Radioactive Potassium May Be Major Heat Source in Earth's Core

http://www.berkeley.edu/news/media/r.../10_heat.shtml

Radioactive potassium may be major heat source in Earth's core

By Robert Sanders, Media Relations
UC Berkeley News
10 December 2003

BERKELEY - Radioactive potassium, common enough on Earth to make potassium-rich
bananas one of the "hottest" foods around, appears also to be a substantial
source of heat in the Earth's core, according to recent experiments by
University of California, Berkeley, geophysicists.

Radioactive potassium, uranium and thorium are thought to be the three main
sources of heat in the Earth's interior, aside from that generated by the
formation of the planet. Together, the heat keeps the mantle actively
churning and the core generating a protective magnetic field.

But geophysicists have found much less potassium in the Earth's crust and
mantle than would be expected based on the composition of rocky meteors that
supposedly formed the Earth. If, as some have proposed, the missing
potassium resides in the Earth's iron core, how did an element as light
as potassium get there, especially since iron and potassium don't mix?

Kanani Lee, who recently earned her Ph.D. from UC Berkeley, and UC Berkeley
professor of earth and planetary science Raymond Jeanloz have discovered a
possible answer. They've shown that at the high pressures and temperatures
in the Earth's interior, potassium can form an alloy with iron never before
observed. During the planet's formation, this potassium-iron alloy could
have sunk to the core, depleting potassium in the overlying mantle and crust
and providing a radioactive potassium heat source in addition to that
supplied by uranium and thorium in the core.

Lee created the new alloy by squeezing iron and potassium between the tips
of two diamonds to temperatures and pressures characteristic of 600-700
kilometers below the surface - 2,500 degrees Celsius and nearly 4 million
pounds per square inch, or a quarter of a million times atmospheric
pressure.

"Our new findings indicate that the core may contain as much as 1,200 parts
per million potassium -just over one tenth of one percent," Lee said. "This
amount may seem small, and is comparable to the concentration of
radioactive potassium naturally present in bananas. Combined over the
entire mass of the Earth's core, however, it can be enough to provide
one-fifth of the heat given off by the Earth."

Lee and Jeanloz will report their findings on Dec. 10, at the American
Geophysical Union meeting in San Francisco, and in an article accepted
for publication in Geophysical Research Letters.

"With one experiment, Lee and Jeanloz demonstrated that potassium may be
an important heat source for the geodynamo, provided a way out of some
troublesome aspects of the core's thermal evolution, and further
demonstrated that modern computational mineral physics not only
complements experimental work, but that it can provide guidance to
fruitful experimental explorations," said Mark Bukowinski, professor of
earth and planetary science at UC Berkeley, who predicted the unusual
alloy in the mid-1970s.

Geophysicist Bruce Buffett of the University of Chicago cautions that
more experiments need to be done to show that iron can actually pull
potassium away from the silicate rocks that dominate in the
Earth's mantle.

"They proved it would be possible to dissolve potassium into liquid iron,"
Buffet said. "Modelers need heat, so this is one source, because the
radiogenic isotope of potassium can produce heat and that can help power
convection in the core and drive the magnetic field. They proved it
could go in. What's important is how much is pulled out of the silicate.
There's still work to be done "

If a significant amount of potassium does reside in the Earth's core, this
would clear up a lingering question - why the ratio of potassium to uranium
in stony meteorites (chondrites), which presumably coalesced to form the
Earth, is eight times greater than the observed ratio in the Earth's
crust. Though some geologists have asserted that the missing potassium
resides in the core, there was no mechanism by which it could have reached
the core. Other elements like oxygen and carbon form compounds or alloys
with iron and presumably were dragged down by iron as it sank to the
core. But at normal temperature and pressure, potassium does not associate
with iron.

Others have argued that the missing potassium boiled away during the early,
molten stage of Earth's evolution.

The demonstration by Lee and Jeanloz that potassium can dissolve in iron to
form an alloy provides an explanation for the missing potassium.

"Early in Earth's history, the interior temperature and pressure would not
have been high enough to make this alloy," Lee said. "But as more and more
meteorites piled on, the pressure and temperature would have increased to
the point where this alloy could form."

