Dirty Dozen Wheels Down

Categories: Essays Mars Retrospections

These martian chronicles feature an insider’s view of science planning on the surface of Mars , as reported in the science diary of principal investigator, Steve Squyres.

Follow Martian Chronicles, Parts 1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 10 * 11 * 12 * 13 * 14

January 4, 2004

We’re down!

Principal investigator, Dr. Steve Squyres, Cornell University, describes Mars surface operations Credit: NASA-TV

Spirit touched down in Gusev Crater this evening. We landed with the lander’s base petal down, and so far every indication is that she’s in great shape.

Another two hours and we’re hoping to see the first data relay through the Mars Odyssey orbiter. We’ve got a long night ahead of us…

January 5, 2004

What an amazing couple of days! Spirit is alive and well in Gusev crater. We’re going into our second night on the surface as I write this, and everything is going amazingly well. You’ve seen many of the first low-resolution Navcam images, of course, on the JPL web site. Gusev looks like it’s tailor-made for our rover, with plenty of small rocks to look at, and excellent terrain for driving. We’re already talking about where to go after we egress, and the bulk of opinion so far is that we may want to head toward a feature that we’ve named Sleepy Hollow. I’ll be talking more about that at a press briefing later today. I’ll also be presenting the results from the first post-landing health checks of the Microscopic Imager, the APXS, and the Moessbauer.

I can’t tell you how much I and the whole team appreciate all the messages of congratulations we’ve been receiving. Those of you who have watched this site for awhile now know that it has been a very long road to get to this point. Of course, we’re not breaking out the champagne just yet. The real mission doesn’t begin until we’ve got six wheels in the dirt, and that is still something like a week away. But it’s a good time for our science team, a good time for NASA, and a good time for the exploration of Mars.

January 9, 2004

The path of Spirit from Gusev Crater to Columbia Hills
Credit: NASA/JPL

Wow, what a sol! We just finished up Sol 5, and from a science standpoint it was maybe the best one yet. It’s 9:30 PM in Gusev crater as I write this (at 6:00 AM in Pasadena), and Spirit is sleeping soundly. We got a ton of new Pancam data down today, but the big news is that we’ve got the first batch of Mini-TES data processed now. It’s fantastic. Phil Christensen and his team have made a beautiful map of afternoon temperatures near the rover. You can see the soil glowing a warm color, with cooler rocks scattered around. It’s just like when you go to the beach barefoot on a really sunny day… the sand gets really hot, but the rocks are cooler because they conduct heat better. We’ll be able to use this kind of stuff to tell how compact the soil is, and where it’ll be safest to drive the rover.

Even better, we’ve got the first determinations of what minerals are present near that rover. It’s a very interesting story that I think will continue to unfold in the days and weeks ahead. Phil and I will be presenting the results in a press briefing that starts at 9:00 AM Pacific today. It’s very cool stuff.

January 12, 2004

We’re almost there… just one cable-cut away from being a free-wheelin’ machine. Spirit is now fully stood up, with every last hardware deployment done. The solar arrays are out, the mast is up, the antenna is free, the arm is released, and all six wheels are cut free from the lander. The one and only thing tying us to the lander now is a single electrical cable, and we’re going to cut that tomorrow. The egress drive is currently scheduled for Sol 12 if everything goes well, and then we’ll be ready to start our exploration of Gusev crater.

And what a site to explore! We’re releasing the first full panorama from Pancam today, available for download on the JPL web site. The views off into the distance –particularly of the hills to the east — are spectacular. And then just another few days and we’ll have six wheels in the dirt.

One other bit of good news (it just seems to keep coming): We did a second health check on the Moessbauer Spectrometer today, and it looks fine… every bit as good as it did back in Florida. We still don’t know exactly what went wrong with it during cruise, but we’re seeing flawless performance now. Strange and wonderful.

January 15, 2004

We’ve done it. Spirit is on Mars. We’ve got six wheels in the dirt now, and we’re ready to roll.

