New theory on how Earth's crust was created

A composite image of the Western hemisphere of the Earth. Credit: NASA

More than 90% of Earth's continental crust is made up of silica-rich minerals, such as feldspar and quartz. But where did this silica-enriched material come from? And could it provide a clue in the search for life on other planets?

Conventional theory holds that all of the early Earth's crustal ingredients were formed by volcanic activity. Now, however, McGill University earth scientists Don Baker and Kassandra Sofonio have published a theory with a novel twist: some of the chemical components of this material settled onto Earth's early surface from the steamy atmosphere that prevailed at the time.
First, a bit of ancient geochemical history: Scientists believe that a Mars-sized planetoid plowed into the proto-Earth around 4.5 billion years ago, melting the Earth and turning it into an ocean of magma. In the wake of that impact—which also created enough debris to form the moon—the Earth's surface gradually cooled until it was more or less solid. Baker's new theory, like the conventional one, is based on that premise.
The atmosphere following that collision, however, consisted of high-temperature steam that dissolved rocks on the Earth's immediate surface—"much like how sugar is dissolved in coffee," Baker explains. This is where the new wrinkle comes in. "These dissolved minerals rose to the upper atmosphere and cooled off, and then these silicate materials that were dissolved at the surface would start to separate out and fall back to Earth in what we call a silicate rain."
To test this theory, Baker and co-author Kassandra Sofonio, a McGill undergraduate research assistant, spent months developing a series of laboratory experiments designed to mimic the steamy conditions on early Earth. A mixture of bulk silicate earth materials and water was melted in air at 1,550 degrees Celsius, then ground to a powder. Small amounts of the powder, along with water, were then enclosed in gold palladium capsules, placed in a pressure vessel and heated to about 727 degrees Celsius and 100 times Earth's surface pressure to simulate conditions in the Earth's atmosphere about 1 million years after the moon-forming impact. After each experiment, samples were rapidly quenched and the material that had been dissolved in the high temperature steam analyzed.
The experiments were guided by other scientists' previous experiments on rock-water interactions at high pressures, and by the McGill team's own preliminary calculations, Baker notes. Even so, "we were surprised by the similarity of the dissolved silicate material produced by the experiments" to that found in the Earth's crust.
Their resulting paper, published in the journal Earth and Planetary Science Letters, posits a new theory of "aerial metasomatism"—a term coined by Sofonio to describe the process by which silica minerals condensed and fell back to earth over about a million years, producing some of the earliest rock specimens known today.
"Our experiment shows the chemistry of this process," and could provide scientists with important clues as to which exoplanets might have the capacity to harbor life Baker says.
"This time in early Earth's history is still really exciting," he adds. "A lot of people think that life started very soon after these events that we're talking about. This is setting up the stages for the Earth being ready to support life."

Violating law of energy conservation in the early universe may explain dark energy

This is the "South Pillar" region of the star-forming region called the Carina Nebula. Like cracking open a watermelon and finding its seeds, the infrared telescope "busted open" this murky cloud to reveal star embryos tucked inside finger-like pillars of thick dust. Credit: NASA

Physicists have proposed that the violations of energy conservation in the early universe, as predicted by certain modified theories in quantum mechanics and quantum gravity, may explain the cosmological constant problem, which is sometimes referred to as "the worst theoretical prediction in the history of physics."

The physicists, Thibaut Josset and Alejandro Perez at the University of Aix-Marseille, France, and Daniel Sudarsky at the National Autonomous University of Mexico, have published a paper on their proposal in a recent issue Physical Review Letters.
"The main achievement of the work was the unexpected relation between two apparently very distinct issues, namely the accelerated expansion of the universe and microscopic physics," Josset told Phys.org. "This offers a fresh look at the cosmological constant problem, which is still far from being solved."
Einstein originally proposed the concept of the cosmological constant in 1917 to modify his theory of general relativity in order to prevent the universe from expanding, since at the time the universe was considered to be static.
Now that modern observations show that the universe is expanding at an accelerating rate, the cosmological constant today can be thought of as the simplest form of dark energy, offering a way to account for current observations.
However, there is a huge discrepancy—up to 120 orders of magnitude—between the large theoretical predicted value of the cosmological constant and the tiny observed value. To explain this disagreement, some research has suggested that the cosmological constant may be an entirely new constant of nature that must be measured more precisely, while another possibility is that the underlying mechanism assumed by theory is incorrect. The new study falls into the second line of thought, suggesting that scientists still do not fully understand the root causes of the cosmological constant.
The basic idea of the new paper is that violations of energy conservation in the early universe could have been so small that they would have negligible effects at local scales and remain inaccessible to modern experiments, yet at the same time these violations could have made significant contributions to the present value of the cosmological constant.

