martesit is a dry planet ruled by global dust storms. It's also a frigid world, where nighttime winter temperatures drop to minus 140 C (minus 220 F) at the poles.
But it was not always a dry, barren, frozen and inhospitable wasteland. It used to be a warm, humid, almost cozy place where liquid water flowed across the surface, filling lakes, opening channels and leaving deltas of silt.
But then it lost its magnetic field, and without the protection it provided, the Sun stripped away the planet's atmosphere. Without its atmosphere, water was next.
Now Mars is the Mars we've always known: a place only robotic rovers find hospitable.
How exactly did he lose his magnetic shield? Scientists have been puzzled by this for a long time.
A magnetic shield is critical to preserving Earth's atmosphere and habitability. Without it, Earth would look like Mars. But the Earth maintained its protection and Mars did not. Therefore, Earth is "bursting with life", as Carl Sagan put it, while Mars is probably completely devoid of life.
Mars has a weak remnant of a magnetic field emanating from its crust, but it is a weak phenomenon that offers little protection.
The loss of its magnetosphere was catastrophic for Mars. How did this happen?
A newstudy published innature communicationstries to answer this question, like many previous studies. The title is "Shedding in Planetary Cores by Liquid Immiscibility in Fe-S-H". Lead authors are Kei Hirose of the Department of Earth and Planetary Sciences at the University of Tokyo and Ph.D. student Shunpei Yokoo in Hirose's lab.
The Earth's core creates a magneto effect that generates the magnetic fields of our planet. There is a solid inner core and a liquid outer core.
Heat flows from the inner core to the outer core, generating convective currents in the liquid outer core. Convective currents flow in patterns generated by the planet's rotation, the inner core, and the Coriolis effect. This creates the planet's magnetosphere.
The magnetosphere surrounds the Earth like a protective cloak. The solar wind from the Sun hits the magnetosphere, and the magnetosphere forces it to flow around the planet instead of reaching the atmosphere or surface.
The magnetosphere is not a sphere: the solar wind moves the magnetosphere in an asymmetrical fashion. The magnetosphere prevents the solar wind from destroying Earth's atmosphere. Without it, the Earth would be dry, dead and barren, like Mars.
So what happened to Mars?
"Earth's magnetic field is driven by inconceivably large convection currents from molten metals at its core. Magnetic fields on other planets are thought to work in the same way," Hirosesaid in a press release.
"Although the internal composition of Mars is not yet known, meteorite evidence suggests that it is sulfur-enriched molten iron. Additionally, seismic readings from NASA's InSIGHT probe on the surface tell us that the core of Mars It's bigger and less dense than that." from Mars. previously thought. These things imply the presence of additional lighter elements like hydrogen."
and NASAInSIGHT landerHe struggled to achieve all of his scientific goals. But he did gather some critical evidence about the interior structure of Mars. If the InSIGHT results are correct and the implied hydrogen is there, there is a basis for experiments that could reveal more about the loss of Mars' magnetic shield.
(NASA/Goddard/MAVEN/CU Boulder/SVS/Cindy Starr)
on top of oneVisualization of electrical currents around Mars. Electrical currents (blue and red arrows) encircle Mars in a nested, double-circuit structure that continuously encircles the planet from the day side to the night side. These current loops distort the magnetic field of the solar wind (not shown), which surrounds Mars to create an induced magnetosphere around the planet.
"With this detail, we prepare iron alloys that we hope will form the core and subject them to experiments," Hirose said.these.
Previous experiments have investigated the behavior of planetary cores at different pressures and temperatures. But they did not focus on hydrogen.
"Recent theories of planet formation demonstrate that a large amount of water was delivered to Mars and Earth during their accumulations, suggesting that hydrogen is possibly an important light element in the core," the authors wrote.explainon your paper. "Despite its importance, the Fe-S-H system has so far been little investigated at high pressures."
But if the InSIGHT data is correct, hydrogen in the Fe-S-H core could play a role in the collapse of Mars' magnetic field.
The researchers prepared a sample of material that matches what they believe the core of Mars was once composed of. It contained iron, sulfur and hydrogen – Fe-S-H. They placed the sample in a device called a diamond anvil or diamond anvil cell (DAC).
The diamond anvil cell used in the experiments. (Yokoo et al.)
A diamond anvil compresses samples between two small diamond plates. Diamonds can withstand extreme pressure within the anvil because they are forged under extreme pressure deep within the Earth.
The DAC can subject microscopic samples to pressures of hundreds of gigapascals. A laser heated the sample so that conditions simulated the core of Mars. As the team subjected the sample to higher temperatures and pressures, they observed it with X-rays and electron beams to track changes in the material. The Fe-S-H sample not only melted, but also changed its composition.
The results of the experiment center on the idea of miscibility. When materials are added to create a homogeneous mixture, they are miscible. When materials are added and do not form a homogeneous mixture, they are immiscible. The immiscibility of Fe-S-H at high temperatures and pressures played an important role in Martian planetary history.
"We were very surprised to see a particular behavior that could explain a lot of things," Hirose said.thesein a press release. "The initially homogeneous Fe-S-H separated into two distinct liquids with a level of complexity never seen before under this kind of pressure," Hirose said. "One of the iron liquids was rich in sulfur, the other rich in hydrogen, and this is the key to explaining the birth and eventual death of the magnetic field around Mars."
Hirose and his team think that two immiscible liquids initially separated in the core of Mars.
"While the separated denser liquids remained in the deep end, the lighter liquids migrated upward and mixed with the bulk liquid core, which could drive convection of the Martian core," they said.write.
But in the region where the two liquids separated, something else happened. "At the same time, gravitationally stable compositional layering should have developed in a region where liquid separation occurred. Eventually, the entire core of Mars layered, stopping convection."
(Yokoo et al., National Community, 2022)
Above:This figure from the article shows how the core of Mars and Earth started out similar and then changed over time. Light blue and dark blue represent buoyant and dense liquids, respectively.
Scientists already knew when the convection ceased and Mars lost its magnetic shield. This happened about 4 billion years ago. This study explains why the convection ended, leading to the loss of the magnetic shield.
It also explains how it all started. "The separation of immiscible S-rich and H-rich liquids could have been responsible for both the initiation and termination of the convection of the Martian core and the action of the dynamo," they state.writeon your paper.
Once the two liquids separated, Mars was doomed. There was no more convection, no magnetism, no atmosphere, no water. The exact time frame is unknown, but the result was a dead planet.
However, this is just one study and we don't have the full picture. "With our results in mind, we hope that further seismic survey of Mars will verify that the core is in distinct layers, as we predicted."theseHirose. "If that's the case, it would help us complete the story of how rocky planets, including Earth, formed and explain their composition."
We know that Earth will not remain habitable forever. In about 5 billion years, the Sun will enter its red giant phase and destroy the Earth. But our protective magnetic shield won't last forever either, and we're doomed without it. What will happen first? Fatality due to loss of magnetosphere? Or destruction by a red giant?
"And you might be thinking that Earth could one day lose its magnetic field as well," Hirose said.these, "but don't worry, it won't happen for at least a billion years."
So we have a billion years. Let's not waste it.