The Mars Science Laboratory (MSL, or just “Curiosity” to its friends) is still a few days away from landing on Mars but it has already finished its first experiment: For the past 252 days, the Radiation Assesment Detection (RAD) experiment has been measuring radiation levels in deep space. There is a lot of talk about a mission sending people to Mars, but one of the many obstacles is that space is a dangerous place, and human beings are quite vulnerable to radiation. RAD’s purpose is to give us an idea of how much radiation protection is needed, and what type.
Since MSL launched, the Sun has been quite active, with 5 major flares and solar particle events affecting the space between Earth and Mars. The experiment has now ended, with the RAD instrumentation retracted into the body of the spacecraft for final approach. Once (if? the landing process is quite complex, and the mission publicists are making a big deal about the risk) the landing is succesfully completed, RAD will be turned back on, for the second part of its mission: to measure radiation levels on the surface of Mars. The purpose is exactly the same as for the first part: to see what kind of radiation levels human explorers will have to cope with.