Clouds Over Mars

While photographers had to improvise to include clouds in their views for most of the 19th century, by the late 20th century it was possible for robotic cameras to successfully record these weather patterns—all without direct human contact. Landing on July 4, 1997, the Mars Pathfinder was a spacecraft sent by NASA to explore the red planet. Its six-wheeled robotic rover, Sojourner, helped analyze the climate and geology of Mars and conduct experiments with its atmosphere and soil composition. As in the survey expeditions in the American West of the 1860s and 1870s, photography played a vital role in this massive effort to gather data about an unknown land. Sojourner was equipped with a camera on an expandable pole that sent images of Mars back to Earth. This view of the Martian sky shows stratus clouds, consisting of ice condensed on reddish dust particles, suspended low in the atmosphere.