Planetary Radio • Nov 21, 2018

We Know Where the 2020 Rover Will Look for Martian Life

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Briony Horgan

Assistant Professor for Earth, Atmospheric and Planetary Sciences, Purdue University

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

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

NASA announced on November 19th that the multi-billion dollar 2020 Mars rover will land in Jezero crater, where it will begin the search for the signature of past life. The selection process took five years, and Briony Horgan of Purdue University was part of it all. She joins us to talk about this exciting and enticing target on the Red Planet. Planetary Society Senior Editor Emily Lakdawalla prepares us for the much more imminent Mars landing of InSight. Orion in the northern hemisphere’s night sky can only mean winter is coming. Just ahead of it is a new What’s Up segment from Bruce and Mat.

Jezero crater regional topography
Jezero crater regional topography Isidis basin, about 1500 kilometers in diameter, was the last of Mars' large impact basins to form. The landing site of Mars 2020 will be in Jezero crater, on the northwest edge of the basin. Nili Fossae is a region of fractured terrain. Geologists think that the fractures in Nili Fossae formed as a result of the Isidis impact. Syrtis Major, to the southwest, is a volcanic region. This map shows topography derived from the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA).Image: NASA / MIT / Goudge et al 2017
Location of Jezero Crater Mars 2020 landing site, Mars
Location of Jezero Crater Mars 2020 landing site, Mars Jezero crater lies within the yellow circle near the center of this image (the crater itself is not visible in this global view, which was taken by Mars Orbiter Mission on 7 October 2014). InSight and Curiosity landing sites are near the edge of the disk on the right; no other successful landing sites are visible in this view.Image: ISRO / ISSDC / Emily Lakdawalla
Jezero Crater, Mars
Jezero Crater, Mars This 10 m/pixel resolution mosaic of Jezero Crater was created from images taken by the Mars Reconnaissance Orbiter Context Camera (CTX). (Click on the image for a full-resolution view.)Image: NASA / JPL-Caltech / MSSS / Tanya Harrison

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[00:00:00] Rover targets life on Mars 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 now know where the 2020 Rover will land on the red planet. NASA made the announcement on Monday, November 19th, exactly one week before another spacecraft descends to Mars. Planetary scientist Briony Horgan will tell us about the promise of Jezero crater and how it was chosen.

First though, we'll check in with senior editor Emily Lakdawalla for a look at what to expect when the InSight Lander begins its seven minutes of terror on November. 26th

A dog puts the first paw prints on Mars? That's a hint about one of the prizes Bruce and I have for the winner of a new space trivia contest coming in this week's What's Up segment.

Emily, it looks like we are just [00:01:00] days away from another white-knuckle landing on the red planet.

[Emily]: We are. It's going to be exciting as it always is as we approach, in this case, a six minutes and forty-five seconds of terror as InSight gets ready to land on the surface of Mars on November 26.

[Mat]: I have in front of me your blog entry at for November 12 and you have all of this in detail, and you include this neat little graphic that you created that traces what we can expect.

[Emily]: It's always a challenge to put together all the the bits and pieces of information that come out from different sources and so I love to just assemble these infographics that have every last detail on it and then share them out into the world for the benefit of everybody else who has the same problem I did.

[Mat]: Our friend Rob Manning, the man who knows more about putting things down softly on the surface of Mars than I think any other human, has this great video which you have a link to from the blog post.

But even the audio is so good, I mean the video is [00:02:00] great as well because it's like a combination of a wipe-off transparent wipe-off board and CGI, which is really fun, but the audio is so great that I think we'll just use it right now.

[Rob (from audio clip)]: Although we've done it before, landing on Mars is hard and this mission is no different. The process to get from the top of the atmosphere of Mars to the surface we call Entry Descent and Landing, or EDL. It takes thousands of steps to go from the top of the atmosphere to the surface and each one of them has to work perfectly to be a successful mission. The process starts well above the top of the atmosphere of Mars. The cruise stage faces the sun. It also has its radio antenna which faces Earth, but now we don't need the cruise stage- it’s job is done- the next step, just seven minutes before arriving to the top of the Mars atmosphere, is to separate the cruise [00:03:00] stage.

Before you hit the top the atmosphere though, the space capsule has to orient itself so that the heat shield is precisely facing the atmosphere. Now, the fun begins. The vehicle is moving at nearly 13,000 miles an hour, but it's hitting the top of the atmosphere at a very shallow angle: 12 degrees. Any steeper, the vehicle will hit the thicker part of the atmosphere and will melt and burn up; any shallower, the vehicle will bounce off the atmosphere of Mars. At the very top, the atmosphere gets about 70 miles above the surface of Mars and the air is starting to get thicker and thicker and thicker. As it does that, the temperature of the heat shield gets well over a thousand degrees centigrade, enough to melt steel. Over the next two minutes, the vehicle decelerates, a back-breaking 12 Earth G's, from 13,000 miles an hour to about 1,000 miles an hour.

