Imagine a cosmic collision so powerful it leaves scars on the face of Mars. That’s exactly what happened when a rare meteoroid struck the edge of Apollinaris Mons, a towering volcano on the Red Planet, creating a dramatic display of dust avalanches and carving over a hundred new streaks into its slopes. But here’s where it gets fascinating: these streaks, captured by the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter just before Christmas 2023, aren’t just random marks—they tell a story of Mars’ dynamic and ever-changing surface.
The images, taken by the Color and Stereo Surface Imaging System (CaSSIS), reveal not only the fresh streaks but also a faint cluster of impact craters in a discolored region at the base of the slopes. Additional analysis confirmed that this event occurred between 2013 and 2017, adding another layer to the mystery of Mars’ geological activity.
Scientists have long debated the origins of these streaks. While water might seem like an obvious culprit, there’s no evidence of it here. Instead, researchers believe these features are the result of dry processes—layers of fine dust sliding off steep terrain, driven primarily by wind and dust activity. And this is the part most people miss: while meteoroid impacts like this one are rare, they’re not the main cause of these streaks. A groundbreaking study published in Nature Communications suggests that fewer than one in a thousand streaks are caused by such collisions. Most are actually triggered by seasonal changes, as dust and wind stir up the Martian surface.
Lead author Valentin Bickel from the University of Bern in Switzerland explains, ‘Dust, wind, and sand dynamics appear to be the main seasonal drivers of slope streak formation. Meteoroid impacts and quakes, while locally distinct, are relatively insignificant on a global scale.’ To reach this conclusion, Bickel and his team used deep learning algorithms to analyze over two million slope streaks from images captured by NASA’s Mars Reconnaissance Orbiter (MRO) between 2006 and 2024. The resulting streak census identified five distinct hotspots on Mars where these features are most common.
But here’s the controversial part: Could these streaks hold clues to Mars’ past habitability? Colin Wilson, ESA’s project scientist for the ExoMars Trace Gas Orbiter, believes so. ‘These observations could lead to a better understanding of what happens on Mars today,’ he says. ‘Obtaining long-term, continuous, and global-scale observations that reveal a dynamic Mars is a key objective of present and future orbiters.’
The Trace Gas Orbiter continues to play a pivotal role in this quest, imaging Mars from orbit to uncover its ancient past and potential for life. It captures spectacular images, maps the planet’s surface for water-rich locations, and provides the most detailed inventory of atmospheric gases to date. Understanding the history of water on Mars—and whether it once supported life—remains at the heart of ESA’s ExoMars missions.
So, what do you think? Are these streaks just the result of wind and dust, or could they hint at something more profound about Mars’ history? Let us know in the comments—we’d love to hear your thoughts!