Scientists finally solve the mystery of dust avalanches on Mars

On the night before Christmas in 2023, a meteoroid rattled the flanks of Apollinaris Mons and unleashed a flurry of dust avalanches on Mars. 

The European Space Agency’s ExoMars Trace Gas Orbiter caught the aftermath in crisp detail.

The Color and Stereo Surface Imaging System (CaSSIS) revealed a faint cluster of fresh impact craters at the base of the slope and roughly a hundred new, dark streaks raking downhill like claw marks. 

Follow-up imaging shows the impact and streak formation happened sometime between 2013 and 2017, making this a bona fide case of a rock strike triggering slope changes. Events like this, however, are the exception.

Seasonal drivers of slope streaks

A sweeping new analysis reveals that long-lived Martian slope streaks overwhelmingly appear in the presence of existing ice clouds and are driven by factors other than impacts or quakes. 

“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,” said study co-author Valentin Bickel from the University of Bern. 

How Mars makes a dust streak

Slope streaks are dark albedo features produced when a thin layer of bright, fine dust suddenly gives way and avalanches downslope, exposing the slightly darker substrate below.

There’s no liquid water involved in most cases. On today’s cold, arid Mars, these are dry mass-wasting events. 

The new census was powered by deep learning detectors running through the full Mars Reconnaissance Orbiter Context Camera (CTX) archive.

The experts catalogued more than 2.1 million streaks seen between 2006 and 2024 and tracked where and when new ones form. 

Hotspots for dust avalanches on Mars

The highest concentrations cluster in five hotspots: Amazonis, Olympus Mons Aureole (OMA), Tharsis, Arabia, and Elysium. These are dusty provinces where winds load, shuffle, and remobilize surface fines. 

Crucially, the authors estimate that fewer than one in a thousand newly formed streaks can be directly tied to non-seasonal triggers such as meteoroid impacts or marsquakes. 

The bulk of production coincides with the southern summer and autumn, when wind stress more consistently exceeds the threshold to fling sand grains and stir dust.

The model even pinpoints the most favorable moments for streak initiation: around sunrise and sunset, when temperature gradients and boundary-layer turbulence peak.

The role of clouds

The atmosphere matters not just for wind, but also for clouds. Using extensive aircraft measurements over the North Atlantic as an Earth analog, complementary work shows that more than 80% of long-lived aircraft contrails form inside pre-existing ice clouds, usually natural cirrus. 

On Mars, the atmospheric context is highly important. Streak rates rise with seasonal dust loading, and many new streaks appear where thin ice clouds and dust haze are common.

In both cases, background clouds modulate radiative and thermal conditions that set the stage for what follows. 

For Mars, that means the dusty, hazy seasons are prime time for streak creation. For Earth, it suggests climate-aware flight planning should consider existing cloud cover. 

A planet that rearranges its dust

Quantitatively, the new work derives a global, normalized formation rate of roughly 5% per Mars year across streak-bearing terrains, implying that tens of thousands of CTX-scale streaks are “born” each Martian year. 

Given typical streak lifetimes of a couple of decades, the global population could be replenished on ~20-Mars-year cycles if conditions remain steady. 

Streak production isn’t uniform. Some cells tick along quietly, while others experience “bursts” where dozens of new streaks appear between image pairs. Those bursts tend to occur in the dusty hotspots and during the windy season. 

Triggers for Mars’ dust avalanches

The analysis also used the InSight mission’s marsquake catalog to search for seismic triggers.

A handful of events in Elysium appear to have been followed by small local streak bursts, suggesting that shaking can tip marginal slopes into motion. 

But with only two Mars years of seismic coverage and significant uncertainty in epicenter localization, the safest conclusion is that quakes can matter locally – just not very often at the planetary scale captured by orbital imaging. 

Impact-triggered avalanches are rare

The Apollinaris Mons episode is a perfect example of an impact-triggered streak flurry, and it helps anchor the statistics.

Such impact-launched avalanches happen, but they’re rare compared to the steady drumbeat of wind-driven slides. 

That rarity matches the new global estimate that only ~0.1% of the annually formed streak population can be directly attributed to non-seasonal processes like meteoroid impacts and quakes.

Put differently, the Red Planet’s most prolific artist is its atmosphere, not its incoming rocks. 

Why the research matters

These insights also change how we observe Mars. By linking streak formation to seasons, dust loading, and time of day, scientists can better predict when the surface will shift.

Mission teams can now target sunrise and sunset over the five major hotspots during southern summer and fall to catch the landscape in motion.

“These observations could lead to a better understanding of what happens on Mars today,” said Colin Wilson, ESA’s project scientist for the ExoMars Trace Gas Orbiter. 

“Obtaining long-term, continuous, and global-scale observations that reveal a dynamic Mars is a key objective of present and future orbiters.”

Future missions to Mars

Understanding how dust is mobilized and redeposited isn’t just a geomorphic curiosity. Slope streaks speak to the vigor of Mars’ present day dust cycle, which is the same engine that scours solar panels, hazes the air, seeds clouds, and shapes climate. 

The new streak census reveals a planet that is still actively reshaping its cover with every windy season.

For engineers, that knowledge guides where to land, when to power-budget, and how to schedule imaging. For scientists, it sharpens the search for any processes that do still require liquids.

And for all of us, it turns a seemingly static world into one that is restlessly alive with dust. 

“Dust, wind and sand dynamics appear to be the main seasonal drivers of slope streak formation,” Bickel noted.

The Trace Gas Orbiter will keep watching, mapping atmospheric gases and water-rich terrains while CaSSIS returns close-ups of the latest scratches. 

The research is published in the journal Nature Communications.

Image Credit: European Space Agency

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