Streaks on the slopes of Mars, known as recurring slope lineae (RSL), may have their origins explained thanks to recent research. These dark, seasonal markings are believed to result from either briny water thawing from seasonal ice or the movement of dry sand. Investigations led by the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) have provided new insights into this intriguing phenomenon.
On December 24, 2023, the TGO captured images of streaks formed by a dust avalanche on the slopes of Apollinaris Mons. The images, taken by the orbiter’s Colour and Stereo Surface Imaging System (CaSSIS), reveal a faint clustering of impact craters alongside the dark streaks at the slope’s base. These findings were detailed in a paper titled “Dust, sand and wind drive slope streaks on Mars,” published in Nature Communications.
Valentin Tertius Bickel, a postdoctoral researcher at the University of Bern, emphasized that recent geostatistical evidence indicates that RSL can arise from “dry,” non-seasonal factors. Nonetheless, he noted a significant gap in direct, quantitative measurements regarding the rate and causes of dark streak formation. The streaks observed by the TGO were determined to stem from meteorite impacts occurring between 2013 and 2017.
Bickel utilized machine learning to analyze over two million streaks documented by NASA’s Mars Reconnaissance Orbiter (MRO) from 2006 to 2024. His research suggests these features are often linked to dry, non-seasonal events, including meteoroid impacts, marsquakes, and wind activity. Through this analysis, he developed a “streak census,” revealing that the majority of these features cluster in five distinct hotspots over the observed 19-year period. Notably, he found that approximately 0.1% of the annually formed streaks could be directly attributed to significant events like meteoroid impacts and marsquakes.
Bickel stated in an ESA press release, “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.” These results contribute to a growing body of evidence that may clarify the underlying causes of dark streaks on Mars and help scientists understand the dynamic forces shaping the planet’s climate.
Colin Wilson, ESA’s project scientist for the TGO, commented, “These observations could lead to a better understanding of what happens on Mars today. Obtaining long-term, continuous, and global-scale observations that reveal a dynamic Mars is a key objective of present and future orbiters.” Gaining insight into the dynamics of Mars’ environment is crucial for answering fundamental questions regarding the planet’s history, including the disappearance of surface water and the potential for past life.
Currently, nine missions operated by five space agencies are actively exploring Mars, with additional robotic missions planned. Crewed missions are also anticipated before mid-century, furthering humanity’s understanding of the Red Planet and its capacity for sustaining life.
