Planetary Radio • Nov 18, 2020

Revealing Mars From Above, and Crew Dragon is Go!

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On This Episode

Jeff Plaut

Jeffrey Plaut

Mars Odyssey Project Scientist for Jet Propulsion Laboratory

Richard zurek

Richard Zurek

MRO Project Scientist and Chief Scientist for JPL Mars Program Office

Betts bruce headshot 9980 print

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Planetary Radio Host and Producer for The Planetary Society

Jeffrey Plaut and Richard Zurek are the project scientists for two of the most successful and long-lived Mars missions. Their orbiters, Mars Odyssey and the Mars Reconnaissance Orbiter, are still delivering great science, even after 19 years above the Red Planet for Odyssey. We’ve also condensed the first 29 hours of the first operational Crew Dragon mission into 98 thrilling seconds. You’ll get a chance to win The Spacefarer’s Handbook in this week’s What’s Up space trivia contest.

The Mars Reconnaissance Orbiter
The Mars Reconnaissance Orbiter NASA’s Mars Reconnaissance Orbiter is an orbiting spacecraft studying Mars’ climate and geology. NASA / JPL
RSL site in Melas Chasma
RSL site in Melas Chasma Melas Chasma RSL forming on a fan of fine-grained material in HIRISE enhanced color image ESP_034962_1670. NASA / JPL-Caltech / University of Arizona
Mars dunes from MRO
Mars dunes from MRO The High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars Reconnaissance Orbiter captured these sand ripples and the large dune (at center) on Feb. 9, 2009. Color has been added to make textures easier to see. This area is in Proctor Crater at 47.8 degrees south latitude and 30.7 degrees east longitude. NASA/JPL-Caltech/University of Arizona
The Mars Odyssey Spacecraft
The Mars Odyssey Spacecraft This artistic rendering shows NASA's Mars Odyssey spacecraft orbiting over Mars' south pole during its multi-decade mission to map and characterize the Red Planet. NASA / JPL
Layers in Mars' south polar cap
Layers in Mars' south polar cap This Mars Odyssey THEMIS VIS image of the defrosting layers of the south polar cap was taken on August 23, 2016. Some of the layers show the characteristic pits known as "swiss cheese" terrain. The image shows a region about 14 kilometers wide. NASA / JPL-Caltech / ASU
Expedition 64 Crew
Expedition 64 Crew The Expedition 64 crew on the International Space Station speaks to the ground shortly after the arrival of 4 new astronauts aboard the SpaceX Crew-1 mission on 16 November 2020. Front row from left: Shannon Walker, Victor Glover, Michael Hopkins, and Soichi Noguchi. Back row from left: Kate Rubins, Sergey Ryzhikov, and Sergey Kud-Sverchkov NASA

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Trivia Contest

This week's prizes:

The Spacefarer’s Handbook by Bergita Ganse and Urs Ganse

This week's question:

Mars Odyssey is the longest continuously active spacecraft orbiting another world. What spacecraft is the second longest continuously active spacecraft orbiting another world?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, November 25th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

Who gave the names to most of the lunar maria that are used today--those approved by the International Astronomical Union?


The winner will be revealed next week.

Question from the 4 November space trivia contest:

How many of the largest dwarf planet Pluto would fit inside the smallest planet, Mercury? Just a basic volume-to-volume comparison, please.


About 8.7 Plutos would fit inside Mercury in a volume-to-volume comparison.


Mat Kaplan: Decades revealing Mars from overhead, and Crew Dragon highlights, this week on Planetary Radio. Welcome, I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. We're minutes away from a great conversation with the project scientists for two pioneering Mars missions. Jeffrey Plaut and Richard Zurek will tell us how Mars Odyssey and the Mars Reconnaissance Orbiter have revealed the Red Planet and have enabled missions and discoveries that followed.

Mat Kaplan: First, though, at the top of our news, is the brilliant success of the first Crew Dragon operational mission that has delivered three NASA astronauts and one from JAXA, the Japanese space agency, to the International Space Station. What you're about to hear is condensed from roughly the first 29 hours of that mission, beginning with the Sunday, November 15 launch of Crew Dragon Resilience, atop a SpaceX Falcon 9.

Speaker 2: Three, two, one, zero. Ignition. Lift off.

Speaker 2: And Resilience rises, not even gravity contains humanity when we explore as one for all.

Speaker 2: Launch escape system is disarmed.

Speaker 2: And SpaceX copies.

Speaker 2: And [Leia 00:01:30], the words we like to hear, a nominal orbit insertion.

Speaker 2: That's right, John, nominal orbit insertion, as we mentioned, stage two, and I believe we've had a touchdown on the drone ship.

Speaker 2: We've got stage one has touched down on the drone ship in the Atlantic Ocean.

Speaker 2: SpaceX, this is Dragon on the big loop, six decimal six, four dot four hundred, hatch is open.

Speaker 2: We copy. Hatch open. Great to hear.

Speaker 2: As you can see, they do have that hatch open now. They called down. That came right at 12:02 AM Central Time.

Speaker 2: There they are, first across the hatch, Mike Hopkins, and here is Victor Glover. You heard the team here in mission control cheering to see them come across the hatch. There's Shannon Walker, and finally, Soichi Noguchi bringing up the rear. Four new members, bringing the total expedition 64 crew to a total of seven ready to increase the space station science and get to work.

Mat Kaplan: Our congratulations to SpaceX and NASA for that picture-perfect start of commercial crew operations. You can bet that Crew Dragon will return to the downlink later this week. The 13 November edition of The Planetary Society's weekly newsletter is topped by your opportunity to fly over Occoter crater on dwarf planet Ceres. The spectacular animation is derived from data collected by the Dawn spacecraft, of course. Wait until you see those salty white spots.

