A depiction of the inside of Mars. Image: Chris Bickel/Science
Researchers have turned their eyes to the composition of Mars by using seismic readings to understand what might lie beneath its surface.
Marsquakes were key to observations from NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander that will be published in three studies in Science tomorrow (23 July).
All of these studies made efforts to examine the composition of Mars. The research represents the first attempts to map the inside of a planet that isn’t Earth and measuring seismic waves was crucial to the research.
By studying the different layers of a planet, it is possible to garner insights into how the planet formed and evolved over billions of years. It can also help uncover the geomagnetic and tectonic activities of the planet.
The deep interior parts of a planet can be best accessed by measuring the waves that travel through the planet’s body following seismic events. These methods have been key in surveying internal characteristics here on Earth.
In 2019, InSight began to detect and record marsquakes from its position on the surface of Mars, including several subcrustal quakes that were like tectonic events on Earth.
Brigitte Knapmeyer-Endrun from the University of Cologne and colleagues used marsquakes and ambient seismic noise to image the structure of the Martian crust below the InSight landing site.
Their work found evidence of multiple layers, which they then extrapolated to the entire planet. Their paper concludes that the average thickness of Mars’ crust is somewhere between 24km and 72km.
A second research paper saw Amir Khan from ETH Zürich and his team use direct and surface-reflected seismic waves from eight different marsquakes to go deeper and show the structure of Mars’ mantle down to nearly 800km.
These findings suggest that a thick lithosphere is about 500km below the surface and, similar to Earth, it probably has a low-velocity layer beneath it. According to the paper, Mars’ crustal layer likely contains heat-producing radioactive elements that warm the region.
Meanwhile, Simon Stähler’s team used the faint seismic signals reflected off the Martian core-mantle boundary to investigate the very centre of the planet. They found that Mars’ liquid metal core has a radius of nearly 1,830km and begins about halfway between the surface and its centre.
According to researchers, the findings suggest that the iron-nickel core is less dense than previously thought and contains many lighter elements.
“Direct seismic observations on Mars represent a major leap forward in planetary seismology,” wrote Sanne Cottar and Paula Koelemijer in an article related to the research.
“Over the coming years, as more marsquakes are measured, scientists will refine these models of the Red Planet and reveal more of Mars’ enigmatic mysteries.”
