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A meteoroid strike on the slopes of Apollinaris Mons, a long-dormant volcano near Mars’ equator, sent dust cascading down its walls sometime between 2013 and 2017. Scientists confirmed the event after the European Space Agency’s ExoMars Trace Gas Orbiter captured a December 24, 2023, image showing more than 100 new dark streaks. Researchers say the impact shook loose fine dust on the steep terrain and created sudden avalanches that are still visible today.
The orbiter used its main imaging camera to spot a small cluster of fresh craters at the base of the volcano. These craters appeared with pale patches where dust settled after sliding downhill. NASA’s Mars Reconnaissance Orbiter later reviewed older images of the same area and confirmed that the streaks were not present a decade ago.
Slope streaks look like narrow, dark lines stretching down a hillside. Many can reach hundreds of meters long. They stand out against the lighter surface and slowly fade as new dust lands on them. They do not contain water, ice, or mud. They are simply dust slides on a very dry world.
Scientists rarely see slope streaks triggered by meteoroid impacts. A study published in Nature Communications examined millions of detections from 2006 to 2024. It found that only a tiny fraction come from impacts. Most form when wind pushes sand grains into dust layers, which then fall under their own weight. The team counted about 1.6 million unique streaks across the planet.
Dust and wind drive most of Mars’ surface changes today. When winds reach a certain strength, they can push sand grains into dust piles. The pressure lifts the dust and sends it downhill. This usually happens during the southern summer and autumn seasons, when storms are more common. The darkest streak clusters appear in dusty regions at low elevation where loose soil builds up.
The new streaks at Apollinaris Mons offer a look at an old volcano reacting to a modern impact. The mountain is about 200 kilometers wide and 5 kilometers tall. Although it has been inactive for a long time, dust continues to pile on its slopes. When the meteoroid hit the ground nearby, vibration and shock waves disturbed the buildup, exposing darker ground underneath.
These findings also tie into a long-running debate in Mars research. For years, some scientists suggested that slope streaks or similar features might involve small amounts of briny water. The new study supports a dry explanation. Researchers say they see no sign of liquid water in these streaks, even in regions where they appear very often.
Understanding how Mars moves dust around is important for future missions. Dust shapes the climate, affects solar power for landers, and changes the surface that rovers explore. The ExoMars orbiter continues to study gases and the surface to learn more about Mars’ past and present. As more high-resolution images come in, scientists expect to find more examples of changes on the planet’s surface happening in real time.
Source: Dust, sand and wind drive slope streaks on Mars
