 So, I'd like to introduce our guest speaker, Bethany Elman is a professor of planetary sciences at Caltech and a research scientist at the Jet Propulsion Laboratory. She focuses her research on planetary surface processes, infrared spectroscopy, the evolution of Mars, and chemical weathering and hydrothermal alteration throughout the solar system. She currently is a co-investigator on the compact reconnaissance imaging spectrometer from our science team, a participating scientist on the Mars Science Laboratory mission, and a co-investigator for two instruments that are part of the Mars 2020 mission. Please welcome Dr. Bethany Elman. Okay, great. Thanks, Brian. It's a pleasure to be here and to be presenting. Let me just get my screen sharing going here now that we're done with the introductory comments stand by. Okay, so I think you all are now seeing my screen. If not, Brian speak up now. It looks great. Okay, fabulous. So, I'm going to give a little bit of a roaring tour through some of the most exciting things that we've learned about Mars habitability through our orbiters like the Mars reconnaissance orbiter there on the left and through our rovers like the Curiosity rover here on the right over the last 10 to 15 years of exploration. And so to this audience, I think Mars needs relatively little introduction. It's the fourth planet out from the sun. It's larger than our moon, but smaller, of course, than Earth itself. But because not everyone thinks about Mars every day, let's get all of our facts in order here. Mars' size is about half that in terms of diameter as that of Earth takes twice as long to orbit the sun. But like Earth, at least at the moment, it is tilted on its axis at 25 degrees. And so like Earth, it has four seasons. The day is about the same length. But the critical parameters for setting the environments and potential habitats on Mars are what you see next, which is the solar flux. It only gets 43% of the radiation, solar illumination that Earth gets. And it only has a six millibar atmosphere. It's 96% CO2, but it's very, very thin, 0.6% of Earth's atmosphere. So those two parameters combine. I mean that Mars' average surface temperature is a rather chilly minus 63 degrees Celsius. And in terms of surface composition, some of you may be geologists or rock aficionados. So unlike Earth that has large sections of continental crust and some of the rocks that we might be familiar with, like granites and quartz sandstones, Mars is a different composition. It's basaltic. It's similar to the composition of our own oceanic crust and also to some of the volcanoes that you would see if you went to Hawaii and to Iceland. So hot spot volcano type composition. So a different starting chemistry too, a little bit more iron and magnesium rich. Now this temperature range though, cold though it is, is a large range. So the average diurnal temperature flux. So over the course of the day at the equator on Mars, the average surface temperature does rise above freezing. It's about 15 degrees Celsius above freezing. So that's pretty balmy, 40 to 50 degrees Fahrenheit for those of you who think in that system. But because of the thin atmosphere, it doesn't retain the heat and plunges at night. Now nevertheless though, Mars with its atmospheric pressure, the range is shown over here on the y-axis of the plot. The temperature is shown spanning up to about 283 degrees Kelvin on the x-axis of the plot. Mars even today has a very small interval of time and conditions where actually liquid water can be present on the surface today. So it's largely cold. It's actually frozen in the solid realm. But there is a period where water is there. It's ephemeral. It's not stable against evaporation, just like bodies of water on earth evaporate. But it could exist if it can exist for short periods of time. This of course is very interesting given one of the most exciting discoveries made in 2010 by the Mars Reconnaissance Orbiter, the high-rise camera snapping these pictures of these downward moving dark streaks that appear right as these terrains cross the freezing point of water in Mars summer months. So are they ice melting to make fresh water flowing down the sides of craters? Are they some sort of a salt that's letting off of its water to form a brine? Or are they something else? Are they something potentially less exciting like dust avalanching? This is I think one of the most exciting discoveries and we continue to monitor these with orbital spacecraft and it will remain for the future to test out exactly what these are. Now these features called recurring slope lineae, it's a complicated name recurring because they happen multiple years, slope because they occur on slopes, lineae because they're linear features. We didn't want to give them a name that was like water streaks because they're not sure that's what they are. So these recurring slope lineae occur in these areas that the stability of water diagram predicts that for small amounts of the Martian year, 20 sols, sol is a Martian day, the 20 sols, 16 sols, these are the pockets where liquid water might exist. So Mars sits right now kind of as a planet on the edge. It's just right at the point where it can support small amounts of liquid water but it largely sits in a deep freeze. And here's an example of, we've known about the freezing part for a good long time. This is a beautiful image I think of frosts that were deposited overnight at the Viking II landing site in the mid-latitude northern hemisphere of Mars. Now the other thing we've learned in the last 15 years or so of exploration is that Mars is an active planet, an active geology. So as a geologist I get excited about things like seeing dust devils streak across the surface as we saw here with the Spirit Rover. We've also studied sand dunes migrating across the surface of Mars. We've also caught avalanches in the act. Here's an example coming off the northern pole of Mars, the thick polar ice caps that sit on the poles. And you can see the fine layers there of dirty ice and their instability in the spring. Now it's worth pointing out, especially given that today is the solstice, we should ask, well what season is it on Mars? Is it the Mars solstice? Well, so the annotated figure at the top of the slide shows Mars' orbit. The orbit is actually more eccentric than Earth's. Earth's is a little bit more circular. So Mars, as I said, is tilted on its axis about the same. But as it goes around the sun, the southern hemisphere winter, which occurs on the right-hand side of the plot, is actually a bit more severe than the northern winter due to the fact that Mars is actually appreciably, I think it's on the order of a percent or two, further from