|The Earth by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans.|
Tuesday, 24 November 2015
Earth's oxygen-rich atmosphere emerged in whiffs from a kind of cyanobacteria in shallow oceans around 2.5 billion years ago, according to new research from Canadian and US scientists.
These whiffs of oxygen likely happened in the following 100 million years, changing the levels of oxygen in Earth's atmosphere until enough accumulated to create a permanently oxygenated atmosphere around 2.4 billion years ago - a transition widely known as the Great Oxidation Event.
"The onset of Earth's surface oxygenation was likely a complex process characterized by multiple whiffs of oxygen until a tipping point was crossed," said Brian Kendall, a professor of Earth and Environmental Sciences at the University of Waterloo. "Until now, we haven't been able to tell whether oxygen concentrations 2.5 billion years ago were stable or not. These new data provide a much more conclusive answer to that question."
The findings are presented in a paper published this month in Science Advances from researchers at Waterloo, University of Alberta, Arizona State University, University of California Riverside, and Georgia Institute of Technology. The team presents new isotopic data showing that a burst of oxygen production by photosynthetic cyanobacteria temporarily increased oxygen concentrations in Earth's atmosphere.
"One of the questions we ask is: 'did the evolution of photosynthesis lead directly to an oxygen-rich atmosphere? Or did the transition to today's world happen in fits and starts?" said Professor Ariel Anbar of Arizona State University. "How and why Earth developed an oxygenated atmosphere is one of the most profound puzzles in understanding the history of our planet."
The new data supports a hypothesis proposed by Anbar and his team in 2007. In Western Australia, they found preliminary evidence of these oxygen whiffs in black shales deposited on the seafloor of an ancient ocean.
The black shales contained high concentrations of the elements molybdenum and rhenium, long before the Great Oxidation Event.
These elements are found in land-based sulphide minerals, which are particularly sensitive to the presence of atmospheric oxygen. Once these minerals react with oxygen, the molybdenum and rhenium are released into rivers and eventually end up deposited on the sea floor.
In the new paper, researchers analyzed the same black shales for the relative abundance of an additional element: osmium. Like molybdenum and rhenium, osmium is also present in continental sulfide minerals. The ratio of two osmium isotopes - 187Os to 188Os - can tell us if the source of osmium was continental sulfide minerals or underwater volcanoes in the deep ocean.
The osmium isotope evidence found in black shales correlates with higher continental weathering as a result of oxygen in the atmosphere. By comparison, slightly younger deposits with lower molybdenum and rhenium concentrations had osmium isotope evidence for less continental input, indicating the oxygen in the atmosphere had disappeared.
The paper's authors also include Professor Robert Creaser of the University of Alberta, Professor Timothy Lyons from the University of California Riverside and Professor Chris Reinhard from the Georgia Institute of Technology.
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Wednesday, 18 November 2015
Tiny biological compasses made from clumps of protein may help scores of animals, and potentially even humans, to find their way around, researchers say.
Scientists discovered the minuscule magnetic field sensors in fruit flies, but found that the same protein structures appeared in retinal cells in pigeons’ eyes. They can also form in butterfly, rat, whale and human cells.
The rod-like compasses align themselves with Earth’s geomagnetic field lines, leading researchers to propose that when they move, they act on neighbouring cell structures that feed information into the nervous system to create a broader direction-sensing system.
Professor Can Xie, who led the work at Peking University, said the compass might serve as a “universal mechanism for animal magnetoreception,” referring to the ability of a range of animals from butterflies and lobsters to bats and birds, to navigate with help from Earth’s magnetic field.
Whether the compasses have any bearing on human navigation is unknown, but the Peking team is investigating the possibility. “Human sense of direction is complicated,” said Xie. “However, I believe that magnetic sense plays a key role in explaining why some people have a good sense of direction.”
The idea that animals could sense Earth’s magnetic field was once widely dismissed, but the ability is now well established, at least among some species. The greatest mystery that remains is how the sensing is done.
One type of molecular compass, proposed by the biologist Klaus Schulten, senses geomagnetic field information through the bizarre quantum behaviour of electrons that are produced when light falls on retinal proteins called cryptochromes. But Xie argues that a compass based on cryptochromes alone is not enough to navigate.
By screening the fruit fly genome, the Chinese team discovered a protein they named MagR, which forms rod-like clumps with cryptochrome proteins. This MagR-cryptochrome cluster behaves like a sophisticated magnetic sensor that in principle can sense the direction, intensity or inclination of Earth’s magnetic field.
