Exploring Mars or an asteroid means that NASA will have to grant exceptions to its current standards for protecting astronauts from radiation and other health risks, an expert panel warned on Wednesday.
The Institute of Medicine panel said the agency should not revise the standards wholesale, but should make exceptions for long space trips only on a "mission by mission" basis, after a heightened ethics review that weighs the social benefits of the mission against the cost to the astronauts. On their return, the astronauts should also be guaranteed lifetime health benefits, the panel said.
NASA is considering sending astronauts to lasso an asteroid in 2021 and to Mars sometime in the 2030s. It is already spending roughly $1 billion a year on the Orion space capsules for such missions, with the high cost driven in part by safety standards, according to a 2013 agency inspector general's audit.
(Related: "Mars Flyby Proposed for 2021 NASA Astronaut Mission.")
The agency also has plans for missions to the International Space Station that exceed the standard tour of six months. The health risks from exposure to radiation and weightlessness increase with the duration of the exposure.
"NASA is an exploration agency, that is what it does, and it has to make hard, dangerous decisions," says Johns Hopkins University bioethics expert Jeffrey Kahn, who headed the report panel. "There is just tremendous uncertainty and unknowns, real unknowns, about this kind of space travel."
Requested by NASA, the report provides the space agency with a framework for judging the ethics of sending explorers on dangerous missions beyond any hope of rescue. It concludes, "The only ethically acceptable option that could allow for increased risk exposures in the context of long duration and exploration space flights is granting an exception to existing health standards."
"The agency is committed to pushing the boundaries of human exploration," says a NASA response to the report released by agency spokesperson Joshua Buck. "However, we also are committed to the highest safety standards for those choosing to embark upon these bold missions."
Space travel weakens bones, hearts, and lungs and poses a wealth of other health risks, including psychological ones. New risks turn up regularly, such as the 2011 finding that about 20 percent of space station astronauts suffer from impaired vision. And 24 astronauts have died in the line of duty, most recently seven crewmembers in the 2003 Columbia tragedy. (Related: "Space Shuttle History.")
NASA space health guidelines issued in 2007 place astronauts on missions more than 210 days long in the agency's highest risk category, requiring them to receive care equal to having a doctor aboard their spacecraft.
The standards limit astronauts' career radiation exposure from cosmic rays and solar flares to levels intended to keep their lifetime risk of fatal cancer under 3 percent. A mission must allow them to keep their muscle strength at 80 percent and their aerobic capacity at 75 percent of their preflight levels.
A trip to Mars might take six months or more each way, along with a lengthy stay on the red planet's surface, where radiation hazards look similar to those in deep space. Only men over age 45 and women over age 55 who have never smoked would not exceed NASA's cancer risk standards on such a trip—and only then if they traveled during the height of the sun's 11-year "solar maximum," when strong solar winds shield the solar system from harmful cosmic rays that come from deep space. The average age of people currently selected as astronauts is 34.
The IOM report calls for not putting astronauts into situations that allows them to choose unacceptable levels of danger, Kahn says. "These are highly motivated people, who are self-selected for their interest in exploration."
He compares astronauts to National Football League players willing to reenter a football game after a concussion, heedless of brain trauma risk. "We take their helmets away if they fail a concussion test now. We don't offer to let them back into the game."
For that reason, NASA should only offer deep-space trips to astronauts on a voluntary basis after an ethics review of the proposed missions that weighs the harms faced by the explorers against the benefits to society, said the report. And the agency should offer the astronauts lifetime health care.
"One surprise was hearing how many ex-astronauts, if they were civilians, had trouble finding health care after they retired from NASA because of their risky behavior at an early age of being in space," says Kahn.
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