The decades-old mystery of Mars' dark slope streaks is largely resolved by a global analysis of ~2.1 million observations: seasonal wind, dust and sand dynamics — not impacts or water — produce most new streaks. The study estimates ~1.6 million distinct streaks and about 80,000 new streaks per year, with formation events often occurring near sunrise or sunset. Understanding these processes is important for Mars climate models and future human exploration.
Scientists Solve 50-Year Riddle: Seasonal Winds and Dust Explain ~2 Million Dark 'Slope Streaks' on Mars
The decades-old mystery of Mars' dark slope streaks is largely resolved by a global analysis of ~2.1 million observations: seasonal wind, dust and sand dynamics — not impacts or water — produce most new streaks. The study estimates ~1.6 million distinct streaks and about 80,000 new streaks per year, with formation events often occurring near sunrise or sunset. Understanding these processes is important for Mars climate models and future human exploration.
04:10 AM, 11/14/2025Science
New analysis links Mars' mysterious dark streaks to seasonal wind and dust
For decades, dark linear markings known as slope streaks have dotted Martian slopes and puzzled researchers. First reported in the 1970s, these streaks were variously attributed to melting ice, liquid-driven flows, impacts or seismic activity. A new global analysis, however, offers a clear, largely water-free explanation for most of these features.
What the study examined
Valentin Bickel of the University of Bern analyzed roughly 2.1 million observations taken by NASA's Mars Reconnaissance Orbiter between 2006 and 2024 and estimates about 1.6 million distinct slope streaks on Mars (some features appear multiple times across image sets). The results were published Nov. 6 in Nature Communications.
Key findings
- Dominant driver: Seasonal wind, dust and sand dynamics account for the vast majority of new slope streaks.
- Minor role for impacts and quakes: Meteoroid impacts and marsquakes can trigger streaks locally, but Bickel estimates they cause <0.1% of newly formed streaks planetwide.
- Regional clustering: Slope streaks cluster in five principal regions, and new streaks typically form when seasonal winds exceed the local threshold to mobilize dust.
- Timing of formation: Events conducive to streak formation most often occur near sunrise and sunset, which helps explain the historical scarcity of direct observations.
- Formation rate: The study reports a formation rate of about 0.05 new streaks per existing streak per year — roughly 80,000 new streaks annually given the estimate of 1.6 million streaks. Many streaks persist for decades, although precise lifetimes remain uncertain.
Notable example
On Apollinaris Mons, an extinct shield volcano just south of Mars' equator, hundreds of parallel streaks produced a striking "barcode-like" pattern. Those particular streaks were later linked to a nearby meteoroid impact, illustrating that impacts can create streaks in specific situations even though they are not the main global driver.
Why this matters
Although slope streaks cover less than 0.1% of Mars' surface, the study suggests they may be the single largest contributor of dust to the Martian atmosphere. That has implications for climate modeling, surface operations and planning for future human missions, since airborne dust affects solar power, thermal control and materials degradation.
"Dust, wind and sand dynamics appear to be the main seasonal drivers of slope streak formation," Bickel wrote. Colin Wilson of the European Space Agency added that long-term, continuous and global observations are critical to revealing a dynamic Mars.
In short, this work reframes most slope streaks as a product of Mars' atmospheric and surface-grain interactions rather than widespread liquid activity or frequent impact-triggered landslides. Future orbiters and long-duration monitoring will help refine formation rates, lifetimes and the role these streaks play in the planet's dust cycle.