Noble gases hitch a ride on hydrous minerals

June 16, 2013 ? The six noble gases do not normally dissolve into minerals, leaving earth scientists to wonder how they are subducted back into the Earth. Researchers at Brown have discovered that the lattice structure of minerals such as amphibole provides a way. Better yet, the multiple isotopes of noble gases could help scientists track volatiles like water and carbon.

The noble gases get their collective moniker from their tendency toward snobbishness. The six elements in the family, which includes helium and neon, don't normally bond with other elements and they don't dissolve into minerals the way other gases do. But now, geochemists from Brown University have found a mineral structure with which the nobles deign to fraternize.

Researchers led by Colin Jackson, a graduate student in geological sciences, have found noble gases to be highly soluble in amphibole, a mineral commonly found in oceanic crust. "We found remarkably high solubility," said Stephen Parman, assistant professor of geological sciences at Brown and Jackson's Ph.D. adviser. "It was three or four orders of magnitude higher than in any other mineral than had been measured."

The findings, which are published in Nature Geoscience, are a step toward answering puzzling questions about how noble gases are cycled between the atmosphere and the depths of the Earth.

Completing the cycle

Gases in the air we breathe are on a geological conveyor belt of sorts, cycled from the Earth's mantle to the atmosphere and back again. Carbon dioxide, water vapor and other gases are released into the atmosphere and oceans from molten magma during volcanic eruptions, and then returned to depths through subduction, when one tectonic plate slides underneath another. The subducting crust is injected deep into the mantle, taking water and any other volatiles it may carry along for the ride.

Noble gases are also released during volcanic activity, but the amount of those gases returned to the mantle through subduction was long thought to be minimal. After all, if noble gases don't dissolve in minerals, they would lack a vehicle to make the trip. Recent research, however, has suggested that some noble gases are indeed recycled, leaving scientists at a loss to find a mechanism for it. By showing definitively that noble gases are soluble in amphibole, Jackson and his colleagues have shown how noble gases could be carried in subducting slabs.

The key to amphibole's ability to dissolve noble gases, the researchers say, is its lattice structure. Amphibole and other silicate minerals are made up of tetrahedral and octahedral structures linked together in a way that creates a series of rings. It's those rings, called A-sites, that provide a home for otherwise finicky noble gases, the research suggests.

Jackson performed a series of experiments to see if the number of empty rings in different types of amphibole were correlated to its ability to dissolve noble gases. He placed cut amphibole gems into a tube with helium or neon under high pressure and temperature, and then used a mass spectrometer to see how much of the gas had dissolved in each gem over the duration of each experiment. The experiments showed that noble gas solubility was highest in types of amphibole with the most unoccupied ring structures.

"This was the meat of the paper," Parman said. "It's telling us a specific site where we think the noble gases are. It might be the first time anyone has made a positive identification of where noble gases are going into a mineral."

Importantly, the researchers said, amphibole isn't the only crustal mineral with these ring structures. Ring structures are actually quite common in crustal minerals, and could provide a wide variety of potential vehicles that could take noble gases back to the depths via subduction.

A high-fidelity fingerprint

Understanding how noble gases are cycled between the Earth's surface and interior could shed new light on how other volatiles are recycled, the researchers said.

Scientists are particularly interested in tracking the cycling of water and carbon. Water is obviously vital for life, and carbon cycling has an important impact on the climate. Scientists try to track the cycle by looking at isotope ratios, which can provide a fingerprint that helps to identify where elements originated. Butarbon and the hydrogen in water have only a few isotopes that scientists can use for tracking, and in the case of hydrogen, the isotope ratios are easily thrown off by all kinds of natural processes.

The noble gases, on the other hand, have lots of isotopes, giving scientists ways to track them with great specificity. So if noble gases are cycled in the same minerals that cycle other volatiles like water and carbon, they could be used as a marker to track those other volatiles. "It's a very high-fidelity fingerprint because you have so many isotopes to play with," Jackson said.

There's more work to be done before noble gases could be used as such a fingerprint, but this work does provide a first step: showing which kinds of minerals could be responsible for noble gas recycling.

Other authors on the paper were Simon Kelley of The Open University in the United Kingdom and Reid Cooper, professor of geological sciences at Brown. The work was funded by the National Science Foundation's Division of Earth Sciences (1019229).

Source: http://feeds.sciencedaily.com/~r/sciencedaily/most_popular/~3/1xSZsu3gDTI/130616155204.htm

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Obama taps finance director as envoy to Denmark

WASHINGTON (AP) ? Handing plum European posts to key campaign boosters, President Barack Obama on Friday nominated his former finance director to be U.S. ambassador to Denmark and tapped two major fundraisers for postings in Spain and Germany.