At about 10 miles above the surface of Mars, a supersonic parachute is launched [00:04:00] out of the back of the vehicle; 15 seconds after the parachute inflates, it's time to get rid of the heat shield. Six pyrotechnic devices fire simultaneously, allowing the heat shield to fall and tumble away from the vehicle, exposing the Lander to the surface of Mars. Ten seconds after the heat shield is dropped, three pyrotechnically deployed legs are released and locked for landing; about a minute later the landing radar is turned on, sending pulses toward the surface of Mars as the vehicle starts to try to measure how high it is above the surface and how fast it's going out. About a mile above the surface of Mars, the Lander falls away from the backshell and lights its engines and very quickly the vehicle must rotate out of the way so that the parachute and the backshell don’t come down to hit it.

The last thing that has to happen is that on the moment of contact the engines have to shut down immediately. If they don't [00:05:00], the vehicle will tip over. So if all the steps of Entry Descent and Landing happen perfectly and we are safely on the surface of Mars, we'll be ready to do some exciting new science.

[Mat]: So that's Rob Manning of the Jet Propulsion Lab on what we can expect it. If all this goes according to plan, Emily, when are we going to get back those images? I want my pictures.

[Emily]: But we actually don't know the answer to that question, as usual. The spacecraft will take some photos with its cameras right after landing.

The main one that will show us foot pads on the ground, that camera will still have a dust cover on right after landing. We can the hope that we'll get those pictures back right after touchdown, which does frequently happen, but we can't be sure that there will be enough bandwidth that the spacecraft actually transmitted at the time that it lands, so we might have to wait a couple hours. We might even have to wait several hours, but I really don't expect [00:06:00] that. I hope to see images pretty quickly.

[Mat]: Now these are going to have to be relayed back to earth right?

[Emily]: Yes. That's how it works. InSight has a pretty small radio antenna.

It uses that antenna to communicate with orbiters or in the case of InSights landing, it's actually going to be relaying data through two CubeSats that are flying past Mars as an experiment to try to test this kind of communications for the future. So it's possible that we'll get this data, the telemetry and the first images, through these tiny suitcase-like spacecrafts named Marco, which would be really cool if it happens.

[Mat]: Very cool and really good for the show that we're going to put on at Caltech as this happens. If you want to learn more, has a link to the Eventbrite page. You do need an RSVP but it is free and we will be following along the NASA TV coverage there with some great people on stage. As if I didn't know, where will you be?

[Emily]: I'll be at JPL with all the press, you know, holding our [00:07:00] breath hoping that everything went well and then being excited and writing everything down as soon as things do go well. You know I do feel like we take for granted now the fact that Mars landings have seemed to go off without a hitch for a long time, and I have to keep reminding myself that things may not go well. But we'll know for sure one way or another on November 26.

[Mat]:We will all be holding our breath along with you and all those other folks at JPL and around the world. Thanks Emily.

[Emily]: Thank you Matt.

[Mat]: That's our senior editor, the Planetary Evangelist and the editor-in-chief of the Planetary Report, the magazine from the Planetary Society that goes to our members but you can read it online for free. We'll check in with her again before long: very possibly to talk about the success we all hope for the InSight Lander.

We're going to call it Jezero, but if you read Emily Lakdawalla’s [00:08:00] November 20th blog post at, you'll learn that our pronunciation of that Martian crater’s name is open to debate. And you should read Emily's post for a great guide to the just announced target for the 2020 Rover, enhanced by lots of images and graphics, but I also learned a lot in my conversation with Briony Horgan

Briony is an assistant professor in the department of Earth Atmospheric and Planetary Sciences at Purdue University, but this planetary scientist was also a major player in the long and winding process that ended on November 19th with the selection of Jezero. She joined me from her office not long after the announcement was made.

Briony thank you very much for joining us on Planetary Radio on very short notice and congratulations to you and the rest of this team that has delivered this really momentous decision about where the next Rover will be going on Mars.

[Briony]: Thank you. Yeah, we're very excited [00:09:00] that we have a landing site for Mars 2020. We're absolutely thrilled.

[Mat]: And we're going to talk about that site, but I'm hoping we can spend a couple of minutes upfront talking about that process that led to its selection. You are a good person to talk to about this because you and Sanjeev Gupta, I can't say you wrote the book but you wrote the PowerPoint presentation that I’ve been pouring over and that my colleague Emily Lakdawalla refers to many times in her brand new blog post about the selection of this site (and we’ll link to it by the way from the episode page that people can find at, but of course it wasn't the only site under consideration, was it?

