CAPE CANAVERAL, Fla., Aug. 4 (AP) — NASA launched a Mars lander on Saturday, beginning a 422-million-mile journey scheduled to culminate next spring in the first landing within the planet’s Arctic Circle.

An unmanned Delta rocket bearing the craft blasted off on time before dawn.

After the blastoff, engineers inside launching control worried as they awaited contact with the spacecraft. Charles P. Dovale, the launching director, finally confirmed success, one and a half hours into the flight.

“Everything appears normal, but it was a little bit of anxious moments there,” Mr. Dovale said. “It seemed like an eternity but it was about 20 minutes or so where we weren’t sure.”

Only 5 of the world’s 15 attempts to land on Mars have succeeded. If this one goes as planned, the spacecraft will set down on the Martian Arctic plains on May 25, 2008, and spend three months scooping up soil and ice, and analyzing the samples in minuscule ovens and mixing bowls.

The craft, named the Phoenix Mars Lander, will be looking for traces of organic compounds in the baked and moistened samples, which would be a possible indicator of conditions favorable for life, either now or in the past.

If organic compounds are present on Mars, they are most likely preserved in ice. That is why NASA is aiming for the planet’s high northern latitudes, where ice is almost certainly lurking just beneath the surface.

Only about six inches of soft red soil should cover the ice, and so the digger should not have to probe too deeply. The ice is expected to be as hard as concrete, and a drill on the scoop will help gather frozen samples. Some dirt and ice samples will be baked and their vapors analyzed. Other soil samples will be mixed with water on the craft and the muddy soup will be examined by onboard microscopes.

Mars landings are especially risky. Only 5 of the 15 American, Russian and European efforts have worked, all of them American successes beginning with the 1976 Viking touchdowns. The Phoenix team said it did everything possible to test for failures and will continue to do so as the spacecraft flies to Mars. The entire mission costs $420 million.

NASA has never tried to land a spacecraft on Mars at such a high northern latitude. A lander intended for the red planet’s South Pole went silent immediately upon arrival in 1999. That failure, combined with the loss of the companion Mars orbiter, prompted NASA to cancel a 2001 lander mission. The parts from that scrapped mission were used for the Phoenix, so its name alludes to the mythological bird that rises from its own ashes.

The Phoenix could help pave the way for human visitors, especially if it confirms the presence of frozen water in large amounts near the pole, said Michael Meyer, the lead Mars scientist at the National Aeronautics and Space Administration.