The existence of this high-pressure alloy was predicted by Bukowinski in the
mid-1970s. Using quantum mechanical arguments, he suggested that high
pressure would squeeze potassium's lone outer electron into a lower shell,
making the atom resemble iron and thus more likely to alloy with
iron.

More recent quantum mechanical calculations using improved techniques,
conducted with Gerd Steinle-Neumann at the Universität
Bayreuth's Bayerisches Geoinstitüt, confirmed the new experimental
measurements.

"This really replicates and verifies the earlier calculations 26 years ago
and provides a physical explanation for our experimental results," Jeanloz
said.

The Earth is thought to have formed from the collision of many rocky
asteroids, perhaps hundreds of kilometers in diameter, in the early solar
system. As the proto-Earth gradually bulked up, continuing asteroid
collisions and gravitational collapse kept the planet molten. Heavier
elements - in particular iron - would have sunk to the core in 10 to 100
million years' time, carrying with it other elements that bind to iron.

Gradually, however, the Earth would have cooled off and become a dead rocky
globe with a cold iron ball at the core if not for the continued release of
heat by the decay of radioactive elements like potassium-40, uranium-238 and
thorium-232, which have half-lives of 1.25 billion, 4 billion and 14
billion years, respectively. About one in every thousand potassium atoms
is radioactive.

The heat generated in the core turns the iron into a convecting dynamo that
maintains a magnetic field strong enough to shield the planet from the solar
wind. This heat leaks out into the mantle, causing convection in the rock
that moves crustal plates and fuels volcanoes.

Balancing the heat generated in the core with the known concentrations of
radiogenic isotopes has been difficult, however, and the missing potassium
has been a big part of the problem. One researcher proposed earlier this
year that sulfur could help potassium associate with iron and provide a
means by which potassium could reach the core.

The experiment by Lee and Jeanloz shows that sulfur is not necessary. Lee
combined pure iron and pure potassium in a diamond anvil cell and squeezed
the small sample to 26 gigapascals of pressure while heating the sample
with a laser above 2,500 Kelvin (4,000 degrees Fahrenheit), which is
above the melting points of both potassium and iron. She conducted this
experiment six times in the high-intensity X-ray beams of two different
accelerators - Lawrence Berkeley National Laboratory's Advanced Light Source
and the Stanford Synchrotron Radiation Laboratory - to obtain
X-ray diffraction images of the samples' internal structure. The images
confirmed that potassium and iron had mixed evenly to form an alloy, much
as iron and carbon mix to form steel alloy.

In the theoretical magma ocean of a proto-Earth, the pressure at a depth
of 400-1,000 kilometers (270-670 miles) would be between 15 and 35
gigapascals and the temperature would be 2,200-3,000 Kelvin, Jeanloz said.

"At these temperatures and pressures, the underlying physics changes and
the electron density shifts, making potassium look more like iron," Jeanloz
said. "At high pressure, the periodic table looks totally different."

"The work by Lee and Jeanloz provides the first proof that potassium is
indeed miscible in iron at high pressures and, perhaps as significantly,
it further vindicates the computational physics that underlies the original
prediction," Bukowinski said. "If it can be further demonstrated that
potassium would enter iron in significant amounts in the presence of
silicate minerals, conditions representative of likely core formation
processes, then potassium could provide the extra heat needed to explain
why the Earth's inner core hasn't frozen to as large a size as the thermal
history of the core suggests it should."

Jeanloz is excited by the fact that theoretical calculations are now not
only explaining experimental findings at high pressure, but also predicting
structures.

"We need theorists to identify interesting problems, not only check our
results after the experiment," he said. "That's happening now. In the past
half a dozen years, theorists have been making predictions that
experimentalists are willing to spend a few years to demonstrate."

The work was funded by the National Science Foundation and the Department of
Energy.

(Ron Baalke) wrote in message ...
http://www.berkeley.edu/news/media/r.../10_heat.shtml

Radioactive potassium may be major heat source in Earth's core

By Robert Sanders, Media Relations
UC Berkeley News
10 December 2003

BERKELEY - Radioactive potassium, common enough on Earth to make potassium-rich
bananas one of the "hottest" foods around, appears also to be a substantial
source of heat in the Earth's core, according to recent experiments by
University of California, Berkeley, geophysicists.