To most people, the idea that conservation of energy is violated goes against everything they learned about the most fundamental laws of physics. But on the cosmological scale, conservation of energy is not as steadfast a law as it is on smaller scales. In this study, the physicists specifically investigated two theories in which violations of energy conservation naturally arise.
The first scenario of violations involves modifications to quantum theory that have previously been proposed to investigate phenomena such as the creation and evaporation of black holes, and which also appear in interpretations of quantum mechanics in which the wavefunction undergoes spontaneous collapse. In these cases, energy is created in an amount that is proportional to the mass of the collapsing object.
Violations of energy conservation also arise in some approaches to quantum gravity in which spacetime is considered to be granular due to the fundamental limit of length (the Planck length, which is on the order of 10^-35 m). This spacetime discreteness could have led to either an increase or decrease in energy that may have begun contributing to the cosmological constant starting when photons decoupled from electrons in the early universe, during the period known as recombination.
As the researchers explain, their proposal relies on a modification to general relativity called unimodular gravity, first proposed by Einstein in 1919.
"Energy from matter components can be ceded to the gravitational field, and this 'loss of energy' will behave as a cosmological constant—it will not be diluted by later expansion of the universe," Josset said. "Therefore a tiny loss or creation of energy in the remote past may have significant consequences today on large scale."
Whatever the source of the energy conservation violation, the important result is that the energy that was created or lost affected the cosmological constant to a greater and greater extent as time went by, while the effects on matter decreased over time due to the expansion of the universe.
Another way to put it, as the physicists explain in their paper, is that the cosmological constant can be thought of as a record of the energy non-conservation during the history of the universe.
Currently there is no way to tell whether the violations of energy conservation investigated here truly did affect the cosmological constant, but the physicists plan to further investigate the possibility in the future.
"Our proposal is very general and any violation of energy conservation is expected to contribute to an effective cosmological constant," Josset said. "This could allow to set new constraints on phenomenological models beyond standard quantum mechanics.
"On the other hand, direct evidence that dark energy is sourced by energy non-conservation seems largely out-of-reach, as we have access to the value of lambda [the cosmological constant] today and constraints on its evolution at late time only."

Credit: Lisa Zyga  

 

Energy scenarios that actually provide useful decision-support tools for policymakers and investors

Fulfilling the promise of the 2015 Paris Agreement on climate change—most notably the goal of limiting the rise in mean global surface temperature since preindustrial times to 2 degrees Celsius—will require a dramatic transition away from fossil fuels and toward low-carbon energy sources. To map out that transition, decision-makers routinely turn to energy scenarios, which use computational models to project changes to the energy mix that will be needed to meet climate and environmental targets. These models account for not only technological, economic, demographic, political, and institutional developments, but also the scope, timing, and stringency of policies to reduce greenhouse gas emissions and air pollution.

