Introduction
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tonight I'm gonna talk to you a little bit about some of the work that I've been doing as well as many of my colleagues in terms of trying to figure
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out where water might actually be on Mars and the reason that we're so interested in this is that it's
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basically what nASA uses to explain why we need to be going to Mars so much the
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reason for this is that there's several different aspects of Mars that we're very very interested in of course the
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big thing is whether or not life has ever existed on Mars is it there today and we know at least for here on earth
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you do need to have water in order for life to actually survive so that's one of the big challenges they're trying to
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figure out where water might be and whether or not there might actually be life on Mars we're also very interested
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in the climate both the current climate as well as ancient climate and by the end of this evening I'll have told you
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about how we think that Mars has actually undergone quite a bit of climate change over time how we think
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that at one time it may have been very earth-like and with lots of water on the surface but that we don't actually have
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today and then we also have a little bit of the geologic history of the planet
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tied in with the role of water and then finally of course we want to go to Mars
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have had a lot of interest and going to Mars it's not just here in the US it's countries all over the world that want
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to go so if we don't go Russia and Europe and India and China are all interested in going in our place so but
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if we're gonna go and explore Mars obviously where you don't want to have to bring all the water with us from Earth out to there so we need to know
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where it is there today but at first glance you would look at this and say
Why are we looking for water on Mars
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why are we even trying to bother identifying where water might be on Mars because you know under the current
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climatic conditions it really can't be there first off Mars does have an atmosphere
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it's a very thin atmosphere composed primarily of carbon dioxide but as I
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said it's very thin and the way that we can actually kind of get a sense of how thin an atmosphere is is by looking at
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the atmospheric pressure on the surface so right now as you are sitting here Earth's gravity is pulling our
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atmosphere down on the top of your head and our atmosphere is putting a force on the top of your head if you take that
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force and you divide it by the surface area of your head that force divided by area is what we call pressure and so
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while you're sitting here right now at sea level the atmosphere of the earth is pushing down on the top of your head
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where the pressure of what we call 1-bar and so it turns out that in the case of
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Mars if you go to the surface of Mars the atmospheric pressure is about 1/100 that so it's a very very thin atmosphere
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not a whole lot of atmosphere above you to actually be pulled down on the top of your head to give you another sense of how little
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atmosphere this is here on earth if you wanted to go to an area where you have about 1/100 the atmospheric pressure at
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sea level you have to go about a hundred thousand feet up into the atmosphere I mean I flew in today and they said oh
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we're cruising a thirty four thousand foot elevation you know it's like okay I have to go like three times higher in
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order to get to what the surface pressure is on Mars but what this means is that if you go ahead and put liquid
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water on the surface of Mars today there's not enough atmosphere to hold it in the liquid form it immediately will
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boil away up into the atmosphere and become water vapor so part of the reason
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we don't have liquid water on the surface of Mars today is because of this very thin atmosphere it not enough atmospheric pressure
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in addition Mars is about one-and-a-half times as far from the Sun as the earth is so it's a lot colder there as well
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average temperatures about minus 82 degrees Fahrenheit and so of course if
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you have liquid water put that into that temperature what's going to happen to it going to turn to ice right so liquid
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water on Mars can't exist if you put liquid water there it either goes into vapor into the atmosphere or it turns
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into ice on the surface and so we can actually see this when we go ahead and
Water on Mars
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we look at Mars we do see that there are white clouds in the atmosphere here's a really nice image of a storm system up
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near the north polar cap you can kind of zero in on it the right there and that actually is water ice clouds that we're
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looking at and it probably actually produced some snow up there but again no liquid water in the meantime
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but the temperatures are again cold enough and the atmosphere is actually got a lot of water vapor in it such that
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in the early morning hours that water vapor can actually condense out in the form of clouds and so in the early
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morning hours right after the Sun rises a lot of times we can actually see fog in the low-lying areas of the planet and
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again those are water ice crystals that were actually looking at there and then we do have a lot of water ice clouds and
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the atmosphere as I mentioned and I absolutely love this picture because it was actually taken by a spacecraft that
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we had on the surface of the planet back in 1996 we had the Mars Pathfinder mission that landed on the surface and
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one morning NASA sent a signal and said wake up early we want you to take a
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picture of the morning star out there which is Earth and so the rover woke up and it took this picture and guess what
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it got clouded out I love that because that's always been my problem whenever
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I've tried to do ground-based observatory it clouded out that's why I went and turned to spacecraft image analysis instead but anyway yes there's
