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Even though it is hotter than the surface of the Sun, the crystallized iron core of the Earth remains solid. A new study from KTH Royal Institute of Technology may finally settle a longstanding debate over how that’s possible, as well as why seismic waves travel at higher speeds between the planet’s poles than through the equator.
Spinning within Earth’s molten core is a crystal ball – actually a mass formation of almost pure crystallized iron – nearly the size of the moon. Understanding this strange, unobservable feature of our planet depends on knowing the atomic structure of these crystals – something scientists have been trying to do for years.
As with all metals, the atomic-scale crystal structures of iron change depending on the temperature and pressure the metal is exposed to. Atoms are packed into variations of cubic, as well as hexagonal formations. At room temperatures and normal atmospheric pressure, iron is in what is known as a body-centered cubic (BCC) phase, which is a crystal architecture with eight corner points and a center point. But at extremely high pressure the crystalline structures transform into 12-point hexagonal forms, or a close packed (HCP) phase.
At Earth’s core, where pressure is 3.5 million times higher than surface pressure – and temperatures are some 6,000 degrees higher – scientists have proposed that the atomic architecture of iron must be hexagonal. Whether BCC iron exists in the center of the Earth has been debated for the last 30 years, and a recent 2014 study ruled it out, arguing that BCC would be unstable under such conditions.
However, in a recent study published in Nature Geosciences, researchers at KTH found that iron at Earth’s core is indeed in the BCC phase. Anatoly Belonoshko, a researcher in theDepartment of Physics at KTH, says that when the researchers looked into larger computational samples of iron than studied previously, characteristics of the BCC iron that were thought to render it unstable wound up doing just the opposite.
Spinning within Earth’s molten core is a crystal ball – actually a mass formation of almost pure crystallized iron – nearly the size of the moon. Understanding this strange, unobservable feature of our planet depends on knowing the atomic structure of these crystals – something scientists have been trying to do for years.
As with all metals, the atomic-scale crystal structures of iron change depending on the temperature and pressure the metal is exposed to. Atoms are packed into variations of cubic, as well as hexagonal formations. At room temperatures and normal atmospheric pressure, iron is in what is known as a body-centered cubic (BCC) phase, which is a crystal architecture with eight corner points and a center point. But at extremely high pressure the crystalline structures transform into 12-point hexagonal forms, or a close packed (HCP) phase.
At Earth’s core, where pressure is 3.5 million times higher than surface pressure – and temperatures are some 6,000 degrees higher – scientists have proposed that the atomic architecture of iron must be hexagonal. Whether BCC iron exists in the center of the Earth has been debated for the last 30 years, and a recent 2014 study ruled it out, arguing that BCC would be unstable under such conditions.
However, in a recent study published in Nature Geosciences, researchers at KTH found that iron at Earth’s core is indeed in the BCC phase. Anatoly Belonoshko, a researcher in theDepartment of Physics at KTH, says that when the researchers looked into larger computational samples of iron than studied previously, characteristics of the BCC iron that were thought to render it unstable wound up doing just the opposite.
New theory explains how Earth's inner core remains solid despite extreme heat
Even though it is hotter than the surface of the Sun, the crystallized iron core of the Earth remains solid. A new study may finally settle a longstanding debate over how that's possible, as well as why seismic waves travel at higher speeds between the planet's poles than through the equator.
www.sciencedaily.com
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