When a meteoroid shook the edge of Apollinaris Mons on Mars, it triggered streaks that carved a hundred new scratches on the surface. The European Space Agency’s ExoMars Trace Gas Orbiter captured these dust avalanches on the slopes the night before Christmas in 2023.

This image from the Colour and Stereo Surface Imaging System (CaSSIS) onboard the European orbiter also shows the faint cluster of impact craters in the discoloured region at the base of the slopes. Additional imagery helped scientists determine that the impact and streak formation occurred between 2013 and 2017.

Scientists believe these streaks on Mars form when layers of fine dust suddenly slide off steep terrain. With no evidence of water, they concluded that these features mostly result from dry processes driven by wind and dust activity.

A new study published in Nature Communications suggests that this is a rare event; fewer than one in a thousand streaks are caused by rocks smashing into Mars. In most cases, seasonal changes stirring up dust and wind are to blame.

“Dust, wind and sand dynamics appear to be the main seasonal drivers of slope streak formation. Meteoroid impacts and quakes seem to be locally distinct, yet globally relatively insignificant drivers,” explains lead author Valentin Bickel from the University of Bern in Switzerland.

Valentin used deep learning algorithms to analyse more than two million slope streaks in images from NASA's Mars Reconnaissance Orbiter (MRO). The resulting streak census locates them in five distinct hotspots on Mars between 2006 and 2024.

“These observations could lead to a better understanding of what happens on Mars today. Obtaining long-term, continuous and global-scale observations that reveal a dynamic Mars is a key objective of present and future orbiters,” says Colin Wilson, ESA’s project scientist for the ExoMars Trace Gas Orbiter.

The Trace Gas Orbiter continues to image Mars from orbit to understand its ancient past and potential habitability. The spacecraft returns spectacular images and provides the best inventory of atmospheric gases and mapping of the planet’s surface for water-rich locations.

Understanding the history of water on Mars and whether it once allowed life to flourish is at the heart of ESA’s ExoMars missions.

The image covers an area of approximately six square kilometres and was captured on 24 December 2023. Mars location: 7.1°S, 173.4°E. CaSSIS image MY37_027142_351.

“Dust, Sand and Wind Drive Slope Streaks on Mars” by Valentin Bickel was published in Nature Communications on 6 November 2025.