Prepare for landing on Mars
— -- Once a graveyard for space probes, Mars is now a prime destination in scientific exploration. NASA's latest lander aims to uncover fresh territory on the Red Planet.
Launched Aug. 5, the space agency's Phoenix mission is on a 10-month trip to Mars' northern plains. If it lands as planned, the $400 million Scout lander will dig into the soil and ice, searching for signatures of life-friendly conditions in the planet's ancient past.
"We now know there are massive ice deposits where Phoenix is landing," says mission scientist Diana Blaney of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The launch comes amid a renaissance in Martian studies as the durable Mars rovers — the rolling geology labs that landed in January 2004 — head toward a fourth year of exploration and a fleet of orbiters circle the planet.
"Right now, it's exciting, and things are getting better and better in what we're learning about Mars," says Louis Friedman, head of the Planetary Society in Pasadena.
In "the dark days of 1999," as Friedman says, Mars science seemed jinxed with the crash of NASA's $120 million Mars Polar Lander and the $125 million Mars Climate Orbiter late that year. The Phoenix mission uses instruments designed for the lost polar lander and follows in its intended footsteps, but with better direction, Blaney says: "We know the water ice is there now."
"I remember the dark times," Blaney says. "Now it's a lot busier." A dust storm on Mars that temporarily shut down the rovers, which are fueled by solar power, was almost helpful to mission scientists, says Blaney, who is also deputy project scientist for that mission. "We needed a chance to catch our breath."
Search for water runs deep
"Follow the water" has been NASA's mantra for exploring Mars in the past decade as it searches for signs of life's crucial ingredient. Since the rover called Opportunity (the other one is Spirit) discovered rock layers left behind by salt-laced waters, new discoveries have fundamentally changed the scientific view of Mars, says William Hartmann of the Planetary Science Institute in Tucson.
"If anything, the last decade of Mars exploration has intensified our excitement about tracking the history of water on Mars," he says.
A fistful of missions have evolved into a full-fledged scientific network:
•The 2001 Mars Odyssey orbiter, which reported the first signs of ice layers under the Martian surface.
•The 2003 European Space Agency's Mars Express orbiter, which found evidence of even deeper ice layers.
•The 2004 Mars Rovers, which are persevering more than two years after landing on Mars. The Opportunity rover is preparing to enter its deepest crater yet, Victoria, to search for sedimentary rock.
•The 2006 Mars Reconnaissance Orbiter, which has probed the Martian atmosphere and returned high-resolution images of the rovers crawling on the planet's surface.
Earlier this year, NASA reported the loss of the 1997 Mars Global Surveyor, which famously spotted signs of recent gullies in Martian craters in 2000, fueling the search for signs of water. Those hopes have been borne out in the rover results and more recent findings.
"Yes, it looks like there was a lot of water," says Hartmann, part of the Mars Express science team. The oldest parts of Mars show lots of clays and water-soaked minerals, for example, suggesting formation in a wet climate billions of years ago. Later, the planet dried out, becoming the desert Mars now familiar in photos from the surface.
French and American scientists have found that the polar tilt of Mars nods up and down, perhaps as much as 70 degrees, toward the sun every 10 million years or so, Hartmann says. (Mars tilts 25 degrees now, close to Earth's tilt of 23.5 degrees, which is stable because of the moon's gravity.)
Computer models suggest that when the axis dips far toward the sun, heat shines down on the summer polar ice cap, which would explain signs of icemelts and water bursts. "We've gone from a picture of Mars as pretty arid to a place with probably some water on it," Blaney says. "If anything, it is starting to look a bit more like Earth."
Hartmann suggests the driving question is whether bacteria exists on Mars that have adapted to conditions and will "come to life" upon exposure to water.
A human on Mars?
The next big mission comes in 2009, when NASA hopes to land its nuclear-powered Mars Science Laboratory Rover, designed to answer Hartmann's question on whether Mars could have supported microbes.
"We need to connect the mission to future landings," says Friedman, whose society sponsored a DVD aboard the Phoenix lander that was packed with a story collection and the names of more than a quarter-million Mars mission supporters, intended as a library for future astronauts.
The real question in Mars exploration, he adds, is whether the success of the robotic missions can translate into astronaut landings.
"Mars is the eventual goal of any human space flight program," Friedman says. "For all the success we're having now, we have to remember it's not an ordinary thing to explore another planet."