Mars has seasonal polar ice caps that are composed of dry ice (carbon dioxide). During the planet’s springtime season, the sun shines on the ice, causing it to turn from a solid to a gas. Unlike water ice, which melts into liquid when heated, Mars’ dry ice changes directly from solid to vapor. This transition leaves patterns of erosion behind on the planet’s surface. This type of erosion does not occur naturally anywhere on Earth because our planet is too warm.