“The nanoscale biocompass has the tendency to align itself along geomagnetic field lines and to obtain navigation cues from a geomagnetic field,” said Xie. “We propose that any disturbance in this alignment may be captured by connected cellular machinery, which would channel information to the downstream neural system, forming the animal’s magnetic sense.”
In a series of follow-up experiments, the scientists show that MagR-cryptochrome compass can form in a range of species, including monarch butterflies, pigeons, more rats, minke whales and humans. Details are reported in the journal Nature Materials.
Xie said the discovery could go beyond understanding how animals navigate, and lead to new technologies that allow scientists to control cell processes and influence animal behaviour with magnetic fields.
Simon Benjamin, who studies quantum materials at Oxford University, said that evolution seemed to have found a number of ways to sense magnetic fields. “It seems plausible that the structure discovered in this paper is key to the fruit fly’s compass, and perhaps other species as well.”
He added that the finding was exciting even if the MagR-cryptochrome cluster was not one of nature’s biocompasses, because it could be used to develop new technologies. “There is a continual drive for cheaper, smaller, more robust, or more sensitive field sensors. They’re needed to enable a vast range of applications from mining survey systems to map navigation with mobile phones.”
“It has been well documented that cryptochromes, which are crucial to the compass proposed in this new paper, may harness significant quantum effects to convert the Earth’s weak magnetic field into a signal in the animal’s brain.
This is a tantalising possibility since the new UK quantum technology hubs are focusing about a quarter of their £150M on sensor systems. It would be remarkable if we can learn some tricks from Mother Nature in this highly-advanced field of physics,” he added.
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Wednesday, 11 November 2015
Diamonds may not be as rare as once believed, but this finding in a new Johns Hopkins University research report won't mean deep discounts at local jewellery stores.
"Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought," said Johns Hopkins geochemist Dimitri A. Sverjensky, whose article co-written with doctoral student Fang Huang appears today in the online journal Nature Communications. The report says the results 'constitute a new quantitative theory of diamond formation,' but that does not mean it will be easier to find gem-quality diamonds and bring them to market.
|"Rough diamond" by Unknown USGS employee - Original source: USGS "Minerals in Your World" website.|
Using a chemical model, Sverjensky and Huang found that these precious stones could be born in a natural chemical reaction that is simpler than the two main processes that up to now have been understood to produce diamonds. Specifically, their model - yet to be tested with actual materials - shows that diamonds can form with an increase in acidity during interaction between water and rock.
The common understanding up to now has been that diamonds are formed in the movement of fluid by the oxidation of methane or the chemical reduction of carbon dioxide. Oxidation results in a higher oxidation state, or a gain of electrons. Reduction means a lower oxidation state, and collectively the two are known as 'redox' reactions.
"It was always hard to explain why the redox reactions took place," said Sverjensky, a professor in the Morton K. Blaustein Department of Earth and Planetary Sciences in the university's Krieger School of Arts and Sciences. The reactions require different types of fluids to be moving through the rocks encountering environments with different oxidation states.
The new research showed that water could produce diamonds as its pH falls naturally - that is, as it becomes more acidic - while moving from one type of rock to another, Sverjensky said.
The finding is one of many in about the last 25 years that expands scientists' understanding of how pervasive diamonds may be, Sverjensky said.
"The more people look, the more they're finding diamonds in different rock types now," Sverjensky said. "I think everybody would agree there's more and more environments of diamond formation being discovered."
Nobody has yet put a number on the greater abundance of diamonds, but Sverjensky said scientists are working on that with chemical models. It's impossible to physically explore the great depths at which diamonds are created: roughly 90 to 120 miles below the Earth's surface at intense pressure and at temperatures about 1,650 to 2,000 degrees Fahrenheit.
The deepest drilling exploration ever made was about 8 or 9 miles below the surface, he said.
If the study doesn't shake the diamond markets, it promises to help shed light on fluid movement in the deep Earth, which helps account for the carbon cycle on which all life on the planet depends.
"Fluids are the key link between the shallow and the deep Earth," Sverjensky said. "That's why it's important."
This research was supported by grants from the Sloan Foundation through the Deep Carbon Observatory (Reservoirs and Fluxes and Extreme Physics and Chemistry programs) and by a U.S. Energy Department grant, DE-FG-02-96ER-14616.
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Monday, 2 November 2015
On 2nd November 1931, the DuPont company, of Wilmington, Delaware, announced the first synthetic rubber. It was known as DuPrene, and from 1936 as Neoprene. Many scientists were trying to make natural rubber in the 1920s and 30s. One of the Wallace Carothers team, Gerard Berchet, had left a sample of monovinylacetylene in a jar with hydrochloric acid (HCl) for about five weeks.
