EDWARDS AIR FORCE BASE, Calif. (AP) _ Space shuttle Challenger came home with a slightly scorched nose but with only 18 heat-resistant tiles damaged on re-entry, the lowest number ever in 22 shuttle missions, officials said today.

Ending a 3-million-mile voyage, the spacecraft touched down Wednesday on the Mojave Desert in a test of a new landing mechanism designed to allow the shuttle to resume landing on a shorter, concrete runway at Kennedy Space Center in Florida.

West German scientists said its treasure trove of scientific data would provide impetus for more international cooperation in space.

National Aeronautics and Space Administration spokeswoman Leslie Neihouse said the shuttle would be returned to Florida on Sunday. She said the number of tiles damaged was a record low, while orange marks on Challenger's nose were caused by heat during re-entry into Earth's atmosphere.

She added that the preliminary investigation of the landing mechanism called nose-wheel steering ''looked very good'' but that further review of the device would be conducted at Johnson Space Center in Houston.

The shuttle's brakes were in excellent condition, she said.

Astronauts and NASA officials were happy with the spacecraft's performance on the 22nd shuttle flight, and West German officials were delighted with the load of scientific data brought back from the seven-day, 45-minute flight.

''It was a beautiful mission that gives our scientists data to prepare the way for future missions,'' said Dr. Hermann Strub, a spokesman for West Germany's federal Ministry for Research and Technology.

West Germany paid NASA $64 million to haul the European-built Spacelab and a record crew of eight astronauts into orbit. Strub said the mission lead to U.S.-European cooperation in development of a space station in the 1990s.

James Beggs, administrator of the National Aeronautics and Space Administration, agreed that the mission enhanced joint space efforts.

''It gives us a lot of confidence that we can proceed to the space station,'' Beggs said, noting that international crews would be routine on an orbiting space platform.

Two West German scientists, Ernst Messerschmid and Reinhard Furrer, and a Dutch researcher, Wubbo Ockels, worked with American payload specialists on experiments in weightlessness, materials processing and crystal growth. During 111 orbits, the scientists completed 75 of 76 experiments devised by West Germany and the European Space Agency.

''We demonstrated that we can bring many countries on a shuttle mission and with cooperation, get a lot of work done,'' pilot Steven R. Nagel said before departing for Johnson Space Center in Houston with commander Henry W. Hartsfield and mission specialist James F. Buchli.

After Challenger glided in, using new nose-wheel steering equipment, the Europeans and astronauts Bonnie J. Dunbar and Guion S. Bluford were whisked away for medical tests. The group had performed personal experiments designed to test the physical effects of space travel.

Scientists are attempting to find out why about half of all astronauts suffer disorienting illness during space flight.

Hartsfield said there were no problems with the orbiter during its ninth space flight, but NASA technicians were investigating the source of orange scorch marks on Challenger's nose.

Jesse Moore, NASA's chief of space shuttle operations, said the orange marks appeared to be from water-proof coating that burned. But he said more investigation was needed.

The nose-wheel steering mechanism could lead to resumed landings in Florida after one more test on a shuttle due to land at Edwards in December, he added.

NASA wants to resume Florida landings to shorten the time used in launch preparations. The space agency has used the unlimited runway on the desert since a tire blew during a landing in Florida last April.

The computer-guided nose-wheel steering mechanism is intended to replace the use of alternating brake pressure which has kept the shuttle on a straight path during landings.

In the future, Beggs said people would benefit from substances that can only be manufactured in space, such as the crystals aboard Challenger that may lead to improvements in electronic semiconductors.