[Briony]: No, it wasn't. So we actually had four final sites going into this last round of consideration for Mars 2020. They included Gusev crater, which was previously visited by the Spirit Rover, and the motivation for that site was ancient hydrothermal springs that were investigated by Spirit and could potentially contain [00:10:00] microbes and silica. We had two sites that were actually pretty nearby Jezero, Northeast Syrtis and Midway, both of which were these really ancient sites on Mars that were ancient crustal materials that could tell us a lot about the early history of Mars and very early environments in the surface and subsurface. And then finally Jezero, which is sort of in that same area, but it's this ancient Crater Lake that we think could really be a great place to investigate not just the habitability of ancient Mars but also look for signs of life in this ancient lake environment.

[Mat]: Now I know some of the scientists who were pulling for one or the other of these sites that was not selected and yet they all seem to be satisfied- well the ones I've spoken to- that this is certainly Jezero that’s a really promising place to go.

[Briony]: It is, you know, and one of the reasons it's been a popular site throughout this five-year long landing site selection process is because it just has a lot going for it. We think it's old and we think it dates from the period in Martian history when [00:11:00] the most water was present at the surface, and we see evidence for all of the valley networks and lakes, at least the majority of them forming. And so going to be able to go to a time in Mars's past when life was,we think, probably the most likely to be present, is a huge, huge advantage for this site. But it's not just that it, you know, was a lake at this time, it also has volcanic deposits. It has minerals that precipitated out of that lake, it has beautiful deltaic features that we can investigate to understand the history of those lake processes, and it's smack in the middle of this really ancient crust on Mars that we think of as sort of a window into the early evolution of not just Mars, but other planets in the solar system as well.

[Mat]: Whatever else it may prove to be once we get there, this site certainly doesn't look from above like it will be boring. It really is very diverse. What is particularly interesting, well to me anyway, is that this area certainly looks like a river delta.

[Briony]: It does, yeah, so that's one of the really great things about this site is that we have this clear [00:12:00] evidence for this well-developed system of river valleys that feeds into this lake. When the rivers hit the lake, they dropped their sediment out and formed this delta that built out into the lake, and then eventually we actually also see evidence that this lake breached, that it breached the other side of the crater rim to form an outflow channel on the other side.

So that tells us not only was there water in this crater, but that it was there, it was deep enough, and it was there for long enough to actually flow out the other side. And so we think there's a really great case that there was a long-lived watery environment here for life to live in.

[Mat]: We've talked about the 2020 Rover and even about the site selection process several times in the past. What were the major factors that were being taken into account as all four of these sites were being considered?

[Briony]: So there are a couple of big things. So we had a few big goals or big objectives we had to evaluate when we were looking at these sites on the science team and we spent the last two or three years on the science team looking at these sites ourselves,you know, actually going back and looking at the original data, trying to make sure we agreed with all the interpretations that other scientists put out [00:13:00] there, and really trying to do as good of a job as we could internally as well evaluating these sites. So we spent a lot of time looking at all four of these sites.

So the big things we were trying to understand was first off, you know, does this site contain a geologically compelling story, right? Can we go to this site and understand the geological story? The second one was can we conduct a good astrobiology mission, can we try to understand an ancient habitable environment and then can we also look for biosignatures?

And those are two, you know, they seem similar but they're sort of different investigations, right? And of course the third one is are there opportunities for this site to collect samples for future sample return, which is a very important consequence of the Mars 2020 Mission and it's one that we’re holding at the back of our minds at all times.

So we're looking at these sites trying to understand, okay, how much do we really know about the geology? How much will the Rover be able to add to our understanding of the geology at that site, and then based on that, how well do we think we'll be able to conclusively identify [00:14:00] or even search for biosignatures at these sites?

So they all kind of interplay together, and the different sites have different strengths and weaknesses in all of those categories.

[Mat]: You're a planetary scientist, I believe primarily a geologist, if you will speak from the biology side for a moment, what tells us that this is a good place to look for biosignatures, probably of past life, but we won't know until we go there?

[Briony]: Right, exactly, so really it's the evidence for long-lived watery environment. So the presence of the delta tells us that there was a lake here for long periods of time. What's also really interesting about this site though is that it's not just the delta, we also see evidence for minerals that precipitated out of the lake, potentially. We think we see evidence for that from orbit, and basically when that happens you can actually trap anything that's living in the lake in those minerals in particular. We see evidence for minerals called carbonates, which is similar to, you know, things like limestone that you might find on Earth, which are great at trapping microbial fossils, organic matter, all kinds of stuff [00:15:00] like that. So it's the combination of minerals precipitating out of the lake along with the delta itself and bringing in all kinds of materials, sediments, and organics and biosignatures from the surrounding terrains and depositing them in the lake and then trapping them in the sediments as laying down.