the sun. So that means less insulation and that means colder. Season on Mars, there's no calendar with named months. But seasons on Mars are kept track of this parameter called Elsebess, which is measured by the solar longitude. And there's a figure here in the lower right-hand corner of the plot. I've marked where we are today, Elsebess 22.9. So that means we're 23 degrees from the northern hemisphere spring equinox. So it is spring on Mars and events like I just showed you, like landslides off the polar cap are going to be starting again soon this year, as the ice is warm up and in some cases start to become unstable. So that's where what Mars is experiencing now, northern spring and southern fall. While we're on orbit, there's something absolutely crucial also about Mars's spin axis parameters that really I think is going to be a profound part of Mars's geologic story as we continue to unravel its history and its evolution. So what the figure on the upper left is reminding you of are just some of the showing the axis schematically, rotation about the axis of Mars and then a procession or a wobble to the axis of Mars. Interestingly and unlike Earth, Mars wobbles like a top. It has an unstable axis. There's no large moon to help pull on the equatorial bulge and help stabilize the planet. So Mars is very wobbly. In fact, what you can see on the plot on the lower left is that even over the just the last three million years in a geological time, that's not that long. Earth and Mars are more than four and a half billion years. So just these last three million years, the axis has shifted between the 25 degrees that we see now, all the way down to 15, all the way up to 35. And this profoundly influences the climate on Mars and where we see ice on the surface of Mars. And that's shown schematically on the right. When Mars is straight up and down, the polar caps can grow seasonally because they don't get a lot of insulation. But when Mars is tilted on its axis, those caps may even disappear and go to the surface. And this is cool because you can see from how this fluctuation is happening. I mean, this is just hundreds of thousands of years ago that Mars would have been in this particular and different climate regime. By comparison, Earth's wobble is only one degree. And so I think we need to think of Mars not actually as a static environment, but one that's very dynamic, driven from orbit. A final example, talking about some of the consequences of this relates to a new discovery that was made in the South Pole of Mars in 2011. So the South Pole of Mars is this beautiful sculpted region of canyons through water ice. So the bulk of the pole is more than a kilometer thick of water ice. It gets a thin CO2 frost seasonally on the surface. But what we found in 2011 when investigations were made via radar to send radar waves through the cap was that, in fact, there was this particular region where the dielectric properties of the material as sensed by the radar were just fundamentally different. And the best explanation for the data to explain the returns from the radar signal is that there's actually a large layer of buried CO2 ice beneath the polar cap of Mars. And using estimates of the volume, the volume of that would almost double the atmospheric pressure of Mars if released. And really, it's a question of when released because we know those polar caps are unstable against the obliquity fluctuations on some time scale. And so just to bring that point home with the diagram that we looked at before as to the range where liquid water is stable on Mars, it expands the range by more than doubling the parameter space on Mars where water could be present on the surface. So modern Mars is a pretty exciting and dynamic place. It sits right on the edge of where there's water and maybe even as recently as 100,000 years ago, it would have been actually a far more clement place for life driven by these obliquity cycles. Now I'm going to transition for the entire rest of the talk to to the past and past habitats on Mars because of course in the past, water is even, there's even more evidence for liquid water and water was at times, apparently quite abundant on the surface, abundant enough to carve these large channels that you see heading through the southern highlands of Mars. This is a topographic image of Mars where red is high and blue is low. And you can see these canyon systems carving through the highlands and then draining out into the depression in the northern lowlands of Mars, which looks for all the world like it might have at one point in history held an ocean. We've known about morphology for a while actually since the first missions in the 1960s and 1970s we've seen this and these enigmatic channel of evidence for possible past oceans. But what I'm showing here is a sequence of missions. Originally the Mariner mission in the 1960s kicked off the exploration of the red planet. The only missions to successfully land on Mars and operate appropriately were Viking one and two in the 1970s, which brought back some beautiful images of the surface tests of the chemical composition. But then planetary exploration shifted elsewhere the NASA budget shifted elsewhere and it wasn't really until the 1990s that interest was renewed. Some of you may remember two failures back to back at the end of the 90s. It was a risky time. It required some political will to continue the program. But the program continued and if you look at the 2000s decade, it's seen both the European Space Agency and NASA send successive orbiters, rovers, landers to the surface. And so it's been an incredibly exciting decade for probing Mars history. A lot of what I'm going to talk about today, some of it is based on images, which I think we're all familiar with. And some of what I'm going to talk about is actually based on infrared and spectroscopic data. So I know that you're a lot of astronomers on the line. Most of you are looking through the telescope making, I'm sure, beautiful digital images. I suspect that some of you probably are making digital images in the infrared. And a few of you may even have spectrometers on the telescope where you measure the signal of wavelengths coming off of the star at out from the visible into the infrared wavelength of light. So one of the instruments called an imaging spectrometer is what we do to look at the infrared on Mars. Mars is actually proven to be incredibly interesting in the infrared because it lets you see to some extent features that are obscured by dust in the visible, dust that obscures what our eyes can see or is apparent in the infrared. The instrument that I spend a lot of my time working on from orbit is this instrument called prism. It