This is a Dust Avalanche on Mars

Scientists have observed slope streaks on Mars for decades. The mechanism behind the slope streaks has been debated, with some suggesting they are the result of dry mechanics or water activity on the Red Planet.

Scientists with the Mars Odyssey mission have verified that carbon dioxide frost is behind the slope streaks.

Slope streaks can be seen on the walls of craters or on the sides of hills. The dust and rocks on a slope can be moved by something as small as a dust devil, or even an impact event. There are events that cause dry dust on Mars.

The images and data from the Odyssey spacecraft show that the carbon dioxide frost can cause an avalanche.

Odyssey has been in the air for over a decade. The perfect time to observe frost activity is at 7 a.m. local Mars time, which is the same time as on Earth.

Last year, scientists were surprised to see blue and white frost illuminated by the rising Sun in images taken by the visible light camera on board Odyssey. The frost appeared more widely in areas where the visible light camera was not present, as shown by the heat-sensitive camera in Odyssey.

Sylvain Piqueux of NASA's Jet Propulsion Laboratory in Southern California led the paper.

NASA says that because Mars has so little atmosphere, the Sun warms frost that builds up overnight. Dry ice can be deposited into the atmosphere in minutes.

The cold- temperature signature from the THEMIS of frost was first noticed by an intern at the Jet Propulsion Laboratory. These temperatures were less than the width of a human hair.

The first thought was that ice could be buried there.

Slope streaks or even larger slides were observed in those areas. In their paper, the team explains.

“At sunrise, sublimation-driven winds within the regolith are occasionally strong enough to displace individual dust grains, initiating and sustaining dust avalanches on steep slopes, forming ground features known as slope streaks. This model suggests that the CO2 frost cycle is an active geomorphological agent at all latitudes and not just at high or polar latitudes, and possibly a key factor maintaining mobile dust reservoirs at the surface.”

— Paper: Gardening of the Martian Regolith by Diurnal CO₂ Frost and the Formation of Slope Streaks

Dry ice frost mixed with fine grains of dust obscured it in visible light, but not in the visible images of the authors. Some of the dark streaks that can stretch 3,300 feet (1,000 meters) down Martian slopes are thought to be caused by dirty frost. They knew the streaks were caused by dust storms that slowly change the mountainsides across the planet.

If you were there, what would you see? The scientists think the dust avalanches look like a river of dust releasing a trail of material behind them. As the dust travels downhill, it exposes darker material underneath.

Chris Edwards, a paper co-author at Northern Arizona University, said that every time we send a mission to Mars, we discover exotic new processes. You have to think outside the box to understand Mars.

The team's paper is in JGR Planets.

There are spots on Mars. NASA/JPL-Caltech/UArizona