Mars Up Close, Part 3: Ken Edgett

Ken Edgett: I've been with this project with the Rover since 2004 when we proposed the cameras that take all these beautiful color images. And...but my own story goes back to reading National Geographic in the early 1970s, and the coverage of the Mariner missions and the Voyager and Apollo. So, it's kinda trippy to be standing here right now

This is a landscape. Mount Sharp you see to the upper left rising out of the scene in that direction... in the other direction, you don't actually see it here, but we'll see it. You'll see the wall of Gale, off further in the distance. Mount Sharp is three miles high of layered sediment. The kinds of outcrops of rock that we've been looking at since we landed are more like ankle and knee high. And some of them are down underfoot like the mudstone that we drill.

By the way, two years ago when we landed, if you said the first thing we drilled was going to be a mudstone. And that, we would find that it was actually habitable environment, I wouldn't have believed you. So, this has been an amazing two years. You see, Curiosity carries its name on its arm, it carries its name on its sleeve. And...what we are doing, we are geologists for the most part, and what we are doing is, trying to read the history of this place in the layered rock. We call it stratigraphy.

So basically, the oldest rocks are at the bottom of the stack and the youngest are at the top, and so, if you go like, to the Grand Canyon in Arizona, for example or Letchworth, I've been there many times. Older... younger. So, what you see here behind me is one of these landscapes in a place called Dingo Gap. This was just a few months ago. In the far distance you actually see the north wall of Gale Crater. So, we are trying to look at these rocks with the rover and trying to understand the history that they are telling us about this place. Here's another place we call this one Shaler and this is layered rocks, laid down by moving water in a stream. All of that orange-brown stuff you see, that's the dust. The rocks is the dark grey stuff. Everything we've seen in Gale has been sedimentary rock and it's been various shades of grey.

Here's another landscape again in the direction we are driving. Here you can actually see the wall of Gale off in the far distance and you see a little bit of Mount Sharp off in this corner up here, in front of us, right in the foreground is a little drift of sand... windblown sand. What we've been dealing with here is a very, very thin veneer of windblown sand, windblown dust, and all those little pebbles and cobbles you see, that's just the detritus, as this rock breaks down and then wind carries it away.

This is a story of... we are right there by the bed rock, it is right under our feet, we can drive up to it, we can read this history, but we do have to deal with this veneer of dust and sand, and pebbles here and there. Wind erosion is a big deal in Gale in allowing us to do our jobs. And if you look in the sort of the bottom middle of this picture, you see a little pebble and behind it is a protrusion going back under the sand into the rock outcrop, or into the rock face. The little pebble and then this protrusion. That pebble protected all that rock behind it as wind blew sand and eroded that rock back except where that pebble was. That's like one of my favorite pictures from this mission. Now, here is a close up. Like I said sedimentary rock, so this is bits of old rock.

So, think about the history here. There was rock on Mars. That rock broke apart, made sand and pebbles and cobbles and dust. And then, that stuff was transported by wind or water and deposited in Gale. And then later, it becomes rock, okay, so sediment then becomes rock and then even later the wind is eroding that, leaving like that protrusion with the pebble. Okay. This is a picture of one of the conglomerates that we saw. This is a close up and you see a penny for scale, so you get some idea... these are actually very small pebbles, something about the size of Lincoln's head... that penny is also on Mars, but not actually in this photo, I photoshopped that in. To give you a sense of scale, but that-- the rover carries that penny with it and I love to use it for scale, because we are all familiar with that. That was a Conglomerate.

Now I'm going to go to a finer grain sediment, this is a sandstone. Okay? And what you are looking at is the sand is both, the very dark grey mass that you see everywhere. You can't actually see the individual grains because they are actually smaller than the camera was resolving here. And then you see little protrusions which are larger sand grains set in that finer sand. Those protrusions are there because of wind erosion, those are resisting the blasting by the sand, so they stick out. But then at the bottom you see a void, you see out of focus dirt in the background... because this is a layer, it's forming a shelf overhang and the layer beneath it retreated back out of view, you can't see it.

Now, everything you see in this picture that looks kind of brownish or reddish is just dust sitting on the rock. This rock is dark grey. Next slide shows the finest grain sedimentary rock we've seen which is this mudstone and the penny here is for scale again and you see an area that the rover brushed, it has a little wire brush. We don't use it often, but when we do it, it does a good job. Now, let's look at that close up. Okay? The camera on the arm can get right down literally within an inch or so and we can take these close up views. Here now, you actually see grooves cut into the rock by the brush. So, this rock is not really, really hard, it actually can get little grooves from the wire, as it, the wire brush as it moves. And you see some of the dust that is sort of generated as it swirls that up. But when we look at the rock itself, ignore the dust, ignore the groove, we find that the grains are too small to see... with this camera. And this is one of highest resolution images ever taken outside of a microscope, you know, on board the Phoenix Lander, this is one of the highest, right down there with this camera and we can't see the grains. So, they are very, very fine grains.

So, let me talk briefly about some of the other tools. You've seen a lot of pictures. You get a sense that we can do a lot with pictures. But we also want to know about the chemistry of the rocks and the minerals that make up the rocks. This is the arm, it's that the white thing sticking down and then the turret and the shadow underneath it, you see a little box, called the APXS. That is a science instrument that is using X-rays and it is measuring the chemistry of the rock there. So, that is one of our tools. Here now is another brushed spot. This was just at the end of April. This was a sandstone... and remember the penny in the brushed spot. So, it is like three, or four, five pennies across, but you see an array of dots going through that, those were formed by a laser beam, zapping the rock at each one of those spots. Multiple times, at each spot... okay? And then the instrument observes the light that comes off of that as it zaps it and it can tell you something about the chemistry of the rock that way.

Later in May, we actually drilled this rock. But here is our very first drill hole. The diameter is 16 millimeters. One-six millimeters, I don't know what is a millimeter. Well, a Roosevelt dime, a US dime is 17 millimeters. So, this is one millimeter smaller than a dime. This is the stuff that if you told me this was going to be first thing we drilled, you know, before we landed, I didn't even know that we would land, right? It...you see the grey mudstone there, you also see this white lightning bolt. That is... there was a crack in that rock at some point in its history and minerals filled that... sulphur and calcium bearing minerals filled that vein. Getting a picture like this allows us to get a sense of what did we actually drill through. Then that sample is put into instruments that are inside the rover's body. One to find out what the minerals are and one to find out what the chemistry is.

I just want to leave you with this because this is why we do this. It's really for understanding our home and so what you are seeing is the rim of Gale after sunset, and there's a bright dot in the sky. That's Earth. And if you look up at the little blow up, you actually see there are two dots. The bright one is Earth, the fainter one is the moon. You can see these from Mars. And we study this stuff to understand our home planet. Just as much, because of our curiosity. Thank you.