So it's really all about trapping and preserving all those signs of life, everything from organics to minerals to microbial fossils and things like that, that's really that ability to trap those biosignatures that we’re looking at in this lake.

[Mat]: When this Rover, the 2020 Rover has yet to be given a cuter name, rolls up to one of these sites that appears to be a good place to look for biosignatures what will it have on-board that will enable us to look for the remnants of possible life?

[Briony]: So the really great thing we have with this Rover that we haven't had in the past is the ability to do very high-resolution imaging of these rocks, and not just imaging, we have the ability to look at these rocks at the [00:16:00] microscopic scale and do things like look for, okay, where are the organics, and map them out with instruments like the SHERLOC instrument, which is a spectrometer that can actually make maps of the minerals and organics and other species that are in the rocks at a very very small scale. We can also make maps of the chemistry of the rocks at a very similar scales and we also actually have remote sensing instruments to detect organics and other minerals from standoff distance. So we have this whole strategy for the mission where we'll come up to a site, say for example, the side of this ancient delta, we’ll do a survey of this site using remote sensing instruments, and then we'll identify places we want to look at in much more detail with our microscopic and sort of high-resolution contact.

Once we do that, once we kind of know what's going on, then we can decide whether or not we want to take a sample at this site to bring back to Earth eventually to do a much more detailed search for biosignatures in these rocks.

[Mat]: That remote sensing that you mention, is that this more advanced descendant of ChemCam that's on Curiosity?

[Briony]: Yes [00:17:00] that's the SuperCam instrument and it's called Super because it can do so many things at once. It has the same abilities that ChemCam did where a basically uses a laser to create a plasma in the rocks and then can look at the elemental chemistry of the rocks based on a light that's emitted by that plasma.

It can also though do standoff Raman spectroscopy, so similar to our microscopic SHERLOC instrument but at a standoff distance so we can get a sense of what's in the rock before we go look at it up close. And then it also actually can do a different kind of spectroscopy, sort of in the long sort of red wavelengths, near-infrared wavelengths, at which will help us identify the minerals that are in the rocks. And so it can kind of do all this stuff all at once and so we're pretty excited to apply that once we get on the ground.

[Mat]: Pretty cool instrument. Is this Rover going to have- it sounds like it may have- just a more powerful microscope than Curiosity has?

[Briony]: Yes on Curiosity the only high resolution imaging issue we have is Molly, which is the Mars hand-lens imager, which is really just a camera but a very, very good one that can get very high-resolution imagery.

So on Mars 2020, [00:18:00] what we're going to have instead is not just that we'll be able to map out all of the minerals and organics and all the things at that same kind of scale, but it will help us identify, you know, could those organics be a biosignature or are they just organics that are present all over Mars?

[Mat]: Speaking of cameras, up on top, up on the mast, is of course going to be Mastcam-Z that we've talked about on this show in the past, and your co-investigator for that amazing stereo-vision system, I believe going to be the most advanced camera ever to go to the surface of Mars. How will it play a part in in searching for this this evidence of at least past life?

[Briony]: Well Mastcam-Z is literally the eyes of the Rover and we're really excited to use the eyes to identify where we're going to do our deep sampling of these rocks.

The Mastcam-Z is not just a camera. It is actually a pair of cameras that have the ability to zoom in and out and get really beautiful high resolution images of the surface and stereo as well. Because we have two cameras, we can make 3D maps of the surface, but the really great thing about Mastcam-Z is that in addition to all of that, in [00:19:00] addition to the beautiful images and the stereo Imaging we’ll be able to do, we can also actually also do mineral mapping with this camera because we have the ability to do spectroscopy with the camera.

We use filters to put in front of the camera to take a picture at very specific wavelengths, then we can look for absorption of light at those wavelengths for two different kinds of minerals. This is the kind of work we're already doing with the Mastcam-Z on the Curiosity Rover, but we've actually been working really hard to update that technique so that Mastcam-Z will be able to detect more minerals at higher resolution, and we’re really excited to help use that data to identify where we should be looking for biosignatures.

[Mat]: I'm looking at that presentation that you co-created. There are several slides in here that go into that sample collection, which is one of the main jobs of this Rover; you actually have graphics on some of these slides that show some of what look like the cores that may be brought up out of the ground and stored away for safekeeping.

