work. In fact, there's something about this research that is nearly as fascinating is your conclusions that we'll get to in a moment. I read in your Great Nature Astronomy blog posts that the team actually set out to investigate something else all together.

Edgard Rivera-Valentin: Correct. So when we started in this project, our goal was to actually look at where, when and for how long could there be a stable brine on Mars because we were trying to answer the question, what is the role of these types liquids in making some of these what we've call slope failure events that we're seeing on Mars.

Edgard Rivera-Valentin: A good example of one would be these Recurring Slope Lineae. At the time when we started doing this research, Recurring Slope Lineae were very indicative that there was liquid water active on Mars today because they were forming always in spring and summer. They were forming on crater walls that were facing the equator. Those are the crater walls, they get the more intensely heated by the sun. They grew over time, they darkened, and then they faded back to the background color. So we when saw these, we were like, "Oh my gosh, there's liquid water on Mars." But in order for it to be liquid water, it has to be brine. That's how you're going to have something stable under Martian conditions today.

Edgard Rivera-Valentin: But as time has gone on, and we've gotten more data on these features, were going, "Well maybe they're not made by liquid water. There might be something else involved that are making these." But by then, we had all of this data. So we had to answer another question with it. That is are these liquids habitable?

Mat Kaplan: That was what led us to to this conversation today. You weren't alone in that excitement about those RSLs. There were a lot of us at the Planetary Society and among our membership, and outside our membership, who were pretty thrilled by this possibility. I guess the possibility, it is still possible, right? That this is a liquid that we see appear and disappear on these slopes?

Edgard Rivera-Valentin: So the best data we have right now is more suggestive that the flow itself is not made of liquid, but rather maybe it is instigated or triggered by a liquid forming. So one of the things that I guess is my soapbox to stand on whenever we talked about flows on Mars, is that although Earth is a great analog when we're looking at Earth geology and try to look out in the Solar System and do these comparisons with other Solar System bodies, Earth has more gravity than Mars.

Edgard Rivera-Valentin: Gravity is a very important factor in fluid mechanics. So something will flow differently under a different gravity regime. On Mars, because the gravity is about a third compared to Earth, things don't need a fluid. Things don't need a lot of liquid inside of it to make it look as if it's a flow, as if it would have been the flow on Earth. So the same thing on Earth does not need the same amount of liquid to look like it on Mars.

Edgard Rivera-Valentin: So the type of research that people have been, doing a lot more going through all these images, it's showing that Yeah, they're probably very dry. The dark stuff that you're seeing is actually the regolith that's under the surface. We know that regolith is much darker than the surface stuff. But that type of flow still need an instigation, still needs a trigger to start it off. One of the ideas that we have is that you might still form a liquid. As that liquid quickly evaporates away, that energy is what could be used to instigate the flow.

Mat Kaplan: That's very interesting. Well, at least a little liquid is better than none at all, I suppose.

Edgard Rivera-Valentin: Exactly, looking.

Mat Kaplan: Let's talk about these brines. I'm a native of Southern California where we don't have much need to put salt on our roads. But that's a bit of what we're talking about, aren't we? I mean, what are you referring to when you say a brine?

Edgard Rivera-Valentin: Right? So in planetary science, when we're talking about brines, we're talking about very salty liquids. I'm a chef. I like cooking. I'm not literally a chef, because it's not my professional, but I'm like cooking a lot. People for Thanksgiving, like to sometimes take their turkeys and put them in a brine. That is water with a truckload of salt inside of it. That's what we're talking about when we say brine, it's a liquid with a lot of salt in it.

Mat Kaplan: So I note that you frequently refer to stable liquids. So I guess a brine doesn't need to be water-based.

Edgard Rivera-Valentin: It's a good catch. I try to be a little bit precise when I say stable liquids for Mars just because there might be something else that allows liquid water to exist besides salt. The cool thing about salt is that it changes the freezing temperature of the liquid. So when you have a brine, despite the fact that you need zero degrees Celsius to freeze something, well, brine could reduce that to maybe minus 10 degrees celsius. Those people who are in the north, they're used to having to throw salt into the street when it snows. The reason they do that is so that the snow goes back into the liquid state. That's because the salts change that freezing temperature of that mixture. Now you can have liquid again whereas you would have had ice under the temperatures that there exists there.

