The Phoenix Mars Lander will blast off from Cape Canaveral, Fla., aboard a Delta II rocket on a 423-million-mile trip. The three-week launch window begins Friday.

Los Angeles ? A three-legged NASA spacecraft with a long arm for digging trenches is going to the Martian north pole to study whether the environment is favorable for primitive life.

But before it can start its work, the Phoenix Mars Lander must survive landing on the surface of the rocky, dusty Red Planet, which has a reputation of swallowing manmade probes. Of the 15 global attempts to land spacecraft on Mars, only five have made it.

“Mars has the tendency to throw you curve balls,” said Doug McCuistion, who heads the Mars program at NASA headquarters.

Phoenix, which is pieced from old hardware that was shelved after two embarrassing Mars failures in 1999, will blast off from Cape Canaveral, Fla., aboard a Delta II rocket on a 423-million-mile trip. The three-week launch window opens Friday.

Unlike the durable twin rovers near the equator, the Phoenix Mars Lander will sit in one place and extend its long arm to dig trenches in the permafrost and scoop up soil for analysis. Made of aluminum and titanium, the 8-foot-long arm acts like a backhoe and can dig down 20 inches and rotate.

Although Phoenix lacks the tools to detect past or current life, scientists hope it will shed light on whether the northern arctic possesses the signature ingredients for microbes to exist.

The lander should arrive at Mars 10 months after it launches and touch down in the northern plains for its three-month mission. If successful, it will be the first time since the Viking missions three decades ago that a robot will drill beneath the Martian surface.

Once it lands, Phoenix will heat the soil samples in miniature ovens to study their chemistry. The lander can detect the presence of organics, although it won’t be able to tell if there’s DNA or protein, said principal investigator Peter Smith of the University of Arizona, Tucson.

The landing site was chosen because previous spacecraft found evidence that frozen water lurked below the surface. Some believe the shallow valley measuring about 30 miles wide might be the remnant of an ancient sea. However, Phoenix will look for evidence of liquid water that may have existed as recently as 100,000 years ago.

There’s no water on the arid Martian surface today, but Phoenix’s job is to find out whether the underground ice may have melted, creating a wetter environment. Scientists generally agree that water, along with the presence of organic materials and a stable heat source, is needed to support life.