Before any astronauts can begin fulfilling NASAs new vision of traveling to the moon and Mars, scientists must first develop a full understanding of how long-duration exposure to space radiation affects the body, NASA researchers said Sunday.

Radiation, they said, isamong the top biological concerns facing anyone aboard long-duration missions.

But it is not a showstopper, said Walter Schimmerling,NASA program scientist for space radiation research in Washington D.C., of theradiation risk facing long-term missions. What we are trying to do is tounderstand the risk and determine how to mitigate it.

Prolonged space radiation exposure could have wide-rangingimpacts on the human body depending on an astronauts sensitivity to thehigh-energy particles, researchers said. Among the potential risks are; detrimentaleffects to the central nervous system, tissues of the heart, eyes and digestivetrack, as well as the hazard of acute radiation sickness if an astronaut werecaught in solar flare while on the lunar surface or an extravehicular activity.

Merely adding additional radiation shielding to spacecraftwont solve the entire problem, though there are projects underway looking intonew shielding materials, Schimmerling told SPACE.com. He and otherscientists spoke during the 15^th annual NASA Space Radiation HealthInvestigators Workshop, a five-day meeting in Port Jefferson, New York.

NASA researchers have long known of the potential radiationhazards in space where high-energy particles proliferate outside the protectionof Earths magnetic field. During the Apollo program NASA astronauts reportedseeing bright flashes of light caused by high-energy particles striking theretinas in their eyes. More recently in October 2003, crewmembers aboard theInternational Space Station (ISS) took shelterin the outposts Zvezda module as a preventative measure against the radiationfrom a particularly strong solar flare.

During the Apollo missions, Schimmerling said, NASA sentastronauts for three-day stays on the moon, where the risk of suffering formradiation hazards for such a short amount of time were low. For a sustainedmanned lunar expedition such as that suggested by the new space vision,astronauts will have to be prepared for missions up to a year on the moon, headded.

[Radiation] is one of the largest obstacles that weregoing to have to overcome, said Terri Lomax, NASA director of fundamentalspace biology division and a professor at Oregon State University, adding that theobstacle does not only apply to humans. Since NASAs vision includes the use ofrobots to assist in human space exploration, hardening robotic and scienceequipment to withstand long bouts with space radiation is also a must, sheadded.

Francis Cucinotta, a radiation researcher at NASAs JohnsonSpace Center in Houston, Texas, said astronauts routinely face risk on anyspaceflight because of the built-in hazards of flight operations, such aslaunches and extravehicular activities. But, he added, it would be unethicalfor NASA to add to that risk by placing astronauts in a high-radiationenvironment without a proper understanding of its affect on humans.

We need to develop the technologies for advanced warningand protection against solar particle events, Cucinotta said, adding thatcutting down the risk of radiation exposure is the first step. Once we knowhow to reduce risk, we can develop countermeasures.