Mat Kaplan: We also learned last week that NASA administrator Jim Bridenstine plans to step down in January. We'll ask him to return to Planetary Radio for a conversation about what has seemed to be an exciting and productive tenure at the agency. As always, you'll find much more space exploration goodness at

Mat Kaplan: A bunch more of you were kind enough to add a rating or review to Apple Podcasts in the last week. I'd write to each of you if I knew who you were. I don't, so I hope you'll accept my thanks here, and any others of you who decide to join them will also have my gratitude.

Mat Kaplan: July 15, 1965, the first close-up pictures of another planet have just been captured during the brief flyby of Mariner 4. It revealed a Mars that disappointed many, but we were only getting started. Six years later, Mariner 9 would become the first spacecraft to orbit another world. It sent back over 7,000 images and began a tradition that has been carried on by many orbiters to follow. That family of explorers includes Mars Odyssey and the Mars Reconnaissance Orbiter.

Mat Kaplan: I invited the project scientists for these wonderful missions to join us for the conversation you're about to hear. Both have the Jet Propulsion Lab near Pasadena, California as their professional home. Jeffrey Plaut oversees science operations for Mars Odyssey, while Richard Zurek does the same for MRO. Rich also serves as chief scientist for JPL's Mars Program Office. Jeffrey Plaut and Rich Zurek, it seems like I have reason to congratulate just about everybody I talk to on Planetary Radio, but not many of the folks I talk to can be congratulated on as long a tenure, as long a record of service by their spacecraft as I can the two of you, so congratulations, and welcome to Planetary Radio, guys.

Rich Zurek: Well, thank you, Mat.

Jeffrey Plaut: Thank you. It's great to be with you.

Mat Kaplan: Just for our listeners out there, that was Rich that you heard from first and then Jeff. Let's keep it in that order for the moment, so Rich, I'll ask you first. How's the health of your veteran spacecraft?

Rich Zurek: Amazingly good after 15 years since launch and 14 years in Mars orbit. We still have all our instruments able to operate. We've had some aging and such of the spacecraft itself, but we're still ready to go for another 10 years.

Mat Kaplan: Oh, my gosh.

Rich Zurek: Yeah. We're not quite up to Odyssey's record yet, though.

Mat Kaplan: That's quite a record to meet. Jeff, you just passed 19 years in orbit at Mars. Congratulations again.

Jeffrey Plaut: Well, thank you for that. We're very rapidly approaching the 20th anniversary of the launch of 2001. Mars odyssey launched, of course, in April of 2001, so coming up here in just a few months, we'll hit that milestone of 20 years in space.

Mat Kaplan: How is Odyssey holding up?

Jeffrey Plaut: Odyssey is also doing remarkably well. We have functioning instruments, which I think we'll get into a discussion of our science instruments. Most of the elements of the instruments are still working great. The space craft is healthy, and there's still fuel in the tank, so we anticipate years more of operations as well.

Mat Kaplan: Just amazing. We will get into more specifics about the spacecraft and their accomplishments, but I want to keep it more general up front. I suppose it's understandable that Mars lander and rovers generate the excitement that they do, but this is really for both of you, would they be able to accomplish much? I mean, could they even have made it to the surface without the steadily brilliant work of orbiters like those you work on. Rich?

Rich Zurek: It's an amazing effort and definitely a team effort by many projects and many disciplines to make one of these missions a success, but the orbiters are really the ones that identify the most interesting places where landers can go, and rovers can rove, and where it's safe to do so. That's been a prime function of these two orbiters over time.

Jeffrey Plaut: Yeah, and I will add to that. Just as an example, one of the early historic accomplishments of Mars Odyssey was using its neutron and gamma ray detectors to map the distribution of hydrogen in the soil on Mars, and we identified locations in the Arctic regions where there was likely to be water ice very close to the surface. Not too many years after we made that observation, the Phoenix Lander targeted one of these zones specifically because Odyssey had made that discovery. Sure enough, shortly after landing, it was very clear there was ice just below a thin layer of the soil, just as we had predicted.

Mat Kaplan: Jeff, I so well remember those images of Phoenix digging just those few inches or centimeters down and finding that ice that, as soon as it was exposed, submlimated away pretty quickly, but there it was. We will come back to that search for water as well, I'm sure.

Mat Kaplan: It's not hard to understand why MRO, the Mars Reconnaissance Orbiter, got its name. Jeff, remind us of why Odyssey got its moniker.

Jeffrey Plaut: Of course, the year that we launched, it has a familiar ring to fans of space and space science fiction. I was on the project at the time when we were promoting our name from the generic 2001 Mars mission to something different, something a little catchier. Naturally, the idea of 2001 and a Space Odyssey came up, and we thought, "Well, let's just try swapping out a word there and make it 2001 Mars Odyssey," but of course, there's issues of copyright and intellectual property, et cetera associated with a title of a famous book and film. So, we actually got permission from Arthur C. Clarke to use that, and he was thrilled, actually, at least that's what he told us, that NASA was proposing to use a name like that for an actual Mars mission. It was win-win for everybody. We were very excited, and the name, I think has held up over the years.

Mat Kaplan: I have no doubt that Sir Arthur's enthusiasm was genuine. He was a pretty enthusiastic guy, after all. I do want to talk about the spacecraft themselves. Jeff, we'll stick with you for a second. Tell us about Odyssey. What was it sent to Mars to do, and how was it supposed to accomplish this?

Jeffrey Plaut: Well, something that a lot of the listeners may not recall or be aware of was that Odyssey was part of the Mars Program at a time when the plan was to send pairs of landers and orbiters on each launch opportunity every two years, so when Odyssey was planned originally, it was to be the orbiter that was going to accompany a 2001 lander. However, a few years prior to our launch was the unfortunate set of failures of the previous paired orbiter and lander, 1998. So, especially in view of the disappearance of the Mars Polar Lander, NASA decided, "Well, let's just stick with one of the two for 2001, and we'll make it the orbiter." We actually had a lot of pressure. We felt a lot of pressure because this was the comeback after the two failures, which was very discouraging for many of us. We were told, "You are not allowed to fail." We didn't, and in October of 2001, we got to Mars.

