Mars lander launches new decade of exploration

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.

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