June 24, 2008
Searching for Life Signs — Phoenix Testing Soil From Mars’ Arctic Polar Region for Sustaining Compounds
By Alicia Chang
LOS ANGELES - Bizarre microbes flourish in the most punishing environments on Earth from the bone-dry Atacama Desert in Chile to the boiling hot springs of Yellowstone National Park to the sunless sea bottom vents in the Pacific.
Could such exotic life emerge in the frigid arctic plains of Mars?
NASA's Phoenix spacecraft could soon find out. Since plopping down near the Martian north pole a month ago, the three-legged lander has been busy poking its long arm into the sticky soil and collecting scoopfuls to bake in a test oven and peer at under a microscope.
There hasn't been a eureka moment yet. But Phoenix turned up a promising lead last week when it uncovered what scientists believe are ice flecks in one trench and an icy layer in another.
Scientists hope experiments by the lander will reveal whether the ice has ever melted and whether there are any organic, or carbon- containing, compounds.
"We're looking for the basic ingredients that would allow life to prosper in this environment," chief scientist Peter Smith of the University of Arizona in Tucson has said in describing the mission's goal.
The discovery of extreme life forms, known as extremophiles, in unexpected nooks and crannies of the Earth has helped inform scientists in their search for extraterrestrial life.
"It's very suggestive that there are lots of worlds that may support life that at first glance may look like fourth-rate real estate," said Seth Shostak, an astronomer at the SETI Institute, a nonprofit dedicated to the search for extraterrestrial intelligence.
While the possibility for ET seems to grow with new extremophile discoveries on Earth, the truth is there's no evidence that life ever evolved on Mars or if it even exists today.
But if there were past or present life on the red planet scientists speculate it would likely be similar to some extreme life on Earth - microscopic and hardy, capable of withstanding colder- than-Antarctica temperatures and low pressures.
"It's going to be microbes. It's not going to be a little green man," said Kenneth Stedman, a biologist with the Center for Life in Extreme Environments at Portland State University.
Under a microscope, extremophiles vary in size and shape. Some resemble miniature corkscrews while others are rods or irregular shapes. Scientists use a dye to distinguish the living ones from the dead.
The Phoenix mission has its limitations besides a shoestring budget of $420 million. It doesn't carry instruments capable of identifying fossils or living things. Rather, the lander has a set of ovens and a gas analyzer that will heat soil and ice and sniff the resulting vapors for life-friendly elements. Its wet chemistry lab will test the pH, or acidity, of the soil. And its microscope will examine soil granules for minerals that may indicate past presence of water.
Most researchers agree life likely cannot develop on the Martian surface, which is bombarded by lethal doses of radiation. But satellite images have revealed a softer side, spying hints of a vast underground store of ice near the red planet's polar regions. Phoenix last week hit what's thought to be an ice layer 2 inches below the surface.
Originally published by Alicia Chang Associated Press .
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