Anyone planning to explore Mars would be wise to avoid a fewhighland locations because of the dangerous doses of radiation expected there.

NASA released a new global map of Mars last week showingestimates for amounts of high-energy-particle cosmic radiation reaching thesurface, a health concern for humans who might one day visit the planet.

The estimates are based on measurements made on the way tothe Red Planet by the Mars Odyssey's Mars Radiation Environment Experiment(MARIE), along with information about Mars' surface elevations from the laseraltimeter instrument on NASA's Mars Global Surveyor.

The areas of Mars expected to have the least radiation arewhere elevation is lowest, because those areas have more atmosphere above themto block out some of the radiation. Earth's thick atmosphere shields us frommost cosmic radiation, but Mars has a much thinner atmosphere.

Colors in the map refer to the estimated average number oftimes per year each cell nucleus in a human there would be hit by a high-energycosmic ray particle. The range is generally from a moderate risk level of twohits, noted in green, to a high risk level of eight hits, noted in red.

The MARIE instrument was used en route until August, when itceased to function. Engineers have been unable to get it back online but saidlast Friday that they remain optimistic they'll figure the problem out. If theinstrument is made to work, a more detailed and accurate map would be one goal.

Odyssey is managed by NASA's Jet Propulsion Laboratory.

Special Report: MarsOdyssey Mission and Discoveries