by Meteorites impact Mars at a rate up to 10 times more frequent than previously estimated, according to two new research papers that identified the seismic shock waves of these impacts detected by NASA’s InSight Mars Lander which is now obsolete.
The new rate is emerging. According to the results, between 180 and 260 impacts occur per year on the Red Planet, and these objects can get at least as big as a basketball, getting an eight-meter (26-foot) crater in the ground. Overall, the impact rate is between two and 10 times higher than predicted, depending on the size of the impactor. And some of the new impacts detected by InSight were large: For example, one of the studies reports two major impacts, occurring 97 days apart, that were significant enough to excavate a crater the size of a football field.
“An impact of this size, we would expect to happen maybe once every few decades, maybe even once in a lifetime, but here are two of them that are just over 90 days apart,” Ingrid Dauber Brown University, who led one of the studies, said in a statement.
Dauber doubts that these impacts are just a coincidence, and suggests that it is more likely that the direct impact rate of Mars is generally higher than planetary scientists have realized.
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Both studies used the seismometer instrument, SEIS, on InSight (Interior Exploration using Seismic, Geodesy and Thermal Investigations) to detect the impacts. InSight recorded seismic data for four years, during which SEIS was present active on the surface of Mars (between December 2018 and December 2022). It’s not easy to tease out the seismic shock of all the other seismic movements within the Red Planet, so Dauber’s team compared the seismic data with images of a similar new crater seen from orbit by NASA. Mars Exploration Orbit (MRO) to link the tremors to actual impacts.
From the MRO images, Dauber’s team identified eight new impact craters that created “big quakes: detected by SEIS. Six of these craters were in the area around InSight’s landing site in Elysium Planitia. The two larger impacts that were 97 days apart created a more distant crater. These two events are the largest fresh impacts seen on Mars in modern history 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 collisions occur each year based on SEIS data alone. However, the estimated impact rate in each paper, calculated independently of each other using slightly different methods, is consistent with each other, which adds to the validity of the results.
Detecting impacts in this way is an important new capability because, previously, planetary scientists could only find new impacts by comparing images of the Martian surface and later from orbit and seeing if any new craters were visible. This was, as you can imagine, very inefficient. Seismic data adds a new dimension to efforts to measure these impacts. In addition, the results also have ramifications that may trickle down during our study of all the other solid bodies in our Solar system.
Planetary surfaces do not come with an acknowledgment of how long ago they formed, or when they were last covered in lava. Instead, scientists must calculate surface ages based on how many craters cover those surfaces; the more craters there are, the older the surface. We can see a classic example of this on our moon. The ancient lunar highlands, which are about as old as the moon itself, are filled with craters, but the lunar core, which is volcanic plains up to a billion years younger, has far fewer craters.
However, being able to update planetary surfaces depends on scientists having an accurate handle on impact rates, and the new data from Mars suggests, however, that they may not. If the impact rate on Mars is higher than we thought, some planetary surfaces may be younger than previously determined, as they may have accreted their craters over a shorter period of time.
“By using seismic data to better understand how often meteorites hit Mars and how these impacts change its surface, we can begin to build a timeline of the geological history and evolution of the Red Planet put together,” Wojcicka said in a statement. “You could think of it as a kind of ‘cosmic clock’ to help us date Martian surfaces and, perhaps further down the line, other planets in the solar system.”
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Dauber goes further, saying that the higher impact rate not only has implications for the age and evolution of [Mars’] surface,” but that “This will require us to rethink some of the models used by the scientific community to estimate the age of planetary surfaces throughout the entire solar system.”
Dauber’s team published their findings on June 28 in the journal Scientific Progressand Wojcicka’s team’s results were published in the journal at the same time Natural Astronomy.
