Seismic Waves Help Map the Core of Mars for the First Time – Universe Today

More than a hundred years after geologists first observed how seismic waves traveled through Earth, theyve achieved another seismic first. This time, they measured core-transiting seismic waves moving through Mars. The InSight landers seismic instrument tracked shockwaves generated by an earthquake and an impact event. Their behavior revealed for the first time that Mars very likely has a liquid core. Its made of a single blob of molten iron alloy.

By comparison, Earths core is more of a combo plate. It has both a liquid outer core and a solid inner core. They contain mostly iron and nickel. The turbulent outer core is heated by radioactive decay and other processes. It also generates our planets magnetic field.

It turns out that Marss innards are a bit different from Earths. The Martian liquid iron core is also rich in sulfur, with smaller fractions of oxygen, carbon, and hydrogen. That mix of elements makes it much less dense than Earths core, and its more compressible.

According to Nicholas Schmerr of the University of Maryland and a member of a team that used InSight data to study Mars, the differences between Earth and Mars cores hint at different formation stories for each planet. You can think of it this way; the properties of a planets core can serve as a summary of 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, he said. The uniqueness of Earths 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 planets surface conditions are hostile to life.

Interestingly, despite having a liquid iron core, Mars doesnt seem to have much of a global magnetic field. It probably did generate one in the past, however. Planetary scientists suspect that it existed because Marss rocks contain traces of magnetism from ancient times. That magnetic memory gets embedded in rock crystals as they cool in the presence of a magnetic field. That memory can last for millions or billions of years. On Earth, scientists use it to track the motions of our planets tectonic plates, for example. They also use it to monitor changes in Earths magnetic field over timea science called paleomagnetism.

Paleomagnetism studies of Mars rocks tell scientists about Marss magnetic field in the past. Although there isnt one there now, it probably once had one similar to Earths. University of Maryland associate professor of geology Vedran Lekic suggests that Mars changed from a planet with a potentially habitable environment, shielded by a magnetic field, to the more unfriendly place it is today.

What caused it to change? Conditions in the core might have played a role, along with other factors such as violent impacts, according to Lekic. Its 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.

No one has been able to directly image the Martian core. However, planetary scientists have made extensive models of what they think conditions are like there. The InSight seismic measurements confirm the accuracy of those models. 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 part of the team analyzing the InSight results. But the work paid off, and we now know much more about whats happening inside the Martian core.

The team used data from InSight from a marsquake that occurred on August 25, 2021, and an impact that happened on September 18, 2021. They compared the time it took waves from each event to travel through Mars to waves that stayed in the mantle. Those measurements got combined with other seismic and geophysical measurements of the Red Planet. All that data gave the team enough information to estimate the density and compressibility of the material the waves traveled through. Thats how the researchers figured out that Mars most likely has this completely liquid core.

Lekic and Schmerr note 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. Studying the data from InSight and other missions will help them determine more about the conditions that existed in Marss ancient history to give it that core.

Even though the InSight mission ended in December 2022 after four years of seismic monitoring, were 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.

Scientists detect seismic waves traveling through Martian core for the first timeFirst Observations of Core-transiting Seismic Phases on MarsThe Far Side of Mars: Two Distant Marsquakes Detected by Insight

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Seismic Waves Help Map the Core of Mars for the First Time - Universe Today