Scientists Link Mars’ Dark Slope Streaks to Seasonal Winds — and a Single Meteoroid Impact

A Martian mystery clarified

At first glance, the dark marks in this image could be mistaken for a cosmetic smudge — but they are most likely the scars of dust avalanches on Mars. The European Space Agency’s ExoMars Trace Gas Orbiter photographed the streaks on Apollinaris Mons on 24 December 2023, showing patterns that researchers say formed after a meteoroid struck the volcano’s rim sometime between 2013 and 2017.

Millions of streaks, a seasonal explanation

A new study in Nature Communications led by Valentin Tertius Bickel of the University of Bern cataloged more than 2 million dark slope streaks across Mars. Image analysis in that work suggests these features rarely require dramatic triggers such as impacts or marsquakes. Instead, many streaks appear to form through ordinary seasonal processes: during southern summer and autumn Mars' winds intensify and can loft or push fine dust and sand down steep slopes.

Observations indicate the strongest wind stresses at numerous locations occur near dawn and dusk, times when most orbiters do not regularly image the surface. That timing helps explain why direct observations of streak formation are rare.

Dry avalanches, not flowing water

The new paper adds to mounting evidence that the streaks are dry dust avalanches rather than signs of liquid water. Scientists first speculated about a water link after NASA’s Viking missions in the 1970s discovered enigmatic slope markings, but recent analyses — including a May paper coauthored by Bickel titled “Streaks on martian slopes are dry” — argue the features are driven by dust dynamics and play a significant role in the martian dust cycle. The streaks also tend to fade over years to decades.

What’s next?

To further test the wind-driven hypothesis, researchers recommend targeted imaging at dawn and dusk to capture streaks forming when wind stresses peak. While the findings weaken arguments that these streaks indicate present-day habitability, other missions like NASA’s Perseverance rover continue to search for independent clues about Mars’ past potential for life.

Bottom line: High-resolution, time-targeted observations—especially around sunrise and sunset—could confirm that seasonal winds and dry dust avalanches are the dominant forces behind the Red Planet’s dark slope streaks.