For art collectors willing to spend a cool million, the latest must-have objects are falling from the sky. Big names like Steven Spielberg, Nicolas Cage and Yo-Yo Ma are buying meteorites at prices that are out of this world. On Oct. 28, Bonhams auctioneers will hold their first-ever sale devoted to them, and some lots are expected to fetch into the seven figures. "The natural world is making a foray into the art world," says Barbara Tapp, editor of Art & Antiques. "Given global warming, these pieces reflect attention on how our world is changing." Esthetic meteorites, as they're called, are mostly iron-based and admired for their sculptural beauty. Private dealers trade rare finds, such as lunar rocks, with museums for less scientifically significant—but more decorative—meteorites. The jewel of the Bonhams sale is the crown piece of the American Museum of Natural History's Willamette meteorite, priced at $1.3 million. "Scientists don't care about money," says Darryl Pitt, who traded a scientifically useful stamp-size piece from Mars for the chunk of Willamette. "They just want to write abstracts."