Exploring Mars

Exploring Mars

Driver required to operate robotic rover from 190 million kilometres away. Must be able to negotiate vehicle across rock-strewn martian terrain using commands that take 11 minutes to arrive. Experience with computer games an asset.

The help-wanted ad could have read like that, but there was no need to run one. Brian Cooper fit the bill, and the 37-year-old electronics whiz was already in the right place at NASA's Jet Propulsion Laboratory in Pasadena, Calif. (Favorite computer game: Quake, a popular shoot-'em-up action thriller set in three times: past, present and future.) As the techie who created the workstation to control the six-wheeled Sojourner vehicle that landed on Mars on July 4, Cooper got to sit in the driver's seat for its wanderings last week. First stop: the soil beside the lander. Next, on to Barnacle Bill, a crusty looking grey rock about 25 cm long, just three metres from the landing site. Then another drive to Yogi, a larger, vaguely bear-shaped rock three metres farther away. Still on the itinerary: two intriguingly white rocks nicknamed Scooby Doo and Casper, and as much other surface material as Sojourner can reach in its brief working life. And at each stop, Sojourner beamed back information that thrilled the mission scientists and added new dimensions to earthlings' understanding of a close neighbor.

Amid the ecstatic Pasadena team revelling in the performance of Pathfinder and its cargo, the solar-powered Sojourner, sat Cooper, living a schoolkid's fantasy. Eyes shrouded by 3-D glasses, he studied the spacecraft's images of its surroundings on a high-definition TV, then fired off instructions to guide the microwave oven-sized rover on the next leg of its journey. "I'm just overwhelmed by how well things are going," said Cooper, taking a brief break as Sojourner rested beside Yogi late last week. "I'm so thrilled that our preparation has finally come to fruition."

And what fruition. Scientists and the general public alike marvelled at the wealth of new information pouring in from the NASA's Pathfinder mission. Evidence of vast quantities of iron that, having rusted, give Mars its characteristic red hue. Clues suggesting that there was water on Mars earlier than previously thought - possibly more than four billion years ago, around the time life began on Earth. New signs of the torrents of water or mud, many kilometres wide and hundreds of metres deep, that once raged across the surface with enough force to move boulders. Close-up views of a crust much like Earth's that was almost certainly formed by volcanic action and tumultuous fluctuations between extreme heat and cold. "I surely didn't expect this," glowed University of Tennessee geologist Harry McSween after reviewing evidence that Barnacle Bill is made of material similar to andesite, a common volcanic rock on Earth.

Sojourner's soil-sample information confirmed data that two U.S. Viking spacecraft collected from widely separated sites in 1976. "It means we have three different places on Mars and they are virtually identical," McSween told a media briefing in Pasadena. What they have all found is a topsoil made primarily of iron, with smaller amounts of aluminum, magnesium, calcium, sulphur and potassium. The consistent findings on iron suggest, according to Cornell University planet composition expert James Bell, that "the surface of Mars is rusting."

But on Barnacle Bill, Sojourner's analytical equipment found something else: strong evidence of the volcanic activity long understood to have taken place on Mars. The rover's X-ray spectrometer - a device that identifies the elements making up an object by bombarding it with subatomic particles - found large amounts of silicate. That form of silicon is most likely to be found in quantity in quartz, a rock associated with volcanic activity on Earth. To scientists, that suggests a composition on Mars much closer to Earth's than the moon's is. "The Earth," observed McSween, "is a very unusual place - at least we thought that until last night." If Barnacle Bill is volcanic rock, he added, it was probably transported from nearby ancient highlands by tremendous floods.

In fact, it is the historic presence of water, as suggested in pictures taken by the Viking orbiters 21 years ago, that lured the current mission's scientists to the present site. Scientists analyzing Pathfinder's thousands of digital pictures of the area, known as Ares Vallis (Mars Valley), said they could see patterns in the positioning of rocks on the bone-dry surface that suggested water movement of catastrophic proportions. "This was huge," said geologist Michael Malin, "but we don't know where the water went." Some water, certainly, is frozen in the planet's north polar ice cap. More likely exists in permafrost beneath the surface, and possibly in liquid form deeper down. But there, on the surface of Ares Vallis, are rocks that could contain evidence of a warmer, moister time more hospitable to life.

Nothing like that emerged in Sojourner's first week of wandering. But given the time delay built into Earth-to-Mars driving instructions, Cooper had his hands full just keeping the rover on the straight and narrow. One miscue might have cost him his licence if he had been doing his driving test back home: as Sojourner nestled up to Yogi to do some analysis, its left rear wheel started to climb the rock. No problem. An onboard tilt sensor quickly overruled the command from Earth and set the $34-million vehicle back on level ground. But then a transmission miscalculation meant that Sojourner missed a set of instructions designed to fix its approach to Yogi. That left the rover with nothing to do throughout the martian day that corresponded to the North American night of July 10-11. "It's unfortunate, but it's not dangerous," said deputy project manager Brian Muirhead of the error. "We're going to do again tonight what we should have done last night."

How critical the lost time would turn out to be depended on how long the rover could function in a frigid environment (where nighttime temperatures can dip to -93° C). It was designed to work for a minimum of a week, but mission specialists hoped it would last longer. In any case, the stationary Pathfinder should be operating for at least a month, its mast-mounted camera sending a stream of digital snapshots to help reconstruct the geological history of Mars. "The science," crowed Peter Smith, who heads the team using the camera, "is just beginning."

Meanwhile, back at the space station . . .

While the feats of the Mars Pathfinder mission dazzled earthlings, the aging, accident-prone Russian space station Mir seemed to be experiencing one problem after another. Now in its 11th year of Earth orbit, the 100-ton station lost half of its solar-generated electrical power on June 25, when an unmanned cargo ship crashed into one of its modules, called Spektr. Then, as the three-member crew - Russians Vasily Tsibilyev and Alexander Lazutkin and British-born American astronaut Michael Foale - got ready to make repairs, they encountered more trouble. Navigational equipment temporarily failed, forcing the crew to use Mir's rocket engines - instead of electronic guidance - to keep its solar panels facing the sun.

Tsibilyev and Lazutkin will face a daunting task when they enter Spektr to begin repairs tentatively scheduled for this week. Wearing bulky space suits and using equipment delivered by a supply mission last week, they will try to reconnect 17 internal cables, severed in the collision, to Spektr's solar panels. While the accident was the worst in Mir's history, it was just the latest in a series of mishaps, raising doubts about the continued usefulness of the veteran spacecraft. In February, an oxygen canister caught fire; in April a coolant leak caused temperatures aboard Mir to rise to 31° C.

One of Mir's current functions is to enable Russian cosmonauts and space officials to work with counterparts from the United States and the 12 other countries participating in the planned $37-billion international space station that is scheduled to take a crew aboard in 1999. Canada is constructing a $1.1-billion mobile servicing system for the station. And next summer, the first Russian and U.S. space station components will be blasted into space. As for Mir, it may have outlived its usefulness. But even if recurring problems forced the space station into retirement, a NASA spokesman said that would not effect the timing of its much larger successor.

Maclean's July 21, 1997