Radioactive potassium, uranium and thorium are thought to be the three main
sources of heat in the Earth's interior, aside from that generated by the
formation of the planet. Together, the heat keeps the mantle actively
churning and the core generating a protective magnetic field.

But geophysicists have found much less potassium in the Earth's crust and
mantle than would be expected based on the composition of rocky meteors that
supposedly formed the Earth. If, as some have proposed, the missing
potassium resides in the Earth's iron core, how did an element as light
as potassium get there, especially since iron and potassium don't mix?

Kanani Lee, who recently earned her Ph.D. from UC Berkeley, and UC Berkeley
professor of earth and planetary science Raymond Jeanloz have discovered a
possible answer. They've shown that at the high pressures and temperatures
in the Earth's interior, potassium can form an alloy with iron never before
observed. During the planet's formation, this potassium-iron alloy could
have sunk to the core, depleting potassium in the overlying mantle and crust
and providing a radioactive potassium heat source in addition to that
supplied by uranium and thorium in the core.

Lee created the new alloy by squeezing iron and potassium between the tips
of two diamonds to temperatures and pressures characteristic of 600-700
kilometers below the surface - 2,500 degrees Celsius and nearly 4 million
pounds per square inch, or a quarter of a million times atmospheric
pressure.

"Our new findings indicate that the core may contain as much as 1,200 parts
per million potassium -just over one tenth of one percent," Lee said. "This
amount may seem small, and is comparable to the concentration of
radioactive potassium naturally present in bananas. Combined over the
entire mass of the Earth's core, however, it can be enough to provide
one-fifth of the heat given off by the Earth."

Lee and Jeanloz will report their findings on Dec. 10, at the American
Geophysical Union meeting in San Francisco, and in an article accepted
for publication in Geophysical Research Letters.

"With one experiment, Lee and Jeanloz demonstrated that potassium may be
an important heat source for the geodynamo, provided a way out of some
troublesome aspects of the core's thermal evolution, and further
demonstrated that modern computational mineral physics not only
complements experimental work, but that it can provide guidance to
fruitful experimental explorations," said Mark Bukowinski, professor of
earth and planetary science at UC Berkeley, who predicted the unusual
alloy in the mid-1970s.

Geophysicist Bruce Buffett of the University of Chicago cautions that
more experiments need to be done to show that iron can actually pull
potassium away from the silicate rocks that dominate in the
Earth's mantle.

"They proved it would be possible to dissolve potassium into liquid iron,"
Buffet said. "Modelers need heat, so this is one source, because the
radiogenic isotope of potassium can produce heat and that can help power
convection in the core and drive the magnetic field. They proved it
could go in. What's important is how much is pulled out of the silicate.
There's still work to be done "

If a significant amount of potassium does reside in the Earth's core, this
would clear up a lingering question - why the ratio of potassium to uranium
in stony meteorites (chondrites), which presumably coalesced to form the
Earth, is eight times greater than the observed ratio in the Earth's
crust. Though some geologists have asserted that the missing potassium
resides in the core, there was no mechanism by which it could have reached
the core. Other elements like oxygen and carbon form compounds or alloys
with iron and presumably were dragged down by iron as it sank to the
core. But at normal temperature and pressure, potassium does not associate
with iron.

Others have argued that the missing potassium boiled away during the early,
molten stage of Earth's evolution.

The demonstration by Lee and Jeanloz that potassium can dissolve in iron to
form an alloy provides an explanation for the missing potassium.

"Early in Earth's history, the interior temperature and pressure would not
have been high enough to make this alloy," Lee said. "But as more and more
meteorites piled on, the pressure and temperature would have increased to
the point where this alloy could form."

The existence of this high-pressure alloy was predicted by Bukowinski in the
mid-1970s. Using quantum mechanical arguments, he suggested that high
pressure would squeeze potassium's lone outer electron into a lower shell,
making the atom resemble iron and thus more likely to alloy with
iron.

More recent quantum mechanical calculations using improved techniques,
conducted with Gerd Steinle-Neumann at the Universität
Bayreuth's Bayerisches Geoinstitüt, confirmed the new experimental
measurements.

