Recent results from the InSight mission reveal that Mars experiences between 280 and 360 large meteorite impacts per year, far exceeding previous estimates based on satellite images. This seismic approach offers a new way to date the surfaces of Mars and other planets. Image source: NASA/JPL-Caltech
Seismic signals indicate Mars It is hit by about 300 basketball-sized meteorites every year, providing a new tool for dating planetary surfaces.
Scientists participating in NASANASA’s InSight mission has revealed that Mars experiences far more meteorite impacts than previously thought, with annual averages ranging from 280 to 360 major impacts. This new understanding stems from seismic data captured by InSight’s seismometer, suggesting a more efficient way to date the surfaces of planets throughout the solar system.
New research led by scientists at Imperial College London ETH Zurich As part of NASA’s InSight mission, it has highlighted how often “marsquakes” caused by meteorite impacts occur on Mars.
The researchers found that Mars experiences about 280 to 360 meteorite impacts every year, creating craters more than eight meters in diameter and shaking the surface of the Red Planet.
The rate of these Martian quakes, monitored by the InSight rover’s seismograph — an instrument capable of measuring the slightest ground motions — exceeds previous estimates based on satellite images of the Martian surface.
These craters were formed as a result of a meteorite colliding with Mars on September 5, 2021, and are the first craters to be observed by NASA’s InSight probe. Taken by NASA’s Mars Reconnaissance Orbiter, this color image highlights dust and soil disturbed by the impact in blue to make details more visible to the human eye. Copyright: NASA/JPL-Caltech/University of Arizona
Seismic data and planetary dating
The researchers say this seismic data could be a better, more direct way to measure meteorite impact rates, and could help scientists more accurately determine the age of planetary surfaces throughout the solar system.
“By using seismic data to better understand how often meteorite impacts Mars and how these impacts change its surface, we can begin to piece together a timeline of the geological history and evolution of the Red Planet,” said Dr Natalia Wojciech, a research associate in the Department of Earth Science and Engineering at Imperial College London and co-author of the study.
“You can think of it as a kind of ‘cosmic clock’ to help us date the surfaces of Mars and, perhaps, in the future, other planets in the solar system.”
The study was published today (June 28) in the journal Astronomy Nature.
A collage image shows three meteorite impacts that were first detected by a seismograph on NASA’s InSight lander and later captured by the agency’s Mars Reconnaissance Orbiter using the HiRISE camera. Copyright: NASA/JPL-Caltech/University of Arizona
Archaeological craters as cosmic clocks
For many years, scientists have used the number of craters on the surface of Mars and other planets as “cosmic clocks” to estimate the age of planets — older surfaces on planets were more cratered than younger ones.
To calculate the age of the planet in this way, scientists used models based on craters on the moon’s surface to predict the collision rate of meteorites of different sizes over time. To apply these models to Mars, they would have to be modified to account for how the atmosphere prevents the smallest objects from hitting the surface and the different size and location of Mars in the solar system.
For small craters less than 60 meters across, 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.
Artist’s rendering of the InSight lander operating on the surface of Mars. InSight, short for Interior Exploration Using Seismic Investigations, Geodesy and Heat Transfer, is a lander designed to perform the first comprehensive examination of Mars since its formation 4.5 billion years ago. Copyright: NASA/JPL-Caltech
Insights from InSight’s seismometer
In this new research, part of the InSight mission to understand seismic activity and the internal structure of Mars, researchers have identified a previously unknown pattern of seismic signals, as produced by meteorite impacts. These signals were characterized by their unusually larger proportion of high-frequency waves compared to typical seismic signals, among other characteristics, and were known as “very high-frequency” Martian earthquakes.
The researchers determined that the rate of meteorite impacts was higher than previously estimated by looking at newly formed craters captured by satellite images and consistent with extrapolating data from craters on the moon’s surface.
This highlights the limitations of previous models and estimates, as well as the need for better models for understanding 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 probe and its highly sensitive seismograph, SEIS, to record seismic events that may have been caused by meteorite impacts.
SEIS detected distinct seismic signatures of these high-frequency Martian earthquakes, which researchers found were indicative of meteorite impacts and distinct from other seismic activity.
Using this new method for detecting impacts, the researchers detected many more impact events than the satellite images predicted, especially for small impacts that produced craters just a few meters in diameter.
“SEIS has proven incredibly successful at detecting impacts – and it seems that listening to impacts is more effective than looking for them if we want to understand how often they occur,” said Professor Gareth Collins, a co-author of the study from the Department of Earth Science and Engineering at Imperial College London.
Improve our understanding of the solar system
Researchers believe that deploying smaller, more expensive seismometers on future landers could enhance our understanding of Mars’ impact rates and internal structure. These instruments will help researchers detect more seismic signals, providing 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 internal structure of planets, we use seismology. This is because when seismic waves travel through or reflect off material in a planet’s crust, mantle and core, they change. By studying these changes, seismologists can determine what material these layers are made of and how deep they are.
“On Earth, you can understand the internal structure of our planet more easily by looking at data from seismometers located all over the world. However, on Mars there was only one – SEIS. In order to better understand the internal structure of Mars, we need more seismometers distributed all over the planet.
In addition to new research published in Astronomy NatureThe team is also involved in another study published in Scientific progress Today, which used images and atmospheric signals recorded by InSight to estimate how often impacts occur on Mars. Despite using different methods, both studies reached similar conclusions, strengthening the overall findings.
Reference: “Estimating the impact rate on Mars from very high-frequency Martian earthquake statistics” June 28, 2024, Nature astronomy.
DOI: 10.1038/s41550-024-02301-z