Mission to Mars

(Return to archived mission updates list)

October 2005
October 24, 2005

Opportunity was the star of the show this week. One piece of news, of course, is that we're really driving again. Erebus is a nasty place to work, with widely-separated outcrops of rock separated by lots of dunes and drifts, some of which look like they could be real rover-eaters. But we're getting the hang of driving in this stuff, and we made some very solid progress toward the Mogollon Rim this past week.

On top of that, Opportunity has stumbled onto something really new and different lately... the blueberries seem to be gone! We've been seeing smaller and smaller berries in the rocks since all the way back at Strawberry and Lemon Rind, two of the rocks we looked at before we got on the Erebus Highway. So we've known something was going on for awhile. But if you look at the most recent images -- the front Hazcams from Sol 617 are a great example -- you'll see that the rocks here appear to be lacking berries altogether. We can't say that they're gone completely... we really need some better imaging, including MI images, to do that. But this sure doesn't look anything like the berry population back at Eagle or Endurance.

We haven't done any IDD work on this stuff yet, but that'll be coming soon. And it's such a new discovery that it's too early yet to say exactly what it means. But one possible guess at this point is that we have moved "up section" in geologic terms -- to rocks that are higher up in this stack of layered sediments -- and that the rocks at this level never experienced the concretion-forming process. It's an interesting hypothesis with interesting implications, and it's also one that could explain a few other odd things we've been thinking about ever since Eagle crater. We're not jumping to any conclusions, but everybody is itching to get the IDD onto this stuff as soon as we get the chance.

At Gusev, Spirit is working her way nicely down the upper portion of Haskin Ridge. We're within a few tens of meters of the top of the step now, and we've stopped for a bit of IDD work on a new outcrop called Kansas. No idea what it's made of yet, but we should get some clues over the next couple of days.

October 16, 2005

It's been ten days of high drama on the Spirit side of the planet.

As we were completing the Everest pan, we decided that the one thing we still had to do before leaving the summit was some IDD work on Hillary. Easier said than done, it turns out. What was happening on Mars may have looked fairly benign as the Hazcam images were coming down, but this IDD campaign was one of the hairier things we've ever tried with either rover.

The initial approach wasn't too bad. We were on familiar ground, and the rover planners managed to put Hillary within reach of the arm with just a couple of very sweet drives down off the summit. But our position at the end of that second drive looked pretty dodgy: A very steep slope (we were pitched up more than 27 degrees) and some very loose-looking crud under the wheels.

In a position like this, nobody was real comfortable about deploying the IDD, because we had no way of knowing how stable the vehicle was. Swinging the IDD out changes the center of gravity of the rover, and if you're on really unstable ground that could cause unanticipated motion of the vehicle, potentially whacking delicate components (like the instruments on the arm) into rocks.

So, before deploying the IDD, we did a set of "wheel wiggles"... turning the front and rear steering actuators back and forth, just to make sure the thing had settled properly. Unfortunately, with each wiggle, the rover moved! It shimmied back down the slope something like 2 cm with each wiggle. A little motion isn't unexpected when you wiggle wheels on a slope this steep, of course, but it wasn't exactly a confidence-builder. We weren't sure whether it was safe to put the instruments on Hillary or not.

So what to do? This was a crucial rock, and we really didn't want to back off from it. At the same time, we had to know whether or not it was 100% safe to put the IDD instruments onto it. The scheme we came up with, in a very long day of planning, was to deploy the IDD partway -- to a position where it was extended, but where there was zero chance of the instruments touching the rock even if the rover shifted. Then, the next morning, we'd see how much of a shift there had been, and make a go/no-go decision regarding the actual measurements.

The go/no-go came last Saturday, with members of the team calling in from airports, cars, everywhere (I was in my car on the way to Boston at the time). The news was great... the rover tilted only 0.005 degrees as a result of deploying the arm, and it did not slip by any discernable amount. So we were go for the deploy, and over the next several days we did two detailed IDD campaigns on Hillary... one at a spot called Khumjung and the other at a spot called Namche Bazaar. It all worked, and we got everything we hoped for out of it.

The science result, in a nutshell, is that the summit rocks are nearly indistinguishable from rocks we found near Jibsheet, hundreds of meters from here. That includes how they look, and also what they're made of. And the rocks here are tilted at a very different angle from the ones at Jibsheet. All in all, it was a crucial piece of the puzzle in trying to work out the geology of Husband Hill.

From where I sat, the Hillary campaign was one of the MER uplink team's finest hours. In a situation like that, perched on loose ground at a 27-degree angle, at the summit of a mountain on Mars, we're right at the ragged edge of the vehicle's performance capability. The team thought it through carefully, kept the vehicle safe, got the science, and in the process nudged outward the performance envelope of what you can achieve with a robot on another planet. It was a pretty cool thing to watch.

So now we're on our way again, starting the descent of Haskin Ridge. The first move was a very nice, pulling back from Hillary, shooting a little more data on it, and then driving 41 meters to the east. We're on new ground now, and we're going to be seeing some new sights. Spirit has really been on a roll lately.

Unfortunately, it was a week of frustration over on the Opportunity side of Mars. You get good luck and bad luck in this game, just like anything else, and we've had more than our share of bad luck at Meridiani lately.