[Briony]: Right. Yeah, so, you know the Mars 2020 [00:20:00] Rover, the goal of the Rover itself when it's doing its in-site mission on the ground is to do astrobiology, right, to look for biosignatures. It's all we've been building up to for decades now with the Mars exploration program, but really to do that well, to look for better concise evidence of biosignatures,we need to bring those samples back to Earth and look at them using-throw basically, throw everything we can at them, everything but the kitchen sink, right, to try to see if we can see definitive signs of life in these samples. And that's one of the big goals of Mars 2020 then is to collect this suite of samples that we can do astrobiology with back here on Earth.

But of course in addition to astrobiology Mars sample return is an incredible opportunity to do really great geology as well. So we're not just bringing back samples that are good astrobiology, we also want to bring back things like lava flows that could tell us about the volcanic history of Mars, the initial formation of the planet, we want to bring back samples of minerals to tell us about the history of the atmosphere and why Mars has lost so much of its atmosphere, for example, [00:21:00] things that could tell us about the history of water on the planet.

There's a whole suite of things we would love to bring back. Unfortunately, we only get to bring back- it's very small number of samples- probably something like 20 samples. And so one of the jobs of the Rover, in addition to looking for biosignatures, is going to be selecting that suite of rocks, you know, the sort of pencil-sized core samples that we will hopefully be able to bring back with the future mission. And that's going to be challenging, right? Because this is, okay, we're going to one site, we have this one opportunity to collect rocks that might come back from Earth to Mars. What rocks do you choose? Right, what small sampling of the huge diversity of rocks we've seen on Mars already would you bring back to study in labs on Earth? And that's the really challenging question, it’s going to be one of the big questions will have to address with the mission. We already have some idea right, so we've already presented a possible suite of samples we could bring back from Jezero crater and we’re really excited. It ranges from everything from these mineral precipitates that we think could have formed in the lake to the delta sediments to the volcanic materials [00:22:00] that are in the crater, as well as many other types of samples. And one of the really compelling reasons that we chose Jezero crater, that we supported Jezero crater, is because of the diverse samples we could possibly get back.

[Mat]: Sounds like you'd like to get your hands on a gram or two of those samples when they make it back here.

[Briony]: I would love to hold some of a piece of Mars in my hand. That would be great.

[Mat]:I know that, you know, you have a lot to weigh in making this choice, each site had its pros and cons. What are some of the downsides of Jezero?

[Briony]: Yeah, so Jezero has a few challenges. One thing, on the surface, you know we actually have really beautiful images of Jezero, it’s pretty dust-free, we can see all the beautiful textures and colors in the rocks, but that's because it's a pretty windy place and there's a lot of sand moving around and blasting all that dust away. So there's a lot of sand ripples and dunes that are on the surface. The engineers don’t think it will be a problem, there plenty of risk-free pads that we can use to get around to the major places in the crater.

One of the [00:23:00] concerns about Jezero is that, you know, it doesn't have some of the things that the other possible landing sites have. You know, for example at the Gusev crater, the Columbia Hills landing site where Spirit investigated, Spirit identified silica bearing little finger-y rocks associated with an ancient hydrothermal springs that could be actually, in and of themselves, based on the Spirit data, potential biosignatures. Scientists have observed these silica digitate forms that we've seen at Gusev on Earth and associated them with microbial activity and actually trapping microbial sort of remnants in them as well.

So that was the really strong argument for Gusev is that we know what we're getting into. We know the biosignatures, potential biosignatures were there. It's a very simple mission to go get them. So at the other sites, we don't have that, right, all we have is orbital data. We don't have the on the ground, you know ground truth that there are indeed great rocks there for us to sample for biosignatures. But at the same time Gusev crater was a place we've been before, we've done a lot of the basic geology, we've learned a lot [00:24:00] about Mars from it.

What is a little unclear is how much more you can learn about Mars by going back with a better Rover. Is it enough to justify, you know, several billion dollars not just for Mars 2020, but for future missions well. So thinking more about the other sites that were around Jezero, Northeast Syrtis and Midway, so these sites were the sort of, again this ancient crustal environment on Mars. The argument for those sites is ,one, that they would tell us a lot geologically about the history of Mars, about how Mars formed, about the really early formation of the crust and hydrothermal processes and all kinds of exciting things like that.

But there's also a natural biological argument for those sites and that these sites might preserve, basically hosted subsurface environments that hosted things like hydrothermal systems or aquifers or other environments that could have supported a very different kind of life from the kind of life were looking for in a surface lake, right?

So somewhere like Jezero, really looking for things like microbial mats or microbes living in the water [00:25:00] column that deposited organics, that's a very different environment in a very different kind of ecosystem from something like a subsurface environment, which we know exist on Earth. There are enormous, huge amounts of microbes that live underground on Mars- excuse me, on Earth- and we know they're there-

[Mat]: Wishful thinking!

