Meteorite impacts on Mars are up to 10 times more common than previously estimated, according to two new research papers. These describe the seismic shock waves from these impacts, which were detected by NASA’s now defunct Mars InSight lander.
The new rate is staggering. The findings suggest that between 180 and 260 impacts occur on the Red Planet each year, and these objects can be at least as large as basketballs, leaving eight-meter (26-foot) craters in the ground. Overall, the impact rate is two to 10 times higher than predicted, depending on the size of the impact. And some of the new impacts detected by InSight were large: One study, for example, reported two large impacts, occurring 97 days apart, that were significant enough to each carve out a crater the size of a football field.
“We would expect an impact like this to happen maybe once every few decades, maybe even once in a lifetime, but here we have two just over 90 days apart,” said Ingrid Dauber of Brown University, who is a of the studies led, in one rack.
Dauber is skeptical and does not think these impacts are mere coincidence. He suggests that it is more likely that the impact frequency on Mars is simply higher than planetary scientists realized.
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Both studies used the seismometer instrument SEIS (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) on InSight to detect the impact. InSight recorded seismic data for four years, during which time SEIS active on the surface of Mars (between December 2018 and December 2022). It’s not easy to distinguish the seismic shock wave from an impact from all the other seismic movements within the Red Planet, so Dauber’s team compared the seismic data with images of apparently new craters seen from orbit by NASA’s Mars exploration orbiter (MRO) to connect the vibrations to actual shocks.
From the MRO images, Dauber’s team identified eight new impact craters that had produced “marsquakes” detected by SEIS. Six of these craters were in the vicinity of InSight’s landing site in Elysium Planitia. The two larger impacts, 97 days apart, formed craters further away. These two events are the largest new impacts to ever occur on Mars in the history of our planet. robotic exploration of the Red Planet.
The second study, led by Natalia Wojcicka of Imperial College London, suggests that between 280 and 360 basketball-sized impactors occur each year, based solely on SEIS data. However, the estimated impact rate in each article, calculated independently using slightly different methods, confirms each other, adding to the veracity of the results.
Detecting impacts in this way is an important new capability, because previously planetary scientists could only find new impacts by comparing before and after images of the Martian surface from orbit and seeing if new craters had formed. This was, as you can imagine, very inefficient. Seismic data adds a new dimension to efforts to measure these impacts. Moreover, the findings also have implications that could trickle down to our studies of all other solid bodies in our solar system.
Planetary surfaces don’t come with a receipt telling them how long ago they formed, or when they were last covered in lava. Instead, scientists must calculate the age of the surface based on the number of craters that cover those surfaces; the more craters there are, the older the surface must be. We can see a classic example of this in our moon. The ancient lunar highlands, which are about as old as the moon itself, are riddled with craters, while the lunar mare, volcanic plains that are up to a billion years younger, have far fewer craters.
However, being able to date planetary surfaces depends on scientists having an accurate understanding of impact rates, and the new data from Mars suggests that may not be the case. If Mars’ impact rate is higher than we thought, some planetary surfaces could be younger than previously determined because their craters could have formed in a shorter time period.
“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,” Wojcicka 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.”
Dauber goes further and says that the higher impact rate not only has implications for the age and evolution of [Mars’] surface,” but that “this requires us to reconsider some of the models that the scientific community uses to estimate the ages of planetary surfaces throughout the solar system.”
Dauber’s team published their findings June 28 in the journal Scientific progresswhile Wojcicka’s team’s findings were simultaneously published in the journal Nature Astronomy.