BOSTON — To ancient civilizations, the planet Mars represented war and death. Tomorrow, scientists begin a 10-year quest to comb the Red Planet for signs of life.
Shortly after noon Eastern time, the National Aeronautics and Space Administration (NASA) is scheduled to launch the Mars Global Surveyor from the Kennedy Space Center in Florida.
The unmanned probe marks a fundamental shift in the way NASA conducts new space-science missions - away from big expensive spacecraft to smaller probes with specific objectives. It also heralds a new era of exploration of the mysterious, long-beguiling Red Planet by nations around the world.
NASA itself is planning to send eight Surveyor missions to Mars between now and 2005. Next month, the agency will launch the Mars Pathfinder to test a robotic rover for use on future flights.
In December, the Russians are scheduled to launch their Mars '96 mission, which will carry two probes, and Japan is planning an orbiter to the planet in August 1998.
Taken together, these missions not only will give scientists new insights into the geology, natural resources, and climate of the solar system's most Earth-like planet. If the effort uncovers definitive evidence of past or present life on Mars, it could provoke a shift in human thought as profound as the revolution sparked when Galileo discovered moons orbiting Jupiter - the first direct evidence that Earth was not the center of the universe.
The notion that organic life, at least in its most elementary forms, once existed on Mars received a boost late last week when three British scientists said that they had found evidence of primitive life in a second Martian meteorite.
Last August, researchers from Stanford University in California and NASA's Johnson Space Center in Houston reported that a 3.6 billion-year-old, potato-sized meteorite from Mars contained what they interpreted as fossils of tiny bacteria. In addition, they said, their meteorite contained organic molecules thought to have originated on Mars, as well as deposits of minerals typically formed through biological processes.
On Thursday, a British team from The Open University and London's Natural History Museum announced that they had examined NASA's meteorite and agreed with the US team's findings. They also reexamined a Martian meteorite in their own collection and found similar evidence of organic material and processes in the 180-million-year-old sample. "I believe I can say life existed and may still exist on Mars," said Ian Wright, an astronomer at The Open University during the press conference announcing the team's results.
Meteorite evidence remains controversial. At a recent meeting of the American Astronomical Society's Planetary Sciences Division, for example, two researchers from the University of Colorado at Boulder calculated that some of the the tell-tale mineral deposits, known as carbonates, in NASA's sample formed under hotter temperatures than those estimated by the NASA-Stanford team.
As the temperatures forming carbonates rise, the "possibility for the evolution of life goes down," says Kevin Hutchins, one of the two researchers. Yet even he and his colleague's higher estimates included temperatures that are cozy to some Earth-bound bacteria.
Although its climate is frosty by earthly standards (from minus 76 F. at the equator to minus 189 F. at the poles), the climate is believed to have undergone several thaws. These periods may have released large volumes of water, locked in polar caps or permafrost, that etched he Martian surface. Finding water, key for the development of life and an engine for climate, represents the overall goal of the Mars exploration program.
The attempt to probe Mars for signs of life, or at least for conditions that could have fostered it, underscores how NASA is changing the way it operates. Gone are the high-tech equivalents of ponderous Spanish galleons - large spacecraft crammed with experiments and costing from $600 million to $1 billion each.
Driven by shrinking budgets and advancing technology, the agency aims to build smaller craft for $100 million to $200 million each, with specific missions, to be launched every two or three years.
"We're conducting this 10-year [Mars] program for the cost of a major motion picture a year," says Donna Shirley, manager of the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Researchers benefit from the approach, she says, because they can adapt future orbiters to follow up on discoveries from earlier Surveyor craft. Moreover, if one fails, others are in line to replace it. Indeed, the Surveyor currently sitting atop a Delta rocket on Pad 17A takes advantage of spare instruments designed for the Mars Observer, which NASA launched four years ago. The Mars Observer failed in August 1993, three days shy of entering its orbit around the planet.
The Global Surveyor is intended to gather data on climate, terrain, and the distribution of minerals, rocks, and ice on the surface of Mars. Once it arrives at the planet, the craft will orbit the planet's poles. Its passing across the sunlit face will be timed to coincide with the Martian afternoon, so shadows cast on the surface will help define features for a digital camera, which will be able to spot objects as small as 9.5 feet across.
A laser altimeter will gather data allowing scientists to build topographical maps accurate to within 100 feet. Other instruments will store information about Mars's magnetic field, if it has one. The Surveyor will continue its observations for one Martian year (about two Earth years).