NASA’s Mars Reconnaissance Orbiter (MRO) has detected carbon dioxide snow falling on the red planet, making Mars the only body in the solar system known to host this weird weather phenomenon.
Scientists discovered the snow, which fell from clouds around the planet’s south pole, by sifting through MRO observations taken in 2006 and 2007. The planet’s south pole hosts a frozen carbon dioxide cap year-round, and the new discovery may help explain how it formed and persists, researchers said. Frozen carbon dioxide is commonly known as dry ice.
“These are the first definitive detections of carbon-dioxide snow clouds,” study lead Paul Hayne of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement the space agency issued Sept. 14 announcing the finding. “We firmly establish the clouds are composed of carbon dioxide — flakes of Martian air — and they are thick enough to result in snowfall accumulation at the surface.”
The find means Mars hosts two kinds of snowfall. In 2008, NASA’s Phoenix lander observed water-ice snow falling near the planet’s north pole.