Jeffrey Plaut: The main task for Mars Odyssey was to study the composition of the surface materials, and we did that through two sets of instruments, one being what I mentioned earlier, the gamma ray spectrometer suite, which includes gamma ray detectors and neutron detectors, and that was mainly to measure the concentration of elemental materials, elemental periodic table in the soils of Mars in the first meter or so of the soils of Mars.

Jeffrey Plaut: The other main instrument was the camera system, which was called THEMIS, the Thermal Emission Imaging System. That camera system has a visible light camera, but its unique capability is in the thermal infrared, basically like a night-vision goggles camera, and it can take images of the surface temperatures both day and night and use the spectral information in that part of the infrared spectrum to detect minerals. That was the primary goal of the mission... was to reveal the composition of the surface materials on Mars.

Mat Kaplan: It's been a while, but Phil Christensen, the principal investigator for the THEMIS instrument has been on our show. I did see... It wasn't too long ago, just a few months ago... that you turned the spacecraft and THEMIS toward Phobos, and there's some pretty beautiful images that came out of that. Can you tell you about those?

Jeffrey Plaut: Yeah, sure. Phobos was not originally a target for our camera or for our spacecraft, but we're not the only Mars orbiter that took advantage of opportunities to point away from Mars and point instead towards the moons of Mars, Again, using the unique capabilities of THEMIS, the thermal infrared spectral imaging capability, we did capture, over the last three years now, a very interesting and complete suite of images. We have one more imaging observation to do just in a few weeks from now to complete the set.

Jeffrey Plaut: We're using, in particular, the thermal imaging capability to measure not only the composition but also how the near-surface materials respond to sunlight hitting the surface of Phobos, and we watched an eclipse of Phobos by Mars and watched how the surface then warmed up immediately after that and how, through the day, night cycles, which is about, I think, a seven-hour day on Phobos, how the temperatures change as the Sun sweeps across the surface. This will allow us to make determinations of the density and the details of the small-scale structure of the regolith, or the soil, on Phobos.

Mat Kaplan: They're beautiful images. We will link to them. In fact, we will have many links that are relevant to this conversation on this week's show page at You had one other instrument, which sadly and kind of ironically was lost not too long after the arrival in Mars orbit. Can you tell us about MARIE and what you did get from it?

Jeffrey Plaut: Yes, MARIE was the Mars Radiation Environment Experiment, and it was a detector that had been flown previously on the International Space Station to measure the kinds of radiation-charged particles and neutral particles that could pose threats mainly to astronauts, also to computer equipment and other kinds of hardware on the spacecraft. This instrument was provided by the folks from Johnson Space Center in the Manned Space Program, and it gets back to what I mentioned earlier that there was also a lander that was intended to go at the same time as Mars Odyssey. That lander also had the same instrument, so we were going to watch the flecks of these potentially damaging particles both in orbit and at the surface simultaneously. We could see how those two different environments affected the flecks of these particles from the Sun and from the galaxy.

Jeffrey Plaut: We got some great measurements. Actually, shortly after launch, we turned the instrument on, and during the cruise to Mars, we collected a lot of great data. Once we got into orbit, also we had good success. Then, about two years on, we had a very large solar flare event, which I think you were alluding to...

Mat Kaplan: Yeah.

Jeffrey Plaut: ... damaged some of the circuitry in the radiation detector. So, a radiation storm, ironically enough, put an end to that instrument's observing campaign, but leading up to that, we got some great data, and it really is part of our understanding of the challenges that humans will face on their way to Mars and once they get there in orbit.

Mat Kaplan: Pretty amazing that, really, after now nearly 20 years in space, that may be the biggest loss that this spacecraft has suffered. Rich, turning to MRO, I suppose you know that we at The Planetary Society and everybody else who follows this mission and follows Mars around the world, we constantly make use of those gorgeous images from HiRISE, the High Resolution Imaging Science Experiment. Please, say whatever you would like about HiRISE, but we tend to perhaps put into the background that MRO carries a lot of other instruments that have done some terrific work.

Rich Zurek: Yes, but a big part of it was to observe Mars at resolutions that we hadn't achieved before with our previous spacecraft. HiRISE is the obvious example of that, where a single pixel projected down onto the surface of the planet is about a foot across.

Mat Kaplan: Wow.

Rich Zurek: But, we also have covered all of Mars, except for very small regions, with our Context Camera, which has a larger field of view but lower resolution, but still, at six meters per pixel, would have been the highest resolution except for HiRISE, and we use them in tandem. We do things like look for new impact craters, new things and changes on the surface, and we often first detect those just barely with our Context Camera because its larger field of view can cover more territory, and then we can zoom in on them with HiRISE to see what they're really like at that much higher resolution.

Rich Zurek: Now, in many ways, MRO is three different satellites. It's a weather satellite. We have a camera system that gives a daily global map of what the weather looks like on Mars. Sometimes we see regional dust storms. On occasion, in some years, but not every year, and for reasons we're still trying to understand, there can be giant dust storms that cover most of the planet.

Rich Zurek: Now, we also have an instrument in the thermal IR. It looks at the surface, but it's mainly looking at the atmosphere, and it's doing so at higher resolution again, and it's profiling things. How do they change with altitude in the Mars atmosphere and such? It routinely scans from 0 up to about 80 kilometers and does that repeatedly as it goes around the spacecraft, building up a temperature map of what's going on.

Rich Zurek: We're also a subsurface explorer. That is, we have a radar that is looking in the subsurface and in the interiors of ice caps, and profiling ice on Mars, I think, has been one of the big discoveries of most of the Mars missions currently operating at the planet. As Jeff pointed out, Odyssey pinned down where it was in that first meter or so. Our radars are probing deeper than that and telling us about the internal structure of the north polar ice cap, a mile-thick block of ice that we can see the interior layers and try to match them to the layers that we see exposed at the edge of the ice caps with our camera systems and such.