Then on 17 Apr 1930, coworker Arnold M. Collins happened to look in that jar and found a rubbery white material. The HCl had reacted with the vinylacetylene, making chloroprene, which then polymerized to become polychloroprene. The new rubber was expensive, but resisted oil and gasoline, which natural rubber didn't. It was the first good synthetic rubber.
In 1935, German chemists synthesized the first of a series of synthetic rubbers known as Buna rubbers. These were copolymers, meaning the polymers were made up from two monomers in alternating sequence. Other brands included Koroseal, which Waldo Semon developed in 1935, and Sovprene, which Russian researchers created in 1940. B.F. Goodrich Company scientist Waldo Semon developed a new and cheaper version of synthetic rubber known as Ameripol in 1940.
The production of synthetic rubber in the United States expanded greatly during World War II, since the Axis powers controlled nearly all the world's limited supplies of natural rubber by mid-1942 once Japan conquered Asia. Military trucks needed rubber for tyres, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret) effort to improve synthetic rubber production. A large team of chemists from many institutions were involved, including Calvin Souther Fuller of Bell Labs. The rubber designated GRS (Government Rubber Styrene), a copolymer of butadiene and styrene, was the basis for U.S. synthetic rubber production during World War II. By 1944, a total of 50 factories were manufacturing it, pouring out a volume of the material twice that of the world's natural rubber production before the beginning of the war. It still represents about half of total world production.
Operation Pointblank bombing targets of Nazi Germany included the Schkopau (50K tons/yr) plant and the Hüls synthetic rubber plant near Recklinghausen (30K, 17%), the Kölnische Gummifäden Fabrik tire and tube plant at Deutz on the east bank of the Rhine. The Ferrara, Italy, synthetic rubber factory (near a river bridge) was bombed August 23, 1944. Three other synthetic rubber facilities were at Ludwigshafen/Oppau (15K), Hanover/Limmer (reclamation, 20K), and Leverkusen (5K). A synthetic rubber plant at Oświęcim in Nazi-occupied Poland, was under construction on March 5, 1944.
|World War Two poster about synthetic rubber tyres|
Solid-fuel rockets during World War II used nitrocellulose for propellants, but it was impractical and dangerous to make such rockets very large. During the war, California Institute of Technology (Caltech) researchers came up with a new solid fuel based on asphalt mixed with an oxidizer (such as potassium or ammonium perchlorate), and aluminium powder. This new solid fuel burned more slowly and evenly than nitrocellulose, and was much less dangerous to store and use, but it tended to slowly flow out of the rocket in storage and the rockets using it had to be stockpiled nose down.
After the war, Caltech researchers began to investigate the use of synthetic rubbers to replace asphalt in their solid fuel rocket motors. By the mid-1950s, large missiles were being built using solid fuels based on synthetic rubber, mixed with ammonium perchlorate and high proportions of aluminium powder.
Such solid fuels could be cast into large, uniform blocks that had no cracks or other defects that would cause non-uniform burning. Ultimately, all large solid-fuel military rockets and missiles would use synthetic-rubber-based solid fuels, and they would also play a significant part in the civilian space effort.
Additional refinements to the process of creating synthetic rubber continued after the war. The chemical synthesis of isoprene accelerated the reduced need for natural rubber, and the peacetime quantity of synthetic rubber exceeded the production of natural rubber by the early 1960s.
Nowadays synthetic rubber is used a great deal in printing on textiles. In this case it is called rubber paste. In most cases titanium dioxide is used with copolymerization and volatile matter in producing such synthetic rubber for textile use. Moreover, this kind of preparation can be considered to be the pigment preparation based on titanium dioxide.
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Tuesday, 27 October 2015
Comparing smoking to bacon in terms of risk of cancer is extremely misleading, despite the strength of evidence being similar.
Vegetarians are probably breathing a sigh of relief today as headlines are warning us that processed and cured meats cause cancer. But the way this message has been framed in the media is extremely misleading.
Comparing meat to tobacco, as most news organisations who’ve chosen to report this have done, makes it seem like a bacon sandwich might be just as harmful as a cigarette. This is absolutely not the case.
|A bacon sandwich|
The headlines are referring to the news that the World Health Organisation has classified cured and processed meats (bacon, salami, sausages, ham) as group 1 carcinogens, because there is a causal link between consuming these meats and bowel cancer. This group also includes tobacco, alcohol, arsenic and asbestos, all known to cause certain cancers.