Fundraising guru Rufus Gifford, who raised upward of $700 million as the head of Obama's 2012 finance operation and held a similar job previously at the Democratic National Committee, is Obama's pick for Denmark, the White House said. Obama selected James Costos, a vice president of HBO, as his envoy to Spain.

If confirmed by the Senate, Gifford and Costos would bolster the limited ranks of ambassadors in U.S. history who have been openly gay. When Obama took office in 2009, only two previous ambassadors had been openly gay. Friday's nominations mark the fifth and sixth, gay rights groups said.

The Gay & Lesbian Victory Fund, which works to elect openly gay candidates, hailed the nominations and said they would clear the way for more gay Americans to achieve prominent positions in public service.

Obama also said he had selected John Emerson, an investment manager and former White House official, as his envoy to Germany. Both Costos and Emerson were listed in public disclosures as bundlers, meaning they raised more than $500,000 from others to benefit Obama's campaign. Federal Election Commission records show Costos donated more than $67,000 to efforts to re-elect Obama in 2012.

Ken Hackett, who stepped down last year as the president and CEO of Catholic Relief Services, is Obama's pick to be the U.S. emissary to the Vatican. Hackett worked extensively in Africa coordinating Catholic charitable programs on the continent.

Patricia Marie Haslach, a veteran diplomat who has worked in Iraq, Pakistan and Laos, is Obama's pick to be ambassador to Ethiopia. He nominated Liliana Ayalde, another State Department official with experience throughout Latin and Central America, for the top post in Brazil. Both Haslach and Ayalde have held the rank of ambassador before.

___

Reach Josh Lederman on Twitter at http://twitter.com/joshledermanAP

Source: http://news.yahoo.com/obama-taps-finance-director-envoy-denmark-205518401.html

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Reaction cool to US arms plan for Syrian rebels

WASHINGTON (AP) ? The Obama administration hopes its decision to give lethal aid to Syrian rebels will prompt other nations to beef up assistance, now that the U.S. has cited evidence that the Syrian government used chemical weapons against its people. But the international reaction Friday ranged from flat-out disbelief of the U.S. intelligence assessments to calls for negotiation before more weapons pour into the vicious civil war.

The administration now says it has "high confidence" that President Bashar Assad's forces have killed up to 150 people with sarin gas. Although that's a tiny percentage of the approximately 93,000 killed in the civil war so far, the use of a chemical weapon crosses President Barack Obama's "red line" for escalating U.S. involvement in the conflict and prompted the decision to send arms and ammunition, not just humanitarian aid and defensive non-lethal help like armored vests and night goggles.

The administration's plan heading into the G8 meeting of industrialized nations beginning Monday is to use the chemical weapons announcement and Obama's decision on arms to persuade Russia to increase pressure on Assad to send a credible negotiating team to Geneva for talks with the opposition.

In addition, Obama is expected to use the G8 meeting and discussions on the sidelines to further coordinate with the British, French and potentially others an increase of assistance ? lethal, non-lethal and humanitarian ? to the rebels, the political opposition and refugees.

In a letter to U.N. Secretary-General Ban Ki-moon, U.N. Ambassador Susan Rice said the United States has determined that sarin was used in a March 19 attack on the Aleppo suburb of Khan al-Assal and in an April 13 attack on the neighborhood of Shaykh Maqsud. She said unspecified chemicals, possibly including chemical warfare agents, were used May 14 in an attack on Qasr Abu Samrah and in a May 23 attack on Adra.

U.S. officials have not disclosed any details about the weapons they intend to send to Syria or when and how they will be delivered. According to officials, the U.S. is most likely to provide the rebel fighters with small arms, ammunition, assault rifles and a variety of anti-tank weaponry such as shoulder-fired rocket-propelled grenades and other missiles.

As of Friday, however, no final decisions had been made on the details or when it would reach the rebels, according to the officials, who insisted on anonymity because they were not authorized to discuss internal administration discussions with reporters.

Obama has consistently said he will not put American troops in Syria, making it less likely the U.S. will provide sophisticated arms or anti-aircraft weapons that would require large-scale training. Administration officials are also worried about high-powered weapons ending up in the hands of terrorist groups. Hezbollah fighters are among those backing Assad's armed forces, and al-Qaida-linked extremists back the rebellion.

The lethal aid will largely be coordinated by the CIA, but that effort will also be buttressed by an increased U.S. military presence in Jordan.

U.S. officials say Defense Secretary Chuck Hagel is about to approve orders that would leave roughly a dozen F-16 fighter jets and a Patriot missile battery in Jordan after ongoing military exercises there end later next week. That would result in several hundred more U.S. troops staying in Jordan to support the fighters and missiles, in addition to the approximately 250 that have been there for some time.