Rich Zurek: Finally, we also had an imaging spectrometer that was looking to understand where are the minerals that were formed in water on the surface of Mars—where are they today? where were they exposed? how were they exposed?—as a way of trying to understand what the ancient climate looked like on Mars. The geological record on Mars extends back to that very early period. In fact, it's almost unique in the Solar System in that regard.

Rich Zurek: So, our instruments are trying to exploit that planetary record to compare to the Earth's, and much of that Earth rock record from that period of time early in the planet's history is gone because the rocks get recycled by plate tectonics, and also, they've been degraded by the activity of lots of water for billions of years, whereas on Mars, the climate changed, and we're still trying to understand why. That's what some of our observations are about, to look at that ancient atmosphere—how did it evolve, how long were there wet periods that persisted, and what's the change on the planet today?—so that we can extrapolate that back into the past.

Mat Kaplan: That last instrument you mentioned, that's CRISM, which is one of my favorite space acronyms.

Rich Zurek: It is indeed, and it was dependent for its infrared observations in the near-infrared, which is where the surface minerals have their best signatures to say, "Is this a carbonate, is this a clay [inaudible 00:21:40] unit? What is this material, and how's it formed?" Those coolers worked for 10 years, well past their lifetimes and such. They're no longer working. That's kind of the one instrument failure we've had, and yet, we can't lament that because they went far longer than they were designed to. It still operates in the visible wavelengths because it doesn't need the coolers to get good signal to noise for that, so we're looking at minerals like hematite iron compounds and trying to understand what those look like. Even there, we're doing it at resolutions that haven't been achieved before. We can target areas as small as 20 meters across, and we can also look at, in a survey mode, areas at 100 meters per pixel.

Mat Kaplan: There are so many, I mean, thousands upon thousands, of images that HiRISE has returned, but just to pick out a couple of things that it has been able to do for us, our knowledge of Mars, what's the current thinking about those features that we've come to know as Recurring Slope Lineae, or RSLs, that sure look like something's running downhill?

Rich Zurek: They certainly do. There is something going downhill, and the argument is, is it enabled by some kind of activity of water, or is it, in fact, a dry avalanche? Think of sand moving down a steep slope, for instance. We were looking at this as a possible water-related feature because they seem to get darker during the warmest seasons and such and then fade away as we got into the colder seasons. Then, they would reappear again almost in the same places, but we did notice that there were changes from year to year, and we've been able to measure the slopes, the steepness of the slopes on which they occur, and those are consistent with dry flows. That is, they could be blowing sand, triggers and moves a fine layer of dust or changes or darkens it in some way that we're still trying to understand. So, it's not settled yet. There's still debate going on, but at the moment, we're leaning towards these are actually dry flows.

Mat Kaplan: My terrific conversation with Jeff and Rich about their very active Mars orbiters is far from over. I'll be back with them after this break.

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Mat Kaplan: Jeff. Everything that Rich has just talked about with these RSLs and so much of what we've already talked about in this conversation brings me back to that old mantra, follow the water. It's worked out pretty well, hasn't it?

Jeffrey Plaut: Yeah, I think so, and a motivation to follow the water is life requires water. If you find where the water is or has been, then perhaps you can find the evidence for life, and in some sense, our exploration program is making that transition from following the water because we seem to have found most of the water we were looking for, although there is a bit of a gap in our understanding, which maybe I could go into. We are now sort of, like I say, transitioning towards finding the evidence of life at these locations where we've seen that water is present or active, in particular, looking at two different signatures of past water, one being the land forms, for example, old river channels, or lake beds, or deposits laid down with water, such as deltas. Those become targets for landers and sample return.

Jeffrey Plaut: Then, the other signature, as Rich was alluding to, is changes in mineral composition, where minerals are altered in the presence of water. This, most commonly, are clay minerals or salt-type minerals like chlorides or sulfates. Again, the presence of those types of minerals give us targets for landers, and rovers, and the upcoming Mars 2020 Perseverance Rover, which is intended to collect samples for eventual return to Earth, is going to one of these sites that has all of these features indicative of the action of water. So, it's been a big success following the water. I will say, because I also come from the world of these radar explorations, that the radar on MRO and also on Mars Express, a European orbiter, have not directly detected liquid water except for one controversial instance in the south polar region, so there's still a lot of water that we might say is missing or we haven't put our finger on that's likely deep in the subsurface.

Mat Kaplan: We should mention that you are Co-PI, co-principal investigator for MARSIS, the Mars Advanced Radar for Subsurface and Ionosphere Sounding on the Mars Express orbiter from the European Space Agency. Before we finish, maybe we'll talk about that other radar system that you're hoping to send to Jupiter before too long. I'll bite, though. What's that knowledge gap that you referred to?

Jeffrey Plaut: There is a question that is encapsulated by, "Where did all that water go?"

Mat Kaplan: Yeah.

Jeffrey Plaut: There is clear evidence that large volumes of water flowed across the surface of Mars just in the amount of erosion that has taken place that I think there's a consensus that this erosion was caused by the action of flowing water. You can calculate just how much water is needed to do that work of eroding, these large flood channels, for example. It's much larger than the total amount of water that we have been able to measure, for example, in the polar caps with the radar systems or that we can calculate might be locked up in the ground ice or in mineral structures. There's still a huge amount, literally hundreds of meters of ocean depth if you spread it across the whole planet that is not immediately accessible to us. We don't quite know where it is.

Jeffrey Plaut: The MAVEN mission, which is not one of the orbiters on the agenda today, but another orbiter active around Mars, has led us to get a better handle on how much of that water may have been lost to space, probably in the form of hydrogen being stripped off by the solar wind. Even that probably doesn't account for a lot of this missing water, so again, my hunch, and I think a lot other Mars scientists would agree is that a lot of this water that once flowed across the surface perhaps was present as standing bodies of water has retreated into the subsurface fairly deeply, is either frozen or is deep in the warm interior where it's liquid groundwater.

