We spent a lot of time looking at pictures of Mars, and, and pictures are great. But there was one, I think, fundamental transformation in understanding the geology of Mars that came from, not pictures, but from figuring out the elevations, the altimetery. the, the topology of Mars. And we've talked a little bit about this when we were talking about some of the outflow channels. But I want to show you the entire global view of what Mars looks like in terms of elevation. First, how do you do it? Well, you take your spacecraft, it's flying around with the solar panels, and you zap the surface. Here's the surface here. [SOUND] You zap the surface with a laser. In fact, you'd zap it with a pulse of lasers. That pulse comes back and you time how long it takes each pulse to get to this bottom and come back. And that's it. You've made a very precise measurement of the distance between your spacecraft and the surface. Of course, you have to know very precisely the, where your spacecraft is when you're doing that and these are things that you can do pretty well with orbital mechanics. So you fly around Mars. Systematically shooting down the laser and mapping, marching along and mapping these elevations and. So this happened from the spacecraft called the Mars Observer. Mars Observer was the replacement for the Mars Global Surveyor which is the one, one of the ones that blew up as it got to Mars and this instrument, this laser instrument was called MOLA, Mars Observer Laser Altimeter. And it sounds like a very simple thing, and it sounds like, well, we probably knew the elevations more or less anyway. And I'm here to tell you, it is perhaps one of the most spectacular things that, that happened in the past decade, 15 years in, in studying Mars. When these maps first came out, you could sit in the audience of the presentations and listen to the jaws hitting the floor, because it was just such an amazing set of data to try to understand Mars. Rather then there's just try to tell you, let me show you. Here is Mars as I now think of it forever. I think of these colors, because this is the classic map that you always see. So these are elevations if you look very carefully up here in this corner you can see the highest things are whites, the lowest things are dark blues. Midland is these red ones. Where are the highest things, well we knew where the highest things were, remember when Mariner 9 went there and the only things that showed up above the dust storms were these three peaks in Olympus Mons, these volcanoes? Maybe this one too. These are the highest points on Mars. What are the lowest points? Well, it's not surprising that things like this big impact crater. This is the Hellas Basin that we talk about a lot. That it's pretty low, but the far north is also quite low. We'll talk a lot about that in a little bit. It's maybe not surprising that volcanoes are high, but it's not just that these are high volcanoes, this entire region in through here is quite high. This is called the Tharsis Bulge. It's quite an extensive pimple on the side of a planet. Everything is above the mean elevation. These reds are way up in here that are, that are higher. They're higher than most of these other regions in through here. What's going on? Just seeing this picture immediately tells you something about the, the history of Mars. And that, that history is that where these volcanoes are, and where these volcanic regions are, you have these, these big highlands. And that's because there were volcanoes there for billions of years probably. And those volcanoes didn't move. On the earth, we never see something like that. We see something like the, the classic version is the Hawaiian hot spots. Where you have a, a volcano, a, a hot spot coming out of the earth and creating a volcano. But the plate tectonics moves the plates on the surface of the earth along. And so the volcano even though it stays in the same place with respect to the interior of the earth, the volcano seems to march along the surface of the earth. So going from where it is now, the big island of Hawaii to where it was in the past, Maui, Oahu, Kauai, all those islands use to be the center of volcanism. Mars doesn't do that, these big volcanic regions look pretty set and it caused big bulges that are, that are visible in the topography, and that's because Mars has no plate tectonics. Why would Mars have no plate tectonics? Well, one good reason is that plate tectonics requires that you have these plates that are lubricated with water, if you don't have water, if all the water on the Earth dried up. The plate tectonics on the earth would stop also. There's no water on Mars, or no large quantities of water on Mars, and not surprisingly, no plate tectonics. I want to look at some of these other regions in, in detail, like these outflow channels, that we looked, talked about a little bit before. Let's look at those in much more magnification and there's a great way to do this. It's, it's fun just to look at this static map. But there, there's so much more information available. And you can play with it yourself. I want you to try this, because it's, it's you can just waste way too many hours on it. Go