scans the surface line by line acquiring one line of an image on the surface and then the wavelength in 544 different colors of light from the visible to the infrared and showing an example of some of the spectra down on the lower right. What's interesting about prism though is that it sweeps across the surface and it builds up this image cube which is on the right upper right. So for any latitude and longitude you have a beautiful image for any one given channel. But each of those pixels has an associated spectrum so you can drill in and look for fingerprints or absorptions of different gases and different minerals using prism. So this has led to some spectacular discoveries. So what this image is, it's a grayscale image acquired at 6 meters per pixel by the context imager. But then I've used prism false color infrared data acquired at wavelengths between 1 micron and 2.5 micrometers of light to colorize the red-green blue channels over the small portion of the image that you see in the middle where we had an overlapping prism image. And what this is showing is you can see this channel heading into a deltaic feature. This is a past lake called Jezero Crater and you can see here the elevation map. You can see the crater. We're looking at the delta which is in the channel which is right where the arrow is here. And if you look just to the left upstream of that you can see faintly in the topographic data these channels that head there. These are paleo rivers that flowed into this crater leading to the formation of the lake. And then if you look at the right-hand side of the crater there's actually an outflow channel where these waters came out. What this spectrometer has enabled us to do is to look at what are the sediments in this crater made out of. So the sediments that are making up the bulk of the delta and the bulk of the deposits around the shore of the lake are that beautiful greenish color. And what that means spectroscopically what they are what we're seeing is H2O, OH, and CO3 in the mineral structure. And so it's a mixture of carbonate and clay and this indicates that there were well waters interacting with rocks to form these minerals. And also that those waters were relatively neutral to alkaline. Some of you may have done the baking stone and vinegar experiment right if it's acid the carbon would dissolve carbonate would dissolve. So these are neutral to alkaline waters in a lake. It was a great discovery. We've also found evidence for very acidic waters elsewhere on the planet. This is another example of what this combination of imaging plus spectroscopy can do. So on the lower left-hand side there was a prediction made by Jeff Andrews Hannah in 2010 that there would be a few craters on Mars where if ice were melting on top of some of the large volcanoes that groundwater would flow underneath the surface and then up well to form lakes in some of these craters. So this was the prediction and we're looking right now in the background there this this bowl shaped crater is cross crater. So it's one of the craters that Jeff predicted the lake sediments and it's a 70 kilometer impact crater. And there's over 500 meters of layered sediments that contain clay minerals like the olinite, marlinite, and then these aluminum sulfates that only form under acidic conditions. You might find these in some of the weird and rare acid lakes that occur in Western Australia or around volcanic fed lakes that are near steam from magma that's being let off that acidifies the waters. So this was a key discovery too. So we have both alkaline lakes and we have acid lakes depending where and when you are on ancient Mars. This is probably over three billion years ago judging by from the we judge age by crater counts, counts of number of craters on the emits and these appear to be quite old. I can talk more about that in questions if you want. Finally, another example here's a huge stack of layered clay minerals. We were able to see with the high rise camera and false color infrared this beautiful kind of bluish layer that cut across above the more typical reddish tone unit and with spectroscopy we were able to pick out that this was a unit of aluminum clays sitting atop iron clays. Now on earth, a scenario where this forms is like the image that I'm showing here. So minus the grass and the vegetation that's growing on top of it, what actually has happened here is that you had initial rocks, in this case iron and magnesium rich igneous minerals that partially were transformed a little bit by waters interacting on the surface. But then over time, as the surface was stable and you had rain over and over again or snow melt over and over again waters flowing through the upper surface leaching it out, removing some of the metal ions leaving behind these aluminum clays. So this may be a product of very extensive water and rock interaction on Mars these similar types of deposits. Finally, a last example I'll show and it's actually the most common chemical mineral fingerprint of water that we see on the planet is that which is exposed by impact craters. Now, unlike earth there's no deep drilling to expose what's going on in the older deeper layers that we can't see. And so we geologists have to rely on impact craters to act as our very crude drills right when the impact created when the meteor hits the material in the ejecta are excavated out and then deposited on the surface. So what I'm going to show you now is from the orange box next to this 45 kilometer relatively fresh looking crater. We're going to look at the ejecta and when we make mineral maps with prism and consider the spectrum, we can identify all kinds of mica minerals, chloride minerals, this one particular mineral named Prenite. Okay, these are these are names of what it what would this look like? Well, they would probably look like in like rocks like this you rocks you probably seen hiking about. So overall they're volcanic rocks, but when you look at vein at the veins, you see, in this case, white and green minerals from water having flown through them and hydrothermal and groundwater systems underground, leading to the precipitation of minerals. In fact, this one particular mineral mineral Prenite, it's a calcium aluminum silicate. It's actually a pretty special mineral because it's stability field is relatively narrow. So it tells us that these waters that flowed through that created these minerals are were between about 200 and 300 degrees Celsius and relatively low in CO2 so probably out of contact with the Mars atmosphere. So this is evidence of groundwater hydrothermal systems on Mars. And this is something you see as very widespread across the surface. This is just one example of a small four