First there was the unexpected drive partway into something we called Telluride Dune, a little drift that was nasty enough that it triggered our slip-check alarm and stopped a drive. Fair enough; that's the way things are supposed to work when the going gets dangerous in this kind of terrain. No sooner did we back out of that, though, than we got hit by another of the mystery reboots that Opportunity has encountered a few times in the past several months. This was different from what hit us on Sol 596... that one we understand and can trace to a simple bug in the software. But this one we don't understand yet, and it cost us a couple more sols. And then, just as soon as we recovered from that, we had a minor problem at one of the Deep Space Network stations and lost two more sols. Not a good week.

Each event was benign individually, and each was unrelated to the others. So it really was nothing other than a run of bad luck, for a rover that's had more than its share of good luck. Still, the end result was a week in which we made zero progress toward the Mogollon Rim, so we're going to try to really get things moving in the week ahead. One good piece of news is that this latest mystery reboot was almost identical to one that happened a couple of months ago... and somewhere in that fact may lie the clue that'll help us figure it out. The reboots do no harm to the vehicle, and we've gotten very good at recovering from them. But they cost us sols when they happen, and that's never a good thing. So we're working hard on this one.

October 4, 2005

Sorry it's been a little longer than usual since I've done one of these... we had a server down for a couple of days.

Spirit's doing well. The big event of the past week, of course, was that we finally reached the true summit of Husband Hill. There are several rocks up here that we've had our eyes on for possible IDD work, including ones named Whittaker, Tenzing and Hillary. But first we had to climb to the highest point on the hill, to get the lay of the land around us and to take some images that'll let us determine the tilt (what geologists call "strike and dip") of the layers in the summit rocks. And rather than name the single highest rock on the hill after any particular mountaineer, we simply called it "Everest".

So that's it for the mountaineering names. Don't ask me what names we'll use if we ever get to the summit of McCool Hill!

While we were on top, it made sense to bang out one more big Pancam panorama... which we called the "Everest Pan". It's coming down now, and it's going to be quite a picture once it's all stitched together.

Having looked at all the summit rocks, the one that we like best for IDD work is definitely Hillary. So right now we're driving back around to the face of Hillary for what should be a pretty solid IDD campaign there. And with that, the summit campaign on Husband Hill should be done, unless something unexpected pops up. The seasons are changing, and it's time to get a move on.

The big news, I guess, is that we've decided where we're going to go next. We've been studying possible descent routes for a couple of weeks now, and we've settled on one, at least for the first part of the descent.

Extending eastward from the summit of Husband Hill is a broad ridge that we've named Haskin Ridge. It trends ENE from the summit, does a little dog-leg to the right, and then trends ESE for a bit. Right at the dog-leg there's a pretty steep step, which we're not certain we can get down. So we're going to descend the upper portion of the ridge, right to where the step is, and assess the situation. If we can see a safe route, then we'll continue down onto the lower portion of Haskin Ridge. If not, then we'll think about what to do next! But either way, we should get a good view of the East Basin, which is something of a mystery at the moment. And we all think our chances of finding a way down that step are pretty good.

If we can get down onto the lower part of the ridge, we'll eventually hang a hard right turn and head south, toward Home Plate, crossing some interesting-looking terraces and passing just to the east of a dark patch of sand as we do. But that's for the future. Right now our focus is upper Haskin Ridge, and whatever the view is going to be from the top of that step.

I should also mention that we've just given some interesting names to the rocks just east of the summit: names like "Montagsdemo", "Nikolaikirche" and "Wiedervereinigung". Yesterday was the Tag der Deutschen Einheit (German Unity Day), celebrating the re-unification of Germany. We have a lot of German scientists on our team, and two of our instruments -- the Moessbauer Spectrometer and the APXS -- came from Germany. So to celebrate the day, we gave a number of rocks names inspired by German re-unification. You can find more information here.

Over at Meridiani, Opportunity is doing fine. She gave us a little bit of a scare a week or so ago, returning no data at all for 24 hours. I of course was having high-stress flashbacks to the big anomaly we had on Sol 18 of the Spirit mission, but as it turns out everything was just fine. What really happened was that we had been hit again by a benign little software bug that had also given us trouble twice before, on Spirit sols 131 and 209. This time it hit us at just the wrong moment, the result being that we got no data at all for a sol. We fired up a high-priority comm window first thing in the morning (Mars time) on Sol 597 -- at about 5:00 AM on the east coast of the US -- and Opportunity woke up smartly and greeted us with a smile. However stressed-out we were here on Earth, on Mars things were just fine. Sometimes I think these rovers are smarter than we are.

So Opportunity continues westward, picking her way carefully along the outside of Erebus crater. This is treacherous stuff we're driving through, as a look at the Sol 603 Hazcams will show. But we've got our driving safeguards on, and Opportunity is able now to sense when her wheels are slipping and stop moving before we get into another Purgatory-like predicament. It's a good thing.

As the rover moves forward, we're in the process of starting to plan what we call the Erebus campaign. Getting some vertical rock here would be great, if we can pull it off, and we're going to try. But above all we want to get past Erebus quickly and continue on our way. Victoria crater beckons, and whether we can reach it or not, we have to try.