CNN  —  A meteorite that is the largest known piece of Mars on Earth has sold for a hammer price of $4.3 million to an anonymous bidder at a Sotheby’s New York auction Wednesday. Known as NWA 16788, the meteorite weighs 54 pounds (24.5 kilograms), massive compared with most Martian meteorites, which tend to be small fragments, auction house Sotheby’s said in a July 8 statement. Meteorites are what’s left when a comet, asteroid or a meteoroid survives its passage through the earth’s atmosphere.