Earth's core may be cooling faster than scientists thought
Louisa Wright
January 20, 2022
At the center of Earth sits the planet's fiery core, which scientists say might be losing heat faster than expected.
A mineral in the Earth's core-mantel boundary plays a role in the new discoveryImage: Cigdem Simsek/Zoonar/picture alliance
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Earth's core has been cooling since the planet formed some 4.5 billion years ago, when the entire surface was covered with oceans of magma.
Scientific understanding of how quickly this cooling occurs was challenged in a study published January 15 that suggests the process is moving much faster than scientists thought.
The discovery, by researchers from Switzerland, Germany, the US and Japan, adds to a body of research that supports the idea that radiation plays a bigger role in heat extraction from the Earth's core than once assumed.
The core-mantle boundary lies between the Earth's lower mantle and its liquid core. Scientists believe it is largely composed of a mineral called bridgmanite, characterized and named after physicist Percy Bridgman in 2014. Scientists consider bridgmanite the most abundant mineral on the planet.
"We eventually found that the previous thermal conductivity value [of bridgmanite] was highly underestimated," said Motohiko Murakami, an earth sciences professor at ETH Zurich and lead author of the study.
Murakami and his colleagues found that the thermal conductivity of bridgmanite was 1.5 times higher than expected.
"The heat transfer from the core would go more efficiently than previously thought, which ultimately leads to the cooling of the core more rapidly than expected," Murakami said.
A tricky study subject
Scientists are not able to reach the Earth's core, which makes it hard to study.
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What they can do are geophysical studies and experiments that simulate the conditions deep down in the Earth.
This is what Murakami's team attempted to do by synthesizing the mineral bridgmanite, said Helen Williams, a geochemist at the University of Cambridge in the United Kingdom who was not involved in the study.
A synthetic mineral is one scientists have made themselves in the lab, rather than found in nature.
The equipment Murakami and his colleagues used to work this out can fit in your hand: a diamond anvil cell.
A mineral sample is placed in a tiny chamber, where it's compressed by diamond walls from all sides. The sample is heated by a laser that shines through the diamond, said Karin Sigloch, a geophysicist at the French National Center for Scientific Research and Côte d'Azur University, who was also not involved in the study.
"This produces tiny rock samples that are hopefully equivalent to those in the deep earth," she said.
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'The result is an important one'
"The conventional wisdom has been that radiation does not contribute significantly to heat transport anywhere in the solid Earth," Gerd Steinle-Neumann, who researches the Earth's interior at the University of Bayreuth in Germany and was not involved in the study, told DW.
"The experiments by Murakami confirm previous studies that radiation can enhance heat extraction from the core to the mantle by approximately 50%, speeding up heat loss from the entire Earth," Steinle-Neumann said.
Singloch said the result from Murakami and his colleagues' research is significant, but that she noticed a gap between the findings and the paper's discussion about tectonic implications.
"The result is an important one," Sigloch said, adding that it helps clarify that radiative heat transfer and conductive heat transfer likely play more comparable roles than previously assumed in the core's cooling.
"This is a number that contributes to our quantitative understanding of core cooling, and how core cooling contributes to mantle behavior," she said.
But, even if the Earth is cooling faster, it won't have an impact on the current climate crisis.
"This is planetary cooling taking place on billion-year timescales, whereas the current anthropogenic global heating is taking place on decadal timescales," Williams said.
Edited by Clare Roth
Space tourism: Out of reach for most Earthlings
Space tourism began in 2001 with Italian-American millionaire Dennis Tito. Decades later, it's still a preserve of the rich and essentially white.
Image: Joe Skipper/REUTERS
An unbeatable record
Dennis Tito was and always will be the first civilian to travel to space. Tito had been a NASA engineer before turning to finance. He had always dreamed of a trip to space and is said to have paid $20 million to have his dream come true. It was hard convincing the big space agencies, but on April 28, 2001, Tito took a ride on a Soyuz rocket and spent six days at the International Space Station.
Image: picture-alliance/dpa
In second place: Mark Shuttleworth
So, the name's fitting — shuttle-worth. But beyond that you'll quickly see a bias emerge. The first space tourists were all nerdy engineers… and all but one were MEN. South African Mark Shuttleworth, an internet and software engineer, flew a year after Tito and is celebrated as the first African in space. We're still waiting for the first Black African to make it — not for want of trying, though.
