Mission News

JPL Media Teleconference - 11.12.09

Female Voice:           Welcome, and thank you for standing by. At this time, all participants are on the listen-only mode. Today's conference is being recorded. If you have any objections, you may disconnect at this time. Now I'd like to turn the meeting over to Mr. Dwayne Brown at NASA headquarters.

Dwayne Brown:        Thank you, Operator, and good afternoon, everyone. Again, my name is Dwayne Brown with the office of public affairs. And today's subject is to discuss attempts to free the Mars Rover Spirit from sandy soil where it's been stuck for the past six months. Our presenters will compliment their remarks with visuals on the web, and I know the link was attached to the media advisory, but for a quick link, for those who have joined us, www.nasa.gov/rovers, and you'll see a link at the top that will have the link that says media conference, and you can go to that for the visuals.

Also for our television media on this call, we are currently running video, animation, and interviews with the Mars rover team on NASA Television and check your local scheduling for the airtimes. We have a replay number that will record and replay the entire telecon. That number is 888-820-8959. Again, 888-820-8959. And before we open it up for Q&A, again we'll have presentations from our participants, and I'll introduce them to you at this time.

First up will be Doug McCuistion, director of the Mars exploration program here at NASA headquarters in Washington. And I may add that the Mars chief scientist is also here, Dr. Michael Meyer, and during the question and answer period, he may chime in to add any information on a particular question. Following Doug will be John Callas, project manager for the Mars Exploration Rovers at NASA's Jet Propulsion Laboratory in Pasadena, California.

Following John will be Ashley Stroupe, rover driver for the Mars Exploration Rovers at JPL. And following Ashley will be Ray Arvidson, deputy principal investigator for the Mars Exploration Rovers at Washington University in St. Louis. So with that, I'll turn it over to Doug to kick us off.

Doug McCuistion:    Okay. Thank you very much, Dwayne. Good afternoon, everyone. Thanks for joining us for this -- what I would call a bittersweet press conference regarding the rover Spirit. Spirit, as Dwayne mentioned, did the equivalent of falling through the ice over a frozen pond back in April of this year and has not been able to pull itself out to date. We did attempt to do that earlier a little bit, realized how complicated the situation was, and the rover teams, plus some outside help, have been investigating and exploring ways to get it out of this situation since then.

To allay questions about Opportunity, I thought I'd take us back and talk about Opportunity briefly, and then we can concentrate on Spirit for the rest of this press teleconference. Opportunity is now on Sol 2063 of its 90-day mission. It's doing quite well. As you can see from the first graphic of mine, the Opportunity Traverse Map, it began back at Eagle Crater in 2004, and as everyone probably remembers, it hit a gold mine upon landing in Eagle Crater.

It's had a fantastic journey in the nearly 12 miles it's driven so far, finding iron meteorites, hematite blueberries, lots of water-related sedimentary rock and other water processes were proven on the surface. It even investigated its own heat shield at one point, when it ran across that. It had a battle with being stuck in the sand once also in Purgatory Dune. It was successfully extricated from that, and we did learn something to help us with this. As you can see, it's been quite a journey.

Down in the bottom right of this image is Endeavor Crater. That's the ultimate destination of Opportunity, but it's another 4 to 5 kilometers away. It's quite a long drive. Still, hopefully we can make it. Things are going well. The rover is in essentially good health, a few minor glitches, but chugging along. So as exciting as opportunity was when it landed, Spirit has had a harder road to hoe from day one. When it landed in Gusef Crater, you can see by that second graphic called Spirit's Travels, it landed in a relatively featureless area. It wasn't terribly exciting.

The rover teams sat down and decided what do we do with this? And it was decided to set off on a trek to Columbia Hills, which are on the right-hand side of this image. The plucky little rover made it to the hills. Not only did it make it to the hills, but it has remained in those hills and has discovered some phenomenal things. A mission that we were concerned was going to be largely unachievable, if it only survived 90 days, has turned out to make some of the most spectacular scientific investigations yet down on the surface of Mars, especially the Home Plate area, which you will hear more about momentarily from Ray Arvidson.

So it landed in a rather featureless area, and then we continued to have some issues. We had some software issues after landing. Spirit had a failed right front wheel in 2006, which I'm sure that John will talk more about. We've had some recent amnesia events. All of these have been overcome, but unfortunately, Spirit may have met its match in this one. We will see if we can get it out of this talcum powder type soil that laid beneath a seemingly innocuous surface crust that we broke through back in April.

The rover teams have been working very hard since April. They've been testing, strategizing, analyzing, and modeling to figure a way out. We even called experts in soil mechanics and mechanical systems in to try to help us understand the environment. But there's only so much you can do on Earth to simulate Mars. The plan is -- and you'll hear more about this -- the plan is to send the first commands on Monday, but this process could take quite a while, if it's possible at all to get Spirit out of its predicament.

So despite all the hard work that's been done and the preparations made, this could end up being where Spirit remains. So to provide more details on the situation from an engineering and scientific perspective, I'd like to pass it over to John Callas, the Mars rover project manager and continue the discussions.

John Callas:              Thank you, Doug. Good afternoon to those on the East Coast, good morning to those on the West Coast. About six months ago on Sol 1886, Spirit was traversing in a region around this feature we call Home Plate. If you look at my first graphic, which is titled Spirit's Travels in the Home Plate Neighborhood, you'll see in the upper portion of that image this large circular feature called Home Plate. It's about 80 meters in diameter, so about 250 feet across.