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a lot of water vapor in the atmosphere and we also do have some water ice that we can see very easily this is actually
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a series of three images that were taken by the Hubble Space Telescope in orbit around the Earth and they've been put
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together in kind of a mosaic we took the picture another picture another picture and then pulled them together to
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actually give us a picture of what would look like looking straight down on the north polar region so that's why there's
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some areas here where we don't have any images but it turns out the height of winter we have a really big polar cap
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that extends down to about Oh 60 degrees latitude in the in that Hemisphere and
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as time goes on it starts to shrink now the issue is that at the height of
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winter this polar cap that you're looking at here is actually carbon dioxide ice it is cold enough that part
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of the carbon dioxide in the atmosphere of Mars actually condenses down on the surface and creates an ice cap and that
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ice cap starts to go ahead and shrink over time so at the height of spring it looks something like this
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and then at the highest simmer we have this really small polar cap remaining and it turns out that the temperature at
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the north polar region at the height of summer is too warm for carbon dioxide ice but it turns out it's just right for
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water ice so we actually have suspected since about the 1970s that this is
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actually a water ice cap at the north polar region and we now actually have ordem orbiting spacecraft that are able
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to look at the composition of materials on the surface and they have told us
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that yes it turns out this is actually water ice so we do have water ice on the
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surface of the planet we have water vapor in the atmosphere and but when you go ahead and you add up
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you know how much water we have in those two reservoirs it's not very much and we
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actually think there should be a lot more water that actually has existed at
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Mars part of this is because Mars lies between Earth which we know is water
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rich and the outer solar system were pretty much all the moons are water ice so we would expect just by his position
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in the solar system that Mars should actually have quite a bit of water there but a better argument actually comes
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from our spacecraft missions and as I mentioned we have instruments on board several of these missions that can tell
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us about the surface composition and what we have found is that there are a lot of areas excuse me a lot of areas
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here highlighted in blue for example that are actually exposing hydrated
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minerals and these are minerals had actually formed in the presence of liquid water Wow
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we don't have liquid water there today but we see evidence especially in the ancient areas of Mars that there was a
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lot of liquid water there in the past to create these hydrated minerals this image down here is actually the location
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where one of our Rovers right now the opportunity Rover is actually busy exploring this area it's the rim of an
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ancient impact crater and it turns out that rim does actually expose some hydrated minerals shown in the greens
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and the Reds here in this in this picture so we're getting an idea that yes there actually was a lot of liquid
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water on the surface of Mars earlier in history but it's not there today we
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also see a lot of evidence from the geology I mean we see features here that hey those are channels they had to a
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form by some sort of fluid and when we look to see what kind of fluid would be the most likely that we would have at
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Mars it does turn out to be liquid water even though the atmosphere can't support it today and a lot of times these
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channels will come along and they'll cut the rim of an impact crater and then we look at the floor of this crater and
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it's nice and smooth where these channels actually cut into
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the root in to the rim of the crater right at this area we actually see features like this does that look
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familiar to anybody that's the Delta it's just like the Mississippi Delta
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where New Orleans is but this is a delta on Mars and we see these in several
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different locations also when we start looking at these smooth deposits on the floor they're not necessarily smooth all
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the way some areas are kind of eroded back and in those cases we actually see very fine layers
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looks like sedimentary deposits that were actually created and so what we
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propose is that there actually was liquid water flowing through this channel at one time it got into the
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floor of this crater it created a pond and the sediments from that water actually got deposited onto the floor
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eventually the water vaporized up in space but it left behind this evidence that there was actually
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liquid water in this crater at one time in the past and then we also have
Martian Meteorites
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evidence from Martian meteorites turns out that although we have not actually been able to bring back samples just yet
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of the Martian surface with our spacecraft missions Mother Nature has delivered samples to us as it is and
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that's in the form of Martian meteorites so these are rocks that got blasted off the surface of Mars
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millions to billions of years ago by impact events and it turns out some of
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them when you start looking deep inside of them actually contain globules of carbonates
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and carbonates her a mineral that basically forms when you've got liquid water and carbon dioxide interacting
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together and they precipitate out to give you carbonate and so the fact that we actually see carbonates within these
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meteorites tells us that okay there must have actually been liquid water interacting with that carbon dioxide
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rich atmosphere sometime in the past now at this point usually somebody raises