Mat Kaplan: Very much like those roads that I didn't grow up with. I don't think he did either, actually. But I noted, and this was an image I'd never seen before, an image that was connected to some of this work was looking under the Phoenix Lander, may it rest in peace. I'd looked under the Phoenix Lander before with others to see the ice that it found just below the surface. But this was something I hadn't seen, what looked like little drops of condensation.

Edgard Rivera-Valentin: Yes, that picture when they came back, super excited me because at that time, I was a graduate student and doing brine research. I was like, "Yes, we have evidence." My work here is done or just started. But the cool thing too, that picture is neat to let us know that you could have liquid water stable on Mars, it's going to be a brine. But we also have to remember that those droplets formed very shortly after the spacecraft had landed. So that area was very warm.

Edgard Rivera-Valentin: The idea we have is the Phoenix landed, it kicked up some of the ice. The ice fell onto the struts. It started forming those droplets and a great paper by Renaud back in 2008, if I remember correctly, they actually have a sequence of images showing those drops coming together. So we were seeing them flow and then evaporate away. It looked like very strong evidence that they should be liquid water. In popular science, we try to be slightly skeptical when we talk about liquids on Mars. So you'll hear me say things like, "We think these were liquid droplets." There are people that don't think they are and unless we have some sort of spectrometer taking data of that droplet as it was forming, and it said H2O, we'll just keep saying it looks like, it behaves like a brine.

Mat Kaplan: Extraordinary claims require extraordinary evidence. Right?

Edgard Rivera-Valentin: Exactly.

Mat Kaplan: More of my conversation. With Edgard Rivera-Valentin about liquids on the surface of Mars is coming up after a break.

Kate: Hi, this is Kate from the Planetary Society, how to space spark your creativity. We want to hear from you. Whether you make cosmic art, take photos through a telescope, write haikus about the planets, or invent space games for your family. Really any creative activity that's space-related, we invite you to share it with us, you can add your work to our collection by emailing it to us at [email protected]. That's [email protected]. Thanks.

Mat Kaplan: Tell me about the model that was developed out of this work that has revealed these interesting predictions about regions of Mars.

Edgard Rivera-Valentin: What we did here is we put together a climate model that is used to figure out what are the conditions on Mars when we're about to send a spacecraft, better understand the type of atmospheric conditions that entry is going to encounter. We took that type of model. We also meshed it with experimental data that we've done at the University of Arkansas that has a Mars simulation chamber, and has been looking at the stability of these brines, and trying to understand it from a thermodynamics perspective.

Edgard Rivera-Valentin: So I took all of the actual experimental data, put it together with the climate model, and then meshed everything together to try to figure out okay, given this temperature, given this relative humidity at the surface, compared to the experimental data where we saw liquid stable, would a liquid be stable, yes or no? Then we track that liquid over time to try to figure out what its chemistry is, and what its temperature is. That allowed us to could see that at most. The stable brines that can form our Mars will only ever reach a temperature of about 225 Kelvin. We think that, "Well, okay. Life as we know it."

Mat Kaplan: There's that phrase again.

Edgard Rivera-Valentin: Yeah, it's a very important phrase. But typically life as we know it needs a temperature a bit higher than 250 Kelvin for it to be able to replicate and metabolize. So to actually be alive. Anything lower than that, and it starts getting a little fuzzy whether it's just metabolizing very slowly or if it just completely stopped replicating or if it went into a spore phase. But that temperature is used by international policy when we're trying to consider planetary protection. When we're trying to consider okay, if we're going to send spacecraft there, do we have to be extra careful because the conditions might allow for life as we know it to exist there.

Mat Kaplan: How has this been received in the planetary protection community? Because, I mean, this indicates, as you've said in the research, that putting robots and maybe humans on Mars, as long as they don't dig down too deep or they're careful when they dig down deep, that this might be safer for anything that may still be on Mars than we thought.

