Testimonials
By Steve Gorman
PASADENA, California (Reuters) - As scientists search for signs of life
on Mars and elsewhere in the solar system, they are sticking to one guiding
principle -- follow the water.
Indeed, NASA experts say their entire game plan for the latest stage of
Mars exploration is based on sending twin robotic rovers, Spirit and Opportunity,
to two spots on the red planet where the evidence of water is most compelling.
Spirit landed on Saturday night in the heart of Gusev Crater, a massive
basin larger than Connecticut that was carved out by the impact of an asteroid
or comet early in Mars' history and is thought to have once held a gigantic
lake.
A long, deep valley apparently chiselled by ancient flows of water leads
into Gusev, suggesting it was fed by an ancient river.
In three weeks NASA plans to land Opportunity on the so-called Meridiani
Planum, a smooth plain near Mars' equator where NASA's orbiting Mars Global
Surveyor has detected an abundance of grey hematite, a mineral that on Earth
usually forms in association with liquid water.
Some environmental conditions that can produce hematite, such as a lake
or hot springs, could be hospitable to life. Others, such as hot lava, would
not.
"
We believe the pathway to finding life is to follow the water," said
Firouz Naderi, Mars exploration programme manager.
At the crux of this quest is whether "there are locations where water
has been sustained ... for a very long period of time so life would have
time to evolve in them," said Charles Elachi, director of NASA's Jet
Propulsion Laboratory. "Mars appears at first look to have the right
ingredients."
A KEY FIND
Determining whether Mars ever supported living things would provide scientists
with valuable insights into the evolution of life on Earth and the question
of how rare or common life may be throughout the universe, Elachi said.
Although scientists believe the odds are slim that advanced forms of life
like those on Earth could have evolved on Mars' comparatively hostile environment,
there is reason to believe that simple, microscopic organisms may have once
existed at a time when Mars was warmer and wetter.
It is even possible that primitive life forms may now be present beneath
Mars' thick polar ice caps or in subterranean springs warmed by heat vents
around smouldering volcanoes. There could also be Martian equivalents of
lithotrophs, single-celled microbes that dwell in bedrock.
The two rovers are designed to roam the surface of Mars for about three
months seeking to unlock clues to the mystery of water on Mars by examining
its rocks and soil.
The Spirit will survey its general environs with a pair of high-resolution,
panoramic cameras mounted on a mast and with a spectrometer that measures
the infrared radiation emitted by minerals. Together, these instruments will
help scientists pick which areas to explore first with the rover.
The rover carries several more gadgets on its robotic arm to conduct remote-controlled
geologic studies, including a microscopic camera to give scientists extreme
close-up views of minerals, a tool to grind away the outer layer of rocks,
and an instrument to analyse the composition of rocks and soil.
Besides Earth, which is Mars' closest planetary neighbour, the only place
in the solar system where water is believed to exist is Europa, a moon of
Jupiter, where a liquid ocean may lie beneath an icy crust, JPL's Naderi
said.