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her hand and goes how do we know those guys are from Mars and that's a good question they're not stamped made on
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Mars we'd probably be suspicious if they were but it turns out there's lots of
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kind of inferential evidence that suggests these guys are from Mars first
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off they're volcanic material so they have to come from volcanic Li active body they're also relatively young as
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meteorites go there on the order of about 180 to 1.3 180 million years to
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1.3 billion years so you had to have a body that was volcanically active as recently as 180 million years ago and
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that kind of rules out most bodies in the solar system it rules out asteroids things of that nature
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so we kind of were left with okay it could be Venus could be earth could be Mars turns out that there's oxygen
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that's trapped within these meteorites but it's not in the ratios of oxygen isotopes that we have here on the earth
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so we can rule out the earth and trying to get rocks off of Venus which is about
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the same size as the earth kind of tough Mars is about a third the size of the earth or half the size of the earth so
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it's easier to get rocks off of there plus if you knock a rock off of Venus it's gonna go inward towards the Sun
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with the big gravity Mars it will come inward but earth is in the way so we
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kind of suspect that these guys were from Mars and then in the 1980s scientists at Johnson Space Center in
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Houston actually discovered that there's glass within some of these meteorites and in that glass is actually trapped
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traces of an atmosphere and it turns out that atmosphere is exactly the same
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composition as the Martian atmosphere so that was really the clincher that yes these guys are from Mars
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so again these guys are telling us that hey we're from Mars and we're containing carbonates that came from Mars and
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therefore you know another good line of evidence that we actually did have liquid water on Mars in the past so back
Spirit and Opportunity
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in 2004 we decided to send two robotic geologists to the surface of Mars to
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actually check this out and these are two Rovers originally called the Mars Exploration Rover
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a-and Mars Exploration Rover B we decided those were too boring of names so we actually had a big nationwide
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competition to name these two Rovers and the winning entry actually came from a
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young girl in Phoenix who had been adopted from Russia and she said when I lived in the orphanage back in Russia
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and I looked to America as the land of spirit and opportunity and so these two
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Rovers became known as Spirit and Opportunity and they both landed on the surface of Mars in January of 2004 they
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were designed to last for 90 days opportunity is still going it is our
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little energizer bunny it refuses to give up but the whole purpose of these missions was to test all of these ideas
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that we have that yes it looks like there was liquid water on the surface of Mars at least early in its history and
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it's all this circumstantial evidence we have from geology and Martian meteorites and so forth now let's actually send
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missions out there to test the rocks close up and actually look for evidence of water and so they carried a whole
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suite of instruments to go ahead and actually you know go looking for this water so this is the landing site for
Spirit Landing Site
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spirit which landed on January 4th 2004 this is actually a topography map that
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you're looking at which is why it's all colorize but basically this is blue is low and white is high and I was actually
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involved we had a big community input to the actual landing site selection for
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these missions and I was involved with the team that actually proposed this particular landing site now when people
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think about us going to Mars and landing on Mars a lot of people kind of think oh we just put a map of Mars up on the wall
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and we throw a dart and that's where we go but it turns out is much more involved in that you know certainly
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there's a science that's driving all of it but then the engineers get involved and they're the real killjoys you know
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because we want to go explore these really exciting places and the engineers go that's too dangerous
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our missions gonna crash we're not going to be able to get any data back so they're the ones who are telling us well
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you got to go someplace that's low so the atmosphere is thick enough and we can slow things down with a parachute
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and oh by the way it's going to be really smooth because we don't like rocky stuff and of course the geologist won't go and explore rocks so you know
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there's this constant back-and-forth between the scientists and engineers but this is one of those locations where we
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see a channel coming in and cutting the rim of this ancient impact crater and the floor is really smooth and so we
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argued okay this looks like it was an ancient lake bed and it's low cuz it's
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inside a crater and it's smooth because it's an old lake bed and so the engineer said well okay you can go there and this
Spirit Landing View
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is the view from spirit after it landed so right after it landed it looked out and yeah it's nice and flat kind of what
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you expect to you know ain't you like that kind of look like it's all red because there's a lot of red dust on
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Mars so it coats everything but in the distance here a few miles away you can actually see this little range of hills
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and that range of hills became known as Columbia Hills because we lost the Columbia Space Shuttle on the astronauts
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right about this time so keep that in mind that it's a few miles away from the
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landing site but and it turns out that that's where spirit ended up by the end of its mission opportunity landed about
Opportunity Landing View
