A team of international researchers, including seismologists from the University of Maryland, have successfully detected seismic waves traveling through Mars’ core for the first time, revealing new insights into the geological differences between Earth and Mars. The team used seismic data from NASA’s InSight lander to measure the properties of Mars’ core, confirming model predictions of the core’s composition.
Observing Seismic Waves
The team tracked 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. By comparing the time it took those waves to travel through Mars compared to waves that stayed in the mantle, the team estimated the density and compressibility of the material the waves traveled through. Their findings indicated that Mars has a completely liquid core, unlike Earth's combination of a liquid outer core and solid inner core.
Composition of the Core
The team inferred details about the core's chemical composition, such as the surprisingly large amount of light elements, namely sulfur and oxygen, present 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.
Implications for Planetary Habitable Conditions
The properties of a planet’s core can serve as a summary of how the planet formed and evolved dynamically over time. The end result of the formation and evolution processes can be either the generation or absence of life-sustaining conditions. 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.
Evolution of Mars
Although Mars does not currently have a magnetic field, scientists hypothesize that there was once a magnetic shielding similar to Earth's core-generated field due to traces of magnetism lingering in Mars' crust. This might mean that Mars gradually evolved to its current conditions, changing from a planet with a potentially habitable environment into an incredibly hostile one. Conditions in the interior play a key role in this evolution, as might violent impacts, according to the researchers.
Future Geophysics-Oriented Expeditions
The team’s findings have ultimately confirmed the accuracy of current modeling estimates that aim to unravel the layers hidden beneath a planet's surface. For geophysicists, research like this is paving the way for future geophysics-oriented expeditions to other celestial bodies, including planets like Venus and Mercury.
Continuing Research
The InSight mission ended in December 2022 after four years of seismic monitoring, but the team is 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.
Journal Information: Irving, Jessica C. E., First observations of core-transiting seismic phases on Mars, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2217090120
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