Edgard Rivera-Valentin: So I actually haven't heard back from people. I don't know if I should be scared or not. But I know when we're thinking about sending any type of spacecraft into these type of environments, we are very cautious and rightfully so. Right? Because if we send a spacecraft that is contaminated in any way, and it goes into an environment, even if the best models we have, even if the best experiments we have go and show us, okay, we only expect a liquid there that isn't habitable, so it's okay.

Edgard Rivera-Valentin: But some random happenstance happens, and you just took a bug to Mars and that bug suddenly was okay living in that environment. You send another spacecraft, and you go, "Oh, I found life on Mars." Oh, but no, it's actually Earth contamination. You just ruined one of the most important questions that we have in astronomy and planetary science and that is are we alone in the universe. So we are rightfully cautious when we send a spacecraft out there.

Edgard Rivera-Valentin: I would say that this work isn't to say that we shouldn't be cautious at all, but rather that we don't have to be extraordinarily extremely cautious to the point where if we see an RSL or if we're in an area where there might be a liquid, we need to be kilometers upon kilometers away just to be safe. We maybe can get a little bit closer, maybe we could send a helicopter to take a picture of it. I'm hoping there's maybe newer avenues that will allow us to explore these regions.

Mat Kaplan: Gee, if only somebody was sending a helicopter to Mars, wait a minute, we are.

Edgard Rivera-Valentin: Yeah, right?

Mat Kaplan: It's not just a hypothetical. This had to be taken into consideration for Curiosity, the Mars Science Laboratory, because it was supposed to go through an area with some RSLs, wasn't it?

Edgard Rivera-Valentin: Correct, so Curiosity. As it was probing along, it took some very interesting pictures of these dark streaks emanating from bedrock. When those pictures ended up going all the way up to the Contra Protection Office, I'm not involved with MSL. But from what I read on the news, it caused a lot of stir because when you see those type of features, you immediately think, "Oh, they might be liquid." So it would have meant that MSL would have had to completely change its trajectory instead of going up where it was going.

Edgard Rivera-Valentin: It would have had to go somewhere else or worst case scenario, just completely stop. More data came in, more orbital data came in. There was a lot more research done. We saw, "Okay, that's probably not liquid what you're seeing, most definitely not so it might be safer, but just be cautious."

Mat Kaplan: Then of course there's Perseverance leaving for Mars this summer, followed we hope in a couple of years by the Rosalind Franklin Rover from the European Space Agency. Perseverance is designed to go to these areas and. Rosalind Franklin is has got a drill to go meters down. Do we need more data or are you fairly confident now partly based on your model that they can do the work they need to do assuming we've sterilized them as well as we can back here on Earth?

Edgard Rivera-Valentin: So I would say that the work that we've done definitely says that we don't have to be extraordinarily cautious to the level of do not send a spacecraft here, because it seems as if the type of liquids shouldn't allow for what we call for contamination. Do we need more data to be 100% sure? Of course. The one type of feedback I've gotten from this type of work is from the biology community who brings up a lot of these micro-environments where they have been seeing life exist even though its surroundings and the bulk environmental conditions would say life shouldn't, this itty bitty environment in this itty bitty other place is suddenly just right. So that is still something that we need to consider.

Edgard Rivera-Valentin: Because again, if we accidentally contaminate ,that would ruin a lot. But the more data we have from experiments, the more data we have in situ, in situ environmental data on Mars will definitely help improve these type of models, and give us better insights as to how cautious we need to be where we go. If we're actually trying to answer the question, is there active liquids on Mars? Then it also is informing our observation strategies. Where do I need to look? When do I need to look to make sure yes, liquids are forming there,

Mat Kaplan: According to your model, we're not talking about everywhere on Mars, right? That we might find even these brines, which appear to be so, that may be so unfriendly to life as we know it.

Edgard Rivera-Valentin: Correct. So there's only certain places on Mars where the environmental conditions are just right to allow for brines to actually be stable. Not only that, when they're stable, it's not they're stable for hours upon hours on end, they're only stable for maybe about a percent or two throughout the year. At most, they're stable for six consecutive hours. That only happens in the very special regions up in the northern hemispheres of Mars. But more typically, wherever they can exist and are stable, they'll only be stable for maybe an hour or two.

