Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Argon conclusion: Researchers reassess theories on formation of Earth's atmosphere

21.09.2007
Geochemists at Rensselaer Polytechnic Institute are challenging commonly held ideas about how gases are expelled from the Earth.

Their theory, which is described in the Sept. 20 issue of the journal Nature, could change the way scientists view the formation of Earth’s atmosphere and those of our distant neighbors, Mars and Venus. Their data throw into doubt the timing and mechanism of atmospheric formation on terrestrial plants.

Lead by E. Bruce Watson, Institute Professor of Science at Rensselaer, the team has found strong evidence that argon atoms are tenaciously bound in the minerals of Earth’s mantle and move through these minerals at a much slower rate than previously thought. In fact, they found that even volcanic activity is unlikely to dislodge argon atoms from their resting places within the mantle. This is in direct contrast to widely held theories on how gases moved through early Earth to form our atmosphere and oceans, according to Watson.

Scientists believe that shortly after Earth was formed, it had a glowing surface of molten rock extending down hundreds of miles. As that surface cooled, a rigid crust was produced near the surface and solidified slowly downward to complete the now-solid planet. Some scientists have suggested that Earth lost all of its initial gases, either during the molten stage or as a consequence of a massive collision, and that the catastrophically expelled gases formed our early atmosphere and oceans. Others contend that this early “degassing” was incomplete, and that primordial gases still remain sequestered at great depth to this day. Watson’s new results support this latter theory.

“For the ‘deep-sequestration’ theory to be correct, certain gases would have to avoid escape to the atmosphere in the face of mantle convection and volcanism,” Watson said. “Our data suggest that argon does indeed stay trapped in the mantle even at extremely high temperatures, making it difficult for the Earth to continuously purge itself of argon produced by radioactive decay of potassium.”

Argon and other noble gases are tracer elements for scientists because they are very stable and do not change over time, although certain isotopes accumulate through radioactive decay. Unlike more promiscuous elements such as carbon and oxygen, which are constantly bonding and reacting with other elements, reliable argon and her sister noble gases (helium, neon, krypton, and xenon) remain virtually unchanged through the ages. Its steady personality makes argon an ideal marker for understanding the dynamics of Earth’s interior.

“By measuring the behavior of argon in minerals, we can begin to retrace the formation of Earth’s atmosphere and understand how and if complete degassing has occurred,” Watson explained.

Watson’s team, which includes Rensselaer postdoctoral researcher Jay B. Thomas and research professor Daniele J. Cherniak, developed reams of data in support of their emerging belief that argon resides stably in crystals and migrates slowly. “We realized from our initial results that these ideas might cause a stir,” Watson said. “So we wanted to make sure that we had substantial data supporting our case.”

The team heated magnesium silicate minerals found in Earth’s mantle, which is the region of Earth sandwiched between the upper crust and the central core, in an argon atmosphere. They used high temperature to simulate the intense heat deep within the Earth to see whether and how fast the argon atoms moved into the minerals. Argon was taken up by the minerals in unexpectedly large quantities, but at a slow rate.

“The results show that argon could stay in the mantle even after being exposed to extreme temperatures,” Watson said. “We can no longer assume that a partly melted region of the mantle will be stripped of all argon and, by extension, other noble gases.”

But there is some argon in our atmosphere--slightly less than 1 percent. If it didn’t shoot through the rocky mantle, how did it get into the atmosphere"

“We proposed that argon’s release to the atmosphere is through the weathering of the upper crust and not the melting of the mantle,” Watson said. “The oceanic crust is constantly being weathered by ocean water and the continental crust is rich in potassium, which decays to form argon.”

And what about the primordial argon that was trapped in the Earth billions of years ago" “Some of it is probably still down there,” Watson said.

Because Mars and Venus have mantle materials similar to those found on Earth, the theory could be key for understanding their atmospheres as well.

Watson and his team have already begun to test their theories on other noble gases, and they foresee similar results. “We may need to start reassessing our basic thinking on how the atmosphere and other large-scale systems were formed,” he said.

Gabrielle DeMarco | EurekAlert!
Further information:
http://www.rpi.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth 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 >>>