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.

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 for the European orbiter Mars Express, which began circling Mars in December, say the craft's radar detected frozen water on the planet. The two current U.S. rovers would have to be extremely lucky to stumble on signs of life on the Martian surface. A further exploratory flight planned in the next decade would drill into the surface and return material to Earth for analysis.

THE REAL MARTIANS?

If Martian life is found, it may be similar to Earthling life, suggesting that it might have come from Earth via cosmic collisions. (Or perhaps Earth life came from Mars by the same method, meaning we, in effect, are Martians.)

But if Martian life is distinctly un-Earthlike, it could mean evolution functions nearly anywhere in the universe--fueling speculations about the existence of sentient beings far more advanced than us.

But finding lift' on Mars--even if it's there--will be far from easy, scientists warn. The perils of space flight, for machines or humans, are savagely daunting. When the Spirit rover fell silent during its first week on Mars due to software problems, NASA scientists had to scramble to patch the problem.

In addition, disasters big and small have struck the federal space establishment with alarming regularity of late: Satellites have failed, and the space shuttle Columbia blew up just last year, killing all seven astronauts aboard. In January, the International Space Station was leaking air. A new generation of spy satellites is behind schedule and billions of dollars over budget. Landsat 7, a federal satellite, is sending back fuzzy pictures of Earth.

Such problems add costs--a fate suffered by earlier space projects. The space-shuttle program, announced in 1972 by President Richard M. Nixon, ended up costing 10 times its original estimates. A moon and Mars exploration plan proposed by the first President Bush in 1989 fizzled when the cost estimates bit $400 billion.

HUBBLE & SHUTTLE FINALES

For his Mars program, President Bush plans only modest increases in space spending: $1 billion in new money with $11 billion from existing NASA programs. To economize, NASA has already announced the phasing out of the current shuttle fleet by about 2010. NASA has also canceled plans to service the Hubble Space Telescope, which is expected to die in orbit sometime in the next 10 years.

Such choices, though, are essential to make the Mars program work, supporters say. But other space experts say more difficult choices lie ahead. Howard E. McCurdy, a space historian at American University, said that most presidential initiatives went sailing off course because of insufficient discipline and seriousness.

But a Mars landing on the President's schedule, while difficult, is possible, he says. "Doing it successfully would mean a total transformation of the space program, as radical as happened from 1961 to 1966." The problem, he says, is that "for 30 years NASA hasn't had that discipline."

RELATED ARTICLE: Opinion.

If Mars Trips Were Just One-Way ...

Professor Paul Davies of the Australian Center for Astrobiology on his idea for exploring Mars

President Bush has announced that the United States is headed for Mars, but without some radical improvements in technology the costs of sending astronauts on a roundtrip to Mars are prohibitive.

At its closest point in orbit, Mars lies 35 million miles from Earth. Martian gravity is greater than the moon's, so transporting propellant for a return trip makes the expense of a launching soar

The President's suggestion of using the moon as a base for a Mars journey could turn into a costly sideshow. There is, however, on obvious way for humans to explore Mars. The answer lies with a one-way mission.

Most people react with instinctive horror at the suggestion. But Mars is theoretically able to support a permanent human presence. If provided with the right equipment, astronauts would have a chance of living there for years.

Every two years the orbit of Mars creates an opportunity to send fresh supplies at a reasonable cost. An initial colony of four astronauts could make their own oxygen, grow some food, and even initiate building projects.

It's true that accidents or equipment failures might doom the colony. And medical problems from the lower gravity and increased cosmic radiation that penetrates the thin atmosphere would certainly shorten the astronauts' tires.

Would it be right to ask people to accept such conditions for the sake of science, or even humanity? The answer has to be yes. Soldiers and test pilots already take significant risks on our behalf. A century ago, explorers set out to trek across Antarctica in the fur knowledge that they could die in the process.

It would make sense to pick mature, older scientists with reduced life expectancy. The early outpost would eventually grow' to the point of being self-sustaining.

If during the next millennium, civilization on Earth were destroyed by an asteroid, a killer plague, or a global war, a Martian colony could keep civilization alive until Earth could be reverse-colonized from Mars.

Would NASA entertain a one-way policy for human Mars exploration? Probably not. But other, more adventurous space agencies in Europe or Asia might. The next giant leap for mankind won't come without risk.

DISCUSSION QUESTIONS

* What do you think drives humans to explore outer space?

* Do you believe human beings are unique in the universe?

* Would you consider a career in the U.S. space program?

TEACHING OBJECTIVES

To help students understand both the rewards and the difficulty of space exploration, and to help them think about the implications for humanity if life exists elsewhere in the universe.

CLASSROOM STRATEGIES

CRITICAL THINKING: The article discusses possible reaction to the discovery of life--past or present--on Mars. Note the reference to a challenge to human uniqueness in the universe.

Ask students how they think they might react if space exploration discovers evidence of other forms of life on Mars or elsewhere in the universe. Would such a discovery be frightening? Exciting? How would the discovery of life affect religious beliefs, specifically religious explanations of the origin of humanity and the role of a superior being in human development?

DEBATE: Students should understand that there is serious debate in the country about the amount of resources (read money) devoted to the space program. Break the class into two groups. Group A should present a brief argument supporting the value of space exploration. Group B should present a brief argument that the U.S. should focus its energy and resources on earthly needs. Students' arguments should be as specific as possible.

(You might also ask students whether they believe the U.S. is compelled to continue space exploration as long as other countries--Russia, China, and the European Union, for example--pursue their own space programs.)

ONE-WAY TRIP: Refer to the sidebar on a proposed one-way Mars mission. Ask students whether such a mission might someday rake place or Trill never take place. Note comparisons to test pilots and Antarctic explorers. In what ways are these comparisons with a one-way Mars mission valid or invalid? (Note that some early American settlements, like Roanoke, Va., died out.)

WEB WATCH: Go to www.nasa.gov /externalflash/m2k4/index1.html, a NASA Web site dedicated to the exploration of Mars. Numerous links offer background on Mars, astronauts, and other aspects of the space program.

DIRECTIONS: Circle the letter next to the best answer.

1. President Bush has proposed a sweeping
   change in federal laws governing

   a the use of illegal drugs.
   b mandatory education.
   c immigration.
   d the selection of judges.

2. The President has also proposed
   that the U.S. establish a

   a department of terrorism research.
   b department of tax reduction.
   c base on the moon.
   d military academy for women.

3. In addition, the President pushed through a $400 billion
   benefit for senior citizens to help them pay for

   a housing.
   b prescription drugs.
   c visits to medical doctors.
   d food and clothing.

4. Both political parties are changing their campaign
   strategies. This year there will be a lot more

   a attention devoted to national campaign advertising.
   b focusing on the state of the economy.
   c debates.
   d face-to-face appeals to voters.

5. One of the groups Democrats build their
   grassroots campaigns around are

   a labor unions.
   b religious congregations.
   c business associations.
   d immigrants.

6. Republicans are counting on the fact that Americans
   have never voted a President out of office

   a when there's been a high rate of unemployment.
   b during a war.
   c when the stock market has been rebounding.
   d when his party has controlled both houses of Congress.

ANSWER KEY

1. (c) immigration.

2. (e) base on the moon.

3. (b) prescription drugs.

4. (d) face-to face appeals to voters.

5. (a) labor unions.

6. (b) during the middle of a war.

William J. Broad is a science reporter for The New York Times.