Curiosity landing on Mars

The NASA rover Curiosity carried a radiation instrument during its trip to Mars that is helping scientists determine how humans could survive a deep-space mission. (NASA /JPL-Caltech / August 3, 2012)

An instrument on NASA’s Curiosity rover found during its deep-space cruise that a mission to a place like Mars could expose humans to potentially dangerous radiation levels, scientists announced Thursday.

Currently, NASA allows astronauts to be exposed to radiation levels that carry up to a 3% increased risk of cancer over their entire career. The rover was exposed to radiation levels that appear to surpass that threshold, scientists said.

"In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days," Cary Zeitlin, a principal scientist at the Southwest Research Institute in San Antonio, said in a statement.

Before it headed to Mars, scientists at the Jet Propulsion Laboratory discovered that a radiation tool on the Curiosity rover could act as a stand-in for what a future astronaut might experience in their spacecraft on their way to Mars.

So 10 days after the rover launched, they turned it on, gathering information that the space agency is now using to explore how to protect astronauts from harmful radiation levels.

Don Hassler, the principal investigator of Curiosity’s Radiation Assessment Detector, and other scientists announced the findings from NASA’s Washington, D.C. headquarters on Thursday, which are also being published in Friday’s edition of the journal Science.

So how can NASA protect astronauts on a deep-space mission? Scientists have a couple of ideas.

Besides improving radiation shielding, the space agency could use hydrogen to block harmful solar energetic particles.

“One way we can protect the crew is to surround them with water in the walls of the habitat, which would absorb the space radiation,” said Chris Moore, NASA’s deputy director of advanced exploration systems. “We also could arrange food packages around the quarters where the astronauts sleep and live because food contains a lot of water and hydrogen.”

Once Curiosity landed on Mars Aug. 5, it began to measure surface radiation levels, which scientists are now using to track how a human might survive on the planet.

NASA will also launch a modified version of Curiosity’s radiation instrument to the International Space Station in 2015, said Eddie Semones, a spaceflight radiation health officer.

“This will be the first time we measure the radiation environment in [low Earth orbit] and on the Mars surface simultaneously with basically the same instrument,” he said.

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