What if we actually did find life on Mars? If life--even microscopic life--is found in space, humanity's claim to uniqueness in the universe would be challenged.

• Author: Broad, William J.
• Position: National - Cover Story

The story of astronomy is one long, slow assault on our sense of self-importance. The ancients thought they were at the center of the universe, with the sun and the stars moving around them. In the 16th century, the Polish astronomer Nicolaus Copernicus dislodged the Earth from its place of glory and put the sun in the center. Before long, astronomers discovered that our own galaxy, the Milky Way, is just one of billions of star parties.

Our human sense of self-importance, already staggered, could be in for more knocks with the human barrage of Mars. With the landing of two rovers, Spirit and Opportunity, on Mars in January, the human claim to uniqueness in the universe could be challenged if life, no matter how small, is found there.

Beyond that, President Bush's plans to put an American colony on the Moon and then to land astronauts on Mars suggests astounding scientific possibilities. But the history of bold visions for human spaceflight is littered with more tragedies, failures, delays, and cost overruns than clear successes. Many in the space community believe the Mars goal is reachable. But they also question whether the country has the political will and NASA, the space agency directing the effort, the technological prowess to make it happen.

"NASA has gotten obese and encumbered," says Rick N. Tumlinson, a founder of the Space Frontier Foundation in Nyack, N.Y. "It's like a former Olympic athlete eating potato chips and drinking beer while watching reruns of past glories."

When the rovers began their work

on Mars in January, they examined rocks, but their ultimate purpose was to look for water and what seems to be its nearly inevitable companion, life. The rovers may find living organisms--tiny microscopic Martians are more likely than the green antennae-sprouting beings of science fiction--or fossil evidence of prior life. Even if just one little Martian were to come to light, however small and ugly, old and desiccated, it would mean that we are not alone in the universe.

The current hunt for lift on Mars goes back to the failure in 1976 of two Viking landers to find signs of life on the Martian surface.

But in recent years scientists on Earth have found life forms thriving in super-hot vents at the bottom of the oceans as well as in Arctic wastelands. Scientists now theorize that Martian lift' may exist below ground. "It's not crazy to ask if there are oases where life might still exist," says Andrew H. Knoll, a biologist at Harvard who studies early life on Earth, and the possibility that it exists elsewhere.

Scientists...