Post #4838

2 million black 'streaks' on Mars finally have an explanation, solving 50-year mystery Martian "slope streaks" are dark albedo features that cover the slopes of topographical features across the Red Planet. They were discovered in the 1970s, and scientists initially assumed they were evidence of landslides caused by melting ice. But while scientists still think that the streaks are the result of landslides, a study published in May revealed that these landslides are actually triggered by "dry processes" that do not involve any water. This narrowed down the list of potential causes but did not conclusively settle the debate around the streaks' origins. One of the most famous examples of these streaks is on Apollinaris Mons — an extinct shield volcano located just south of Mars' equator. Here, hundreds of parallel streaks can be seen on a single side of a large ridge, giving the structure a "barcode-like" appearance (see below). These streaks appeared at some point between 2013 and 2017, and scientists later realized that they were the result of a nearby meteoroid impact, Live Science's sister site Space.com reported. As a result, some researchers assumed that meteoroid impacts and other seismic events, such as marsquakes, are responsible for birthing most slope streaks. But a new study, published Nov. 6 in the journal Nature Communications, suggests that this is not the case. Instead, an analysis of around 2.1 million slope streaks, photographed by NASA's Mars Reconnaissance Orbiter between 2006 and 2024, revealed that almost all new streaks are the result of seasonal wind and dust erosion. (The study estimates the total number of slope streaks on Mars to be around 1.6 million, but some streaks were included in multiple image sets.) "Dust, wind and sand dynamics appear to be the main seasonal drivers of slope streak formation," the study's sole author Valentin Bickel, a planetary scientist at the University of Bern in Switzerland who also co-authored the May study, said in a statement. "Meteoroid impacts and quakes seem to be locally distinct, yet globally relatively insignificant drivers [of streak formation]," he added. Bickel estimates that less than 0.1% of newly formed slope streaks are created by meteoroid impacts or marsquakes. Source:Live Science @EverythingScience