to this website jmars.mars.asu, Arizona State University, .edu/maps, and you will find yourself with a whole series of maps, but one of them being, one of the layers the maps being the MOLA color. If it comes out slightly different, then go to this thing and pick MOLA color and you'll get something like this. You might initially start out with it zoomed way out, and you see Mars repeated from spot to spot to spot. But zoom yourself in until you find something that you recognize. And again, you should now really start to recognize things, Tharsis Bulge right here Valles Marineris, outflow channels like crazy Hellas Basin, Northern Lowlands. And let's go look at some of these outflow channels in detail. These are the ones, right here, that we talked about before and tried to measure the widths of and measure the heights of, and now you can see that they're just part of it. They were coming from this region over here, but they're other outflow channels that are actually coming from the regions around Valles Marineris. Look at these things, look at the, the flow lines going all the way out through here. Look at the flow lines here. But that's not all. We can go zip in more. And really see these same sorts of features that we were talking about in the, the channeled scablands. These, these, these rounded mounds go out, maybe all the way out through here. You see these channels go all the way out through here until they finally sort of peter out, but maybe, maybe we even still see them out through here. And you know, there's more. You can always keep zooming in until you finally hit the limit of resolution. Somewhere around here it starts to get crummy. Why is the resolution not better than this is because you're not taking a picture of Mars at this point. You are doing these individual laser shots, and the laser beam itself spreads out as it goes down to Mars and it covers an area of a, of a certain size, and it comes back and you can't get better resolution than that without putting a telescope on your laser beam. I find these outflow channels to be just spectacular at the, at the MOLA topography. You could spend hours and hours looking around at Mars and that, I love the cracks that show up here in the Tharsis region and you can start to see that hey, Valles Marineris looks like the biggest crack in the world. In fact, it looks a lot like a big loaf of bread that has been expanding and expanding and that loaf of bread cracked open from too much expansion. Caused by these volcanoes over here. I want to now think about what's going on here in the North. These very blue regions up through here. Very blue. Meaning very low, compared to these, these are, these are now called the Southern Highlands. Because they're the old regions. Heavily cratered and much higher altitude then these regions here. Let's zoom in on some of these low regions and see what they look like. Let's try that crater looking region right there. And see how it looks. There's something really fascinating going on, first off, you see that it's not just lower. There's something else that's going on here. While one, we knew that this was Amazonian Period and so the numbers of craters is much smaller here than just right next door right here. So clearly a big difference going on here. But there's something else. Look at the, just the surfaces. Look at the surfaces here versus the surfaces here. You can tell just by eye that this region in through here is really very smooth compared to, say, this region in through here. And if you look around the entire Northern Planes, you see the smoothness everywhere. Let's look at right here, sort of well north of the outflow channels. You do have some mucky stuff here, maybe caused by some impact craters. But in general, look at this very smooth material in through here. How do we quantify that? Well, there's actually a great way of quantifying that, and that is by using a laser altimeter. Because of course not only does the laser reflect back and tell you how long it takes, but the laser can tell you how smooth the surface is. If you shine the laser at the surface, and it all comes back in one instant pulse then you know that that surface is very shiny. If it comes back all spread out that's because some if it's a little closer, some of it is a little further. You have a rough surface, so you can use MOLA not just to measure the, the elevations but you can measure the roughness. How do we do that? How, look at that. Well, we can actually just go to this layer tool, right here, and say MOLA Vertical Roughness, and I want you to watch very carefully as I turn this on. Pay attention to where the Northern Planes are and, and the, the Southern Highlands, and see what we get. It's not important to know what these colors are in, in detail but these greens, these dark greens mean very, very smooth. These surfaces, these surfaces that we know as the low blue regions are incredibly smooth on these scales. So what's going on? Hm, very low elevation, very smooth. Sure sounds like a region that could perhaps be a large, liquid-filled basin, in a, in a massive northern ocean. Is that a possibility? Some people really think so. There's a figure