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Listening to the heart of Mars has dealt a new blow to the hope of ever finding signs of life on the red planet.
Astronomers used a NASA machine called InSight, designed to study the planet’s vibrations, and analyzed two events that created seismic data: a marsquake and a meteorite that crashed on the opposite side of the planet.
The vibrations passed completely through Mars and were detected on the other side of the planet by InSight’s apparatus. Complex data processing allowed scientists to listen for seismic activity and find out what was at the center of Mars.
They determined that its core was made of liquid metal, mostly iron, but also with plenty of sulfur, some carbon, and a “dusting of hydrogen.”
The core has a radius of about 1,800 km, the data show, making it slightly smaller and denser than previously thought.
Scientists used InSight data from a marsquake and meteorite impact on the far side of Mars in September 2021 to learn about the core. Some seismic waves from these events traveled directly through the planet’s center and through the core, but some bounced around the rocky mantle.
By comparing the two different paths, the scientists were able to determine how the nucleus affected the waves and what it must look like to create those differences.
‘We’ve actually heard energy traveling through the heart of another planet, and now we’ve heard it,’ said study author Dr Jessica Irving of the University of Bristol.
“To get signals that go straight through the center of the planet, your seismic signals have to come from the opposite side of the planet.
“We studied a marsquake and an impact on the opposite side of the planet and each impact produces two sets of waves.
“One way the waves travel is straight through the core and the other way is to stay in the rocky mantle, bounce off the mid-planet surface, then travel back through the rocky mantle and crust to reach the station. They rebound but remain in the rocky layers that we know well”.
The team obtained the first elastic data of the core, as well as improved knowledge of the chemical composition and size of the core. They found that a fifth of the Martian core is made up of light elements, a higher proportion than on Earth. As a result, the core is not as dense as Earth’s which is made up of a higher percentage of iron.
The difference between the two cores could explain why Earth has become a thriving oasis of life and Mars has become a parched, rusty desert, scientists speculate.
“The uniqueness of the Earth’s core allows it to generate a magnetic field that protects us from solar winds, allowing us to retain water,” said Dr. Geology Nicholas Schmerr, of the University of Maryland, and co-author of the paper.
“Mars’ core does not generate this protective shield, and therefore the planet’s surface conditions are hostile to life.”
Scientists believe that although Mars does not currently have a magnetic field and therefore is not protected from the solar barrage of charged sterilizing particles, it may have in the past.
Mars therefore may have had a protective Earth-like magnetic field at some point in its past four billion years before dissipating.
This could be due to the nucleus changing composition and producing a weaker magnetic field, the scientists believe.
“It’s like a jigsaw puzzle in some ways,” said co-author Dr Vedran Lekic, a study co-author at the University of Maryland.
“For example, there are small traces of hydrogen in the core of Mars. This means that there had to be certain conditions that allowed hydrogen to be there, and we need to understand those conditions to understand how Mars evolved into the planet it is today.
“With InSight, we are finally discovering what is at the center of Mars and what makes Mars so similar yet distinct from Earth.”
Dr. Irving added: “The new findings are important for understanding how the formation and evolution of Mars differs from that of Earth.
“New theories about the formation conditions and building blocks of the red planet will need to be able to match the physical properties of the core, as revealed by this new study.”
The new study is published in PNAS.
