File photo: A photo taken by Expedition 46 flight engineer Tim Peake of the European Space Agency (ESA) on board the International Space Station shows Italy, the Alps and the Mediterranean sea on January 25, 2016. (REUTERS/NASA/Tim Peake)
One day, about a billion years ago, earth’s inner core had a growth spurt. The molten ball of liquid metal in the middle of our planet is quickly crystallized by lowering the temperature, growing steadily outward until reaching the about 760 miles (1,220 km) in diameter, which it is thought to expand today.
That is the conventional story of the inner core of creation, anyway. But according to a new paper this week published online in the journal Earth and Planetary Science Letters, that story is impossible.
In the paper, the researchers stated that the standard model of how the core of the Earth formed is missing a crucial detail about the metal crystallization: a mandatory, by the enormous decrease of the temperature which would be extremely difficult to achieve a core pressure. [6 Visions of Earth’s Core]
Weirder still, the researchers said that, once you have an account for this missing data, the science seems to suggest that the Earth’s core would not need to exist.
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The paradox at the center of our planet
“Everyone, ourselves included, seemed to be missing this major problem,” study author Steven Hauck, a professor of Earth, Environmental and Planetary Sciences at Case Western Reserve University in Ohio, said in a statement. Namely, they were missing “that metal does not begin to crystallize immediately, unless there is something in there that lowers the barrier a lot.”
In chemistry, this extra energy is known as the nucleation barrier: the point at which a composite visible changes of the thermodynamic phase. Liquid water, for example, freezes into a solid at the familiar 32 degrees Fahrenheit (0 degrees Celsius). If you’ve ever made ice cubes at home, you know that even the water stored in her freezing may take several hours to fully crystallize. To speed up the process, you should expose the water significantly colder temperatures (this is the so-called “hypothermia”) or expose it to an already-solid piece of ice to lower the nucleation barrier, reducing the amount of cooling needed.
Hypothermia is easy to achieve for a single ice cube, but for the Earth is gigantic inner core, things are a little more difficult, the researchers said.
“The pressure of the core, it would have to cool 1,000 degrees Kelvin[726 degrees C or 1,340 degrees F] or more below the melting temperature to crystallize spontaneously out of pure liquid,” Hauck told Live Science. “And that’s a lot of cool, especially because at this time the scientific community thought that the Earth cools down maybe about 100 degrees K per billion years.”
According to this model, “the inner core would not need to exist, because it couldn’t have been supercooled to such a degree,” study author Jim Van Orman, a professor of Earth, Environmental and Planetary Sciences at Case Western, told Science. The molten core of the nucleation barrier, he said, should have lowered a different way — but how?
The core of the problem
In their paper, the researchers proposed one possibility: Maybe a huge gold nugget of solid metal alloy to fall from the mantle and dipped in the liquid core. If an ice cube dropping into a glass, slowly freezing water, this solid piece of metal could have reduced the core of the nucleation barrier is enough to kick-start a rapid crystallization.
There is a big caveat, however: It would be a truly massive amount of metal work.
“To be released in the core and then it is all the way down to the center of the Earth without having to dissolve … this drop should be on the order of about 10 km (6.2 miles] in radius,” Orman said. That means a diameter about the length of the island of Manhattan.
The Case Western researchers said that, while they have the benefit of this new statement on the conventional model, they are excited for members of the scientific community to weigh in with theories of their own.
“We’ve talked about what the ideas are unbelievable, and we have proposed an idea that may be plausible,” Hauck said. “If it happened that way, it is possible that some signature of that event can be detected by means of seismic surveys. The study of the centermost part of the planet is about the most difficult to access with these waves, so it will take some time.”
Hopefully we can look forward to a response within the next billion years.
Originally published on Live Science.