Safsaf Oasis, Egypt, April 16 1994.
© National Aeronautics & Space Administration / Science & Society
The left-hand image was taken by the Landsat Thematic Mapper. Wind has smoothed the desert's surface leaving diagonal lines running from upper right to lower left. The faintest trace of a river channel is visible where water has recently cut through the sand. The right-hand image shows the landscape stripped bare, revealing water-carved rock under the sand. The Oasis was clearly once a thriving river valley; the channel cut by an ancient river runs from the lower left corner towards the centre. The image was taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the Space Shuttle Endeavour. Clues such as ancient riverbeds help scientists reconstruct what a region's climate must have been in the past, and to understand and predict future climate change.