LOS ANGELES (AP) - 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,
The discovery of
extreme life forms, known as extremophiles, in unexpected nooks and crannies of
the Earth in recent years 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 - a big if -
scientists speculate it would likely be similar to some extreme life on Earth -
microscopic and hardy, capable of withstanding colder-than-
``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 beside 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 much like a gardener would. And its microscope will
examine soil granules for minerals that may indicate past presence of
water.
Most living things on Earth thrive not only in the presence of water,
but also need sunlight, oxygen and organic carbon. But the range of conditions
in which life can survive has been expanded with recent discoveries of
micro-organisms trapped in glaciers and rocks or living in volcanic vents and
battery acid-like lakes.
These extreme conditions on Earth mirror the harsh
environments found on Mars and other parts of the solar system. Present day Mars
is like a desert with no hint of water on its weathered surface, although
studies of rocks suggest the planet was wetter once upon a time.
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.
Even if Phoenix uncovers microbe-habitable
conditions, a more sophisticated spacecraft would be needed to determine if life
was ever there or is present now.
The last time NASA looked for organics was
during the 1976 twin Viking missions, which sampled soil near the Martian
equator but turned up empty.
Scientists chose to dig in Mars' far north this
time because they think it's an analog to Earth's polar regions, which preserve
life's building blocks and sometimes even life itself in ice.
Researchers
have shown microbes on Earth can be inactive in a deep freeze for thousands of
years and resuscitated under the right conditions.
In 2005, NASA researchers
announced they revived bacteria that were apparently dormant for 32,000 years in
a frozen pond in central Alaska. Earlier this month, Penn State University
scientists said they were able to grow in the lab an ultra-small species of
bacteria trapped in a Greenland glacier under high pressure and low oxygen for
at least 120,000 years.
``There's a lot of amazing things that survive in the
cold environments,
What that means for Mars and other hostile environments is
debatable. But scientists are plumbing the depths of Earth for clues to possible
life that may exist elsewhere in the universe.
``We need to continue to try
to understand what's going on with the extremophiles here on Earth,'' said
Stedman of Portland State University. ``The more we learn how extremophiles here
are functioning, the more that will inform any kind of future mission.''
On
the Net:
Phoenix Mars: http://phoenix.
06/22/08 13:25 EDT
Copyright 2004 The Associated
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