The Martian core refers to the central part of the planet Mars, which is believed to be composed primarily of iron and nickel. For the first time, scientists were able to witness seismic waves moving through Mars’ core, and the composition of the core was validated by models.
A totally liquid iron-alloy core with high concentrations of sulfur and oxygen was discovered by an international research team that includes seismologists from the University of Maryland. The researchers used seismic data collected by the NASA InSight lander to directly analyze the properties of Mars’ core.
Published in the Proceedings of the National Academy of Sciences on April 24, 2023, these findings reveal new insights into how Mars formed and the geological differences between Earth and Mars that may ultimately play a role in sustaining planetary habitability.
Studying the Martian core can provide valuable insights into the planet’s formation and evolution, as well as its magnetic field and potential for supporting life. Understanding the core’s composition and dynamics helps scientists unravel the geologic history of Mars, including its volcanic activity, tectonic movements, and magnetic field generation.
“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.”
The scientists traced the development of two distant seismic events on Mars, one brought on by a marsquake and the other by a significant impact, and discovered waves that passed through the planet’s core to ascertain these distinctions.
The researchers calculated the density and compressibility of the material the waves passed through by comparing the time it took those waves to pass through Mars to those that remained in the mantle and combining this data with other seismic and geophysical measurements. In contrast to Earth’s combination of a liquid outer core and solid inner core, the researchers’ findings suggested that Mars most likely had a totally liquid core.
In 1906, scientists first discovered the Earth’s core by observing how seismic waves from earthquakes were affected by traveling through it. 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.
Professor Vedran Lekic
The scientists also deduced information on the chemical makeup of the core, such as the surprisingly high concentration of light elements, or those with low atomic numbers, like sulfur and oxygen, in Mars’ innermost layer. The team’s findings suggested that a fifth of the core’s weight is made up of those elements.
This high percentage differs sharply from the comparatively lesser weight proportion of light elements in Earth’s core, indicating that Mars’ core is far less dense and more compressible than Earth’s core, a difference that points to different conditions of formation for the two planets.
“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.”
Despite the absence of a magnetic field now, researchers believe that Mars formerly had one because of residual magnetism in its crust, which is similar to the magnetic shielding produced by the Earth’s core.
According to Lekic and Schmerr, this may indicate that Mars gradually changed from a planet with a possibly habitable climate to one that is extremely hostile. According to the experts, internal conditions as well as potentially severe impacts have a significant effect in this process.
“It’s like a puzzle in some ways,” Lekic said. “For example, there are small traces of hydrogen in Mars’ core. That means that there had to be certain conditions that allowed the hydrogen to be there, and we have to understand those conditions in order to understand how Mars evolved into the planet it is today.”
In the end, the team’s findings have validated the reliability of recent modeling projections that seek to reveal the layers buried beneath a planet’s surface. Research like this is also laying the groundwork for upcoming geophysics-focused journeys to other celestial bodies, such as Venus and Mercury, according to geophysicists like Lekic and Schmerr.
“This was a huge effort, involving state-of-the-art seismological techniques which have been honed on Earth, in conjunction with new results from mineral physicists and the insights from team members who simulate how planetary interiors change over time,” noted Jessica Irving, a senior lecturer at Bristol University and first author of the study. “But the work paid off, and we now know much more about what’s happening 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,” Lekic said. “InSight will continue to influence how we understand the formation and evolution of Mars and other planets for years to come.”
