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The Phoenix lander (artist's conception) will use its robotic arm to dig into the Martian permafrost. (Corby Waste/JPL)

Northern Exposure

We've already seen water ice on Mars. NASA's Phoenix lander will reach out and touch it.

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THE SQUARE, EARTH-TONE industrial building on North Sixth Avenue in Tucson, Arizona, has little of the proud, high-tech gloss of NASA’s Jet Propulsion Laboratory, traditional home of U.S. Mars missions. The historic NASA center in Pasadena, California, has neatly clipped lawns and squadrons of badge-wearing engineers and scientists, who work each day surrounded by memorabilia from decades of solar system exploration. Everything about the place fairly shouts Space science is our business.

But around this building in Tucson’s commercial flatland, the ambience is quite different: There’s a car repair shop, a day care center, a small dinosaur museum, and the hum of passing traffic. The main clue that something unusual is going on is the exuberant yellow and orange mural painted along one of the building’s broad sides. The work of art students from the University of Arizona and local high schools, it depicts a fiery trail from Earth to Mars, along which travel a chariot, a bird with flames for feathers, and an interplanetary robot.

A small sign near the entrance tells visitors that this is the home of Mars Phoenix, which happens to be the only mission bound for the Red Planet this year. NASA will launch the spacecraft in August and guide it to a landing on the Martian surface in May 2008. Once it arrives, though, day-to-day operations will be run out of this building, near the university campus. It’s a new model of doing business for a new generation of smaller, leaner, more innovative Mars Scout missions.

NASA sees these missions as a way to encourage fresh thinking: Ideas for Mars missions are proposed by scientists working outside the space agency rather than by staff scientists within. The Scouts augment bigger and more expensive missions like the Spirit and Opportunity rovers, which have been exploring the planet since 2004. The cost of the Mars Phoenix, about $400 million, is roughly half that of a typical NASA mission to Mars.

The Phoenix team seems to like the low-budget arrangement just fine. “The advantage of the Scout mission concept is that the whole thing is determined by the scientists who are working on it,” says Peter Smith, the mission’s tall, plain-spoken principal investigator. “The usual NASA strategy is to have a spacecraft with some general goals, and then scientists propose instruments for it. You get committees and overlaps and competing personalities.” The Scout teams are smaller and more collegial. The 25 co-investigators under Smith (compare that to 57 on the rover team) are a disparate bunch: eight from U.S. universities, nine from NASA centers, four from private contractors, and four from institutes in Britain, Germany, and Switzerland.

Together, they hope to take the next step in understanding a world that has become a familiar destination for planetary robots. For at least a decade, the mantra for NASA’s Mars exploration program has been “Follow the water.” If Martian life ever existed, the logic goes, the evidence would most likely be found in a zone marked by the presence of water. The current rovers have therefore spent more than three years examining rocks formed under wet conditions long in the past.

The Phoenix mission comes about as close to a single-minded search for water as anything NASA has done so far. While the Spirit and Opportunity rovers have done a good job of tracing the history of water, scientists hope that Phoenix will be the first spacecraft to directly sample it. “Everybody talks about water [on Mars], water signatures, water this and water that,” says Smith. “But they’ve never seen any.” Nor will Phoenix, at least not in liquid form. Scientists would be astonished to find running water on the Martian surface today—it’s far too cold. Water ice, though, is very likely to be found where Phoenix will touch down.

The lander will head straight for the Martian arctic and the broad belt of permafrost surrounding the planet’s north polar cap. Next May, if all goes according to plan, Mars Phoenix will bore into the atmosphere near the north pole at 12,600 mph. A heat shield, then a parachute, then a set of landing jets will reduce the craft’s speed until finally the 800-pound lander thumps down on three legs at about 5 mph. As with any planetary lander, this will be a harrowing time for the Phoenix team. “Seven minutes of hell” is how NASA project manager Barry Goldstein, who’ll be at JPL during the mission, describes it.

Once Phoenix is on the ground, two circular solar panels will extend from its sides and open like Chinese fans to provide power. A column of delicate tubing will rise like a stalk, with a stereo camera on top for panoramic photography. From the lander’s flat deck will extend a robotic arm equipped with small cameras, microscopes, and, most important, a shovel and small electric grinder—the same kind used for sculpting ice. Articulated like a backhoe, the arm can in principle dig a trench about two feet deep, at least in soft ground. The whirring grinder is designed to break frozen ground into manageable bits for the shovel to scrape up. Nobody expects the grinder to penetrate more than a fraction of an inch into the permafrost, which will be deep-frozen to about –130 degrees Fahrenheit.

Mission scientists believe the lander will find ice mixed with the soil just below the dusty surface. And some researchers, like Ray Arvidson of Washington University in St. Louis, a co-investigator with the robotic arm science team, expect to see, on close inspection, patches of hard, blue ice peeking through.

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