Mat Kaplan: Wow.

Edgard Rivera-Valentin: That's the more typical value that we're seeing. So it's very short-lived liquids, because Mars is so, so, so dry, that once it gets a little bit too hot, you will evaporate that brine very, very quickly.

Mat Kaplan: Does your research have anything to say about what may be going on, a couple of meters three meters down below the surface? I think you're only talking about the surface and maybe a handful of centimeters down, right?

Edgard Rivera-Valentin: Right. So when I talk about is surface and what we call the shallow subsurface. The shallow subsurface is the part of the soil that actually can talk to the atmosphere and is actively exchanging water with the atmosphere. Once you get something about below 10 centimeters or so, that activist change, slows down very, very quickly. It's no longer seeing the day, it might be seeing something on the order of the season. Once you go below a meter or more, you're you're really not exchanging water vapor too much with the atmosphere at all, even throughout the year. Down there, that ends up being a whole new world to poke Aladdin, where other people are doing research to figure out if there could be larger bodies of water down there.

Mat Kaplan: So if Mark Watney, The Martian comes to you or calls you on the radio and says, "Hey, can I start planting and fertilizing potatoes on Mars?" Or maybe the asparagus that NASA Chief Scientist Jim Green said might grow better there, according to the most recent research, I mean, what would be your advice?

Edgard Rivera-Valentin: I wouldn't grow any. I wouldn't grow anything on Mars and try to eat it, but I am extra cautious. The type of salts that I'm looking at that form these brines, potassium perchlorate, that's the same type of ingredient that is in a lot of toilet bowl cleaners. I wouldn't drink my toilet bowl cleaner, so I wouldn't even touch that.

Mat Kaplan: I don't know, it could turn out that it works against COVID-19. Too soon?

Edgard Rivera-Valentin: True, there you go.

Mat Kaplan: So we've talked about Mercury with you, now Mars, you've possibly made it a safer place for us to visit. What else is happening and what's ahead for you and your research?

Edgard Rivera-Valentin: On Twitter, you can find me at @PlanetTrekkie. I use that handle because I love to trek the planets. Fundamentally, I do what's called system science. At the base of everything, I like to do math, but I specifically like to understand how these different things can come together to make that which you are observing. So instead of doing just the geochemistry or just the atmospheric science, I'll put everything together into this paper where I can look at the chemistry of the brines based on the atmospheric science that we have.

Edgard Rivera-Valentin: I talked about Mercury because I was doing planetary radar, and I was zapping mercury with radar to figure out how these ices might be stable at the poles of mercury. Is that changing over time? How deep are they? Where could they have come from? Putting all of that picture together with this added data. Other type of work I also do, I'll observe icy moons. So I have a project using Cassini data, may it rest in peace, of the Saturnian satellites. I use that data, I'll count the craters. I'll also use another spectrometer that Cassini has that looks like at the ice space distribution on the moon.

Edgard Rivera-Valentin: That lets you know something about how old a crater could be. Because when the crater forms, it changes the ice that is around it. Over time, the ice will come back to it's amorphous phase. So I have basically a clock, and I have craters there so I can start putting together what the impact crating rate is for the Saturn system that lets me know how old certain ages are. Then I can put everything together and go back to the bigger question we have out there. Okay, are the Saturn's rings young or old? That's the type of question I like to look at, put all of these little bits together to figure out how all of the system pumps and gets you what you observe.

Mat Kaplan: Sounds like you're at home all over the solar system.

Edgard Rivera-Valentin: Yes, it's fun.

Mat Kaplan: All right, Ed. Thank you. I'm very glad that I was able to get you back for this. Again, congratulations to you and the team that put together this model and has come out with these new data and conclusions. We'll have lots of great links to this work on this week's show page at Ed, live long and keep trekking.

Edgard Rivera-Valentin: Thank you so much. You have a good day

Mat Kaplan: You too. Planetary Scientist Edgard Rivera-Valentin works for the University's Space Research Association at the Lunar and Planetary Institute. Great links to his work and other topics we cover on this week's show, our time for What's Up on Planetary Radio. Bruce Betts is the Chief Scientist of the Planetary Society. He is here. One more time, well one more time, many more times, I hope.