Credit: David Pilbrow/Flickr

Model-driven energy scenarios provide policymakers and investors with a powerful decision-support tool but should not be used as a decision-making tool due to several limitations. So argues a new study in the journal Energy and Environment by Sergey Paltsev, deputy director of the MIT Joint Program on the Science and Policy of Global Change and a senior research scientist for both the Joint Program and the MIT Energy Initiative. The study shows that overall, energy scenarios are useful for assessing policymaking and investment risks associated with different emissions reduction pathways, but tend to overestimate the degree to which future energy demand will resemble the past.
"Energy scenarios may not provide exact projections, but they are the best available tool to assess the magnitude of challenges that lie ahead," Paltsev observes in the study, a unique review of the value and limits of widely used energy scenarios that range from the International Energy Agency (IEA) World Energy Outlook, to the Joint Program's own annual Food, Water, Energy and Climate Outlook (which uses the MIT Economic Projection and Policy Analysis model), to a recent Intergovernmental Panel on Climate Change (IPCC) assessment report (AR5) presenting 392 energy scenarios aligned with the 2 C climate stabilization goal.
The study points out that because energy scenarios tend to vary widely in terms of the projections they produce for a given policy and the degree of uncertainty associated with those projections, it's not advisable to base an energy policy or investment decision on a single energy scenario. Taken collectively, however, energy scenarios can help bring into sharp focus a range of plausible futures—information decision-makers can use to assess the scale and cost of the technological changes needed to effect significant transformations in energy production and consumption. A careful review of multiple energy scenarios associated with a particular emissions pathway can provide a qualitative analysis of what's driving the results and the potential risks and benefits of a proposed policy or investment.

That said, projections in energy scenarios can sometimes be highly inaccurate due to factors that are difficult to anticipate.
For example, according to the study, which compared several energy scenario projections to historical observations, most energy scenarios do not account for sudden changes to the status quo. One of the greatest contributors to uncertainty in energy scenarios is the demand for low-emitting energy technologies, whose timing and scale of deployment—dependent on several economic and political factors—is highly unpredictable. Paltsev notes that the IEA constantly underestimates renewable energy production; in its 2006 World Energy Outlook, the agency projected for 2020 a level of wind power generation that the world exceeded as early as 2013.
In addition, while energy scenarios have been largely successful in projecting the quantity of global energy demand (e.g., the 1994 IEA World Energy Outlook's projection for 2010 was off by only 10 percent, despite highly disruptive developments such as the breakup of the Soviet Union, the world recession in 2008, and the emergence of the shale gas industry), most have been considerably off the mark when it comes to projecting energy prices (e.g., in 1993 dollars, the 1994 IEA WEO projected $28/barrel in 2010, but the actual price was $53/barrel).
Recognizing the steep challenge in projecting demand and prices for different energy sources in the midst of a dramatic energy transition, Paltsev emphasizes that governments should not try to pick a "winner"—a single energy technology that seems poised to reduce emissions singlehandedly—but rather adopt a strategy that targets emissions reductions from any energy source.
"Governments shouldn't pick the winners, because most likely that choice will be wrong," he says. "They should instead design policies such as carbon-pricing and emissions trading systems that are designed to achieve emissions reduction targets at the least cost."

credit: Mark Dwortzan 

SpaceX set to launch for first time since Sept blast

the above picture is the Falcon 9 rocket

SpaceX is poised to blast off a Falcon 9 rocket on Saturday, marking its first return to flight since a costly and complicated launchpad explosion in September.

The launch of 10 satellites for Iridium, a mobile and data communications company, is scheduled from Vandenberg Air Force Base in California at 9:54 am (1754 GMT).
The launch window is "instantaneous," meaning that any technical glitch or poor weather—the current forecast is just 60 percent favorable—would push the launch forward to the next opportunity on Sunday at 1749 GMT.
The stakes for SpaceX are high after a pair of accidents.
September's blast destroyed a $200 million satellite Facebook had planned to use to beam high-speed internet to Africa. Another explosion in June 2015 two minutes after liftoff obliterated a Dragon cargo ship packed with goods bound for the astronauts at the International Space Station.
The incidents cost SpaceX dearly, possibly pushing the privately owned company into the red, the Wall Street Journal reported this week.
"That June 2015 disaster, followed by months of launch delays, contributed to a quarter-billion dollar annual loss and a six percent drop in revenue, after two years of surging sales and small profits," the paper said after a review of internal financial documents from 2011 to 2015, forecasts for the next decade and interviews with former SpaceX employees.
Three weeks after last September's accident, the company removed a long-standing phrase from its website saying it was "profitable and cash-flow positive."
That "suggest(ed) both profit and cash flow had moved into the red for 2016," the Journal said, noting that it found an operating loss for every quarter in 2016 and negative cash flow of roughly $15 million.
SpaceX, headed by billionaire entrepreneur Elon Musk, declined to comment on the findings and is not obligated to release its financial figures because it is a private company, the report said.
"The company is in a financially strong position and is well positioned for future growth," with $1 billion in cash and no debt, SpaceX chief financial officer Bret Johnson was quoted as saying.

