The Spirit rover finally rolled onto the surface of Mars today and dutifully beamed back photos showing its now-abandoned lander resting atop crumpled airbags on the frigid martian soil. It was yet another moment for hugs and cheers in a mission that has proceeded from one emotional high to another since landing on Jan. 3.

Spirit's view looking back at the lander. Credit: NASA/JPL See larger image here

"Less than 24 hours ago, President Bush committed our nation to a sustained human and robotic program of exploration," said Charles Elachi, director of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "But we at NASA, we move awfully fast, in less than 15 hours, by doing our first step. Spirit is now ready to start its mission of exploration and discovery. We have six wheels in the dirt. Mars now is our sandbox and we are ready to play and learn. I have to tell you, I've never seen so many people so excited by just seeing two tracks in the dirt."

He was referring to the tread marks left in the martian soil behind Spirit's rear wheels.

"Last night ... I looked up in the sky and looked at Mars," Elachi said. "And I'm still awed that we have a rover on that planet. And I was thinking to myself that for centuries, there were millions of people who looked up the same way I looked up and were wondering what's up there.

"But we know what is up there. Just think about that. ... Think of the endless possibilities that this generation is going to leave as a legacy for generations of the future."

For mission manager Jennifer Trosper, who explained the roll off operation to Vice President Dick Cheney the day before, the moment called for a toast. At a 6 a.m. news conference attended by dozens of Spirit engineers and scientists, she pulled out a bottle of champagne and toasted "all the people who contributed to getting us to six wheels on Mars. Your efforts are historical. Thank you very much."

"You know how you write your to-do list for the day?" she asked. "My to-day list for (Wednesday and Thursday) was get some images from Mars, meet with the Vice President, then drive the rover onto Mars. I think as a young girl growing up on a farm in Ohio, I probably never envisioned that that might be my to-do list for today! But I am very honored and privileged to be part of this team that was able to do that."

The command ordering Spirit to roll off its lander was transmitted at 3:21:30 a.m. EST. Confirmation the rover had successfully negotiated its egress route and short drop to the surface came right at 5 a.m. as telemetry and then photographs showed Spirit's wheels in the dirt and the lander in the background (see earlier story for complete details).

"Is there life on Mars? The answer is absolutely yes. And we put it there today," said Joel Krajewski, chief engineer for impact and egress. "Thank you to this whole team for helping us do that."

The Spirit rover's view forward as it drives on the surface of Mars today. Credit: NASA/JPL See larger image here

For Kevin Burke, the engineer responsible for the rover's final egress onto the surface, the first grainy, black-and-white image confirming the successful maneuver was worth much more than a thousand words.

"I've gotta tell you, being the last person who has the last piece of hardware between sticking on the lander and being on the surface of Mars is very, very stressful," he said, prompting laughter from his colleagues. "I'm really glad, I'm really glad that we're done."

Flight director Chris Lewicki said the successful roll off opened a new chapter in Spirit's mission.

"So now it's the time where we kind of hand over the keys," he said. "We get to drive the nice sports car but in the end, we're just valets bringing it around the front and handing the keys over to the science team."

Spirit will remain where it is, close beside the no-longer-needed lander, for three to four days. Starting late tonight, engineers will begin putting the rover's robot arm through its paces, checking out its rock-eroding abrasion tool and taking the first microscope images of the rocky soil directly in front of the rover.

Late Friday, the arm's two spectrometers will make measurements and then, if all goes well, Spirit will begin moving again late Saturday or Sunday night.

Earlier today, principal Investigator Steve Squyres briefed the flight control team on the latest exploration strategy.

"We will do, I'm sure, magnificent things with this vehicle as time goes on, but we want the first drives, the first deployment of the IDD (instrument deployment device, or robot arm), the first-time activities to be clean, straight forward, as free of risk as they can be when you're operating a robot on Mars," he said.

"Ultimately, one of the things we want to do at this site is characterize the geological diversity. That means going and finding the unusual rocks, finding the unusual soils, finding the things that are not characteristic of the typical stuff around it. But before we can do that, we've got to understand the typical stuff.

An artist's concept of Spirit exploring the landscape. Credit: NASA/JPL

"So the most important thing to do at the outset is to find characteristic, typical, kind of a baseline material and get a really good characterization of those things with the entire suite of instruments on the vehicle," he said. "I've likened this rover recently to a Swiss army knife, with all the different tools that it has on it. And you want to bring all those tools to bear on the key geologic materials."

Spirit also will participate in a first-of-a-kind joint project with the European Space Agency's recently arrived Mars Express orbiter.

"There's a remarkable event that's going to take place tomorrow where the Mars Express orbiter is going to go over our site and for the first time, we're going to be doing coordinated, international surface and orbit observations on the surface of another planet," Squyres said. "That's going to be really cool.