"This really replicates and verifies the earlier calculations 26 years ago
and provides a physical explanation for our experimental results," Jeanloz
said.

The Earth is thought to have formed from the collision of many rocky
asteroids, perhaps hundreds of kilometers in diameter, in the early solar
system. As the proto-Earth gradually bulked up, continuing asteroid
collisions and gravitational collapse kept the planet molten. Heavier
elements - in particular iron - would have sunk to the core in 10 to 100
million years' time, carrying with it other elements that bind to iron.

Gradually, however, the Earth would have cooled off and become a dead rocky
globe with a cold iron ball at the core if not for the continued release of
heat by the decay of radioactive elements like potassium-40, uranium-238 and
thorium-232, which have half-lives of 1.25 billion, 4 billion and 14
billion years, respectively. About one in every thousand potassium atoms
is radioactive.

The heat generated in the core turns the iron into a convecting dynamo that
maintains a magnetic field strong enough to shield the planet from the solar
wind. This heat leaks out into the mantle, causing convection in the rock
that moves crustal plates and fuels volcanoes.

Balancing the heat generated in the core with the known concentrations of
radiogenic isotopes has been difficult, however, and the missing potassium
has been a big part of the problem. One researcher proposed earlier this
year that sulfur could help potassium associate with iron and provide a
means by which potassium could reach the core.

The experiment by Lee and Jeanloz shows that sulfur is not necessary. Lee
combined pure iron and pure potassium in a diamond anvil cell and squeezed
the small sample to 26 gigapascals of pressure while heating the sample
with a laser above 2,500 Kelvin (4,000 degrees Fahrenheit), which is
above the melting points of both potassium and iron. She conducted this
experiment six times in the high-intensity X-ray beams of two different
accelerators - Lawrence Berkeley National Laboratory's Advanced Light Source
and the Stanford Synchrotron Radiation Laboratory - to obtain
X-ray diffraction images of the samples' internal structure. The images
confirmed that potassium and iron had mixed evenly to form an alloy, much
as iron and carbon mix to form steel alloy.

In the theoretical magma ocean of a proto-Earth, the pressure at a depth
of 400-1,000 kilometers (270-670 miles) would be between 15 and 35
gigapascals and the temperature would be 2,200-3,000 Kelvin, Jeanloz said.

"At these temperatures and pressures, the underlying physics changes and
the electron density shifts, making potassium look more like iron," Jeanloz
said. "At high pressure, the periodic table looks totally different."

"The work by Lee and Jeanloz provides the first proof that potassium is
indeed miscible in iron at high pressures and, perhaps as significantly,
it further vindicates the computational physics that underlies the original
prediction," Bukowinski said. "If it can be further demonstrated that
potassium would enter iron in significant amounts in the presence of
silicate minerals, conditions representative of likely core formation
processes, then potassium could provide the extra heat needed to explain
why the Earth's inner core hasn't frozen to as large a size as the thermal
history of the core suggests it should."

Jeanloz is excited by the fact that theoretical calculations are now not
only explaining experimental findings at high pressure, but also predicting
structures.

"We need theorists to identify interesting problems, not only check our
results after the experiment," he said. "That's happening now. In the past
half a dozen years, theorists have been making predictions that
experimentalists are willing to spend a few years to demonstrate."

The work was funded by the National Science Foundation and the Department of
Energy.


A heat inside the earth is caused. And to search for the source is a
scientist's experiment. So take the earth and reduce the interior
temperature.

And if the right cause is selected, the right cause was discovered.

And to answer the question without experiment other then complex
conjecture is a lie.

I believe it is gravity heated. And comet temperature photographs
from the comet's trip arround the sun, comfirm this experiment.

The photographs depict the inside heating only!!!

What other proof is necessary?

Is Newton's Gravity incomplete? My, my.

Douglas Eagleson
Gaithersburg, MD USA

"Douglas Eagleson" wrote in message

A heat inside the earth is caused. And to search for the source is a
scientist's experiment. So take the earth and reduce the interior
temperature.

And if the right cause is selected, the right cause was discovered.

