The findings demonstrate that Mars' atmosphere, though just 1 percent as thick as that of Earth, does provide a significant amount of shielding from dangerous, fast-moving cosmic particles. (Mars lacks a magnetic field, which gives our planet another layer of protection.)
The $2.5 billion Curiosity rover is getting a bead on the nature of this shielding. RAD has observed that radiation levels rise and fall by 3 to 5 percent over the course of each day, coincident with the daily thickening and thinning of the Martian atmosphere, researchers said.
Hassler stressed that RAD's findings are preliminary, as Curiosity is just three months into a planned two-year prime mission. He and his team have not yet put hard numbers on the Martian radiation levels, though they plan to do so soon.
"We're working on that, and we're hoping to release that at the AGU meeting in December," Hassler said, referring to the American Geophysical Union's huge conference in San Francisco, which runs from Dec. 3-7. "Basically, there's calibrations and characterizations that we're finalizing to get those numbers precise."
The real issue for human exploration, he said, is determining how much of a radation dose any future astronauts would accumulate throughout an entire Mars mission — during the cruise to the Red Planet, the time on the surface and the journey home.
"Over time, we're going to get those numbers," Hassler said.
One key to understanding the big picture will be documenting the effects of big solar storms, which can blast huge clouds of charged particles into space. Curiosity flew through one such cloud on its way to Mars but has yet to experience one on the surface, Hassler said.