But just because all these things cause cancer, doesn’t mean they’re all as risky as each other. A substance can increase your risk of cancer a small amount, or, like tobacco, a huge amount. Comparing them like for like is just really confusing to anyone trying to work out how to lead a healthy life.
The risk of lung cancer from smoking is extremely high. Of all cases of lung cancer (44,488 new cases in the UK in 2012), evidence suggests that 86% of these are caused by tobacco. And lung cancer isn’t the only type of cancer caused by smoking. CRUK estimate that 19% of all cancers are caused by smoking. Another way of looking at this is that if smoking was completely eliminated, there would be 64,500 fewer cases of cancer in the UK per year.
In contrast, the recent evidence that suggests a causal link between processed meat and bowel cancer estimates that 21% of bowel cancers (which occurs at slightly lower rates than lung cancer – 41,600 new cases in 2011) were caused by eating processed and red meat. If all such meat was eliminated entirely from our diet, they estimate that 8,800 cases of cancer would be prevented in the UK per year.
All this simplistic reporting ignores a variety of other factors – the amount you consume, for example, is likely to affect your risk a great deal. And that’s not to mention addiction – however much you crave a bacon sandwich at times, it doesn’t contain nicotine.
The WHO have deemed the strength of evidence that processed meats cause cancer to be equivalent to that showing that smoking causes cancer. This means that if you eat a lot of red or processed meats you are increasing your risk of cancer. But to compare it to something as lethal as smoking is confusing and dangerous.
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Tuesday, 20 October 2015
The European and Russian space agencies are to send a lander to an unexplored area at the Moon's south pole.
It will be one of a series of missions that prepares for the return of humans to the surface and a possible permanent settlement.
The spacecraft will assess whether there is water, and raw materials to make fuel and oxygen.
BBC News has obtained exclusive details of the mission, called Luna 27, which is set for launch in five years' time.
The mission is one of a series led by the Russian federal space agency, Roscosmos, to go back to the Moon.
These ventures will continue where the exploration programme that was halted by the Soviet Union in the mid 1970s left off, according to Prof Igor Mitrofanov, of the Space Research Institute in Moscow, who is one of the lead scientists.
"We have to go to the Moon. The 21st Century will be the century when it will be the permanent outpost of human civilisation, and our country has to participate in this process," he told BBC News.
But unlike efforts in the 1960s and 70s, when the Soviet Union was working in competition with the US and other nations, he added, "we have to work together with our international colleagues".
|Full moon: Gregory H. Revera|
Bérengère Houdou, who is the head of the lunar exploration group of at Esa's European Space Research and Technology Centre (Estec), just outside Amsterdam, has a similar strategy.
"We have an ambition to have European astronauts on the Moon. There are currently discussions at international level going on for broad cooperation on how to go back to the Moon."
One of the first acts of the new head of the European Space Agency, Johann-Dietrich Wörner, was to state that he wants international partners to build a base on the Moon's far side.
The initial missions will be robotic. Luna 27 will land on the edge of the South Pole Aitken (SPA) basin. The south polar region has areas which are always dark. These are some of the coldest places in the Solar System. As such, they are icy prisons for water and other chemicals that have been shielded from heating by the Sun.
According to Dr James Carpenter, Esa's lead scientist on the project, one of the main aims is to investigate the potential use of this water as a resource for the future, and to find out what it can tell us about the origins of life in the inner Solar System.
"The south pole of the Moon is unlike anywhere we have been before," he said.
"The environment is completely different, and due to the extreme cold there you could find large amounts of water-ice and other chemistry which is on the surface, and which we could access and use as rocket fuel or in life-support systems to support future human missions we think will go to these locations."
Back in the heady days of the Apollo missions, it seemed almost inevitable that those astounding but brief trips to the Moon would be followed by something more permanent. But the notion of colonies soon proved to be science fantasy. After the last of 12 astronauts left their boot prints in the lunar dust in 1972, the US government and taxpayers collectively declared, "been there, done that". America had scored a dazzling point over the Soviet Union but at eye-watering cost, so the final three planned Apollo missions were cancelled.
For a while, our nearest neighbour in space seemed rather unappealing. But then, over recent years, came a series of discoveries about the lunar dust itself, suggesting that the Moon holds water and minerals that could conceivably help support a settlement, if anyone has the appetite to pay for it. So a new batch of missions is under way. China seems to be particularly eager, launching increasingly capable robotic craft that could pave the way for human flights, sometime in the 2030s.
In all probability, the next boots on the Moon will be Chinese. One of China's leading space scientists told me how he even envisages opening lunar mines to extract valuable resources such as Helium-3. Throughout history, humanity has gazed at the Moon through different eyes. In the 1960s, it was the scene for Cold War rivalry. Now it is seen as a potential staging-post for longer journeys and as a rock waiting to be dug up and exploited.