And to answer the question without experiment other then complex
conjecture is a lie.

I believe it is gravity heated. And comet temperature photographs
from the comet's trip arround the sun, comfirm this experiment.

The photographs depict the inside heating only!!!

What other proof is necessary?

Is Newton's Gravity incomplete? My, my.

Douglas Eagleson
Gaithersburg, MD USA

Clearly this is a satire on something.
does anyone know what?

In the beginning there was nothing.

Then it exploded and reached immense temperatures.

And since then everything has been cooling.

And that is why the earth has a molten core.

Bananas are therefore obviously bad for your health.

Ron Baalke wrote:
snip

In article ,
says...

"Douglas Eagleson" wrote in message

A heat inside the earth is caused. And to search for the source is a
scientist's experiment. So take the earth and reduce the interior
temperature.

And if the right cause is selected, the right cause was discovered.

And to answer the question without experiment other then complex
conjecture is a lie.

I believe it is gravity heated. And comet temperature photographs
from the comet's trip arround the sun, comfirm this experiment.

The photographs depict the inside heating only!!!

What other proof is necessary?

Is Newton's Gravity incomplete? My, my.

Douglas Eagleson
Gaithersburg, MD USA

Clearly this is a satire on something.
does anyone know what?

While it could be a satire of an alt.sci loon, I suspect it simply is a
loon.

Marc

On a sunny day (Tue, 16 Dec 2003 18:00:48 +1100) it happened Louis Hissink
wrote in
:

In the beginning there was nothing.
In the beginning there was nothing.
Then God created light,
there was still nothing, but you could see it a lot better.

"Marc 182" wrote in message
t...
While it could be a satire of an alt.sci loon, I suspect it simply is a
loon.

The fruitcakes always appear before Christmas.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/

"Chuck Taylor" wrote in message
...
"Marc 182" wrote in message
t...
While it could be a satire of an alt.sci loon, I suspect it simply is a
loon.

The fruitcakes always appear before Christmas.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/


I think its a loon going to talk about EE again.

"Jan Panteltje" wrote in message
...
On a sunny day (Tue, 16 Dec 2003 18:00:48 +1100) it happened Louis Hissink
wrote in
:

In the beginning there was nothing.
In the beginning there was nothing.
Then God created light,
there was still nothing, but you could see it a lot better.


FREAKIN' LOL

"Ron Baalke" wrote in message
...
http://www.berkeley.edu/news/media/r.../10_heat.shtml

Radioactive potassium may be major heat source in Earth's core

By Robert Sanders, Media Relations
UC Berkeley News
10 December 2003

BERKELEY - Radioactive potassium, common enough on Earth to make
potassium-rich
bananas one of the "hottest" foods around, appears also to be a
substantial
source of heat in the Earth's core, according to recent experiments by
University of California, Berkeley, geophysicists.

Radioactive potassium, uranium and thorium are thought to be the three
main
sources of heat in the Earth's interior, aside from that generated by the
formation of the planet. Together, the heat keeps the mantle actively
churning and the core generating a protective magnetic field.

But geophysicists have found much less potassium in the Earth's crust and
mantle than would be expected based on the composition of rocky meteors
that
supposedly formed the Earth. If, as some have proposed, the missing
potassium resides in the Earth's iron core, how did an element as light
as potassium get there, especially since iron and potassium don't mix?

Kanani Lee, who recently earned her Ph.D. from UC Berkeley, and UC
Berkeley
professor of earth and planetary science Raymond Jeanloz have discovered a
possible answer. They've shown that at the high pressures and temperatures
in the Earth's interior, potassium can form an alloy with iron never
before
observed. During the planet's formation, this potassium-iron alloy could
have sunk to the core, depleting potassium in the overlying mantle and
crust
and providing a radioactive potassium heat source in addition to that
supplied by uranium and thorium in the core.

Lee created the new alloy by squeezing iron and potassium between the tips
of two diamonds to temperatures and pressures characteristic of 600-700
kilometers below the surface - 2,500 degrees Celsius and nearly 4 million
pounds per square inch, or a quarter of a million times atmospheric
pressure.

