NASA Chasma Boreale and North Polar Ice Cap of Mars

Mars has bright polar caps of ice that are easily visible from telescopes on Earth. A seasonal cover of carbon-dioxide ice and snow is observed to advance and retreat over the poles during the Martian year. Scientists using radar data have found a record of the most recent Martian ice age recorded in the north polar ice cap. via NASA http://www.nasa.gov/image-feature/chasma-boreale-and-the-north-polar-ice-cap