— The Mars exploration rovers should take seven months to get to the Red Planet. But for Steven W. Squyres, the journey has already lasted seven years.
"This is going to be, when we pull it off, humanity's first great voyage of exploration of this century," says Squyres, an astronomy professor at Cornell University. He is principal investigator for the mission, and was part of the small team that first proposed it back in 1995.
It has been slow going since then, even though the two little ships will need to go 25,000 miles an hour to leave Earth's gravity on the way to Mars. In the last several years, the rover plan has gone through rejections, approvals, cancellations, delays and a final hurry-up to get to the launch pad.
"It's been a roller coaster," says Squyres. "You lose sight of the fact that, yeah, we're actually sending two robots to Mars and exploring."
The 400-pound rovers, each with six wheels, nine cameras, and five scientific experiments on board, are designed to spend at least 90 days rolling slowly across the Martian surface. They are not designed to look directly for life, but their examination of the rocks and soil around them may suggest whether conditions on Mars are, or ever were, right for living things.
Beagles, Moles, and Rats
It is a busy time in the business of exploring Mars. A British-led team, using a Russian rocket, launched its own probe June 2. It consists of a main ship, called Mars Express, which should orbit the planet after releasing a small lander called Beagle 2. (The name is a reference to Charles Darwin, who formed his theory of evolution after traveling the world on a ship called the Beagle.)
British scientists celebrated after the launch, but Colin Pillinger, the team leader, called it "only the quarter-finals."
"The exciting bit, the bit we're going to enjoy most," he said in an interview with the BBC, "is doing the science to discover, is there, or was there, life on Mars."
To that end, Beagle 2 has a robotic arm and 12 tiny ovens to heat soil samples and see what gases they emit. Certain chemical compounds could suggest the presence of living organisms.
Some soil samples will be gathered by a mechanical "worm" — a device that can burrow into the ground, then be pulled back on a lanyard into the lander.
NASA's two rovers are not specifically looking for life, but they are looking for conditions that may have been friendly to life in the past. The Martian surface today is cold, more dry than any earthly desert, and sterilized by the ultraviolet rays of the Sun. But clearly, at some time in the past, Mars was warmer and wetter. Its surface is crisscrossed by ancient, dried-up river valleys.
Before they can get a look, the rovers will have to survive the seven-month trip to Mars, and the violent, chancy landing there. They will descend by parachute, then fall the last few feet onto the surface in protective air bags.
Unlike the Mars Pathfinder rover six years ago, which had very limited range, the new rovers are meant to travel for months on their own — probing the rocks, sending pictures and data to the scientists back on Earth. Since many of the best clues may be hidden beneath the rocks' weathered outer layers, engineers have devised a "RAT" — short for Rock Abrasion Tool — designed to cut into boulders so other instruments can get better samples.
What if the rovers, or later missions, find suggestions of life?
"If that happens," says Squyers, "we've learned something really profound. We've learned that we're not alone in the universe.
"On the other hand, we could go to these places and find that they were warm, they were wet, they were just the kind of place you'd think life would be happy — and yet, somehow, life didn't emerge there.
"If that happens," he concludes, "we've learned something really profound about what it takes to make life happen. It makes our little planet a lot more special."