SAND-FILLED CRATER (left), 11 meters (36 feet) in diameter, was discovered by the authors on their expedition to Wabar in December 1994. Under the sand the crater is lined with a bizarre kind of rock--impactite--thought to have formed when immense pressures glued sand grains together. Around the crater rim are centimeter-size chips of iron and nickel. From the size of the crater geologists estimate that it formed when a dense metallic meteorite just one meter across smacked into the sand. This meteorite had split off from the larger bodies responsible for the other two craters at Wabar.

SECOND-LARGEST CRATER (right) at the Wabar site, Philby "A," has been nearly buried by a creeping seif ("sword," in Arabic) dune. Only its southeastern rim, preserved by a gravelly mix of rock formed during impact, still pokes up above the sand. The 64-meter (210-foot) crater marks the impact site of a five-meter meteorite, one of several pieces of the original Wabar meteoroid (which broke apart in midair). The chunks hit the ground at speeds of up to 25,000 kilometers per hour--20 times as fast as a .45-caliber pistol bullet.