Browse image
Resolutions offered for this image:
1000 x 576 pixels 540 x 311 pixels 720 x 480 pixels 4256 x 2913 pixels 640 x 438 pixels
Cloud masks available for this image:

Spacecraft nadir point: 18.5° N, 53.6° E

Photo center point: 19.1° N, 53.2° E

Nadir to Photo Center: Northwest

Spacecraft Altitude: 186 nautical miles (344km)
Click for Google map
Width Height Annotated Cropped Purpose Links
1000 pixels 576 pixels No Yes Earth From Space collection Download Image
540 pixels 311 pixels Yes Yes Earth From Space collection Download Image
720 pixels 480 pixels Yes Yes NASA's Earth Observatory web site Download Image
4256 pixels 2913 pixels No No Download Image
640 pixels 438 pixels No No Download Image
Other options available:
Download Packaged File
Download a Google Earth KML for this Image
View photo footprint information
Image Caption: Ar Rub' al Khali Sand Sea, Arabian Peninsula

The Ar Rub' al Khali, also known as the "Empty Quarter", is a large region of sand dunes and interdune flats known as a sand sea (or erg). This astronaut photograph highlights a part of the Ar Rub' al Khali located close to its southeastern margin in the Sultanate of Oman. Reddish-brown, large linear sand dunes alternate with blue-gray interdune salt flats known as sabkhas at image left. The major trend of the linear dunes is transverse to northwesterly trade winds that originate in Iraq (known as the Shamal winds).

Formation of secondary barchan (crescent-shaped) and star dunes (dune crests in several directions originating from a single point, looking somewhat like a starfish from above) on the linear dunes is supported by southwesterly winds that occur during the monsoon season (Kharif winds). The long linear dunes begin to break up into isolated large star dunes to the northeast and east (image right). This is likely a result of both wind pattern interactions and changes in the sand supply to the dunes.

The Empty Quarter covers much of the south-central portion of the Arabian Peninsula, and with an area of approximately 660,000 km2 it is the largest continuous sand desert on Earth. The Empty Quarter is so called as the dominantly hyperarid climate and difficulty of travel through the dunes has not encouraged permanent settlement within the region. There is geological and archeological evidence to support cooler and wetter past climates in the region together with human settlement. This evidence includes exposed lakebed sediments, scattered stone tools, and the fossils of hippopotamus, water buffalo, and long-horned cattle.