Moqui Marbles and Martian Blueberries

The photo above shows Moqui Marbles in their native habitat of southern Utah. These curious rocks are actually concretions having iron (hematite) rinds.

Very similar rocks, called blueberries, have been observed repeatedly on Mars by the rovers. Click here to see an image taken by the Opportunity rover of the blueberries. Some scientific papers implicate the possibility of life on Mars playing a role in their formation while others do not.

Discussions about the pros and cons of their formation have been quite lively at times. However, the consensus seems to be that both the marbles and the blueberries were created beneath the surface as naturally occurring substances, most likely minerals, precipitated from flowing groundwater. Pictured with the marbles is a Devil’s-Claw cactus (Sclerocactus parviflorus). — Bret Webster

Deep Canadian mine yields ancient water

Scientists working 2.4 kilometres below Earth’s surface in a Canadian mine have tapped a source of water that has remained isolated for at least a billion years. The researchers say they do not yet know whether anything has been living in it all this time, but the water contains high levels of methane and hydrogen — the right stuff to support life.

Micrometre-scale pockets in minerals billions of years old can hold water that was trapped during the minerals’ formation. But no source of free-flowing water passing through interconnected cracks or pores in Earth’s crust has previously been shown to have stayed isolated for more than tens of millions of years.

“We were expecting these fluids to be possibly tens, perhaps even hundreds of millions of years of age,” says Chris Ballentine, a geochemist at the University of Manchester, UK. He and his team carefully captured water flowing through fractures in the 2.7-billion-year-old sulphide deposits in a copper and zinc mine near Timmins, Ontario, ensuring that the water did not come into contact with mine air.

To date the water, the team used three lines of evidence, all based on the relative abundances of various isotopes of noble gases present in the water. The authors determined that the fluid could not have contacted Earth’s atmosphere — and so been at the planet’s surface — for at least 1 billion years, and possibly for as long as 2.64 billion years, not long after the rocks it flows through formed. The study appears today in Nature.

‘Extremely strange’

“The isotopic compositions that they see in these samples are extremely strange, and the preferred explanation in the article seems to me the most likely one,” says Pete Burnard, a geochemist at the Centre of Petrographic and Geochemical Research in Vandœuvre-les-Nancy, France. “For the moment, I think we have to conclude that there are 1.5-billion-year-old fluids trapped in the crust.”

The findings are “doubly interesting”, Ballentine says, because the fluid carries the ingredients necessary to support life. The isolated water supply, he says, provides “secluded biomes, ecosystems, in which life, you can speculate, might have even originated”. His colleagues are now working to establish whether the water does harbour life.

The findings may also have implications for life on Mars, Ballentine says, though he acknowledges that the idea is speculative. The surface of Mars once held water and its rocks are chemically no different from those on Earth, he says. “There is no reason to think the same interconnected fluids systems do not exist there.”

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Earth’s Rotating Inner Core Shifts Its Speed

Earth’s solid-metal inner core is a key component of the planet, helping to give rise to the magnetic field that protects us from harmful space radiation, but its remoteness from the planet’s surface means that there is much we don’t know about what goes on down there. But some secrets of the inner core are being revealed by acoustic waves passing through the planet’s heart and iron squeezed to enormous pressures in the lab.

Two new studies, both detailed online May 12 in the journal Nature Geoscience, reveal that Earth’s inner core may actually be softer than previously thought, and that the speed at which it spins can fluctuate over time.

Under the liquid-metal outer layer of the Earth’s core is a solid ball of superhot iron and nickel alloy about 760 miles (1,220 kilometers) in diameter. Scientists recently discovered the inner core is, at 10,800 degrees Fahrenheit (6,000 degrees Celsius), as hot as the surface of the sun.

Churning in the liquid outer core results in the dynamo that generates Earth’s magnetic field. Geoscientists think interactions between the inner and outer cores may help explain the nature of the planet’s dynamo, the details of which remain largely unknown.

“The Earth’s inner core is the most remote part of our planet, and so there is a lot we don’t know about it because we can’t go down and collect samples,” said Arianna Gleason, a geoscientist at Stanford University in California. 