I wish there were some way that I could find the words to describe how a moment like this feels, but I can’t. I sit here tonight, after an experience like what we’ve just been through, and a thousand images and feelings go through my mind. The exhilaration of NASA telling us six years ago that we could go to Mars, followed by the shock of watching the missions in line in front of us fail and our own mission get cancelled. Our amazement as brilliant JPL engineers found an approach that might get us to Mars anyway. The horrors of ripped parachutes and burst airbags, and the times when it looked like only a miracle could get us down onto the martian surface. The joy and nervous tension of launch. And then, of course, the "six minutes of terror" that got us down onto the martian surface for real.

Trenching experiments where five wheels are locked and the one free wheel digs up to its radius, about six inches, then turns around to image the trench. See Spirit’s images and slideshow

All of that is behind us now, and the years of work by the thousands of people who made this mission possible have finally paid off. Spirit is in her native habitat at last, and we’re ready to begin exploring Gusev crater. For all of us who have had the honor of being part of this, it has been one of the greatest experiences of our lives. And for all of you who made it possible, with your tax dollars and your support, we’re going to do the very best we can to make this mission worth your investment and your trust.

And, check this out: We get to do it again! Opportunity lands at Meridiani Planum just nine days from now.

January 22, 2004

We’ve just hit the first significant bump in the road since Spirit landed. By now you’ve heard the news that we’ve been having communications problems with our rover. It’s cause for concern, certainly, but it’s not cause for alarm. I’ve been in this business for almost 25 years now, and I’ve been involved in over a dozen different planetary missions. I don’t know of a single one that hasn’t had a problem like this somewhere along the line, and I include in that list missions like Voyager and Magellan that were spectacular successes. This kind of thing is part of the business of operating complicated spacecraft far from Earth.

There are two reasons to be optimistic. One is that Spirit is very, very good at keeping itself safe. This vehicle knows how to protect itself when something goes wrong, and can do so for long periods of time. The other reason for optimism is that the MER engineering team is very, very good at figuring out what’s going on when something goes wrong. Given enough time they’re going to get it, and I expect Spirit to give them all the time they need. So I’m very optimistic that we’ll get this straightened out, and get back to the business of exploring Gusev crater.

January 29, 2004

We’re back on track now, after getting a pretty serious scare from Spirit. Spirit’s problems seem to have been caused by little more than a fouled-up computer file system… not too different from what can happen when you hit the power button on your computer accidentally and corrupt a bunch of files on your hard drive. The JPL flight software team is hot on the trail of this thing now, and I’m hoping that Spirit will make a full recovery.

Lander pod for Opportunity in Eagle Crater. See Opportunity’s images and slideshow

And how about that Opportunity landing site?!!! The pictures are just sensational.

I have to confess that we lucked out on this one. We weren’t lucky that we landed safely… that was the result of years of work by an incredibly talented and dedicated team of engineers at JPL. But we were very lucky to come down where we did. Some of the most interesting geologic materials at Meridiani Planum seem to be exposed only in impact craters, which are pretty rare in that neighborhood. So where do we land? Right in a crater. Tiger Woods couldn’t have pulled this one off. Most of the Opportunity standup and egress process is still ahead of us, and it isn’t going to be easy. But if all goes well, we should be off the lander and headed for that outcrop before too very long.

January 31, 2004

What a wonderful day. We now have twelve wheels safely on martian soil. I’ve said since the very beginning of this thing that there were six terrifying events over the course of this mission… two launches, two landings, and two egresses. All six of those are behind us now. We have two healthy rovers, each with completely healthy payloads, on the surface of Mars and ready to explore.

We also have a whole bunch of hematite at Meridiani! The first Mini-TES results are in, and we’ve got a slam-dunk identification of hematite in the gray soil granules around the lander. This spectrum shows a laboratory spectrum of hematite (the red curve) and a Mini-TES spectrum of the dark soil near the lander (the yellow curve). The close match of the up-and-down lines at the right end of the plot is what tells us we’ve definitely found the hematite.

