Meteorite Chaos: How NASA InSight’s Seismic Data Is Rewriting Mars’ History

Seismic signals indicate Mars is hit by about 300 basketball-sized meteorites each year, providing a new tool for dating planetary surfaces.

Scientists involved in NASA‘s InSight mission has found that Mars is exposed to many more meteorite impacts than previously thought, with annual numbers ranging from 280 to 360 significant impacts. This new insight comes from seismic data collected by InSight’s seismometer, suggesting a more effective method for dating planetary surfaces across the solar system.

The new research, led by scientists from Imperial College London and ETH Zurich, part of NASA’s InSight mission, have provided insight into how often ‘marsquakes’ caused by meteorite impacts occur on Mars.

The researchers found that Mars experiences between 280 and 360 meteorite impacts each year, creating craters over eight meters in diameter and shaking the surface of the red planet.

The frequency of these Martian quakes, which were detected by InSight’s seismometer – an instrument that can measure the smallest ground movements – exceeds previous estimates based on satellite images of the Martian surface.

Seismic data and planetary dating

The researchers say this seismic data could provide a better, more direct way to measure the speed of meteorite impacts, and help scientists more accurately date planetary surfaces across the solar system.

Co-first author of the study Dr. Natalia Wojcicka, research associate at the Department of Earth Science and Engineering at Imperial College London, said: “By using seismic data to better understand how often meteorites hit Mars and how these impacts change the surface, we can start to piece together a timeline of the red planet’s geological history and evolution.

“You could think of it as a kind of ‘cosmic clock’ that helps us date the surfaces of Mars, and perhaps later other planets in the solar system.”

The study is published today (June 28) in the journal Nature Astronomy.

Impact craters like cosmic clocks

For years, scientists have used the number of craters on the surfaces of Mars and other planets as ‘cosmic clocks’ to estimate the age of planets – with older surfaces on planets containing more craters than younger ones.

To calculate planetary ages this way, scientists have traditionally used models based on craters on the moon to predict the rates of meteorite impacts of various sizes over time. To apply these models to Mars, they must be adjusted for how the atmosphere can keep the smallest impacts from hitting the surface and for Mars’s different size and position in the solar system.

For small craters less than 60 meters wide, Mars scientists have also been able to observe how often new craters form using satellite images – but the number of craters found this way is much lower than expected.

Insights from InSight’s seismometer

In this new research, part of the InSight mission to understand the seismic activity and internal structure of Mars, researchers identified a previously unrecognized pattern of seismic signals, such as those produced by meteorite impacts. These signals were notable for their unusually higher proportion of high-frequency waves compared to typical seismic signals, as well as other characteristics, and are known as “very high-frequency” marsquakes.

The researchers found that the rate of meteoroid impacts was higher than previously estimated by looking at freshly formed craters captured by satellite images and consistent with extrapolating data from craters on the moon’s surface.

This highlighted the limitations of previous models and estimates, as well as the need for better models to understand crater formation and meteorite impacts on Mars.

The power of seismic data in planetary science

To address this problem, the team of scientists used NASA’s InSight lander and the extremely sensitive SEIS seismometer to record seismic events possibly caused by meteorite impacts.

SEIS detected seismic signatures characteristic of these very high-frequency Marsquakes, which researchers found were indicative of meteoroid impacts and distinct from other seismic activities.

Using this new method of detecting impacts, the researchers discovered many more impacts than predicted from satellite images. This was especially true for small impacts that created craters only a few meters in size.

Co-author of the study, Professor Gareth Collins from Imperial College London’s Department of Earth Science and Engineering, said: “The SEIS instrument has proven to be incredibly successful at detecting impacts. Listening for impacts appears to be more effective than looking for them if we want to understand how often they occur.”

Improving our understanding of the solar system

Researchers believe that deploying smaller, more affordable seismometers on future landers could further increase our understanding of the impact rates and internal structure of Mars. These instruments would help researchers detect more seismic signals, creating a more comprehensive dataset for understanding meteorite impacts on Mars and other planets, as well as their internal structures.

Dr Wojcicka said: “To understand the inner structure of planets, we use seismology. This is because seismic waves change as they travel through or reflect off the crust, mantle and core of planets. By studying these changes, seismologists can determine what these layers are made of and how deep they are.

“On Earth, it’s easier to understand the internal structure of our planet by looking at data from seismometers placed all over the world. But on Mars, there’s only been one: SEIS. To better understand the internal structure of Mars, we need more seismometers, spread across the planet.”

In addition to the new research published in Nature Astronomythe team is also involved in another study to be published in Scientific progress today, using images and atmospheric signals recorded by InSight to estimate how often impacts occur on Mars. Despite using different methods, both studies reached similar conclusions, reinforcing the overall findings.

Reference: “An estimate of the impact velocity on Mars from statistics of very high frequency Marsquakes” June 28, 2024, Nature Astronomy.
DOI: 10.1038/s41550-024-02301-z