The Mars Curiosity rover is three months into its two-year mission to determine if Mars was, or still is, able to support life.
One life-limiting factor to habitability — and critical to a future manned mission to Mars — is the level of radiation, from cosmic rays and solar particles, that gets to the planet's surface.
To measure this, an instrument onboard the rover called the Radiation Assessment Detector, or "RAD," has been collecting data on the daily cycles of radiation reaching Curiosity.
The Martian atmosphere acts as a shield for radiation on the planet's surface. Scientists known this because as the atmosphere gets thicker, the radiation level dips between 3 and 5 percent, according to the latest findings.
The problem is that the atmosphere of Mars is 100 times thinner than Earth's, meaning the surface is much more easily penetrated by radiation, and therefore more dangerous to astronauts.
But the principal questions remains: Could astronauts survive in the Martian environment?
"Absolutely, astronauts can live in this environment," RAD's principal investigator Dan Hassler, said in a teleconference today. At least for a limited period of time.
Radiation levels on the surface of Mars are about half of what scientists observed during deep space flight. Accumulating radiation over a long time is the main concern.
What's certain is that a deep space mission to Mars would be long — somewhere around three-years, including the six months its takes to travel there and another six back.
"There's a concept of career-limit in terms of total radiation dose [astronauts] can experience," Hassler said.
On a normal day, an astronaut in deep space should be safe from radiation. "It [radiation sickness] doesn't happen overnight," Hassler noted.
The scenario might be different if astronauts encountered an event where lots of radiation is emitted, like in a solar storm.
Still, nothing is certain. Scientists will continue to take measurements and conclusive dose level determinations are ongoing.
In the chart below, radiation dose is given in arbitrary units to reflect the magnitude of the variations. Hard numbers will be announced at the AGU meeting in December.
"It's never been a question of 'if' we go to Mars; it's when we go, how can we best protect our astronauts?" Hassler said. "We really needed to go there and make these measurements so we had definitive proof to make our design better."
SEE ALSO: We Can't Land On Mars Without NASA's Million-Dollar Spacesuit