Radioactive Moon

How much radiation awaits lunar colonists? A new NASA mission aims to find out.

On the Moon, many of the things that can kill you are invisible: breathtaking vacuum, extreme temperatures and space radiation top the list.

Vacuum and temperature NASA can handle; spacesuits and habitats provide plenty of air and insulation. Radiation, though, is trickier.

The surface of the Moon is baldly exposed to cosmic rays and solar flares, and some of that radiation is very hard to stop with shielding. Furthermore, when cosmic rays hit the ground, they produce a dangerous spray of secondary particles right at your feet. All this radiation penetrating human flesh can damage DNA, boosting the risk of cancer and other maladies.

The surface of the Moon is exposed to space radiation.

According to the Vision for Space Exploration, NASA plans to send astronauts back to the Moon by 2020 and, eventually, to set up an outpost. For people to live and work on the Moon safely, the radiation problem must be solved.

"We really need to know more about the radiation environment on the Moon, especially if people will be staying there for more than just a few days," says Harlan Spence, a Professor of Astronomy at Boston University.

To carefully measure and map the Moon's radiation environment, NASA is developing a robotic probe to orbit the Moon beginning in 2008. Called the Lunar Reconnaissance Orbiter (LRO), this scout will pave the way for future human missions not only by measuring space radiation, but also by hunting for frozen water and mapping the Moon's surface in unprecedented detail. LRO is a key part of NASA's Robotic Lunar Exploration Program, managed by the Goddard Space Flight Center.

One of the instruments onboard LRO is the Cosmic Ray Telescope for the Effects of Radiation (CRaTER).

"Not only will we measure the radiation, we will use plastics that mimic human tissue to look at how these highly energetic particles penetrate and interact with the human body," says Spence, who is the Principal Investigator for CRaTER.

The CRaTER telescope consists of silicon radiation detectors (red) mounted on detector boards (green), separated by pieces of "tissue-equivalent" plastic (tan).

By placing the radiation detectors in CRaTER behind various thicknesses of a special plastic that has similar density and composition to human tissue, Spence and his colleagues will provide much-needed data: Except for quick trips to the Moon during the Apollo program, most human spaceflight has occurred near Earth where our planet's magnetic field provides a natural shield. In low-Earth orbit, the most dangerous forms of space radiation are relatively rare. That's good for astronauts, but it leaves researchers with many unanswered questions about what radiation does to human tissue. CRaTER will help fill in the gaps.