Archive for the ‘Earth’ Category

A battered diamond that survived a trip from “hell” confirms a long-held theory: Earth’s mantle holds an ocean’s worth of water.

“It’s actually the confirmation that there is a very, very large amount of water that’s trapped in a really distinct layer in the deep Earth,” said Graham Pearson, lead study author and a geochemist at the University of Alberta in Canada. The findings were recently published in the journal Nature.

The worthless-looking diamond encloses a tiny piece of an olivine mineral called ringwoodite, and it’s the first time the mineral has been found on Earth’s surface in anything other than meteorites or laboratories. Ringwoodite only forms under extreme pressure, such as the crushing load about 320 miles (515 kilometers) deep in the mantle.

Most of Earth’s volume is mantle, the hot rock layer between the crust and the core. Too deep to drill, the mantle’s composition is a mystery leavened by two clues: meteorites, and hunks of rock heaved up by volcanoes. First, scientists think the composition of the Earth’s mantle is similar to that of meteorites called chondrites, which are chiefly made of olivine. Second, lava belched by volcanoes sometimes taps the mantle, bringing up chunks of odd minerals that hint at the intense heat and pressure olivine endures in the bowels of the Earth.

In recent decades, researchers have also recreated mantle settings in laboratories, zapping olivine with lasers, shooting minerals with massive guns and squeezing rocks between diamond anvils to mimic the Earth’s interior.

These laboratory studies suggest that olivine morphs into a variety of forms corresponding to the depth at which it is found. The new forms of crystal accommodate the increasing pressures. Changes in the speed of earthquake waves also support this model. Seismic waves suddenly speed up or slow down at certain depths in the mantle. Researcher think these speed zones arise from olivine’s changing configurations. For example, 323 to 410 miles (520 to 660 km) deep, between two sharp speed breaks, olivine is thought to become ringwoodite. But until now, no one had direct evidence that olivine was actually ringwoodite at this depth.

“Most people (including me) never expected to see such a sample. Samples from the transition zone and lower mantle are exceedingly rare and are only found in a few, unusual diamonds,” Hans Keppler, a geochemist at the University of Bayreuth in Germany, wrote in a commentary also published in Nature.

The diamond from Brazil confirms that the models are correct: Olivine is ringwoodite at this depth, a layer called the mantle transition zone. And it resolves a long-running debate about water in the mantle transition zone. The ringwoodite is 1.5 percent water, present not as a liquid but as hydroxide ions (oxygen and hydrogen atoms bound together). The results suggest there could be a vast store of water in the mantle transition zone, which stretches from 254 to 410 miles (410 to 660 km) deep.

“It translates into a very, very large mass of water, approaching the sort of mass of water that’s present in all the world’s ocean,” Pearson told Live Science’s Our Amazing Planet.

Plate tectonics recycles Earth’s crust by pushing and pulling slabs of oceanic crust into subduction zones, where it sinks into the mantle. This crust, soaked by the ocean, ferries water into the mantle. Many of these slabs end up stuck in the mantle transition zone. “We think that a significant portion of the water in the mantle transition zone is from the emplacement of these slabs,” Pearson said. “The transition zone seems to be a graveyard of subducted slabs.”

Keppler noted that it’s possible the volcanic eruption that brought the deep diamond to Earth’s surface may have sampled an unusually water-rich part of the mantle, and that not all of the transition-zone layer may be as wet as indicated by the ringwoodite.

“If the source of the magma is an unusual mantle reservoir, there is the possibility that, at other places in the transition zone, ringwoodite contains less water than the sample found by Pearson and colleagues,” Keppler wrote. “However, in light of this sample, models with anhydrous, or water-poor, transition zones seem rather unlikely.”

A violent volcanic eruption called a kimberlite quickly carried this particular diamond from deep in the mantle. “The eruption of a kimberlite is analogous to dropping a Mentos mint into a bottle of soda,” Pearson said. “It’s a very energetic, gas-charged reaction that blasts its way to Earth’s surface.”