degree by two degree bin of looking at some of the impact creators and the evidence for these type of minerals associated with them. So Mars is most ancient buried crust has been water altered almost everywhere and we didn't know this until the Christmas spectrometer started mapping in 2006. So it's pretty clear that Mars was once re and a half billion years ago, a water rich, rich world. So the question is really what changed? Well, we continue to explore this. This is a bit of a technical figure, but for those of you who are minimal at this unados, you can see that it's what I'm meaning to illustrate here is that everywhere we look in Mars is most ancient southern highlands. The southern highlands are the impact crater portion of Mars. The older terrains have more impact craters on them, the smoother terrains are younger and have fewer impact craters. I think you can see that it's it's in the oldest terrains where we see evidence for all of these water related minerals and depending where you look, it's different minerals in different places. There are clusters of carbonate. There are clusters of sulfates and in other minerals. So depending where you go, water chemistry on ancient Mars varied in space and time. The question is, well, what changed, right? Why did Mars go from this once water rich world to the relatively cold and dry planet we see today while Earth seems to have comfortably maintained habitable environments for life from microbes to us over the last four and a half billion years. It's really this question that drives some of some of my exploration. Just a bit of history on this topic. So I'm first on the on the top here and I'm showing the timeline of Earth, what we think we know about history. Sorry, the slide formatting got a little disrupted, but I think you can see what we're seeing is the ethics of geologic time on Earth. You're all stronger. So I probably don't have to tell you that the solar luminosity changes with time. Our sun was probably about 60 to 75% less bright. Initially, it's been getting steadily brighter over time. What are the implications for the evolution of planets is that means that planets initially got less sunlight and probably colder and then and then progressively got more solar radiation and of course early in history. Planets were being bombarded. Now on Earth, it's very hard to figure out exactly what the environments were like during the Hadian and Archean because we have plate tectonics that recycles and destroys a lot of these rocks. Less than 1% of Earth is more than 3 billion years old. On the other hand, as a planetary scientist, I'm very fortunate in terms of thinking about these early processes like changing solar luminosity impacts how they affect the development of oceans and of life. I'm fortunate to have Mars and me and my colleagues study the over 50% of the rock record of Mars that relates to this early time to understand the lake basins, the hydrothermal minerals, the valleys, the outflow channels and why they went away. So the big questions are what processes sustained the early habitats that we see. Did life develop on Mars as well? It's during the time period that life began on Earth. And then why did Mars change? Why did Mars change while Earth stayed an excellent habitable environment? Well, in terms of investigating this question, I've talked to you about the results from what we're doing now and the missions that are active now. You can see the three NASA orbiters there, Odyssey, Mars Reconnaissance Orbiter and MAVEN. The European Space Agency also has its instrument. And then the MOM, the Mars Orbiter mission is actually from India. And Europe also has the Trace Gas Orbiter. So it's an international fleet of India, Europe and the US around Mars right now with the Opportunity Rover and Curiosity Rover on the ground. We'll talk a little bit about the results from those rovers, but we're also going to talk about what's in the future. So later this year, Mars Insight, the next lander that has a seismic station and a weather station and a heat probe on it, will launch. So keep your eyes peeled to the news for that launch. And then coming up about two and a half years from now, hardware is being built at the Jet Propulsion Lab where I work as we speak. The Mars 2020 rover will also launch. So the 2020 rover, which as Brian said in the introduction, I have the pleasure to be a part of this team, has really three particular roles. One is to act just as like the previous rovers to explore the geologic history of Mars to understand whether there were habitats on Mars to look for potential evidence of life. The second is to prepare for human exploration. There is an experiment that's being conducted on a rover. It's a technical experiment. There is an instrument called MOXIE that is designed to convert CO2 to oxygen. And it has goals to produce a certain amount per day and it's a technical demonstration because if and when we send humans to Mars, we will need oxygen both to breathe, as well as probably to act as a source in rocket fuel for combustion to occur. So that's the second goal of this mission. And the third is to prepare a sample cache for eventual return to Earth. Nothing that we've sent to Mars has ever returned before. So the only samples we have are meteorites and we don't know where they come from on the planet. This is an opportunity to collect the samples that we want from the place that we want. And this rover would have, and I'll try to play the video here, the rover. This is the first rover that would try to collect samples for eventual return to Earth with this coring system. And you can see this prototype of the Jet Propulsion Lab eating its way through the rock. Slowly steadily. This was done over the course of about 20 minutes or so and then retracting back out. So this coring instrument produces cores like you see on the lower right hand side of the screen here. They're about the size of a piece of chalk. And these would then be placed one by one into the canister. And then the canister dropped for a later return by a rocket to launch it back off the surface of Mars and toward Earth. Now, we don't send rovers to Mars that often. When we are on the ground, we learn a tremendous amount. I mean, consider what you would learn from looking at the rocks as you, for example, hike through the Grand Canyon versus what you would learn from the rocks from a plane flying over the Grand Canyon. The answer is, of course, you learn much more, the closer you are, the more you can see the textures, the fine scale of the minerals. These are the fingerprints of history recorded in the rocks. So given all of these fascinating sites, each of which has its own story to tell about