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The Center of the Earth Is as Hot as the Sun

Crushed by the weight of the thousands of kilometers of liquid iron and sulfur, superheated metal and minerals and cool crustal rock above, the Earth’s core is under immense pressure. Heated from within by friction and by the decay of radioactive material and still shedding heat from the initial formation of the planet 4.5 billion years ago, the planet’s core is blisteringly hot. In new research, scientists studying what the conditions at the core should be like found that the center of the Earth is way hotter than we thought—around 1,800 degrees hotter, putting the temperature at a staggering 10,800 degrees Fahrenheit.

This superheated core, says the BBC, is about as hot as the surface of the Sun.

Scientists know the Earth’s core, a multi-layered structure with a solid iron core spinning in a sea of liquid iron and sulfur, is hot. But, cut off from direct study by all the stuff in between the core and the surface, getting an accurate idea of the core’s properties is a daunting feat.

Led by Simone Anzellini, the French research team did their best bet to reproduce the core’s properties in the lab: they took a bunch of iron and crushed it between two pieces of diamond. Then they shot it with a laser. The apparatus produces massive pressures and superheated temperatures. This let them study how the iron behaved under such intense conditions and gave them a window into the conditions found at the planet’s center.

Knowing how hot the Earth’s core is can add to our understanding all sorts of wonders, from the existence of the planetary magnetic field, to the propagation of seismic waves after an earthquake, to the birth of the Earth itself.

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Ancient crust rises from the deep - Remnants of surface rocks take long tour of planet’s interior.

Earth recycles — but it takes its time. Chemical remnants of the rigid surface plates that plunge deep into the planet’s interior at subduction zones can eventually resurface on distant volcanic islands. But the process may take more than two billion years, a study published in this issue suggests.

By analysing volcanic rock that erupted millions of years ago on an island in the South Pacific, the researchers found clues about when components of the rock first left Earth’s surface and began their long journey through its interior. The authors’ findings are “a smoking gun” for deep, slow tectonic recycling, says Steven Shirey, a geochemist at the Carnegie Institution for Science in Washington DC. “It’s hard to conclude that they’re not right.”

Studies of volcanic rock have revealed that the chemical and isotopic composition of Earth’s mantle — the layer of molten rock beneath the crust — varies considerably from place to place, says Rita Cabral, a geochemist at Boston University in Massachusetts and a co-author of the paper. Some have proposed that those variations arose because chunks of crust that once resided at Earth’s surface have tainted parts of the mantle. But researchers have had to rely on computer models to estimate how fast the recycling takes place — and firm evidence that material is recycled through the planet’s deep interior has been lacking.

Cabral and her colleagues now have compelling evidence that such tectonic recycling really happens, and of how long it takes. The team analysed rock samples from Mangaia, the southernmost of Polynesia’s Cook Islands. The rocks, formed by volcanic activity about 20 million years ago, have been worn by weathering. But sulphide minerals locked away inside weather-resistant crystals of olivine, which formed at a depth of a few kilometres before spewing from the volcano, still retain their pre-eruption composition, says Cabral.

That composition is telling. For one thing, Cabral notes, the proportion of the isotope sulphur-33 is substantially lower than that typically found in Earth’s crust. Although biological processes can generate such an anomaly, they would simultaneously generate abnormally high concentrations of sulphur-34 — which are not present in the Mangaia samples.

The most likely source of the sulphur-33- depleted rocks, the team says, is mantle material that includes remnants of crust that sank or were pushed below Earth’s surface at least 2.45 billion years ago, before photosynthetic organisms filled the atmosphere with oxygen. When oxygen was low, sunlight-driven reactions would naturally have created sulphides containing lower-than-normal proportions of sulphur-33; later, the ozone layer resulting from the surge of oxygen would have stifled those reactions.

At some point, Cabral contends, material from the core–mantle boundary upwelled in a ‘hotspot’ — a large-scale version of the buoyancy-driven burbling seen in the lava lamps that were popular during the 1970s. The upwelling swept the sulphur-33-depleted material back to the surface.

In addition to providing insight into the pace of tectonic recycling, the findings reveal how little violent mixing occurs deep within Earth, says Cabral. The purported piece of ancient crust containing the sulphur-33- depleted minerals “had to have stayed relatively intact in the mantle for all that time”, she notes, implying that the deep mantle may be a graveyard of ancient tectonic slabs.

