OT: Scientists: Mars radiation poses risk
stoney
Scientists: Mars radiation poses risk
Friday, March 14, 2003 Posted: 10:30 AM EST (1530 GMT)
William Boynton, team leader of the Mars Odyssey spacecraft's gamma ray
spectrometer gear, talks about his findings.
PASADENA, California (AP) -- Radiation on Mars is so intense that it
could endanger astronauts sent to explore the Red Planet, and it's
unlikely that any extraterrestrial life would survive there, NASA
scientists said.
High radiation levels measured by the space agency's unmanned Mars
Odyssey spacecraft suggest that any extraterrestrial life would have
little chance of surviving unless it were shielded beneath the planet's
dusty, cold surface, Cary Zeitlin of the National Space Biomedical
Research Institute in Houston said Thursday.
"It would have to be pretty robust against all kinds of environmental
horrors," said Zeitlin, one of the scientists working on the project.
Getting a clearer picture
The conclusions stemmed from new data released by scientists at NASA's
Jet Propulsion Laboratory from the first year of scientific results from
the $300 million mission.
Scientists also presented information on the minerals and elements that
make up the planet's surface, including measurements that show its
northern hemisphere is richer in water than its southern half. Near the
planet's north pole, frozen water makes up as much as 75 percent, by
volume, of the top 3 feet or so of soil, said William Boynton, one of
the mission's scientists.
"We're talking ice with a little bit of dirt mixed in it and not the
other way around," Boynton said.
Looking at possible accidents
NASA talks vaguely of future manned missions to Mars, where astronauts
could use that ice for drinking water, fuel and oxygen to breathe. The
new radiation findings suggest such a mission would be risky.
Even so, possible accidents involving the spacecraft that would take
astronauts to and from Mars pose a far greater risk, said Robert Zubrin,
president of the pro-exploration Mars Society.
"The idea (radiation) represents this incredible, forbidding obstacle to
Mars exploration just isn't so," Zubrin said.
Mars is continuously bombarded by radiation from the galaxy at large, as
well as by periodic bursts from the sun. The radiation would expose
astronauts in orbit to an effective dose 2.5 times greater than that
received by humans in low Earth orbit aboard the international space
station, Zeitlin said.
A three-year mission would expose astronauts to the radiation limit
considered safe by NASA over the career of an astronaut, he added.
Atmosphere may shield
The radiation environment on the surface of Mars is unknown but probably
poses a similar risk, even though the planet's tenuous atmosphere would
provide some shielding.
"It still remains to be seen what the hazards are on the surface,"
Odyssey project scientist Jeffrey Plaut said.
The main worry for astronauts on Mars would be the periodic bursts of
charged particles that stream outward from the sun. On Earth, a global
magnetic field and a substantial atmosphere protect against that
radiation.
Observations made last year show bombardments of solar radiation can
last more than a week. Presumably, astronauts on Mars would have to
remain confined in some sort of shelter during such blasts of radiation,
Zeitlin said.
"They're manageable, as long as the spacecraft has these refuge areas,"
Zeitlin said.
Mars Odyssey's science mission is expected to last 18 more months but
probably will be extended. The spacecraft has been thrifty enough with
its fuel to enable it to stay in orbit 20 more years, Plaut said.
Copyright 2003 The Associated Press.
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