Mat Kaplan: Well, I hope you're right about that. Rich, do you remember sitting with me and some of my Planetary Society colleagues when we were celebrating the arrival of MAVEN at Mars with a live show?

Rich Zurek: Yes, I do.

Mat Kaplan: What are your feelings about this, how successful we've been in following the water and figuring out where it's gone?

Rich Zurek: Well, I think we've learned a lot, and MAVEN was certainly a major contributor by being able to look at the various processes that are active today. By the way, part of that is, how does water get into the upper atmosphere where it's more likely to escape? We've seen that dust storms, for instance, by warming up the middle atmosphere, can let water get to higher altitudes, where it can be more easily photodissociated and stripped away from the planet. So, definitely, loss to space is a major part of the water budget over time, but the other part of it is ice and in the near surface that means we can see it in the polar caps, and we've also detected it in the subsurface and sometimes in multiple layers of the subsurface and such.

Rich Zurek: An interesting thing about Mars is, today, it seems to have been on the edge of having liquid water somewhere around the surface or in the subsurface but still frozen at the present time. The question is, how long has it been that way? Is it a couple a hundred million years? Is it a billion years? Is it two billion years? That's part of what we're trying to do by mapping out where the ice deposits are today and how they might have been emplaced over time.

Rich Zurek: There are different mechanisms for that. Ice ages on Mars is one possibility, where ice is emplaced at lower latitudes as the poles are exposed to more direct sunlight during their summer periods and such, and that's as the axis of Mars' rotation tilts over time in cycles of 100,000 to millions of years. So, we're still learning about this planet. Oftentimes, we look at something, and we say, "We know what that is," and then you realize the context is different. It's larger, or it's smaller, or it's at the edge of being what we suspect to be.

Rich Zurek: For instance, is this gully carved by water, or was it a block of CO2 ice that was streaming down the slope of a dune or something as it was melting during the annual changes today? It's those kinds of things where the Earth analog is both helpful in trying to interpret what we see and also sometimes misleading because this is a different environment. It'll be very interesting, once we get humans on the surface of the planet, to see what their perspectives of all of this is.

Mat Kaplan: Something else to look forward to. Here's a segue question. I found a release from NASA that was titled Treasure Map for Water Ice on Mars. Came out last December, actually, December of 2019, and it made it clear that it relied on... the creation of this map... on data from both of your spacecraft, MRO, and Odyssey, and other data. So, the question is... and I think you've addressed this already a little bit... how have these two orbiters and the teams behind them collaborated? How do you continue to collaborate? Jeff, you want to take that first?

Jeffrey Plaut: Yeah, yeah, it's an interesting point, and there's a couple of different ways to look at it. One is, in the strict sense, collaborating with scientists on both missions working together. We do have overlap. We have some scientists who are on teams on both missions. We communicate frequently with one another to coordinate observations whenever possible. Strangely enough, the two orbiters are in similar orbits, but they actually move in opposite directions to one another, so it's not always easy to get them lined up to make the same stripe across the surface at the same time, but we do our best.

Jeffrey Plaut: There are a number of complementarities or synergies in the instrumentation between the two spacecraft. That can really work to our advantage. MRO has the highest resolution cameras, whereas Odyssey has the thermal infrared imaging, which is not a capability of the MRO camera, so when you put the two kinds of data together over a particular site, you often get more than the sum of the two parts. Another thing we haven't really talked about but one of the functions of both MRO and Odyssey is to relay data from the ground assets, from the rovers and the landers, whatever happens to be on the surface of Mars.

Mat Kaplan: I was going to get to that because it is such an important function and one that there's some concern about, especially as these spacecraft age.

Jeffrey Plaut: Yeah, part of making all of that happen is all of these different projects' mission operations teams have to coordinate. We have to be ready to contact a lander. The lander has to be ready to contact the orbiter on a very tight time schedule, so there are weekly meetings to get all of these players to play together in a smooth fashion, and then we have new missions arriving. We have foreign partners that sometimes request support, so there's a lot of work that goes on behind the scenes to make sure all these pieces fit together, and the orbiters play a big role in that.

Mat Kaplan: Rich, anything to add?

Rich Zurek: It's a unique feature of Mars exploration for deep space and planetary science is this combination of the orbiters relaying data from the surface, also providing critical coverage of things like the entry, descent, and landing of the landers and rovers as they go to the surface. We're about to do that on February 18th of next year for the 2020 mission. Perseverance, as it goes down to the surface, will be covered by several orbiters and then, getting data back immediately after their landing, will be covered by other orbiters. So, there's a very big orchestration of activities here, as Jeff described, that help us gain more.

Rich Zurek: You get a lot more of your data back from your landed assets than if they were trying to do it by direct-to-Earth return because that takes more energy. By sending it up to the orbiters that are a couple of hundred miles away, as opposed to all the way back to Earth, is a great energy saving for them. The orbiters can do that. It's a small part of the total data return. MRO, for instance, has returned almost 400 terabits of information from Mars orbit. Just a small fraction of that is relay data, but it is a much bigger volume of data than would be returned by direct to Earth. So, we're enhancing the return in many different ways.

Rich Zurek: The concern, of course, is orbiters get old. They may not last forever. They won't last forever, but we've had good luck so far. Odyssey's been there almost 20 years. MRO's been operating, doing relay for more than a dozen, so it's definitely one of the key programmatic attributes of the Mars exploration.

Mat Kaplan: Another reason to hope that they'll continue to function for many more years. I want to ask you about how, over all of these years, your missions, maybe even the spacecraft themselves, the work you do, may have evolved. I was led to think about this, Rich, because of an announcement that I saw, made fairly recently, that MRO had discovered and imaged a group of tiny new craters on Mars, which may not sound like a big deal because it certainly has found lots of craters, some of them new, but the bigger news may be how this discovery was made. Do you know the ones I'm talking about?

