I'll get some notes up for the Tuesday press briefing this evening. In the mean time, enjoy this cool picture of the IDD reachin' for Adirondack.
Since I haven't posted notes yet, here's a cool inverview with the creator of that great MER animation. I wonder what it would have been like if he hadn't had "tone down" certain shots. Thanks for the heads-up, Steve.
And here it is:
I missed the first few minutes of the briefing and the notes are short on clean-up and editing. Have fun :-)
Johannes Brueckner:
I'm going to talk about the Alpha Particle X-ray Spectrometer, developed in Germany at the Max Planc Institute, a small hand-held instrument that measures x-ray radiation emitted by the Martian samples. With this data we can derive the elemental composition of the Martian soil and rocks. Image shows the instrument with the doors open and there is the x-ray detector. This first diagram shows an X-ray spectrum. The horizontal axis shows energy of the x-rays. Vertical shows amount of x-rays per energy interval. As a result you get the spectrum, the spec count and the peaks. The position of the peaks is indicative of the elements in the sample. The largest peak comes from Silicon, a major rock and soil forming element. Second largest peak is from Iron. Height of the peaks is also indicative of the amount of concentration of the element. This helps our colleagues to get good Mossbauer spectra. First I'd like to indicate that next to silicon peak is three small peaks, for sulfur, chlorine and argon. Very indicative of Mars. Argon is noble gas and part of the Martian atmosphere. Sulfur and Chlorine are salt forming elements. Not surprised to see this amount of salt-forming elements because we have measured this from Viking, Pathfinder sites and on all these sites there is a lot of Chlorine and Sulfur in the soil. This tells a story about something which is a component everywhere, globally distributed on Mars. Something which is new you can see on the right side of the Iron peak, the Nickel and Copper and Zinc. This instrument is so sensitive that we can now detect Nickel and Zinc on the Martian surface for the first time. The Copper comes from the instrument itself. This is a very high-resolution x-ray detector, possible because of very good detector development in Germany. This sensitivity will help us measure even minor changes in the chemistry on all future soils and rocks we hope to measure. Looking forward to more measurements on Gusev.
Steve Squyres:
Multiple working hypotheses - a bunch of different ideas and we're trying to figure out which one's right. We have multiple hypotheses. Preliminary observations have revealed interesting things about this soil and posed new questions. First, we do not know that this soil came from Gusev crater. The basic pattern of elements is very similar to what's been seen at the Pathfinder and Viking sites. Mars has global dust storms. This stuff could have come from somewhere else. It will be very interesting to dig some holes or go where mother nature dug some holes, craters. There are a couple of surprises that we've got so far. When we first looked we saw fine-grained soil with a reddish cast to it. As we take a close look with Pancam we can see a spot of fairly pure soil where we put down the Microscopic Imager (and the APXS, Mossbauer and mini-TES were used there too) When we looked at this a couple of days ago we saw these grains, very fine grains in an aggregate, stuck together. What's sticking them together? We got a surprising answer. I was suspecting electrostatic forces, static cling. I thought the first time we pushed on it that it would all collapse. The Mossbauer Spectrometer has a contact plate that we pressed into the soil. After we pulled the Mossbauer away, we took another image. The collapse didn't happen. Before and after pictures, there's hardly any change. Nothing collapsed. These grains held together. What's holding these together? We don't know but I think a clue may be in Johannes' data. There may be sulfates and chlorides, salts that are glomming these things together. They may have been transported there by water or by volcanic process. We may have chemical glue. I want to find out how strong those things are. We can push harder with the Mossbauer. We can use the wheels. It's a pretty heavy vehicle. It's gonna flatten these grains. One puzzle we've got is what's holding these things together. One other puzzle posed by these measurements is the Olivine. Olivine is a silicate with Iron and Magnesium. The kind you find in igneous rocks. It's not something you form as the result of chemical weathering. One possibility is that this is simply ground up, finely ground up lava. That would be a surprise to me. Some on my team are so surprised by the Olivine that they believe what we're seeing is actually underneath the fluffy soil to the solid rock underneath this stuff. We can test this. We can scrape, we can dig with the wheels. We're starting to put together a comprehensive picture of what this stuff is. We have pulled up against a rock called Adirondack and as we speak Johannes' instrument is taking data on Adirondack. Right now as we're speaking the science team is trying do decide if they want to use the RAT on Adirondack. We have the tools to learn.