liquid water. You pick the single one that gets the rover. Well, first you pick your science questions and we've got those habitats life and why did Mars change? And the second thing that we do is we learn from the past. We learn from our past experiences of picking landing sites. Now, in yellow on this map are the locations where that we've landed before. We landed the opportunity landing site right in the middle of the planet. And on the right hand side of the screen, the Gusev crater landing site and the Gale crater landing site. So what did we learn by these sites as selected places for rovers to have landed? Well, the Spirit rover landed at Gusev crater, which you see here. Gusev was about 200 kilometers south of the Apollonaris volcano. It is a 120 kilometer or so crater with a valley that breaches its side. So it looks like there was once a river flowing into this crater. Very exciting. But when we landed, there was not any evidence immediately for lakes. Instead, it looked like we landed on a bunch of old and dust covered lava. You can see the angular dark rocks there. Well, where's the water story here? So having faced with that at the landing, the lesson here is that geologic context really matters. That is not only knowing that there was perhaps like once a lake or once a hydrothermal system there, but pinpointing exactly where it is and making sure that the rocks that are responsible are present near the surface. There was considerable debate about this before landing because some people were saying you're going to find a lava. Some people were saying you're going to find a lake. The lava folks are right when the rover landed, lava was found. But all was not lost because these rovers were supposed to last for 90 days and travel 500 meters. And thanks to some good American engineering, the spirit lasted in total about seven years and ended up traveling tens of kilometers. And so you see the truck here. We landed on this lava plane, but over the course of the first half year of the mission, made the way to these hills because these hills were the only chance of getting out of these lavas and getting to older and potentially more interesting environments. And finally toward the end of the mission, you can see the winding path that spirit took to the hill. We arrived at this interesting feature from orbit called the home plate after the obvious resemblance to a baseball plate. And you can see the layered material is considerably brighter. What we found when we got to this location was that these rocks were different. These rocks were every 70% silica and either formed from a volcanic humoral like you might find from volcanic gases venting out of the surface. Or a hot spring type environment is the other place where you find these rocks and El Tatio, a high altitude, cold, but volcanically fed hot spring. And Chile has been suggested as a potential example for what the spirit rover discovered after it's years of trekking. So this is certainly an interesting environment, an interesting potential habitat for life that was discovered by spirit after having trekked for a half of the year to get out of the lavas. Now the second landing site from the Mars exploration rovers was the Merdiani quantum or Terra Merdiani landing site. And this landing site, we were drawn to it for two reasons. The first is it just stood out like a beacon in the mineralogical data that was available at the time. This is the map of large chunks of hematite FE203 that was seen from tests. And clearly it's an outstanding example because if you look elsewhere on the planet, there's no deposit like it. And this is what this type of hematite looks like. We didn't know what we were going to find exactly, but on Earth these are the types of rocks that have that spectral signature. Now the other thing is it wasn't just hematite completely out of context when we looked at what hosted that mineralogic signature. It was these beautifully layered sediments that were seen in various locations exposed in a rodent throughout the plane. So that is where opportunity was sent and opportunity landed an interplanetary hole in one bouncing to rest inside an impact crater, eagle crater. And you can see it immediately went to work roving the crater and exploring that outcrop of rock over the distance. So deployed its chemical instruments and then discovered immediately evidence for past surface waters in the shallow lake. Here on the lower right you can see the ripple marks preserved in these kind of scoop shaped features in the rock that I'm pointing out with the red and the blue arrows. And you can also see that at some point in time there were ground waters coming in and out of these rocks because the carrier of the hematite signature ended up to be these little concretions. So they grow from a tiny crystal outward, spirally, within the sediment. And apparently there were also these once these longish rectangular crystals because you see the rock is sort of crisscrossed with these empty holes. But whatever waters went through and deposited them something about the chemistry changed because now and then they re-dissolved because now these holes are empty. There was once a crystal there, there is not a crystal now. So this is pretty exciting. When we look at the chemistry of these sediments they're rich in sulfate salts, silica, and then that hematite signature that beacon that drew us from orbit. So what is the lesson here in this landing site selection? Well I think the lesson is both follow the minerals and follow the layers. That is look for the chemical and mineralogical fingerprints of water. And also look for rocks that are very well ordered, one on top of the other, so that they can be interpreted. This is perhaps in the modern sense what that opportunity site would have looked like. This is from the United Arab Emirates and it's fly lakes in between sand dunes. And after a few years of exploration and seeing the rock types I think this is the closest modern analog. Shallow lakes among sand occasionally dry, occasionally wet, but largely by groundwater. Okay so that was two landing sites, the Mer rovers, and now finally Gale Crater where the Curiosity rover is exploring now. So on the right hand side of the screen I have everyone's image up so I can't see it. But there's an arrow that's pointing to Gale Crater and we were drawn to Gale because of its layers and because of the sulfates and the clay minerals that were there. And this pile of sediments is located in the center of the crater. The crater was created and then subsequently filled by sediments. And this mountain of sediments had a very characteristic layered mineralogy to it with an ordered sequence of minerals. And