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Hundreds of basketball-sized space rocks slam into Mars every year, leaving impact craters and rumbling across the red planet, according to a new study.
Mission planners could use the insights recorded in the data collected by a now-retired NASA mission as they determine where to land future robotic missions and astronaut crews on the red planet.
NASA’s InSight mission ended when the stationary lander lost its battle with Martian dust accumulating on its solar panels in December 2022, but the wealth of data collected by the spacecraft is still fueling new research.
The lander carried the first seismometer to Mars, and the sensitive instrument was able to detect seismic waves originating thousands of miles from InSight’s location in Elysium Planitia, a smooth plain just north of the planet’s equator.
During its time on Mars, InSight used its seismometer to detect more than 1,300 earthquakes that occur when the Martian subsurface cracks due to pressure and heat.
But InSight also captured evidence of meteoroids when they crashed into Mars.
Meteoroids are space rocks that have broken off from larger rocky bodies and range in size from dust grains to small asteroids, according to NASA. Known as meteoroids while still in space, they are called meteors as they pass through the atmosphere of Earth or other planets.
Scientists have questioned why more impacts have not been found on Mars, as the planet is located next to our solar system’s main asteroid belt, where many space rocks appear to hit the Martian surface. The Martian atmosphere is only 1% the thickness of Earth’s atmosphere, meaning more meteoroids pass through it without disintegrating.
A meteorite hit the Martian atmosphere on September 5, 2021, and then broke up into at least three pieces, each leaving behind a crater on the red planet’s surface. And that was just the beginning.
Starting in 2021, researchers examined InSight data and found that space rocks are bombarding Mars more often than previously thought, up to two to 10 times more than previously estimated, according to a new study published Friday in the journal Science Advances.
“Mars may be more geologically active than we thought, which has implications for the age and evolution of the planet’s surface,” lead study author Ingrid Daubar, associate professor of Earth, environmental and planetary sciences at the university, said in a statement Brown. “Our results are based on the small number of examples we have, but estimating the current impact rate suggests that the planet is being hit much more often than we can see using images alone.”
The team identified eight new impact craters created by meteoroids from the InSight data that orbiters orbiting the planet had previously spotted. Six of the craters were close to InSight’s landing site, and two of the distant impacts are among the largest ever detected by scientists observing the red planet, according to the study.
The two major impacts each left craters the size of football fields, and they occurred 97 days apart.
“We would expect it to happen once every few decades, maybe even once in a lifetime, but here we have two of them that are just over 90 days apart,” Daubar said. “It could just be a crazy coincidence, but there’s a really, really small chance that it’s just a coincidence. It is more likely that either the two large impacts are related, or the magnitude of the impact is much higher for Mars than we thought it was.”
The team compared data collected by InSight with that taken by NASA’s Mars Reconnaissance Orbiter to determine where the impacts occurred. Before and after images allowed the team to confirm eight of the craters. It’s possible that InSight recorded more impacts during its mission, and the team plans to continue digging through the data and looking for orbital evidence of fresh craters.
“Planetary impacts happen throughout the solar system all the time,” Daubar said. “We’re interested in studying this on Mars because then we can compare and contrast what’s happening on Mars with what’s happening on Earth.” This is important for understanding our solar system, what’s in it, and what the population of impactors looks like in our solar system – both as hazards to Earth and historically to other planets.
A companion paper published Friday in the journal Nature Communications also examined seismic events recorded by InSight to find that basketball-sized meteorites collide with Mars almost every day.
Between 280 and 360 meteoroids hit the red planet each year, and they form impact craters larger than 26 feet (8 meters), according to the study. Larger craters spanning 98 feet (30 meters) appear about once a month, the study authors said.
“This percentage is about five times higher than the number estimated from orbital imaging alone,” study co-author Dr. Géraldine Zenhäusern, professor of seismology and geodynamics at ETH Zürich in Switzerland, said in a statement. “Consistent with orbital imaging, our findings show that seismology is an excellent tool for measuring impact magnitude.”
By analyzing seismic events traced back to meteorites, the team has identified about 80 earthquakes recorded by InSight that may have been caused by impacts. Earthquakes as a result of collisions with meteorites occur with a higher frequency and have a shorter duration than other routes caused by underground activity.
“While the new craters can be seen best on flat and dusty terrain where they really stand out, this type of terrain covers less than half of the surface of Mars,” Zenhäusern said. “However, the sensitive InSight seismometer can hear every single shock within range of the landers.”
Seismic data of the smallest ground motions on Mars may be the most direct way to understand how many impacts occur on Mars, the researchers said.
“By using seismic data to better understand how often meteorites hit Mars and how these impacts change its surface, we can begin to piece together a timeline of the red planet’s geological history and evolution,” said study co-author Dr Natalia Wojcicka, a research associate in the Department of Science and Engineering at Imperial College London, said in a statement. “You could think of it as a sort of ‘cosmic clock’ to help us date Martian surfaces and perhaps, further down, other planets in the solar system.”