Bruce Betts: What? What do you know that I don't know?

Mat Kaplan: Nothing. Nothing at all. Nothing. No secrets here. Anyway, he's here to tell us about the night sky, and we're going to give away a copy of his new book for kids, My First Book of Planets. Welcome.

Bruce Betts: Thank you. Good to be here, Matt.

Mat Kaplan: It's especially good to have have you here this week. It's good to be with with old friends. So what's up there?

Bruce Betts: You know what's not in the evening sky? Venus, it's gone. It's gone, man. It's out of there.

Mat Kaplan: It was a heck of a show.

Bruce Betts: It was, but it'll be coming in the morning sky shortly because it's between us and the sun right now, and it'll be popping out on the other side, which puts it in the morning sky, but not quite yet. But in the middle of the night, taken over are Jupiter and Saturn, rising around 11:00, midnight, depending on where you are. They will be near the moon on June 7th, and 8th, it'll make a lovely triplet, Jupiter being the much brighter of the Jupiter-Saturn pair. A couple hours later, so quite middle of the night, Mars rises in the east, and it's getting bright. So it's now in negative magnitudes for those who play the astronomical apparent magnitude game, meaning it's brighter than the star Vega. It'll keep brightening through its opposition in October.

Mat Kaplan: So Vega is magnitude zero, right?

Bruce Betts: Yep, yep. In visible equivalent to what we see kind of. Yes. Onto This Week in Space History, it was 55 years ago in 1965 that Ed White took the first American spacewalk. 45 years ago, the Venera 9 launched, the Soviet Venera 9 that would become the first spacecraft to return pictures from the surface of another planet. In this case, Venus.

Mat Kaplan: Still such an amazing feat that they actually put something on the surface of that living or dead hell, and it's survived to take some pictures. I mean, my goodness.

Bruce Betts: Yeah, impressive. Speaking of impressive, we're going to move on to Random Space Facts! Feel like we're flying, man?

Mat Kaplan: The friendly skies.

Bruce Betts: The space station, The International Space Station has an internal pressurized volume. In other words, where the astronauts and cosmonauts hang out equal to that of a Boeing 747.

Mat Kaplan: Does that include ...I don't know if you do remember when the 747 first came out? There was a piano bar upstairs? Does the ISS, no, it doesn't have a piano, does it?

Bruce Betts: No, it just has the bar.

Mat Kaplan: Okay.

Bruce Betts: So anyway, we move on to the trivia contest. I asked you approximately how many days did Lightsail 1, the Lightsail test mission, Lightsail 1 spend in orbit. How'd we do, Mat?

Mat Kaplan: A very nice response to this one. Here is the answer delivered by our Poet Laureate Dave Fairchild. Lightsail A, later Lightsail 1 was launched into space nice and clean. It flew as a payload on ULA's rocket in May back in 2015. Despite having problems in keeping Earth contact, the sales still blossomed in June. 25 days after launch. It re-entered our atmosphere and was consumed.

Bruce Betts: Nice. I mean, not that it was consumed. But that was the plan. We knew as soon as we put the Sail out, it would be dragged down,

Mat Kaplan: Unlike Lightsail 2 that will probably come up here in just a moment because of some reaction we got from some other folks. Here's our winner, first time winner, John Georges in Silver Spring, Maryland, who responded correctly with the 25 days., A few people were off a little bit, a few people thought maybe that was after deployment when it didn't last very long, I assumed because the drag was so much increased?

Bruce Betts: Yeah, because Lightsail 1 went to a much lower orbit, and that's why we knew it was just going to be a test mission, not able to solar sail. It had a pereaps, a low point in the orbit that I forgot exactly, but it was between three and 400 kilometers. With that little tiny mass and that big giant sail, the atmosphere drags you down in a hurry. Whereas Lightsail 2 started out around 720 kilometers, or there's still some atmosphere but a lot less.

Mat Kaplan: John, congratulations, you have one a copy of Bruce's brand new book that we mentioned from Rockridge Press, My First Book of Planets, all about the solar system for kids. It's a great first book, introduction to the solar system and astronomy for that matter. It's available now I think, right, as an e-book.

