Mount Everest and surrounding mountains, ridges, and valleys as viewed through thick cloud cover by NASA's Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) (top image) and in optical light under clear conditions by the crew of the space shuttle Endeavour. Mount Everest and its neighbor Lhotse (27,890 ft.) are indicated by crosses. The area shown is approximately 43 miles by 24 miles (70 km by 38 km).
The radar image was taken in April 1994 and shows deep snow cover, while the optical photograph was taken in October 1994 and shows minimal snow cover. Snow appears blue in the radar image and white in the optical photograph. The curving and branching features seen in both images are glaciers. They show up as blue, purple, red, yellow, and white in the radar image, depending on ice roughness, water content, and stratification; however, they only appear as gray or white in the photograph.
Image Credit: NASA/Jet Propulsion Laboratory (JPL) (top image). NASA, STS-68 crew (bottom image).