Scientists determine thickness of Mars crust

T

he structure of Mars’s crust has been determined for the first time, researchers say.

Based on analysis of “marsquakes” recorded by Nasa’s InSight mission, three studies provide clues to the composition of the Red Planet.

Researchers have reported preliminary findings from the mission and for the first time have begun to map the interior of a planet apart from Earth

Beneath the InSight landing site, the crust is either approximately 20 kilometres or 39 kilometres thick, according to an international research team led by geophysicist Dr Brigitte Knapmeyer-Endrun at the University of Cologne’s Institute of Geology and Mineralogy and Dr Mark Panning at Jet Propulsion Laboratory, California Institute of Technology (Caltech).

Studying a planet’s interior layers – its crust, mantle and core – can reveal key insights into its formation and evolution, as well as uncovering any geomagnetic and tectonic activity.

It is possible that the mantle starts under this layer, which would indicate a surprisingly thin crust, even compared to the continental crust on Earth

Deep interior regions can be probed by measuring the waves that travel through the planet after seismic events like a quake.

The internal characteristics of Earth have been surveyed using such methods.

In the past, only relative differences in the thickness of Mars could be estimated, and additional assumptions were required to obtain absolute thicknesses. These values showed large scatter, depending on which assumptions were made.

Seismology replaces these assumptions with a direct measurement at the landing site, and calibrates the crustal thickness for the entire planet.

The independent data also allows researchers to estimate the density of the crust.

Dr Knapmeyer-Endrun, lead author of the paper published in Science, said: “What seismology can measure are mainly velocity contrasts. These are differences in the propagation velocity of seismic waves in different materials.

“Very similar to optics, we can observe phenomena like reflection and refraction.

“Regarding the crust, we also benefit from the fact that crust and mantle are made of different rocks, with a strong velocity jump between them.”

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