“The Big One”: The Most Powerful Marsquake Ever Detected
A new paper explains how the largest recorded seismic event on Mars provided evidence for the release of stress within the Martian crust.
The ground shakes. Paintings tilt. Walls crack. Rubble may fall. On Earth, we understand how and where these events happen due to the discovery of plate tectonics — the continental crust’s creation, movement, and destruction. However, when astronauts placed seismometers on the lunar surface during NASA’s Apollo mission era, those instruments recorded quakes on the Moon. In the 1970s, the Viking landers also recorded quakes on the surface of Mars. Since neither of these worlds has plate tectonics, scientists set about collecting more data to understand the phenomena, which led to the recent NASA InSight lander. Now, a new paper in Geophysical Research Letters explains how the largest recorded seismic event on Mars provided evidence for a different sort of tectonic origin — the release of stress within the Martian crust.
On Wednesday, May 4, 2022, InSight recorded a record-breaking magnitude 4.7 marsquake with an epicenter about 2,200 kilometers away from the lander. The resulting tremors shook the planet for the next six hours. The event was large, but scientists had no reason to believe the cause was anything different from the usual meteoroid impact. After all, InSight had recorded no fewer than eight impact-related quakes, the two largest of which resulted in separate craters about 150 meters in diameter. This new event — cataloged as S1222a — generated a quake energetic enough for the resulting crater to be on the order of 300 meters in diameter with a potential blast zone nearly 200 kilometers wide.
All three events had several similarities, including long-period surface waves. There were, however, differences in the wave data types collected. Lead author Benjamin Fernando from the University of Oxford still suspected an impact as the cause of S1222a. He gathered up a team to find the crater, requesting help from a number of organizations, including the European Space Agency, the…