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two weeks after spirit it landed on the other side of the planet from spirit because there again the engineers said
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well they're going to be communicating with orbiting spacecraft and you can't have them in the same area otherwise they'll be talking to this you know
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spacecraft at the same time and we can't have that so this is in another area of the planet but it turns out that this
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area was selected because the information from orbiting spacecraft
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indicated that there is a huge deposit of hematite in this area hematite is an
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iron oxide here on earth it forms in the presence of liquid water so
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we basically selected the spirit landing site in a place called Gusev crater because it looked like from the geology
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that it was an ancient lake bed we selected opportunity's landing site in Meridiani Planum because of the
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chemical evidence suggesting that there had been liquid water there and this was our view from the landing site at
Opportunity Landing Rocks
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opportunity and as soon as this picture came down we all started jumping up and down going cool rocks okay we're a bunch
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of nerdy geologists we like our rocks but it turns out the reason we got so excited about these rocks is that these
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rocks are actually where they formed every place else we had ever landed on
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Mars rocks have been brought in by other processes either by impact or by floovio
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processes or what have you they had not actually formed in that area they were brought in from elsewhere and this it
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turned out we landed inside a very small crater and these are rocks exposed in
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the wall of that crater so here we can say these rocks formed here and if we
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can go and actually analyze those rocks and find out what in geologic environment was you know present at the
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time that they've formed that will tell us you know what was going on in this area so spirit lasted for quite a while
Volcanic Rocks
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and it went ahead roved around and started analyzing all these nice flat
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deposits that we thought were lake bed sediments and it turned out they were
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all volcanic okay yeah there is a little volcano off to the side that we looked
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at and kind of went yeah maybe there's something from that but yeah it looked too promising to be an old lake bed so
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we were kind of disappointed with that and and this slide here just kind of shows where the color points are some of
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the rocks that we analyzed and this is kind of a typical diagram that geologists use to figure out what kind
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of volcanic rocks we got and yeah they're definitely volcanic so what we decided to do is head off to the hills
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go off to Columbia Hills and see if maybe they were sticking up above the
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volcanic lava flow and could actually give us evidence of the ancient lake bed environment and so
Columbia Hills
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that's what happened spirit went up to Columbia Hills and lo and behold it started finding minerals that indicate
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it yes they did form in the presence of liquid water things like good tide and hematite and so forth and so we got a
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little more excited at that point but probably the most exciting thing that happened with spirit is that it's a
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rover with six wheels and the front wheel actually quit working and so what
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we ended up doing was driving spirit backwards most of the way and it would drag this front wheel along and as it
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did so that wheel would actually sink down into the soil here and when we look
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back we started seeing hey there's a lot of white stuff that's actually exposed you know by this dragging wheel and when
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we analyze that composition of that salty of that you know white material it turned out that it actually was salt and
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so again salt is something that you actually expect in an old lake bed I mean in Arizona where I live yeah we've
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got lots of dry lake beds and they're usually coated in this white stuff that's very salt rich and so we looked
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at this and we said yeah you know this is more consistent with our idea that this would actually be an ancient lake
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bed the downside is that this sandy stuff that we were able to drag the wheel through and you know show all this
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great salt also was what led to spirits demise turned out spirit got stuck in
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the sand one time and we couldn't get it out now the Gusev crater landing site is
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far enough south and it turns out spirit is powered by solar panels and so at the
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height of winter what we would do is we would find a nice slope that we you know a hillside that we could park on and
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point the solar panels towards the Sun to keep it alive during the winter well now we're stuck in a sand dune can't
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move it and so that winter spirit actually died it did not get enough energy we've tried several times since
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then to reestablish contact and know we just never have so if the spirit mission
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ended in March of 2010 but again the rock compositions and the salty exposures really do indicate that
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yes at Columbia Hills at least we have good evidence that yeah this actually was a lake bed with just the rest of the
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craters covered with the lava flow and in fact one of these white streaks that
Hot Springs
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we expose ended up having about a composition with 90% silica silica is
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silicon and oxygen and in Earth the only way to get such high concentrations of
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silica is actually in Hot Springs and so there is speculation that the center of
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this crater not only was water rich but there is still some heat left over from the impact and actually caused some hot
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spring activity to occur there and again we also found a lot of carbonates in the rocks here so again yeah you know it
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does look like eventually we did find our evidence of ancient water here on Mars ancient how ancient are we talking
