Asger Risom
A dark patch on Mars has been spreading for decades, and scientists still can’t fully explain what’s driving its slow expansion across the planet’s surface.
A dark, expanding patch on the surface of Mars has been slowly creeping across the planet for decades—and scientists still don’t fully understand why.
First photographed in 1976 by NASA’s Viking missions, the feature in the Utopia Planitia region has continued to grow, with new images confirming it has spread significantly over time.
A moving patch of volcanic material
The so-called “shadow” isn’t actually a shadow, but a vast area covered in dark volcanic material, including ash and minerals like olivine and pyroxene.
According to data from the European Space Agency, parts of the patch have shifted more than 200 miles (320 km) since it was first observed, suggesting it expands by several miles each year.
Winds are the main suspect—but not confirmed
Scientists believe Martian winds are likely responsible for the movement.
One theory is that winds are actively spreading the dark volcanic material across the surface. Another is that lighter-colored dust is being blown away, gradually revealing the darker terrain beneath.
So far, there’s no clear evidence pointing definitively to either explanation.
A region scientists have been watching for decades
The area, known as Utopia Planitia, is one of the largest plains on Mars and has long been a focus of exploration.
NASA’s Viking 2 lander touched down there in 1976, while China’s Zhurong rover explored the region more recently, uncovering signs that it may once have held a vast ocean.
The region is also believed to contain significant underground ice, making it a key area for future research.
A slow mystery still unfolding
Despite decades of observation, the expanding dark patch remains only partially understood.
What is clear is that Mars is far from static. Even without active volcanoes, the planet’s surface continues to change—driven by forces that scientists are still trying to fully explain.
Sources: European Space Agency (ESA), NASA
