OK, Mars fans, here's the scoop: Efforts to explore the red planet are about to go underground.
Saturday morning, the Phoenix Mars Lander is set to launch from the Kennedy Space Center on a 423-million-mile, 10-month voyage to the planet. The payload – essentially a high-tech Tonka Toy for digging tiny trenches on Mars – opens a new decade in Mars exploration, following 10 years of spectacular discoveries from a series of orbiters and rovers.
Since Mars Pathfinder's lander-rover combo and the Mars Global Surveyor orbiter reached Mars during the summer of 1997, surface rovers and orbiters from the US and Europe have revolutionized scientists' views of the planet. But these missions either have peered at the planet from on high or scraped at rocks on the surface.
By contrast, the Phoenix Mars Lander will vicariously take researchers where none of them have gone before.
Previous missions have striven to re-create the story of water on Mars in the planet's distant past. Phoenix aims to track the activity of water in the polar regions today by analyzing the chemistry of soil and water to depths of nearly two feet.
If all goes well, the lander will touch down in the Martian "Arctic" next May. Over the following 90 Martian days (92 Earth days), its mini backhoe – a nearly eight-foot-long arm wielding a bucket roughly the size of a box of large kitchen matches – will dig progressively deeper into the surface. The data it collects hold the key to another burning question: Could the polar regions serve as nurseries, or at least storage freezers, for microbial life today?
Freezer for life
The Martian surface is bathed in radiation too intense for simple life forms to survive. But layers of soil and ice could provide shielding. And, researchers add, periodic shifts in the planet's orbit around the sun could warm the surface enough to turn the ice to water and release microbe-friendly nutrients locked in the soil.
At first blush, it might seem that the water-ice caps themselves would be good places to study today's water. But scientists rejected that for a polar landscape reminiscent of Alaska's North Slope or northern Greenland.
"We didn't want to land on exposed ice; it's a very difficult environment" for a lander, says Peter Smith, a University of Arizona planetary scientist and the project's lead investigator. Moreover, it would be difficult to get to the soils, and soil chemistry is key to the questions the team is asking. "It's the transition of soil from a volcanic mixture into clays and salts" that tells water's tale, he says.
Indeed the subsurface ice detected in the region from the Mars Odyssey orbiter could be the remains of an ancient sea, researchers say. The ice appears within three feet of the surface.
"We also think it's a more likely environment for microbes on Mars – more of a habitable zone" than any exposed ice, Dr. Smith adds.
Baking the soil for clues
The lander is designed to use a stir 'n' bake approach to analyzing the soil samples. The scoop deposits tiny amounts of soil into one of eight furnaces, each roughly the size of a baby's pinky. The ovens will slowly heat the samples to 1,800 degrees Fahrenheit, analyzing the chemical composition of gases formed along the way.
A wet lab boasts four beakers the size of tea cups to serve as mixing bowls for Martian soil samples and water brought from Earth. The hardware gradually will add other chemicals to the mixes and measure the results. And microscopes will capture images of soil and ice particles.
For those who prefer weather to dirt and ice, the lander carries a complete weather station that will help track what passes for a water cycle on Mars. Two cameras round out the instrument package. The mission is unlikely to enjoy the typical NASA extension; the high latitude and eventual Martian winter will ensure that the lander's solar panels don't get enough sunlight to do their job after the three-month mission expires.
Several of the instruments were originally built for the Mars Surveyor 2001 and the Mars Polar Lander. But the Surveyor lander fell to the budget ax in 2000, following the failure of two other US Mars missions, including the Polar lander, the year before. Several of the instruments have been upgraded during the interim and all have been extensively tested. Still, "it's important to recognize that we're buying a used car here," says Barry Goldstein, the mission's project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
If the Phoenix Lander represents a resurrection of sorts for two previous missions, the past decade's worth of Mars missions have done the same for Mars.
After the two Viking missions launched in the mid-1970s, "there was a feeling that, gosh, maybe this planet is really just kind of dead, except for the dust storms that come and go," says Richard Zurek, chief scientist for Mars exploration at JPL.
But the orbiters and rovers have uncovered evidence of episodes of mineral formation on the surface. Within the past decade, Mars scientists have seen changes on the slopes of gullies that suggest sudden outbursts of trapped water. And the planet may have enough of a residual energy source that it hosts hot springs – or at least did during recent geological periods.
"That's encouraged us that Mars may still be alive today in the sense of moving water around the planet" and other activities, Dr. Zurek says. Taking a page from a Mel Brooks script, he adds with a chuckle: "It's alive!"