This is important and the central iron core was identified twenty years ago. Now we have an additional core within the apparent iron crystalline structure that is also crystalline but oriented east west rather than north south. I would expect a different element and that may well be nickel.
Again we are at the limits of our knowledge here.
What is important is that such an object will have a different gravity signature that brings into question our own assumptions regarding gravity as well.
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The Earth’s inner core has an inner core of its own, with crystals aligned in a different direction.
CHAMPAIGN, Ill. — Seismic waves are helping scientists to plumb the world’s deepest mystery: the planet’s inner core.
http://news.illinois.edu/news/15/0209innercore_XiaodongSong.html
Thanks to a novel application of earthquake-reading
technology, a research team at the University of Illinois and colleagues
at Nanjing University in China have found that the Earth’s inner core
has an inner core of its own, which has surprising properties that
could reveal information about our planet.
Led by Xiaodong Song, a professor of geology
at the U. of I., and visiting postdoctoral researcher Tao Wang, the
team published its work in the journal Nature Geoscience on Feb. 9.
“Even though the inner core is small – smaller than the moon – it has
some really interesting features,” said Song. “It may tell us about
how our planet formed, its history, and other dynamic processes of the
Earth. It shapes our understanding of what’s going on deep inside the
Earth.”
Researchers use seismic waves from earthquakes to scan below
the planet’s surface, much like doctors use ultrasound to see inside
patients. The team used a technology that gathers data not from the
initial shock of an earthquake, but from the waves that resonate in the
earthquake’s aftermath. The earthquake is like a hammer striking a
bell; much like a listener hears the clear tone that resonates after
the bell strike, seismic sensors collect a coherent signal in the
earthquake’s coda.
“It turns out the coherent signal enhanced by the technology is
clearer than the ring itself,” said Song. “The basic idea of the method
has been around for a while, and people have used it for other kinds of
studies near the surface. But we are looking all the way through the
center of the earth.”
Looking through the core revealed a surprise at the center of
the planet – though not of the type envisioned by novelist Jules Verne.
The inner core, once thought to be a solid ball of iron, has
some complex structural properties. The team found a distinct
inner-inner core, about half the diameter of the whole inner core. The
iron crystals in the outer layer of the inner core are aligned
directionally, north-south. However, in the inner-inner core, the iron
crystals point roughly east-west. (See graphic for a visual map of the
inner core.)
Not only are the iron crystals in the inner-inner core
aligned differently, they behave differently from their counterparts in
the outer-inner core. This means that the inner-inner core could be
made of a different type of crystal, or a different phase.
“The fact that we have two regions that are distinctly different may
tell us something about how the inner core has been evolving,” Song
said. “For example, over the history of the earth, the inner core might
have had a very dramatic change in its deformation regime. It might
hold the key to how the planet has evolved. We are right in the center –
literally, the center of the Earth.”
The U.S. National Science Foundation and the National Science Foundation of China supported this work.
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