[Briony]: Well, so one idea is that people think, you know, we have this incredibly active subsurface environment on Earth, on Mars the problem with looking for life at the surface is that,you know, the surface of Mars today and really for the last 3 plus billion years has been almost inhospitable, so why not go to the place where we think microbes could have lived for a much longer period of time, and that's kind of in these protected subsurface environments. So that's the argument for going to these, the astrobiological argument for going to the more subsurface crustal sites is that it's a very different type of astrobiological investigation that a lot of people are very strongly behind.

But you know, what's nice about Jezero is that we're kind of sticking to what we know from Earth. We know that in the Earth's geological records, going back hundreds of millions or even billions of years, that these [00:26:00] kind of lake environments are really great at preserving organics, at preserving biosignatures.

And so Jezero, on some level, is the safe choice in terms of what we know from Earth.

[Mat]: Isn't there an outside chance that this Rover might be able to reach one of, at least one of, those other sites?

[Briony]: Yeah, so that's the option that we're extremely excited about, is that, because of the incredible advances in mobility and software with Mars 2020, that we think we will be able to rove out of Jezero crater, onto the surrounding plains to one of these other sites, to the Midway site, which contains these ancient crustal rocks and ancient, maybe, crustal subsurface environments. We call this the Mega Mission, it's a really exciting possibility that we can sample both of these environments and maybe get both of those sets of samples back to Earth to look at as well; it would really cover so much ground, would answer almost every major question we have about Mars that we could answer upon sample return.

And so if we can do that, that would be, it would be a very bold mission, but it's a really, really exciting opportunity. [00:27:00]

[Mat]: Yeah, something to hope for, but still shame that we can't just send four rovers, right?

[Briony]: I know, right?

[Mat]: Um, what about those engineering challenges? I mean, I have read that this is not quite as friendly a place to land if you want, if those engineers want to get you down there safely to do science.

[Briony]: So Jezero and all the sites have been through a very rigorous Entry Descent and Landing analysis in terms of winds and altitude, you know, all these things that affect landing, and from what I understand the engineers are very confident about all four of the final landing sites, including Jezero. I don't know, I haven't heard any other details about specific program plans.

[Mat]: And I know some of that is because of more advances in the 2020 Rover over Curiosity, right, because it's going to be able to kind of zero-in much more accurately, I guess, on its actual landing site.

[Briony]: Yeah, so the landing ellipse size, which is area of probability that it will land on, is absolutely getting tiny when it [00:28:00] comes to Mars 2020.

We're talking about on the order of less than 10 kilometers across, but when you compare that to, you know, the European Exomars Rover, their landing ellipse is like a hundred kilometers long. And so just the technology that's gone into being able to do that includes things like terrain-relative navigation, where the rover actually senses the ground below it and can try to navigate to avoid big hazards, has really, really helped to reduce the size of that ellipse.

Jezero, the ellipse is actually partially on the delta which is pretty cool considering there's a big delta cliff running through part of the ellipse, but the engineers are confident that the rover can navigate that during the landing.

[Mat]: It's amazing. We have literally come a long ways on the red planet. You talked about this five-year process to reach this point: is this a good example of science working the way it should, and scientists working together the way they should?

[Briony]:I think so. I think that NASA has learned a lot from all the different landing site selection processes leading up to the Mars 2020. What I really like about this process is that it was a great [00:29:00] mix of community involvement, you know, the initial sixty or so sites were all proposed by the community, and up through the last one landing site workshop, including this last one, there was community presentations, you know, no one was sent away, anyone could present anything they wanted on any of these landing site. We have lots of great discussions. But we also had a lot of involvement from the science team on these landing sites and doing our own independent analysis, you know, and trying to think about, you know, what our rover could really do with each of these sites, which we have the best perspective on.

So I really like that kind of even-handed mixture of input from the community, but also the sort of rigor from the science team trying to keep everybody honest. So I think that ends up working really well, and I'm ultimately really happy with our selection.

[Mat]: You've been working on Mars- you've been a Martian, so to speak, for a long time now- but you've also worked with some people who've been doing this even longer.

I mean, I've looked at your involvement with the THEMIS camera on the Mars Odyssey Orbiter, Phil Christensen, old friend of this show, along with Jim Bell, who [00:30:00] you still work with, who is of course the Principal Investigator for Mastcam-Z and you work with him on on the Curiosity Rover. This is something that there are so many people that have been looking forward to for a very long time. I'm just, I'm wondering how you think our entire history of Mars, orbiters and rovers and just landers, have led us to this moment.

