Seismic data from NASA’s InSight mission shows Mars’ thin atmosphere leaves it vulnerable to frequent meteorite bombardments

Photo: NASA/JPL-Caltech/USGS

New research paints a picture of a more active Mars than previously imagined. The Red Planet is likely struck by a space rock nearly every day, generating seismic waves and leaving behind an 8-metre-wide crater, according to a new study.

Further, every month, the Red Planet also appears to be hit by a meteorite that leaves a 30-metre crater, the paper published in journal Nature Astronomy noted. 

These findings may help inform safety strategies for future missions, both robotic and human. Every year, approximately 17,000 meteorites strike Earth, but the majority of them burn up as they enter the atmosphere. Because Mars’ atmosphere is 100 times thinner, the surface is more vulnerable to larger and more frequent meteorite impacts.

“This rate [of meteorite impacts] was about five times higher than the number estimated from orbital imagery alone. Aligned with orbital imagery, our findings demonstrate that seismology is an excellent tool for measuring impact rates,” Geraldine Zenhaeusern, staff of professorship for seismology and geodynamics, ETH Zurich, said in a statement.

Previously, scientists used orbital images and models to predict meteorite impacts on the Moon and extrapolate them to Mars. However, this was difficult because experts had to account for the Red Planet’s stronger gravitational pull and proximity to the asteroid belt, both of which increase the frequency of meteorite impacts.

Further, orbital imagery is not very good at detecting craters on Mars, as they are not well-preserved due to regular sandstorms. 

The study used seismological data from a seismometer aboard the National Aeronautics and Space Administration (NASA) InSight mission, which was launched in 2018 to study the Red Planet’s interior structure. It landed in Elysium Planitia, a flat-smooth plain just north of the equator. The mission ended in 2022.

When a meteorite strikes the planet, the impact generates seismic waves, which travel through the crust and mantle, before being recorded. “The sensitive InSight seismometer could hear every single impact within the landers’ range,” Zenhaeusern explained.

There are distinct differences between earthquakes caused by tectonic movements and meteorite impacts. A magnitude 3 earthquake on Mars lasts several seconds, whereas an impact of the same size lasts only 0.2 seconds or less. The team discovered more than 80 marsquakes that could be caused by meteorite strikes.

The team counted the number of craters formed around the InSight lander over the course of one year. They then extrapolated this information to calculate the number of impacts that occur annually on the planet’s surface. Overall, they discovered that the planet is likely hit by 280 to 360 meteorite impacts per year.

These findings could help scientists learn about Mars’ history. Natalia Wojcicka, research associate at Imperial College London explained that seismic data can tell us how often meteorites hit Mars and how these impacts change its surface. This, she added, can help scientists piece together a timeline of the red planet’s geological history and evolution. 

“You could think of it as a sort of ‘cosmic clock’ to help us date Martian surfaces, and maybe, further down the line, other planets in the Solar System,” she said in a statement.

Going forward, the team hopes that future lander missions carry more affordable seismometers to paint a complete picture of Mars’ impact rates and inner structure, including the makeup of the different layers and their depth. 

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