Researchers gained new insights into Mars’ liquid core, discovering that it is slightly denser and smaller than previously believed, and contains a mixture of iron and other elements. The findings, obtained through the first-ever detections of seismic waves on the Martian core, contribute to our understanding of the planet’s formation and evolution.
Lead author Dr. Jessica Irving, Senior Lecturer in Earth Sciences at the University of Bristol, stated: “The extra mission time certainly paid off. We’ve made the very first observations of seismic waves traveling through the core of Mars. Two seismic signals, one from a very distant marsquake and one from a meteorite impact on the far side of the planet, have allowed us to probe the Martian core with seismic waves. We’ve effectively been listening for energy traveling through the heart of another planet, and now we’ve heard it.”
The research team used data from NASA’s InSight lander, a robotic spacecraft designed to probe the interior of Mars, to compare seismic waves traveling through the planet’s core with those traversing its shallower regions and model properties of its interior.
The InSight lander deployed a broadband seismometer on the Martian surface in 2018, allowing for the detection of seismic events, including marsquakes and meteorite impacts. The multidisciplinary team of scientists, including seismologists, geodynamacists, and mineral physicists, used observations of two seismic events located in the opposite hemisphere from the seismometer to measure the travel times of seismic waves that passed through the core relative to seismic waves that remained in the mantle.
The authors used these measurements to build models describing physical properties of the core, including its size and elastic wave-speed. The results suggested Mars’ core is slightly denser and smaller than previous estimates, with a radius of approximately 1,780–1,810 km. These findings are consistent with the core having a relatively high fraction of light elements alloyed with iron, including abundant sulfur and smaller amounts of oxygen, carbon, and hydrogen.
Co-author Ved Lekic, Associate Professor of Geology at the University of Maryland College Park, stated: “Detecting and understanding waves that travel through the very core of another planet is incredibly challenging, reflecting decades of efforts by hundreds of scientists and engineers from multiple countries. We not only had to utilize sophisticated seismic analysis techniques but also deploy knowledge of how high pressures and temperatures affect properties of metal alloys, leveraging the expertise of the InSight Team.”
Dr. Irving added: “The new results are important for understanding how Mars’ formation and evolution differ from those of Earth. New theories about the formation conditions and building blocks of the red planet will need to be able to match the core’s physical properties as revealed by this new study.”
Dr. Jessica Irving and co-author Dr. Anna Horleston, a seismologist from the University of Bristol, were supported with funding from the UK Space Agency.
Reference: “First observations of core-transiting seismic phases on Mars” 24 April 2023, Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2217090120. This research was supported by NASA (Grant Nos. 80NSSC18K1628 and 80NSSC19M0216) and the SSERVI Cooperative Agreement. This story does not necessarily reflect the views of these organizations.
