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Hundreds of basketball-sized space rocks hit Mars every year, according to new research. They leave impact craters and cause rumblings on the red planet.
Mission planners can use the revelations, captured in data collected by a now-abandoned NASA mission, to help determine landing sites for future robotic missions and astronaut crews on the Red Planet.
NASA’s InSight mission ended when the stationary lander lost a battle in December 2022 due to a buildup of Martian dust on its solar panels, but the wealth of data the spacecraft collected is still fueling new research.
The lander delivered the first seismometer to Mars, and the sensitive instrument could detect seismic waves thousands of miles away from InSight’s location in Elysium Planitia, a smooth plain just north of the planet’s equator.
During its stay on Mars, InSight used its seismometer to detect more than 1,300 marsquakes, which occur when the Martian subsurface cracks due to pressure and heat.
But InSight also captured evidence of meteorites hitting Mars.
Meteoroids are space rocks that have broken off from larger rocky bodies and range in size from dust particles to small asteroids, according to NASA. They are known as meteoroids while they are still in space, and are called meteors as they streak through the atmosphere of Earth or other planets.
Scientists have wondered why more impacts haven’t been observed on Mars, since the planet is located next to our solar system’s main asteroid belt, where many space rocks emerge and hit the Martian surface. Mars’ atmosphere is only 1% the thickness of Earth’s atmosphere, meaning more meteoroids fly through it without breaking up.
A meteoroid struck the Martian atmosphere on September 5, 2021, before exploding into at least three shards, each leaving a crater on the red planet’s surface. And it was just the beginning.
Since 2021, researchers have studied InSight data and found that space rocks bombard Mars more often than previously thought. According to a new study published Friday in the journal Science Advances, space rocks are two to 10 times more common than previously thought.
“It’s possible that Mars is more geologically active than we thought, which has implications for the age and evolution of the planet’s surface,” lead study author Ingrid Daubar, an associate professor of earth, environmental, and planetary sciences at Brown University, said in a statement. “Our results are based on a small number of available samples, but the estimate of the current impact rate suggests the planet is being hit much more frequently than we can tell with imaging alone.”
The team identified eight new impact craters created by meteorites based on InSight data, which orbiters orbiting the planet had previously spotted. Six of the craters were near InSight’s landing site, and two of the distant impacts were among the largest ever detected by scientists observing the red planet, the study said.
Both major impacts left craters the size of a football field and occurred 97 days apart.
“We expect this magnitude to happen once every few decades, maybe even once in a lifetime, but here we have two just over 90 days apart,” Daubar said. “It could just be a crazy coincidence, but the chances of it being just a coincidence are very slim. What is more likely is that either the two major impacts are related, or the impact rate for Mars is much higher than we thought.”
The team compared the data collected by InSight with that of 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 sifting through the data and looking for evidence of fresh craters in orbit.
“Planetary impacts are happening all the time throughout the solar system,” Daubar said. “We’re interested in studying that on Mars because 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 is in it, and what the impactor population in our solar system looks like – both as a hazard 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 determine that basketball-sized meteoroids crash onto Mars almost daily.
According to the study, between 280 and 360 meteorites hit the red planet each year, forming impact craters larger than 26 feet (8 meters) in diameter. Larger craters that span 98 feet (30 meters) occur about once a month, the study authors said.
“This rate was approximately five times higher than the number estimated from orbital images alone,” said co-lead study author Dr. Géraldine Zenhäusern, professor of seismology and geodynamics at Switzerland’s ETH Zurich, said in a statement. “In line with orbital images, our findings demonstrate that seismology is an excellent tool for measuring impact rates.”
By analyzing seismic events traced to meteoroids, the team identified approximately 80 InSight-recorded Marsquakes that may have been caused by impacts. The Martian earthquakes caused by meteoroid impacts occur with a higher frequency and last for a shorter period than other quakes caused by underground activity.
“Although new craters are best seen 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 was able to hear every single impact within range of the landers.”
According to the researchers, seismic data from the tiniest ground motions on Mars could provide the most direct way to understand exactly how many impacts occur on Mars.
“By using seismic data to better understand how often meteorites hit Mars and how these impacts alter the surface, we can piece together a timeline of the red planet’s geological history and evolution,” said study co-lead author Dr. Natalia Wojcicka, research associate in the department of earth sciences and engineering at Imperial College London, said in a statement. “You could think of it as a kind of ‘cosmic clock’ to help us date the surfaces of Mars, and perhaps, later, other planets in the solar system.”