Beagle 2 - the next great Martian hope

Robot: The British-built spacecraft is seen as the best chance to solve the mystery of life on Mars.

Medicine & Science

December 15, 2003|By Michael Stroh | Michael Stroh,SUN STAFF

Eight days after arriving on the rock-strewn Martian plain of Chryse Planitia, Viking 1 sank its stainless steel claw scoop into the rust-tinted soil. It was 3:30 a.m. July 28, 1976. The first search for life on another world had begun.

But far from settling the question of extraterrestrial life, the expedition showed just how difficult it is to answer.

Viking's verdict: Mars is and always was dead. In the years since, however, scientists have questioned whether the spacecraft's instruments were sensitive enough. Others are bothered by baffling inconsistencies in the data it beamed back.

Of the new generation of robots closing in on the Red Planet this month, the British-built Beagle 2 may have the best shot of putting to rest the debate over what, if anything, Viking detected in the Martian dunes that summer day 27 years ago.

Each Viking was equipped with a trio of ingeniously designed biology experiments designed to pinpoint the presence of Martian microbes. Not long after the first scoop of Martian soil tumbled in, the automated biology labs began to signal signs of life.

But with the world watching, Viking scientists were reluctant to declare they had found Martians. So they turned to Viking's gas chromatograph-mass spectrometer. If Mars really harbored life, the spectrometer would see chemical fingerprints of carbon-based organic material.

It didn't. Gerald Soffen, the mission's chief scientist, was puzzled. "All the signs suggest that life exists on Mars, but we can't find any bodies!" he said.

Most scientists now think that Viking's life detectors saw a mirage, detecting chemistry, not biology.

But the absence of organic molecules on Mars remains a nagging mystery, says astrobiologist Christopher McKay of NASA's Ames Research Center in California. Organics, after all, have turned up all over the solar system - including the moon. Why not Mars?

Beagle 2 may finally solve the riddle. Tucked inside its compact clamlike shell, the spacecraft carries a more sophisticated and sensitive version of Viking's organic detector called the gas analysis package, or GAP.

Twelve tiny ovens will cook rock and soil samples to produce carbon dioxide gas. A mass spectrometer will measure the ratio between two isotopes of carbon, Carbon-12 and Carbon-13. On Earth, a higher concentration of Carbon-12 usually signals the presence of life.

The instrument also will sniff for gasses such as hydrogen, nitrogen, oxygen and methane, a substance that scientists believe would be present in the Martian atmosphere only if microbes were manufacturing it.

Since the planet is continually bombarded by life-neutralizing ultraviolet radiation and cosmic rays, Beagle 2 also will attempt to dig deeper for samples than Viking did. "The surface of Mars is fried," says Jeffrey Bada, a scientist at Scripps Institution of Oceanography in La Jolla, Calif.

Viking's robotic arm, he notes, could burrow no deeper than 8 inches or so - too shallow to find life. Beagle 2, on the other hand, has an instrument called a mole that can worm its way five times as deep to collect samples.

The lander has other tools, including an onboard microscope to inspect rock samples for biofilms (the slime produced by bacterial colonies) and ancient, microscopic fossils. But scientists consider either one a long shot.

If Beagle 2 finds organic molecules, it would be a fantastic discovery, says McKay, but still short of definitive proof that our nearest neighbor once harbored life - or still does.

"There may be organics on Mars, but that doesn't mean they're biologically produced," he says. It's hard, even on Earth, to tell the difference between naturally occurring organic molecules and those made by living organisms.

Still, says Bada, "We're all waiting very anxiously to see what they find."

Red planet plans

Mars will be the focus of an intense exploration effort between now and 2010. NASA alone has nearly a half-dozen Mars missions in the works, while the European Space Agency is planning several.

Here's NASA's itinerary for the Red Planet.

Mars Reconnaissance Orbiter (2005) - Outfitted with ground-penetrating radar and a camera capable of resolving desk-size rocks, this spacecraft will hunt for minerals that form in wet environments and signs of frozen or melted water below the Martian surface. The goal: to pinpoint sites for future robot landers.

Phoenix Mars Scout (2007) - The Mars Scout will be the first robot to land in the Martian arctic, where previous orbiters have detected evidence of copious quantities of ice protected from solar ultraviolet radiation by a thin layer of Martian soil.

Mars Science Laboratory (2009) - The project that makes many Mars-heads salivate: the first nuclear-powered robotic laboratory since Viking. Unlike today's short-lived solar-powered robots, this mobile laboratory would operate for several years and cover vast distances to sniff out signs of life and water.

Mars Telecommunications Orbiter (2009) -The first interplanetary communications satellite, designed to handle the spike in two-way radio traffic between Mars and Earth once the Mars Science Laboratory and other spacecraft arrive.

- Michael Stroh

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