Problems fixed
The June 2015 accident—in which the unmanned Dragon cargo ship exploded in a massive fireball two minutes after launch—was caused by a faulty strut that allowed a helium tank to snap loose, SpaceX said.
Last September's explosion, during a test a day prior to a scheduled launch, was traced to a problem with a pressure vessel in the second-stage liquid oxygen tank.
SpaceX said it will change the way it fuels for now and redesign its pressure vessels in the future.
Musk, who cofounded PayPal and also owns Tesla Motors, has lofty goals, including colonizing Mars and revolutionizing the launch industry by making rocket components reusable.
Founded in 2002, SpaceX logged 18 successful launches of the Falcon 9 before the 2015 accident.
The company has a $1.6 billion contract with NASA to supply the International Space Station using its Dragon space capsule, which is the only cargo ship that can return to the Earth intact.
SpaceX had hoped to resume Falcon 9 flights as early as November, then in mid-December, before pushing the date to January.

scientists find that Solar cells can be made with tin instead of lead

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Credit: University of Warwick

A breakthrough in solar power could make it cheaper and more commercially viable, thanks to research at the University of Warwick.

In a paper published in Nature Energy, Dr Ross Hatton, Professor Richard Walton and colleagues, explain how solar cells could be produced with tin, making them more adaptable and simpler to produce than their current counterparts.
Solar cells based on a class of semiconductors known as lead perovskites are rapidly emerging as an efficient way to convert sunlight directly into electricity. However, the reliance on lead is a serious barrier to commercialisation, due to the well-known toxicity of lead.
Dr Ross Hatton and colleagues show that perovskites using tin in place of lead are much more stable than previously thought, and so could prove to be a viable alternative to lead perovskites for solar cells.
Lead-free cells could render solar power cheaper, safer and more commercially attractive - leading to it becoming a more prevalent source of energy in everyday life.
This could lead to a more widespread use of solar power, with potential uses in products such as laptop computers, mobile phones and cars.
The team have also shown how the device structure can be greatly simplified without compromising performance, which offers the important advantage of reduced fabrication cost.
Dr Hatton comments that there is an ever-pressing need to develop renewable sources of energy:
"It is hoped that this work will help to stimulate an intensive international research effort into lead-free perovskite solar cells, like that which has resulted in the astonishingly rapid advancement of lead perovskite solar cells.
"There is now an urgent need to tackle the threat of climate change resulting from humanity's over reliance on fossil fuel, and the rapid development of new solar technologies must be part of the plan."
Perovskite solar cells are lightweight and compatible with flexible substrates, so could be applied more widely than the rigid flat plate silicon solar cells that currently dominate the photovoltaics market, particularly in consumer electronics and transportation applications.
The paper, 'Enhanced Stability and Efficiency in Hole-Transport Layer Free CsSnI3 Perovskite Photovoltaics', is published in Nature Energy, and is authored by Dr Ross Hatton, Professor Richard Walton and PhD student Kenny Marshall in the Department of Chemistry, along with Dr Marc Walker in the Department of Physics.

2.5 billion-year-old fossils of bacteria that predate the formation of oxygen

A microscopic image of 2.5 billion-year-old sulfur-oxidizing bacterium. Credit: Andrew Czaja, UC assistant professor of geology

Somewhere between Earth's creation and where we are today, scientists have demonstrated that some early life forms existed just fine without any oxygen.