Rich Zurek: I do indeed, and what this was is, over the years, as I said, our Context Camera has tried to look for changes on the surface, dark splotches that weren't there in earlier images and such. Then, we zero in on that with the HiRISE camera to verify that they are indeed impact craters. That's a tough job. You have to look through all of these images that are coming back. As I said, the Context Camera's got over 120,000 images that it's taken. Looking through all of those and trying to remember that that dark spot wasn't there in an earlier image is not an easy thing to do.

Rich Zurek: So, a group has tried to... and has succeeded in applying some artificial intelligence algorithms to... Let's train it. We know these were indeed craters. Let's train it to look for these kinds of things, and then we can run that algorithm through all of the images that have been taken and identify candidates. Then, we put those on the list for HiRISE to verify. That recent image was showing, the first of the image, the first of the confirmations of those candidate images that we had missed by our manual approach.

Rich Zurek: By the way, we're pretty good at capturing all of them manually, but to get really good statistics, and that's what we want because we use crater rates as a way of trying to understand time and the age of features on Mars, so even a small improvement in that is going to have great significance.

Mat Kaplan: Something we've also talked about many times on this show. Jeff, has Odyssey also changed or evolved its mission, how it does its work, over time?

Jeffrey Plaut: Yes, absolutely. A lot of the changes happen here on Earth, on the ground. It has to do with, among other things, dollars, and Rich will commiserate with me on this. As these missions age, they tend to face reductions in funding. In order to respond to that and continue having good science productivity, we are constantly searching for ways of streamlining our operations, trying to do as much or even more with less in terms of the number of people working, the number of hours that are spent on the different processes.

Jeffrey Plaut: Each of these extended mission teams become lean, mean machines to find all kinds of ways, and our job, both mine and Rich's as project scientists, is to protect the science parts of our budgets so that we can continue to be productive scientifically. I think we've mostly succeeded in those efforts to streamline the operations. We've done some other technical things, which allow us to get more data down, tricks with handling the downlink signal to increase our data rates and data volumes, as Rich mentioned, looking at ways to automate processes that can improve efficiency. So, both on the spacecraft, onboard the spacecraft, but maybe even more so on the ground, the missions evolve over time.

Rich Zurek: Obviously, one thing we have to deal with with these long-lived missions is the spacecraft does age. We're using redundant systems in some cases, but our missions are not using our star cameras, for instance, to give us attitude and knowledge and such instead of relying on our inertial measurement units, trying to figure out how to keep everything working and moving forward. There are techniques and such that we've continued to evolve and apply to keep these things operating almost at their original efficiencies and such. That's a challenge, but it's been successfully met so far, and we're hoping, for both of these orbiters, that they'll continue into the future here for many years.

Mat Kaplan: I hope that you both know how strongly all of us at The Planetary Society feel about how important it is that that funding for missions like this, all missions across the Solar System, as they continue to deliver great science, that this is a high priority for us, so we've got your back on that.

Rich Zurek: We appreciate the support.

Mat Kaplan: You're welcome. Rich, there is no denying that HiRISE has helped turn Mars into an object d'art if you will. There's even a special section of images on the MRO website that we'll, again, provide a link to, called Mars Is Art. I want to ask both of you about how important the simple beauty of this planet has been as you have spent so many years studying it professionally. Rich?

Rich Zurek: Well, even from orbit with HiRISE now, we're getting to what I call the human scale, and I think that's one of the reasons the landers, of course, have engaged the public as much as they have, that and the fact that everybody wants to drive a rover. However, I think that we're seeing this detail, and there's certainly beauty that goes along with it. The surface is complex. There's some startlingly beautiful things. Now, sometimes, we stretch the colors a bit because there's dust everywhere on Mars, and it tends to subdue those colors. When you do that, you can see some amazing diversity on the planet, and we use that scientifically, but occasionally, it also makes things works of art as well.

Rich Zurek: I recall that Alfred McEwen, the principal investigator for HiRISE, was at JPL for a meeting once, and looking for the meeting room, the secretary directed him down to turn left at the expressionist painting that was on the wall. When he went past, he realized it was a stretched HiRISE image. It just shows that there is this intricate color variation across the planet that reflect what we would see as a human scale if we were on the surface of the planet or flying low over it in an airplane or such. Many of the scenes are just incredibly striking.

Mat Kaplan: Stretch the colors. I don't even mind false color. They're all beauties to me. They're all masterpieces. Jeff, what are your feelings about the aesthetic side of the work that you do?

Jeffrey Plaut: Okay, we're getting kind of philosophical here, but-

Mat Kaplan: Yes.

Jeffrey Plaut: ... it's all right. As long as I've been in this business, I'm constantly reminded, and I remind myself, how fortunate we are in planetary science to be able to see these things, literally see with our own eyes and with the cameras that are extensions of our eyes, these incredible worlds that are, often at once, alien but quite familiar. What you'll often hear a planetary scientist say when they see a new image of something interesting or something that's maybe a little bit different than what they were expecting, they'll say words like, "Wow," and "Cool," and "Amazing." You're constantly thrilled. Your listeners, a lot of the listeners who support The Planetary Society or just enthusiasts for exploration of space understand what I'm taking about. It's important, I think, that people know that the scientists feel the same way. The scientists, okay, maybe they have an informed context to instantly interpret what they're seeing, but usually the first reaction is, "Wow, that's cool."

Mat Kaplan: I'm going to keep you in that philosophical mode for one more question if you don't mind. Your spacecraft have seen the loss of neighbors like Mars Global Surveyor and the Mars Exploration Rovers, the Phoenix Lander, and the arrival of new colleagues, MAVEN, MOM, the ExoMars Trace Gas Orbiter, Curiosity and InSight down on the ground. They'll soon be joined by a new generation of Martians, Perseverance, TianWen-1, Hope. What comes to mind as you look back through now more than 50 years since that first brief visit by Mariner 4? Rich?

