We first looked back at Earth with human eyes just over forty years ago. The images of our blue planet adrift in the vastness of a harsh cosmos became icons for the environmental movement. The first Earth Day was celebrated just 16 months later — no coincidence. NASA’s efforts to explore the solar system bring advanced technology and cutting-edge instruments to the study of our home planet. An entire constellation of Earth-observing satellites are monitoring our climate, the carbon cycle, water resources, pollution, ice cover, ozone, global temperatures, and natural disasters. Our ability to bring back from space hard numbers about our changing planet should enable us to make environmental protection decisions based not on politics, but on valid science. Making data-based decisions can save us hundreds of billions in needlessly painful and misdirected policies. Let’s use NASA’ s expertise to attack our own pollution sources in a cost-effective way: the right moves, informed by hard measurements using space technology, can help us find new energy sources and get the most bang for our environmental bucks.