"Our new findings indicate that the core may contain as much as 1,200
parts
per million potassium -just over one tenth of one percent," Lee said.
"This
amount may seem small, and is comparable to the concentration of
radioactive potassium naturally present in bananas. Combined over the
entire mass of the Earth's core, however, it can be enough to provide
one-fifth of the heat given off by the Earth."

Lee and Jeanloz will report their findings on Dec. 10, at the American
Geophysical Union meeting in San Francisco, and in an article accepted
for publication in Geophysical Research Letters.

"With one experiment, Lee and Jeanloz demonstrated that potassium may be
an important heat source for the geodynamo, provided a way out of some
troublesome aspects of the core's thermal evolution, and further
demonstrated that modern computational mineral physics not only
complements experimental work, but that it can provide guidance to
fruitful experimental explorations," said Mark Bukowinski, professor of
earth and planetary science at UC Berkeley, who predicted the unusual
alloy in the mid-1970s.

Geophysicist Bruce Buffett of the University of Chicago cautions that
more experiments need to be done to show that iron can actually pull
potassium away from the silicate rocks that dominate in the
Earth's mantle.

"They proved it would be possible to dissolve potassium into liquid iron,"
Buffet said. "Modelers need heat, so this is one source, because the
radiogenic isotope of potassium can produce heat and that can help power
convection in the core and drive the magnetic field. They proved it
could go in. What's important is how much is pulled out of the silicate.
There's still work to be done "

If a significant amount of potassium does reside in the Earth's core, this
would clear up a lingering question - why the ratio of potassium to
uranium
in stony meteorites (chondrites), which presumably coalesced to form the
Earth, is eight times greater than the observed ratio in the Earth's
crust. Though some geologists have asserted that the missing potassium
resides in the core, there was no mechanism by which it could have reached
the core. Other elements like oxygen and carbon form compounds or alloys
with iron and presumably were dragged down by iron as it sank to the
core. But at normal temperature and pressure, potassium does not associate
with iron.

Others have argued that the missing potassium boiled away during the
early,
molten stage of Earth's evolution.

The demonstration by Lee and Jeanloz that potassium can dissolve in iron
to
form an alloy provides an explanation for the missing potassium.

"Early in Earth's history, the interior temperature and pressure would not
have been high enough to make this alloy," Lee said. "But as more and more
meteorites piled on, the pressure and temperature would have increased to
the point where this alloy could form."

The existence of this high-pressure alloy was predicted by Bukowinski in
the
mid-1970s. Using quantum mechanical arguments, he suggested that high
pressure would squeeze potassium's lone outer electron into a lower shell,
making the atom resemble iron and thus more likely to alloy with
iron.

More recent quantum mechanical calculations using improved techniques,
conducted with Gerd Steinle-Neumann at the Universität
Bayreuth's Bayerisches Geoinstitüt, confirmed the new experimental
measurements.

"This really replicates and verifies the earlier calculations 26 years ago
and provides a physical explanation for our experimental results," Jeanloz
said.

The Earth is thought to have formed from the collision of many rocky
asteroids, perhaps hundreds of kilometers in diameter, in the early solar
system. As the proto-Earth gradually bulked up, continuing asteroid
collisions and gravitational collapse kept the planet molten. Heavier
elements - in particular iron - would have sunk to the core in 10 to 100
million years' time, carrying with it other elements that bind to iron.

Gradually, however, the Earth would have cooled off and become a dead
rocky
globe with a cold iron ball at the core if not for the continued release
of
heat by the decay of radioactive elements like potassium-40, uranium-238
and
thorium-232, which have half-lives of 1.25 billion, 4 billion and 14
billion years, respectively. About one in every thousand potassium atoms
is radioactive.

The heat generated in the core turns the iron into a convecting dynamo
that
maintains a magnetic field strong enough to shield the planet from the
solar
wind. This heat leaks out into the mantle, causing convection in the rock
that moves crustal plates and fuels volcanoes.

Balancing the heat generated in the core with the known concentrations of
radiogenic isotopes has been difficult, however, and the missing potassium
has been a big part of the problem. One researcher proposed earlier this
year that sulfur could help potassium associate with iron and provide a
means by which potassium could reach the core.