Prof Mitrofanov says that there are scientific and commercial benefits to be had by building a permanent human presence on the lunar surface.
"It will be for astronomical observation, for the utilisation of minerals and other lunar resources and to create an outpost that can be visited by cosmonauts working together as a test bed for their future flight to Mars."
Esa and its industrial collaborators are developing a new type of landing system able to target areas far more precisely than the missions in the 1960s and 70s.
The so-called "Pilot" system uses on-board cameras to navigate and a laser guidance system which is able to sense the terrain while approaching the surface and be able to decide for itself whether the landing site is safe or not, and if necessary to re-target to a better location.
Europe is also providing the drill which is designed to go down to 2m and collect what might be hard, icy samples. According to Richard Fisackerly, the project's lead engineer, these samples might be harder than reinforced concrete and so the drill will need to be extremely strong.
"We are currently looking at the technologies we would need to penetrate that type of material and are looking at having both rotation and hammering functions. The final architecture has yet to be decided - but this combination of rotation, hammering and depth is a step beyond what we have already flown or is in development today," he told BBC News.
Esa will also provide the onboard miniaturised laboratory, called ProSPA. It will be similar to the instrument on the Philae lander, which touched down on the surface of Comet 67P last year. But ProSPA will be tuned to searching for the key ingredients with which to make water, oxygen, fuel and other materials that can be exploited by future astronauts.
The instrument will help scientists discover out how much of these critical resources are under the surface, and, crucially, whether they can be extracted easily.
Europe's participation in the mission is due to receive final approval at a meeting of ministers in late 2016. It has the strong support of Esa and Roscosmos hierarchy, and the scientists involved in Luna 27 are confident that it is not a question of if but when humans go back to the lunar surface.
"This whole series of missions feels like the beginning of the return to the Moon but it is also starting something new in terms of overall exploration of the Solar System," says Mr Fisackerly.
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Wednesday, 14 October 2015
By meticulously examining sediments in China's Yellow River, a Swedish-Chinese research group are showing that the history of tectonic and climate evolution on Earth may need to be rewritten.
Their findings are published today in the highly reputed journal Nature Communications.
To reconstruct how the global climate and topography of the Earth's surface have developed over millions of years, deposits of eroded land sediment transported by rivers to ocean depths are often used. This process is assumed to have been rapid and, by the same token, not to have resulted in any major storages of this sediment as large deposits along the way.
However, knowledge gaps and contradictory data in research to date are impeding an understanding of climate and landscape history. In an attempt to fill the gaps and reconcile the contradictions, the researchers have been investigating present-day and ancient sediment deposits in the world's most sediment-rich river: the Yellow River in China.
The researchers, from Uppsala University (led by Dr. Thomas Stevens) and Lanzhou University (led by Dr. Junsheng Nie), China, analysed Yellow River sediment from source to sink and determined its mineral composition. They also determined the age of mineral grains of zircon, a very hard silicate mineral that is highly resistant to weathering.
Zircon ages serve as a unique fingerprint that yields information about the sources of these sediment residues from mountain chains, according to Thomas Stevens of Uppsala University's Department of Earth Sciences, one of the principal authors of the study.
The Yellow River is believed to gain most of its sediment from wind-blown mineral dust deposits called loess, concentrated on the Chinese Loess Plateau. This plateau is the largest and one of the most important past climate archives on land, and also records past atmospheric dust activity: a major driver of climate change.
The scientists found that the composition of sediment from the Yellow River underwent radical change after passing the Chinese Loess Plateau. Contrary to their expectations, however, the windborne loess was not the main source of the sediment. Instead, they found that the Loess Plateau acts as a sink for Yellow River material eroded from the uplifting Tibetan plateau.
This finding completely changes our understanding of the origin of the Chinese Loess Plateau. It also demonstrates large scale sediment storage on land, which explains the previously contradictory findings in this area.
'Our results suggest that a major change in the monsoon around 3.6 million years ago caused the onset of Yellow River drainage, accelerated erosion of the Tibetan plateau and drove loess deposition,' Thomas Stevens writes.
Weathering of this eroded material also constitutes a further mechanism that may explain the reduced levels of atmospheric carbon dioxide at the beginning of the Ice Age. The researchers' next step will be to compare terrestrial and marine records of erosion to gauge how far sediment storage on land has impacted the marine record.
'Only then will we be able to assess the true rates of erosion and its effect on atmospheric CO2 and thus the climate in geologic time,' says Stevens.
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