David Grinspoon, curator of astrobiology at the Denver Museum of Nature and Science, talks about why Curiosity’s Radiation Assessment Detector truly is “RAD.” The RAD instrument is being used to study the presence of radiation at the Martian surface for the first time, and can tell astrobiologists how much radiation is penetrating the planet’s atmosphere and reaching the ground. Curiosity will use RAD to study how radiation might have affected life that existed on or under the surface of Mars.