Yahoo Movies Earth's Core Is Cooling Faster Than Scientists Expected
While the timeline is hard to pinpoint, Earth's core is cooling faster than expected.
The interface between core and mantle is bridgmanite, a mineral with strange properties.
To study bridgmanite, scientists used diamond anvils and a pulsating laser.
Earth's core may be cooling on a shorter time schedule than we've been led to believe, according to scientists from the Swiss university ETH Zürich and the Washington, D.C.-based Carnegie Institution of Science (CIS). That means less time before our blue planet turns into a lifeless new version of Mars. The explanation, researchers posit in a new paper, could be as simple as the reason why your cold floor makes your whole body colder in the winter: the simple transfer of heat.
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Earth's mantle is dominated by a silicate mineral called bridgmanite (MgSiO3-perovskite), named after high-pressure scientist and Nobel Prize winner Percy Williams Bridgman. Scientists have known about the mineral for decades, but only examined it up close for the first time in 2014. Earth's mantle is so huge and deep that bridgmanite is one of the most common minerals on Earth without ever really touching the surface—except in a unique fragment of a meteor that fell in Australia in the 1800s.
Experts have long wondered about the transfer of heat from Earth's core to its slightly cooler mantle, but it's a difficult chemical reaction to study. The core is up to 6,000 degrees Celsius, about the same temperature as the surface of the sun, making it difficult to recreate in safe laboratory conditions. That's on top of having to manufacture bridgmanite to begin with because of its scarcity on Earth's surface.
To solve this longstanding laboratory problem, scientists at ETH and CIS had to invent a new way to study these materials up close. They placed a tiny amount of bridgmanite and a thermal probe in the center of a striking pair of diamond anvils to mimic the high pressure that smashes onto Earth's core and mantle. The researchers outline this process in a new paper published earlier this month in the journal Earth and Planetary Science Letters.
As for the temperature, a pulsing laser brought the bridgmanite sample up to the extremely high temperatures required to study how bridgmanite conducts heat from Earth's core. By combining the high pressure and high temperature while controlling the durable diamond anvils, scientists could, for the very first time, actually measure how bridgmanite conducts heat.
ETH professor Motohiko Murakami says the ingenious system quickly bore fruit. "This measurement system let us show that the thermal conductivity of bridgmanite is about 1.5 times higher than assumed," he says in a prepared statement. If that number doesn't sound very big, consider that it's literally a 50 percent higher rate that directly affects the lifespan of our planet as a livable place.
There is also a cascading effect, because bridgmanite turns into a different mineral called post-perovskite as it cools. That means more bridgmanite cools faster than we thought due to the transfer of heat, which in turn means more post-perovskite. And the post-perovskite conducts heat even better, whisking it away from the core and into the mantle.
Murakami says there's no way to pin down the exact timeline of this cooling; we just know it will be sooner than experts would have previously guesstimated. But he also points out that we have role models of a sort: "Our results could give us a new perspective on the evolution of the Earth's dynamics," Murakami says. "They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected."
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