There’s lots more news to tell, but a bunch of people are about to head out to celebrate (at 7:00 AM Pacific time!)and I’m going to join them…

February 2, 2004

So now it really begins in earnest. Opportunity has been cranking away for several sols now, and as of yesterday Spirit is back up and running too. So now, for the first time, we have two rovers with twelve wheels in the dirt, both doing science.

It’s not easy to deal with. The two landing sites are on totally opposite sides of the planet, which means that when it’s the middle of the night for one rover, it’s noon for the other. The bottom line is that there’s something going on pretty much all the time. But as tempting as it is to try to work on both rovers at once, you just can’t do it. Unfortunately, you just have to sleep sometime! Personally, I’ve been working on Opportunity, where the big story is that fantastic rock outcrop less than ten meters away from us. We’re going to spend some sols working on the soil before we head over to it, but it shouldn’t be long.

And on Spirit (from what I hear… I’ve been sleeping, really) the news is that they’re back to work on the rock we’ve named Adirondack. Now that we know what the outside of Adirondack looks like, the next step is going to be to take the RAT to it and see what it’s like on the inside.

February 11, 2004

The closer we look at this outcrop at Meridiani, the more interesting it gets. We knew when we saw it from a distance that it had really thin layers. When we checked it out with the Microscopic Imager, though,(see a cool image here) we saw some very strange things. One is that the layers are really thin… like just a few millimeters thick in some cases. Another is that we see these strange round objects we’re calling "spherules" embedded in the outcrop, like blueberries in a muffin. The outcrop erodes away as it gets sandblasted, and the spherules (which seem to resist erosion better than the rest of the outcrop does) fall out and roll down the hill. Weird.

Columbia Hills loom with increasing detail at the Spirit rovers’ Gusev Crater site. See Spirit’s images and slideshow

We’re in the middle of doing two things now. One is driving along the face of the outcrop and shooting lots and lots of high-resolution images of it. We’ll use those to pick a couple of places that we’ll drive to later and really look at up close. The other is puzzling through some data that we took on a spot called Stone Mountain at the far right end of the outcrop. We’ve got APXS, Moessbauer, and Mini-TES data on Stone Mountain now. The one result so far that you can really hang your hat on is that the outcrop is chock full of sulfur… much higher in sulfur than anything ever seen on Mars before. And the Moessbauer and Mini-TES data are, well, interesting. We’re still pondering on them, but we should have something soon. This is quite an amazing piece of rock.

And by the way, don’t infer from the fact that I’m rambling on about Opportunity that I’ve forgotten about Spirit. The problem with this mission is that there simply is no way you can work both rovers at once… you’d never sleep. You’ve got to work on one or the other, and right now I’m working on Opportunity. The story on Spirit these days is pretty simple… pedal to the metal, and head for the crater we’ve nicknamed Bonneville. And then we’ll see what we see.

March 4, 2004

Sorry it’s been so long since I’ve done one of these updates! The story of the Meridiani outcrop has grown very interesting, and it has taken up much of my time and attention.

By now you’ve probably heard that we think the rock that makes up this outcrop was once pretty well soaked in liquid water. There are four lines of evidence that support this idea. One is that we now think it’s pretty likely that the little round things in the outcrop (the "blueberries") are what geologists call "concretions". They seem to be different in composition from the stuff in which they’re embedded, they don’t deform the layers around them, they’re not concentrated along layers, and we sometimes see layers running through them… all of which are consistent with the idea that they’re concretions. And if that’s what they are, then they point to water, since concretions form when minerals are precipitated from groundwater.