The added military troops and equipment are designed to increase stability in the region and are not part of the effort to train Syrian rebels or take part in any offensive operations in Syria, the U.S. officials said, speaking on condition of anonymity because they were not authorized to talk about the details.

The biggest hurdle for the U.S. strategy remains Russia, a major weapons supplier to Assad.

President Vladimir Putin's foreign affairs adviser, Yuri Ushakov, said Friday that Moscow doesn't believe the U.S. finding on chemical weapons.

"I wouldn't like to draw parallels with the famous dossier of Secretary of State Colin Powell, but the facts, the information presented by the U.S. didn't look convincing," he said. The comment indeed drew a parallel with Powell's speech to the U.N. asserting pre-war Iraq had weapons of mass destruction, a claim that proved false.

Ushakov also suggested that sending weapons to the opposition would diminish Moscow's interest in negotiations in Geneva.

"If the Americans make and fulfill a decision to provide a greater assistance to the rebels, to the opposition, it's not going to make the preparations for an international conference on Syria any easier," he said.

Obama's deputy national security adviser, Ben Rhodes, acknowledged the differences that remain between U.S. and Russia on the Syrian crisis. Despite their disagreement over chemical weapon use, the U.S. will continue to talk to the Russians about ways to achieve a political settlement in Syria, considered the best option by all .

"We have no illusions that that's going to be easy," Rhodes said, adding that Obama and Putin would meet next week.

Getting Western allies to increase support for the rebels won't necessarily be easy, either.

British Prime Minister David Cameron has said he there is credible evidence of "multiple attacks" using chemical weapons by Assad's fighters, but indicated that al-Qaida-linked elements in the opposition movement had also attempted to acquire chemical weapons for probable use in Syria. Still, he restated the government's position that no decision had been taken to arm moderate rebels opposed to Assad. The Obama administration says it has no evidence the opposition has used chemical weapons.

French President Francois Hollande told reporters Friday that the use of chemical weapons by Assad "confirms that we must exercise pressure on the regime." But Foreign Ministry spokesman Philippe Lalliot would not say whether the U.S. claim of chemical weapons adds momentum to arming rebels.

U.N. Secretary-General Ban Ki-moon, however, voiced opposition to the U.S. decision to send arms to the Syrian rebels. He said no one can be certain chemical weapons were used without an on-the-ground investigation. Increasing the flow of arms to either side "would not be helpful," he said

Washington's decision comes after several military setbacks for the rebels and as Lebanon's Hezbollah militia becomes increasingly involved, fighting alongside Assad's forces. Hezbollah's role was key in the capture of the strategic rebel-held town of Qusair earlier this month.

The U.S. has so far provided $250 million in non-lethal military and political aid to the Syrian opposition. The Obama administration has already told Congress that $127 million of this aid is in the pipeline. State Department spokeswoman Jen Psaki said Friday the administration now has notified Congress that the remaining $123 million in assistance, including body armor and other equipment such as night-vision goggles, is beginning to move to the Syrian rebels.

The plan to arm the rebels comes after a tricky assessment of which groups in the opposition the U.S. and allies can work with and which should be avoided.

"I think we know who the good guys are ... who we can trust and who we cannot," said Rep. C.A. Dutch Ruppersberger of Maryland, the top Democrat on the House Intelligence Committee. He received briefings from U.S. diplomats and intelligence officials in Jordan last month and visited a refugee camp at the Syrian border.

He said the U.S. aid will include weapons training and basic military tactics, and share intelligence to help guide the rebels to the right targets.

"Intelligence is a key component to helping the opposition warfighters to make sure they make the right decisions to turn the tide of this fight," said Ruppersberger.

The CIA has led U.S. outreach to the rebels from outside Syria, meeting rebels at refugee camps and towns along the Turkish and Jordanian borders. CIA paramilitary officers, as well as special operations trainers, have trained select groups of rebels in Jordan on the use of encrypted communications equipment ? the nonlethal aid provided by the Obama administration ? and they have helped the rebels learn how to fire anti-aircraft weapons and small arms provided by Gulf states.

"We've been looking at this for a long time now," said John McLaughlin, former acting director of the CIA. "You can do a pretty good diagram of who the rebel forces are, what the number of foreign fighters are. We've come to the conclusion that there is an acceptable level of risk, understanding we will lose control of some of the weapons."

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Associated Press writers Matthew Lee and Kimberly Dozier in Washington, Edith M. Lederer at the United Nations, Elaine Ganley in Paris and Cassadra Vinograd in London contributed to this report.

Source: http://news.yahoo.com/reaction-cool-us-arms-plan-syrian-rebels-222514541.html

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Climate talk shifts from curbing CO2 to adapting (The Arizona Republic)

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