The experiment by Lee and Jeanloz shows that sulfur is not necessary. Lee
combined pure iron and pure potassium in a diamond anvil cell and squeezed
the small sample to 26 gigapascals of pressure while heating the sample
with a laser above 2,500 Kelvin (4,000 degrees Fahrenheit), which is
above the melting points of both potassium and iron. She conducted this
experiment six times in the high-intensity X-ray beams of two different
accelerators - Lawrence Berkeley National Laboratory's Advanced Light
Source
and the Stanford Synchrotron Radiation Laboratory - to obtain
X-ray diffraction images of the samples' internal structure. The images
confirmed that potassium and iron had mixed evenly to form an alloy, much
as iron and carbon mix to form steel alloy.

In the theoretical magma ocean of a proto-Earth, the pressure at a depth
of 400-1,000 kilometers (270-670 miles) would be between 15 and 35
gigapascals and the temperature would be 2,200-3,000 Kelvin, Jeanloz said.

"At these temperatures and pressures, the underlying physics changes and
the electron density shifts, making potassium look more like iron,"
Jeanloz
said. "At high pressure, the periodic table looks totally different"

"The work by Lee and Jeanloz provides the first proof that potassium is
indeed miscible in iron at high pressures and, perhaps as significantly,
it further vindicates the computational physics that underlies the
original
prediction," Bukowinski said. "If it can be further demonstrated that
potassium would enter iron in significant amounts in the presence of
silicate minerals, conditions representative of likely core formation
processes, then potassium could provide the extra heat needed to explain
why the Earth's inner core hasn't frozen to as large a size as the thermal
history of the core suggests it should."

Jeanloz is excited by the fact that theoretical calculations are now not
only explaining experimental findings at high pressure, but also
predicting
structures.

"We need theorists to identify interesting problems, not only check our
results after the experiment," he said. "That's happening now. In the past
half a dozen years, theorists have been making predictions that
experimentalists are willing to spend a few years to demonstrate."

The work was funded by the National Science Foundation and the Department
of
Energy.

Let's do a little review of what is known about the interior of the earth
for
those who haven't taken basic geology. There are several ways to determine
the
composition of the mantle and core. Let's look at those methods:

(The following narrative comes straight from Ehlers and Blatt)

"In order to deduce the composition of the inaccessible mantle and core, a
number of different types of evidence have been used. One of these is
meteorites. It is generally accepted that meteoritic bodies were created at
about the same time as the earth from gravitational collapse of the same
materials that comprise the earth. The paths of meteorites indicate that
they come from the asteroid belt (athough we now know that some have come
from Mars and perhaps elsewhere) and follow elliptical orbits that can
result in collision with
the earth. Although meteorites exist in a wide variety of chemical an
mineralogical types, they can be subdivided into two major varieties - the
stony meteorites and the iron meteorites. The iron meteorites consist of
mostly iron with minor amounts of nickel and iron sufide (interestingly,
there is very little if any potassium in these meteorites)...

"Stony meteorites, which often contain some iron-nickel alloy, are composed
mainly of silicates. The relative abundances of nonvolatile elements in the
stones (mg, Si, Ca, Al, and Fe) are similar to those of the sun and other
stars. It is probably not a coincidence that the relative volumes of mantle
and core in the earth (83.5% and 16.2%) are similar to the percentages of
stony to iron-nickel material in observed meteorite falls. Using
meteorites as a basis, mantle compositions are estimated to be about 90%
SiO2, MgO, and FeO; that is, the mantle is composed of ultramafic material.
The remaining 10% is mainly Al2O3, CaO, and NaO.

