A rare rock from Mars known as Meteorite NWA 16788 will be up for auction at Sotheby's on July 16. The meteorite may sell for as much as $4 million, according to the auction house.

A chunk of the Martian surface that made an unlikely voyage to Earth will be available to the highest bidder at Sotheby's ...

Ejected material, mostly breccia (angular rocks cemented by clay), can be found far as 3 to 4 km (1.8 to 2.5 mi) from the largest craters.” ...