And Spirit has spent most of her time on Mars around this particular feature. We've survived three winters now, two of those winters were in the region of Home Plate. The most recent winter was right on the north edge of Home Plate. And if you look carefully at the graphic, you can see roughly on the 12 o'clock position [on] Home Plate where we spent the winter. Our objectives after that winter, which was a pretty hard -- harsh winter for the rover, was to get south to these features we've named von Braun and Goddard, which you'll see at the bottom of that same graphic.

But we had some urgency. Because so much dust had accumulated on the solar rays for the rover, we needed to get south to conduct as much science as we could before the next winter, and then possibly try to locate a winter haven for that next winter. But with a five-wheel driving rover, getting into a position that's favorable for the winter was quite problematic.

So we had tried to go first across Home Plate and ran into some difficulty trying to climb back up onto Home Plate. Then we tried to go around to the northeast and had difficulties there. So we were traveling around to the west, counterclockwise around Home Plate. And you can see indicated on the graphic the location called Troy. And that's where Spirit became imbedded in this loose fine material where we are now.

So if you look at my second graphic, which is the view of the traverse direction from Sol 1870, this is a navigation image looking south. You can actually see the feature von Braun in the distance there. And we were traversing across material that looked very much like material terrain that we had successfully traversed before. You can see that there are imbedded rocks, which was an indication of stability to the soil, and you can even make out sort of what we call a curb, if you will, or sidewalk directly ahead in that image.

And so that's where we were headed. And on Sol 1886, the rover started to have trouble. So if you just blink to the next graphic, which is the same image, but you now see indicated the Rock Garden in that image. That's where the rover has become imbedded, and that's where the rover is right now. So you can see that there's nothing obvious in this image that suggests that this is difficult terrain. But if you now will go to the next graphic, which is Spirit's Wheels Digging into Soft Ground on Sol 1899, we actually had done a set of moves.

And this is where we stopped. And this is now about six months ago. And you can see this is our first haz cam -- hazard avoidance camera images. And you can see the right front wheel, which is the wheel that stopped operating over three years ago, and you can see that's still up on the surface. But you can see the left wheel has dug down deeply and has revealed this loose fine material, this light-toned material, and you can see that the wheel is caked. The treads of the wheel are covered with this material, which also complicates its ability to gain traction.

Essentially, the rover was driving on what we call a dirt crust, and you'll hear Ray Arvidson describe this in a little more detail, but it was a hard surface that we broke through. And underneath this material, camoflagoued underneath, was this loose fine material where the rover is challenged right now. If you go to the next graphic, you can see what are the rear hazard avoidance cameras. Because the rover was traveling backwards, traveling south, when the imbedded occurred.

So this is looking south. You can see the rear wheels are also imbedded, and you can see, again, the light-toned material has been churned up and the wheels are sunk. Now, the rover has moved slightly over the course of the last few drives we did, but it was exceedingly high slip, almost 100 percent slip when we were moving. So on Sol 1899, we experienced a left middle wheel stall.

And this is when we stopped tactical activities and began a more detailed assessment of the situation of the rover and realized that the rover was seriously imbedded at this point, that mobility was very compromised, and the rover was sunk in. With subsequent analysis, we realized that that mound of rocks that you saw in the earlier image actually posed a threat to the underbelly of the rover.

And through some detailed analysis of the rover's position relative to the terrain, those rocks actually do pose a risk to the underbelly, and one of them is likely what's contributing to the left middle wheel stall that occurred. And we've done subsequent diagnostics on that wheel, and it has moved freely one full rotation in both directions, but that rock or whatever mechanism that caused the stall may be a complication going forward.

So at this point, the project stood down from any driving operations on the rover, although it remained active scientifically, and we commenced a very ambitious ground test campaign where we tried to simulate the situation on Mars here on Earth. At the Jet Propulsion Laboratory, we have a test facility where we have a full-scale, high-fidelity engineering model of our rover. So if you go to my last graphic, which is the one labeled Test Rover in Sandbox at JPL, you can see a photograph of the kind of testing that we are doing.

What you see is our full-fidelity test rover, which is almost identical to what's on Mars, in a special sandbox. The sandbox is 8 feet by 12 feet and about 2 feet deep. And it's filled with a specially developed cocktail of materials to represent the gross physical properties of the soil on Mars. The primary characteristics we were trying to simulate was that the soil is loose, it's unconsolidated, it has very little bearing strength, and it clings to the wheels.

And so that material was replicated -- or those characteristics were replicated in this sandbox. And you also notice the sandbox is tilted at 12 degrees. The rough terrain where the rover is imbedded, it's about sloped or rolled to the left about 12 degrees. And then we also have rocks that are complicating the Spirit's situation. You'll hear more about that from Ashley Stroupe.

But you can see the nature of the testing that we've been doing at JPL for several months. And what we have found is that is that what we are testing on Mars is -- excuse me -- what we are testing on the Earth is likely a worse case of what's happening on Mars, but still a very difficult situation. And we haven't found a clear solution to how to get Spirit out of its predicament. But if there is a way to get the rover out, we'll find it.

But it is a very complex situation. It is the most complex situation for either rover in their over five and a half years on the surface of Mars. We also have been dealing with other complications of the rover. One is these amnesia events that Doug McCuistion mentioned, although last night we got some good news that we did reformat our Flash memory on the vehicle, and it appears to be operating normally as of this morning.

