Earthquakes reveal the planetary core | SETI Institute


It has been an exciting week in the world of space science, with the publication of some groundbreaking stories. Let’s look at the results of three separate articles published this week in the journal. Science on the structure of Mars. The teams involved analyzed the data from NASA InSight lander. Remember how we explained to you how InSight’s seismometer detected hundreds of earthquakes? In the same way that we have used earthquakes to understand the internal structure of the Earth, these teams have done the same for Mars.

First, scientists had to assume that Mars could be similar to Earth, with a series of layers: the crust, mantle, and core. It’s a bit more complicated than that, but it’s a good starting point for understanding the structure of a planet. And as lead author Amir Khan explains: Now, seismic data has confirmed that Mars was probably once completely melted before it split into the crust, mantle, and core we see today, but these are different from those on Earth.

Let’s start with the surface and move on. The crust under InSight, which is near the Martian equator, is between 15 and 47 kilometers thick, which is relatively thin compared to Earth where the crust can be up to 70 kilometers thick. It also means that the chemical makeup of rocks may be more radioactive than those here on Earth.

Under the crust is the mantle of Mars. Here’s where it got a little interesting. Like Earth, Mars has a lithosphere at the top of its more plastic mantle. This lithosphere is twice as thick as Earth’s, ranging from 400 to 600 kilometers deep. Unlike Earth, Mars appears to have only one continental plate, unlike Earth’s seven large plates and many small ones. This structure could explain why we are not seeing any sign of plate tectonics on Mars.

As for the composition of the mantle, the Martian mantle is similar to the Earth’s upper mantle although it appears to contain more iron.

Finally, we come to the point. No, not that terrible disaster movie from 2003, but the innermost layer of a planet. The researchers were able to use the seismic waves detected by InSight to calculate the size of the core, and according to the press release: The Martian core has a radius of about 1,840 kilometers, which is 200 kilometers longer than what was assumed 15 years ago when the InSight mission was planned.

Co-author Simon Stähler goes on to explain: If the radius of the nucleus is large, the density of the nucleus should be relatively low. This means that the core must contain a large proportion of lighter elements in addition to iron and nickel.

So in the core of Mars there are lighter elements like sulfur, oxygen, carbon and nitrogen. But that core is still liquid as the researchers predicted, which is a bit surprising given that Mars no longer has a magnetic field.

InSight has done an incredible job, despite the failure of their drill. And we’re pretty sure there’s more to come, which we’ll continue to bring to you on the Daily space.

More information

This article originally appeared on Moyen, July 27, 2021.

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