Bruce Betts: It is, it just came out available as an e-book at least on Amazon. In two weeks, it'll be out as a paperback.

Mat Kaplan: Okay, well, it's going out to you, John. You should read it before you give it to some young person. I think you'll enjoy it as well. So 25 days. Burton Caldwell in New York said, "That's four more days than Sputnik one lasted." Did you know that? There's a random space fact.

Bruce Betts: That's very nice. Yeah, I had never connected those two, nicely done.

Mat Kaplan: Zippy Olson in Wisconsin, "I track the satellite every day, and I'm currently tracking Lightsail 2."

Bruce Betts: Cool,

Mat Kaplan: Thanks, Zippy, and love your comic, Zippy. Mel Powell, "You'll answer this in the 939th all time episode of Planetary Radio for ease of math, average length of episode 60 minutes." That's a bit long, but we'll let it slide. Lightsail 1 would have had to remain on orbit for an additional 14 days and three hours to hear all of our episodes end to end.

Bruce Betts: Oh my gosh. Wow. That's a lot of episodes, man.

Mat Kaplan: Mel, you made it in again with that. How could we pass it up? Martin Hadjosky, "Perhaps somewhat prophetic, the number one song on the Billboard Hot 100 both on launch day May 20, 2015 And the date the orbit finally decayed June 14, was See You Again by Wiz Khalifa and Charlie," is Puth? Puth?. I know Wiz Khalifa, but I don't know Charlie P-U-T-H. Anyway, Martin says, "How about that?"

Bruce Betts: I didn't know that.

Mat Kaplan: Finally, another poem from Jean Luan up at Fairchild Air Force Base in Washington, "Lightsail 1 accompanied by X37B, a test of the new CubeSat and the OTV. Assisted by a rocket that bears the Atlas name with 40,000 donors and a Kickstarter campaign. 25 days it orbited around the pale blue dot, proving solar sailing, demonstrating what was sought."

Bruce Betts: Nice.

Mat Kaplan: Okay, thank you everybody. Try again next time. and you might just win something great. But, Bruce, first set it up for us.

Bruce Betts: All right. We of course just had the very successful Crew Dragon Demo 2 launch. Before Crew Dragon Demo 2, what was the last two-person orbital spaceflight launched from the United States? Go to

Mat Kaplan: This time, you have until the 10th. Wednesday, June 10th at 8:00 AM Pacific Time to get us your answer. We opened the show with this, highlights of the Crew Dragon launch and arrival at the International Space Station. Maybe some of you saw the astronauts holding a little celestial buddy. Little Earth is what it's called or Earthy, little plush toy. I have the Mars version of it sitting up above my head here. We have one to give to you.

Mat Kaplan: No, it's not signed by the astronauts or anything like that. But it is exactly the kind that was brought up on the demo mission number one on crude and will be brought back to Earth by Bob Behnken and Doug Hurley when they return, in we don't know yet some number of weeks or months, could be up to four months. But we've got a picture of the astronauts with this little celestial buddy, Little Earth on the International Space Station. So there'll be three passengers on the way home. How's that?

Bruce Betts: That's really cool.

Mat Kaplan: And next week, ice cream.

Bruce Betts: Nice. Man, I want ice cream.

Mat Kaplan: Of course, you do. We're done though, you can go get some.

Bruce Betts: All right, everybody, at the risk of being thematic. Everybody go out there, look up at the nice guy and think about how fun space is. Thank you. Good night.

Mat Kaplan: It's very fun, more fun than a piano bar on a 747. Maybe they'll put one on Starship. Note to Elon. He's Bruce Betts, the Chief Scientist of the Planetary Society, who joins us every week here for What's Up.

Mat Kaplan: Planetary radio is produced by the Planetary Society in Pasadena, California, and is made possible by its members. Join them to help empower the world's citizens to advance space science and exploration. Mark Hill Veritas, our associate producer. Josh Doyle composed our theme, which is arranged and performed by Peter Slusher. Per ardua ad astra or through struggle to the stars.