Mars Global Surveyor image of landing site, showing Endurance Crater. Click image for larger view.
Credit: Malin Space Systems/NASA/JPL

The second piece of evidence is some weird little holes that are shot through many parts of the outcrop. The holes are tabular in shape, and they look just like what happens when crystals of certain minerals (gypsum could be one example) form from liquid water in a rock. The crystals grow in tabular shapes, and then later they either dissolve or erode away, leaving funny chicken-scratch looking holes behind. You might be able to come up with some other explanation for these things, but they’re awfully darn similar to features found in rocks on Earth where this has happened. It seems to be the most likely explanation.

The third piece of evidence is that there is a huge amount of sulfur in this rock. There’s so much sulfur that we think there has to be a lot of some kind of sulfate salt in the rock, which is very hard to account for unless water was involved.

And finally, we see a mineral called jarosite in this rock, which is an iron sulfate hydrate. There’s a lot of jarosite there, and jarosite is a mineral that requires water for its formation.

So water once flowed through these rocks. It changed their texture and their chemistry, and it left behind the clues that we’ve been able to read. It’s a nice conclusion, and we feel pretty confident about it.

The really cool thing here, of course, is that a groundwater environment like this would have been suitable for some simple forms of microbial life. That doesn’t mean life was there, of course! But we flew this mission because we wanted to find out if Mars ever had habitable environments. And the answer, we now believe, is that it did.

After we announced all this to the world yesterday, I had a reporter ask me if this finding meant "mission accomplished". My answer was, effectively, "yes and no". On the one hand, we set out to learn something about Mars, and we’ve done it. If both rovers died tomorrow, heaven forbid, I think this mission now would always be thought of as a success.

On the other hand, we’ve still got two very healthy rovers on the surface of Mars, and a lot more work to do. At Gusev, the best stuff may lie ahead, either in Bonneville crater or off towards the Columbia Hills. And at Meridiani, who knows what wonders lie outside this little crater that we landed in. In some sense, I’m not going to feel like we’ve really accomplished our mission until we’ve learned everything about Mars that we can possibly learn with these two wonderful machines of ours… and that is still a long way off.

March 24, 2004

We just announced another big finding at Meridiani: We think that the rocks there were deposited in liquid water.

This finding is fundamentally different from what we announced three weeks ago. It’s the difference between water you could draw from a well and water you could swim in. Last time, we had evidence that water had once seeped through the rock, changing its chemistry and its texture. This time, we think we see telltale signs suggesting that the rock was originally laid down in gently flowing liquid water.

The spherules, blueberries and naming have become important to visualize an alien landscape.
Credit: NASA/JPL

This one didn’t come easy. Several weeks ago, as we looked at the outcrop, we thought we were seeing what geologists call "cross bedding". Cross bedding means seeing layers in the rock that aren’t parallel to one another, and cross bedding in a rock generally means that it was deposited in a flowing fluid. Either air (wind) or water (currents) can be the fluid. On earth, it turns out that there are some kinds of cross bedding that only form in liquid water… wind won’t do it. We thought that that was what we were seeing in some of the Pancam images of the Meridiani outcrop. Maybe.

With even Pancam images not being sharp enough to resolve the problem, we turned to the only higher-resolution camera we have: the Microscopic Imager. Back when we built the MI, we really only envisioned using it to image areas a few centimeters across. In fact, the field of view of the camera is only 3 cm wide. But here we had a problem where we needed ultra high-resolution images of rocks that were much, much bigger than an MI field of view. So we did something that we had really never envisioned doing… we took some big image mosaics with the MI. There was one rock called "Last Chance" that we took 152 images of!

This was a remarkable feat of robotic imaging, and Ken Herkenhoff, Eric Baumgartner, and a whole bunch of other people too numerous to name deserve enormous credit for pulling it off. (And hats off too to the good folks at ASI, who built us one heck of an arm.) Anyway, the whole thing paid off. The MI mosaics nailed the problem, showing us features in the rock that look like the distinctive signature of ripples formed in flowing water.

