Books Peter Douglas Ward Books by Peter Douglas Ward Peter Douglas Ward has written books about: Nonfiction Science & Health Facebook Twitter Flipboard Email NPR stories about Peter Douglas Ward Opinion 13.7: Cosmos And Culture How Rare Is The Earth? October 31, 2012 NASA's Kepler Mission has been spotting many "Earth-like" planets within our galactic neighborhood. But what fraction of these Earth-like planets are really like our planet? The more we learn about Earth's remarkable properties, the rarer our planet seems to be. And with it, the life it hosts.