Nav: Home

Shock compression research shows hexagonal diamond could serve as meteor impact marker

March 14, 2016

LIVERMORE, California - In 1967, a hexagonal form of diamond, later named lonsdaleite, was identified for the first time inside fragments of the Canyon Diablo meteorite, the asteroid that created the Barringer Crater in Arizona.

Since then, occurrences of lonsdaleite and nanometer-sized diamonds have been speculated to serve as a marker for meteorite impacts, having also been connected to the Tunguska explosion in Russia, the Ries crater in Germany, the Younger Dryas event in sites across Northern America and more.

It has been hypothesized that lonsdaleite forms when graphite-bearing meteors strike the Earth. The violent impact generates incredible heat and pressure, transforming the graphite into diamond while retaining the graphite's original hexagonal structure. However, despite numerous theoretical and limited experimental studies, crucial questions have remained unresolved for short-time high-pressure environments relevant to meteor impacts, particularly the structural state immediately after the shock transit, the timescales involved and the influence of crystalline orientation.

In a new paper published today by Nature Communications, a team of researchers, including scientists from Lawrence Livermore National Laboratory (LLNL), provide new insight into the process of the shock-induced transition from graphite to diamond and uniquely resolve the dynamics of the phase change.

The experiments show unprecedented in situ X-ray diffraction measurements of dynamic diamond formation on nanosecond timescales by shock compression of graphite starting at pressures above 0.5 Mbar (1 Mbar = 1 million atmospheres). The team observed the direct formation of lonsdaleite above 1.7 Mbar, for the first time resolving the process that has been proposed to explain the main natural occurrence of this crystal structure being close to meteor impact sites.

"Due to difficulties in creating lonsdaleite under static conditions, the overall existence of this crystal structure in nature has been questioned recently," said lead author Dominik Kraus. Kraus conducted this research while working as a University of California, Berkeley, Physics Department postdoc sited within LLNL's NIF & Photon Science directorate. He now serves as the Helmholtz Young Investigator group leader at Helmholtz-Zentrum Dresden-Rossendorf in Germany.

"However, static experiments cannot mimic fast dynamics such as those in violent meteor impact events," he said. "Here we show that we can indeed create a lonsdaleite structure during dynamic high-pressure events. This is interesting for modeling dynamic phase transitions in general, but also shows that the lonsdaleite found in nature could indeed serve as a marker for violent meteor impacts."

The experiments were conducted at the Matter at Extreme Conditions (MEC) experimental area at the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory at Stanford. Graphite samples were shock-compressed to pressures of up to 2 million atmospheres (2 Mbar) to trigger the structural transitions from graphite to diamond and lonsdaleite. The phase changes in the high-pressure samples were probed with ultrafast (femtosecond) X-ray pulses created by LCLS.

According to Kraus, this was the very first in situ structure measurement of the shock-induced graphite to diamond transition. Before these experiments, all conclusions regarding this structural transition where based from the material that was recovered after applying the shock drive or dynamic measurements of macroscopic quantities, such as density and pressure.

"You won't get rich from our experiments, but the shock-induced transition from graphite to diamond already has important industry applications," he said. "For example, nanometer-sized diamonds for fine polishing of materials are created by detonation of carbon-bearing explosives. These explosions typically generate pressures up to ~0.5 Mbar, just above the threshold of diamond formation. Here we show that above 2 Mbar, the lonsdaleite structure can be generated in a very pure form. Since pure lonsdaleite is supposedly even harder than diamond, this is highly interesting and other groups now try to recover these samples after an experiment."
Kraus was joined by LLNL co-authors Tilo Doeppner and Benjamin Bachmann, and scientists from the University of California, Berkeley, SLAC, the University of Warwick, the Max Planck Institute, Technical University Darmstadt, Helmholtz-Zentrum Dresden-Rossendorf, the University of Oxford and GSI.

The U.S. Department of Energy's Office of Science and the German Federal Ministry for Education and Research funded the work.

Founded in 1952, Lawrence Livermore National Laboratory provides solutions to our nation's most important national security challenges through innovative science, engineering and technology. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.

DOE/Lawrence Livermore National Laboratory

Related Diamond Articles:

Engaging diamond for next-era transistors
Most transistors are silicon-based and silicon technology has driven the computer revolution.
Looking at light to explore superconductivity in boron-diamond films
More than a decade ago, researchers discovered that when they added boron to the carbon structure of diamond, the combination was superconductive.
Unpolarized single-photon generation with true randomness from diamond
The Tohoku University research group of Professor Keiichi Edamatsu and Postdoctoral fellow Naofumi Abe has demonstrated dynamically and statically unpolarized single-photon generation using diamond.
The world's largest diamond foil
Material researchers of Friedrich-Alexander Universität Erlangen Nürnberg have come a step closer to their goal of providing large diamond foils for practical applications.
How fullerite becomes harder than diamond
The scientists suggested that under pressure, part of the fullerite turned into diamond, while the other part remained as fullerite, but in a compressed state within the diamond.
Dr. Sakamoto explains signaling pathways in the pathogenesis of diamond blackfan anemia
The results from this research have shed light on a previously undiscovered link between the well-studied p53 pathway and the lesser known pathways associated with ribosome biogenesis and nucleotide metabolism in DBA.
New diamond harder than ring bling
The Australian National University has led an international project to make a diamond that's predicted to be harder than a jeweler's diamond and useful for cutting through ultra-solid materials on mining sites.
'Diamond-age' of power generation as nuclear batteries developed
New technology has been developed that uses nuclear waste to generate electricity in a nuclear-powered battery.
Diamond nanothread: Versatile new material could prove priceless for manufacturing
QUT's Dr Haifei Zhan is leading a global effort to work out how many ways humanity can use a newly-invented material with enormous potential -- diamond nanothread.
Defects in diamond: A unique platform for optical data storage in 3-D
There are limitations on storing large volumes of data. Home-computer hard disk drives consume a lot of power and are limited to a few terabytes per drive.

Related Diamond Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#514 Arctic Energy (Rebroadcast)
This week we're looking at how alternative energy works in the arctic. We speak to Louie Azzolini and Linda Todd from the Arctic Energy Alliance, a non-profit helping communities reduce their energy usage and transition to more affordable and sustainable forms of energy. And the lessons they're learning along the way can help those of us further south.