that's what we've been exploring with the Curiosity rover for the last five years since 2008, since 2012. And we've made it over 14 kilometers and are now climbing through these lowermost Murray formation materials which are rich in clays. And we're just about to get to this red hematite ridge which you can see toward the middle of the layered set of materials. So what's the little lesson three from this? Well it took us a little while to get to the juicy minerals. On the right hand side I'm showing the travers. It took us the rover nearly three and a half years to get to the most interesting materials. And so I think we've learned again that you want to land near your best science targets. But we've also learned really that looking at small scale is just beautiful because this landing site has proven to be even more interesting from the ground than we could have hoped for from orbit. So some of the things we've seen are these finely layered sedimentary rocks which indicate a past lake within Gale crater. And we've also seen these amazing intricate vein structures criss-crossing and fracturing the rocks which indicate even longer lived ground waters that have been flowing through these sediments leaving behind minerals. So in my last five to ten minutes here so I'm going to transition now to the future in a process that is happening right now which is the process of picking the Mars 2020 landing site. And those of you who are curious about this should write down Mars Next because if you Google Mars Next you'll arrive at marsnext.jpl.nasa.gov where all the documents and up-to-date status of the landing site process is recorded and available for all to peruse. It's a kind of a knock-down drag-out fight actually in some ways because each of us scientists wants to go to the most exciting place for Mars science but of course we don't all agree exactly which site that is. So hundreds of sites were proposed. This map here is sort of complicated looking but what it's meant to illustrate is that there are some very fundamental engineering factors that limit where we can go on Mars. So we had to go between 30 degrees north and south latitudes because otherwise during the winter it would be too cold and the rover would basically be spending all of its energy just on surviving the winter. So it was heating enough to preserve the electronics, to not have anything fractured due to the cold, and it wouldn't have enough energy to do science and deploy its instruments and energy to operate those instruments. So restricted in latitude and then also restricted by elevation. So I'm sure you need the elevation of Mars but where the elevation is higher than zero kilometers above the data it's blacked out because it's too high. With the landing system we need the column of the Mars atmosphere to help slow the rover as it by parachute and enough time for the rockets to slow the rover to delivery to the surface and higher the elevation the shorter the time so we need to land in a relatively low spot. So only certain areas were accessible yet still hundreds of sites are interesting in this area and indeed hundreds of sites were proposed at the first workshop and they were judged based on science interest. Remember those big questions. Landing site safety. You know when you took a closer look where they're big boulders sitting in the landing site the answer was yes for a few of those sites. And then maintaining some semblance of diversity and of different types of science goals of the resource constraints so that's how we went from 100. It is the sort of survival style driven by those three parameters after two landing site workshops then there were only eight. And those eight were four different types of of Lake or shallow water settings on the on the left hand side Olden Crater Mill with Kazma Edwards Wally crater and Jezero crater. And then on the right hand side. One thing you would recognize is Columbia Hills of goose up crater which is actually where the spirit rover went. Those were excited about the hydrothermal system wanted to head back there. And then the other three on the right hand side sort of service major mark ballast and really positive talk are really really ancient box. Their places were canyons and erosion have exposed Mars is oldest and mineral rich rocks. So then there was a third landing site workshop and you can read about it on the web if you want but then there were three after that and what survived was basically three very different types of sites. And that's where we sit right now actually with these three incredibly different sites Jezero crater. The amazing Delta Northeast service major the ancient lands and then the possibility to go back to a place that we learned about before. So let's talk about each of those super briefly check in my time here. Yeah super briefly. And you feel free to ask more about this I want to make sure to leave time for questions. Both Jezero crater and the Northeast service landing ellipse are very close together there and that's because they're in a particularly interesting fascinating part of Mars. One of Mars's largest impact basins sits there formed about four billion years ago. And then exposing rocks very nicely for us geologists to see the basin cause falting as the crust drop down and adjusted in response to removal of all this mass. So there were these giant faults these concentric faults that are called Robin nearly Fossi over to the Northeast. And then toward the south you see this lava flow coming in this lava flow came in about 3.5 billion years later where these two landing ellipses are. The rover has to land within a 25 by 20 kilometer ellipse it may shrink as we get to know the landing system better but that's where the two ellipses are one with land. And you would be able to explore the sediments on the inside of Jezero crater one with land and you'd be able to explore the canyon lands. It's probably too far to travel between them it's about 70 kilometers and the drive distance on Mars record is 26 kilometers these rovers are not meant for distance they're meant for. Detailed investigation of the single site to the oldest lake delta maybe Jezero which you saw earlier this beautiful. A set of sediments with carbonates and clays from an alkaline lake you can see a close in our highest resolution imagery. Then forms from channel switching events that could be investigated to trace the history of this lake about the size of Lake Erie. At Northeast service major it's completely different type of terrain it's not as obvious immediately what it is you have to look up close and combine mineralogy and morphology and so I'm zooming in here to the white box. And what you see when you look in the white box