Images: When mars was a wetland

It may look like the inside of an abalone shell at first glance, but this is an image of the surface of Mars, composed from infrared, red and blue-green images captured by NASA's High Resolution Imaging Science Experiment (HiRISE) camera earlier this month. The camera is one of six science instruments aboard the Mars Reconnaissance Orbiter, which arrived at Mars in March and has revealed remarkable new details of the planet's past and present environments.

Researchers are particularly interested in clues that these new images may provide about Mars' past life as a wet planet. Scientists think the brighter areas in this image (of Mawrth Vallis, one of the oldest valleys on Mars) may be rich in clay, an important key to understanding the history of water on Mars because the formation of clay minerals requires that rocks be exposed to liquid water for a long period of time.