Rich Zurek: It's incredible, the gains that we've made, and yet, there are many outstanding science questions that we still don't understand. What sets the frequency of these dust storms that spread a haze across the planet in some years but not others, and this climate change that has occurred, as Jeff put it, where did all that water go, and why, and the processes for it? I think with Mars, and because Mars could someday be a destination for human explorers working on its surface, that Mars is going to a level that, in ways, more like Earth science, where we know some basics, but we're still trying to understand the processes by which things occur. By learning that, we learn something about the Earth as well and its place in the universe.

Rich Zurek: One of my favorite images is a picture that HiRISE took from Mars orbit of the Earth and Moon system. We're always comparing back to, "Okay, what are we learning here? What's different? Might we fill in some of the gaps of our understand of our own planet in doing that?"

Mat Kaplan: Jeff?

Jeffrey Plaut: You referenced 50 years, which takes us back to the '70s when we had our first visitors to Mars. That culminated with the Viking program, which consisted of two landers and two orbiters and was incredibly successful, but once those missions ended, there was a long gap. I think Mars Pathfinder was then the next NASA mission to Mars after a few decades of inactivity. Pathfinder kicked off what I refer to as the new golden age of Mars exploration, and we've been doing this continuously since then. What we were talking about earlier, how these different pieces fit together scientifically and logistically, is just what has made this program so successful.

Jeffrey Plaut: Again, it's how lucky we are to be alive right now during this golden era of Mars exploration. At least this year, we're not slowing down. Like you say, we've got more visitors arriving, not only from the U.S. but from international efforts, both European and from individual countries now, and more to come, so let's keep this momentum going. I think it's really taking us to some great places in Mars exploration, ultimately with humans making their visits.

Mat Kaplan: Rich, as the chief scientist for the Mars program out of JPL, where so much of what we've learned about the Red Planet has made its way back to Earth, all of this knowledge, very exciting times ahead, right?

Rich Zurek: Yes, indeed. The next big step is Mars Sample Return, and that's going to go from places that our orbiters have said, "This is an interesting place." There was a crater filled with a lake. A delta formed in there. Might that preserve biosignatures from that early time when there was a more Earth-like environment? Why did that change, and how did it change? To understand that part, we need other kinds of investigations, too. We need to finish our mapping of where ice is across the planet. We need to understand more the processes from day to day, the agents of change, which include not only the action of water but of what is on Mars, the other volatile, the carbon dioxide going from solid to gas and back again.

Rich Zurek: So, there is plenty to do. That's not the problem. The problem is to find a program that can support this broad range of exploration, and I'm hopeful that it will because this is a place that went through many of the same stages that the Earth went through early in its history, and it's preserved some of the evidence of that transition. We need to learn how to translate that and learn about it, but to do it, we have to observe, and we have to go there, and we have to see more of what's there. So, I'm very hopeful about that.

Mat Kaplan: Gentlemen, please pass along to your teams the very highest regards from all of us at The Planetary Society and, I am willing to say, all of the listeners to this show for continued success, continued great science from these missions, the Mars Reconnaissance Orbiter and Mars Odyssey. Jeff, we won't do it today, but maybe another time, perhaps as we see the JUICE mission from the European Space Agency begin its journey toward Jupiter in 2022. Maybe you can come back and tell us about RIME, the Radar for Icy Moon Exploration Instrument that you are a Co-PI for on that spacecraft, but again, best of continued success to both of you, and we look forward to hearing more great science coming from these two missions we've been talking about over the last nearly an hour.

Rich Zurek: Thank you, Mat. We appreciate the support of groups like The Planetary Society and such. After all, these missions are for everybody, and the knowledge gained is for everyone as well, and we hope to continue going on.

Mat Kaplan: Well said. Thank you both.

Sarah Al-Ahmed: What a year it's been for space exploration. Hi, I'm Sara, digital community manager for The Planetary Society. Will you help us celebrate 2020's greatest accomplishments? You can cast your votes for the most stunning image, the most exciting mission, the most surprising discovery, and more at We've also got special year-end content on our social media channels. Voting is open now at

Mat Kaplan: Guess what? It's time for What's Up on Planetary Radio. Here is the chief scientist of The Planetary Society. That's Bruce Betts, who is in charge of so many things around the office and around the world.

Bruce Betts: Yes, indeed, but I can't discuss all of them.

Mat Kaplan: No, of course not. You'd have to kill all of us.

Bruce Betts: God, that would be such a drag. I like most of you.

Mat Kaplan: Really, that would look so funny on your expense account.

Bruce Betts: Oh, God. This took a quick dark turn.

Mat Kaplan: It's good, though, that it's dark because that'll make it easier to, you know... Oh, I got to [crosstalk 00:53:33].

Bruce Betts: Good one, yes, if it's dark where you are, literally not figuratively, hopefully, you can see planets in the evening sky. We got Jupiter and Saturn looking all bright, particularly Jupiter over in the west in the early evening, Mars high in the south in the early evening looking bright and reddish. To skip out of planet land, check out Orion coming up in the early evening looking quite gorgeous as it does, heralding winter in the Northern Hemisphere, southern in the... Southern in the Summer Hemisphere? Yeah, that was backwards. I'm just [inaudible 00:54:10] of attention. At least that those are coming, that's what I think of when I see Orion. In the predawn, we've still got Venus dominating the predawn east in the bad times before dawn.

Mat Kaplan: The Orions are coming. The Orions are coming.

Bruce Betts: Oh, goodness. Let me become more coherent as I discuss this week in space history. 1969, second set of humans to ever step onto the moon did so with Apollo 12, and in 1998, the Zarya Module was launched, the first module piece of the International Space Station.

