NASA's Mars Global Surveyor shows three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough.

These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

View all Images