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about probably about 3 to 3.4 billion years old quite a while back opportunity
Layered Rocks
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landed in that little crater we went over and explored those rocks that we've been so excited about and immediately we
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could see those rocks are actually layered and there are two ways that you can get layered rocks either in a water
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rich environment or a desert environment and so when we started analyzing the
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composition we started to find that hmm they're very very salt rich here and
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this is two different types of analyses the blue line or the red line is actually the surface of the rock but
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there's a lot of dust coating on these rocks and so we actually had a little grinding tool that we could grind away
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the surface dust and expose the inside of the rock and the blue lines actually show that and what we found is that the
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salt content went up as we went into the rock so it wasn't just some surficial deposit this was actually rock set
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formed in a salt rich environment and when we took a closer look at these rocks a lot of times we saw these little
Salt Rich Rocks
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depressions within the rocks this is what we call microscopic imager image
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and basically it's a magnifying glass but these little depressions that we see in the rocks are actually quite common
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here on the earth they're called bugs and what happens is that when you form a
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rock in a salt rich environment you get a salt crystal that actually forms in there and then over time water or just
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erosion in general causes the salt to dissolve or drop out and you're left
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with a little cast of where that salt crystal was and the rocks are just full of these things at the opportunity
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landing site so we're starting to look at this and say mmmm looks like maybe these rocks formed in a salt rich
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environment and then remember we chose the opportunity landing site because of
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the hematite signature the iron oxide and when we looked in the rocks we started seeing all these little round
Hematite concretions
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things they actually start nicknaming the row saying that these look like blueberries and a muffin and so they got
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to the the name of blueberries but it turns out these are where the hematite
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signature comes from these are what we refer to as concretions and again
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they're common here on the earth there's a really good exposure of them just north of where I live up on the Colorado
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Plateau and what happens is that as water percolates through like sandstone it'll
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actually pick up iron and when it gets out to the edge the water starts to evaporate and it leases iron oxide
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behind and it will form these little round spheres within the rocks and so
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again the evidence of the salt rich material the hematite concretions and
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then when we looked at the layering within the rocks a lot of times it was kind of curved which is indicative of
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ripples and so all of this came together and we went you know these rocks formed
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in a saltwater sea and you know it had to have been around for some period of
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time for these rocks to actually have formed in this way opportunity is now
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has now been out exploring lots of other craters the reason we like craters is I like to refer to craters as nature's
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drills because hey nature has provided us with a depression and of course we know from here on the earth that if you
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want to look further back in time you look further down right so it turns out
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that craters the depth of the crater of excavate the depth of excavation of the crater is proportional to its
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size so the bigger craters we can go to the further down they've actually excavated the further back in time
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they've actually exposed and so we have gone ahead and explored several other craters that were bigger than the one
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that we landed in and what we have found is that this area went back and forth
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between being very wet and very dry so we see evidence that there was a sea
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there at one time and then turned into a desert and then it went back to being water rich and then it went back to being a desert and we can actually read
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that in these different layers of the rocks that we see within these craters and so what we actually have found is
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that this saltwater sea existed in this area not for tens of years not for
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hundreds of years but probably thousands if not millions of years so it actually
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was a very long-lived water rich environment that we're looking at now again we're looking back
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at probably about three and a half billion years ago though you know it's not something that's been real recent
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but it does tell us that early Mars must have actually been very warm and very wet and therefore we must have had a
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different climate than what we have today where we can't have the liquid water on the surface we also have
Curiosity
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another Rover on Mars right now the Mars Science Laboratory also known as curiosity it landed back in 2012 and
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again we ended up going into a crater it's a very large crater called Gale Crater and the landing site was bad
28:26
right up there and the reason we chose this particular landing site for curiosity which is really looking for
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evidence of ancient water again is this big mound in the very center of this crater turns out that this mound the
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very bottom of it actually has minerals indicative of hydrated minerals so again
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we think the bottom part of the mound may have actually been in place in a lake bed environment the other parts of
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the mounds though are actually very dry they may have been in place by volcanic ash or something of that nature
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and so what we're aiming to do is to actually move up this mouth we've got a rover and we're trying to
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find a path up through this Mound so that we can actually see how the Mars climate has changed over time from a