So the plan ahead is to commence driving the rover starting Monday. That will be our first motion of the rover in over six months. And we intend to basically drive forward, which is the way we came into this. Remember we drove backwards into this, so we're now going to attempt to drive forward out of this. So at this point, I'll turn things over to one of our rover drivers, Dr. Ashley Stroupe. Ashley?

Ashley Stroupe:        Thank you, John. So we have faced imbedding events on both vehicles before, and as you heard from John, this is by far the most complicated and complex situation we've had in terms of imbedding and perhaps in terms of all of the challenges we've faced with the rover. What we typically like to do in these situations is we build a test stud and we test everything we can on Earth to try to come up with the best solution. If you still are looking at John's last graphic, number six, we have attempted to do this. We built a test stud.

But the situation is very complex, and not only do we have the tilt and the high-slip soil and the broken wheel, which we have been able to model reasonably well here on Earth, we have a complicated situation with many rocks underneath the vehicle, some of which are loose, and we don't understand exactly how they're moving. We have an unknown situation underneath the ground, this rock that may be causing the left middle wheel stall. We don't know how deep this soft material may be. So not only do we have a very complex situation, but we have not a terrific ability to model that situation on Earth.

So we've spent the last several months doing a lot of analysis, looking at the last several drives that we did on Mars, trying to understand how the vehicle performs in this material at this location with the rocks, and also trying to model what we can here on Earth. And we've been looking at this very closely and in great depth. Now, my first graphic, AS1, which is the view of Spirit photographing her underbelly, this is the largest concern that we have in terms of getting Spirit out of Troy right now. We have this rock that is apparently touching the underside of the rover.

Now, this not only can cause complications in terms of perhaps offloading the wheels so that they get less traction and causing greater friction for the vehicle trying to move across the surface, but also the rover's underbelly itself is a complicated feature, and there are both negative and positive aspects that we are worried about how this rock may interact with those features. It could get trapped in one of these concavities or may get hung up on one of the protrusions from the underbelly's rock.

And so we're going to have to be very carefully maneuvering the vehicle to ensure that the rock, if it is in fact anchored and able to support weight, does not become trapped on any of those features. So if you look at my next graphic, I'm again showing -- this is, again, the front haz cam, the view out of Spirit's front eyes, looking back at the tracks that we made coming into here. Our best plan, at this point, as John briefly discussed, is to try to drive forward, retracing our steps that we drove in. And we believe this is our best plan for several reasons.

One is that we believe that this softer material may be easier to plow through than trying to break through the crust and cut new tracks. So if we follow our old tracks out, we may be able to make better progress. This is essentially, at the beginning, a relatively flat path. We don't have to try to climb up hill to get out, and eventually it actually comes downhill and gravity may be able to be our friend. Going the other direction, backwards, is undesirable because we would have to climb up a rather steep hill to continue in that direction.

Normally, we would like to use gravity to benefit the rover, help pull it out, but unfortunately, because of the tilt of the vehicle, the primary downhill direction is further into this soft material, which might cause us additional problems if all six wheels were to become imbedded in this white Ulysses material. So our plan at this time is to try to follow our tracks that we came in on back out, driving forward, back towards the north. Of course, we've indicated how difficult this is, how challenging it is.

We have very little ground clearance under the vehicle. Wheel turns cause us to sink further into this material. And there is no guarantee that any plan we come up with is going to succeed in extricating the vehicle. And this is going to clearly be a very long process to either get to extrication or perhaps even to determine if extrication is going to work.

But, fortunately, throughout this entire period of analysis on the ground, we've been at one of the most exciting scientific locations that we have found on Mars, and we still could have a lot of work to do here. To discuss that and the situation in terms of the science of it, I'm going to now hand this off to Dr. Ray Arvidson, our Deputy PI.

Ray Arvidson:          Thanks, Ashley. If we go to the first graphic, which is entitled Site of Intense Investigation by Spirit. It's the same front haz cam view. It's a very important view, partly because it shows Husband Hill. And you may remember, if you follow the mission, we were on the top of Husband Hill several years ago looking toward Home Plate. And to actually be at Home Plate, even though we're imbedded, is still pretty exciting. And we've labeled the features on this graphic, looking north, and as you probably know, we have lots of targets that we've seen over the course of the mission.

Soils, topographic features, rocks, and it's very difficult to keep track of them unless you have a kind of common name and theme. So, for example, Home Plate is a baseball analogy. Well, on the current site, we adopted names from the Iliad and Odyssey. So, for example, this general region is called Troy, and the disturbed soils on the left wheel, facing toward the west, that area is called Ulysses. And Cyclops Eye and Polyphemus Eye are two areas where we use the rock abrasion tool to actually grind in to the undisturbed surface and measure properties as a function of depth.

So is this a nice place to be imbedded? Of course, no place is a nice place to be imbedded. But this turns out to be a geological treasure trove, in that the materials on the left, based on deploying the robotic arm and doing composition, mineralogy, and close-up imaging, the Ulysses soils are sands, they're course sands, and in fact they have the highest sulfate content of any place we've measured on Mars with either Spirit or Opportunity. And for Cyclops Eye, as soon as we ground beneath the surface, we see the same sulfate sand.

Whereas Polyphemus Eye, when we ground through the surface a number of times, we couldn't find any evidence of sulfate. We saw the salt, we saw iron-rich dust, but somehow we're sitting just astride a geologic boundary that's in between the locations of Cyclops Eye and Polyphemus Eye. So if we go from this view looking to the north, the next view, which is Adjusted Local Topography Map of Spirit's Surroundings, what we've done here is when we were to the north of this site on Sol 1870, we used the navigation cameras on the [mast] to take [stereo].

