NASA’s InSight Lander Provides New Information on Mars Crust, Mantle and Core

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According to new analysis of data from the Seismic Experiment for Interior Structure (SEIS) instrument deployed during NASA’s InSight mission, Mars likely has a 24-72 km (15-45 mile) thick crust with a very deep lithosphere. close to 500 km (311 miles); similar to Earth, a low velocity layer probably exists beneath the Martian lithosphere; the crust of Mars is probably highly enriched in radioactive elements which help to heat this layer to the detriment of the interior; the Martian core is liquid and wide, 1,830 km (1,137 miles), which means that the mantle has only one rock layer instead of two like Earth. These results appear in three articles in the journal Science.

Schematic view of the propagation of seismic waves in the Martian crust and the seismic conversions at the base of the discontinuity, at a depth of 10 km (6.2 miles). Image credit: IPGP.

Like Earth, Mars warmed up when it formed from dust and large clusters of meteorite material orbiting the Sun that helped shape our first solar system.

During the first tens of millions of years, the planet split into three distinct layers – the crust, mantle, and core – in a process called differentiation.

Part of InSight’s mission was to measure the depth, size and structure of these three layers.

“When we started to develop the concept of the mission over a decade ago, the information in these articles is what we were hoping to get in the end,” said InSight Principal Investigator Dr Bruce. Banerdt, researcher at NASA’s Jet Propulsion Laboratory. .

“This represents the culmination of all the work and worry over the past decade. “

The earthquakes most people experience come from faults caused by the shifting tectonic plates.

Unlike Earth, Mars does not have tectonic plates; its crust is more like a giant plate. But faults, or rock fractures, still form in the Martian crust due to the stresses caused by the planet’s slight shrinkage as it continues to cool.

Members of the InSight team spend much of their time looking for bursts of vibration in seismograms, where the slightest movement in a line can represent an earthquake or, for that matter, noise created by wind.

If the ripples in the seismogram follow some known patterns (and the wind is not gusting at the same time), there is a chance that it is an earthquake.

The initial ripples are primary waves, or P, which are followed by secondary waves, or S. These waves can also reappear later in the seismogram after reflecting off the layers inside the planet.

“What we are looking for is an echo,” said Dr Amir Khan, researcher at ETH Zurich.

“We detect a direct sound – the earthquake – then listen to an echo coming from a reflector deep underground. “

“The layering in the crust is something we see all the time on Earth,” said Dr Brigitte Knapmeyer-Endrun, researcher at the University of Cologne.

“The oscillations of a seismogram can reveal properties such as a change in porosity or a more fractured layer. “

Artist's impression of the internal structure of Mars.  Image credit: David Ducros / IPGP.

Artist’s impression of the internal structure of Mars. Image credit: David Ducros / IPGP.

InSight scientists discovered that the Martian crust was thinner than expected and could have two or even three sub-layers.

It goes up to 20 km (12.4 miles) if there are two sublayers, or 37 km (23 miles) if there are three.

Underneath is the mantle, which extends 1,560 km (969 miles) below the surface.

At the heart of Mars is the nucleus, which has a radius of 1,830 km. Confirming the size of the molten nucleus was particularly exciting for the authors.

“This study is a once-in-a-lifetime chance,” said Dr Simon Stähler, researcher at ETH Zurich.

“It took hundreds of years for scientists to measure the Earth’s core; after the Apollo missions, it took them 40 years to measure the core of the moon. InSight only took two years to measure the heart of Mars.

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Facebook Facebook logo Sign up for Facebook to connect with Amir Khan et al. 2021. Structure of the upper mantle of Mars from InSight seismic data. Science 373 (6553): 434-438; do I: 10.1126/science.abf2966

Brigitte Knapmeyer Endrun et al. 2021. Thickness and structure of the Martian crust from InSight seismic data. Science 373 (6553): 438-443; do I: 10.1126/science.abf8966

Simon C. Stähler et al. 2021. Seismic detection of the Martian core. Science 373 (6553): 443-448; do I: 10.1126/science.abi7730

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