- WASHINGTON -- In the next 30 days, two U.S. spacecraft will rocket off
to Mars, continuing the search for answers to such profound questions as:
Is there life beyond Earth? Can humans survive on another planet? Could
Earth become as hostile to life as Mars now seems to be?
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- The Mars Climate Orbiter, due to be launched
today, and Polar Lander will be taking the next steps in the exploration
of the Red Planet, a long-range venture that began with the Mariner flybys
in the 1960s, progressed to the Viking landings in the 1970s, and accelerated
with Pathfinder's spectacular return visit July 4, 1997.
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- Mars holds an extraordinary appeal for
scientists because they think it may resolve some of the deepest mysteries
humankind has faced. So far, remote-controlled machines have done the exploring,
but NASA plans to send human investigators early in the next century.
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- "The question that drives us at
NASA is the search for life beyond Earth," Edward Weiler, the space
agency's chief scientist, said. "We're seeking to answer the question:
Is life a cosmic imperative? Are we alone in the universe?
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- "These aren't just scientific questions.
Humans have been asking them since humans began thinking."
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- Scientists do not expect the two new
spaceships to find evidence of extraterrestrial life. But each will advance
the quest for knowledge.
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- The Climate Orbiter is scheduled to be
launched this afternoon from Cape Canaveral and to reach Mars in September.
The launch, originally set for yesterday, was delayed for 24 hours so NASA
engineers could correct a potentially damaging software problem. The Orbiter
will spend a Martian year -- almost two Earth years -- circling the Red
Planet at an altitude of 262 miles, monitoring the atmosphere, surface
and polar caps.
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- Its camera will produce the most detailed
color map yet of the entire planet. With a resolution of 130 feet, not
much bigger than a basketball court, the map will help scientists pick
out the most likely places to find water and, conceivably, signs of life.
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- The Polar Lander is set to follow on
Jan. 3. It should touch down next December on the frigid steppe near the
southern ice cap, where it is scheduled to operate through the Martian
summer.
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- The Lander is equipped with a 6-foot
robotic arm designed to dig a trench and look for traces of underground
water that might harbor microorganisms protected from lethal radiation
on the surface.
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- Ten minutes before touchdown, the Lander
also is to release two 8-pound "microprobes" that are to crash
into the surface at 400 m.p.h., burying themselves up to 3 feet into the
frozen ground. A tiny drill is to pull in a soil sample, checking for water
ice.
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- Data from the Lander and the microprobes
are to be radioed up to the Orbiter for relay home.
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- A key question NASA must answer in the
next decade is whether robots or humans make better extraterrestrial scientists.
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- Robotic machines such as Pathfinder's
little rover and the Global Surveyor spaceship now orbiting Mars have already
helped scientists to learn much about our neighboring planet. But some
experts believe that only humans can perform the most difficult tasks,
such as finding microscopic fossils of long-dead bacteria.
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- "Humans are immeasurably more capable
and versatile than the machines we have available today for planetary exploration,"
said Geoffrey Briggs, a Mars expert at NASA's Ames Research Center in Mountain
View, Calif.
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- Carol Stoker, a robotics expert at Ames,
agreed. "There is a common misconception that robots can explore Mars
more cost-effectively than humans," she said. "But robots are
simply the tools for gathering data for humans. For geological fieldwork,
nothing will work better than the human in the field."
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- Whether people or machines do the work,
researchers say that the exploration of Mars has greater value than simply
satisfying curiosity about an alien world. It can also help solve Earthly
riddles.
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- Scientists always demand more than one
experiment to prove a hypothesis. So far, however, Earth is the only laboratory
available to study how living creatures evolved from a single, primordial
ancestor.
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- "To understand life, we need a second
example," Christopher McKay, a biologist at Ames Research Center,
said. "On Earth, all life is a variation on a single theme."
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- It is possible, for example, that extraterrestrial
life could arise without the particular combination of carbon-based chemicals,
mild temperatures and plentiful energy available on our own planet.
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- "Because we have only the one example
of life in the universe, on Earth, it is extremely dangerous to make generalizations
about the conditions needed for life," said Bruce Jakosky, a planetary
scientist at the University of Colorado in Boulder.
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- Some scientists, such as Norman Sleep,
a geophysicist at Stanford University in Palo Alto, Calif., even contend
it is more likely that life arose first on Mars and was transported to
Earth aboard a meteorite. That is because Mars suffered less than Earth
from bombardment by giant space rocks, which could have allowed primitive
microorganisms to develop beneath the surface.
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- Another reason scientists are eager to
investigate Mars is for what it can teach us about global climate change,
a little-understood process now threatening our own planet. Three billion
to four billion years ago, when Earth and Mars were young, they apparently
had similar climates, but then Mars took a different path.
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- "If Mars was warm and wet in the
past, why did it change? What happened to produce the cold and dry environment
of today?" Matt Golombek, chief scientist on the Pathfinder project,
asked.
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- "Scientists do not know the answer
to this question, but it is obviously important for understanding long-term
climate change in general," Golombek wrote in the preface to a new
book on Pathfinder.
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- Scientists also believe Mars can reveal
much about the history of our own planet: its violent past and its uncertain
future.
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- Additional unmanned missions are planned
every two years until 2014, when NASA hopes to put the first humans on
another heavenly body since the last Apollo moon landing 26 years ago.
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