High-altitude vertical photo of rock-covered glaciers in the Dry Valleys of Antarctica, long considered one of the most Mars-like places on Earth. These glaciers contain very old, slow-moving ice protected by a layer of rocky debris, similar to the features on Mars recently probed by the SHARAD radar on NASA's Mars Reconnaissance Orbiter. Ongoing research in the Dry Valleys including radar overflights will help scientists better understand the history of water and climate on Mars. USGS photo.