Image: picture alliance/AP Photo/M. Grachyev
Afronaut: Mandla Maseko
There's never been a Black African astronaut, neither agency-based nor a tourist. Mandla Maseko, a DJ from a township in Pretoria, South Africa, was due to be the first "Afronaut" until he died in a road accident at the age of 30. Maseko had won his chance through a private venture called Ace Apollo Space Academy. Seen as an inspirational figure, he said: "Defy gravity in everything that you do."
Image: Themba Hadebe/AP Photo/picture alliance
Third: Gregory Olsen
The third "official" space tourist was millionaire scientist Gregory Olsen. As Tito and Shuttleworth before him, Olsen bought his ticket through a company called Space Adventures and flew on a Russian Soyuz rocket. Olsen sold his own company, Sensors Unlimited, which under new owners Collins Aerospace is a NASA contractor, to pay his way. And he says he'd sell another firm to do it all again.
Image: Ivan Sekretarev/AP Photo/picture alliance
Fourth: Anousheh Ansari
So, it's not only boys who dream of the stars. Anousheh Ansari dreamed of space as a child as well. An engineer, internet technologist and co-founder of the XPRIZE Foundation, Ansari spent 11 days in space in 2006. She is described as the first astronaut of Iranian descent and the first Muslim woman in space. Her foundation champions itself as having "ignited a new era for commercial spaceflight."
Image: picture-alliance/Everett Collection
Science tourist: Helen Sharman
In 1991, Helen Sharman became the UK's first astronaut. Sharman conducted scientific experiments on the Soviet/Russian space station Mir, so hers was a mission in the traditional sense. We're including Sharman because her mission started as a commercial venture, but the company failed. The Soviets, whose idea it was anyway, paid in an act of bettering relations between them and the West.
Image: Alexander Mokletsov/dpa/Sputnik/picture alliance
The man who went twice: Charles Simonyi
Charles Simonyi is the first space tourist to have taken two trips. The billionaire software engineer first flew in 2007 and then again in 2009. But Simonyi holds other records, too. At the age of 13, he was selected as a junior astronaut in his native Hungary, and he developed the world's first WYSIWYG (what-you-see-is-what-you-get) text editor, Bravo. He thinks humans will live in space one day.
Image: Mikhail Metzel/picture-alliance/dpa
Not just gaming around: Richard Garriott
British-American Richard Garriott (left) had an early interest in space travel due to the fact that his dad, Owen, was a NASA astronaut. Family friends and neighbors were astronauts, too. But he became a computer games developer and that's how he paid for his trip in 2008 — but he was also an investor in the space tourism company, Space Adventures. He's known to dress up as a medieval knight.
Image: AP
From circus of the sun to the stars: Guy Laliberte
A native of Quebec, Guy Laliberte is the original creative mind behind the world-famous circus company, Cirque du Soleil ("Circus of the Sun"). He spent 10 days at the International Space Station in 2009 and is the last of the old-school space tourists. Following Laliberte's trip, no tourists flew for over a decade. This shot of a Soyuz capsule returning to Earth was almost the end of it. Until…
Image: AP/NASA/BILL INGALLS
Richard Branson rears his head
Boys and their toys: Virgin Galactic's Richard Branson just had to pip Amazon-man Jeff Bezos at the post. His reward? The US Federal Aviation Administration grounded Branson's SpaceShipTwo for deviating from its flight path as it descended from the edge of space on July 11, 2021. Got to hand it to Branson, though — he's been at it for decades. SpaceShipOne won the Ansari XPRIZE in 2004.
Image: Andres Leighton/AP Photo/picture alliance
Just another dreamer: Jeff Bezos
Branson and Bezos (in hat) are competitors. They're also in a private space travel clique with common goals and would get nowhere without each other — or early test pilots Brian Binnie and Mike Melvill and investors like Microsoft co-founder Paul Allen or Peter Diamandis, co-founder of Space Adventures and XPRIZE. On July 20, 2021, Bezos and three others took a suborbital flight. Will you be next?
Image: Blue Origin/Anadolu Agency/picture alliance
