成功着陆后，重约772磅(约合350公斤)的“凤凰”号将在原地等候15分钟，待着陆掀起的尘埃物质落定，它将展开太阳能电池板，升起气象天 线杆，将周围环境的第一批照片传回地面。在接下来的几个火星日，“凤凰”号将检查机载仪器，伸展机械臂铲起第一堆火星土壤样本。一个火星日约比地球上的一 天长40分钟。在度过第10个火星日之前，“凤凰”号将进入“挖掘”阶段，每天有两小时用来挖土壤，这个阶段预计将占据此次任务的绝大部分时间。

The first-ever landing of a probe near Mars' north pole happened smoothly on Sunday, NASA confirmed.

The Mars Phoenix Lander, completing a 296-day, 422-million-mile journey, closed in on the Red Planet with a 50-50 chance of a successful touchdown on its arctic plains, NASA officials said.

The landing -- dubbed the "seven minutes of terror" -- was a nerve-wracking experience for mission managers, who have witnessed the failure of similar missions.

Despite that, they could hardly contain their excitement. In mission control at NASA's Jet Propulsion Laboratory in Pasadena, California, they celebrated the lander's much-anticipated entry.

Historically, 55 percent of all Mars missions have ended in failure. VideoWatch the challenges the mission faced »

The mission of the Phoenix is to analyze the soils and permafrost of Mars' arctic tundra for signs of life -- past or present.

The first pictures from Phoenix were expected to be revealed at 9:43 p.m. ET.

Phoenix is equipped with a robotic arm capable of scooping up ice and dirt to look for organic evidence that life once existed there, or even exists now.

"We are not going to be able to answer the final question of is there life on Mars," said Smith, the optical scientist on the team. "We will take the next important step. We'll find out if there's organic material associated with this ice in the polar regions. Ice is a preserver, and if there ever were organics on Mars and they got into that ice, they will still be there today."

Earlier, officials said the spacecraft was expected to be traveling at 13,000 mph when it hit the Martian atmosphere. Onboard computers were supposed to deploy its parachute, jettison its heat shield, extend its three legs, release the parachute and finally fire its thrusters to bring it down for a soft landing.

The twin to the Mars Polar Lander spacecraft, Phoenix was supposed to travel to Mars in 2001 as the Mars Surveyor spacecraft. They were originally part of the "better, faster, cheaper" program, formulated by then-NASA Administrator Dan Goldin to beef up planetary exploration on a lean budget.

But Polar malfunctioned during its entry and descent into Mars' atmosphere in 1999 and crashed. Technical investigations later concluded that as many as a dozen design flaws or malfunctions doomed the spacecraft.

The failure of that mission, as well as another spacecraft called the Mars Climate Orbiter the same year, led NASA to put future missions on hold and rethink the "better, faster, cheaper" approach. Mars Surveyor went to the warehouse. iReport.com: Send your photos, video of space

"The trouble is somebody forgot the 'better' part," said Weiler. "By pushing the 'faster and cheaper' part so hard, engineers were forced to make decisions that weren't necessarily the best and right decisions. And that led to both the failures of the Mars Climate Orbiter and ultimately the Mars Polar Lander and eventually the entire Mars program."

But all was not lost. In 2003, Smith proposed a plan to re-engineer the Mars Surveyor and fly it on a mission to look for signatures of life in the ice and dirt of Mars far North. Mars Phoenix, literally and figuratively, rose from the ashes of Surveyor. Learn about NASA's past missions to mars »

Engineers set to work, testing and retesting the onboard system to ferret out and fix all the flaws they could find.

The Phoenix landing site was targeted for the far northern plains of Mars, near the northern polar ice cap. Data from the Mars Odyssey spacecraft indicate large quantities of ice there, probably in the form of permafrost, either on the surface or just barely underground.

"Follow the water" has become the unifying theme of NASA's Mars exploration strategy.

In 2004, the rover Opportunity found evidence that a salty sea once lapped the shores of an area near Mars' equator called Meridiani Planum. Astrobiologists generally agree that it's best to look for life in wet places.

"There is no life on Earth where there isn't water," Weiler said. "However, where there's water, you find life, especially if you have organics, organic material and energy."

Smith believes that the mission probably will find organic footprints of life.

"Whether it's in the northern plains, I have no idea. But the universe is an immense place. In our Milky Way, we find hundreds of planets, and those are just in the nearby stars," he said. "So there must be huge astronomical numbers of planets in the universe."

So are we really alone? "I suspect not," Smith said.