And one of our investigators, Ron Lee at Ohio State University, made a very exquisite topographic map. What I've done is take his map and I've rotated away the regional trend. This area tilts about 6 degrees to the northwest. And north is to the top on this image, and it's about 12 meters across. And I've rotated away that regional tilt to emphasize local variations. And what you can see, since black and blue is low and red is high, Spirit is shown as a black outline, we're sitting astride a circular feature that we think is an old, old impact crater, about 8 meters wide, it's about 20 centimeters deep.

And the left wheels facing to the west with this 12 degree roll on the vehicle are in the crater and we've pierced through a crust. And we've measured the crust with all of our instruments located on the arm and also with our imaging systems on the mast. The material in the crater is completely different than the material off to the right or to the east. And what's happened -- and we couldn't have told this before we drove into it because nothing was evidence from the surface view, either spectrally or texturally or topographically except for this modest crater -- but it required driving into the side of the crater, punching through the crust, exposing this loose, sandy material.

And if you've ever walked in a sandbox, it's very difficult to get traction. That's exactly the situation with Spirit. And also just by kind of bad luck, you can see the very busy topographic contours under the body of the vehicle. That's the Rock Garden. So John and Ashley have already discussed -- we've disturbed some of these loose rocks on the edge of the crater. And one of them, [belly rock], might be just touching the bottom of Spirit.

So this has been an exciting area to be in scientifically in that it's probably an impact crater, probably punctured into sulfate-rich deposits associated with Home Plate volcanic eruptions. Those have been redistributed by wind, come back as ejecta. The sulfates were produced in a water environment. They're largely ferric sulfates, but there are also calcium sulfates. So we are following the water, and we've done six months' worth of measurements within the arm workspace. But we're ready to button up and start driving on Monday and head for [points south] as soon as we can get out of this place, if it is possible to, in fact, extricate the vehicle. So let me turn it back to Doug McCuistion for wrap-up.

Doug McCuistion:    Yeah, thanks, Ray. Thanks, John, Ashley, and Ray. I appreciate your comments here. As you can tell, everybody, from the discussion that John, Ashley, and Ray put forward, Spirit is facing the most challenging situation it's seen yet on the surface of Mars. We know that a lot of people around the world have followed Spirit and Opportunity both and view Spirit with great affection, exploring the red planet along with it, experiencing the excitement, seeing new and exciting vistas, new landscapes, uncovering some incredible new knowledge about our sister planet.

So I really want everybody to be realistic here. I'd like everybody to be hopeful, but I'd also like them to be realistic. This is a much more serious situation than Opportunity had in Purgatory Dune. If Spirit can make the great escape from this sand trap -- if it cannot make the great escape from this suntrap, it's likely that this lonely spot straddling the edge of this crater might be where Spirit ends its adventures on Mars. We'll keep everybody informed, because we know everybody's interested, and we'll keep progress reports coming. But at this point I'd like to pass it to Dwayne and open for Q&A.

Dwayne Brown:        Okay, thanks, Doug, and thanks, everyone. For reporters, please hit star one to queue up in the Q&A line. And for the reporters who have joined us, again, the subject for today, to discuss attempts to free the Mars rover Spirit from soil where it's been stuck for the past six months. Again, for the queue, please press star one, and we'll wait a moment before we take the first question. Okay, we'll take the first question, and that is from Peter King from CBS News. Peter?

Peter King:                Dwayne, thank you. Good afternoon and thank you for the briefing, everyone. Some really interesting things here. And I have two questions. First of all, if Ashley could tell us a little bit about what rover parts are in the underbelly, the parts that you're really worried about.  And, finally -- I don't know who would answer this one -- I'm just wondering how long you would give it before you say that's it? Would it be two months, six months, a year before you throw in the towel if you can't get it out of there? Thank you.

Ashley Stroupe:        Yes, thanks for the question. Yeah. So the primary feature that we're worried about underneath the belly of the rover is there are two notches underneath where another part nestled into the rover. This was part of the lifting mechanism that helped Spirit get up off of the lander. This part nestled in there, and so there's a concavity in the bottom that is a few centimeters across and is much larger than the point of the rock. And if the rock were to slip in there, that's our primary concern.

Peter King:                That it would get hung up there?

Ashley Stroupe:        Yes, and that's at the front edge of the rover, and that's another reason why we prefer going forward, as that minimizes the chances of the rock interacting with that feature.

Peter King:                Thank you.

Doug McCuistion:    This is Doug McCuistion. I'll answer your second question. We sort of have, coincidentally, a natural review point in February of next year called the senior review. That's a standing process that annually we review all of the operating missions for Mars, make assessments with an independent panel of the kind of science that's still being done and the value of the science, instrument by instrument and overall, and then of course the programmatic factors come into it.

So the first -- so if we don't get out of this situation by February, we want these rover teams to have that much time, November, December, January, and part of February, to attempt to extricate Spirit. If it can't be extricated by then, that senior review will take a look at the situation and progress that has been made at that point, if any, and look at the scientific value of either continuing to try to extricate it, depending on progress, or scientific value of not attempting any longer and just remaining in place and conducting science from where it sits.

Peter King:                So it would be fair to say you have until at least February to get it out of there?

Doug McCuistion:    That would be the first point that we will officially review the progress, that's correct.

Peter King:                Thank you.

Dwayne Brown:        Thank you, Peter. And, again, for the media, hit star one to place your call into the queue. Our next question is from Joe Palca from National Public Radio. Joe?