from a paper that came out soon after the MOLA data were acquired, showing that if you look at now, we're looking straight down at the North Pole. You didn't really get to see this region in the North Pole before. But one of the things to notice before we talk about the rest of it is this. This is the polar cap right through here, and the polar cap is a mound. It's small, but it's above quite nicely above the rest of this. And, we now know that it's a mound of water ice. But, the rest of it is this very flat region, this very smooth region that also is consistent with large massive shorelines. If you imagine taking a bucket of water and filling up the northern hemisphere here, these are the shorelines you would get depending on the volume of water that you have there. So if you don't have quite so much water, add some more water you get up through here. There's a nice correlation between these smooth regions and these, these potential shorelines that you can see through here. There are some indications that there are even features that look like they're shoreline features, like what we have on shores on, on, on the Earth where you have cliffs, wave eroded cliffs. Sometimes people think they see wave eroded cliffs along some of these shoreline features. Sometimes people go back and look with higher resolution images and those things don't look as much like shore eroded cliffs. So the, the evidence is still unclear on that, but it certainly looks like something like that could be what's going on through here. A more recent paper has attempted to do the same thing, but now not looking at just potential shorelines but looking at features that look like they might be deltas. Now if you remember we looked at one of these delta features earlier but that delta feature was not along the shoreline here, it was down in one of these craters. In fact it must be one of these two down in through here. And they went and mapped every thing that looked like a delta anywhere on the planet, and a lot of these are in crater regions where you might have had flow into these craters. But a lot of these are connected to potentially this big northern ocean, these red ones. These red ones are interestingly all at the same elevation. Now you can imagine if deltas were just some random occurrence that were coming because you had a little bit of a flow at one point, and then a little bit of a flow at another point. And maybe there was a stand of water somewhere, and stand of somewhere, else. That you would have random heights for all these deltas, but distributed fairly widely across this putative shoreline. These deltas are all essentially at the same height. That height is given right here with s, s for shoreline. These things are all oceans. These things are all land colors and you can see what the ocean would have looked like. Nice little island that you have through here, the white is the shoreline must be the the sandy seas of Mars. And you have these beautiful deltas that come in at these locations. In fact, these deltas that you see here. This region right here is very close to those outflow values we were seeing. And then we saw some of those flow features that looked sort of delta like. Is it true? It's hard to say. Looking at 4 billion year old deltas is a hard thing to do. Sometimes, geologists dispute each other when somebody says it's a delta. Somebody says it isn't. I'd like to show you some of these but they actually, you can't see them at the MOLA resolution so you have to actually look at the images of them and try to reinterpret what's going on. As with everything else I think I have to say that the jury is still out. In favor of the global northern ocean, a lot of these things. Deltas, the potential for shoreline smoothness of the surface. Volume of the water. The volume of the water is not dissimilar to the estimates of these outflow channels. And you know these outflow channels go into where there might be a northern ocean. And we calculated total volume. These outflows could fill up this big northern ocean. But these outflows, as you remember, were potentially sort of late in the history of Mars. They were perhaps hesperian and they were perhaps related to the rise of Tharsis here as it went up, heated up groundwater, things broke through, and had these massive outflows. So if this global ocean was here during the Hesperian, it doesn't explain the Noachian. I'm going to keep using those words, you're going to actually get used to them, Noachian is the oldest times. Noachian is where we see these evidence for the, perhaps this precipitation, the drainage systems that look like, that really look like they had to have been from precipitation. So if this is an Hesperian Ocean, still doesn't explain that. Maybe the ocean was there even before these outflow channels came in. Maybe they were earlier episodes of, of water flowing in through here. Once again, it's an intriguing enough possibility that we need to continue to explore and see if there's other evidence that we can find that shows that perhaps these were shore lines. That this was an ocean, and that, back at some point in the past of Mars it was warmer than now and wetter than now.
