Seismic waves traveling through the Martian core would provide valuable new information about the planet’s interior. Because seismic waves can reveal information about the density, composition, and temperature of the material they pass through, analyzing them could aid scientists in better understanding the structure of Mars’ core and how it has evolved over time.
According to new NASA InSight research, Mars has a liquid core rich in sulfur and oxygen, providing new insights into how terrestrial planets form, evolve, and potentially sustain life. For the first time, scientists observed seismic waves traveling through Mars’ core, confirming model predictions of the core’s composition.
An international research team, including seismologists from the University of Maryland, used seismic data collected by the NASA InSight lander to directly measure properties of Mars’ core, discovering a completely liquid iron-alloy core with high percentages of sulfur and oxygen. These findings, published in the Proceedings of the National Academy of Sciences, provide new insights into how Mars formed as well as geological differences between Earth and Mars that may eventually play a role in sustaining planetary habitability.
“In 1906, scientists first discovered the Earth’s core by observing how seismic waves from earthquakes were affected by traveling through it,” said UMD Associate Professor of Geology Vedran Lekic, second author of the paper. “More than a hundred years later, we’re applying our knowledge of seismic waves to Mars. With InSight, we’re finally discovering what’s at the center of Mars and what makes Mars so similar yet distinct from Earth.”
This was a huge effort, involving cutting-edge seismological techniques honed on Earth, as well as new results from mineral physicists and insights from team members who simulate how planetary interiors change over time.
Jessica Irving
The team tracked the progression of two distant seismic events on Mars, one caused by a marsquake and the other by a large impact, and detected waves that traveled through the planet’s core to determine these differences. The team estimated the density and compressibility of the material the waves traveled through by comparing the time it took those waves to travel through Mars to waves that stayed in the mantle and combining this information with other seismic and geophysical measurements. According to the researchers’ findings, Mars most likely has a completely liquid core, as opposed to Earth’s combination of a liquid outer core and a solid inner core.
The team also deduced details about the core’s chemical composition, such as the surprisingly large amount of light elements (elements with low atomic numbers) – specifically sulfur and oxygen – present in Mars’ innermost layer. According to the team’s findings, those elements account for one-fifth of the core’s weight. This high percentage contrasts sharply with the comparatively lower weight proportion of light elements in Earth’s core, indicating that Mars’ core is far less dense and compressible than Earth’s core, indicating that the two planets formed under very different conditions.
“You can think of it this way; the properties of a planet’s core can serve as a summary about how the planet formed and how it evolved dynamically over time. The end result of the formation and evolution processes can be either the generation or absence of life-sustaining conditions,” explained UMD Associate Professor of Geology Nicholas Schmerr, another co-author of the paper. “The uniqueness of Earth’s core allows it to generate a magnetic field that protects us from solar winds, allowing us to keep water. Mars’ core does not generate this protective shield, and so the planet’s surface conditions are hostile to life.”
Although Mars currently lacks a magnetic field, scientists believe that traces of magnetism in Mars’ crust once provided a magnetic shield similar to Earth’s core-generated field. According to Lekic and Schmerr, this could imply that Mars gradually evolved to its current state, transitioning from a potentially habitable planet to an extremely hostile one. According to the researchers, interior conditions, as well as violent impacts, may play a role in this evolution.
“It’s kind of like a puzzle in some ways,” Lekic said. “For instance, there are trace amounts of hydrogen in Mars’ core. That means certain conditions had to exist for the hydrogen to exist, and we need to understand those conditions to understand how Mars evolved into the planet it is today.”
The findings of the team ultimately confirmed the accuracy of current modeling estimates aimed at uncovering the layers hidden beneath a planet’s surface. For geophysicists like Lekic and Schmerr, this type of research paves the way for future geophysics-focused expeditions to other celestial bodies, such as Venus and Mercury.
“This was a huge effort, involving cutting-edge seismological techniques honed on Earth, as well as new results from mineral physicists and insights from team members who simulate how planetary interiors change over time,” said Jessica Irving, a senior lecturer at Bristol University and the study’s first author. “However, the effort paid off, and we now know a lot more about what’s going on inside the Martian core.”
“Even though the InSight mission ended in December 2022 after four years of seismic monitoring, we’re still analyzing the data that was collected,” said Lekic. “InSight will continue to influence how we understand the formation and evolution of Mars and other planets for many years to come.”
