Humans 'Could Survive Mars Visit'

Dec. 9, 2003
By Richard Black
BBC science correspondent, in San Francisco

Scientists say measurements taken by the US space agency's Mars Odyssey craft prove that a human mission could survive on the Martian surface.

Instrument data show radiation around the Red Planet might cause some health problems but is unlikely to be fatal.

Mars Odyssey has sent back a wealth of information about Earth's neighbour since it went into orbit two years ago.

The new research was presented at the annual meeting of the American Geophysical Union in San Francisco.

Radiation risk

On Earth, we are protected from the worst cosmic radiation. The Earth's magnetic field acts like a shield, diverting radiation away.

But for astronauts on the Martian surface - or travelling between Earth and Mars - there is no such protection.

Nasa scientists have been measuring radiation around Mars with an instrument on board the Mars Odyssey orbiting probe.

According to Cary Zeitlin, from the National Space Biomedical Research Institute, it has found that astronauts on the Red Planet would be exposed to roughly double the radiation dose they currently experience on the International Space Station.

"The dose [an] astronaut would receive on a Mars mission is large enough to be beyond what they've experienced in Earth orbit," he told BBC News Online.

"Therefore it opens some questions about the biological effects of this radiation that we haven't really fully addressed yet."

Martian bunkers

He continued: "People are going to the space station for about six months.

"A Mars mission would last around 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."

This radiation could perhaps lead to more cancers, more cataracts and nervous system damage.

But overall, Dr Zeitlin says, it is manageable - humans could go on Mars missions relatively safely.

They would need to use the planet itself to shield them, building their shelters in hollows, and perhaps taking materials which would reduce radiation further.

What is somewhat ironic about this is that the Odyssey instrument, named Marie, has itself been damaged, apparently beyond repair, by excessive radiation from the Sun.

It stopped functioning following a massive solar flare in October.

But Nasa says it sent back enough data before its demise to reassure us about the feasibility of human missions to Mars.

Ice age

Other Odyssey results released here in San Francisco suggest Mars may be going through a period of climate change.

The amount of frozen water near the surface in some relatively warm low-latitude regions on both sides of Mars' equator appears too great to be in equilibrium with the atmosphere under current climatic conditions.

Dr William Feldman, of Los Alamos National Laboratory in New Mexico, said: "One explanation could be that Mars is just coming out of an ice age.

"In some low-latitude areas, the ice has already dissipated. In others, that process is slower and hasn't reached an equilibrium yet.

"Those areas are like the patches of snow you sometimes see persisting in protected spots long after the last snowfall of the winter."

Odyssey assesses water content indirectly, through measurements of neutron emissions.

Frozen water makes up as much as 10% of the top metre of surface material in some regions close to the equator. Dust deposits might be covering and insulating the lingering ice, Dr Feldman said.

http://news.bbc.co.uk/2/hi/science/nature/3302375.stm