Mars astronauts safe from radiation

By STEVE CONNOR

Humans could survive an extended visit to Mars without dying of radiation exposure.

A study of the cosmic rays bombarding the planet says a space colony should be able to shield itself from any radiation, thus escaping significant increases in the risk of cancer or other radiation-induced diseases.

Although it may be many years before there is a manned mission to Mars, scientists are already assessing what needs to be done for such a return trip to work.

One of the big unknowns is how much radiation Mars is exposed to from the Sun and other sources of cosmic rays - unlike Earth, the Red Planet has no magnetosphere to shield it from space radiation.

An experiment on the Odyssey spacecraft orbiting Mars has, however, found that the radiation dose should be within manageable limits for astronauts, although still significantly higher than on Earth.

The Odyssey's radiation instruments found that astronauts visiting Mars would experience a radiation dose about twice the level typically experienced on the International Space Station, which orbits within Earth's magnetosphere.

Cary Zeitlin, from Lawrence Berkeley National Laboratory in California, said astronauts visiting Mars would be exposed to higher risks than those spending a few months on the space station.

"People are going to the space station for about six months. A Mars mission would last about three years, and it's the duration of the exposure that becomes the issue.

"It's also the fact that the radiation is quite exotic. It's galactic cosmic radiation. It comes from all over the galaxy. We call it heavy ion radiation."

Potentially, this radiation could be more damaging to health in terms of causing more cancers, cataracts and nerve disorders, he said.

However, it should be relatively easy to shield people by, for instance, building shelters in hollows in the ground or taking extra protective material from Earth.

The Odyssey's instrument, called the Martian Radiation Environment Experiment, is designed to predict radiation doses for future astronauts but was itself damaged by a solar radiation storm.

Before it was knocked out, however, it sent back enough data on Martian radiation levels for scientists at the US National Aeronautics and Space Administration to assess the risks to a manned mission.

Nevertheless, one of the biggest problems for a mission to Mars is how to carry enough fuel to maintain life-support systems during the visit and to ensure a safe return journey to Earth.

One idea is to send an unmanned probe that can produce oxygen and hydrogen from any frozen water in the Martian ground using solar energy. The gases could then be used as rocket propellant for a later return journey of a manned mission, as well as helping to keep astronauts alive during their stay on the Red Planet.

The next space probe to reach Mars will be the European Mars Express, carrying a small, British-built lander called Beagle 2 which is scheduled to begin its descent late this week.

- INDEPENDENT