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How NASA discovered the core of Mars is molten

Much of what we know about other planets is based on what we can see and infer from experiences on our own planet, but as science and space exploration marches forward, we learn that perhaps we don’t know as much as we think we do.

Case in point, this week NASA confirmed that unlike Earth, Mars houses a molten core. While Earth does have an outer core that is molten, the inner core is a solid ball comprised of nickel and iron.

This discovery was outlined in three papers published in Science this week that take an in-depth look at the Red Planet’s structure and how NASA came to these findings is incredibly interesting.

It all starts with the Insight rover which arrived on Mars in 2018. Aboard the plucky robot was the Seismic Experiment for Interior Structure (SEIS).

While the rover spent much of its life roaming the surface, SEIS allows NASA to observe the interior of Mars through marsquakes. The SEIS has measured 733 marsquakes, but researchers focused their attention on 35 quakes measuring between 3.0 and 4.0 magnitude.

These are relatively tiny movements with quakes of this magnitude classified as minor to light on the Richter scale. If you were to experience a 4.0 magnitude quake on Earth you’d likely have a few broken glasses but there wouldn’t be much damage.

Essentially, NASA is looking for the smallest movements beneath the Martian surface and then studying how long primary and secondary waves (known as P-waves and S-waves respectively) take to echo off of materials beneath the surface.

As seismic waves move through different materials the speed and shape of the waves will differ and that gave scientists a way to determine how many layers Mars has.

Each of the aforementioned papers published in Science looks at a section of the Martian interior, but all used SEIS data albeit in different applications.

In the study of the crust the speed at which each wave returned was measured and timings between those waves gave an idea of whether a wave had crossed a layer.

Meanwhile, the velocity of the waves was used to help understand the consistency and temperature of the mantle.

Finally, to determine the core is molten, researchers studied S-waves bouncing off of the core.

We highly recommend reading this piece from Inverse which features comments from Mark Panning, a geophysicist at NASA who explores the findings in more depth.

With all of these studies NASA says that the crust could be as thin as 20 kilometres if there are two layers, but could go as deep as 37 kilometres if its three layers. The reason NASA can’t say for certain is that it used two different models to determine the crust’s thickness.

The mantle stretches 1 560 kilometres into the depths of the planet before we reach the core which has a radius of 1 830 kilometres.

“It took scientists hundreds of years to measure Earth’s core; after the Apollo missions, it took them 40 years to measure the Moon’s core. InSight took just two years to measure Mars’ core,” explains lead author on the core paper and researcher at ETH Zurich, Simon Stähler.

All of this goes to show just how little we really know about the galaxy and the universe at large.

InSight and SEIS will continue to monitor Mars for quakes and hopefully it will lead to a better understanding of not only our celestial neighbour, but perhaps other planets and moons within our own solar system as well.

[Source – NASA][Image – CC 0 Pixabay]

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