 This illustration made available by NASA in 2018 shows the InSight lander drilling into the Martian surface. (NASA via AP) | | | Marsquakes. Since NASA's InSight probe landed near the Martian equator just over a year ago, researchers have recorded scores of them — the first-ever seismic events studied on another planet. Presenting at the annual meeting of the American Geophysical Union last week, mission scientists said the marsquakes were small. Even the strongest of them would be imperceptible to a human on Earth. But if scientists can detect enough of them, they may be able to decipher the mysteries beneath Mars' surface. Early in its history, the Red Planet looked much like Earth: It had a magnetic field, an atmosphere, and liquid water on its surface. But at some point, the internal dynamo that generated Mars' magnetic field shut down. Since seismic waves are affected by the materials they encounter as they travel through the interior, they can teach scientists about the makeup of the planet. They may even reveal the presence of underground water reservoirs or active volcanic plumes. The two largest marsquakes seemed to come from a series of fissures called the Cerberus Fossae, 1,000 miles away from the InSight probe's landing site. These features formed from stretching of the Martian crust and are thought to have experienced floods and lava flows in the past tens of millions of years. An analysis led by University of Paris physicist Alice Jacobs suggests that the quakes could stem from stress building up around the fissures — making Cerebus Fossae the first active seismic zone discovered on Mars. The seismology experiments also revealed a curious, continuous hum not related to the lander or any weather activity. "We don't know exactly where it comes from or why it's there," principal investigator Bruce Banerdt told the geoscience magazine Eos. "We don't know why it gets excited or it doesn't get excited, but we think that it has something to do with some kind of a resonance in the crustal layer that's sensitive to being excited by seismic events. And this is something that's kind of puzzling." | 
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