"An additional source of information about the types of rock within the
earth comes from xenoliths and xenocryts. Vertically ascending magma marry
carry fragments from the magmatic source area (cognate xenoliths), or
fragments acquired from all rock at higher levels. If the fragments are
brought from the greatest depths at a slow rate of ascent, it is likely that
they will undergo change during the rise. Such changes may include reaction
with the surrounding melt, or conversion of high-temperature minerals to
low-temperature equivalents. Ideally, then, in order to have samples truly
representative of mineral assemblages characteristic of the mantle and lower
crust, the xenoliths should be brought up rapidly to the surface.
Fortunately, the variety of peridotite known as kimberlite furnishes such a
mechanism. Kimberlites contain diamonds (which are also found in stony
meteorites), known from laboratory experiments to be stable at very high
pressures. It is, therefore, assumed that kimberlitic magma originates at
very great depth (150-300 Km). Kimberlite magmas reach the surface very
rapidly by an explosive process, and commonly contain xenoliths brought from
all levels; those of deep origin are generally able to maintain the high
pressure assemblages and phase compositions characteristics of the upper
mantle. The most common of these xenoliths are peridotites and eclogites.
Recall that peridotite is a rock consisting mainly of olivine ((Mg,
FeO2SiO4) and pyroxene (calcium, magnesium silicates of varying composition)
***note that none of these minerals contain potasium except in minute
amounts
possibly due to substitutions***, whereas eclogite(containing pyroxene and
garnet)
is the high pressure equivalent of basalt. The mineralogy of the peridotites
is similar
to the mantle compositions deduced by the meteoritic research....

"Another approach to mantle mineralogy has been through high-pressure
experimentation. A variety of materials have been synthesized that fulfill
two basic criteria. The first is that they have appropriate densities for
the various pressure-tempterature conditions of the mantle. Secondly, their
compositions must be such that they furnish basaltic liquids when partially
melted (20%-40% of the total) under mantle conditions. This second
condition is necessary because basaltic melts are known to be produced by
partial melting processes in the upper mantle at rift zones. This approach
yields a material that is a variety of peridotite.

"A typical phase composition of the mantle by weight percentage is as
follows:

SiO2 - 45.20
TiO2 - 0.71
Al2O3 - 3.54
Cr2O3 - 0.43
Fe2O3 - 0.48
FeO - 8.04MnO - 0.14
NiO - 0.20
MgO - 3.08
Na2O - 0.57
K2O - 0.13"
__________________________________________________ __

A typical elemental composition of the crust, by comparison:

Oxygen - 46.6
Silicon - 27.7
Aluminum - 8.1
Iron - 5.0
Calcium - 3.6
Sodium - 2.8
Potassium - 2.6
Magnesium - 2.1
All others - 1.5


Note that the mantle contains very little potasium. Also note that
only traces of potassium phases are identified in the mantle (0.13%). In
addition,
practically no potassium phases are identified in meteorites (neither in
stony
meteorites, nor, more importantly for the purposes of this discussion, in
iron-nickel meteorites). The abundance of potassium in the crust is an
order of
magnitude greater than that seen in the mantle. In contrast, 20 mineral
groups are
recognized in the earth's crust which contain substantial quantities of
potassium. Since
we do know with reasonable assurance that all the main body of oceanic
crustal basalt is derived from a process of partial melting of the
underlying mantle, and are composed of mineral phases that are potassium
poor, it stands to reason that the bulk of the potassium is found in the
continental crust. And as it so happens, this is the case. All of the 20
mineral groups which are known contain potassium are found in continental
crust,
many exclusively so. Potassium-rich minerals make up about 25% of the
continental crust.

This data leads to the conclusion that the early earth had differentiated
such that the heavier elements are contained within the core, while the
phases become progressively lighter as one approaches the surface, in
agreement with long-standing theory.

Although high-pressure experimentation if very useful in determining what is
possible under conditions of extreme pressure and temperature deep within
the earth, it is by no means useful to conclude that since potassium and
iron are miscible, and can form an alloy under the conditions that exist at
the
core, as demonstrated in the exeriments discussed in the original post. It
is certainly a leap of faith to then come to the conclusion that this alloy
actually exists at the
core, when all other evidence, meteoritic, and mineralogic, does no support
such a conclusion. While it is an interesting prospect that an
iron-potassium
alloy CAN exist at the conditions found at the core, the experiment has not
shown
that that such an alloy has a high probability of actually being present in
quantity at the core.
Given the abundances of potassium known to exist elsewhere within the planet
(especially within the continental crust), the lack of evidence for the
existence of
this alloy within meteorites, and the lack of evidence that potassium exists
or has ever
existed in quantity at depth within the earth, it is highly unlikely that
such an alloy will be
found to exist in abundance within the core.

- George