are these amazing layered deposits with three or four different units within them an ancient basement of clay rich rocks. A in green a carbonate rich area where we have ground waters flowing through and then a lava or a volcanic ash up at the top. So there's a beautiful stratigraphy shown here in cartoon form that the rover would crawl through going from 4 billion years ago to 3.5 billion years ago sampling all of these different materials and the environments in between. Because it's a little hard to visualize I recently worked with an artist at National Geographic to help sketch out so this is what it might look like today. And if you were to go there during while it was in its heyday with liquid water this is what you might see waters underground but emerging in springs to form rivers that carve the landscape into the canyons and maces that we see today. And then finally the other option is return to the known to go back where where spirit was we know that there are some interesting things there. Spirit Rover did not have the life detection capabilities that to detect organics. For example, that the 2020 Rover what he had so there's a case being made that these silica deposits are the most the best most interesting thing that we could we could do, and that perhaps we would be exploring active hydrothermal systems like this. So, and then there are three and this is where we set the next landing site workshop will be I believe in spring of next year. We have these big questions left outstanding how these landing sites stack up is there they're at slightly different points in time northeast service lets us investigate a really old period of Mars. Jezero and the spirit landing site somewhat younger periods of Mars history and I will go ahead and reveal my preference. I'm kind of like the old explorers and where the map says here there be dragons, which is the case for the oldest terrains on Mars. Well that's where I want to explore. That's where I want to go. And so northeast services is my favorite site because I think we have the most potential word in there. And just with the thought that we haven't yet set humans to Mars, we may at one day but in the meantime the rovers are proxy and their shadows are the proxy for our shadows reaching out and exploring Mars. So with that happy to take any questions. Okay, well that's great. Thank you very much Dr Elman we do have a couple of questions that have come up and so we have Jeffrey is asked, except for recent impact cratering changing the surface. How young are the features on Mars are any channels really young like less than one billion years old? Yeah. Okay, so let me that's a great question. So how old are these various water related features? I don't have a superb map of this because I didn't focus on this topic, but I'll answer it in stages. Yes, there are a few examples of relative of young water related features. In fact, there are some that are probably younger than five to 10 million years old. They're very fresh looking. They have very few craters on them. There's a little bit of a debate as to whether they're due to water due to CO2 ice. I think a lot of them maybe due to CO2 ice, but there are a few examples where there are very sinuous channels and then fan shaped deposits coming out of them. But I think you're best explained by water. Now these are relatively small water related features. They're there. They're usually on the walls of impact craters and in size, there may be a kilometer or so in size from the top of the channel down all the way to the bottom through the fan kind of like in a real fan out in the desert. You see fans coming out of the mountains in terms of the big channels, the big valley networks to form lakes. And the outflow channels from age dating based on crater counting. We think those are those are actually quite a bit older, like 3.5 billion to 2 billion. So there's a difference in the scale of water related activity used to be big large scale planet wide and it's gradually just become more localized over time so that there are probably only a few special places now that that was water. Okay, I'm going to kind of combine a couple of questions here because I think that they're related. And so we have one person asked what type of sensors will the 2020 Rover have but then Carol asked what instruments methods because I think that these relate our best use on the rover to estimate the age of the rocks and so kind of combining a couple of things. Okay, okay. Well, let me tell you a little bit about what's on board the 2020 Rover. So there are two instruments that sit on the mast of the rover for remote sensing. One is a camera. It's actually very similar to the camera on curiosity. It's called mass cam Z. So it's like curiosity is mass cam except it has a zoom lens capability to go in and out of the landscape that has visible and near infrared filters below one microbeater. Then on the rover there's a bit of a Swiss Army night spectrometer. It's called super cam, which is kind of like chem cam on the curiosity rover. So super cam like chem cam is a laser induced breakdown spectrometer so it can shoot a laser at a rock and look at emission lines from the plasma to see different elements in the plasma. And then super cam also has the ability to operate its spectrometers in passive mode where it's simply looking at reflected light off the target and also can look at Raman spectroscopy. So rotational and vibrational absorptions do Raman excitation. So those are the two remote sensing instruments. The other remote sensing instrument is a ground penetrating radar. That's actually a contribution from Finland. And they'll be looking underground to see if there's any ice or to look at layers of rock under the ground. I mentioned already the tech demo that converts oxygen and carbon dioxide. So the remaining two instruments are on the arm of the rover. In addition to having that coring system on the rover arm, there will also be an X-ray fluorescence mapper called pixel that will be able to look at a rock and make a map of the chemical elements over a small portion of the surface. And then there's another combined microscope and Raman spectrometer and UV fluorescence instrument named Sherlock that also looks at a small area on the surface and makes a map of where organics are and where minerals are on the surface. So that's the science payload that we've got. In terms of looking at the age of rocks, the age will remain a relative unknown at the landing site. So there are instruments that were proposed for the rover that would have permitted the pretty accurate age determination on site. But it was judged that there was not enough space to put them on this particular