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




CLIMATE SCIENCE
Birth of a mineral
by Staff Writers
Richland WA (SPX) Sep 10, 2014


An aragonite crystal -- with its characteristic "sheaf of wheat" look -- consumed a particle of amorphous calcium carbonate as it formed. Image courtesy Nielsen et al. 2014/Science.

One of the most important molecules on earth, calcium carbonate crystallizes into chalk, shells and minerals the world over. In a study led by the Department of Energy's Pacific Northwest National Laboratory, researchers used a powerful microscope that allows them to see the birth of crystals in real time, giving them a peek at how different calcium carbonate crystals form, they report in Science.

The results might help scientists understand how to lock carbon dioxide out of the atmosphere as well as how to better reconstruct ancient climates.

"Carbonates are most important for what they represent, interactions between biology and Earth," said lead researcher James De Yoreo, a materials scientist at PNNL.

"For a decade, we've been studying the formation pathways of carbonates using high-powered microscopes, but we hadn't had the tools to watch the crystals form in real time. Now we know the pathways are far more complicated than envisioned in the models established in the twentieth century."

Earth's Reserve
Calcium carbonate is the largest reservoir of carbon on the planet. It is found in rocks the world over, shells of both land- and water-dwelling creatures, and pearls, coral, marble and limestone. When carbon resides within calcium carbonate, it is not hanging out in the atmosphere as carbon dioxide, warming the world.

Understanding how calcium carbonate turns into various minerals could help scientists control its formation to keep carbon dioxide from getting into the atmosphere.

Calcium carbonate deposits also contain a record of Earth's history. Researchers reconstructing ancient climates delve into the mineral for a record of temperature and atmospheric composition, environmental conditions and the state of the ocean at the time those minerals formed. A better understanding of its formation pathways will likely provide insights into those events.

To get a handle on mineral formation, researchers at PNNL, the University of California, Berkeley, and Lawrence Berkeley National Laboratory examined the earliest step to becoming a mineral, called nucleation. In nucleation, molecules assemble into a tiny crystal that then grows with great speed.

Nucleation has been difficult to study because it happens suddenly and unpredictably, so the scientists needed a microscope that could watch the process in real time.

Come to Order
In the 20th century, researchers established a theory that crystals formed in an orderly fashion. Once the ordered nucleus formed, more molecules added to the crystal, growing the mineral but not changing its structure.

Recently, however, scientists have wondered if the process might be more complicated, with other things contributing to mineral formation. For example, in previous experiments they've seen forms of calcium carbonate that appear to be dense liquids that could be sources for minerals.

Researchers have also wondered if calcite forms from less stable varieties or directly from calcium and carbonate dissolved in the liquid. Aragonite and vaterite are calcium carbonate minerals with slightly different crystal architectures than calcite and could represent a step in calcite's formation. The fourth form called amorphous calcium carbonate - or ACC, which could be liquid or solid, might also be a reservoir for sprouting minerals.

To find out, the team created a miniature lab under a transmission electron microscope at the Molecular Foundry, a DOE Office of Science User Facility at LBNL. In this miniature lab, they mixed sodium bicarbonate (used to make club soda) and calcium chloride (similar to table salt) in water. At high enough concentrations, crystals grew. Videos of nucleating and growing crystals recorded what happened [URLs to come].

Morphing Minerals
The videos revealed that mineral growth took many pathways. Some crystals formed through a two-step process. For example, droplet-like particles of ACC formed, then crystals of aragonite or vaterite appeared on the surface of the droplets. As the new crystals formed, they consumed the calcium carbonate within the drop on which they nucleated.

Other crystals formed directly from the solution, appearing by themselves far away from any ACC particles. Multiple forms often nucleated in a single experiment -- at least one calcite crystal formed on top of an aragonite crystal while vaterite crystals grew nearby.

What the team didn't see in and among the many options, however, was calcite forming from ACC even though researchers widely expect it to happen. Whether that means it never does, De Yoreo can't say for certain. But after looking at hundreds of nucleation events, he said it is a very unlikely event.

"This is the first time we have directly visualized the formation process," said De Yoreo. "We observed many pathways happening simultaneously. And they happened randomly. We were never able to predict what was going to come up next. In order to control the process, we'd need to introduce some kind of template that can direct which crystal forms and where."

In future work, De Yoreo and colleagues plan to investigate how living organisms control the nucleation process to build their shells and pearls. Biological organisms keep a store of mineral components in their cells and have evolved ways to make nucleation happen when and where needed. The team is curious to know how they use cellular molecules to achieve this control.

Michael H. Nielsen, Shaul Aloni, and James J. De Yoreo. In Situ TEM Imaging of CaCO3 Nucleation Reveals Coexistence of Direct and Indirect Pathways, Science September 5, 2014, doi: 10.1126/science.1254051.

.


Related Links
DOE/Pacific Northwest National Laboratory
Climate Science News - Modeling, Mitigation Adaptation






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

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




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





CLIMATE SCIENCE
Carbon stored in soils more vulnerable to climate change than expected
Exeter, UK (SPX) Sep 05, 2014
The response of soil microbial communities to changes in temperature increases the potential for more carbon dioxide to be released from the world's soils as global temperatures rise, scientists have revealed. The potential for global warming to stimulate decomposition rates in soils, and thus release large quantities of carbon dioxide to the atmosphere, has long been considered to be one ... read more


CLIMATE SCIENCE
China Aims for the Moon, Plans to Bring Back Lunar Soil

Electric Sparks May Alter Evolution of Lunar Soil

China to test recoverable moon orbiter

China to send orbiter to moon and back

CLIMATE SCIENCE
Opportunity Flash-Memory Reformat Planned

Memory Reformat Planned for Opportunity Mars Rover

Scientist uncovers red planet's climate history in unique meteorite

A Salty, Martian Meteorite Offers Clues to Habitability

CLIMATE SCIENCE
Aurora Season Has Started

Russian, US Scientists to Prepare Astronauts for Extreme Situations in Space

Russia's Space Geckos Die Due to Technical Glitch Two Days Before Landing

US to Stop Using Soyuz Spacecraft, Invest in Domestic Private Space Industry

CLIMATE SCIENCE
China launches two satellites via one rocket

China Sends Life to Moon

Same-beam VLBI Tech monitors Chang'E-3 movement on moon

China Sends Remote-Sensing Satellite into Orbit

CLIMATE SCIENCE
Expedition 40 Heads Into Final Week on ISS

3-D Printer Could Turn Space Station into 'Machine Shop'

Russia May Continue ISS Work Beyond 2020

Science and Departure Preps for Station Crew

CLIMATE SCIENCE
Sea Launch Takes Proactive Steps to Address Manifest Gap

SpaceX rocket explodes during test flight

Russian Cosmonauts Carry Out Science-Oriented Spacewalk Outside ISS

Optus 10 delivered to French Guiana for Ariane 5 Sept launch

CLIMATE SCIENCE
Orion Rocks! Pebble-Size Particles May Jump-Start Planet Formation

Rotation of Planets Influences Habitability

Planet-like object may have spent its youth as hot as a star

Young binary star system may form planets with weird and wild orbits

CLIMATE SCIENCE
Artificial membranes on silicon

Ultra-thin Detector Captures Unprecedented Range of Light

Grooving Crystal Surfaces Repel Water

A Metallic Alloy That is Tough and Ductile at Cryogenic Temperatures




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - 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. 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 All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.