Space History Photo: Evidence for Recent Liquid Water on Mars: Gullies

liquid, mars, water, gullies
Gully landforms on Mars. (Image credit: NASA)

In this historical photo from the U.S. space agency, gully landforms proposed to have been caused by geologically-recent seepage and runoff of liquid water on Mars are found in the most unlikely places. They typically occur in areas that are quite cold, well below freezing all year round. Like the old adage about moss on trees, nearly all of them form on slopes that face away from sunlight.

Most of the gullies occur at latitudes between 30 and 70. The highest latitude at which martian gullies have been found is around 70-75 S on the walls of pits developed in the south polar pitted plains. If you were at this same latitude on Earth, you would be in Antarctica. This region spends much of the winter--which lasts approximately 6 months on Mars--in darkness and at temperatures cold enough to freeze carbon dioxide (around -130C or -200F). Nevertheless, gullies with very sharp, deep, v-shaped channels are seen on the pit walls.

Based upon the locations of the tops of the channels on the slope shown here on June 22, 2000, the inferred site of liquid seepage is located at a layer in the pit wall about 1/3 of the way down from the top of the MOC image. The channels start wide and taper downslope. The area above the channels is layered and has been eroded by mass movement dry avalanching of debris--to form a pattern of chutes and ridges on the upper slope of the pit wall. The top layer appears to have many boulders in it (each about the size of a small house), these boulders are left behind on the upper slopes of the pit wall as debris is removed.

Each weekday, looks back at the history of spaceflight through photos (archive).

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at:

NASA Archives
U.S. Space Agency

The National Aeronautics and Space Administration (NASA) is the U.S. government agency in charge of the civilian space program as well as aeronautics and aerospace research. Founded in 1958, NASA is a civilian space agency aimed at exploring the universe with space telescopes,  satellites, robotic spacecraft, astronauts and more. The space agency has 10 major centers based across the U.S. and launches robotic and crewed missions from the Kennedy Space Center in Cape Canaveral Florida. It's astronaut corps is based at the Johnson Space Center in Houston. To follow NASA's latest mission, follow the space agency on Twitter or any other social channel, of visit: