It is expected to arrive on Mars May 25, 2008 to analyze the red planet's icy soil.

The surface of Mars is an unfriendly place. Dust devils churn constantly, and temperatures average a chilly 64 degrees below zero. The poles are even nastier: frozen, often dark and deathly cold.

But astronomers think that arctic wasteland could harbor the tiniest hint of life. Today, NASA plans to test this theory by launching a probe to study soil and ice at the fringe of Mars' northern pole.

If everything goes well, the Phoenix spacecraft will parachute onto a frosty Martian plain next May or June. It would be NASA's northernmost landing on the Red Planet and the first spacecraft sent to capture and analyze Martian water.

To NASA scientists, it's also a chance for redemption. A similar polar explorer lost contact and is thought to have crashed while landing in 1999; another attempt to land on the planet failed in 2001. Spare parts from both these probes will be used on Phoenix, whose name was inspired by the mythical bird that rose from the ashes.

"Mars has a tendency to throw you curveballs," said Doug McCuistion, Mars Exploration Program director at NASA. To prevent another disaster, technicians have spent years fine-tuning Phoenix's landing equipment and technique.

Mission price tag: $420M

NASA officials said the extra attention to safety added at least $25 million to its price tag, which now stands at about $420 million. That's about $100 million more than the 2003 estimate for the mission.

In recent years, scientists have focused on searching for water on other planets because they think it offers the best chance of finding Earth-like life -- especially if the water is in liquid form.

Astronomers speculate that liquid water once carved the channels and gullies seen on Mars' surface today. But there was little evidence liquid water still existed on the barren surface -- until December, when NASA announced that scientists comparing nine years' worth of Mars photos had seen evidence of recent water flow, a sign that water may have briefly bubbled to the surface during that time.

Still, most of the planet's known water is frozen at the poles. That's why the landing site for Phoenix is a frost-covered plain a little south of Mars' north pole -- the equivalent of Alaska or Greenland on Earth.

Their belief is that this transition area between the frozen north and bone-dry equator -- which can reach 80 degrees at noon when Mars is closest to the Sun -- could have supported liquid water.

"If we could really find evidence that ice had melted, I think that would be a great result," said Peter Smith, a researcher from the University of Arizona who will manage the Phoenix mission along with the Jet Propulsion Laboratory in California. "If we could find organic material, that would be a huge result."

Either would suggest the possibility that life could exist on this part of the planet, he said.

Digging to find life

To study the ice and soil of Mars, Phoenix is outfitted with seven different tools. One is a nearly 8-foot, camera-equipped robotic arm that will claw the ground around the craft, dig until it hits ice and bring samples back to the lander.

The dirt and ice samples will be heated to 1,800 degrees so scientists can study whatever gases are released. The hope is to find hints of organic compounds that could indicate life.

Another instrument will test the acid and alkaline balance of the soil to see what type of microorganisms could live in that environment. Cameras and a weather station will give scientists a better idea of the surrounding area.

Two solar arrays will power the lander through its scheduled three-month mission. However, scientists hope Phoenix can retain enough juice to keep running as the seasons turn and this region gets colder and darker.

A side benefit of the Phoenix mission is that it should give NASA a better understanding of Martian ice and water as it prepares to send astronauts to the Red Planet sometime after 2020.

Before Phoenix can study the surface of Mars, however, it first must endure a nine-month, 423 million-mile journey that starts with a Delta 2 rocket scheduled to blast off at 5:26 this morning from Cape Canaveral Air Force Station.

Most worrisome for NASA is the harrowing Mars entry. Phoenix will have less than seven minutes to slow from 12,750 mph to about 5 mph just before landing.

To do that, the spacecraft will use a heat shield at the top of the atmosphere, deploy a parachute at eight miles up and then float down until its thrusters slow its fall to what NASA hopes is a gentle landing.

Mixed record on Mars

The agency's efforts to explore Mars have an uneven history. Two rovers continue to motor across the landscape years after 2004 touchdowns, but three U.S. missions failed between 1992 and 2000.

With this spotty track record, engineers took extra care to check Phoenix for problems. During one of these tests, they discovered a problem with an interface card that directs several of its functions.

Analysis showed there was a small chance that when Phoenix took pictures on descent -- as originally planned -- processing the images would reset the interface card. This would cripple the spacecraft's ability to take altitude and orientation readings essential for landing.

The problem was discovered too late to fix, so NASA officials decided to take only one photo on descent, instead of the planned 20 pictures. This would avoid the problem that was causing the interface card to reset.

Mark K. Matthews can be reached at mmatthews@orlandosentinel.com or 202-824-8222.

http://www.orlandosentinel.com/news/space/orl-phoenix0407aug04,0,2983630.story

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