While researchers proclaim the first half of our 4.5 billion-year-old planet's life as an important time for the development and evolution of early bacteria, evidence for these life forms remains sparse including how they survived at a time when oxygen levels in the atmosphere were less than one-thousandth of one percent of what they are today.
Recent geology research from the University of Cincinnati presents new evidence for bacteria found fossilized in two separate locations in the Northern Cape Province of South Africa.
"These are the oldest reported fossil sulfur bacteria to date," says Andrew Czaja, UC assistant professor of geology. "And this discovery is helping us reveal a diversity of life and ecosystems that existed just prior to the Great Oxidation Event, a time of major atmospheric evolution."
The 2.52 billion-year-old sulfur-oxidizing bacteria are described by Czaja as exceptionally large, spherical-shaped, smooth-walled microscopic structures much larger than most modern bacteria, but similar to some modern single-celled organisms that live in deepwater sulfur-rich ocean settings today, where even now there are almost no traces of oxygen.

UC Professor Andrew Czaja indicates the layer of rock from which fossil bacteria were collected on a 2014 field excursion near the town of Kuruman in the Northern Cape Province of South Africa. Credit: Aaron Satkoski, UWM postdoc on the excursion.

In his research published in the December issue of the journal Geology of the Geological Society of America, Czaja and his colleagues Nicolas Beukes from the University of Johannesburg and Jeffrey Osterhout, a recently graduated master's student from UC's department of geology, reveal samples of bacteria that were abundant in deep water areas of the ocean in a geologic time known as the Neoarchean Eon (2.8 to 2.5 billion years ago).
"These fossils represent the oldest known organisms that lived in a very dark, deep-water environment," says Czaja. "These bacteria existed two billion years before plants and trees, which evolved about 450 million years ago. We discovered these microfossils preserved in a layer of hard silica-rich rock called chert located within the Kaapvaal craton of South Africa."
With an atmosphere of much less than one percent oxygen, scientists have presumed that there were things living in deep water in the mud that didn't need sunlight or oxygen, but Czaja says experts didn't have any direct evidence for them until now.

Czaja argues that finding rocks this old is rare, so researchers' understanding of the Neoarchean Eon are based on samples from only a handful of geographic areas, such as this region of South Africa and another in Western Australia.

According to Czaja, scientists through the years have theorized that South Africa and Western Australia were once part of an ancient supercontinent called Vaalbara, before a shifting and upending of tectonic plates split them during a major change in the Earth's surface.
Based on radiometric dating and geochemical isotope analysis, Czaja characterizes his fossils as having formed in this early Vaalbara supercontinent in an ancient deep seabed containing sulfate from continental rock. According to this dating, Czaja's fossil bacteria were also thriving just before the era when other shallow-water bacteria began creating more and more oxygen as a byproduct of photosynthesis.
"We refer to this period as the Great Oxidation Event that took place 2.4 to 2.2 billion years ago," says Czaja.

Microstructures here have physical characteristics consistent with the remains of compressed coccodial (round) bacteria microorganisms. Credit: Andrew Czaja, permission to publish by Geological Society of America

Early recycling
Czaja's fossils show the Neoarchean bacteria in plentiful numbers while living deep in the sediment. He contends that these early bacteria were busy ingesting volcanic hydrogen sulfide—the molecule known to give off a rotten egg smell—then emitting sulfate, a gas that has no smell. He says this is the same process that goes on today as modern bacteria recycle decaying organic matter into minerals and gases.
"The waste product from one [bacteria] was food for the other," adds Czaja.
"While I can't claim that these early bacteria are the same ones we have today, we surmise that they may have been doing the same thing as some of our current bacteria," says Czaja. "These early bacteria likely consumed the molecules dissolved from sulfur-rich minerals that came from land rocks that had eroded and washed out to sea, or from the volcanic remains on the ocean's floor.
There is an ongoing debate about when sulfur-oxidizing bacteria arose and how that fits into the earth's evolution of life, Czaja adds. "But these fossils tell us that sulfur-oxidizing bacteria were there 2.52 billion years ago, and they were doing something remarkable."

credit; Melanie Schefft