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very water rich environment to the much colder and drier conditions that we have today but curiosity's been busy
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exploring the area since it landed and it turns out that we did plan near an alluvial fan which forms anytime you got
29:29
water coming along carrying sediment hits a slope and all that water spreads
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out and you get the nice kind of fan shape deposit at the base of this cliff so we did find evidence of you know
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conglomerates here basically we had stream beds going along here we also
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have seen mudstones we've detected clays again all of this stuff is telling us their hats have been fluid here you know
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and you know based on the composition it definitely was water and this is a view not too long ago a
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few months ago from curiosity looking up at this big mound in the center called Mount sharp and look at all those
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beautiful layers I know Chris has spent time in northern Arizona doesn't that
30:14
remind you of Painted Desert it just it looks so familiar to those of us who
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live in the desert Southwest we see things like this all over the place right now spirit here or excuse me
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curiosity has moved past this little dark area here which is actually sand dunes and it's now over here and it's
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actually starting to make a climb up this central mountain so stay tuned over the next few months hopefully we're
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gonna be seeing some really interesting results coming out from the analysis of these rocks okay so to kind of summarize
Summary
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where we're at right now we have really strong evidence from opportunity that there was a saltwater sea in the area
30:52
where it landed at Gusev crater with spirit evidence wasn't quite as strong
30:58
initially but yes it turns out that Columbia Hills is actually full of sediments as well curiosity already is
31:04
showing us that yes there was a lot of liquid water early in Martian history and so when we combined all of this
31:11
evidence from the Rovers that we have on the surface together with our orbiting spacecraft that show us the rest of the
31:18
geology of the planet tell us something about the atmosphere the atmosphere is thin today but there's evidence that it must have been thicker
31:24
in the past coming out of one of our missions called maven and then also the meteorite evidence all of this is
31:31
telling us yeah there was actually a lot of water early on the mark early on in
31:36
the Martian history and in fact in the 1990s we had some scientists who said
31:42
wasn't just early in Martian history maybe we have something much more recently - maybe something within the
31:48
last Oh a few hundred million years or last billion years which again I know if you're not a geologist so sound like
31:55
really long time periods I often have my students asking when did a million years
32:01
end up not being a long time period - it's like when you take enough geology classes it just kind of sinks in after a
32:08
while but again you know when you consider that Mars is four-and-a-half billion years old the age of the solar
32:13
system and the water that we've been looking at thus far has been about three and a half to four billion years old
32:20
having something that's a billion years old or a few hundred million years old that's recent and this is during a time
32:28
period when we thought that the Martian atmosphere had already thinned and we basically had climatic conditions like
32:34
we have today but in the 1990s we started to see a lot of evidence that
32:39
there may have actually been a lot of liquid water in the Northern Plains
32:44
probably a big ocean of some sort and again this is something that would have been geologically recent compared to
32:51
that earlier time period that we're seeing all the evidence from the rover's for it
32:57
we also do know that the northern plains are much lower than the Southern Highlands so yeah we do see channels
33:03
that are flowing out and you know dumping their load out here in the northern plains so if there is water in
33:10
those channels yeah it could have gone ahead and and produced water out in the northern plains and then the other thing
33:15
we know is something to do with the actual roughness of the surface this is
33:21
a roughness map of Mars and the lighter colors are rougher the smoother colors
33:26
are or the darker colors are smoother again you can see that the Northern
33:32
Hemisphere is much much smoother than the southern hemisphere when we compare
33:38
with places on the earth trying to figure out ok what kind of environment can produce a surface that is that
33:45
smooth that we see on Mars the only place that we see something comparable
33:50
is on the ocean floors where you've had the sediments being deposited in that
33:56
ocean environment so all of this was actually put forth as an argument that we may have actually had big oceans on
34:03
the surface of Mars in relatively recent times but again this is during the time period when we would expect that the
34:09
atmosphere had arethe int so how can we have that much liquid water surviving on
34:14
the surface of Mars under the current climatic conditions well it turns out that even though Mars
34:22
you know went through a major period of climate change probably about 3 and 1/2 billion years ago turns out it can go
34:28
through kind of moderate stages of climate change even today and this is actually due to the influence of Jupiter
34:35
Jupiter of course is a huge planet it is 11 times the size of the earth very very
34:40
massive has a lot of gravity and Mars lies between Earth and Jupiter so out
34:45
where Mars is it actually feels a little bit more of Jupiter's gravity over time then earth does although we feel some of
34:52
it - and what Jupiter's gravity actually does is it affects the orbit of Mars and
34:59
also the amount of tilt of its rotation axis so this these are some diagrams
35:04
that actually show as a function of time how things like the ellipticity of the
35:10
orbit what we call the eccentricity how much that you know tilt of the orbit how those have changed over time because of
35:17
Jupiter's gravity but we also have the tilt of the rotation axis anybody know
35:23
what the tilt of the Earth's rotation axis is it's about 23 and 1/2 degrees
35:30
exactly and that causes what seasons so
35:35
it turns out that today Mars also has a tilt and it's about 25 degrees so pretty
35:41
similar to what the earth tilt is and so Mars does experience four seasons just like the earth spring summer fall
35:47
and winter they're about twice as long on Mars because Mars as year is about twice as long as the earth but we do
35:52
have those four seasons but it turns out that because of this gravitational influence from Jupiter that tilt
36:00
actually ranges quite considerably as little as fifteen degrees so the
36:05
rotation axis is almost perpendicular all the way to about 80 degrees where
36:10
the poles are basically pointing towards the Sun and now there's a lot of ice at
36:15
the polar regions I showed you that before it's in the form of water ice and it's also carbon dioxide ice you point
36:21
the poles towards the Sun they're gonna get more sunlight right they're gonna warm up guess what happens to all that
36:28
ice vaporizes into the atmosphere and all of a sudden you've got a much
36:33
thicker atmosphere the other thing is both carbon dioxide and water are really
36:38
good greenhouse gases they like to warm up the surface so they'll trap the heat next to the surface so we could go ahead
36:46
and actually get a warmer surface and a lot of people have argued you know we could go ahead and have rainfall we
36:52
could have liquid water on the surface got a thicker atmosphere for a few million years could go ahead and get
36:57
