NASA’s InSight probe offers an unprecedented glimpse into the bowels of Mars

For the first time, we know what the interior of another planet looks like like ours. In three studies published Thursday, July 22 in the journal SciencesIn this study, an international team of more than 40 scientists has revealed how the Martian core, mantle, and crust contrast with those on Earth.

By analyzing the seismic data collected by the probe insight From NASA on the Red Planet, researchers estimated the size of Mars’ core, the thickness of its crust, and the composition of its mantle (middle layer). “We just have this kind of information about the Earth and the Moon,” Brigitte Knappmayer-Andron, a planetary seismologist at the University of Cologne and co-author of the new research, told Insider. “But the Moon, we can’t compare it well to the Earth because it’s much smaller.”

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Mars, however, is our smaller Earth twin. New studies indicate that its core is less dense than Earth’s, but by its size.

Propagation of seismic waves through the heart of Mars

The InSight seismometer, captured by the landing camera on September 23, 2020. NASA/JPL-Caltech

InSight, NASA’s $828 million (about €704 million) robotic science station landed on Mars in November 2018. Since then, the probe has used seismometers — which detect and record earthquakes — to listen for similar earthquakes on Earth. Mars. Seismic waves from 12 of these Martian tremors, which traverse the middle of the planet and bounce off the layers within, helped Brigitte Knappmayr-Andron’s group map the boundaries of the crust and core.

“Imagine you have a closed box and you want to know what’s inside,” Brigitte Knappmayr-Andron photographed. “This method is like taking this box and putting it in the X-ray machine.”

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The nucleus of Mars is larger than scientists thought

Artist’s impression of the heart of Mars. Jim Bickle / Science

Its radius of about 1,839 kilometers was “larger than expected,” Amir Khan, a seismologist at ETH Zurich in Switzerland and co-author of the study, told Insider. The boundary of Earth’s liquid outer core – which surrounds a solid, metallic inner core – begins deeper than that of Mars, at about 2,900 kilometres. However, Earth is almost twice as wide as Mars, and its core is also twice as wide.

unlike Earth’s core Dominated by nickel and iron, the less dense core of Mars contains lighter elements such as hydrogen and oxygen. The Red Planet appears to have no inner core, according to Simon Stahler, another co-author and Khan colleague at ETH. “We don’t know, we’ll find out,” Simon Stahler told Insider, adding that “the temperatures may be too high for an inner core to form.”

A more congested core also means that Mars’ mantle is relatively thinner compared to Earth. It is also devoid of a dense layer of a mineral called bridgemanite that keeps the Earth’s mantle stable under high pressure, which may explain the unexpected size of the core. In the metallic sense, Amir Khan said the mantle of Mars is a “simpler” version of the planet Earth.

Mars had and lost its protective magnetic field

Visualize the Earth’s magnetic field. NASA Goddard Space Flight Centerرحلات

The Earth’s core plays a vital role in protecting the planet from dangerous winds and solar radiation. Liquid iron that swirls in the outer core generates a magnetic field Which extends from there to the space surrounding our planet.

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This vortex is due, in part, to a process in which the warmer, lighter material rises from the outer core into the mantle above. There it is replaced by cooler and denser mantle material, which sinks into the lower core. This phenomenon is known as convection. Although Mars has a liquid core, it does not have this engine of rotation, known as a dynamo.

Artist’s impression of the different layers of the Earth. GT

Portions of Mars’ magnetized crust indicate that the planet had a magnetic field 4 to 4.5 billion years ago. The absence of a bridgmanite layer in Mars’ mantle could explain why its dynamism stopped about 300,000 years after the planet’s formation. Without this layer, the interior of Mars would have lost its heat much faster, paralyzing the convection that was going on there. In addition, Simon Stehler said, “Mars is smaller and therefore cools faster than Earth.” “Different planet, different story.”

The crust of the red planet is as thick as the crust of the earth

This illustration shows NASA’s Insight spacecraft with its instruments deployed on the surface of Mars. NASA/JPL-Caltech

The crusts of the two planets are similar, according to Brigitte Knappmayr-Andron, although the crust of Mars is made up of two or three layers. The average thickness of the crust of Mars ranges from 22 to 71 km. fish Crustal It varies greatly – under the oceans it can be up to 4.8 kilometers thick – but under the continents it is between 29 and 71 kilometers thick.

She said that the crust of Mars is very old and firm compared to the crust of the Earth. Our planet’s atmosphere is fragmented into mantle tectonic plates. Through convection, these plates sometimes collide or sink into each other, which means new pieces of crust are constantly emerging.

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Mars does not have this tectonic plates, so that no new crust has been formed since the planet’s crust formed about 4.5 billion years ago. The planet was once “probably completely molten,” Khan said, and then this hot liquid mass diverged into a crust, mantle and core.

The lack of plate tectonics is related, in part, to slow convection in the mantle, according to Simon Stahler. Lack of water also plays a role. “Water lubricates the movement of the plates on Earth,” Stehler explained. “On Mars, water may have been lost very early on, after the dynamo went away and the atmosphere was blown away by the solar wind.”

The next goal of InSight? the moon

The moon under the magnifying glass of Mariner 10, 1973. NASA/JPL/Northwestern University

Scientists have previously used observations of Mars’ mass, diameter, and rotation from space to predict what its inner layers might look like. Simon Stähler was pleased that InSight’s results matched previous expectations. “We were able to confirm the very rough estimates made from orbit,” he said. “So we now know how confident we can be in estimates of the internal structure of Venus or Mercury.”

a taskinsight On the Red Planet is expected to continue until the end of 2022, but the scientific exploration of the lander will not stop next year. InSight will visit moon As part of NASA’s Commercial Lunar Payload Services Program in 2024, Stahler said.

Original copy : Eileen Woodward/Insider

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