The tiny, green crystal, scarred from its 325-mile (525 km) trip to the surface, was bought from diamond miners in Juína, Brazil. The mine’s ultradeep diamonds are misshapen and beaten up by their long journey. “They literally look like they’ve been to hell and back,” Pearson said. The diamonds are usually discarded because they carry no commercial value, he said, but for geoscientists, the gems provide a rare peek into Earth’s innards.

The ringwoodite discovery was accidental, as Pearson and his co-authors were actually searching for a means of dating the diamonds. The researchers think careful sample preparation is the key to finding more ringwoodite, because heating ultradeep diamonds, as happens when scientists polish crystals for analysis, causes the olivine to change shape.

“We think it’s possible ringwoodite may have been found by other researchers before, but the way they prepared their samples caused it to change back to a lower-pressure form,” Pearson said.

http://www.livescience.com/44057-diamond-inclusions-mantle-water-earth.html

bnurning earth

Scientists will this week issue their starkest warning yet about the mounting dangers of global warming. In a report to be handed to political leaders in Stockholm on Monday, they will say that the burning of fossil fuels and deforestation have now led to a warming of the entire globe, including land surfaces, oceans and the atmosphere.

Extreme weather events, including heatwaves and storms, have increased in many regions while ice sheets are dwindling at an alarming rate. In addition, sea levels are rising while the oceans are being acidified – a development that could see the planet’s coral reefs disappearing before the end of the century.

Writing in the Observer ahead of the report’s release, the economist and climate change expert Lord Stern calls on governments to end their dithering about fossil fuels and start working to create a global low-carbon economy to curtail global warming. Governments, he states, must decide what “kind of world we want to present to our children and grandchildren”.

The fifth assessment report on the physical science of climate change by the Intergovernmental Panel on Climate Change (IPCC) warns that humanity is on course over the next few decades to raise global temperatures by more than 2C compared with pre-industrial levels. Such a rise could trigger the release of plumes of the greenhouse gas methane from the thawing Arctic tundra, while the polar ice caps, which reflect solar radiation back into space, could disappear.

Although the report does not say so, Earth would probably then be facing a runaway greenhouse effect.

The scientists’ warning – the most comprehensive and convincing yet produced by climate scientists – comes at a time when growing numbers of people are doubting the reality of global warming. Last week, the UK Energy Research Centre (UKERC) published a survey showing that the proportion of British people who do not think the world’s climate is changing has almost quadrupled since 2005.

Asked if they thought Earth’s climate was changing, 5% of respondents said “no” in 2005, a figure that rose to 11% last year and reached 19% this year.

But as the IPCC report underlines, scientists are becoming more and more certain that climate change poses a real danger to the planet.

Many believe the disconnection between popular belief and scientific analysis has been engineered by “deniers” explicitly opposed to the lifestyle changes – including restrictions on fossil fuel burning – that might be introduced in the near future.

“There are attempts by some politicians and lobbyists to confuse and mislead the public about the scientific evidence that human activities are driving climate change and creating huge risks,” said Stern.

“But the public should be wary of those who claim they know for certain that unmanaged climate change would not be dangerous. For they are not only denying 200 years of strong scientific evidence – the overwhelming view of the world’s scientific academies and over 95% of scientific papers on the subject – but they are often harbouring vested interests or rigid ideologies as well.”

The report will be discussed this week by political leaders meeting in Stockholm. The study – the work of more than 200 scientists – outlines the physical changes that are likely to affect Earth’s climate this century.

Future reports will cover the social impact of these changes and the efforts required to offset the damage caused by global warming. A United Nations meeting in Paris in 2015 will then debate what actions are needed to mitigate climate change.

According to the new report, humanity has emitted about half a trillion tonnes of carbon by burning fossil fuels over the past 250 years, a process that has caused atmospheric carbon dioxide levels to rise by 40%. The world is now on target to release another half trillion tonnes in the next few decades which could trigger a major jump in global temperatures.

Most measures that have been proposed for tackling global warming rely on curtailing the burning of fossil fuels and these will form the focus of the 2015 UN meeting in Paris. Given the poor record of previous summits, many are pessimistic an agreement can be reached.

However, other measures have been suggested to curb global warming. In particular, many scientists have backed geo-engineering projects that would involve either spraying particles into the atmosphere to reflect solar radiation back into space or extracting carbon dioxide from the atmosphere in order to bury it in mines or depleted oil fields.

