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Mission to Mars' north poloar region Phoenix Mars Lander
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  Audio Recording of Phoenix Media Telecon for June 2, 2008 June 2, 2008
 


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Female Voice:              Thank you for standing by. This conference is being recorded. If you have any objections, you may disconnect at this time. I will now turn the call over to the Dr -- Jet Propulsion Laboratory. You may begin.

Jane Platt:                     Thank you very much. Uh, good morning at least here on the West Coast and in Arizona. I'm Jane Platt with the Media Relations Office at NASA's Jet Propulsion Laboratory in Pasadena, California. We will be joined momentarily by the University of Arizona in Tucson. During this media telecon, you'll get the latest news about the Phoenix Mars Lander.

                                    Our panel will give brief presentations, and then we'll take questions from reporters. And, as you're listening to the panelists, if you realize you'd like to ask a question, please press *1, so our operator can put you in the queue. And, we're going to try to have each speaker identify himself every time he speaks.

                                    But, right now, I'd like to turn things over to Sara Hammond, with the Public Affairs Office at the University of Arizona. And, she will, in turn, introduce the panel. Sara?

Sara Hammond:            Thank you, Jane. Uh, before we get started, we do have images up today. If you go to the Phoenix Web page under Gallery, on the left side, there's [fall '08] under recent press release images. And, we have four images up there that our speakers will be addressing this morning.

                                    Joining us on our panel is Peter Smith, the principal investigator of the Phoenix mission from the University of Arizona. Ray Arvidson, and his surname is spelled A-R-V-I-D-S-O-N. He's the co-investigator for the robotic arm from Washington University in St. Louis. And, Pat Woida, that's spelled W-O-I-D-A, senior engineer for the Phoenix mission from the University of Arizona. Peter?

Peter Smith:                  Yes. Five years ago, when we started this mission, that -- I was somewhat worried that we didn't have any wheels. And, we were going to have to accept whatever was in the reach of an eight-foot arm. And, that would be our entire interaction with the surface. And, so it's been a thrill for me this first week, after landing in the-the permafrost region in the northern arctic on Mars, to find out that we're in a really great place for doing the science we plan to do.

                                    And, first, we looked at the scene around us, uh, at the beginning of the week. We saw the-the polygonal structures and the-the [hummix] and the troughs that-that make up an arctic type of region, uh, that's very familiar to us on the Earth, both in the Arctic and the Antarctic. And, so, that's really a clue that there's ice under the surface.

                                    But, in getting our first pictures with the robotic arm camera underneath the Lander, and these have been shown in the last few days, we see a very kind of flat, bright surface that looks for all the world like ice. And, uh, many of us have trouble understanding how rock could form polygons and [hummix] and troughs like we see. So, it's very likely ice.

                                    And, uh, now today, we can report our first interactions with the surface itself, uh, and pictures of the surface soils. And, uh, Ray and Pat will be discussing that. But, we have even more good news. There was a-a bit of a scare a couple of days ago with our primary instrument, TEGA, which has eight ovens and a, uh, sort of an electronic nose called a mass spectrometer, that the mass spectrometer had a problem with one of its filaments. It appeared shorted.

                                    And, so the team has been in-in a furious recovery mode ever since the time they learned about this. And, last night, we had our first return with a p -- a-an attempt to switch filaments. We actually have two filaments in the ionization chamber. And, using, uh, the backup filament as the primary, turns out it was very successful.

                                    And, we now know that, even though it wasn't intended to be used this way, that we have the same sensitivity that we expected to have with the-the original filament that appears shorted. And, so that's really good news for us. And, in addition, the TEGA instrument was able to remove its covers successfully. And, I think they're not quite done with that process.

                                    There will be a few more minutes of retracting covers. And, then, uh, TEGA's ready to go with its science and, uh, perform the kind of, uh, uh, analysis of soils that we intended to do all along. So that's really good news. Uh, the -- we're still getting weather reports every day. And, uh, we are really focusing today, at this press conference, on the interaction of the arm with the soil and our plans for, uh -- our strategies for digging, getting samples and starting our-our science experiments.

                                    So, I'm so happy we have a science laboratory not only in the polar region, but next to things that look to be very interesting and just the kind of, uh, terrain that we hope to be able to analyze. And, to discuss our-our digging strategies and what we've done so far, uh, Ray can-can you tell us?

Ray Arvidson:               Yeah. Thanks, Peter. Let me get you up to date in-in terms of our excavation. And, just for background, remember, we saw with the robotic arm camera, this neat area called Snow Queen. And, then, looking under the deck, there is the-the two light-toned areas, uh, that we were so excited about. We called it Holy Cow.

                                    Uh, so we're-we're doing further imaging of Holy Cow on the current plan that's-that's being implemented on Sol 8. But, last night, we had also some pretty good excitement getting the Sol down -- Sol 7 downlink, uh, on the Earth and looking at the data. So we're in the midst of the digging strategy. So, uh, over the weekend, we had the robotic arm touch the surface and make a dent.

                                    And, that area was called Yeti because it kind of looked like a footprint. And, that was a validation of the ability of the robotic arm to go to a particular place on the surface. And, on Sol 7, the downlink, uh, showed our first dig. And, that was a test in which we excavated material just above Yeti and then dumped it to the left in an area that we can't dig.

                                    And, the-the data set is very, very exciting -- and Pat's going to talk about it in a minute -- in that the soil is crumbly. And, there is some light-toned bits. And, there are also some light-toned bits that are in the trench, the little, uh, uh, dent that was -- that was left after we-we acquired the sample. What we'll be doing over the next several Sols is evaluating, uh, where to go next in terms of digging.

                                    And, it's likely that we'll do three samples very close together at the surface and very close together to the-the test dig. And, the reason is, we want to get samples in the TEGA and then into the MECA optical microscopy lab and the MECA wet chemistry lab, all from roughly the same area and the same depth. So, we'll have a-a data set that can be inter-compared.

                                    And, we'll, in particular, want to see whether or not the-the kind of white, chunky bits that are exposed in the initial dig and also we saw in the scoop, in fact are-are icy materials. Or are they some salts, like a magnesium sulfate that we saw at the, uh, two Viking sites and that we saw at the Spirit site and Gusev Crater. But, let me turn it over to Pat to tell you a little bit more detail about these really interesting images that came down last night.

Sara Hammond:            This is Sara Hammond again. Before we go to Pat, I wanted to repeat where the images can be seen. On the Phoenix, uh, Web site, phoenix.lpl.arizona.edu. Under the gallery tab, there is a list of recent press releases, and we're on the Sol 8 images. Thanks. Pat?

Pat Woida:                   Well, our adventures in Wonderland continue here. Uh, if you've got the pictures, the first one to the left shows a-a, kind of a big view above Yeti of where we've done our dig. We brought the scoop down to the surface, pointed it into the surface and filled it up with material. Uh, the second image is a very nice picture taken inside the scoop with the robotic arm camera.

                                    Now, that's the camera that has its own three-light system, a red, green and blue light, so we can produce these nice, color images. And, of course, as soon as we made that nice color image, we-we got very excited because we see this nice streak of white material. It's running about a quarter of the way from the edge on the right side of the scoop.

                                    Uh, we don't know what this material is yet until we get a chance to analyze it, whether it be a-a part of the same thing we're seeing in Snow Queen or whether it's a salt or something new. If you take a look at the, uh, next trench image -- now, remember, that trench is the same width as the, uh, scoop is. And, if you look closely on the black and white image, the gray scale one, you'll see that, along the same place that we see it in the scoop, we have a nice trail of a white material at the deepest part of the -- uh, of the scoop.

                                    So that's [there]. And, that's -- the last image is, of course, if you've got your red and green glasses, gives you a 3-D image of what you're looking at. So we have a white material. At first, you wonder, when it's in the scoop, if it's just a reflection. And, uh, at this point, we're pretty convinced it isn't. We have a high confidence because we see in the same place this white material just at the very deepest part of this first dig on the surface. I'm going to turn it back to --

Jane Platt:                     Okay. Well, uh, thank you very much to our panelists. And, thank you, Sara. Uh, we're going to get ready to take questions from reporters. Now, if you do have a question, please press *1, and tell the operator your name and your affiliation. And, I do want to remind our panelists that if, uh, you do get a question -- sometimes, it will be directed specifically towards you.

                                    But, if not and you want to jump in, just please identify yourself. Say this is Ray or Peter or-or Pat. That really helps people follow along. All right. Let's take our, uh, first question from Alan Fischer at the Tucson Citizen newspaper. Go ahead, Alan.

Alan Fischer:                Hello. This question, I believe, is for Peter. Uh, you mentioned the good news about-about the, uh, TEGA Instrument, Peter. Does that mean that this -- the first, uh, samples from the scoop will now be going to TEGA? Or will they be still going to the, uh, optical instrument?

Peter Smith:                  Uh, our original plan was to give the first sample to TEGA. We were thinking of an alternative to the optical microscope when the TEGA instrument looked like it would take some time to be prepared for the sample. But, uh, because it's done so well, we'd really like to go back and do our first sample delivery to TEGA.

                                    It has a larger entry port. And, uh, we've practiced this move many times. So we'd like to go back to our original plan and-and, uh, the first sample go to TEGA.

Alan Fischer:                And, a follow-up on that question, Peter, in terms of timing, when do you expect the first delivery of a sample to one of your scientific instruments?

Peter Smith:                  Well, [Sully, 7, 9. Oh, yeah.] We're thinking, uh, Sol 9 is the first delivery day.

Alan Fischer:                Okay. Thank you very much.

Ray Arvidson:               Yeah. This is Ray. What we need to do is look at the downlink tonight, uh, and make sure that TEGA's ready, that the-the, uh, cover is fully retracted. Uh, and then, we're good to go. So it's Sol 9, 10. And, we want to make sure we're doing this right.

Alan Fischer:                Okay. Thank you, Ray.

Jane Platt:                     Okay. Our next question comes from Joe Palka at NPR. Good morning Joe.

Joe Palka:                     Good morning. Uh, I guess this is Peter. But, you can correct me if I'm wrong. I have two questions. The first is, uh, that, uh, print that came down over the weekend -- maybe you've already answered this. But, it doesn't look a little bit like a footprint. It looks exactly like a footprint. Uh, can you explain whether you were expecting to see something like that and exactly how the arm made that impression?

Peter Smith:                  Well, typically, it wouldn't look that way. It's-it's because we pressed down on a sloped section of the ground. So that one side pressed, uh, deeper into the material. That's the right side. And, the left side was off into a-a little -- almost, I think, not touching at all on the surface. And, perhaps Ray can explain the exact pattern that developed out of that.

Ray Arvidson:               Yeah. It's basically taking the-the robotic arm in a backhoe mode and just pushing on the surface. And, it's just by coincidence that it looked like it -- a footprint with toes.

Joe Palka:                     Okay. No conspiracy there. Fine. I'll take that. Uh, the second question is --

Ray Arvidson:               Uh, we don't have time for conspiracies. [laughter]

Joe Palca:                     Okay. I accept that. I'm -- I -- you guys have been good to your word so far. So we'll keep going with that. Uh, the second question is what -- can you tell us a little bit about what's happening on the surface today?

Male Voice:                  [Ray]?

Ray Arvidson:               In-in terms of the sequences that we built and are being implemented more or less as we speak, we -- the, uh, the big observation is to take the robotic arm, with the robotic arm camera. And, we're doing a stereo set of images of, uh, Holy Cow. And, the reason is, we want to map out the topography of these very interesting light-toned features in-in detail. So we have a baseline to detect changes.
                                   
                                    And, then, we're also doing a-a further r-retract on the TEGA, uh, cover. And, then, uh, remote sensing of the atmosphere and the terrain surrounding the-the vehicle.

Joe Palka:                     Got it. Thank you.

Jane Platt:                     Next, we'll take a question from David Perlman at the San Francisco Chronicle.

David Perlman:             Uh, hi, folks. Uh, this is Dave Perlman. And, uh, a question for Peter, I guess, or Ray, either one. Uh, in that white slab that everybody's sort of excited about, uh, if the, uh -- if the retrorocket blew away the soil, uh, presumably it was, uh, at a very high temperature.

                                    And, I'm wondering if in -- on that white surface, uh, there was any pitting that you noticed or any idea, any possibility that, uh, the blast from the retrorocket, uh, might have, uh -- I'll be fanciful here -- uh, melted a hunk of that ice? Or have you seen anything on that slab other than a smooth surface?

Peter Smith:                  Well, that's a -- that's a really good question. And, the science team has been pondering exactly that-that question. And, we do see a couple of pits in the feature called Snow Queen, which is under the northeastern, uh, Lander left.

David Perlman:             Yeah.

Peter Smith:                  And, uh, I'm sure you've seen those too. And, uh, there's a question as to whether those are caused by the thrusters, or perhaps the thrusters dislodged a rock off the surface and revealed a little depression underneath the rock. So, uh, we-we-we can debate it both ways, frankly. And, we don't see so many pits on the far side in the Holy Cow region. However, some of that, uh, material was overexposed in the first image.

                                    So now, we're going to take some better timed exposures, so that we don't have overexposed material. And, we'll be able to search more carefully for pitting. Uh, it's a good question. Remember the thrusters came down very quickly to the surface. And, even though they're quite hot, they didn't have much time to do any melting really.

David Perlman:             Oh.

Peter Smith:                  So I think mostly what they're doing is clearing material off the top of the-the -- what's likely icy material. Uh, although we don't have proof of that yet. But, it's hard to imagine, uh, this area covered in -- under covered with rocks and still, uh, making the troughs and the [hummix]. Ray, you want to add to that?

David Perlman:             [And, that's rock.] [crosstalk] No. No. That answers the question.

Ray Arvidson:               Uh, Dave, this is Ray. The other thing that we'll do besides looking at the detailed topography of Holy Cow, uh, and trying different exposures, uh, is to look at the same surface at different times of day. Because remember, we're above the Arctic Circle, and the sun doesn't go down at night. And, at midnight, we should be shining directly, uh, into Holy Cow.

                                    So if we are able to pre-position the robotic arm and point the robotic arm camera back under the Lander, we should see, uh, in fact, the shadow of the robotic arm cast onto Holy Cow. And, that's called an opposition effect. And, it tells you more information about the texture of the surface.

David Perlman:             [Huh]. Well, Ray, as a veteran of Viking, uh, you're doing the instant science again, uh, 32 years later. It's good to hear.

Jane Platt:                     All right. Thank you. And, we're going to take our next question from CBS News, Daniel Sieberg. Go ahead.

Daniel Sieberg:             Hi there. Uh, this may have already been covered before. But, I'm just hoping someone could update me on the status of the short circuit that's been a bit of problem, if anyone can tell me sort of where that's at, what's happening with the work around or any fixes?

Peter Smith:                  Yes, uh, I-I started the, uh, the press conference with the -- an update on that. Maybe you missed it. [Uh, close it.] What's happened is, uh, we've -- we have two filaments inside of the ionization chamber. And, they were both being used as, uh, part of the ionization process. And, since the primary filament, uh, apparently has-has been shorted, we have been able to sort of disconnect that and use the secondary filament as the primary.

                                    It wasn't even intended to be used this way. But, in fact, it does work if you do it that way. And, we'd actually done some testing in our laboratories, uh, previously. And, then, we've done some this week to be sure that this is a safe mode of operation for the TEGA instrument.

                                    And, uh, the laboratory tests on Earth show that that's the case. And, we ran a sequence last night on, uh, Mars that -- or we received the results of a sequence last night that show that we're able to get just the same sensitivity used in this, uh, secondary filament as the primary.

Daniel Sieberg:             Great. Thanks.

Jane Platt:                     Next question. Kelly Beatty from Sky and Telescope.

Kelly Beatty:                 Yes. Uh, hi, thanks. This is for Ray. Uh, uh, I'm wondering, the-the topmost soil layer seems to be really unconsolidated and just kind of loose. And, is that the nature of what you expected? Or do you -- did you imagine it to be somewhat more annealed and-and sort of compacted?

Ray Arvidson:               Uh, Kelly, everything that-that we have seen, uh, so far is consistent with the orbital data. From CRISM, which is the hyper-spectral imager on the Mars Reconnaissance Orbiter, we predicted basically, uh, weakly altered basaltic sand with dust. And, from [femus and TES], which as you know are the thermo instruments, the albedo and the thermal inertia put this into the kind of little bit [dirt crust], uh, regime.

                                    So, uh, having some loose material and crusty material is consistent with, uh, it's kind of pre-landing picture. I-I'm just, uh, struck by how crusty the material is in the-the scoop images. And, finally, the presence of some light-toned material, either ice or cemented soil. And, it remains to be seen exactly what the light-toned stuff is.

Jane Platt:                     Okay. Uh, before we take our next question, let me just remind you if you do -- would like to ask a question of our panelists, press *1, and the operator will put you in the queue. And, I also wanted to mention that this telecon will be archived for one week at 1-866-380-6745. And, the international caller number for the archive is 203-369-0348. And, we also plan to post it online, uh, some time today. All right. Let's go back to our questions. And, let's take Aaron Mackey at the Arizona Daily Star.

Aaron Mackey:            Thanks. Uh, this question is for Ray. Uh, I think you just addressed it a moment ago. But, I was just wondering if you could talk about the actual, uh, hard-hardness, the strength of the soil and how that measured up to, uh, sort of the projections and simulations that-that you guys had gone through in the months before landing?

Ray Arvidson:               Well, we actually have-have simulated robotic arm backhoe operations in, uh, loose material, poorly basaltic sand. And, we also then cemented the material and tried back-hoeing and scraping as a function of how much cement, how hard the material is. So when the robotic arm does its operation and actually get telemetry down that allows us to reconstruct, uh, the forces that would n -- be needed to do the back-hoeing operations.

                                    And, we-we haven't had a chance yet to look at the telemetry. But, what we'll wind up doing is comparing those measurements to what we got in the -- in the pit over the past month or so, uh, based on back-hoeing in materials with different degrees of cementation or-or strength. But, it looks to me like this is, uh, basically, the strength of duricrust, which we've encountered with the two Viking Landers and, uh, the Spirit Rover in the Gusev Plains and up on the Columbia Hills.

                                    And, it's-it's fairly easily broken. And, if you look at the-the, uh, the first dig site, the little trench that we made and also the-the dent that we made that looks like the footprint, uh, that material is crushable. And, it looks like we can push it, and it retains, uh, the shape, which means that it's easily broken, kind of like, uh, a little bit cemented garden soil.

                                    And, it's poorly sorted. It's sand but with a fair amount of silt and dust. And, what happens when you -- when you push on that material, it breaks apart. And, the fines kind of fill in the interstices or the-the voids in between the sand grain. So it kind of retains the shape. So it's not going to be really strong stuff, nor is it totally loose but something in between.

Aaron Mackey:            Thank you.

Jane Platt:                     Okay. Thank you, Ray. And, I just want to remind our panelists to identify yourself when you do respond to a question. It's helpful to our reporters who are on line. Uh, okay. The next question, we're going to go to John Johnson of the L.A. Times. Hello, John.

John Johnson:               Hello. Thank you. Uh, two questions, real brief. Did you just d -- use the term duricrust? Is that what you said?

Ray Arvidson:               Uh, this is Ray, and I did say duricrust.

John Johnson:               Okay. And, that's D-U-R-A-C-R-U-S-T?

Ray Arvidson:               Or D-U-R-I [would be] --

John Johnson:               Okay. All right. And, the other question is that, could you go into a little more detail if you don't mind about this filament problem and the short. And, I mean, what does the filament do? How did it -- how did it work? And-and how does the work around work?

Peter Smith:                  Well, the mass spectrometer is really quite a complex piece of equipment. And, uh, it's able to use, uh, magnetic fields to-to turn particles based on the charge that they carry and the mass that they carry. And, so we have detectors that can pick up the charge-to-mass ratio. And, so, unless you charge the particles, the magnetic field has no effect on them. And, so we have an ionization chamber that applies a charge to each of the particles that comes in out of the oven.

                                    Now, if the, uh, the filament that ionizes these materials is shorted, of course, you get no charge at all. And, then, the instrument doesn't work. So we're-we're happy to report that we have a back-up filament that is capable of charging these particles as they come in. Or --

John Johnson:               Okay. So the p -- so the filament is what is responsible for charging the particles for the --

Peter Smith:                  That's correct --

John Johnson:               Mass spectrometer.

Peter Smith:                  That's exactly correct. It has a high voltage that, basically, uh, induces a charge or an ionization to the particles as they come in.

John Johnson:               Okay. Thank you.

Jane Platt:                     Okay. Next question is Dan Vergano from USA Today.

Dan Vergano:               Hi. Uh, thanks a lot. Uh, I was wondering if, uh, TEGA is-is going to have samples coming in Sol 9 or 10, how soon do you have results, uh, do you expect? And, I-I had a follow-up question.

Peter Smith:                  Probably not as soon as we'd all like. Uh, we'd like instant results. But, the TEGA instrument actually goes through a-a-a four-day process to analyze the sample in the ovens. And, the -- it's not necessarily four days in a row starting on the day the sample is collected. So this will be part of our-our tactical process is to take a measurement at low temperatures. Try and see what the results are.

                                    Then, we agree to go to the next step, which is a higher temperature sweep through the ovens. And, then, finally, on the third day, we go through an entire sweep from the low temperatures all the way up to 1000 degrees centigrade, which is 1800 degrees Fahrenheit, enough to drive gases out of even the-the most, uh, uh, [recalcitant] t -- uh, soils. Uh, I didn't give my name. My name is Peter. [laughter]

Dan Vergano:               And, uh, I-I was also wondering --

Peter Smith:                  [Sorry, Dan. Excuse me.]

Dan Vergano:               [Hi], Peter. Uh, I was also wondering, uh, if you guys could give a little historical perspective since you do have the Viking veterans there. How does this sort of schedule, uh, uh, compare to-to getting results back then? If it's faster, sooner or it's not possible to compare?

Ray Arvidson:               This-this is Ray, the Viking veteran. Uh --

Dan Vergano:               Yeah.

Ray Arvidson:               You're asking me to remember what I did over 30 years ago. Uh, I think it's a comparable schedule. You know, in that, we didn't have the TEGA. We had the gas chromatograph-mass spectrometer. And, you know, again, we needed to get the surface sample arm on Viking unstowed and all the instruments checked out. And, I -- my sense is, but my -- you know, my h -- memory is a little hazy here. [laughs] Is that the timing's just about the same.

                                    And, the other point to make on TEGA, that the reason we do different temperatures, it's an instrument called a differential scanning calorimeter. And, what happens is that minerals break down or thermally decompose at different temperatures. And, uh, as you apply the current, what will happen is the-the, uh, the systems will tell you, uh, what the mineral phases are as a function of the-the breakdown temperature.

                                    And, then, as Peter said, what happens is we stream the gases into a mass spectrometer to do that isotopes. So it's a really interesting instrument. But, it takes, you know, four or five Sols of-of measurements to really get -- pin down the results.

Dan Vergano:               Are those pre-set temperatures? Or can you dial to specific temperatures if something seems interesting?

Ray Arvidson:               I think they're pre-set for now.

Dan Vergano:               Okay. Thanks very much.

Jane Platt:                     Okay. And, uh, thank you to our panelists for identifying yourself. I know it probably seems like, uh, not important to you. But, trust me, we would get a lot of phone calls here afterwards from people asking us who said what. So that --

[Peter Smith]:               Yeah. Peter is the big guy.

Jane Platt:                     [laughs] Okay. All right. Our next question is from Irish Television, Leo Enright.

Leo Enright:                  Thanks very much, Jane. Uh, I got my funny glasses on, and I'm looking at the, uh, the test trench. And, uh, I was quite struck by the cohesiveness of the soil. Uh, I guess this is for Ray because you said earlier that this was poorly sorted. But, uh, my journalist eyes start trying to see layering at the back of the trench. And, I'm wondering, is there anything in the higher res pictures that you have, uh, that-that suggest a structure.

                                    And-and also, in relation to that, uh, what-what does this picture -- uh, does this give you more confidence that, when you go to trench, uh, one of these cracks, uh, that you're going -- that you're -- that the soil isn't going to all fall in on top of you. And, that you are actually going to get the sort of layering that, uh, that you're hoping for as you try and understand the history of the -- of the filling of these cracks and the polygynon -- pol-polyg-polygons?

Ray Arvidson:               Hey, Leo. This is, in fact, Ray. So the -- I think the layering -- the apparent layering that you see in the back is-is just associated with the-the, uh -- how the robotic arm operates and the dent that it makes, uh, when it first contacts the surface. Because we were pretty excited to see the -- [this puditive] layering at the back. But, talking to the robotic arm team, it-it just seems to be an artifact of the -- of the digging.

                                    And, what's really nice is that the, uh, the material maintains the [slope], uh, which indicates that, when we go in to do the big trench -- and it may be a trench that, you know -- uh, the trenches are radial, uh, away from the-the Lander because the-the robotic arm only has four degrees of freedom. But, the nice thing is, we can go from, for example, if we wanted to, from Humpty Dumpty down into the Wall and, uh, expose the soil and dig down and dig down until we see -- hopefully hit the-the ice layer, which I don't think is going to be too far down.

                                    But, it all looks good in that the material is-is cohesive and maintains a pretty steep slope. As [well], you know, we've-we've done on-on the two Vikings, Pathfinder and the two Rovers, our-our slopes on the trenches we've done in all those cases are like 65 degrees in terms of the angle. So angle reposed for loose material is closer to 30. So this material does have some cohesive strength.

                                    And, it's some combination of being crusty and then being poorly sorted where the-the fine grain material fills in the interstices in between, or the voids in between, the sand grains. And, it just maintains this nice shape.

Pat Woida:                   This is Pat. And, let me also add we can also measure the angle of repose, not just in the trench and the surface, but we're doing that in the material in the scoop as well. That is, we can tell what kind of angle can we maintain depending on how the scoop has been tipped.

Ray Arvidson:               And-and this is Ray. We'll do the-the same angle measurements in the dump site, uh, which we haven't had a chance to do. But, we do have a-a nice, uh, image of the dump area. And, we can see the pile.

Jane Platt:                     All right. The next question is from Aviation Week, Craig Covault. Hello, Craig.

Craig Covault:              Yeah. Hi. Good morning. Can you hear me okay?

Jane Platt:                     Yeah. We hear you great.

Craig Covault:              Uh, again on TEGA, uh, is here hope for getting the initial filament back? Or is it, uh, deemed, uh, pretty much gone for good? In other words, is there any redundancy left? And, secondly, uh, if you relate it back to pre-launch problems, uh, with the ionization system there, yesterday it was mentioned that, uh, it was believed to be a contamination problem.

                                    Uh, not that you're settled on the surface as opposed to it being in [GOG], en route, does the analysis indicate that whatever caused this is probably going to stay put and not, uh, be a factor for another circuit problem?

Peter Smith:                  Well, Craig, this is Peter. Uh, we had a backup plan in case this, uh, second filament did not, uh, give the sensitivity we needed or in case it had some other problem, we-we-we [just] discover, uh, last night would be the first time we've known about that. If that happened, what we can do is try and shake this particle loose -- and we assume it is a particle on the first filament -- by, basically, slamming a-a valve open and closed that's right near to it.

                                    It's [the solanoid] valve, and it-it adds a lot of, uh, vibration and shock as it operates. And, uh, the problem first presented itself as intermittent. In other words, the valve opening and closing kind of knocked this particle into a bad position on the filament and cause a short. And, so we could keep kind of hammering this thing, uh, which nobody wants to do. But, we could do it. And, uh, that would, perhaps, free up our first filament. And, we could go back to the primary operations mode.

Craig Covault:              All right. Thanks.

Jane Platt:                     Next question is from Alicia Chang at Associated Press.

Alicia Chang:                Hi. Uh, this question is for Ray. Uh, I was wondering if you can talk a little bit more about the practice dig that you did yesterday. You know, how deep did it go? And, whether you plan to do any more test dig before the actual, uh, uh, delivery to-to the TEGA instrument?

Ray Arvidson:               Hi, Alicia, this is Ray. So the-the idea here was to first do the touch, which, as you know, we did. And, then, uh, a test dig, which is now-now accomplished. And, it's several centimeters deep. And, then, we-we took that material and dumped it from a height of about 50 centimeters off to the left in an area where the robotic arm can't dig. That was all very, very successful. So I don't think we need to do any more testing.

                                    So I think the robotic arm team is-is really eager to get on with business. And, we're in the process now of-of selecting three contiguous sites where we could do a TEGA sample and then shift and do a-a MECA-OM sample and then shift and do a-a MECA-wet-chemistry-lab sample. So, you know, we're-we're ready to go.

                                    And, we're just paced based on, uh, uh, getting TEGA ready, doing some more, uh, retraction. And, in the next couple [falls], we expect to deliver to TEGA. And, then, following that, to OM. Following that, to [WCL]. So we're pretty excited to get on with business here.

Alicia Chang:                So how soon would the actual, uh, dig, uh, to put into the instruments, how-how soon would that be? Would it be tomorrow or Wednesday?

Ray Arvidson:               At-at the earliest, it's, uh, probably tomorrow-ish.

Alicia Chang:                Okay.

Ray Arvidson:               But, you know, we want to go carefully here and make sure the instruments are ready. But, in terms of the robotic arm and the scoop, we're-we're good to go as soon as, uh, we're clear to do delivery.

Alicia Chang:                Great. Thank you.

Jane Platt:                     Okay. And, I do want to tell you that, at the end of this telecon -- and we do have some more questions. But, at the end, I'm going to give you some information. We have a media telecon scheduled again tomorrow. So we'll give you info on that. Let's take a question now from Andrea Thompson at SPACE.com.

Andrea Thompson:       Hi. Uh, I was wondering, uh, when is sort of -- are you going to decide finally whether you're going to go to TEGA or MECA first?

Peter Smith:                  Uh, that decision has been made --

[Ray Arvidson]:            And, who are you?

Andrea Thompson:       Andrea Thompson, SPACE.com.

Ray Arvidson:               No.

Andrea Thompson:       Oh, from -- [laughter]

Peter Smith:                  Apparently, uh, I have to introduce myself. I'm Peter. Peter Smith at the University of Arizona. And, uh, we-we made this decision, uh, a day or two ago. Uh, I'm kind of losing track of which day is which, but I think it was two days ago. That we would go back to our original plan and deliver the first sample to the TEGA instrument. That gives us, I think, a very high probability of a successful delivery. And, uh, we need that kind of morale boost to get started on the rest of our program.

Andrea Thompson:       [laughs]

Pat Woida:                   This is Pat. Let me also add, we've already taken the next step towards that by retracting the covers off of the TEGA. So that is, that we've opened up the covers, so now we can get up those [stores] in order to make that delivery. That would be the next step in the process. So we've moved past the filament onto getting TEGA ready for taking samples.

Andrea Thompson:       Great.

Jane Platt:                     The next question is from New Scientist magazine. I hope I pronounce your name correctly. Ker Than.

Ker Than:                     Yes. That's correct. Uh, on the, uh, the Phoenix Web site, it says that, uh, the white material in the soil sample that, uh, the, uh, the scoop collected, uh, might be ice or salts that have precipitated into the soil. I'm just wondering if that's something you expected and if you could talk about what, uh, the implications of that might be?

Ray Arvidson:               Well, this is Ray. So it-it could be a salt, like a magnesium sulfate. Uh, we saw the -- at the two Viking sites and the Spirit site, an increase in magnesium and sulfur in terms of the chemistry. And, there's a mineral called kieserite, which is magnesium sulfate with, uh, a water molecule embedded into the structure. And, it has the right-right kind of bright, uh, tone that-that you'd expect based on what we see in the scoop.

                                    So we're really carrying two ideas here. One is that we're seeing the-the material that is cementing the soil and making it a little bit cohesive. Or, you know, we've actually exposed the top of the ice table. And, we have a little bit of ice in the -- or had it in the scoop before we dumped. And, it -- as you know, there's a little bit of light-toned material also at the bottom of the hole that-that we dug.
                                   
                                    And, the way to tell is to get, uh, a sample into TEGA and, uh, kieserite, magnesium sulfate with the water in it, if that's what it is, thermally decomposes. And, you'd see that in-in terms of the temperature ramps run with TEGA. Or if it's ice, likewise, that will thermally decompose but at a different temperature. So there is a way to test between those two hypotheses.

                                    The other point I'd make is that, remember, we're only about 30 kilometers away from the rim of this 10-kilometer-wide crater that we informally called Heimdall. So we're sitting on the [ejector] deposits of a-a rather large, fairly fresh crater. And, that impact process probably involved, uh, uh, fluids because it looks like the [ejected implacement] proper was a ground-hugging flow.

                                    So we may be in a -- in a unique environment, uh, that-that led to a fair amount of cementation or ice close to the surface, uh, which we'd expect anywhere. But, uh, it remains to be seen. You know, it's un -- in my mind, I'm still carrying two hypotheses. The-the extensive area called Holy Cow is called Holy Cow because it was so sp -- exciting to see.

                                    But, -- that likely is ice, but, you know, it's not impossible that we're looking at-at some massive amount of salt because we're on this special, uh, [ejector] deposit that we never really landed on before with any of the previous vehicles.

Ker Than:                     Thank you.

Jane Platt:                     Next question is from Science News, Ashley Yeager.

Ashley Yeager:             Hi. I was wondering, can TEGA respond to the Harvard paper about having too much salt for life on Mars? Or do you have to wait for MECA to respond to that? [unintelligible] 

Peter Smith:                  Well, you know, our-our science group here has been --

Male Voice:                  Who are you?

Peter Smith:                  Oh, gosh. Hello. My name is Peter. [laughter] Uh, our science group here has been awfully busy in the last few weeks and haven't been reading too many of the new papers coming up. And, uh, I hate to say it, but, uh, we haven't read the paper. So it's hard to comment on it.

Ashley Yeager:             Okay.

Jane Platt:                     All right. We're going to take a question from Sally rayl, Planetary Report. Sally, you on?

Sally Rayl:                    Yes. Hello. Can you hear me?

Jane Platt:                     Yes, we can hear you fine?

Sally Rayl:                    Great. Uh, Peter, you mentioned the other day that the King's Horse, I think, was the possible first target for the dig. I had some phone issues and got in just a couple seconds late. Is that still the plan?

Peter Smith:                  No. No. It's King of Hearts. [crosstalk]           

Sally Rayl:                    King of Hearts. I'm sorry.

Peter Smith:                  King of Hearts, not King's Horse.

Sally Rayl:                    I'm sorry. I stand corrected. King of Hearts. Is that still looking like the first possible?

Peter Smith:                  Well, Ray-Ray can answer that. The -- my-my name's Peter, by the way. And, [laughter] Ray-Ray can answer that.

Sally Rayl:                    [You there Ray]?

Ray Arvidson:               Yes, Sally. What-what's happened is that, uh, King of Hearts -- I think it's Knave of Hearts actually -- uh, is the area that we're thinking about. But, it turned out, uh, to be a little bit too far away from, uh, the, uh, ability of the robotic arm to successfully get a good sample. So where you see the-the first dig is a good distance. So what we're thinking about it moving to the right and then doing a set of samples, like one, two, three, side by side to-to TEGA then MECA-OM, then MECA-WCL.

                                    But, you know, this is still in discussion. And, Peter appointed me the dig tsar, which means all the science team members are giving me pointers on what to do. So we're going to have, uh, a continued set of discussions over the next couple Sols in terms of the strategy. But, what we want to do is get surface samples from contiguous areas. So we're looking at the same materials with the three different instruments.

Sally Rayl:                    Do those, uh, three spots have a name yet?

Ray Arvidson:               Just a minute.

Male Voice:                  I don't know. Do they have any? [unintelligible] 

[Ray Arvidson]:            What-what we're thinking about it this, uh, as you know, we're trying to make names that people resonate with and that come from fairy tales. So it would be kind of nice to name the three contiguous samples, say Baby Bear, Mama Bear and Papa Bear.

Sally Rayl:                    Okay. Is that unofficial? [unintelligible] 

Ray Arvidson:               I'm looking at the person called Peter, and he's looking at me. [laughter] So I think that it's probably official.

Peter Smith:                  That -- this is Peter. Ray's now the dig tsar, so I think he's, uh, allowed to give the names.

Sally Rayl:                    Uh, the dig tsar. I have one other question. Uh, uh, because I missed the actual introduction, Pat, uh, can -- what is Pat's last name?

Pat Woida:                   Woida. This is Pat. The last name is spelled, W-O-I-D-A. Senior engineer.

Sally Rayl:                    Thank you very much.

Jane Platt:                     All right.

Sally Rayl:                    [I'll get here on time next time].

Jane Platt:                     I'm sorry. What was that?

Sally Rayl:                    Next time, I will not miss the introduction. Thank you.

Jane Platt:                     Okay. [laughs] All right. Thanks. The next question, Chronicle of Higher Education, Richard Monastersky. Did I get that right?

Richard Monastersky:   Yes, you did. Can you hear me?

Jane Platt:                     Great. Uh, can you speak up please?

Richard Monastersky:   Yes. Yes. So I wanted to ask about what the temperature is like there, what the range is over the -- over the day and if the range of temperature changes at height tell you anything about the characteristics of the spot that you landed?

[Peter Smith]:               Uh, yeah. That's a real good question. The-the extremes that have been measured so far are, uh, -30 centigrade, uh, for the high temperature and down to -80 for the low temperature. Uh, that's centigrade. And, I think in-in Fahrenheit, that goes from -22 Fahrenheit to -112 Fahrenheit, which is close to the coldest temperatures, uh, ever recorded on Earth. Although, I think that's -130.

                                    Uh, so it's-it's really getting cold when the sun is low on the horizon. Uh, let's see. The-the other question is about the-the change in temperature with height. Well, the temperatures, uh, start to cool off as you get away from the surface. Remember, the sun is heating the surface. And, the surface is heating the atmosphere. So think of it as a hot plate on the surface. And, the atmosphere is being heated from the bottom.

                                    Uh, we-we do see temperatures changing with height. And, in fact, as you get into the afternoon, you see a kind of a, uh, what looks like, uh, noise on the temperature channel. It's-it's, uh, very quick changes in temperature caused by, uh, thermal-thermal pockets of air being blown past the Lander. And, this is what we think of as the convective zone on the surface.

                                    And, so you see very rapid changes in temperature all through the at -- the afternoon. And, then, it calms down and just has a very stable atmosphere late at night. Uh, this was also seen at, uh, Pathfinder and, I think, probably Viking. The temperatures change so rapidly from the surface up that, you know, if you were standing on Mars, your-your head would be 20 degrees cooler than your feet. So it's-it's quite a strong effect there.

Richard Monastersky:   Are these the coldest temperatures ever measured on Mars?

[Peter Smith]:               No. Actually, uh, it's -- in the equatorial zones when the sun actually does set at night, and you have time to really cool off, it can be considerably colder.

Richard Monastersky:   Thanks very much.

Jane Platt:                     We're going to go --

[Peter Smith]:               But, as we go towards winter, it's going to get colder. Don't you worry.

Richard Monastersky:   Right.

Jane Platt:                     We're going to go back to the Tucson Citizen newspaper, Alan Fischer.

Alan Fischer:                This question is for Peter. Peter, I had a follow-up on your, uh, uh, explaining that it takes four to five Sols to-to analyze the materials put into TEGA. Just to be clear, Peter, is that a single, tiny sample that we're looking at over four or five days with several different temperature ranges? Or are those multiple samples?

Peter Smith:                  Yeah. Good question. It -- w -- each oven has a-a process for analyzing the tiny sample it re -- it receives. And, that sample will go through a five-day process, four-day process, uh, depending on how much, uh, pause we take between the four steps that it has to go through. So it's the same sample.

Alan Fischer:                Thank you.

Jane Platt:                     Okay. We're going to take a -- before we take a question from Leo Enright again, I did want to sort of do a last call. If you do have a question, before we wrap up, please press *1, so we can get you in the queue and give you an opportunity. But, in the meantime, we'll go to Leo.

Leo Enright:                  Thanks, Jane. Uh, just a-a couple of follow-ups. Uh, one has to do with Three Bears, if you could just, uh, Ray, tell us where those Three Bears are. The only image that I have that's on the sight that t -- that gives us a clear picture of-of, uh, the name -- naming regime shows Humpty Dumpty, Wall, Sleepy Hollow, King's Horses, King's Men, Headless, Ichabod. I mean, can you give us some idea where, on that, uh, particular picture, uh, the Three Bears are?

                                    And, my second question was for Peter about calorimetry. Uh, when does the calorimetry start on these samples? And, would that potentially be a wow moment, uh, that you would, uh, expec -- you might -- let me not say expect -- that you might see something pretty much straight away that tells you the, uh -- whether this is ice or not?

Ray Arvidson:               Yeah. Leo, this is Ray. So we're still defining the location of the Three Bears. Uh, and it-it's a combination of science desires and robotic arm engineering reality. But, it's likely to be just to the right of the, uh, test dig that we did. But, we should get that together in the -- in the next Sol and-and post a location.

Leo Enright:                  And, that's without going [international park] then. Is that right?

Ray Arvidson:               We want to preserve as much of, uh, the Humpty Dumpty National Park as possible. [laughter]

Peter Smith:                  Yes. And, this is Peter. You had a question about, uh, the TEGA calorimetry. Well, that starts right away. Uh, the low temperature, first heating cycle is designed to drive off water. So there may be some ices in the soil. And, you would see that right away on the first, uh, heating cycle, which just goes up to the boiling point of water, basically, 100 C.

                                    And, then, uh, over the next few days, they heat it a little hotter, which the idea is to drive out as much water as possible because that tends to swamp our mass spectrometer. And, uh, and then, the third cycle is when you heat up to 1000 degrees, and that's when you're going to see the-the real mineral structures, the kieserite, the magnesium sulfate or any other minerals. They could be carbonates, sulfates, uh, or a whole range, clays, for instance.

                                    And, uh, and in order to-to get a baseline for what these transitions between, uh, mineral phases are actually doing, after we heat it up the first time up to 1000 degrees, we do the same heating cycle again. And, now, the materials are all, uh, basically, uh, uh, inert. And, you can get a baseline for the instrument to do a subtraction. So there's-there's four days that are planned for each sample.

Jane Platt:                     All right. Next, we'll go to the Pasadena Star News and Dan Abendschein.

Dan Abendschein:         Yes. Hi, there. Question for either, uh, Ray or Peter. Uh, I'm sort of a novice to this, so I apologize if this is already pretty obvious. But, uh, I'm curious to know -- uh, we've been reading some of the coverage. And, uh, my understanding is that, uh, you expected it might take, uh, a matter of a week to actually read -- reach an ice layer. Uh, if it is, in fact, ice, are you surprised and, uh, how unusual would that be?

Ray Arvidson:               Uh, this is Ray. I didn't catch the last sentence.

Dan Abendschein:         Uh, if it is, in fact, ice that you found this close to the surface and, uh, this quickly, uh, were you su -- are you surprised by that possibility? And, uh, is this -- h -- is this defying expectations? Or is it, uh, about what, uh -- about the norm?

Ray Arvidson:               Well, uh, this is Ray. It's about what we expected form the pre-landing orbital data because you can actually detect hydrogen from the neutron spectrometer on Odyssey. And, that, together with the gamma ray spectrometer, when the -- when [one models that] suggested a dry layer of soil of a few centimeters over a hard icy layer. And, it-it's also consistent with, uh, climatic models as to how deep the-the ice would be and still be stable under current conditions.
                                   
                                    And, then, finally, it's consistent with, uh, the thermal wave over-over a year. You can actually track the-the depth of loose soil or duricrust and then icy, really very thermally conductive, uh, material beneath. And, it also s -- all suggested -- all three approaches suggested that we would have a few centimeters to 10 centimeters of soil over a discreet horizon.

                                    And, beneath that, to have, uh, very hard, icy soil. So we're not surprised. We're just, uh -- we're glad. [laughter] You know, that-that we seem to have this, uh, discreet horizon just centimeters beneath the surface, which we think is ice, but, you know, we still need to get into the analytical instruments to confirm.

Dan Abendschein:         Okay.

Jane Platt:                     All right. Next question is KVMR, Alan Stahler.

Alan Stahler:                 Thank you. Alan Stahler, KVMR. Could you tell me the significance and also spell the name of the [hydrated] magnesium sulfate mineral [you were] talking about. It sounded like [Tessa -- tesarite] or something.

Ray Arvidson:               [laughs] Yeah. This is Ray. Kieserite is not a common mineral on Earth. So it's K-I-E-S-E-R-I-T-E.

Alan Stahler:                 And, the significance?

Ray Arvidson:               Well, it's-it's a magnesium sulfate. So it's MgSO4.

Alan Stahler:                 Mm-hmmm.

Ray Arvidson:               And, it has, uh, I think, two waters in it. And, it's a mineral that formed --

Male Voice:                  One.

Ray Arvidson:               Oh, I'm sorry. One water.

Alan Stahler:                 Okay.

Ray Arvidson:               Monohydrate. And, it forms in, uh, an evaporitic environment. So you can imagine, uh, that we have soil. And, there are thin films of water that are coming up, and they have salts in them. And, the water evaporates into the atmosphere. And, it leaves behind the salts.

                                    And, what we're finding on the other sites on Mars is that a lot of the evaporitic minerals that we're seeing are sulfur dominated. So we see evidence for kieserite at the, uh, two Viking Lander sites and at the Spirit site. And, we also see evidence for this mineral kieserite and other sulfate minerals from the orbital spectrometers, the one on Mars Express called omega and the one on our NASA Mars Reconnaissance Orbiter called CRISM.

                                    So it-it wouldn't be unexpected. We just need to test and see if it's a sulfate. But, as Peter mentioned, it could also be a carbonate. It could also be a clay mineral. Or it could -- it could be ice. So you know, it remains to be seen. So-so far, we have imaging data, and we have, uh, how bright it is. But, we sure want to get the-the, uh -- these materials into our analytical instruments.

                                    The other point to make is that kieserite in the WCL experiment, or the wet chemistry lab, you know, where you put the-the soil into the chamber and then take the-the water that we brought, which is now ice, and melt it and put it in there, we should see the kieserite partially dissolve. And, we-we should see the magnesium and the -- and the sulfate signature in the detector.

Alan Stahler:                 Thank you.

Jane Platt:                     Next question, we're going to go back to Kelly Beatty from Sky and Telescope. Kelly.

Kelly Beatty:                 Yeah. This is for Peter, the big guy. Uh, eight and half years ago, the person in your chair would have been David [Page] of UCLA. I know he does -- I don't think he has an official role on this mission. But, have you had any exchanges with him? And, can you describe what those were -- are?

Peter Smith:                  Well, uh, you're correct. David was our lead scientist for the Mars Polar Lander Mission and, certainly, uh, had, uh, a lot of vision on how to do science in the polar regions on Mars. He was, of course, interested in the southern region and what's called polar layered terrain.

                                    So that's a little different than what we're on at the moment. But, uh, similar. Certainly similar. Yes, uh, he was invited to the landing. Uh, I don't think he came though. So we haven't actually had an interaction with him yet. Plan to.

Jane Platt:                     Okay. Uh, we're going to take a question now from Daniel [Fisher at Interstella] magazine in Germany.

Daniel [Fisher]:             Uh, hi. This is more of a technical question maybe. In the future of Holy Cow research, uh, will there be a possibility to actually get color images of Holy Cow like at night or at dusk? And, is there a possibility or would it make sense to actually touch it with the, uh, robotic arm [travel]?

Ray Arvidson:               Yeah. There -- I -- this is Ray. There are two questions. Further remote sensing of Holy Cow. And, uh, we-we do expect to image this, uh, surface at different times of day. You know, as I said, the sun doesn't go down. And, at midnight, it's shining directly at low -- at a low angle, directly from the north. Uh, so we should-should be able to pre-position the robotic arm and turn the rack on at about that time to take a picture.

                                    Color's going to be difficult because the color for the-the, uh, system is best done with the little, uh, light-emitting [diodes]. But, we can't get that close. And, Holy Cow is under the vehicle. And, the robotic arm is-is incapable of, uh, getting under there. So that, unfortunately, is precluded.

                                    And, that's why we want to expose what we hope is the equivalent material, uh, in the next few weeks, uh, with the robotic arm and the backhoe. So we can get down to that light-tones surface.

Jane Platt:                     Okay. I think we've gotten to all of our questions. Before we sign off and before I give the information on the rest of the events, the media telecons, the news conferences for the rest of the week, I did want to offer the panelists [at] the University of Arizona an opportunity to jump in with anything they didn't get a chance to say. I know, sometimes, you might be sitting there wanting to say something. So does anybody have anything that we didn't cover?

Female Voice:              Looks like they're all shaking their heads no. [crosstalk]

Jane Platt:                     Okay.

Male Voice:                  I think the answer's no.

Jane Platt:                     Okay. All right. Great. We've had some lively discussion. And, I do want to tell our folks online -- thank you to all our panelists by the way. Great job. And, as a reminder, additional information and the images for Phoenix are online at www.nasa.gov/phoenix and also at phoenix.lpl.arizona.edu. Thanks again to the panelists, and thanks everybody. Have a good day.

 

 

 

                                   

 

 
 
 
Related Links
› NASA Phoenix site

› University of Arizona Phoenix site

› JPL on Facebook and Twitter

› Landing Press Kit (3Mb - PDF)

› Launch Press Kit (6.5Mb - PDF)

› Mission Fact Sheet (244Kb - PDF)

› NASA Mars Exploration site

› NASA/JPL Landing Blog

Other Missions at Mars
› Mars Exploration Rovers

› JPL's Rover News and Image

› Mars Reconnaissance Orbiter

› Mars Odyssey

› Mars Express

 
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