these types of situations and then the atmospheric scientists come in you know
37:03
stamp on our dreams all their atmospheric models suggest that you know
37:09
even with the poles pointed you know 80 degrees that tilt being 80 degrees poles pointed towards the Sun it's still not
37:16
gonna get warm enough for us to actually have liquid water and oceans anywhere but it will actually cause snow and we
37:24
can go ahead and actually get glaciers and guess what we see features like this guy that it turns out this is actually
37:31
dust covered ice on the edge of an impact crater that is flowing down and
37:37
into this material which is flowing down into the center of the crater and this actually is kind of support and
37:44
supported by the mineralogy because it turns out that in a lot of these places we have minerals like olivine which it
37:51
turns out olivine breaks down really fast in the presence of liquid water so
37:56
the mineralogy also suggests that it's probably mainly snow that we're actually dealing with here so right now there's
38:04
actually a big debate in the community going on there are those of us who do
38:09
believe that ancient Mars is very wet we like the geologic evidence we see the mineralogical evidence the rover's you
38:16
know everything we think points to the fact that ancient Mars had a thicker atmosphere it was very wet and then it
38:22
gradually became dry as we lost the atmosphere and it became very thin
38:27
others have argued that Mars has always been dry once in a while things might
38:33
change a little bit and you get you know wet episodes and that's what gives rise to all the geologic activity without we
38:39
saw but mostly it's been dry and then some people actually think that Mars was
38:46
really cold early on and all the water that was there was ice and the entire planet was a big snowball so like I said
38:53
this is an area big debate right now we even you know I was just at a conference in Houston a couple weeks ago or a big
38:59
spring conference and everyone's going back and forth on this personally like I said I like this idea I think the
39:05
evidence is really strong that we had to have had a lot of liquid water and it had to have been around for a long
39:11
period of time on the surface of the planet at least early on so then the
39:17
quote paste the question well where did all this water go if we had so much of it to begin with
39:22
well again Mars is about half the size of the earth and that means that it has a lower gravity turns out that the
39:29
gravity is about 1/3 of the gravitational pull here on the earth so it turns out some of that atmosphere is
39:35
just naturally be lost to space and again we have this mission called maven in orbit around Mars it actually is
39:42
measuring how rapidly the atmosphere is escaping to space and when they extrapolate backwards they find yeah
39:48
there was a much thicker atmosphere in you know the first billion years or so of Martian history and that a lot of
39:55
that atmosphere is simply escaped to space but it turns out that we do think
40:00
that a lot of the water that we had on the surface in the past is actually still there it just infiltrated into the
40:07
near surface region and it's in the substrate and there is a
40:12
possibility that we see some of this seeping out every so often if you take a
40:18
look at this image you see these little white streaks here it turns out these are areas that have changed in just a
40:24
few years time period those white streaks were not there previously and this is all highly gully this is again
40:31
the edge of an impact crater and you can see it's really gully and we have actually proposed that there may be
40:37
groundwater seeping out to go ahead and give rise to these gullies and it could be salt rich and maybe that white stuff
40:44
that you're seeing there is actually salt left over after the water has evaporated others have argued that this
40:51
is just simply you know avalanches cars by carbon dioxide snow and so forth
40:57
again a lot of debate but there is some evidence that yeah there may actually be some liquid water involved here probably
41:05
the best evidence for liquid water on the surface of Mars today comes from these recurring slope lineae RSL s and
41:11
these are dark narrow lines that we see on the surface of the planet that change
41:16
every so often for example here you can see one image and here's the image of
41:22
the same area and okay this guy is that guy and this guy is down here but lo and
41:28
behold hey there's a new dark area these guys come in the spring and last through
41:35
the summer and then they disappear in the fall in the winter and they come back in the spring in the summer and so
41:40
the idea is that we've got some groundwater that when it gets warm enough it can actually seep out you know
41:48
through the surface and create these dark streaks and then in the fall in the winter when it gets cold enough that liquid water freezes and we don't get
41:55
these things actually for me again we do have spectroscopic evidence here and it
42:00
turns out that it is consistent with this actually being briny liquids so that would lower the the freezing
42:06
temperature as well and help make these things possible we also have some
Neutrons
42:11
evidence of where the water underground might actually be especially the ice and that comes from a gamma ray spectrometer
42:18
that's on the Mars Odyssey mission in orbit around the planet and then the gamma ray spectrometer work well
42:24
actually this is neutrons that we're looking at turns out that you guys have
42:29
high-energy particles coming in from space what we call cosmic rays that come from the Sun that come from our galaxy
42:35
and they can hit the surface and when they do they act can actually knock
42:41
atoms off of the minerals in the surface and it turns out that as you go ahead
42:48
and you you know have these high-energy particles coming in they're knocking um atom soft but they're also knocking
42:54
neutrons off of these atoms and the neutrons can actually travel through the near surface region depending on the
43:02
composition of the surface those neutrons could get absorbed or the neutrons can just pass right on through
43:07
it turns out that hydrogen really likes to absorb these neutrons and in the
43:14
inner solar system hydrogen tends to be bound up with oxygen in the form of water so when we look at a neutron map
Water Abundance Map
43:22
of Mars we can translate that into a water abundance map and that's what
43:27
you're seeing here the blue and purple areas are areas of high water
43:32
concentration and not a big surprise that the polar regions are pretty high in water but what is interesting is that
43:39
there are a few areas here in the equatorial region that seem to have high water concentrations this is a surprise
43:47
because these areas get enough sunlight they should be warm enough that we wouldn't have any ice actually there so
43:53
there is some discussion that a lot of this could actually be hydrated minerals from the distant past that we're still
43:59
picking up we're picking up that water that's contained within the minerals but interestingly your opportunity landed
44:07
right about there and spirit landed about there and curiosity is right about
44:13
there all in these areas of high water concentration and we have actually found
44:18
from those Rovers that yes there is a lot of evidence that water was in those areas but the issue here is that this
Impact Craters
44:25
neutron spectrometer can only see down to the upper meter about a yard into the
44:30
soil and we'd like to know what's deeper so that's where my research comes
44:36
play I study these impact craters and as I said they create these nice holes in the ground but what I really like about
44:43
impact craters that they can expose what is buried underneath you go ahead and
44:49
you have stuff tossed out creating what we call an ejecta blanket and on the moon you get a very radial pattern here
44:56
surrounding these craters but here on Mars it kind of looks like you took a rock and threw it into a mud puddle
45:02
it's a very fluid ice type of ejecta blanket and we believe that this is actually due to the fact that you're
45:08
impacting into ice a very ice rich surface you go ahead and vaporize some
45:14
of that is you fluidized some of that ice and you go ahead and actually create this fluid ice pattern so this is the
45:22
