A thick dust cloud travels southward from Saudi Arabia's Rub al Khali sand sea towards the edge of the Arabian Peninsula. This natural-color satellite image shows the dense part of the cloud approaching Yemen (lower left) and translucent swirls of dust over the Arabian Sea. Lines of small clouds cling to the margins of the dust plumes south of Oman (lower right). These clouds may result from the same weather front that kicked up high winds and stirred the dust storm. This region is one of the world's most prolific dust-producing areas, thanks in part to the presence of the sand sea. The Rub al Khali holds about half as much sand as the Sahara Desert. Image courtesy of NASA.