Radiation concerns for trip to Mars
Astronauts would get high doses on their long flight. Still, volunteers are expected.
LOS ANGELES - Astronauts traveling to and from Mars would be bombarded with as much radiation as they would get from a full-body CT scan about once a week for a year, researchers reported Thursday.
That dose would, in some cases, exceed NASA's standards and is enough to raise an astronaut's cancer risk by 3 percent.
As plans for deep space exploration ramp up, radiation is a big concern - from high-energy galactic cosmic rays spewed by distant supernova explosions to sporadic bursts of charged particles hurled by the sun. Earth's magnetic field helps to deflect much of that harmful radiation.
NASA aims to send a crew to orbit the red planet by the mid-2030s. Private outfits like Inspiration Mars - backed by NASA engineer-turned-space tourist Dennis Tito - are seeking volunteers for a Mars flight.
There have been previous efforts to gauge the radiation risk for future Mars travelers, but the best estimate is coming from NASA's Curiosity mission. Tucked inside the rover when it launched in 2011 was a radiation sensor that took readings during the 81/2-month cruise to Mars.
From those figures, scientists calculated a spacefarer's radiation exposure for a quicker six-month voyage in a similarly shielded spacecraft. Round-trip: about 662 millisieverts. That's a sizable chunk of an astronaut's career cap of 1,000 millisieverts, which many international space agencies use to limit the accumulated radiation dosage in space.
NASA's threshold depends on age and gender. The career dose limit for 30-to-60-year-old male astronauts who never smoked ranges from 800 to 1,200 millisieverts. For female astronauts, the limit ranges from 600 to 1,000 millisieverts.
The radiation exposure from a Mars journey is similar to getting a full-body CT scan every five or six days, said lead researcher Cary Zeitlin of the Southwest Research Institute in Boulder, Colo.
The estimate is just for zipping there and back; it doesn't include time spent on the Martian surface, which would add to an astronaut's exposure. How much more would depend on length of stay and available shelter.
"You'd like the radiation exposure to be lower, but it is what it is," said Dr. Norm Thagard, the first American to fly on the Russian space station Mir, who had no role in the research. "Given the importance of such a mission, the mission should be done."
The analysis appears in Friday's issue of the journal Science. The amount of radiation likely won't change unless there's a rocket engine developed that can speed up the interplanetary ride, researchers said.