A global team of scientists has found the reason behind the biggest Martian seismic event, or Marsquake, observed by NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) Mars lander. After ruling out a meteor impact, they concluded the event will need to have been brought on by a release of stress throughout the planet’s crust.
The forceful quake occurred on May 4, 2022, at 23:23 UTC, on the 1222nd Martian day, or sol, of InSight’s mission. The quake, also generally known as S1222a, was five times stronger than any event InSight had observed before. It shook the planet at a magnitude of 4.7 and the vibrations reverberated through Mars’ crust for roughly six hours.
The event showed similarities with earlier Martian seismic events, which have since been identified as meteor impacts, so scientists scoured the Martian surface for a possible impact crater. To do that, the team used observations from missions currently in orbit around Mars, engaging in a world collaboration between the European Space Agency (ESA), the Chinese National Space Agency, the Indian Space Research Organisation, and the United Arab Emirates Space Agency (UAESA).
“This project represents an enormous international effort to assist solve the mystery of S1222a, and I’m incredibly grateful to all of the missions who contributed,” said study lead Benjamin Fernando of the University of Oxford. “I hope this project serves as a template for productive international collaborations in deep space.”
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/10/Picture1.jpg)
The world that was imaged within the seek for a possible impact crater. The yellow star shows S1222a’s expected epicenter and the yellow rectangle is the first search area. A, B, and C show the observations and D shows the probability map for the event’s epicenter. (Credit: Fernando et al.)
For the biggest meteor impacts detected by InSight, scientists found craters with a diameter of as much as 150 meters. If S1222a was also brought on by a meteor impact, the team expected to seek out a crater with a diameter of 300 meters and a blast zone that might be 180 kilometers across. Each contributing team searched for this potential crater using their spacecraft, comparing observations from before and after the Marsquake.
“We’re willing to collaborate with scientists world wide to share and apply this scientific data to get more knowledge about Mars, and are proud to have provided data from the colour imagers on Tianwen-1 to contribute to this effort,” said Jianjun Liu of Chinese Academy of Sciences.
But why did the team need observations from this many satellites?
“Making the association between a given seismic event and a fresh crater is difficult,” the scientists wrote. They will discover fresh craters by the presence of a blast zone, which fades over time but is simple to identify on lower-resolution images taken shortly after the impact. Depending on the impact terrain, nevertheless, blast zones may be obscured or less prevalent, so the team still needed high-resolution images to exclude the potential for an impact.
One other challenge is the low availability of high-resolution images from spacecraft in orbit. The high-resolution cameras on the satellites have narrow fields of view and may only observe small areas at one time. For this reason, the region may not have been imaged before the impact, making it unattainable for the teams to check before and after photos within the seek for a fresh crater.
NEW: A world team of scientists have confirmed the outcomes of a seek for the source of the largest-ever seismic event recorded on Mars.
The study suggests the quake was the results of enormous tectonic forces inside Mars’ crust.https://t.co/wuXo9T0W9v
— University of Oxford (@UniofOxford) October 18, 2023
To beat these hurdles, the scientists had to have a look at the combined output of all current missions in orbit around Mars.
“This experiment shows how essential it’s to keep up a various set of instruments at Mars, and we’re very glad to have played our part in completing the multi-instrumental and international approach of this study,” said Daniela Tirsch, Science Coordinator for the High-Resolution Stereo Camera onboard ESA’s Mars Express Spacecraft.
With all observations combined, the team found no evidence of an impact crater that would explain the measured seismic event and concluded that the Marsquake must thus have been a tectonic event within the planet’s own crust.
“We still think that Mars doesn’t have any energetic plate tectonics today, so this event was likely brought on by the discharge of stress inside Mars’ crust,” said Fernando “These stresses are the results of billions of years of evolution; including the cooling and shrinking of various parts of the planet at different rates.”
This Marsquake’s epicenter was positioned 2,200 kilometers from InSight, but well outside the Cerberus Fossae region which is thought for its tectonic activity.
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/10/Picture2.jpg)
Map showing InSight’s location (red triangle), the situation of S1222a’s expected epicenter (blue dot) and probability ellipse (blue), Cerberus Fossae (black lines) and the locations of other seismic events (purple dots). (Credit: Kawamura et al. (2023))
“We still don’t fully understand why some parts of the planet appear to have higher stresses than others, but results like these help us to analyze further,” said Fernando. “At some point, this information may help us to know where it could be protected for humans to survive Mars and where it is advisable to avoid!”
The S1222a quake occurred near the tip of InSight’s mission. By that point, a number of the lander’s sensors were turned off to conserve power as dust had begun accumulating on its solar panels, reducing the lander’s available power to lower than 20% of the unique capability. For this reason, Fernando’s team was limited to using seismic data, as no measurements of atmospheric pressure and wind were recorded.
InSight was launched on May 5, 2018, by the United Launch Alliance atop its Atlas V 401 rocket from Vandenberg Air Force Base in California. The mission landed in Mars’s Elysium Planitia region on Nov. 26, 2018. When NASA retired the lander in December 2022, it had detected 1,319 Marsquakes. Currently, scientists are continuing to research InSight’s data even after the mission ended.
“This has been an incredible opportunity for me to collaborate with the InSight team, in addition to with individuals from other major missions dedicated to the study of Mars,” said Dimitra Atri of Recent York University Abu Dhabi, who contributed data from UAESA’s Hope Spacecraft. “This really is the golden age of Mars exploration!”
Fernando et al.’s study was published in Geophysical Research Letters on Oct. 17, 2023.
(Lead image: Illustration showing InSight on the Martian surface. Credit: NASA/JPL-Caltech)