Joe Palca:                  Thank you for taking my call. I have two questions. One is a quick one. Can you just describe what a stall means? What does it have when you have a stall event? And the second question is six months ago, when you recognized that this was the problem and you tried to do something about it, did you try backing -- or fronting out, I guess, if you want to call it that way -- retracing your steps, I guess? Or is this the first time that particular extrication maneuver will be attempted?

Doug McCuistion:    John, that sounds like good ones for you.

John Callas:              When I refer to a wheel stall, the rover keeps track of the rotation of the wheels, and you can get in a situation where a physical obstacle prevents a wheel from rotating even though you've energized that wheel. And that's what happened on Sol 1899, the last day of motion for Spirit, is that we were driving, the left middle wheel started to move but then stopped, that likely some external object is jamming the wheel, and the rover recognizes that and flags that as what we call a stall event. So it means that the wheel wasn't rotating, even though it was energized to rotate.

Then, regarding the planned motion, we had a series of motions of the rover when we originally became imbedded at this location. The rover was driving backwards, so we were driving south, and after the first indication that we had broken through this material, we actually continued to drive backwards a few more attempts. We then attempted to try to turn the rover, did what we call a turn in place, and that was unsuccessful. And then we tried driving forward, but it was what we call crabbing, which is where we turn the front wheels and the rear wheels -- there are six wheels on the rover.

The front wheels turn and the rear wheels can turn. And crabbing is you turn the front wheels and the rear wheels in the same direction to try to get some lateral motion in addition to the forward motion of the rover. That had some limited forward progress, but it also had an excessive amount of sinkage. And sinkage is one of the things we're very concerned about. Right now, we can consider sinkage as one of our consumables because if you put the belly pan of the rover on the ground, that's pretty much game over in terms of trying to get the rover out, because then you would be bearing the weight of the rover on the belly pan and not on the wheels where you need the traction.

So we were going forward, but crabbing, and crabbing down slope. And that's where we saw excessive sinkage. And so we stopped because at that point we weren't on a path to getting the rover out. So what the plan is for Monday, at least initially, is not to crab but have the wheels steered straight, so all wheels are pulling in the same direction, and to go along the tracks or the channels that we created when we came in here. So it's the path of least resistance.

Joe Palca:                  Okay. Thank you very much. Very clear.

Dwayne Brown:        Okay, thank you. Again, hit star one to place yourself in the queue. And I believe next up is Irene from Discovery News.

Irene:                          Thanks, Dwayne. Thank you. I have a couple of questions. The first is since you mentioned that you don't really have a clear idea of what's going to happen, I was wondering why you've decided at this point it's time to make a go of this. And also if you could tell us exactly when the commands will be sent and when the rover would be -- well, let's see. I guess it doesn't really matter when it's moving. I guess it matters when you would know if it's moving or not. And if you plan to kind of do this -- sort of make your plans as you go or is there a set of commands and sort of, you know, like the first five or six steps and then you'll wait and stop and see how that went? If you could just maybe break it down a little bit.

Doug McCuistion:    Ashley, would you like to take that one?

John Callas:              Tell you what, Doug, let me take a swing at these. The question as to why now, we had engaged in a very ambitious ground testing plan. And that testing -- we basically ran it to its logical conclusion. And so we've pretty much exhausted all the possibilities, all the things that we can do on the ground, and we've done a detailed analysis of that. We've done a detailed analysis of the last drives on Mars.

And so at this point, we've pretty much done all that we can do to explore this problem. And the clock is ticking here. We are concerned about the next winter. Although we think the rover can survive in its current attitude, we don't have any margin on that. The environmental conditions could get worse. A mobile rover has a better chance of surviving the winter. As far as the timing of things, we will be planning the first motion of the rover on Monday, as part of our normal tactical process for the rover.

The commands for the drive -- it will probably be a modest drive of about five meters of wheel spin. We don't expect the rover to achieve five meters, but we will be turning the wheels for about five meters. Those commands will go up Monday night. They will execute on the rover late Monday night, early Tuesday morning, and we should get the data down very early Tuesday morning. Our strategy going forward is we plan to drive and then follow each drive with a detailed analysis day.

So we'll take at least one day to look at the results of the drive, see if it's on trend to what we are expecting or if there's been any departures form that trend. And the reality is we're going to see very little motion each day, at least initially, so it's going to be a very slow process. The analogy or the metaphor that I've been fond of using -- it's kind of like watching grass grow.

You know, you wake up each morning, you open your front door, and you look at your lawn, and you try to decide when it's time to cut the grass. So we will have probably several drives interspersed with these analysis days before we can discern whether we've seen sufficient progress or whether we need to change our strategy. And our strategy will be very adaptive to where we can change direction, change steering, change any of the drive parameters with each of these drives.

Dwayne Brown:        Okay, thank you. Again, star one to place yourself in the queue. And next up is Jeff Custer from the Voice of America.

Jeff Custer:                Yes. Good afternoon. Much of this has just been answered. I don't want to sound naïve or stupid, but I'm trying to find an analogy here to how this is being done. I know you just said it's going to be very slow. But can you make it analogous to perhaps trying to get a car out of the sand? Are you rocking it at all? Are you moving forward and back? Have you tried that? That sort of thing. I'm trying to describe for listeners how this is working.

John Callas:              Let me throw cold water on that. There is practically no Earth analogy here -- no Earth analog. We are on a planet with nearly no atmosphere, with about three-eighths of the gravity that we have here on Earth. We have a vehicle that has hard metal wheels. And the rover doesn't go very fast. It only goes about 5 centimeters a second. So that's only about 2 inches a second. We move about as fast as a tortoise.

