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Mission Update by Steve Squyres

(Return to archived mission updates list)

July 2005
July 29, 2005

It's been a good week on both planets.

A lot of the action was here on Earth this week. The science team for this mission has been together for about a decade, and during the first eight months after we landed we were all living and working together in Pasadena. So we know one another pretty well. Since last September, though, we've all gone back to our home institutions, and we do flight operations remotely. While we talk to one another by phone and videoconference daily -- often for many hours a day -- we hardly ever see one another face to face any more.

It all works fine for flight operations, but there's no substitute for being in the same room together when it's time to really sit down and argue about the science. So this week the whole team gathered here in Ithaca for what amounted to a three-day MER science fest. I try to do a pretty good job of staying on top of all our discoveries, but still, it was pretty eye-opening to sit in a room and listen for eight hours a day to new analyses of all our results. We're really getting some serious science done these days, with a large set of papers about Meridiani just accepted for publication by Earth and Planetary Science Letters, and another batch of papers about Gusev being prepared for the Journal of Geophsyical Research. There aren't any really big discoveries in these papers that you haven't heard about already... we're just adding the richness of detail that a careful examination of the data over many months allows for.

On top of the science, it was also just really good to see everybody again. The team got very close during all those months of living on Mars time. Things change... one of our team members passed away a few months ago, and several babies have been born. In fact, there were two little ones less than a year old at the meeting. So life goes on. We've gotten to be a bit like a big, sprawling family, I guess.

One of the most impressive things to me about the whole meeting was how effective our remote operations procedures have become. We'd stop the science talks for a couple of hours each day to do tactical planning meetings for each rover, with people spread all over the place. As just as one example, at Tuesday morning's Opportunity SOWG meeting, there were eighty scientists in a hotel conference room in Ithaca, all making suggestions for what to do. The Payload Uplink Leads, who are the people who write commands for the instruments, were on campus at Cornell and at Arizona State near Phoenix. The guy at the controls of the computer screen we were all watching was in Boulder, Colorado, the engineers were all at JPL, and the leader of the whole meeting was in Flagstaff, Arizona. It all worked, and we got a good command load put together in time for the uplink.

So that was Earth. On Mars, Spirit spent the week working over the fantastic outcrop called Voltaire that we found last week.

You only have to look at the pictures to see that the Voltaire region is one of the most interesting places we've found on Husband Hill. There's an incredible amount of variety here, including some things we've never seen before. Voltaire itself is a new rock type for us, composed of very large, often angular grains embedded in a fine-grained matrix. We're just starting to get a handle on what it's made of, with some key APXS and Moessbauer data coming down this weekend. The first first spot on it that we looked at was named Descartes, and the second one, which we're on now, we named Bourgeoisie. We're probably going to finish up Bourgeoisie over the weekend, then bump to the right a little for some Microscopic Imager work on another rock, and then -- probably -- do one more full APXS/Moessbauer/MI workup on one more rock that both Mini-TES and Pancam are telling us may be something else we've never seen before. This is turning out to be a surprisingly target-rich environment, and we've got to work it for all its worth before we move on.

After that, we head toward the summit. The strong feeling on the team is that we should try to go for what we've been calling "Summit 2", which is both closer to us and a little bit higher than Summit 1. If we get to the actual summit we'll probably want to take a fairly substantial panorama there. But the thing we're all most eager for is the view that we'll get off the south side of the summit, down onto lower flanks of Husband Hill that we've never seen before. We're not really convinced that we'll get a good view of this stuff from the true summit, so if we do make it to the top, we may not linger there all that long. It's been an interesting time working on Spirit these days, as we try to find the right balance between our eagerness to get moving up the hill and our excitement over all the new stuff we're finding at Voltaire.

And then there's Meridiani, where Opportunity continues to work her way southward. Many people at the meeting were commenting on how ironic it is that the rovers seem to have switched roles over the past six months. For much of the early part of the mission, Opportunity grabbed all the headlines while Spirit struggled gamely across the lava blocks of the Gusev plains. Today it's the other way around, with Spirit making discovery after discovery on Husband Hill and Opportunity struggling gamely across the sand and the blueberries of Meridiani. The big news, though, is that we're really starting to see serious amounts of bedrock with Opportunity now. The farther south we've gotten the more common these little outcrops have become, and as we look southward we see more of them still. For a long time, we were worried that the bright, mottled stuff that we see from orbit in the etched terrain might just be dust. If that were the case, our chances of ever getting to Victoria Crater might be pretty close to zero. With all this rock we're seeing, though, it has greatly buoyed our hopes that we'll find firmer ground, better driving, and more science as we work our way into the mottled stuff. It's a good feeling.

So that's the latest. I should probably mention that it'll be more difficult than usual for me to do these updates for the next five weeks or so. I've written a book about MER that comes out next week, and one unavoidable consequence of authorship these days is the "book tour" -- a string of appearances hither, thither and yon to tell the world about the book. So for a little while I'll mostly be bopping around the US, Australia and the UK, popping up here and there and trying to follow what the rovers are doing from a distance. I'll do the best I can with updates during that time, and I should be back to doing daily flight ops again starting the second week of September.

July 21, 2005

Spirit has had a pretty remarkable week. Back when we were climbing the lower reaches of Husband Hill, getting anywhere was a real struggle. The terrain wasn't all that steep, but the soil was very loose and slippery. Five meters of forward progress was a good day, and some days it was less than that as we slipped and slid and clawed our way up the slope.