[Briony]: Well, I think that's absolutely true, that everything is built up to Mars 2020. I mean the reason, Mars is an interesting planet from so many perspectives,but ultimately the reason that space agencies all over the world have been so focused on it for the last 50 or 60 years is because Mars offers the promise of a place that was at least, at one point in its history, very Earth-like. It was very much like home, and that means the kind of life you might be looking for might be Earth-like.

We know how to look for it, we know where we should go to look for it in theory. And so that's really, it's been driving the Mars exploration program for so long now, everything from you know, Spirit, Opportunity [00:31:00], just verifying that, yeah, there were watery, watery environments. There were lots of different, diverse watery environments on the surface. Curiosity, with its enhanced payload, was able to tell us things like there are organics in these sediments, you know, the organics that could have been the building blocks of life that are present. And now, finally building up to the point where we think we know enough to actually choose a site to go look for ancient biosignatures in the rocks on Mars, which is an incredibly difficult prospect. It's difficult here on Earth, right, people are still arguing over what are the most anxious signs of life in the rocks here on Earth, even when we can go out and look at where they came from, we can throw them in any any laboratory on Earth and try to figure out what's going on.

Even with all that information, it is still a really hard prospect. So we're really hopeful that we know enough about Mars to at least give it a shot. We think we have the best chance we're going to have with the information we have to look for life on Mars. And so I think everything we've done, from the rovers in the past, even going back to you know, a little Sojourner that yeah we can rove on another planet all the way through to the, you know, scientific beast that is the Curiosity rover, I [00:32:00] think really built it to this point.

[Mat]: Where do you expect to be on February 18, 2021 during those seven minutes of terror as this new rover descends to a crater called Jezero?

[Briony]: Oh, well, I have to be at the Jet Propulsion Laboratory with as much of the Mars 2020 team as we can get in there. I think that'll be an incredibly exciting experience. I've been to, I went to Curiosity’s launch, but I've never been to a landing and so I'm really excited to be part of the team.

[Mat]: Well, I hope to be not too far away. Maybe we'll be doing one of our big planet fest celebrations watching all of you jump up and down when this new rover sets foot on the red planet and we will be doing the same and many more conversations about what's ahead between now and this 2020 launch. Briony thank you so much for taking us through this very important decision that has just been made.

[Briony]: Thank you.

[Mat]: We've been talking with Briony Horgan. She is an assistant professor in the department of Earth Atmospheric and Planetary Sciences at Purdue University in Indiana, and [00:33:00] as we said she's a co-investigator on the Mastcam-Z instrument, that main camera system that will be going on that rover to the crater called Jezero. She has been helping us to learn more about Mars leading up to looking for signs of life there for a long time time.

For What’s Up on Planetary Radio, it's time to talk to the chief scientist of the Planetary Society, Bruce Betts. is is that guy? Welcome back. Thank you. Good to be back.

Looking forward to joining you on stage at that big inside event at Caltech which may very well be sold out. So we don't have much reason to promote it. It was sold out and then they decided to open up the balcony. I'm hoping that as people hear this and if they want to come and join us at Caltech.

The morning of Monday the 26th at they might still be able to be there but you'll be there. Oh good so they will let me in. Yeah, they'll let you in and we're going to save a seat for you on stage. Okay, good. I hear that as the best view [00:34:00] not really because the big screen will be behind us in over our heads.

But no, yeah, but I want to do. Yeah, okay, then you're in good shape. What do you want to look up at the night sky? Well, you know winners Northern winter is coming because the Ryan is coming up in the evening now coming up in the mid evening over in the East with its bright belt and rigel and Bill Jews and all good stuff.

So look for that in the mid evening over in the east. And then in the West in the early evening, you can still catch Saturn low in the west and then Mars still looking pretty bright despite fading looking bright and reddish in the southwest day in the morning. It's a party with Venus hanging out to still near the blue star speaker.

And on December 3rd. The moon will be hanging out with both of. I always enjoy the night sky in the late fall winter because I can look up and say see there's Orion and sound like I probably know the other [00:35:00] constellations don't tell anyone. Oh, yeah. All right. We move onto this week in space history.

It was 2011 2011 the Curiosity launched on its way to Mars. Wow, that's amazing as since we're we were talking in this show about. Finally sending something else there to join it roving around on the surface. It's been since 2012 right that it landed. Yes. Yes, since we've had a successful and er, it's been six years.

All right, we move onto her head thumps Bears fan it short and sweet. I don't know if you've ever looked at pictures of the Crab Nebula and thought hey, that doesn't look like a crab. Here's the story. So first of all Chinese astronomers recorded the new appearance of a very bright star in 1054 ad visible even in the daytime.

