When Galileo observed the planet Mars with a telescope over 400 years ago, it registered as little more than a blank orb, suspended in infinite darkness. Over the next four centuries, scientists tried to fill in the gaps.
Shortly after Galileo, Dutch astronomer Christiaan Huygens arrived and made a profound discovery on Mars. Observing the planet in 1659, Huygens noticed a large dark area on its face, shaded as a heart-shaped spot in a sketch of the red planet. It was the first time humans observed otherworldly surface features.
About 359 years later, in November 2018, NASA posed InSight on the Martian surface about 2,000 miles east of the spot, the eighth time the space agency has placed a robotic explorer on the red planet. Its mission, which was recently extended to 2022, is to listen to "marsquakes " and understand what is happening beneath the surface of our cosmic neighbor.
In a series of three studies published in the Science journal Thursday, a global team of researchers describes the interior of Mars using data obtained by InSight 'sseismometer, an instrument that responds to vibrations and noise beneath My rs 'surface. Analysis of a series of earthquakes, felt by InSight since 2019 , researchers were able to reveal for the first time the inner workings of another planet of our solar system - a breakthrough for the planet geosciences. Science
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Listening to the Ground
The first planetary rattle detected by InSight's seismometer, known as de SEIS, in 2019 looked like this first provisional drawing by Huygens. It revealed that Mars was more seismically active than the Moon, but not as active as Earth, and gave researchers a tantalizing first look at the kind of data InSight would be able to collect.
A sectional view of SEIS , a dome-shaped instrument that sits on the surface of Mars. The outer white layer protects the sensitive instrument from the environment, while the inner layer of organi zed chaos contains pendulums that measurerent vibrations and noise. NASA / JPL-Caltech / CNES / IPGP
SEIS (pictured right) is a dome-shaped instrument that was deployed shortly after InSight arrived on Mars. It sits on Martian soil and, as NASA says, is like a doctor's stethoscope, listening to the "pulse" of the planet. It is an extremely sensitive technology, recording the seismic waves that rumble and vibrate inside the planet after an earthquake.
Its outer dome is a shield against the Martian environment, protecting SEIS from winds and dust that could affect internal vibration measurements. The seismometer itself is a fairly simple device: it contains three weights, suspended like a pendulum, which can detect vibrations from different directions, such as when a seismic wave, generated by an earthquake, hovers over them.
Froms previous research has shown that earthquakes are common, but they are not very powerful. Only a handful of registers above magnitude 3 which on Earth may sound like a slight rumble a few miles away, but are not loud enough to cause significant damage to constructions and buildings. Most come from the top layer of the earth's crust, but studies have probed 10 that came deeper below the surface.
Listening to the waves generated by these earthquakes is how the researchers figured out March. 'bowels. The seismic waves that travel through the interior of the planet are modified by the material with which they come in contact, allowing InSight to paint a picture of what is happening in the earth.ol.
Ogres, onions and other planets
The anatomy of a "differentiated " planet like Mars is, to borrow from a 20-year-old movie, everything like an onion (... or an ogre). He has diapers. Although scientists have filled in the blanks when it comes to surface characteristics, atmosphere, and soil chemistry, it is a mystery what goes on below the surface.
"For all we know about Mars - most of it is limited to the top meter, "says Gretchen Benedix, an astrogeologist at Curtin University in Australia who was not affiliated with the study. "It's like looking at a gift and focusing on the packaging.
In new studies, researchers first probed these layers by studying the waves that were shaking InSight 's SEIS. "This new information is like opening the present to take a look, " said Benedix.
One of the studies, led by Brigitte Knapmeyer-Endrun, a geophysicist at the University of Cologne, used the data to study the top layer of the planet, known as the crust.
The top layer of the crust, made up of rocks basaltic from ancient lava flows, appears to be at most 10 kilometers (6.2 miles) thick. But data from InSight revealed that another layer, about double that size, is just below. Underneath, Knapmeyer-Endrun said in a press release, could be where the "mantle " begins - which would make the crust of Mars "surprisingly thin.
A " selfie "of the InSight lander, taken on the surface of Mars. NASA / JPL-Caltech
But the team also showed that there may be a third layer of the crust, extending the depth to around 40 kilometers.
Then there's the Martian core, which has a few surprises in store of its own.
As shown in the image above, earthquakes can send vibrations up. 'in the heart of the planet, where they bounce back and forth back to SEIS. These signals, like described in a study led by Simon Stähler, geophysicist at ETH Zurich in Switzerland, were relatively small but allowed an estimate of the size of the planet's core. And size matters here.
The boundary between the mantle and the core appears to be just under 1,000 miles below surface, which is wider than some studies have suggested.The suggestion, according to a companion article published in Science on Thursday, is that the iron-nickel core is less dense than expected, but that it is in the liquid state as other studies have supported.
Why is it inside Martian matter?
The return of seismology on Mars has been described by University of Texas geophysicist Yosio Nakamura as "a new dawn " in un comreport of Nature Geoscience in 2020 . The ability to detect seismic waves helps place fundamental constraints on how the planet has likely evolved over time and, according to Benedix, "tells us a lot about the thermal evolution of this planet.
Heat emanates from a planet's core during its formation and early evolution and by understanding the composition of the core, researchers can make hypotheses about how Mars may have cooled down. over time. Combining this with other data, obtained by orbiting spacecraft and NASA and Chinese rovers, doesn't just help us understand Mars - it reveals how planets form, change, and develop. throughout the solar system and potentially outside of it. , too.
InSight also attempted to directly measure the temperature below the surface of the red planet using a "burrowing molee ". But early on, as the mole attempted to dig into the insane soil of Mars, it got stuck. The heroic attempts of NASA engineers to free the mole proved unsuccessful, and in January , he was declared dead . However, InSight 's mission is not over - it will continue to listen to earthquakes until 2022 Although it only provides a single "ear", so to speak, repeated observations should allow scientists to further refine their understanding of Mars.
In Less than four centuries, we have gone from Huygens 'sketch of a heart-shaped spot on the face of Mars to understanding the very heart of Mars itself. May the blanks continue to be filled.