A team of scientists used seismic data from the now-discontinued InSight mission to directly measure the properties of Mars' core. Analyzes have shown that the Red Planet has a liquid core consisting mainly of iron with a fairly large proportion of sulfur and oxygen. This research could help scientists better understand the history of Mars and why it is so different from Earth.
Seismic data collected by the InSight lander, which monitored the bowels of Mars for four years, allowed for a thorough characterization of the planet's core. Analyzes have shown that the Red Planet's core is about the size of our Moon and almost twice as dense. It is also liquid and consists primarily of iron with sulfur and oxygen.
How to explore the core of Mars?
We have been studying the Earth's core for over a century. Anyway, it doesn't present much of a problem now. Just place the seismographs in the right place and wait for the earthquake. And when they happen, scientists study them with the nearest seismograph, and then do the same with an analog device on the other side of the planet to observe the changes that have occurred in the propagating seismic waves after passing through the core.
As you can easily guess, the biggest problem with exploring the core of any other planet would be related to the need to place the appropriate equipment on it. But that's exactly what happened to Mars, on the occasion of the InSight mission, which came to an end in December last year (more on this in the text: Last photo from the InSight mission. The lander stopped responding).
The problem, however, was that scientists had, admittedly extremely sensitive, but only one seismograph for the entire planet. So how would it be possible to use the aforementioned tactic of exploring the nucleus on Earth? A happy accident turned out to be helpful here.
Surface quake and meteor impact
First of all, Mars is a difficult object to study because the seismic activity on this planet is significantly lower than on Earth. This is best illustrated by the fact that during the first (Martian) year of the mission, the ultra-precise SEIS (Seismic Experiment for Interior Structure) seismometer picked up absolutely no signal.
However, by chance, scientists with only one seismograph had the opportunity to study the effects of not one, but two seismic signals. The first was from a Martian surface quake that occurred quite far from the seismograph on mission day 976. The second was triggered by the fall of a meteorite that occurred elsewhere on the planet 24 days later.
A team of scientists tracked the course of these two seismic events and detected waves that traveled through the planet's core. By comparing the time taken for the waves to travel across Mars with those remaining in the mantle, and combining this information with other seismic and geophysical measurements, the scientists estimated the density of the material the waves passed through, as well as other properties.
What is the core of Mars?
What have we learned? First of all, it turned out that the core of Mars is both slightly smaller and slightly denser than originally thought. Its radius is estimated at 1,000 km. 780 to 1 thousand 810 km. The results of the analysis indicate that the Red Planet most likely has a completely liquid core, unlike Earth's combination of a liquid outer core and a solid inner core.
In addition, the researchers inferred details about the chemical composition of the nucleus. According to them, it contains a surprisingly large amount of light elements (elements with a low atomic number) - namely sulfur and oxygen - present in the innermost layer of the Martian core. The findings suggest that up to one-fifth of the mass of the nucleus consists of these elements. This differs significantly from Earth, where the core has a lower proportion of light elements, indicating that Mars's core is less dense and more compressible than Earth's core. This, in turn, suggests different formation conditions for the two planets.
“The properties of the planet's core can serve as a summary of how the planet formed and how dynamically it evolved over time. The end result of the processes of formation and evolution may be the generation or absence of life-sustaining conditions, explained Professor Nicholas Schmerr of the University of Maryland, co-author of the paper. “The uniqueness of the Earth's core allows it to generate a magnetic field that protects us from solar winds. The core of Mars does not generate this protective shield, so the conditions on the planet's surface are inhospitable to life, he added.
Although Mars does not currently have a magnetic field, scientists believe it did in the ancient past. This is evidenced by traces of magnetism remaining in the crust of Mars. This could mean that Mars has gradually evolved to its present conditions, turning from a planet with potential for habitability to a hostile environment. According to the researchers, interior conditions play a key role in this evolution.
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