North American ecosystems are critical components of the global carbon cycle. To grow, an ecosystem's plants use sunlight, atmospheric carbon dioxide and the moisture available to their roots. They also release some carbon dioxide back into the atmosphere. NASA's AirMOSS radar measures root-zone soil moisture to help determine the overall carbon exchange between plants and the atmosphere. Flying on a Gulfstream-III (G-III) aircraft, AirMOSS will use radar to collect soil moisture data from nine climatic habitats in North America to estimate how much carbon the continent is taking in or releasing to the atmosphere. Carbon dioxide has an important influence on climate, and the AirMOSS results will help to improve the accuracy of climate projections for the next 50-100 years. AirMOSS is part of NASA's Earth Ventures 1 program.