The seismic motions of Mars reveal its internal structure

(CNN) – When NASA’s InSight lander landed on Mars in 2018, the mission team hoped the stationary spacecraft would be able to survey the interior of the Red Planet. Now, InSight and its tools have gone beyond those goals, revealing mysteries of Mars’ crust, mantle, and core that have eluded scientists thus far.It is the first time that the interior of another planet outside Earth has been observed and mapped. The InSight mission team achieved this extraordinary feat by tracking Martian earthquakes on the Red Planet, also known as “quakes,” like the earthquakes seen on Earth, which are only slightly different.

The InSight seismometer, called the Inner Structure Seismic Experiment, detected 733 different “swamps.” The researchers analyzed 35 of them, arriving at magnitudes between 3.0 and 4.0, to determine the thickness of Mars’ crust, the depth of the planet’s mantle and, most importantly, to confirm the melting of the planet’s desert ice core.

The results were shared in three studies, all published Thursday in the journal Science.

Before InSight traveled to Mars, all previous robotic explorations of the red planet consisted of studying its surface.

“When we began developing the mission concept more than a decade ago, information from these functions was what we eventually expected to get,” said Bruce Banerdt, InSight principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement. “This is the culmination of all the work and interest in the past decade.”

Learn about Mars through its seismic activity

Unlike the Curiosity and Perseverance rover, InSight is limited to where it landed, unable to clean the surface for plots. However, the lander’s highly sensitive seismometer has the ability to detect martimots hundreds and thousands of kilometers away. You do not need to navigate to study Mars.

When we experience an earthquake, it is because the Earth’s tectonic plates are moving, moving and colliding with each other. So far, Earth is the only planet known to contain these plates.

So how do earthquakes happen on Mars? Think of Mars’ crust as one giant plate. This crust has cracks and fissures in its interior because the planet continues to shrink as it cools. This puts the Martian crust under stresses that stretch and crack.

As seismic waves traveled from the swamps through the various materials within Mars, they allowed researchers to study the planet’s internal structure. This helps them understand the mysterious interior of Mars and apply this research to understanding how other rocky planets form, including our own.

InSight has managed to reveal some of the secrets of Mars’ interior, shedding light on how all the rocky planets formed.

The seismograms collected by InSight are full of ripples, and these ripples can be wind noise or swamp vibrations.

Amir Khan, lead author of What We’re Looking For Is Echo study cloak and a scientist from the ETH Zurich Institute of Geophysics and the Institute of Physics at the University of Zurich, in a statement.

“Direct seismic waves from an earthquake are a bit like the sounds of our own voices in the mountains: they echo,” Philippe Lugnoni, principal investigator in the seismometer and professor at the University of Paris, said in a statement. “And these echoes, reflected in the core, in the front of the tablecloth or even on the surface of Mars, are what we looked for in the signals, thanks to their similarity to direct waves.”

Billions of years ago, Earth, Mars, and the other planets in our solar system formed from a disk of material around the sun, which included clumps of dust and rocks. Planets are very hot when they form. Over time, different layers appeared on the surface of Mars during those first million years, including the crust, mantle, and core.

“Seismic data has now confirmed that Mars was apparently completely molten before it split into the crust, mantle and core as we see it today, but these are different from Earth,” Khan said.

Earth has a thin crust of rock surrounding a thick mantle of rock that surrounds a core made largely of iron and nickel.

Data collected by InSight helped researchers learn that Mars’ thinner-than-expected crust is about 12 miles deep. This crust may have sub-layers extending about 23 miles from the surface.

This artist’s illustration shows the InSight lander and its sensors, cameras, and instruments.

“Intra-crust stratification is something we see all the time on Earth,” said Brigitte Knappmayer-Andron, lead author of the book Cortex study and geophysics of the University of Cologne, in a statement. “The ripples in the seismogram can reveal characteristics such as a change in porosity or a more fractured layer.”

Understanding how Mars’ crust forms, compared to Earth’s, may help researchers understand another part of why the planets in our solar system are so different from one another.

Beneath the crust is the mantle, which travels another 1559.5 kilometers before reaching the liquid metal core.

The researchers were able to confirm the size of the core, which has a larger-than-expected 1,830 km radius, and determine that the core is molten. The liquid core contains iron and nickel, as well as lighter elements such as sulfur, oxygen, carbon and hydrogen.

“This study is a once-in-a-lifetime opportunity,” Simon Stehler, lead author of the primary study and a seismologist at ETH Zurich, said in a statement. “It took scientists hundreds of years to measure Earth’s core; after the Apollo missions, it took 40 years to measure the lunar core. InSight only took two years to measure the core of Mars.”

Earth has a molten outer core surrounding a solid inner core. The InSight mission, which has been extended until 2022, will continue to search for data that can show whether Mars is similar or different from our planet in this respect.

InSight is waiting for the big moment

Mars was once a volcanically active planet. Today’s volcanic regions can be seen across the Red Planet thanks to images from orbits.

Most of the large Martian earthquakes detected by InSight come from a specific region: Cerberus Fossae. This area, which was probably volcanically active only a few million years ago, is filled with rocky trails, possibly formed when it moved by earthquakes.

The largest earthquakes detected by NASA’s InSight appear to have originated in a region of Mars called Cerberus Fossae, imaged by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter.

Meanwhile, other volcanic regions of Mars appear calm. But InSight is still listening and waiting for Mars earthquakes of greater than 4.0 magnitude.

“We’d still like to see a big one,” Mark Banning, co-author of the crust study and JPL research scientist in planetary interiors and geophysics, said in a statement. “We have to do a lot of micro-processing to get what we want from this data. Having a bigger event will make all of this easier.”

The constant stream of data InSight sends back to scientists on Earth will end in about a year, when solar cells can no longer generate enough power. But researchers will study the discoveries InSight has made for decades to learn as much as possible about our mysterious planetary neighbor.

“Mars still poses many mysteries, among them the question of whether it formed at the same time and from the same material as our Earth,” study author Domenico Giardini, professor of seismology and geodynamics at ETH, said in a statement. from Zurich.