only equations I'm going to show as I mentioned it is a case we'll have a quiz at the end that the depth of excavation
45:29
as I mentioned is related to the actual size of the crater it's about 1/10 and so we can use that relationship and then
45:36
we have to do a little bit more magic because some craters are big enough they kind of collapsed a little bit but
45:41
basically we can go ahead and use these relationships to figure out how deep the crater is actually excavating and the
45:49
ejected material like that fluidized ejecta play deposit that I just showed you that actually only comes from about
45:55
the top third of the crater depth and so we can go ahead and do these types of
46:00
calculations and figure out okay what size range do we have for these different you know fluidized
46:07
morphologies figure out the depths that they're excavating to and how deep down
46:12
the ejecta is coming from and what we find is that this is a cross-section of
46:19
the planet basically North Pole equator South Pole and this is where we think
46:24
the ice actually is so in this area where it's dark ice is there all year
46:30
round no no no two ways about it this area if there's water present it would
46:36
always be in the form of ice and then down here it's actually warm enough from the heat on the inside of the planet
46:42
that it would actually be liquid water turns out that some of our craters
46:47
single layer and double layer are into this area and our multiple layer craters are actually excavating down to
46:54
here so we actually think that the appearance of the ejecta deposit may
46:59
actually be telling us something about whether or not we're excavating into ice versus actual liquid and so we can go
47:06
ahead and use that to start to get some idea in terms of where ice is where liquid is and again like I said at the
47:12
beginning we want some humans there someday this gives us a way to actually start to estimate how deep down we'd
47:18
have to drill to get to water resources that could support future colonies we
47:25
also do have some radar on orbiting missions and they can give us more direct information about where water
47:31
might actually be we do have two of these raid arms one is called Marcy's on the European Space Agency's Mars Express
47:37
mission and then we have sherrard on the Mars Reconnaissance Orbiter mission which is a NASA mission
47:43
Martha's seas down deeper this is actually looking over the polar cap and you can actually see a split in the
47:50
signal here which is telling you about the thickness of the polar cap and this is all ice that we're actually dealing
47:56
with here Sherrard doesn't see as deep but it gives you a lot more detail you can see lots of little layers here over
48:02
the polar cap and so again we can start to get some idea in terms of how much ice might actually be there and it's not
48:10
just the polar regions this is an area in the kind of just north of the equator where we see a lot of those glacier like
48:16
deposits and it turns out yeah sure artists telling us these are ice rich as well from the last high tilt period and
Phoenix
48:25
then we did have a mission called Phoenix that landed about 68 degrees north latitude several years back this
48:33
mission was actually run out of the University of Arizona which is in Tucson not Phoenix you can imagine there is a
48:40
lot of you know nagging going on from their counterparts up in Phoenix you
48:45
know you've got this great mission and you called it after us but no it turned out that we actually had a mission in
48:51
2001 that went to Mars and unfortunately it crashed before we could get any
48:57
information from this mission was the exact same design but we made sure that
49:02
we fixed the problems you know so it wouldn't crash as well so it was named Phoenix because it was like the phoenix bird
49:09
rising from the ashes and what it did was to land far enough north that we
49:15
looked at and we saw this kind of hilly terrain turns out that's what we call polygonal terrain it comes from
49:21
freeze-thaw type cycles of ice when we dug down into the near surface region we
49:27
saw this white stuff here and we went cool that could be ice or it could be salt we don't know so what do we do we
49:35
wait for a few days let the sunshine shine on it and if it's ice it's gonna disappear if it's salt it won't and
49:42
after a few days it disappeared and we went ah ha it's ice and we actually were
49:48
able to scoop a little bit of it up and put it into instruments on board that tests at the composition it turns out it
49:55
is water ice pure water ice so we have actually tasted water ice on the surface
50:01
of Mars now and we saw the same type of thing underneath the spacecraft the Rockets that slowed the spacecraft down
50:08
as it was coming down actually blew away some of the dust and you can see big chunks of ice down there too so we do
50:14
know that ice is up there at near the polar regions and another way is looking at new craters craters that have just
50:20
formed in the last few years when they first form a lot of times they actually
50:25
have this little white deposit around them and again over the time span of a few weeks to months that white spot
50:31
disappears so we are exposing ice and so that allows us to get some idea in terms
50:37
of what latitude range we can actually go down to and still have ice basically
50:42
right at the surface of Mars so again these are all things that we're going to be interested in as we get to the point
50:49
of saying we want to send humans to Mars where is that ice that we can go to pull it up and actually melt it and drink it
Mars 2020
50:55
so my message here is to stay tuned we've got another mission going to Mars in 2020 right now given the inventive
51:02
name of Mars 2020 I imagine we'll have a competition to get a good name for it at some point but
51:08
these are the final three landing sites that are being discussed right now and over the next year or so they're going
51:15
to zero in one of these jezero crater is actually one of these Delta deposits again this
51:21
is color enhanced to kind of show different types of minerals but again it's got a lot of hydrated minerals you
51:28
know it certainly looks like an old delta deposit syrtis major again has a
51:33
mineralogy indicating that this was a very water rich area at one time and then long behold the third landing site
51:40
is Columbia Hills back where Spirit had gone to and again the goal of Mars 2020
51:46
mission is to actually go ahead and look for evidence of ancient climate but this mission is actually going to pick up
51:52
soil and rock samples storm on board and then some future mission will actually
51:58
go to that rover retrieve those samples and bring them back to earth for
52:04
analysis so at that point we will finally be able to get these into our terrestrial labs and really analyze them
52:11
and hope to get much better information about the timing of the water as well as how much water was probably there so in
Conclusion
52:18
summary hopefully by now I've convinced you there's lots of evidence that yes even though Mars today is very cold and
52:24
very dry that it was a very water rich planet in the past that there's a lot of
52:29
water there was in the liquid state early on it's mainly in the ice state at this point but lots and lots of evidence
52:36
that yes it was there maybe not doesn't look like this recently this is an
52:42
artist concept of what one of these ancient lake beds probably looked like but again the combined geologic evidence
52:48
the spacecraft data all of it points to a much better understanding of where the volatile reservoirs are today and again
52:55
understanding this gives us some sense in terms of you know investigating the
53:01
issue of life whether or not it's still there or was there in the past gives us information about the location of
53:07
resources for future human settlements and the other thing that I like to come back to when we look at Mars and we see
53:14
that you know okay it has to have gone through these periods of climate change what this does is it helps us better
53:20
understand what are some of the natural cycles that give rise to climate change you know how much climate change can you
53:26
expect and then we can compare that with what we see here on the earth to get a better sense of how much
53:32
human involvement is contributing to climate change here