A NASA news release yesterday discussed some of the ways NASA’s Mars Odyssey spacecraft has changed the way scientists look at the red planet. “In just one year, Mars Odyssey has fundamentally changed our understanding of the nature of the materials on and below the surface of Mars,” said Odyssey’s project scientist Dr. Jeffrey Plaut. One finding is of particular interest to planners of a future manned mission to Mars. Odyssey has measured radiation levels at Mars that are substantially higher than in low-Earth orbit. “The Martian Radiation Environment Experiment has confirmed expectations that future human explorers of Mars will face significant long-term health risks from space radiation,” said the experiment’s principal investigator Dr. Cary Zeitlin of the National Space Biomedical Research Institute in Houston. “We’ve also observed solar particle events not seen by near-Earth radiation detectors.”

As SPACE.com explains, Odyssey’s Martian Radiation Environment Experiment (MARIE) instrument looks for two types of radiation–the sporadic expulsions from the Sun and the flow of charged particles of unknown galactic origin that continually bombard Mars from all directions. Long term exposure to both types of radiation, in low doses, can have serious health effects. Earth’s strong magnetic field shields us from much of this radiation at ground-level, but not so with Mars. The radiation above Mars appears to be 2.5 times higher than at the International Space Station. Over a three year period, Zeitlin says that “those are manageable doses.” However, he cautions that “it would be close to the limit.”

Odyssey has also confirmed that solar radiation bursts originating on one side of the sun can be very directional, hitting either Mars or Earth, but missing the other, depending on the positions of each planet around the sun. Mars spends much of its time on the opposite side of the Sun, relative to Earth. “We’ll have to have radiation monitors around the inner solar system to watch out for these sorts of events and send out warnings, alarms, so astronauts can take appropriate shelter as needed,” Zeitlin said.