NASA Insight mission proves Mars crust is thicker than scientists thought

Planet Mars (Nasa)

Planet Mars (Nasa)

Mars’ outermost layer is denser and more uniform than scientists once thought.

That’s according to new findings from Nasa’s Insight mission which are published Thursday in the journal. Science.

A Mars geology mission, NASA’s Insight lander has been listening to Marsquakes since 2018, using information in the speed of waves traveling through the Red Planet to better understand its deep structure. But the new findings released on Thursday provide a new understanding of the structure of the planet’s crust, from the surface to depths of between 8 and 48 miles, all thanks to Insight capturing the vibrations generated by a meteor strike in December 2021.

“Until now, our knowledge of the Martian crust was based on a single point measurement under the InSight lander,” said Doyeon Kim, senior geophysicist at the Institute of Geophysics at ETH Zurich and senior scientist at the originator of the study, Doyeon Kim, in a statement.

December’s meteor strike created what are known as surface waves, seismic vibrations that propagate along a planet’s surface rather than from the source of an earthquake deep inside. interior of the planet. The fact that Insight single-handedly recorded surface waves is a milestone.

“This is the first time that surface seismic waves have been observed on a planet other than Earth,” Dr Kim said. “Even the Apollo missions to the Moon did not achieve this.”

Surface waves propagate at different speeds depending on the density of the material they pass through, and surface waves reaching Insight from the meteorite impact location about 3,500 miles away indicated that the Martian crust is denser and more uniform in structure than previously thought. This is partly because measurements of the crust directly below Insight are not as dense as they appear typical of the planet.

An illustration of how NASA's Insight landing mission was able to record the seismic waves generated by a meteorite strike on the Red Planet on December 24, 2021 (ETH Zurich / Doyeon Kim, Martin van Driel and Christian Boehm)

An illustration of how NASA’s Insight landing mission was able to record the seismic waves generated by a meteorite strike on the Red Planet on December 24, 2021 (ETH Zurich / Doyeon Kim, Martin van Driel and Christian Boehm)

“The crustal structure beneath InSight’s landing site may have been formed in a unique way, perhaps when material was ejected during a large meteorite impact more than three billion years ago. years,” Dr. Kim said. “This would mean that the structure of the crust below the lander is probably not representative of the general structure of the Martian crust.”

The results challenge the main theory to explain what is called the Mars dichotomy, the fact that the northern hemisphere consists largely of volcanic lowlands, while the southern hemisphere is a plateau cratered by meteorites. . It had been speculated that the crust beneath the two hemispheres was radically different material, but the new study suggests that is not the case.

“As things stand, we don’t yet have a generally accepted explanation for the dichotomy because we’ve never been able to see the deep structure of the planet,” said Domenico Giardini, professor of seismology and geodynamics. at ETH Zurich, in a statement. “But now we’re starting to find that out.”

The new findings come just in time, as NASA’s Insight mission is set to end soon, as the lander loses power due to dust buildup on its solar panels. But in May, the lander gave one last gift: it recorded the largest Mars quake ever observed, a magnitude 5 quake, which produced more surface waves and will allow Dr Kim and others researchers to make more discoveries about the structure of Mars even after Insight is shut down. down.

“It’s crazy. We’ve been waiting for these waves for so long, and now, just months after the meteor impacts, we’ve seen this large earthquake that has produced extremely rich surface waves,” Dr Kim said. These allow us to see even deeper into the crust, down to a depth of about 90 kilometres.”

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