NASA's newest rover is heading for the hills

Scientists to send `Spirit' to nearby crater's edge

January 14, 2004|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

When NASA's Mars rover Spirit rolls off its lander sometime tonight, mission scientists plan to take a quick look around a nearby crater, and then head for the Eastern Hills two miles away.

They know they may never get there.

"The hills are five times farther than Spirit was ever intended to go," said Steve Squyres, the rover's principal investigator. But they also promise a geological bonanza, and the scientists can't resist the attempt.

"The view will get better and better," Squyres said. "Hopefully, we'll learn more and more about what lays on these plains, and what lies above and below them. It's a shared adventure that I think is unprecedented in human history. And I think it's going to be a lot of fun."

Spirit bounced down into Mars' Gusev Crater on Jan. 3. After delays caused by airbags that partially blocked the rover's primary off-ramp, the vehicle has uncoupled from its lander.

By yesterday, engineers had begun a series of maneuvers that will turn the vehicle 115 degrees and point it down a different off-ramp. Roll-off was expected sometime tonight or early tomorrow.

Controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., planned to drive the rover straight off the ramp, then stop about three feet away for a look at soil and rocks with Spirit's instruments and microscopic imager.

They also planned to take three-dimensional photos of the rover's wheels to examine the Martian soil's compressibility, and determine how the dirt sticks to them.

The next destination will be Sleepy Hollow, a depression a few dozen yards from the lander, then a meteorite crater about 825 feet northeast of the landing site. There are no plans to roll Spirit into the crater, which is estimated to be 10 to 20 yards deep, with a 15-foot rim.

"I expect it will get rougher when we get there," Squyres said, "and we'll be darn careful. We've never driven up to a Martian crater before. Whether it's important to get right to the rim or not - good question."

It may not be necessary. "What we're interested in is the material ejected by the [meteor's] impact," said Tim Parker, the landing-site mapping scientist. That material could provide samples of Martian bedrock that would otherwise be too deep for Spirit to reach.

From the crater, scientists planned to turn east toward the hills, 1.8 to 2.5 miles away. It will be a long trip.

Spirit creeps along at just over one inch per second, and designers of the $820 million mission only intended it to travel 650 yards during its planned 90-day lifespan on Mars.

"Most of us are feeling pretty good about that number right now," Squyres said. But rolling on for several miles will require that the rover's solar-electric power and heating systems keep working in dust and deepening cold as the Martian summer slips into autumn.

"We're wearing a winter coat now in the middle of summer," said JPL flight director Chris Lewicki. But he said he expects the rover's heaters will keep its motors running beyond the 90-day mission target.

The Eastern Hills stretch for several kilometers from north to south. The biggest are no more than 100 yards tall.

"How they got there and what they are. ... Boy, that's a tough question," Parker said. Some team scientists think they can see exposed layering in the hills, suggesting their rocks were lain down by wind or water, then thrust upward.

But it's "premature to draw conclusions like that," Parker said. "The thing to do at this point is to let Mars tell us what they are."

Squyres called it "a beautiful piece of scenery, one we will get to really know in the weeks ahead."

Meanwhile, NASA scientists provided the first details yesterday on Spirit's Jan. 3 bounce-down. A review of the data showed that the spacecraft's parachute opened 4.6 miles above the surface - a mile lower than planned, "which, as you can imagine, makes things more exciting toward the ground," Parker said.

Spirit was falling at 920 mph when the chute opened, and slowed to 152 mph - a bit slower than expected, but still 30 mph faster than a skydiver in freefall.

At 343 feet above the surface, Spirit fired its descent rockets. At 28 feet from the surface, it cut itself free of its parachute and bounced 28 times on its air-bag cushion before stopping.

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