The first results from NASA's quake-hunting InSight Mars lander just came out, and they reveal that Mars is a seismically active planet. Space.com reports: Martian seismicity falls between that of the moon and that of Earth, [says InSight principal investigator Bruce Banerdt, of NASA's Jet Propulsion Laboratory]. "In fact, it's probably close to the kind of seismic activity you would expect to find away from the [tectonic] plate boundaries on Earth and away from highly deformed areas," he said. InSight's observations will help scientists better understand how rocky planets such as Mars, Earth and Venus form and evolve, mission team members have said. The mission's initial science returns, which were published today (Feb. 21) in six papers in the journals Nature Geoscience and Nature Communications, show that InSight is on track to meet that long-term goal, Banerdt said.
The new studies cover the first 10 months of InSight's tenure on Mars, during which the lander detected 174 seismic events. These quakes came in two flavors. One hundred and fifty of them were shallow, small-magnitude tremors whose vibrations propagated through the Martian crust. The other 24 were a bit stronger and deeper, with origins at various locales in the mantle, InSight team members said. (But even those bigger quakes weren't that powerful; they landed in the magnitude 3 to 4 range. Here on Earth, quakes generally must be at least magnitude 5.5 to damage buildings.) That was the tremor tally through September 2019. InSight has been busy since then as well; its total quake count now stands at about 450, Banerdt said. And all of this shaking does indeed originate from Mars itself, he added; as far as the team can tell, none of the vibrations were caused by meteorites hitting the Red Planet. So, there's a lot going on beneath the planet's surface. What's interesting to note is that unlike Earth, where most quakes are caused by tectonic plates sliding around, Mars' quakes are caused by the long-term cooling of the planet since its formation 4.5 billion years ago. "As the planet cools, it contracts, and then the brittle outer layers then have to fracture in order to sort of maintain themselves on the surface," Banerdt said. "That's kind of the long-term source of stresses."
"A wealth of information can be gleaned from InSight's quake measurements," reports Space.com. "For example, analyses of how the seismic waves move through the Martian crust suggest there are small amounts of water mixed in with the rock, mission team members said." They can't say one way or the other whether there are large underground reservoirs of water at this point, but the research is convincing.
The new papers also mention a variety of other discoveries as well. "For example, InSight is the first mission ever to tote a magnetometer to the Martian surface, and that instrument detected a local magnetic field about 10 times stronger than would be expected based on orbital measurements," the report says. "InSight is also taking a wealth of weather data, measuring pressure many times per second and temperature once every few seconds. This information helps the mission team better understand environmental noise that could complicate interpretations of the seismic observations, but it also has considerable stand-alone value."
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