The Crab Nebula is located where the Chinese astronomers said the bright guest star appeared in the sky. Now the [00:36:00] name Crab Nebula is due to a drawing of the nebula that looks sort of but I've looked at it and I don't see it like a crab made by William Parsons in 1840 ever since it's been known as The Crab Nebula.

That's a great story. Thank you. You're welcome. We move on to the trivia contest and I asked you. Well, I noted the dawn very successfully employed ion thrusters for propulsion. What was the first spacecraft to employ ion thrusters beyond Earth orbit, how'd we do Matt? Well, as I said two weeks ago, I'm always pleased when I know one of these off the top of my head.

Right there on the top of my head. Someone stenciled Deep Space Nine Deep Space 1. Yeah. That was me. You shouldn't have fallen asleep at the office.

Yeah, that's always a mistake Deep Space 1 good and our winner is Jack Shropshire Jack Shropshire in [00:37:00] Rancho Cucamonga you Jack Benny fans out there who indeed said it was Deep Space 1 he added. Ion engine to be even more valuable post Singularity when we can just send our Consciousness to the Stars on cubesats running.

Tiny super computers slow down. So Millennia feel like feel like days to be astronauts. Okay, Jack your way out there, but you're still the winner and what he's picked up is a copy of your book among other things. That's a new book astronomy for kids now available online and and everywhere all the places.

You usually get good books and it's very cool. We've talked about it many times also a planetary radio. And a 200 point I telescope dotnet account which show will come in handy after Jack row reads astronomy for kids because it's not just for kids is. No, no, [00:38:00] it's really for everyone, but it's got that snazzy title, but it's really for anyone looking.

I don't know to learn consolations besides just a Ryan here are some other great things. We got this one from Nara Hari Rao in Sugar Land, Texas. We've heard from him before we know of course that these ion engines in Deep Space 1 and for that matter and Dawn they use Xenon right as their propellant.

They do indeed. Well. He says. At about four and a half times. The density of air Xenon is the heaviest non-radioactive inert gas more mass implies denser packaging with a high mass to ionization energy ratio at easier to ionize as well. Hence. It is the ideal. And it's tasty they

don't don't try it at home, please that would be a noble experiment. Well Norman in [00:39:00] in the UK, he said record-breaking use of solar electric propulsion on Deep Space 1 achieve 27 thousand seven hundred miles per hour 2.7 times any prior spacecraft nearly equal to the velocity. Don's Delta launch vehicle.

That's that is that's pretty cool Torsten Zimmer. Always enjoy hearing from Torsten in Germany. He said and there were a lot of these Deep Space 9 references Deep Space 1 was decommissioned in 2001. And since then is only been visited by handful of aliens who had been duped into believing they'd find corks bar at the location Nick.

Jury, Scott Plains, New Jersey Deep Space 1 visited the asteroid Braille and the comet Borelli. Neither one unfortunately is an alien light sail spacecraft. Observing Earth. How do you know Nick? Well, we do know don't we because we looked up [00:40:00] close at them. Thanks to Deep Space 1. Finally Richard Hoffman in Greenport, New York.

Who says hey instead of rock paper scissors. Can we play comet stony-iron? Carbonaceous chondrite? Who is that sound sounds fun? That's it. We're ready to talk to you about another one of these. Here we go. It's gonna be kind of long but kind of interesting the answers long the question short what chemical elements were named after celestial bodies or the gods and goddesses For Whom the bodies were named.

Go to Planet rated org slash radio contest you've got until the 28th. That will be November 28th, Wednesday at 8:00 a.m. Pacific time to get us this answer and we got a nice little holiday package for you here in addition to a planetary radio t-shirt, which you can check out in the planetary Society store at Chop Shop

And a 200 point I telescope dotnet [00:41:00] account that great worldwide network of telescopes that you can use to look anywhere in the sky anywhere around the earth. We're going to throw in a copy of. The terrific kids book Max goes to Mars by friend of the show Jeff Bennett. We haven't given away one of these in a while.

It's really fun. And I think was kind of a children's literature bestseller Max goes to Mars part of that series of Max the dog books that Jeff came up with lots of good signs in there. Not a bad packages. No, it sounds good. Sounds fun. All right with that then I guess we're done. All right, everybody go out there looking for night sky and think about if you had the opportunity, what would you stand to stencil on Matt's forehead?

Thank you and good night. That's fine. You can write whatever you want on my forehead. Just don't put my hand in warm water while I'm napping, please. He's Bruce bats. He's the chief scientist for the planetary [00:42:00] Society who joins us every week here for what's up? Planetary radio is produced by the planetary Society in Pasadena, California and is made possible by its Martian members Mary Liz vendor is our associate producer Josh Doyle composed our theme which was arranged and performed by Peter Schlosser.