Part of Antarctica is captured in this mosaic of 11 Galileo images. The mosaic spans about 1600 km (992 mi) across the south polar latitudes of our planet. This part of Antarctica lies south of South America. At lower left, the dark blue Ross Sea is visible, bounded by the Ross Ice Shelf on the right. The Amundsen Sea is just visible at the top and center of the image.

In Australia, the Simpson Desert, 451 km (280 mi) wide by 547 km (340 mi) long, lies southeast of Alice Springs. At lower left is Lake Eyre, a salt lake below sea level. Its water level changes dramatically throughout the seasons. At the time this image was taken the lake was nearly dry. At lower right is the greenish Lake Blanche. Fields of linear sand dunes stretch north and east of Lake Eyre, shaped by prevailing winds from the south. The various sources and age of the sand can be determined by their color.

This space shuttle view of the Atlantic Ocean and Mediterranean Sea illustrates an important feature of Earth-a seacoast. Earth is the only planet with borders of land adjacent to bodies of water because it is the only planet in the Solar System where liquid water is stable at the surface. Seas are important because water has been the catalyst for the development of life on our planet. The Strait of Gibraltar is the border between Africa and Europe. In Spain, to the left, the small spike of land is the Rock of Gibraltar; Africa is on the right side of the image.

This space shuttle image of the Colorado River in Arizona captures the Grand Canyon. The canyon is 30 km (18 miles) across at its widest point and 1.6 km (1 mile) deep at rock bottom. It is 446 km (277 miles) long and covers an area that is over 5000 square km (about 2000 square miles).

Here are a few theories. The Grand Canyon could have been created by the erosional action of the Colorado River on the surface as this region has continued to rise high above sea level over the last several million years. Another theory is that 15,000 to 40,000 years ago an iron rock 25 meters across impacted the Earth at a speed of 15 kilometers per second. The energy released could have been equivalent to that of a 4-megaton nuclear explosion.

Radar's ability to penetrate dry sand cover produced the discovery in this image of Wadi Kufra, Libya: a previously unknown branch of an ancient river, buried for thousands of years under the sands of the Sahara Desert. This area is near the Kufra Oasis in southeast Libya. The image was acquired by the SIR-C/X-SAR imaging radar when it flew aboard the space shuttle Endeavour in October, 1994. This image reveals a system of old, now inactive stream valleys which, during periods of wetter climate, carried running water northward across the Sahara. The region now receives only a few millimeters of rainfall per year, and the ancient river valleys are mostly buried by windblown sand.