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Tectonic Summary of the 7.8 magnitude earthquake in Iran

The April 16, 2013 M 7.8 earthquake east of Khash, Iran, occurred as a result of normal faulting at an intermediate depth in the Arabian plate lithosphere, approximately 80 km beneath the Earth’s surface. Regional tectonics are dominated by the collisions of the Arabian and India plates with Eurasia; at the longitude of this event, the Arabian plate is converging towards the north-northeast at a rate of approximately 37 mm/yr with respect to the Eurasian plate. Arabian plate lithosphere is subducted beneath the Eurasian plate at the Makran coast of Pakistan and Iran, and becomes progressively deeper to the north.

The subducted Arabian plate is known to be seismically active to depths of about 160 km. The frequency of moderate and large earthquakes within the subducted Arabian plate is not high compared with similar events in some other subducted plates worldwide, but several earthquakes have occurred within this slab in the region of today’s event over the past 40 years, including a magnitude 6.7 shock 50 km to the south in 1983. In January of 2011, a M 7.2 earthquake occurred approximately 200 km to the east, in a similar tectonic environment to the April 16 earthquake.

More details @usgs.com

For Peat’s Sake - Peat is not a renewable resource. What does that mean for my favorite Scotch whiskies?

The peat that the Scotch industry burns by the ton to make peated whiskies isn’t renewable, but it’s not quite a fossil fuel either. A sort of proto-coal, peat is a mush of partially decomposed plant matter that lies on the surface of the Earth and accumulates imperceptibly, by about a millimeter a year. It only forms in places where a handful of climatic conditions are in balance. Soil chemistry, density of flora, precipitation, temperature, humidity, and average wind speed must be just so, yielding a habitat with more rainfall than evaporation can subsequently carry away. When all these variables line up, plants never fully decompose; an initial, brief round of decay produces a bath of weak acids that prevents any further decomposition. Over centuries, mummified plants pile up and get compressed into a carbon-rich gunk that resembles crumbly, wet Oreo cookies. Give it a few more million years, and this peat turns into coal.

“There’s some peat that’s 20,000 years old,” says Sandy Neuzil, a peat specialist with the United States Geological Survey. “But most of it’s between 4,000 and 8,000 years.”

In peat-rich regions, which are located mostly in Northern Europe, Canada, and Russia, people have long burned the gunk for heating and cooking. For most of human history, consumption was at the household level and without serious consequences. However, in at least one place, Ireland’s Blasket Islands, the peat resource was totally exhausted. (For this reason, the islands have been uninhabited since 1953.) In the past 150 years, peat consumption ticked up as it became a primary fuel in some power plants, though most of these plants are closing or reducing the amount of peat they burn.

Every year, about 25 million tons of peat are harvested and burned, by individuals, power utilities, and companies of various kinds (including, but not limited to, distilleries). Another 14 million tons are used by farmers, landscapers, and gardeners to amend deficient soil. Peat keeps golf courses looking sharp. As massive as these numbers are, they amount to about 0.1 percent of the global peat resource. An additional 10 percent of the global resource has been lost to real-estate development and agriculture.

Thankfully, the majority of the Earth’s peatlands remain undisturbed. Jean-Yves Daigle, outgoing chair of the Canadian National Committee of the International Peat Society, estimates that there are around 1.5 million square miles of peatland on Earth. This figure only scratches the surface: Square miles measure surface area, but peat deposits can be up to 60 feet deep. (Neuzil reported this anecdotal figure in a stage whisper, as if it were a shamefully tasty rumor.) So, Daigle says, call that between 5 trillion and 6 trillion tons. He reckons that we are using about 0.05 percent of this resource every year. If the trend holds, and if the incidence of peatland fires—such as one that burned uncontrollably in Minnesota last year—doesn’t increase dramatically, that works out to another 2,000 years of Scotch.

However, Neuzil told me that if peat were used only to make Scotch, its most noble purpose (my words, not hers), the supply would never run out. Accumulation would keep pace with consumption, and from now until the end of time there would be Scotch on Earth.

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