Jennifer Trosper:
Right now, it's about 5 PM Mars time on Sol 17 at the spacecraft. This data we're talking about here is hot off the craft. Today's objectives were to unstow the arm this morning and check out the RAT contact sensors. We placed the RAT against the rock to test the sensors and then pulled it away and took some Microscopic Imager pictures. Then we put the APXS on for a couple of hours and next we'll do an overnight with the Mossbauer. As steve said, we're preparing to RAT this rock tomorrow. The spacecraft is extremely healthy. We had a 99 megabits Odyssey UHF pass last night. Incredible amount of data flowing. Thermal situation, we are a little bit cooler now that we're off the lander and can stay awake a little bit longer to accomplish a little bit more science. Power situation looks good. We charge the batteries fully each day. We're really mostly constrained by the amount of data we can collect. We're feeling very good about the status.
Q. What depth did these instruments sense? Possible that trenching won't get down to "the prize" because of the depths.
Johannes: APXS penetration depth is very, very shallow. 10 micrometers. Only see the upper most surface.
Gostar Klingelhofer: For the Mossbauer we can see down to half a millimeter for dense objects or up to millimeters, even a centimeter for the fluffy stuff.
Steve: We have an enormous capability to sample depths from 10 microns to about 50 meters, with the wheels, we can drive to a crater.
Q. You mentioned chloride salts. One possibility that they were brought by water. What does that say about life?
Steve: It's way to early to say about that. We don't even know if the stuff originated in Gusev. We know there's water here, frozen under the surface. There's compelling evidence from pictures taken from orbit that water flowed on Mars. It takes no great leap of imagination to think of water in small quantities percolating through the soil and dissolving salts and then precipitating those out. But there are other ways to make those as well. Volcanos. Go to a volcano some time and take a sniff :) Here's a key point. If you look at that spectrum that Johannes pointed out. It's very sensitive, fantastically sensitive instrument so we can go from rock to rock, soil patch to soil patch, scratch below the surface, etc. If there are even very subtle differences we'll see them. We've got the tools to do this.
Q. Any place on Earth where soil resembles this?
Steve: Am I allowed to turn to the audience for that one? Dick Morris from the science team, are there places you've been that look like this?
Dick: many places in Hawaii that look just like this.
Ben Clark: Back when we got the mineral results from Viking, we went around challenging people to come up with an Earth sample that matched that. That was 30 years ago and no one's done it.
Dick: Well, the answer to that is that Earth has a lot of rain that washes that stuff into the ocean.
Q. Steve, why would you not use the RAT?
Steve: That decision hangs on engineering and vehicle safety considerations. I think Adirondack is so well suited geometrically that I don't think there are any safety issues. The other question is will you learn something more by using the RAT. Adirondack is incredibly smooth, polished by mother nature's rock abrasion tool. The meeting's going on right now. I think the guys are probably gonna decide to RAT this thing because there's really no way to know what's underneath. If we do RAT it and find that nothing's different underneath, that would be great because then we know she's not hiding anything from us and we can take surface measurements as we move around.
Johannes: Pancam closeup suggests weathering. With the APXS we'll see first 10 micrometers. I'm confident we'll see a difference inside.
Q. How do you take the data and tease out what compounds are there.
Johannes: APXS is just elemental composition. Mossbauer can tell the rest.
Gostar: Mossbauer measurements can be compared with terrestrial minerals and we can dig out the different mineral compositions.
Q. Any idea when you might start trenching?
Steve: Trenching comes in different flavor. Some simple, some sophisticated. I expect the first simple trenching activity to scratch the surface is going to come pretty soon. Reason is not only addressing science mysteries but also important to address some key engineering questions. If we intend to head out across the countryside, knowing in a lot more detail how these wheels interact with the soil will be very important. I'll bet you by sol 30 we will have done something like that.
Q. Some of your colleagues are vacating the idea that you're sitting on a lake bed? Where are you on that?
Steve: I believe that it is unavoidable that somewhere underneath our wheels are lake sediments. How far down? I don't know. Couple possibilities. One is that this stuff has been churned up so completely by impacts that whatever was there in terms of sedimentary layering is long gone. Another possibility is that the windblown and volcanic materials have buried the lake sediments. That's why we want to go to that crater. A 200 meter crater is gonna dig down 20, 30, 40, 50 meters. As we get closer and start to see the ejecta we're going to be getting deeper and deeper into what's underneath. I don't think there's any question that Gusev was once a lake. I also said that Mars wasn't going to give up her secrets very easily. That's why we're going to need the full capabilities that this vehicle has to offer.
(Tomorrow's briefing at 10 am PST. Images on the website.)
End of briefing.
Posted by asa at January 20, 2004 09:02 AM