So we can't take advantage of momentum. We can't rock back and forth. We can't spin the wheels as we steer. And all the experience that everyone here on Earth has with getting their car stuck in the mud or the snow or the sand doesn't apply because there's no liquid water here that's changing the characteristics of the soil. So, unfortunately, there's no real good Earth analogy here to use for how we get it out. And that kind of speaks to how difficult it's been trying to test this on the ground and how difficult it will be to try to get the rover out.

Jeff Custer:                Okay, thank you.

Dwayne Brown:        Okay, and star one. And next up, [Bill Harwood], CBS. Bill?

Bill Harwood:           Yes. Thanks, guys. I think actually you just answered my question, but I'll ask it again anyway. There's nothing from a long-term weather standpoint that would have any effect on the consistency of the exposed soil or anything like that. I mean, where you are right now, it's going to stay that way until you either get out of it or you don't. Is that right?

Doug McCuistion:    Ashley, you want to answer that one?

Ashley Stroupe:        Well, that's probably a question for Ray, to talk about the soil properties with the weather.

Ray Arvidson:          Yeah, the amount of water vapor in the atmosphere is so small that it's not thought to have any impact at all on the consistency of the soil. We've just broken through this crust and stirred up this sandy sulfate material, and there's nothing that we can see in any of the data we collected this summer that indicates significant changes and nothing in the [dynamic] that we've thought through that would indicate that there would be any change in the soil properties.

Bill Harwood:           Thanks, and one more quick one for me. You guys mentioned that you can probably get through this winter, even though it's close. For Ray, maybe, from a science standpoint, if you can't get out, I mean, I would assume at some point, other than just serving as a weather station, that there wouldn't be that much more science to gain. I was just wondering, you know, you were talking about this is a geological treasure trove, how long do you think it would take you to mine it if you can't move?

Ray Arvidson:          That's a good question. Weather station is important, because we can track sun and opacity, we can look for clouds, we can get the temperature profile of the atmosphere and we can look for changes between the surface and the atmosphere due to wind. But here's one of the interesting tidbits.

                                    We've been on the surface so long, so far beyond our nominal mission, that the cobalt 57 source and our Moss-Bauer spectrometer, which is radioactive, has been through so many half-life's and it's so depleted that what took us about three hours at the beginning of the mission in 2004 now takes us days.

                                    So we haven't by any means finished all the measurements that we could, and the work [volume] that has this geological boundary with the sulfates to the left and the [normal] materials to the right. So there's still a lot of science to be had from the current location. But we're itching to get started to get out of this place and head south to those two new volcanoes, von Braun and Goddard.

John Callas:              Yeah, and, Ray, this is John Callas, I might add to that. There's a whole list of geodynamic measurements that we can use that you need a stationary vehicle to track the radio signals to explore the geodynamics of Mars. And we also have an ability to do a crude seismometry with the rover. So those are both long-term objectives, new things that the rover can do.

Bill Harwood:           Thanks a lot, guys.

Dwayne Brown:        Thank you. Next up will be Air & Space Magazine. Mike Klesius, and forgive me if I botched your last name. Mike?

Mike Klesius:           Quite all right. Thank you very much. I have a broader question for John and Ashley, but if Michael and Ray would like to add any thoughts, I'd welcome that. I'm very intrigued by the powerful commitment and the emotional bond that's obvious among all of you on the rover team for these two machines, which is all the more poignant as the rovers begin to age. When you came onto the team, did you anticipate this intense devotion and affection that the team has developed for the rovers? And how has that been affected lately by Spirit's current situation?

Ashley Stroupe:        This is Ashley. When I came onto the rover project, we were already four months past the nominal prime mission. And I think it's largely the time that people have devoted to this project that has really created this bond. We've now been working with these rovers -- some of us now for 10 years, and myself for 5. So, no, I don't think that I personally anticipated this. I didn't know that I'd have the time to get to know the rovers this well.

But it certainly has created a tremendous bond. In many ways, we think of these rovers kind of as our children that we've sent off into the world way too early, and like most parents when their kids go off to college, we can't reach out to help them every time that they really need us. So it really is a bond, not just between us and the rover, but also the team has become a very close family as well.

Ray Arvidson:          This is Ray. I've been in it since the beginning, and it's Steve Squyres and I -- Steve is of course the PI from Cornell and I'm the deputy PI. We joined forces because we wanted to get this mission going. In fact, it took, I think, five different proposals to finally get the payload on the Spirit and Opportunity rovers. And it's been, boy, a great ride. So we thought we'd operate for 30 days or 90 days or 180 days. I had no idea I'd be involved in a press teleconference five and three-fourths years into the mission.

My perspective is this: rovers are so difficult, [landed] operations are so difficult, it's so hard to get onto the surface of Mars and to operate, that there's still an enormous return on investment to get both from Spirit and Opportunity that will even build on the enormous amount of information we've already collected. So we're working really, really hard to make sure that we have the best possible approach and the best possible advice and team, which we have, to get out of the current situation and head south.

Dwayne Brown:        Thank you. Next up is Dick [Kerr] from Science Magazine. Dick?

Dick Kerr:                 Thanks. I'm looking at image AS1, Spirit Photographs her Underbelly. It looks like this pyramid rock is in contact with the underbelly. Is that so? And if so, how much weight do you think it's bearing? And how much of a problem is that to extrication?