rover, given the space that had to be taken up by the drilling system and the coring and the caching system. So for this rover, we'll have to continue to make age estimates from orbit and then when the samples are returned back to Earth, do the age data on Earth. Okay. Well, here's, we have an interesting one from Helen, kind of saying with the theme of old rocks, mentioned that the oldest rocks on Mars were affected by water. How do you know that the surface wasn't revealed and then affected by water later? Yeah, that's a good question. A very good scientific question and that's always the thing that we have to prove. What you basically have to prove is the relative timing of events, right? And so how do you prove the time ordering of events? Well, you have to look at clues like texture. So for example, something that some people said early on was, well, maybe it's a rock, and it just looks like it has a lot of minerals on it because it's only just the outer surface. And your instruments from orbit only see the outer, you know, hundreds of microns, maybe a millimetre into the rock. So how do you know that it's actually that whole volume of rock that's altered? And it's not just like a little weathering patina or a skin that was formed later. Okay, so yeah, legitimate question. And so the way we do this is by geologic context. What you do is you look for exposures where from all different sides, the same mineral composition is observed. You then look to see if an impact crater more recently has punched through it, whether the layers that are exposed to the walls of that crater have that same mineral signature. And if the answer to all of those is yes, if on different sides of the outcrop, on boulders that might sit on the base of the outcrop, on craters that punched through, then the simplest explanation to explain all of that data is that it is just the rock itself that's altered, and you're seeing it from all different angles. And so that's one of the ways that we get at the relative timing. So here's by looking at just the physical relationships between altered and unaltered materials. A lot of times what you'll, sometimes what you'll be able to see is in like a canyon or a scarf, you'll be able to see different distinct layers of rock that have different colors. And the different colors correspond to different minerals. And then toward the top of the section, you'll get to a type of rock that doesn't appear to have any water related absorptions with it. And so, again, the simplest explanation is that it's the bulk rock that's been altered. And it would be hard to alter the bottom without the top. So we got a couple other questions here that seem to be somewhat related. And kind of to start out, what is the mission life span for the 2020 Rover? And you had mentioned about the sample caching samples for return. And I guess will the 2020 Rover make those caches and what types of samples and kind of what kind of time framework there be to get those back. Yeah, so the Rover mission is a Mars year, which is two, two Earth years we have to collect the samples. And it may last longer. We can't count on it. But in the past, the missions have lasted longer, but that the goal is to accomplish all objectives within what's called the primary mission. And so, so two are for years. And then what, as for what the river will bring back, so the Rover will core, it'll put the samples in the sampling system has actually changed a little bit from what I showed you. So what it will do is it will put the samples each and sample tubes, and then collections of tubes will be stored together in a cache on the Martian surface. And then they would have to be retrieved by a later a later Rover and rocket combo. And if you're wondering, is this the most efficient way to do it? This is a legitimate debate, but it part of it is actually how our budgetary process works, because you can only get so expensive and still fit through the kind of long term planning that's required. If you want to spend $10 billion in one year, people are just going to shake their head at you. But if you can spend in increments over a long period of time, well then maybe something is doable. So the idea is that the sample return would be conducted by this Rover being the collector, by another Rover with basically very few instruments and only a rocket on its back. The rover itself would be light enough that it could land with a heavy rocket and still use the same type of system. And so that Rover would have an arm to basically grab those collection of tubes, stick them in the rocket and launch them up to space. And then either the rocket itself would come back to earth or there would be another canister to collect the sample and send it back. These things are hard to do remotely. So I know that one of the things, I was originally a geologist as well. And so I tell people that, you know, had I gone up there, I probably could have done the same thing that the rover's done in a fraction of the time. Right. So it's, you know, one of the, maybe by the time we are able to go retrieve the samples, maybe we'll have the ability to actually send humans to do a little bit more. Yeah, I agree with you about the efficiency of humans. And that's, that's one reason that even though it's the expense and frankly the risk that I think it's worth it. Because I think we are still the more effective explorers and will be for the next 50 years or so at least. But in terms of sample return, it's really just a choice to do it. It's a choice for NASA to say we're going to do it because the technologies have been developed. The rocket system technology has been developed. The fetch rover technology has been developed. I saw some cool video at a meeting in February of a rover like picking up these little tubes and sticking them in the devices. Really awesome. And then we have, we've been working on low propulsion. So it's really a matter of just saying go get them. And then two or three years later, we can do it. Yeah. Well, we've got a lot of really great questions, but we want to be productive of Dr. Elman's time. And so we're going to, you know, we're sorry that we weren't able to get to all the some of the really good questions. But that's all for tonight. So you've got to find this webinar along with many others on the night sky network website in the outreach resources section. Each webinars page also features additional resources and activities. And so Dr. Elman, do you mind sharing your slides with us so that we could post those? Sure, I'll be happy to send them your way. Fantastic. Thank you. And so we also post tonight's presentation on the night sky network YouTube page in the next few days. Now for our drawing day.