In a groundbreaking discovery, scientists have detected seismic waves traveling through the core of Mars, providing crucial information about the Red Planet’s composition and leading to new insights about the formation and evolution of terrestrial planets. The study, published in the Proceedings of the National Academy of Sciences, reveals that Mars has a completely liquid core, rich in sulfur and oxygen, which differs significantly from Earth’s core.
An international research team, including seismologists from the University of Maryland (UMD), used data acquired by the NASA InSight lander to directly measure properties of Mars’s core. The study confirms model predictions of the core’s composition and provides new details about the geological differences between Earth and Mars. These differences could play a role in the planets’ ability to sustain life.
“In 1906, scientists first discovered Earth’s core by observing how seismic waves from earthquakes were affected by traveling through it,” explained study co-author Professor of Geology Vedran Lekic. “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.”
To uncover these differences, the researchers tracked the progression of two distant seismic events on Mars – one caused by a marsquake and the other by a large impact. They detected waves that traveled through the planet’s core and compared the time it took for these waves to travel through Mars with waves that stayed in the mantle.
By combining this information with other seismic and geophysical measurements, the team estimated the density and compressibility of the material that the waves traveled through. Their findings indicate that Mars has a completely liquid core, unlike Earth’s combination of a liquid outer core and solid inner core.
Furthermore, the researchers inferred details about the chemical composition of the planet’s core, discovering that it contains a surprisingly large amount of light elements such as sulfur and oxygen. The study suggests that a fifth of the core’s weight is made up of these elements, a stark contrast to the lower weight proportion of light elements in Earth’s core. This indicates that the core of Mars is less dense and more compressible than Earth’s core, suggesting different formation conditions for the two planets.
“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 study co-author Professor of Geology Nicholas Schmerr. “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’s 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 hypothesize that it once had a core-generated magnetic shielding similar to Earth’s, based on traces of magnetism found in the Martian crust. According to Lekic and Schmerr, this could imply that Mars evolved from a potentially habitable environment to its current hostile state. The researchers believe that conditions in the planet’s interior and violent impacts may have played key roles in this transformation.
“It’s like a puzzle in some ways,” Lekic said. “For example, there are small traces of hydrogen in Mars’s 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.”
The findings of the study have not only provided valuable insights into the Red Planet’s composition and evolution, but have also confirmed the accuracy of current modeling estimates that aim to reveal the hidden layers beneath a planet’s surface. This groundbreaking research is paving the way for future expeditions to other celestial bodies, including planets like Venus and Mercury.
Jessica Irving, a senior lecturer at Bristol University and first author of the study, described the significance of this research. “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. But the work paid off, and we now know much more about what’s happening inside the Martian core.”
Professor Lekic emphasized the lasting impact of the InSight mission, which ended in December 2022 after four years of seismic monitoring. “Even though the InSight mission ended, we’re still analyzing the data that was collected. InSight will continue to influence how we understand the formation and evolution of Mars and other planets for years to come.”
The successful application of advanced seismological techniques may present opportunities for future studies on other planets to gain new insights into their formation, evolution, and potential habitability. As scientists continue to analyze data from the InSight mission, they will uncover more information about Mars’s geological history and the processes that shaped it. This will help researchers better understand the underlying mechanisms that drive the formation and evolution of planets.
While there is no definitive evidence of past or present life on Mars, many scientists believe that the planet may have once had conditions suitable for life. There are several lines of indirect evidence that suggest Mars may have harbored life at some point in its history:
Liquid water is considered a key ingredient for life as we know it, and there is evidence that Mars had liquid water on its surface in the past. Observations made by various Mars missions show signs of ancient riverbeds, lakes, and even a possible ancient ocean. Today, water is mostly present in the form of ice, but some evidence suggests that liquid water might still exist underground.
In 2018, NASA’s Mars rover Curiosity discovered complex organic molecules, which are the building blocks of life, in ancient sedimentary rocks. Although the presence of these molecules does not necessarily imply that life existed on Mars, it shows that the planet had the necessary ingredients for life.
Methane, a gas often associated with biological processes on Earth, has been detected in the Martian atmosphere in varying concentrations. While methane can also be produced through geological processes, the presence of the gas raises the possibility of past or present microbial life on the Red Planet.
Studies of Martian meteorites and data from Mars rovers suggest that the planet’s environment may have been more hospitable to life in the past, with a warmer and wetter climate.
Despite these intriguing findings, no direct evidence of past or present life on Mars has been discovered. Future missions, such as NASA’s Mars Perseverance rover and the European Space Agency’s ExoMars rover, will continue the search for signs of ancient life and help us better understand the habitability of Mars.