Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tiny 3-D images from Stanford and SLAC shed light on origin of Earth's core

17.12.2010
A new method of capturing detailed, three-dimensional images of minute samples of material under extreme pressures is shedding light on the evolution of the Earth's interior. Early results suggest that the early Earth did not have to be entirely molten to separate into the rocky crust and iron-rich core it has today. Researchers at Stanford University and SLAC National Accelerator Laboratory are leading the group pioneering the technique, which could lead to a wide range of new experiments.

To answer the big questions, it often helps to look at the smallest details. That is the approach Stanford mineral physicist Wendy Mao is taking to understanding a major event in Earth's inner history.

Using a new technique to scrutinize how minute amounts of iron and silicate minerals interact at ultra-high pressures and temperatures, she is gaining insight into the biggest transformation Earth has ever undergone – the separation of its rocky mantle from its iron-rich core approximately 4.5 billion years ago.

The technique, called high-pressure nanoscale X-ray computed tomography, is being developed at SLAC National Accelerator Laboratory. With it, Mao is getting unprecedented detail – in three-dimensional images – of changes in the texture and shape of molten iron and solid silicate minerals as they respond to the same intense pressures and temperatures found deep in the Earth.

Mao will present the results of the first few experiments with the technique at the annual meeting of the American Geophysical Union in San Francisco on Thursday, Dec. 16.

Tomography refers to the process that creates a three-dimensional image by combining a series of two-dimensional images, or cross-sections, through an object. A computer program interpolates between the images to flesh out a recreation of the object.

Researchers at SLAC have developed a way to combine a diamond anvil cell, which compresses tiny samples between the tips of two diamonds, with nanoscale X-ray computed tomography to capture images of material at high pressure. The pressures deep in the Earth are so high – millions of times atmospheric pressure – that only diamonds can exert the needed pressure without breaking under the force.

Courtesy of Wendy Mao

Mineral physicist Wendy Mao
At present, the SLAC researchers and their collaborators from HPSync, the High Pressure Synergetic Consortium at the Advanced Photon Source at Argonne National Laboratory, are the only group using this technique.

"It is pretty exciting, being able to measure the interactions of iron and silicate materials at very high pressures and temperatures, which you could not do before," said Mao, an assistant professor of geological and environmental sciences and of photon science. "No one has ever imaged these sorts of changes at these very high pressures."

It is generally agreed that the initially homogenous ball of material that was the very early Earth had to be very hot in order to differentiate into the layered sphere we live on today. Since the crust and the layer underneath it, the mantle, are silicate-rich, rocky layers, while the core is iron-rich, it's clear that silicate and iron went in different directions at some point. But how they separated out and squeezed past each other is not clear. Silicate minerals, which contain silica, make up about 90 percent of the crust of the Earth.

If the planet got hot enough to melt both elements, it would have been easy enough for the difference in density to send iron to the bottom and silicates to the top.

If the temperature was not hot enough to melt silicates, it has been proposed that molten iron might have been able to move along the boundaries between grains of the solid silicate minerals.

"To prove that, though, you need to know whether the molten iron would tend to form small spheres or whether it would form channels," Mao said. "That would depend on the surface energy between the iron and silicate."

Previous experimental work has shown that at low pressure, iron forms isolated spheres, similar to the way water beads up on a waxed surface, Mao said, and spheres could not percolate through solid silicate material.

Mao said the results of her first high-pressure experiments using the tomography apparatus suggest that at high pressure, since the silicate transforms into a different structure, the interaction between the iron and silicate could be different than at low pressure.

"At high pressure, the iron takes a more elongate, platelet-like form," she said. That means the iron would spread out on the surface of the silicate minerals, connecting to form channels instead of remaining in isolated spheres.

"So it looks like you could get some percolation of iron at high pressure," Mao said. "If iron could do that, that would tell you something really significant about the thermal history of the Earth."

But she cautioned that she only has data from the initial experiments.

"We have some interesting results, but it is the kind of measurement that you need to repeat a couple times to make sure," Mao said.

Louis Bergeron | EurekAlert!
Further information:
http://www.stanford.edu

More articles from Materials Sciences:

nachricht Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona

nachricht Metallic nanoparticles will help to determine the percentage of volatile compounds
20.10.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>