In March, NASA’s InSight lander felt the distant rumble of two large “Marsquakes” from a region known as Cerberus Fossae near the Martian equator. With quakes of 3.1 and 3.3 on March 7th and 18th, the quakes cement the reputation of Cerberus Fossae as one of the most geologically active places on the Red Planet. A pair of similarly strong Marsquakes shook the same region in 2019.
The Cerberus Fossae region is marked by a series of massive, nearly parallel fissures that arise when the planet’s crust is torn open by a dramatic volcanic event. Volcanism is the main driver of quakes on Mars: the red planet lacks the tectonic plates that cause most of the quakes that we feel here on earth.
On Mars, the Cerberus Fossae region is one of the major epicentres of such activity and a fascinating area of study in both the past and the present due to its geological instability.
The Cerberus Fossae cracks are clearly visible in the dark area in the center left of this mosaic from Viking Orbiter 1. Photo credit: NASA (Wikimedia Commons).
Our ability to detect marsquakes is very new. Geologists have suspected its existence for decades, but it wasn’t until InSight launched its Internal Structure Seismic Experiment (SEIS) in early 2019 that scientists were able to capture a record of one indisputably. The Viking 2 Lander observed an event in 1976 that may have been a small quake, but at that point it was impossible to rule out wind or weather as the cause. InSight, on the other hand, has found hard evidence of over five hundred seismic events in the past two years. Most of the marsquakes detected by SEIS were small, but those that originated from the Cerberus Fossae are some of the clearest and strongest ever.
Landslides in the Cerberus Fossae, indicating recent (geological) seismic activity. Photo credit: NASA / JPL-Caltech / Univ. from Arizona
Incredibly, geologists predicted that InSight could hear quakes from the Cerberus Fossae region six years before the spacecraft landed on Mars. As early as 2012, a team of researchers examined the area using images captured with the HiRISE camera of the Mars Reconnaissance Orbiter and discovered evidence of recent landslides and boulders that had rolled down the steep slopes of some chasms. These rockfalls appeared to coincide with the aftermath of earthquakes here at home, suggesting that a marsquake may have occurred recently. InSight’s new discoveries confirm this theory.
The InSight mission was extended by two years in January. During this time, the team hopes to get a detailed record of Mars seismic activity. To ensure the highest possible data quality, they started using the lander’s robotic arm to bury the SEIS instrument cable. In this way, wind noise, vibrations and temperature fluctuations are reduced, which can disrupt the seismometer and mask possible Marsquake detections.
InSight’s robotic arm shovels earth to bury the seismometer’s line. The picture was taken on April 3, 2021. Photo credit: NASA / JPL-Caltech
InSight is also still having issues with dust-covered solar panels, which means some instruments on the lander, like the weather station, need to be temporarily turned off. Insight still has enough energy to keep SEIS running for another month or two. After that, SEIS must also go into hibernation. This low-powered state will persist until a dust devil cleans the panels or until Mars approaches the Sun in its orbit, which should happen shortly after July.
In the meantime, the researchers are excited about the discoveries of the Cerberus Fossae and hope that even stronger quakes will occur. When InSight hears a “big one,” the vibrations can be deep enough to interact with the planet’s mantle and core. By listening to an event like this, we learn more about the internal structure of the planet – something we currently know very little about.
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