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With Phoenix mission, water hunt to resume on Mars

The lander is scheduled to touch down on the red planet Sunday, marking a turning point in the exploration program.

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At one point during the descent, the lander’s thrusters must scoot the craft sideways to try to ensure that it won’t get tangled up in its parachute as it touches down. The final 40 seconds of the descent rely on a dozen small motors, each firing in pulses, to ease the lander’s three legs onto the surface. Then, after a 20-minute wait for the dust to settle, the craft will deploy its solar panels. Folks at JPL won’t get confirmation of that process until 90 minutes after touchdown. With a “panels deployed” signal, it’s truly high-five time.

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The lander carries an array of instruments designed to, in effect, taste and smell the Martian soil, says Sam Kounaves, a Tufts University chemist and member of the science team. A sterilized mini-backhoe will dig up soil samples near the lander to a depth of about 20 inches. That should be deep enough to bring up water-ice that had been detected previously by Mars orbiters. Estimates are that the soil at this spot contains from 30 to 60 percent water-ice.

Soil samples then get directed to each of two microscopes on the lander, and to eight small, use-it-once furnaces. These furnaces can reach temperatures of up to 1,000 degrees Celsius (1,832 degrees Fahrenheit). By measuring temperatures at which materials vaporize in the heat and analyzing the gases created, the lander’s instruments can give scientists a bead on the compounds in the soil.

Researchers are looking in particular for organic compounds that could represent building blocks for life. In addition, Dr. Kounaves says, he and his colleagues will be looking for inorganic compounds that could serve as food for simple organisms. If a smorgasbord is there, “then its more probable that life might have been there as well,” he says.

In addition, as the scoop works its way down, researchers will analyze samples at each depth for evidence of changes in the area’s recent climate – manifest in the presence or absence of salts among the soil’s constituents. And the lander hosts several cameras plus a weather station that will track local conditions throughout the 90-day (Martian time) mission, during which the seasons will shift from late spring to midsummer.

Although the mission isn’t designed to hunt for life directly, its hardware is suited to an experiment that could answer a key related question: Does Mars’s red hue come from oxidation based on inorganic chemistry, or does the oxidation have a biological origin?

Since the days of the two Viking lander missions, which found no evidence for life at their sites, many scientists have held that inorganic compounds are responsible for oxidizing the surface. But last year, a team led by Dirk Schulze-Makuch at Washington State University proposed that cellular life, with hydrogen peroxide as part of an organism’s cell fluids, could also do the trick.

Hydrogen peroxide – popular as a hair bleach with the surfing set in the 1960s – is present in terrestrial organisms, such as Bombardier beetles, Dr. Schulze-Makuch explains. Hydrogen peroxide attracts water, so creatures with a significant amount in their cellular fluids might be able to absorb water vapor out of the atmosphere, instead of requiring liquid water. The compound might also serve as an antifreeze to help carry simple organisms through the Martian winter.

But hydrogen peroxide can break down easily, so it would need a stabilizing compound to hold it together. And the hardware on Phoenix is up to the task of detecting it. The detection of any one of several possible stabilizers wouldn’t be the smoking gun for life, he concedes. “But it would be strongly supportive.”