Both suggestions get short shrift in the new report: atmospheric aerosols could have widespread side-effects that could produce major disruptions to weather patterns, while not enough is known about the effectiveness of carbon dioxide extraction or burial. “We have to face up to the prospect of weaning ourselves off our addiction to oil and coal,” said one report author. “It is as simple as that.”

http://www.theguardian.com/environment/2013/sep/21/climate-change-ipcc-global-warming

Thanks to Mr. C for bringing this to the attention of the It’s Interesting community.

origins+of+life

Life existed long before Earth came into being, and may have originated outside our solar system, scientists claim.

Researchers say life first appeared about 10 billion years ago – long before Earth, which is believed to be 4.5 billion years old. Geneticists have applied Moore’s Law – observation that computers increase exponentially in complexity, at a rate of about double the transistors per integrated circuit every two years – to the rate at which life on Earth grows in complexity.

Alexei Sharov of the National Institute on Ageing in Baltimore, and Richard Gordon of the Gulf Specimen Marine Laboratory in Florida, replaced the transistors with nucleotides – the building blocks of DNA and RNA – and the circuits with genetic material. Their findings suggest life first appeared about 10 billion years ago, far older than the Earth’s projected age of 4.5 billion years. Like in the 2012 sci-fi movie Prometheus, as our solar system was forming, pre-existing bacteria-like organisms, or even simple nucleotides from an older part of the galaxy, could have reached Earth by hitching an interstellar ride on comets, asteroids or other inorganic space debris.

However, the calculations are not a scientific proof that life predates Earth – there’s no way of knowing for sure that organic complexity increased at a steady rate at any point in the universe’s history.

“There are lots of hypothetical elements to (our argument) … But to make a wider view, you need some hypothetical elements,” Sharov said.

Sharov said that if he had to bet on it, he’d say “it’s 99 per cent true that life started before Earth – but we should leave one per cent for some wild chance that we haven’t accounted for.”

The theory of “life before Earth,” if found true, challenges the long-held science-fiction trope of the scientifically advanced alien species. If genetic complexity progresses at a steady rate, then the social and scientific development of any other alien life form in the Milky Way galaxy would be roughly equivalent to those of humans, the report said.

“Contamination with bacterial spores from space appears the most plausible hypothesis that explains the early appearance of life on Earth,” researchers said.

http://www.phenomenica.com/2013/04/life-did-exist-before-earth-claim-scientists.html

Glints of light from cities, fires, gas flares, even unregistered fishing boats speckle the dark like fireflies in a new series of satellite images released at the American Geophysical Union’s fall meeting. The Suomi National Polar-orbiting Partnership satellite, a joint project between NASA and the National Oceanic and Atmospheric Administration, launched about a year ago and has circled Earth 5000 times. Among its instruments is the Visible Infrared Imaging Radiometer Suite (VIIRS), which has dramatically improved spatial resolution compared with its predecessor (the Defense Meteorological Satellite Program, which earlier produced images of Earth at night). VIIRS includes a sensor (called a day/night band, or DNB) that can see in low-light conditions, allowing meteorologists to study moonlit clouds. But the images suggest that scientists will want to take advantage of the DNB’s images in multiple ways: not just to study clouds, but also to assess disasters such as power outages (such as before and after Superstorm Sandy last month), to study gas flares and estimate volumes of CO2 emissions, or to keep an eye on illegal unreported fishing (the boats emit light to draw in their stocks). On moonless nights—or during the dark winter months at the poles—the instrument can study Earth’s features in the dim light of the aurora, which is particularly useful when the temperature difference between atmospheric, land, and water features is not strong enough for infrared imaging. Most surprising, though, was that the DNB can even see in the dim light of Earth’s “airglow,” chemical reactions in the upper atmosphere that produce a faint radiance an order of magnitude brighter than starlight, said atmospheric scientist Steve Miller, deputy director of the Cooperative Institute for Research in the Atmosphere in Fort Collins, Colorado, at a press conference accompanying the unveiling. The DNB “is truly a paradigm shift,” he said. “This is not your father’s low-light sensor.”