* Astronomy

These images of the Safsaf Oasis in south-central Egypt show the surface of the desert and ancient water-carved rock hidden under the sand.


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The top image, taken by the Landsat Thematic Mapper, shows the desert’s surface. The wind has smoothed the land leaving long diagonal lines that run from the upper right to the lower left of the image. Only the faintest trace of a river channel is visible where water has recently cut through the sand.

The lower image shows what the landscape might look like if stripped bare of sand. The Safsaf Oasis was clearly once a thriving river valley. Sinuous black channels cut by the meandering of an ancient river wind their way through the image.

The widest of these runs from the lower left corner towards the centre of the image.
The image was taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR), which uses radar to penetrate the thin sand cover.

The sensor flew aboard the space shuttle Endeavour, and took this image on April 16, 1994.