Subscribe free to our newsletters via your
. 24/7 Space News .




Subscribe free to our newsletters via your




















IRON AND ICE
High-pressure experiments solve meteorite mystery
by Staff Writers
Hamburg, Germany (SPX) Jun 08, 2017


Cristobalite crystals from Harvard Mineralogical Museum, found at Ellora caves in India. Credit: RRUFF Project / University of Arizona

With high-pressure experiments at DESY's X-ray light source PETRA III and other facilities, a research team around Leonid Dubrovinsky from the University of Bayreuth has solved a long standing riddle in the analysis of meteorites from Moon and Mars. The study, published in the journal Nature Communications, can explain why different versions of silica can coexist in meteorites, although they normally require vastly different conditions to form. The results also mean that previous assessments of conditions at which meteorites have been formed have to be carefully re-considered.

The scientists investigated a silicon dioxide (SiO2) mineral that is called cristobalite. "This mineral is of particular interest when studying planetary samples, such as meteorites, because this is the predominant silica mineral in extra-terrestrial materials," explains first author Ana Cernok from Bayerisches Geoinstitut (BGI) at University Bayreuth, who is now based at the Open University in the UK. "Cristobalite has the same chemical composition as quartz, but the structure is significantly different," adds co-author Razvan Caracas from CNRS, ENS de Lyon.

Different from ubiquitous quartz, cristobalite is relatively rare on Earth's surface, as it only forms at very high temperatures under special conditions. But it is quite common in meteorites from Moon and Mars. Ejected by asteroid impacts from the surface of Moon or Mars, these rocks finally fell to Earth.

Surprisingly, researchers have also found the silica mineral seifertite together with cristobalite in Martian and lunar meteorites. Seifertite was first synthesised by Dubrovinsky and colleagues 20 years ago and needs extremely high pressures to form. "Finding cristobalite and seifertite in the same grain of meteorite material is enigmatic, as they form under vastly different pressures and temperatures," underlines Dubrovinsky.

"Triggered by this curious observation, the behaviour of cristobalite at high-pressures has been examined by numerous experimental and theoretical studies for more than two decades, but the puzzle could not be solved."

Using the intense X-rays from PETRA III at DESY and the European Synchrotron Radiation Facility ESRF in Grenoble (France), the scientists could now get unprecedented views at the structure of cristobalite under high pressures of up to 83 giga-pascals (GPa), which corresponds to roughly 820,000 times the atmospheric pressure.

"The experiments showed that when cristobalite is compressed uniformly or almost uniformly - or as we say, under hydrostatic or quasi-hydrostatic conditions - it assumes a high-pressure phase labelled cristobalite X-I," explains DESY co-author Elena Bykova who works at the Extreme Conditions Beamline P02.2 at PETRA III, where the experiments took place. "This high-pressure phase reverts back to normal cristobalite when the pressure is released."

But if cristobalite is compressed unevenly under what scientists call non-hydrostatic conditions, it unexpectedly converts into a seifertite-like structure, as the experiments have now shown. This structure forms under significantly less pressure than necessary to form seifertite from ordinary silica. "The ab initio calculations confirm the dynamical stability of the new phase up to high pressures," says Caracas. Moreover it also remains stable when the pressure is released.

"This came as a surprise," says Cernok. "Our study clarifies how squeezed cristobalite can transform into seifertite at much lower pressure than expected. Therefore, meteorites that contain seifertite associated with cristobalite have not necessarily experienced massive impacts." During an impact, the propagation of the shock wave through the rock can create very complex stress patterns even with intersecting areas of hydrostatically and non-hydrostatically compressed materials, so that different versions of silica can form in the same meteorite.

"These results have immediate implications for studying impact processes in the solar system," underlines Dubrovinsky. "They provide clear evidence that neither cristobalite nor seifertite should be considered as reliable tracers of the peak shock conditions experienced by meteorites."

But the observations also show more generally that the same material can react very differently to hydrostatic and non-hydrostatic compression, as Dubrovinsky explains. "For materials sciences our results suggest an additional mechanism for the manipulation of the properties of materials: Apart from pressure and temperature, different forms of stress may lead to completely different behaviour of solid matter."

Compressional pathways of a-cristobalite, structure of cristobalite X-I, and towards the understanding of seifertite formation; Ana Cernok, Katharina Marquardt, Razvan Caracas, Elena Bykova, Gerlinde Habler, Hanns-Peter Liermann, Michael Hanfland, Mohamed Mezouar, Ema Bobocioiu, and Leonid Dubrovinsky; Nature Communications", 2017; DOI: 10.1038/ncomms15647

IRON AND ICE
Scientists solve meteorite mystery with high-pressure X-ray experiments
Washington (UPI) Jun 7, 2017
Scientists have long struggled to understand how different types of silica, which require distinction formation conditions, are commonly found in the same meteorite. Thanks to PETRA III, the X-ray light accelerator at DESY, the German research facilities, scientists finally have some answers. Researchers used high-pressure experiments to better understand the conditions under whi ... read more

Related Links
Deutsches Elektronen-Synchrotron DESY
Asteroid and Comet Mission News, Science and Technology

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

IRON AND ICE
Pence hails new NASA astronauts as 'best of us'

John Glenn Cygnus departs ISS begins secondary mission

Additional Astronaut on the Space Station Means Dozens of New Team Members on the Ground

Roscosmos Says Cooperation With NASA Unaffected by 'Political Outbursts'

IRON AND ICE
SpaceX's first recycled Dragon arrives at space station

Russian rocket returns to service with launch of US satellite

India shows off space prowess with launch of mega-rocket

NASA awards Universal Stage Adapter contract for SLS

IRON AND ICE
Study estimates amount of water needed to carve Martian valleys

Opportunity Surveying the spillway into Perseverance Valley

Collateral damage from cosmic rays increases cancer risks for Mars astronauts

Curiosity Peels Back Layers on Ancient Martian Lake

IRON AND ICE
China discloses Chang'e 5 lunar probe landing site

China's 1st astronaut details projects for orbital station, manned lunar visit

Spotlight: First China-designed experiment flies to space station

News Analysis: U.S.-China space freeze may thaw with new commercial pathway

IRON AND ICE
Thomas Pesquet returns to Earth

Propose a course idea for the CU space minor

Leading Global Air And Space Law Group Joins Reed Smith

New Horizons for Alexander Gerst

IRON AND ICE
Saudi deal for counterfire radars approved by U.S. State Department

Study proves viability of quantum satellite communications

Indian Space Agency to Work on Electric Propulsion for Large Satellites

Bamboo inspires optimal design for lightness and toughness

IRON AND ICE
Discovery reveals planet almost as hot as the Sun

A planet hotter than most stars

Hubble's tale of 2 exoplanets - Nature vs nurture

Astronomers discover alien world hotter than most stars

IRON AND ICE
A whole new Jupiter with first science results from Juno

First results from Juno show cyclones and massive magnetism

Jupiters complex transient auroras

NASA's Juno probe forces 'rethink' on Jupiter




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement