Researchers have shed new light on the origins and composition of the planet Mars.
The study uncovered insights into the Red Planet’s liquid core, aiding understanding of its formation and evolution.
The research reveals the first detections of sound waves traveling into the Martian core, finding it to be slightly denser than previously thought.
Measurements of this acoustic energy, called seismic waves, also indicate that the nucleus is smaller than previously thought and comprises a mixture of iron and numerous other elements.
The researchers say the results are all the more remarkable, as the mission was initially scheduled to last only a little over a year on Mars (two Earth years).
Although the Martian storms accelerated the accumulation of dust and reduced the power of the NASA InSight Mars lander, the space agency extended its stay, so geophysical data, including earthquake signals, continued to be collected until the end of last year.
Lead author Dr Jessica Irving, senior lecturer in earth sciences at the University of Bristol, said: ‘The extra mission time has certainly paid off. We have 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, allowed us to probe the Martian core with seismic waves.
“We’ve actually heard energy traveling through the heart of another planet, and now we’ve heard it.
“These first measurements of the elastic properties of Mars’ core helped us study its composition. Instead of just being a ball of iron, it also contains a large amount of sulfur, as well as other elements including a small amount of hydrogen.”
The study, led by researchers at the University of Bristol, used data from NASA’s InSight lander, a robotic spacecraft designed to probe the interior of Mars, to compare the seismic waves traveling through the planet’s core with those transit in the shallower regions of Mars, and modeled the properties of its interior.
In 2018, the lander deployed a broadband seismometer on the Martian surface enabling the detection of seismic events, including earthquakes and meteor impacts.
The multidisciplinary team of scientists 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 compared to seismic waves that remained in the mantle.
Dr. Irving said, “So-called ‘far’ events – those on the opposite side of the planet from InSight – are inherently more difficult to detect because a large amount of energy is lost or deflected as the waves travel across the planet.
“We needed both luck and skill to find, and then use, these events. We have not detected distant events in the first Martian year of operations.
“If the mission had ended then, this quest could not have happened.”
The authors used these measurements to build models describing the physical properties of the nucleus, including the size and speed of the elastic wave.
The results suggested that Mars’ core is slightly denser and smaller than previous estimates, with a radius of about 1,780-1,810 km.
The results are consistent with the fact that the core has a relatively high fraction of light elements bonded to iron, including abundant sulfur and smaller amounts of oxygen, carbon and hydrogen.
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 findings are published in the journal Proceedings of the National Academy of Sciences.