Exploring the last white spot on Earth

by Staff Writers
Grenoble, France (SPX) Nov 15, 2011

This image shows the heating of a catalyst sample in an "in situ" cell at actual operating conditions. The catalyst is studied using time-resolved X-ray absorption spectroscopy. At ID24, the time resolution can be as short as a few microseconds. Credit: ESRF.

Scientists will soon be exploring matter at temperatures and pressures so extreme it can only be produced for microseconds using powerful pulsed lasers. Matter in such states is present in the Earth’s liquid iron core, 2500 kilometres beneath the surface, and also in elusive "warm dense matter" inside large planets like Jupiter.

A new X-ray beamline ID24 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, allows a new quality of exploration of the last white spot on our globe: the centre of the Earth.

We know surprisingly little about the interior of the Earth. The pressure at the centre can be calculated accurately from the propagation of Earthquake waves, and it is about three and a half million times atmospheric pressure. The temperature at the centre of the Earth, however, is unknown, but it is thought to be roughly as hot as the surface of the sun.

ID24, which was inaugurated today, opens new fields of science, being able to observe like in a time-lapse film sequence many rapid processes, whether laser-heating of iron to 10.000 degrees, charge reactions in new batteries or catalysts cleaning pollutants.

It is the first of eight new beamlines built within the ESRF Upgrade Programme, a 180 million Euros investment over eight years to maintain the world-leading role of the ESRF. ID24 extends the existing capabilities at the ESRF in X-ray absorption spectroscopy to sample volumes twenty times smaller and time resolutions one thousand times better than in the past.

“Scientists can use several other synchrotrons notably in Japan and the U.S for fast X-ray absorption spectroscopy, but it is the microsecond time resolution for single shot acquisition (or experiments) coupled to the micron sized spot that makes ID24 unique worldwide,” says Sakura Pascarelli, beamline responsible scientist for ID24.

“The rebuilt ID24 sets the ESRF apart, and even before the first users have arrived, I am asked to share our technology.”

The Earth’s interior is literally inaccessible and today it is easier to reach Mars than to visit even the base of the Earth’s thin crust.

Scientists can however reproduce the extreme pressure and temperature of a planet’s interior in the laboratory, using diamond anvil cells to squeeze a material and once under pressure, heat it with short, intense laser pulses. However, these samples are not bigger than the size of a speck of dust and remain stable under high temperatures only for very short time, measured in microseconds.

Thanks to new technologies employed at ID24, scientists can now study what happens at extreme conditions, for example when materials undergo a fast chemical reaction or at what temperature a mineral will melt in the interior of a planet. Germanium micro strip detectors enable measurements to be made sequentially and very rapidly (a million in one second) in order not to miss any detail.

A stable, microscopic X-ray beam means they can also be made in two dimensions by scanning across a sample to obtain a map instead of a measurement only at a single point. A powerful infrared spectrometer complements the X-ray detectors for the study of chemical reactions under industrial processing conditions.

Today, geologists want to know whether a chemical reaction exists between the Earth’s mostly liquid core and the rocky mantle surrounding it.

They would like to know the melting temperature of materials other than iron that might be present in the Earth’s core in order to make better models for how the core – which produces the Earth’s magnetic field – works and to understand why the magnetic field changes over time and periodically in Earth’s history, has disappeared and reversed.

We know even less about warm dense matter believed to exist in the core of larger planets, for example Jupiter, which should be even hotter and denser. It can be produced in the laboratory using extremely powerful laser shock pulses compressing and heating a sample.

The dream of revealing the secrets of the electronic and local structure in this state of matter with X-rays is now becoming reality, as ID24 allows to look at sample volumes 10000 times smaller than those at the high power laser facilities, making these experiments possible at the synchrotron using table top lasers.

The ID24 beamline works like an active probe rather than a passive detector, firing an intense beam of X-rays at a sample. It uses a technique called X-ray absorption spectroscopy where the way how atoms of a given chemical element absorb X-rays is studied in fine detail.

From this data not only the abundance of an element can be deducted but also its chemical states and which other atoms, or elements, are in their immediate neighborhood, and how distant they are. In short, a complete picture at the atomic scale of the sample studied is obtained.

In the past weeks, ID24 has been tested with X-ray beams, and it will be open for users from across the world as of May 2012, after the ESRF winter shutdown 2011/12. The date for its inauguration was chosen to coincide with the autumn meeting of the ESRF’s Science Advisory Committee of external experts who played a key role in selecting the science case for ID24 and the other Upgrade Beamlines.

“ID24 opens unchartered territories of scientific exploration, as will the seven other beamlines of the ESRF Upgrade Programme. The economic crisis has hit our budgets hard, and it is not obvious to deliver new opportunities for research and industrial innovation under these circumstances”, says Harald Reichert, ESRF Director of Research.

“I wish to congratulate the project team for extraordinary achievements, and I look forward to seeing some extraordinary new science.”

via Exploring the last white spot on Earth.

Magnetic mysteries of Earth’s Core

30 August 2011 | Last updated at 20:45 ET
By Gaby Hornsby, BBC Horizon

The magnetic field emanating from Earth’s core helps create the Northern Lights

Earthquakes, explosions and observations of Earth’s ever-changing magnetic field are helping scientists open up a new window on the heart of our planet.

When Jules Verne wrote A Journey to the Centre of the Earth over 100 years ago, he imagined a place of glowing crystals and a turbulent sea, complete with prehistoric animals and giant mushrooms.

What was actually beneath our feet was a complete enigma. Even to this day scientists astonishingly know more about the rings of Saturn than they do about the core of our own planet.

But that is beginning to change. “We’re at a golden age in terms of the real discovery of the bulk of the deep Earth,” says seismologist Professor Rick Aster.

And remarkably, not everything Verne imagined was wrong.

Wanting to discover the truth about the centre of our world is as basic a human urge as wondering what is on the Moon, although the latter has proved far easier to explore.

But scientists are also fascinated by the Earth’s core because it is responsible for creating our planet’s magnetic field which is vital to life.

As a tool for navigation, it helps honey bees find their hive, while sea turtles, birds and butterflies use it to migrate over long distances.

The magnetic field also acts as a protective barrier between us and some of the dangers of space, shielding us from radiation in the solar wind.

Physically travelling to the core has proved a non-starter though, because of the rapidly increasing pressures and temperatures.

Even with remote drilling, the deepest we have managed to penetrate is 12km at the Kola Superdeep Borehole in Russia – a measly 0.2% of the way to the centre of the Earth.

Molten metal

But seismology has allowed scientists to sense right into the core of the planet. The seismic waves generated during major earthquakes travel from one side of the Earth to the other, allowing scientists to build up a picture of the interior.

Seismology is “the killer application”, says Aster, showing us the Earth has a molten outer-core, “an enormous ocean of white hot molten metal that’s almost as runny as water”.

This core is as large as Mars. But – like a planetary Russian doll – another core was found within this one. An inner-core – a solid metal ball almost the size of the Moon.

Scientists believe the solid inner core is made of an iron-nickel alloy.

To understand what form it might take under the extreme conditions at the centre of the Earth, Professor Kei Hirose set himself a seemingly impossible challenge: recreate the conditions of the core in his lab at the SPring-8 synchrotron near Osaka, Japan. After 10 years of trying, he has finally succeeded.

Crystal forest

Extreme conditions found at the Earth’s core have been recreated in the laboratory

He has created an incredibly powerful vice using the tips of two diamonds. Between them he has pressurised a sample of iron-nickel to three million times atmospheric pressure and heated the sample to about 4,500C.

Under these extraordinary conditions, the crystal structure of iron-nickel alloy changed and the crystals rapidly grew in size. “We may have very big crystals at the centre of the Earth, maybe up to 10km,” says Hirose.

These crystals would all align “like a forest”, says Hirose, pointing at the poles.

The bulk of the Earth’s magnetic field is generated not in the inner-core but in the molten metal of the outer-core. This acts as a massive electromagnetic dynamo powered by the Earth’s rotation and the long-term cooling of the planet.

But although the basic principle is understood, the details of how the molten metal moves are a mystery. As Earth rotates and loses heat from the centre, complex patterns of flow are created within this vast ocean.

“You might think of the core like the atmosphere of the Earth, being a very restless place with storms and fronts and bad weather,” says geophysicist Professor Dan Lathrop from the University of Maryland. He has built himself a massive model of the core to help explain something strange about the field – it is never fixed but constantly fluctuating.

The Earth’s magnetic field has been steadily weakening over the past 180 years. And there is one patch that is weakening faster than any other. It is an area scientists have dubbed the “South Atlantic Anomaly”, which sits over the South Atlantic and the centre of South America.

It is a known hazard for spacecraft because it creates a dip in the field, allowing charged particles into the orbit of satellites and upsetting their electronics and instrumentation.

Magnetic flip

But what some scientists suspect is that it could be much more than an inconvenience to satellite operators – it could be the first indication of a profound change in Earth’s magnetic field.

When scientists mapped the Earth’s magnetic field down to the level of the outer-core, they discovered that under the South Atlantic Anomaly the simple north-south divide we know at the surface had broken down. There are patches where the field has actually flipped and points north instead of south.

Using his weather analogy, Lathrop believes “a particularly violent or unusual patch of weather” in the molten metal of the outer-core is responsible for reversing the field.

If these patches continue to deepen and spread, the entire Earth’s magnetic field could reach a tipping point and flip, he believes.

It is not something that would happen overnight – it could take thousands of years, during which period the field would be pretty confused.

The magnetic poles could wander to the equator for example, and take with them the spectacular Northern Lights. It would not be out of character – the shifting flows of the core have reversed Earth’s field hundreds of times before.

“It’s not a question of if the Earth is going to reverse the magnetic field, but when,” says Lathrop.

Exactly when this might be remains one of the core’s many mysteries. But after centuries of speculation, scientists are finally beginning to understand this great wonder lying 6,000km beneath our feet.

via BBC News – Magnetic mysteries of Earth’s Core.

Earth’s Core: A Moon-Sized Crystal Ball

Wed Jun 29 2011 11:44

Seismologists discover that the inner core rotates

Researchers are now probing what may turn out to be the most curious small body the solar system has yet presented for scrutiny: a globe the size of the moon that appears to be a well ordered crystalline entity. This body is poised little more than 5,000 kilometers away, yet it is completely invisible. Located at the center of the earth, it is known simply as the inner core. Two seismologists have just shown that this strange crystal sphere is turning slowly within the rocky and liquid metal enclosure that keeps it all but hidden from scientific investigation.

Geophysicists realised decades ago that a solid inner core exists, but they knew precious little else about it. They believed the inner core and the liquid shell surrounding it were made largely of iron, yet other features of the heart of the planet remained enigmatic.

But during the 1980s, seismologists examining earthquake waves that pierce the inner core made a startling find. Rather than being "isotropic" (the same in all directions) in its physical properties, the inner core proved to be somewhat like a piece of wood, with a definite grain running through it. Waves traveling along the planet’s north-south axis go 3 to 4 percent faster through the inner core than those that follow paths close to the equatorial plane.

Geophysicists have struggled to explain why this grain (or "seismic anisotropy") should exist. The leading theory is that at the immense pressures of the inner core, iron takes on a hexagonal crystal form that has inherently directional physical properties. Some force apparently keeps the hexagonal iron crystals all in close alignment….

via Earth’s Core: A Moon-Sized Crystal Ball | Before It’s News.