Recent Seismic Activity Points to a More Active Martian Geology

Similar to Earth’s earthquakes, Mars also experiences geological tremors, quaintly known as marsquakes. Now, new research from the Australian National University (ANU) and the Chinese Academy of Sciences in Beijing suggests that volcanic activity beneath the Martian surface could be responsible for repetitive marsquakes in the Cerberus Fossae region of Mars.  

Researchers have discovered 47 previously undetected marsquakes in this seismically active region of Mars. Cerberus Fossae is less than 20 million years old, making it one of the geologically younger areas of Mars.

Unlike Earth which has many seismic monitors located practically everywhere that can tell us about the internal structure of our planet, the interior of Mars is less well known. The Mars InSight mission recently motivated a number of studies regarding Mars’s internal structure, with the landing and setting of the first Martian seismograph, allowing scientists back on Earth to listen in to the rumbles on the red planet. 

The process of convection in the mantle (a subterranean region of molten rock and minerals often found in the terrestrial planets) of Mars is key to a magnetic field, which once existed globally but no longer exists. On Earth, for example, it is the dynamic movement of the outer core that generates our planetary magnetic field, which protects our atmosphere and in turn allows life to evolve safely on the surface. One outstanding question about Mars’s internal structure and processes considers if there is still convection happening in the Martian mantle or if this stopped sometime in the past.

“In a way, it is good news to the geologists and other planetary scientists that the Martian mantle is mobile. More seismic activity means that we have more quakes to use in imaging the interior of Mars, in the same way, we do down on Earth. It also means that the convection in the Martian liquid core is more likely to occur, however, the Martian dynamo died a while ago, and we know that its core is not convecting. One reason for this could be that the liquid layer of the Martian outer core is too thin to produce any sizeable dynamo. Another reason could be that its liquid core is stratified due to its chemical composition, and this killed the convection at some stage in the Martian past, and with it, the magnetic field of Mars.” said Professor Hrvoje Tkalčić, geophysicist and co-author from the ANU Research School of Earth Sciences.

The findings of this recent study suggest that the Martian mantle is still active and responsible for the marsquakes experienced in Cerberus Fossae. This is contrary to previous beliefs held by scientists that these events have been caused by tectonic forces.

The repetitive nature of the quakes combined with the fact that they were all from the same region of Mars suggests that the red planet is more seismically active than previously thought.

“We found that these marsquakes repeatedly occurred at all times of the Martian day, whereas marsquakes detected and reported by NASA in the past appeared to have occurred only during the dead of night when the planet is quieter,” said Professor Tkalčić.

“Therefore, we can assume that the movement of molten rock in the Martian mantle is the trigger for these 47 newly detected marsquakes beneath the Cerberus Fossae region.”

There are also many other processes on Mars that may cause quakes.

“They could be caused by both tectonic and volcanic processes. However, the temperature variations at the Martian surface are quite extreme, up to about -20 degrees Celsius during the Martian day, and less than -100 degrees Celsius during the Martian nights, so these extreme thermal changes could cause Martian rocks to contract and expand, and as a consequence, crack and produce marsquakes. Tidal forces of Phobos and Deimos also cause tiny variations in the stress field of the Martian rocks, and that could also contribute to the quakes. Meteorite impacts can cause quakes, and last but not least, there are all sorts of phenomena in the Martian atmosphere that could be responsible for signals that we observe on the InSight seismometer, SEIS.” said  Professor Tkalčić.

Professor Tkalčić indicated that the continuous seismic activity suggests that the Cerberus Fossae region on Mars is “seismically highly active”.

“Knowing that the Martian mantle is still active is crucial to our understanding of how Mars evolved as a planet,” said Professor Tkalčić.

“It can help us answer fundamental questions about the solar system and the state of Mars’ core, mantle and the evolution of its currently-lacking magnetic field.”

The data used for this study was collected from the seismometer attached to NASA’s InSight lander, which has been collecting data about marsquakes, Martian weather, and the planet’s interior since landing on Mars in 2018.

The researchers used a unique algorithm and applied this to NASA’s data in order to detect the 47 previously undiscovered marsquakes.

The authors of the study say that while the quakes would have caused some shaking on Mars, the seismic events were relatively small in magnitude and would have barely been felt on Earth. The quakes were detected over a period of 350 sols, which is equivalent to about 359 Earth days.

According to Professor Tkalčić, these findings could help scientists figure out why Mars no longer has a magnetic field. There are also implications for further constraining the habitability time period of Mars, as well as giving insight into the planetary evolution and geological processes of Mars.

“If it can be confirmed that the Martian mantle is mobile, this will inform scientists who are investigating the Martian paleomagnetic field and the habitability time period. When the convection in the Martian liquid core died and with it its dynamo that generates the magnetic field, that had catastrophic consequences for the potential life, as the magnetic field protects planets from deadly cosmic radiation. This puts our own magnetic field and the long-lived geodynamo on Earth in a cosmic perspective. Luckily, the conditions during the Earth’s differentiation were different; not just due to the Earth’s size, but also due to the fact that the mixture of light elements that existed in the Earth’s core as a result of the differentiation process, favoured and sustained vigorous convection.” said Professor Tkalčić.

“The marsquakes indirectly help us understand whether convection is occurring inside of the planet’s interior, and if this convection is happening, which it looks like it is based on our findings, then there must be another mechanism at play that is preventing a magnetic field from developing on Mars,” he said.

 “All life on Earth is possible because of the Earth’s magnetic field and its ability to shield us from cosmic radiation, so without a magnetic field life as we know it simply wouldn’t be possible.

 “Therefore, understanding Mars’ magnetic field, how it evolved, and at which stage of the planet’s history it stopped is obviously important for future missions and is critical if scientists one day hope to establish human life on Mars.”