Researchers Find Evidence of Boulders Tumbling After Recent Earthquakes on Mars

"If a rock falls on Mars, and no one is there to see it, does it leave a trace?" jokes the New York Times, answering "Yes, and it's a beautiful herringbone-like pattern, new research reveals." Scientists have now spotted thousands of tracks on the red planet created by tumbling boulders. Delicate chevron-shaped piles of Martian dust and sand frame the tracks, the team showed, and most fade over the course of a few years. Rockfalls have been spotted elsewhere in the solar system, including on the moon and even a comet. But a big open question is the timing of these processes on other worlds — are they ongoing or did they predominantly occur in the past?A study of these ephemeral features on Mars, published last month in Geophysical Research Letters, says that such boulder tracks can be used to pinpoint recent seismic activity on the red planet. This new evidence that Mars is a dynamic world runs contrary to the notion that all of the planet's exciting geology happened much earlier, s aid Ingrid Daubar, a planetary scientist at Brown University who was not involved in the study... To arrive at this finding, Vijayan, a planetary scientist at the Physical Research Laboratory in Ahmadabad, India, who uses a single name, and his colleagues pored over thousands of images of Mars' equatorial region. The imagery was captured from 2006 through 2020 by the High Resolution Imaging Science Experiment (HiRISE) camera onboard NASA's Mars Reconnaissance Orbiter and revealed details as small as 10 inches across. "We can discriminate individual boulders," Vijayan said. The team manually searched for chain-like features — a telltale signature of a rock careening down an incline — on the sloped walls of impact craters. Vijayan and his collaborators spotted more than 4,500 such boulder tracks, the longest of which stretched more than a mile and a half... Roughly one-third of the tracks the researchers studied were absent in early images, meaning that they must have formed since 2006... The researchers suggest that winds continuously sweeping over the surface of Mars redistribute dust and sand and erase the ejecta. Because boulder fall ejecta fades so rapidly, seeing it implies that a boulder was dislodged recently, the team suggest. And a common cause of rockfalls, on Earth and elsewhere, is seismic activity.... Since 2019, hundreds of marsquakes have been detected by NASA's InSight lander, and two of the largest occurred last year in the Cerberus Fossae region. Today the Mars lander InSight is back in operation after a two-week break to avoid dust storms, while dust storms also delayed the 19th flight of NASA's Ingenuity helicopter. And elsewhere on Mars, the Perserverance rover successfully dislodged two pebbles stuck in its sample-collecting apparatus.

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