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What's keeping us from Mars?
01/04/2008 14:00 - (SA)
Washington - Cosmic rays are so
dangerous and so poorly understood that people are unlikely to
get to Mars or even back to the moon until better ways are
found to protect astronauts, experts said on Monday.
And Nasa is not properly funding the right experiments to
find out how, the National Research Council committee said.
"One of the big issues is they have really cut funding for
biology issues," retired space shuttle astronaut James van
Hoften, who chaired the committee, said.
"It is tough on them when they don't have any new money
coming in. They are using old data," he added - including
research done on survivors of the nuclear bombings of Japan
during World War II.
"Given today's knowledge and today's understanding of
radiation protection, to put someone out in that type of
environment would violate the current requirements that Nasa
has."
The committee of experts agreed that Nasa's existing
radiation safety standards can protect astronauts and they
urged the US space agency to keep them in place.
The Earth's bulk, atmosphere and magnetic field protect
life from the solar radiation and the cosmic rays that travel
through space. Astronauts have just a thin layer of shielding.
Van Hoften knows from personal experience.
"My introduction to space radiation came first-hand as a
crew member aboard the Space Shuttle Challenger in April 1984.
'What the heck was that?' I blurted out after seeing what
looked like a white laser passing quickly through my eyes," van
Hoften wrote in the introduction to the report.
"'Oh, that's just cosmic rays,' said Pinky Nelson, my
spacewalking partner and space physicist. The thought of
extremely high-energy particles originating from a distant
cosmic event passing easily through the space shuttle and
subsequently through my head made me think that this cannot be
all that healthy. The truth of the matter is that it is not."
Nowhere to hide
The cosmic rays include galactic cosmic radiation or GCR
and solar particles.
"You can put on very thick walls and they just won't
protect you from that," van Hoften said. "The younger you are
the worse it is," he added, because as with many types of
radiation, it can take years for the damage to cause disease.
"It might be OK if you just send a bunch of old guys like
me," he laughed.
Any mission to Mars using current technology would take
three years, van Hoften said. That long in space would subject
astronauts to too much radiation.
"It hasn't really gotten the airing that it needs. In the
committee we stewed over this for a long time before we said
anything," he added.
Ejections of dangerous particles from the sun can be
forecast, but astronauts must hide in specially shielded areas
of shuttles or space stations and may miss important tasks, the
committee said.
Adding more shielding can make spacecraft too heavy and is
too expensive, added the report from the council, one of the
independent National Academies of Science that advises the
federal government.
The report, commissioned by Nasa's Exploration Systems
Mission Directorate, said the radiation poses cancer and other
health risks for years after astronauts return to Earth.
"The committee finds that lack of knowledge about the
biological effects of and responses to space radiation is the
single most important factor limiting prediction of radiation
risk associated with human space exploration," the report
reads.
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