Fast forward eight or nine months... we had a drive this week in which we covered five meters vertically. That's five meters of elevation gain, over a drive that totaled something like 30 meters horizontally. It's amazing to me how solid the ground has gotten as we've begun to approach the summit of the hill. The terrain is pretty steep here, and I thought this could be one of the hardest parts of the climb. Instead, Spirit has been scampering up it.

Covering all that ground, of course, offers the chance to find new things, and if you've looked at the most recent images you've seen that we've happend upon yet another nice outcrop... a pretty big one this time. So we're going to stop and work it over a little bit before we move on.

As always, we've been having fun lately naming things. In our big Independence Day panorama, all the rocks were named after different kinds of fireworks. Since then, starting around July 14th, we've been using mostly French names, in honor of Bastille Day. So the outcrop we've just arrived at has been named Voltaire. After we're done with Voltaire, we'll resume the push to the summit. The plan is to name the rocks we begin to see next after famous mountaineers.

Meanwhile, over at Meridiani, you look at the lastest pictures and they're enough to make you think we're ready to shout "Land Ho!". We're covering a solid 30 meters a sol with our new drive techniques now, and as we look around us we're starting to see more and more little tiny outcrops of rock. The big expanses of rock we're hoping for aren't in view yet, but still... we feel like sailors who have been at sea for months, starting now to see driftwood and bits of seaweed that are telling us that solid ground may not be far over the horizon.

Oh yeah, and we've just had another one of our lovely "cleaning events", with gusts of wind sweeping dust off of Opportunity's solar arrays. So both rovers are now in very solid shape power-wise. It was a good week on Mars.

July 15, 2005

I'm really sorry it's been so long since I've done an update! I try to do them at least weekly, but occasionally the workload just gets to be a little too much.

We're making some real progress at Meridiani. Our little jog to the north revealed a good southward route on the eastern side of Purgatory Dune, so that's what we went for. Since then we've been making steady southward progress, and as of now we're almost 90 meters south of Purgatory.

Driving in this stuff is an interesting challenge. We are literally in a maze. The easiest going is to stay within the troughs between the ripple crests, which run roughly north-south. So the best way to make southward progress is to follow a trough until it peters out, make a "lane change" to a nearby trough, and continue onward.

But then there's the issue of the "Erebus Highway". This is a stretch of light-toned terrain that we've seen from orbit, and that we're guessing may have some exposed bedrock in it that'll make for easier going. We also like the idea of getting to bedrock from a science perspective... it's been a long time since we've looked at any rock with Opportunity.

But there's a catch. The entrance to the Erebus Highway is not straight south of us, along the troughs... it's a bit off to the east, on a heading closer to 160 degrees or so. That means that in order to get to it, we'd have to head off cross-country, going up and over quite a few ripple crests. That's do-able, but it's also a lot slower than just bombing straight south down a nice trough.

So: If we do head for the highway, we make slow progress for awhile, but maybe we get to a better route to Erebus Crater. If we head down the troughs instead, they take us at a pretty decent speed directly to... Erebus Crater. So it should work either way. We're planning the weekend drive as I type this, and after a bit of discussion we've decided to stay for now in this nice wide trough that we've found, and try to get as much southward distance within it as we can. Whether or not we're actually going to "hit the Highway" is an open question at this point, but Erebus isn't too far off either way you cut it.

And have you noticed how the terrain seems to be changing as we get south of Purgatory? Fewer tall dunes, more pebbles in the troughs, even what might be tiny outcrops of bedrock? I don't want to jump to conclusions, but the driving definitely looks a little nicer here than it did a hundred meters back.

Over at Gusev, Spirit has had a great couple of weeks. During our ascent of Husband Hill we stumbled fortuitously across a very cool outcrop of layered bedrock that we named Independence Rock. We've thoroughly worked it over with all of the arm instruments now, and it's very strange stuff... one of the oddest things that we've seen at Gusev. It's not like Peace and Alligator, and it's not like Methuselah either. I'm not ready to go into much detail here about the chemistry and mineralogy yet, since we're still chugging through the data. But it's clearly highly altered, and it's got an unusually low iron content, which isn't something we've seen much of before.

The low iron is interesting and very cool, but it also slows us down a bit. Our Moessbauer spectrometer tells us what iron-bearing minerals are in a rock, and the more iron there is, the stronger the Moessbauer signal. So when the iron content is low, like it is in Independence, the Moessbauer signal from the rock is weak. And when the signal is weak, we have to take a longer measurement to be able to get the information we want from the rock.

The other thing that's making Moessbauer measurements tough these days is that the radiation sources in the instruments are getting pretty weak. Each Moessbauer instrument has a tiny nugget of radioactive cobalt-57 in it that we use to irradiate the target with gamma rays. The half life of cobalt-57 is 271 days... in other words, every time 271 days goes by, the strength of the source is cut in half. Back when we thought the mission was going to be 90 days long, this wasn't a big deal. But we have now been on Mars two entire cobalt-57 half lives, which means that our Moessbauer radiation sources are now only one-quarter the strength that they were when we landed. Combine that fact with the low iron content in Independence and we had to do a Moessbauer measurement on it that was four sols long.

We're done with Independence now, and we've resumed the climb. The ground is real solid here, and the climbing is good. I still don't know if we'll reach the summit or not, but the recent progress has been excellent. The coming week may reveal a lot.