Ashley Stroupe:        Yes. This is an excellent question. So this image was actually taken with the microscopic imager, so the resolution of these images is not precise enough for us to be able to determine with absolute certainty whether the rock is touching the belly or if it's just below it. We do believe that it is touching, but because of the shape of the rock, it appears at this point to only be barely touching.

We do not think that it is significantly holding the weight of the rover at this time. But certainly we expect that to become a possibility as the rover progresses and starts to sink further into the soil. And that is a serious concern that we have. We did some tests on the ground where we put the rock right at the center of gravity and offloaded most of the weight onto that rock. And we did basically reduce motion to zero at that point.

So that rock as a threat to offloading the wheels and reducing our traction to zero is actually another serious threat of the extrication, and we are, in addition to trying to maneuver that rock around the hazards on the bottom of the rover, we are going to make every effort to make sure that that rock does not come close to the center of gravity.

Now, one thing I do want to point out is some of our preliminary science analysis has indicated that this rock may not be actually fixed. We know we've moved it, and it may actually not be very stable. And the best case scenario would be, of course, that as we move, it just tips over. But at this point we still have to treat it as a very serious hazard.

Dwayne Brown:        Thank you. Next up, Andrea Thompson from space.com.

Andrea Thompson:  Yes. I was wondering how nerve-wracking has this whole months-long process been and how nervous are you guys going into next week and sending these commands up and seeing what happens?

Doug McCuistion:    I wouldn't say it's nerve-wracking. It's been an arduous process, and of course all of us are very concerned about the rover. But we have a skilled, trained team, and they're going to do what they know how to do best, so we're in good shape. We're ready to roll on Monday.

Andrea Thompson:  All right.

Dwayne Brown:        Thank you. Sally from the Planetary Society.

Sally:                          Hi, thank you. I've got a couple of questions. First of all for Ashley. Going into this long-awaited extrication process, I would like to know what your emotions and thoughts are. Do you feel pressure? What are you feeling in the still of the night with these robots that have become real team members?

And for Ray, you've for a long time been confident that Spirit has only been mobility impaired and not stuck. And I'd like to know -- it sounds a little bit like an obituary today, and I'm wondering what's changed for you, if anything. And if it has, can Spirit still tell and fill out the geologic story from the position it's in now? Thank you.

Ashley Stroupe:        Okay, so to answer your first question, we are very emotionally invested in these vehicles. And it has been a long process, and so we're all of course very hopeful that we will get out of this. Spirit has certainly surprised us on many occasions with doing amazing things that we didn't necessarily expect to happen. But of course we're very concerned.

These vehicles are tremendous assets, and we are concerned about the possibility of perhaps Spirit's roving mission coming to an end. I think the worst night is going to be that first night on Mars. I think a lot of us who are waiting for that plan to execute will not get a lot of sleep. But this whole process, I think, regardless of the outcome, none of us can have anything but primarily positive emotions about this mission.

It's been such an incredible experience, we've come so far beyond what we thought we would accomplish, so even at some day when these rovers come to an end, it will be -- perhaps the best word was used earlier, which is bittersweet. We're so proud of them and we're so thrilled to have been a part of this project, but we will be sad to see them go. But we're not ready to let go yet, and we don't plan to let go yet. We still have a lot of work to do.

Sally:                          Thank you.

Ray Arvidson:          And, Sally, with respect to the second pair of questions, as we've discussed -- when we decided not to drive and to a stand-down on Sol 1900, we were still making progress on the last drive till the left middle wheel stalled. So we're not actually formally stuck. And that's why I call it mobility impaired. Are we in a bad situation? You betcha.

In the fact that there might be some combination of soils and rocks that are on the underbelly, that we have a 12-degree roll to the west or left with the left wheels imbedded in that soft sand, that the right front wheel doesn't work. It is a tough situation, worse than any of the situations that either Spirit or Opportunity have been in before. The probability of getting out, I can't tell you. I'm an optimist. I'm looking forward to getting to von Braun and Goddard at some point during this mission.

And the fact that we've been going for five and three-fourths years rather than 30 days or 90 days or 180 days suggests that this vehicle is resilient. I'm not sure we're going to get out though. And when we know the whole story of the inner basin and the explosive volcanism that involves steam and magma, putting the von Braun and Goddard story into the whole situation would really strengthen our kind of regional understanding of the processes.

We do already know, based on the sulfate deposits we've been measuring in Troy and the three other places that we've encountered, together with Opal and Silica discovery from last year, that this place was warm and wet. You know, there were steam eruptions, there may have been hydrothermal pools back billions of years ago. But it would be nice to extend that to a more regional basis by heading south to these beautiful volcanic exposures that we call von Braun and Goddard.

Sally:                          Thank you.

Dwayne Brown:        Next up is [Craig Covault], spaceflightnow.com. Craig?

Craig Covault:          Hi, thanks. I think your answer to Sally's question pretty much got mine, but one question out of two I had here -- the first one is similar to Sally's -- to put the sulfate discovery there in context with sulfates you've seen elsewhere with either rover. And the second, engineering question is really a Hail Mary. I realize this. But earlier in our briefings here, months ago, there was some discussion of maybe as a very last, last resort, using the arm to provide a little bit of leverage. Is that at all still in the plan? Or would you really not do that simply to preserve it for [science in this stuck location]?

Ray Arvidson:          Well, Craig, the uniqueness of this site is twofold. First, we've never been at such a juicy site for such a long period of time. There's always been pressure to continue to move to go to new sites. Here we've been making measurements for six months, so even though the cobalt 57 on the Moss-Bauer is depleted, we've had time to make key measurements. So getting kind of a complete view on the left, the middle, and the right sides of the vehicle has been important.

