The skies around Mars are getting crowded, and traffic on the ground will soon increase, too. The United States and Europe are sending landers to the Martian surface to provide a broader and closer view of the Red Planet. A major goal is to find water and evidence of life.

After a seven-month journey, the touchdown of the European Space Agency's Mars probe is imminent. Its Mars Express spacecraft deployed a lander last week for a Christmas Day arrival on a flat plain north of the planet's equator. Named "Beagle" after the ship that 19th century British naturalist Charles Darwin sailed to the Galapagos Islands, it will parachute to a cushioned landing and seek signs of life from a stationary location. The mother ship will orbit, scanning with radar for underground water.

European Space Agency spokeswoman Jocelyne Landeau says the lander below will check the atmosphere for traces of methane produced by living organisms and search for other signs of life in rocks.

"We are going to grind holes into rocks and find out whether you have any form of life somewhere, present life or past life. Of course, we are not going to find a flower or an animal on Mars. We are going to find probably microbes or bacteria," he said.

The Mars Express mission is similar to a pair of U.S. probes that are not far behind it. "Mars is starting to get pretty big in the windshield," he said.

Steve Squyres of Cornell University is the principal investigator for the U.S. landers, named Spirit and Opportunity, which are to land on opposite sides of the barren planet on January 3 and 24 respectively.

"The scientific focus is to determine whether Mars was ever a place that could have supported life at its surface," he said. "If you look at the surface of Mars today, it's a desolate place. Yet we see these tantalizing clues dry river beds and lake beds, the kinds of minerals that you see formed by liquid water. These are giving us hints that in the past Mars might have been a very different sort of world."

NASA has been trying to return to Martian soil since its last successful landing in 1997. That mission parachuted the Pathfinder lander down in a protective airbag, delivering a small rover that analyzed rocks and took stunning images of the terrain. NASA failed to repeat that success in 1999 when it lost contact with a lander that used rockets to slow its descent. Months earlier, it had lost communications with an orbiter as it reached Mars.

The U.S. space agency hopes its current mission will regain the lost momentum. The director of the NASA center in California that is in charge of the project, Charles Elachi, says the agency has revived its 1997 landing strategy, so Spirit and Opportunity are to float down and bounce to a stop before deploying two robotic rovers, like the European effort.

"People ask me, can we guarantee success? Of course not. But on the other hand, I would say the team deserves it because they have done everything humanly possible to minimize risk and and enhance our possibility of succeeding," he said.

The two new U.S. rovers are bigger, more capable, and can roam much farther than the one six years ago, up to one kilometer during the 90-day missions. For the first time, they will be able to steer themselves around obstacles without specific commands, and see rocks in much finer detail.

NASA's chief of space science, Ed Weiler, says each is a backup for the other.

"We have built two rovers because of the science opportunities, but a side benefit of flying a pair of rovers hopefully increases the opportunity for minimum success," he said.

A Japanese spacecraft named Nozomi was to have been in the vanguard of this international Mars fleet. It was to have circled the red planet, studying why its thin atmosphere has leaked into space. But the Japanese space agency was forced to let the spacecraft fly by Mars earlier this month because defective equipment prevented it from entering orbit.