Mat Kaplan: Yeah, I forgot about that, and here we just... Well, I saw, as we speak, last night, two Russian cosmonauts and an American welcoming four more people, and I'm sure they'll be hanging out in Zarya now and then.

Bruce Betts: Yeah. We move on to Random Space Facts.

Mat Kaplan: I shouldn't even add reverb to that. You did such a good job of simulating it.

Bruce Betts: Oh, thank you. I've been trying for so long. So, as of now... I think you may have discussed Mars Odyssey just a wee bit.

Mat Kaplan: Yeah.

Bruce Betts: As of now, Mars Odyssey has completed more than 80,000 orbits of Mars.

Mat Kaplan: Ooh. that did not come up.

Bruce Betts: Well, I did my own little calculation, so we'll hope it's right. That's a lot of orbits of Mars.

Mat Kaplan: That's a lot of orbits period. I don't care what you're orbiting.

Bruce Betts: All right. Let us move onto the trivia contest. I asked how many of the largest dwarf planet, Pluto, would fit inside the smallest planet in our Solar System, Mercury, assuming that you could smoosh it and shove it in there. How'd we do?

Mat Kaplan: Don't try this at home. There was some disagreement here. We got a... I don't know... plurality, I guess with the answer I think you were looking for because you told me you actually did some calculations of your own, but there were other folks like our poet laureate, [Dave Fairchild 00:56:22], who, as far we can tell, are a little off here. "Mercury, the smallest planet, sits right near the Sun. Frozen Pluto sails wide, a trans-Neptunian. If you stuff the coldest in the warmest until it fit, you could pack nine Plutos and a half inside of it."

Bruce Betts: Well, it's a beautiful poem.

Mat Kaplan: Yeah.

Bruce Betts: I am not quite sure where these nine and a halves came from unless they're using old Pluto diameters. Maybe I'll investigate and figure it out, but calculations based on what I did always gave 8.6, 8.7-ish Plutos that you could shove into Mercury.

Mat Kaplan: That's going to make [Bob Clane 00:57:06] very happy. We have a poet laureate. Maybe he's the pun master. He doesn't have one for us this time, but he does have that answer, 8.7 Plutos would fit inside Mercury if you do a volume comparison. He then went on to add 65.26 Charons would fit inside Mercury, but no Titans would fit in Mercury. I'm having trouble getting those words out. So, Bob in Arizona, you have won yourself a Planetary Society Kick Asteroid! rubber asteroid. I wonder how many of those would fit inside Mercury.

Bruce Betts: Oh, my gosh. I didn't do that calculation [inaudible 00:57:45]. Sorry.

Mat Kaplan: [crosstalk 00:57:47].

Bruce Betts: They do smoosh, though. Do you get to squish them?

Mat Kaplan: Yes. I suppose you can pack them right in. [Devon O'Rourke 00:57:55] in Colorado, "Since Mercury is not hollow, zero. Oh, just kidding. I know what you meant. Since atoms are mostly empty space, the answer is obviously infinity." Somewhere between the two, Devon. [Nathan Molene 00:58:09] in South Carolina. He did have the answer for the planet Mercury, but he also had this, "About 9.8 times 10 to the 20th Freddie Mercurys to one planet Mercury."

Bruce Betts: Oh, wow.

Mat Kaplan: Yeah. I don't think it'd be right to squish them, though.

Bruce Betts: Oh.

Mat Kaplan: Finally-

Bruce Betts: Oh.

Mat Kaplan: ... from our other poet... I know. I'm sorry. Too soon?

Bruce Betts: Yeah.

Mat Kaplan: [Gene Lewin 00:58:33] in Washington, "How many licks to the center of a Tootsie Pop? The wise old owl said three. What would you do for a Klondike bar? Who knows what that would be? So, this question, based on volume that was posed by Dr. B. takes 9.5 croutons, each Pluto-sized to stuff a turkey with the volume of Mercury," and he then adds, "I prefer cornbread stuffing." Okay, wrong answer, but cute rhymes.

Bruce Betts: I am so hungry now, too.

Mat Kaplan: I know. I can't wait.

Bruce Betts: Sounds delicious.

Mat Kaplan: That's where we are for the one that we are done with. What have you got for next time?

Bruce Betts: All right. Well, as you may have just heard, Mars Odyssey is the longest continuously active orbiter around another world. What spacecraft is the second-longest continuously active orbiter around another world? Go to

Mat Kaplan: I don't think I gave this away. I don't think any of us did. Huh. You have until the 25th... That would be Wednesday, November 25th at 8:00 AM Pacific Time... to get us the answer for this one, and we have something pretty cool for you because I was contacted, he was referred to me by our old colleague, Emily Lakdawalla, Urs Ganse, who is a researcher at the University of Helsinki, in Finland, of course, the Finnish Center of Excellence in the Research of Sustainable Space. He has put together a book called The Spacefarer's Handbook: Science and Life Beyond Earth. I've been through it. It's really very, very good. It's very interesting. It's published by Springer, and a copy can be yours. He'll send you either the real thing or an ebook version. That will go to whoever's picked by this coming time, or a couple weeks from now, who has the correct answer. Thank you, and get those entries in. We're done.

Bruce Betts: All right, everybody. Go out there, look up at the night sky, and think about pencil erasers of all different types. Thank you. Good night.

Mat Kaplan: There's so much I could say about pencil erasers. I really treasured... I treasured my Pink Pearl, but I also went through lots of those ones you detach to the top of the pencil because the one with the built-in erasers, come on.

Bruce Betts: Yeah, they're lame.

Mat Kaplan: Yeah. What's up with that? This is What's Up?

Bruce Betts: You said it.

Mat Kaplan: With the chief scientist of The Planetary Society, Bruce Betts, who joins us every week here for, yeah. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by its members who would love to take a spin above Mars, well, many of them anyway. Join the fun at Mark Hilverda is our associate producer. Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Ad astra.