Mars Rover Marks Second Anniversary of Landing

NASA's two Mars rovers, Spirit and Opportunity, were designed to last 90 days. But Tuesday night marks the two-year anniversary of Spirit's landing, and both rovers are going strong. The robotic geologists have provided invaluable data about whether Mars could once harbor life.

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MICHELE NORRIS, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

ROBERT SIEGEL, host:

And I'm Robert Siegel.

As we speak, two remarkable robots are hard at work more than 30 million miles away on the surface of Mars. The six-wheeled explorers known as Spirit and Opportunity were supposed to last 90 days. Well, tonight is the two-year anniversary of Spirit's landing, and both rovers are going strong. They've provided scientists with data to back up their theories about whether Mars was once a wetter, warmer planet, one that could have harbored life. NPR's Joe Palca reports.

JOE PALCA reporting:

Getting a spacecraft to Mars is an amazing technological feat. Getting it there and landing it safely is even harder. But a team from NASA's Jet Propulsion Laboratory in Pasadena didn't just do that once in January 2004; they did it twice, first with a rover called Spirit that landed in the giant Gusev Crater and then three weeks later with Opportunity on the other side of Mars in a vast plain called Meridiani.

Think about it. In about six and a half minutes the spacecraft had to go from more than 10,000 miles an hour to a dead stop. This was accomplished by a heat shield, a parachute and some retro-rockets and, finally, air bags that inflated just before touchdown. The air bags cushioned the precious rovers that didn't so much land as bounce down to the surface.

On the night of January 3rd, 2004, the control room in building 264 at JPL was packed. As the spacecraft descended, it sent back signals when critical events occurred: heat shield separation, parachute deployment, retro-rocket firing. Finally, the signal everyone was waiting for.

Unidentified Man #1: We have signs of bouncing on the surface.

(Soundbite of cheering)

PALCA: But then the spacecraft went silent.

Unidentified Man #1: Hang on, everybody. Please be quiet. We don't see a signal at the moment. No signal at the moment.

Unidentified Man #2: We saw an intermittent signal that indicated we were bouncing. However, we currently do not have signal from the spacecraft.

Unidentified Man #1: Please stand by.

PALCA: For 16 excruciating minutes engineers stared at their consoles and waited.

(Soundbite of Jet Propulsion Laboratory activity)

Unidentified Man #3: All I see is...

Unidentified Man #4: Do you see it? Do you see it? Do you see it?

Unidentified Man #5: What do we see?

Unidentified Man #1: There it is.

(Soundbite of cheering)

PALCA: NASA's deep space network picked up the rover's signal, and all was well. The next few days went better than anyone on the rover team dared to imagine. Less than a day after touchdown, chief scientist Steve Squyres reported good news.

Dr. STEVE SQUYRES (Chief Scientist): We've gotten the first images from the descent camera back. They're beautiful. They show distinctive patterns of impact craters. We landed in the sweet spot.

PALCA: For Squyres, the success was particularly satisfying. He teaches at Cornell University, and like a lot of planetary astronomers, he dreamed of sending scientific instruments to Mars. It took years to persuade NASA officials and his fellow scientists that his instrument package was the one most worth sending.

One of the most important instruments was the Pancam, a high-resolution camera that would give the best views ever of the martian surface. In his book "Roving Mars," Squyres recalls the first time he saw Pancam pictures on Mars. He was planning to get some sleep after staying up all night after the landing when his assistant told him that the pictures had arrived.

Dr. SQUYRES: (Reading) `I run back to building 264 and up the three flights of stairs, not waiting for the elevator. Trying to catch my breath, I walk down the hallway to the Pancam room expecting it to be mobbed. Instead the room is dark. I step inside, and there is Jim Bell, the lead scientist for Pancam, all alone slumped in a chair and staring at a monitor. There are tears in his eyes. On the screen is Mars with colors so perfect and detailed so sharp it's like being there yourself. He looks up at me. "It works, man. It works."

This is so good. I can't believe how good this feels, but I'm not going to get all misty-eyed. I'm cool. I go back outside, do a couple more interviews and then head home and microwave up some frozen spaghetti. I'm sitting on the couch in a darkened apartment in my underwears eating my spaghetti when suddenly the events and the emotions of the day come tumbling down on me. Pancam is really on Mars after all these years. The whole damn thing is on Mars. I dissolve into tears.' I remember that real well.

PALCA: Now NASA sent the rovers to Mars to search for signs that liquid water once flowed there because where there's water, there could be life. Scientists carefully chose both landing sites because they looked like places water had once flowed. But at first Spirit's landing site at Gusev Crater was a bit of a dud. It looked like a dry lake bed from space but none of the nearby rocks showed any sign of a watery past.

On the other side of the planet, Opportunity was having more success. That rover plunked down near some outcrops that showed patterns like what you'd see in rocks sitting in slowly moving water. But looks can be deceiving. Rover scientists waited for data from rover instruments that measure the chemical composition of rocks. By April of 2004, Squyres and his colleagues had amassed enough data from Opportunity to make a bold claim.

Dr. SQUYRES: We found an enormous quantity of sulfur in this rock, too much to explain by any other mechanism, we believe, than this rock being full of sulfate salts. That's a telltale sign, we believe, of liquid water.

PALCA: The water is long gone. It's evaporated, leaving the salts behind. But where Squyres sees a watery past, others see a drier one. Tom McCollom is a geochemist at the University of Colorado in Boulder. He doesn't dispute the fact that Opportunity found sulfate salts. He just disagrees with Squyres about how they got there.

Mr. TOM McCOLLOM (Geochemist, University of Colorado): The sulfate salts that are in there come from reaction of the rock with sulfuric acid rather than from evaporation of a fluid.

PALCA: McCollom's work appears in the latest issue of the journal Nature. Squyres says more recent rover data confirms a watery history at Opportunity's landing site. But the question of when and whether this part of Mars was once wet is likely to be kicked around at scientific meetings for years. Tom McCollom says scientists have the rovers to thank for that.

Mr. McCOLLOM: We now have this tremendous data set that's being returned by the Mars rover that--I mean, we wouldn't have any debates if that data wasn't there. There wouldn't be anything to debate about.

PALCA: Both rovers are showing some signs of age. Opportunity has a sore shoulder in its robotic arm, and one of its wheels is stuck at a slight angle so the rover handles more like a wobbly shopping cart. Over in Gusev Crater, Spirit had been running low on energy as the martian dust began to cover the rover's solar panels. But then, miraculously, there was what engineers call a cleaning event. They don't know for sure, but apparently a mini tornado passed over the rover blowing all the dust away.

And Gusev is no longer the scientific dud it appeared to be. As Spirit began ascending some hills about two miles from its landing site, it found signs that water was once on this part of Mars, too. John Graham is a rover scientist at the Smithsonian's Air and Space Museum. He says Spirit has just come down one hill and is heading for another.

Mr. JOHN GRAHAM (Smithsonian Air and Space Museum): And we're on a very tight time line, and the reason for that is we need to get to the base of the next hill to the south, which has got north-facing slopes, so that we can get up and basically repeat what we did last winter on Husband Hill: turn the solar panels towards the sun and survive. So we are definitely in a strategic mode here where we're planning on making it though the winter and going on.

PALCA: Perhaps for another year, perhaps longer--not bad for a mission that was supposed to last 90 days. Joe Palca, NPR News.

NORRIS: This is NPR, National Public Radio.

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