The other point is that these deposits are layered. You know, we've broken through a crust into the soft material underneath on the left, and we've examined that crust in incredible detail by looking at the layering in the walls of the Ulysses material in the [trench]. And the top part of the crust is different than the middle, is different than the bulk of the sulfates. And it seems to be -- and we're still working through this -- but the crust has more insoluble sulfate species than the bulk of the material.

And that suggests that there's been some reprocessing of the more soluble minerals long after Home Plate was extinct. And that's probably associated with the more recent water cycle. And of course during periods when the tilt of the spin axis is high, the Spirit and the other sites toward the equator tend to have a lot of snow and ice on them.

So we're looking into the possibility that that part of the hydrologic cycle is wrapped up in the deposits that we're seeing. And as to whether or not we can do anything with the robotic arm, the instrument deployment device, we're only going to get about 70 newtons of force. And that's not enough to do much at all in terms of moving the rover or helping things out.

Dwayne Brown:        Okay. We're coming up at the top of the hour. We're going to extend it for a few minutes, so if you have any questions for the last call, please hit star one. Next up is Nancy [Atkinson] from the Universe Today. Nancy?

Nancy Atkinson:      Hi. Thanks for taking my call. Last week, we saw that the wheels were [pivoted] and it looked like maybe you were successful in dislodging some of the materials that were inside of the rims. I was just wondering if that was the case. And also if you could just explain why you pivoted the wheels.

Ashley Stroupe:        Yeah. So a few days ago -- the last motions we did were, as we described previously, this crabbing downhill motion where the front and rear wheels were steered 30 degrees to the left to try to take partial advantage of the gravity component. So they were steered in that direction. We did a couple of days ago steer them straight in preparation for our drive. This did disturb some of the soil. The wheels that were imbedded are still imbedded, and so there's still a lot of material in the interior of the wheels, but some of that was shifted and displaced during the steering and driving motions that we did on Mars. Was there a second part to that? Did that fully answer your question?

Nancy Atkinson:      Yeah, that's great. Thank you.

Dwayne Brown:        Okay. We have time to take two more questions, and the first one is Emma from Pasadena Star News.

Emma:                        Yeah. I wanted to check in and ask how the solar panels are doing, if they've been accumulating dust over the past six months, and if that's a factor in trying to extricate Spirit.

John Callas:              Yeah, this is John Callas. Yes, dust on the arrays is a factor here. When we became imbedded back on Sol 1899, we were actually quite concerned because at that point over 70 percent of the solar arrays were blocked by dust, so we were only getting 30 percent performance. And we were very concerned that we couldn't survive the next winter with arrays that dusty. But coincident with the imbedding is we had a substantial cleaning of the solar arrays, and that came right at the perfect time because that took the pressure off of having to get the rover somewhere.

Since then, we have had another smaller dust storm that did dust the arrays up a little bit, but right now they're at about 60 percent of performance, only about 40 percent obscured. And that is, if we trend that to the next winter, we should just be able to make the next winter. However, if things get worse, if the environmental conditions change, then we do have a rover that's at risk. And as I mentioned earlier, a mobile rover could better deal with that by changing the rover tilt to tilt the solar arrays more to the north to mitigate some of that. So we're okay now, but we have no margin on that.

Emma:                        Okay.

Dwayne Brown:        Okay. If someone can mute their mic. We're hearing some background noise. And last up will be Emily from the Planetary Society. Emily?

Emily:                        Hi, all. This question is for Ray, the optimist. Assuming that you do get free, I'm wondering if the analyses that you've been doing on Earth will allow you to avoid any future sand traps like this one or if there's anybody on the science team advocating for going back toward terrain you've already traversed and known to be safe.

Ray Arvidson:          Oh, good question, Emily. So we've thought a lot about traverseability and hazards. The hazards are rocks, the hazards are loose soil, the hazards are slopes. And this particular sand trap, just one could not predict based on any of the spectral information and any of the textural information other than the topography. So one thing to do is to make sure we stay out of circular pits and drive around them in addition to staying on reasonable slopes and areas that aren't as rocky as other regions.

And in parallel, what's going on is we have some of the world's experts now involved in trying to do simulations of drives, in which we take the topography in the [forward] direction before we drive, in which we take rocks, and in which we take different models of soil subsurface properties, and we actually simulate dynamically the drives across surfaces and then try to find the optimum path to get from point A to B without getting sunk in the soil or without getting too much slip.

And providing that information to the rover planner so that they can have another piece of information to really lower risk in terms of future drives. And I think the team is pretty much committed to continuing going south because von Braun and Goddard, going through South Valley, is the big science payoff.

Emily:                        Thank you.

Dwayne Brown:        Okay. Just a reminder to the media on the line here, the replay number is 888-820-8959, 888-820-8959, and that replay of this telecon in its entirety will run until November 20. Please go to nasa.gov/rovers. The rover team will be very transparent in letting the public and you guys know the status, so they will be having regular updates via the web.

Also, at the appropriate time, we will have the media telecoms as progress and activities progress. For the international replay, 800-873-2062, 800-873-2062 for the international replays of this telecon. And, again, for the TV folks, we are running video and animation on NASA Television. Thank you all. God speed to the Mars rover team. And I will now turn it over to the operator to take us out.

Media contacts:
Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown 202-358-1726
NASA Headquarters, Washington