"Mars Express is going to be looking down with a very sophisticated suite of sensors at the very same time that we can look up and we can look at the terrain around us. So we'll be looking at the same patch of soil, looking through the same column of atmosphere at the same time Mars Express is going overhead. That's an opportunity not to be missed."

Looking ahead, Squyres reminded the flight control team that another rover, Opportunity, is scheduled to land on the other side of the planet at 12:05 a.m. EST on Jan. 25. To minimize the workload, Spirit will be parked over a scientifically interesting patch of soil for lengthy spectrometer measurements while the engineering community focuses on getting Opportunity safely down.

"Around the time that Opportunity lands, I don't need to tell this group that things are going to get pretty hot and heavy in here," Squyres said. "So to make it easier on everybody, for sols-22, 23 and 24, at this site, we're going to have a three-day stand down. By stand down, I don't mean we're not going to do any science activities. In fact, we're going to do a lot of science activity, But we wanted to plan three sols (martian days) that we could really plan in advance, script them ahead of time, get the whole thing ready to go ... and ease the burden on the team for that activity. That requires some significant advance thought and planning."

An artist's concept of the rover's scientific arm in action. Credit: NASA/JPL

In an ideal world, he said, "we'd like to get a good, clean characterization of what the rocks look like without any dirt and a good, clean characterization of what the dirt looks like without any rocks. We can't do that here. We're going to end up in a little pebble field (with) all sorts of stuff mixed together. When we first put down an instrument like the APXS (Alpha Particle X-ray Spectrometer) on this patch, we're going to have rock and soil mixed together. It's going to be a deconvolution problem that we're not going to know how to solve until we've looked at the pure end members.

"But from the standpoint of checking out the IDD, checking out the instrument positioning system, it's a perfect place to do it. It's smooth, it's flat, there are plenty of features there for doing stereo ranging, you couldn't do any better."

And so for now, Spirit will remain right where it is. But by Saturday night or Sunday, it should be ready to roll.

"At that point, we start thinking about which rock to go to first," Squyres said. "Now we're starting to talk about the pure end members. We want to do rock first, followed by soil."

Three rocks directly in front of the rover have been identified as possible targets. Two of them, nicknamed Sushi and Sashimi, are located in a cluster or rocks known as the Wasabi region near Sleepy Hollow. The other rock, located to the left as viewed from Spirit, is known as Pyramid because of its sharply sculpted edges. Squyres said Pyramid is the leading candidate at present.

Once the initial rock observations are complete, Spirit will be positioned over undisturbed, fine-grain soil for the Opportunity stand down. A patch of pristine sand-like particles is present near Pyramid, as well as inside Sleepy Hollow.

These rocks and depression, given names by the scientists, will be studied by Spirit. Credit: NASA/JPL/Cornell See larger image here

Once that work is done, Spirit will drive up the lip of a nearby 660-foot-wide crater in hopes of finding rocks that were blasted out from below the surface. Such rocks may hold clues about whether or not the larger Gusev Crater landing site once held a vast lake.

"By going to lip of the crater, we will be able to sample material that has been thrown out," Squyres said. "There's a lot of talk on the science team about do we go down into the crater, do we not go down into the crater? Don't know, it depends on what we see when we get there, how daunting the terrain looks. We may find when we get in there it's mostly full of drift material. ... But by looking at the ejecta field, we expect to get a good handle on what materials have been excavated. Then, of course, we head for the hills."

He was referring to a cluster of hills two miles away that may be beyond Spirit's range. But scientists are eager to head that way because of the possibility the rover might find rocks that originated at higher levels.

"This is more than just 'get the scenery better,'" Squyres said. "There are several reasons to do this. One is, of course, the closer we get to it, the higher the resolution will be with our remote sensing instruments. Another is that there are a variety of materials ... that could shed off the hills and onto the flats around us. ... which may be a totally different material. And then of course, the image all of us want, is the view from part way up those hills looking back down onto the plains and where we came from."

Video coverage for subscribers only:
   VIDEO: FLIGHT DIRECTOR CHRIS LEWICKI GIVES OK FOR DRIVE QT
   VIDEO: MOMENT WHEN DRIVE ONTO SURFACE IS CONFIRMED QT
   VIDEO: CELEBRATIONS AT FIRST VIEW OF EMPTY LANDER BASE QT
   VIDEO: IMAGES RECEIVED FROM SPIRIT AFTER THE ROLL-OFF QT
   VIDEO: ANIMATION OF SPIRIT'S TURNS & DRIVE FROM LANDER QT
   VIDEO: TODAY'S NEWS CONFERENCE AFTER SPIRIT'S DRIVE QT
   VIDEO: MISSION CONTROL TEAM BRIEFED ON SCIENCE PLAN QT
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