What are we going to do for our next trick? I have no idea. This whole thing has turned out to be such a surprise that I wouldn’t dare guess what we’re going to see next. The plan for Opportunity now is to crawl out of Eagle crater (which we’ve just done), and head 700 meters across the countryside to Endurance crater, which is much bigger and wilder-looking than Eagle. And then we’ll see what we see.

Meanwhile, Spirit is way out ahead of Opportunity, distance-wise, working her way now along the rim of Bonneville crater. We haven’t found any compelling evidence of water at Bonneville yet, but there’s been some fantastic geology there… and the Columbia Hills beckon.

April 16, 2004

Bounce rock with dust fines around the milled-out hole drilled by the rock abrasion tool revealing lighter interior surfaces. Credit: NASA/JPL/Cornell

Well, the Battle of Bounce Rock is over.

A little while after we landed at Meridiani with Opportunity and took our first look around, we noticed that there was only one object anywhere outside Eagle crater that looked even remotely like a decent-sized rock. We named it "Bounce Rock" because we could see that the airbags had bounced right on top of it as the landing took place. (It figures that if there was only one rock for what seems like miles in every direction, we’d find a way to hit it!) So once we climbed out of Eagle Crater and before we headed for Endurance Crater, it made sense to go over and check Bounce Rock out.

(It’s worth noting, by the way, that not everybody on the team was even convinced that it was a rock at first. There was some speculation that it might actually have been one of the airbag covers, shaken off during the landing by a particularly sharp jolt. Before we got to it we had a little guessing game going, with the votes about evenly split between "Mars rock" and "flight hardware", along with a few brave souls who thought it might be a meteorite.)

It was fun, and it sure was interesting, but it was a bit of a struggle. What had us going for awhile there was a very nice Mini-TES spectrum that seemed to show a lot of hematite in the rock. We knew there was hematite in the soil at Meridiani, but this was the first time we’d gotten a hematite signal from rock… so it looked very interesting. We rolled up to it, whipped out the Moessbauer Spectrometer, took some good data, and to our surprise we found no hematite in the rock at all. In fact, the only mineral that the Moessbauer detected was pyroxene, which made this rock look very different from anything we’d ever seen, at either landing site. We put a hole in it with the RAT, looked again, and saw the same thing — lots of pyroxene and no hematite.

So what was going on? Turns out we’d been faked out on the Mini-TES data. We had been pretty far away from the rock when we had first looked it, and the Mini-TES field of view had also included a particularly hematite-rich patch of soil immediately behind the rock. Once we got close enough to see the rock better with Mini-TES, the Mini-TES data confirmed the absence of hematite, confirmed the pyroxene, and also showed some plagioclase, another mineral, in the rock. So the story was coming together.

Then came the most interesting part of all, the APXS data. The APXS measures elemental chemistry, and what we found was that, chemically, Bounce Rock is almost a dead ringer for a rock called EETA 79001-B. Odd name for a rock; 79001 actually is a rock from Mars that was found in Antarctica back in 1979. It was knocked off of Mars long ago, orbited the sun for awhile, and eventually hit the Earth in Antarctica, where it was found many years later by an expedition sent there to collect meteorites. There are more than a dozen such rocks that are believed to be from Mars on Earth. But until Bounce Rock, nobody had ever found a rock that was actually on Mars and that matched the chemistry of one of these rocks. Now we have.

We’re not quite sure where on Mars Bounce Rock came from, but we suspect that it might have been thrown out of a big impact crater that’s about 50 kilometers southwest of our landing site. So it’s not a meteorite, but it probably did fall from the sky. And it turned out to be a very interesting stop on our drive across Meridiani Planum.

Related Web Pages

Mars Rovers JPL
Spirit’s images and slideshow
Opportunity image gallery and slideshow
Mars Berries Once Rich in Iron-Water
NASA’s RATs Go Roving on Mars

Water Signs
Microscopic Imager
Gusev Crater
Pancam– Surveying the Martian Scene
Mössbauer spectrometer
Alpha Proton X-ray Spectrometer