|By Gregory H. Revera (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons|
Wednesday, 3 February 2016
The moon was formed by a violent, head-on collision between the early Earth and a "planetary embryo" called Theia approximately 100 million years after the Earth formed, UCLA geochemists and colleagues report.
Scientists had already known about this high-speed crash, which occurred almost 4.5 billion years ago, but many thought the Earth collided with Theia (pronounced THAY-eh) at an angle of 45 degrees or more -- a powerful side-swipe (simulated in this 2012 YouTube video). New evidence reported Jan. 29 in the journal Science substantially strengthens the case for a head-on assault.
The researchers analyzed seven rocks brought to the Earth from the moon by the Apollo 12, 15 and 17 missions, as well as six volcanic rocks from the Earth's mantle - five from Hawaii and one from Arizona.
The key to reconstructing the giant impact was a chemical signature revealed in the rocks' oxygen atoms. (Oxygen makes up 90 percent of rocks' volume and 50 percent of their weight.) More than 99.9 percent of Earth's oxygen is O-16, so called because each atom contains eight protons and eight neutrons. But there also are small quantities of heavier oxygen isotopes: O-17, which have one extra neutron, and O-18, which have two extra neutrons. Earth, Mars and other planetary bodies in our solar system each has a unique ratio of O-17 to O-16 - each one a distinctive "fingerprint."
In 2014, a team of German scientists reported in Science that the moon also has its own unique ratio of oxygen isotopes, different from Earth's. The new research finds that is not the case.
"We don't see any difference between the Earth's and the moon's oxygen isotopes; they're indistinguishable," said Edward Young, lead author of the new study and a UCLA professor of geochemistry and cosmochemistry.
Young's research team used state-of-the-art technology and techniques to make extraordinarily precise and careful measurements, and verified them with UCLA's new mass spectrometer.
The fact that oxygen in rocks on the Earth and our moon share chemical signatures was very telling, Young said. Had Earth and Theia collided in a glancing side blow, the vast majority of the moon would have been made mainly of Theia, and the Earth and moon should have different oxygen isotopes. A head-on collision, however, likely would have resulted in similar chemical composition of both Earth and the moon.
"Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them," Young said. "This explains why we don't see a different signature of Theia in the moon versus the Earth."
Theia, which did not survive the collision (except that it now makes up large parts of Earth and the moon) was growing and probably would have become a planet if the crash had not occurred, Young said. Young and some other scientists believe the planet was approximately the same size as the Earth; others believe it was smaller, perhaps more similar in size to Mars.
Another interesting question is whether the collision with Theia removed any water that the early Earth may have contained. After the collision - perhaps tens of millions of year later - small asteroids likely hit the Earth, including ones that may have been rich in water, Young said. Collisions of growing bodies occurred very frequently back then, he said, although Mars avoided large collisions.
A head-on collision was initially proposed in 2012 by Matija, now a research scientist with the SETI Institute, and Sarah Stewart, now a professor at UC Davis; and, separately during the same year by Robin Canup of the Southwest Research Institute.
Co-authors of the Science paper are Issaku Kohl, a researcher in Young's laboratory; Paul Warren, a researcher in the UCLA department of Earth, planetary, and space sciences; David Rubie, a research professor at Germany's Bayerisches Geoinstitut, University of Bayreuth; and Seth Jacobson and Alessandro Morbidelli, planetary scientists at France's Laboratoire Lagrange, Université de Nice.
The research was funded by NASA, the Deep Carbon Observatory and a European Research Council advanced grant (ACCRETE).
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Tuesday, 26 January 2016
An antibiotic developed from human breast milk could combat certain drug-resistant bacteria, British scientists have found.
Tackling antibiotic-resistant bacteria, known as superbugs, is a priority for the government. A panel set up by David Cameron forecast that they would cost 10 million lives and £700bn a year worldwide by 2050 if the problem went unchecked.
The breakthrough, by the National Physical Laboratory (NPL) and University College London, found that the minuscule fragment, less than a nanometre in width, is responsible for giving the protein its anti-microbial properties.
This is what makes breast milk so important in protecting infants from disease in their first months of life. The protein, called lactoferrin, effectively kills bacteria, fungi and even viruses on contact.
After identifying the fragment, scientists re-engineered it into a virus-like capsule that can recognise and target specific bacteria and damage them on contact, but without affecting any surrounding human cells.
The team suggested this could help the fight against antibiotic resistance by serving as “delivery vehicles” for cures. The capsules could even pave the way for treatments for previously incurable conditions such as sickle-cell disease, cystic fibrosis and Duchenne muscular dystrophy.
In an interview with the Times, Dame Sally Davies, the chief medical officer for England, said governments and experts needed to do more to tackle the antibiotics issue. “We need on average 10 new antibiotics every decade. If others do not work with us, it’s not something we can sort on our own,” she said. “This is a global problem. I am optimistic about this. The science is crackable. It’s doable.”
Colin Garner, honorary professor of pharmacology at the University of York and head of the charity Antibiotic Research UK, said the situation was too urgent to wait for international consensus. “The pipeline of new drugs had dried up and the problem was on the brink of becoming intractable, he told the Times.
“My heart sinks when I hear the term ‘global initiative’. How long has it taken the world to come to a sort of consensus about climate change?” he said.
“The problem of antibiotic resistance will be at least as intractable, because each nation takes a different view of what is required.”
The NPL findings are reported in the Royal Society of Chemistry journal Chemical Science.
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Tuesday, 19 January 2016
The next ice age may have been delayed by over 50,000 years because of the greenhouse gases put in the atmosphere by humans, scientists in Germany say.
They analysed the trigger conditions for a glaciation, like the one that gripped Earth over 12,000 years ago.
The shape of the planet's orbit around the Sun would be conducive now, they find, but the amount of carbon dioxide currently in the air is far too high.
Earth is set for a prolonged warm phase, they tell the journal Nature.
"In theory, the next ice age could be even further into the future, but there is no real practical importance in discussing whether it starts in 50,000 or 100,000 years from now," Andrey Ganopolski from the Potsdam Institute for Climate Impact Research said.
"The important thing is that it is an illustration that we have a geological power now. We can change the natural sequence of events for tens of thousands of years," he told BBC News.
|The Earth seen from space|
Earth has been through a cycle of ice ages and warm periods over the past 2.5 million years, referred to as the Quaternary Period.
This has seen ice sheets come and go. At its maximum extent, the last glaciation witnessed a big freeze spread over much of North America, northern Europe, Russia and Asia.
In the south, a vast expanse of what are now Chile and Argentina were also iced up.
A fundamental parameter determining what dips Earth into an ice age is the changing nature of its orbit around the Sun.
The passage around the star is not a perfect circle and over time our planet's axis of rotation also rocks back and forth.
These movements alter the amount of solar radiation falling on the Earth's surface, and if a critical threshold is reached in mid latitudes in the Northern Hemisphere then a glaciation can be initiated.
Dr Ganopolski colleagues confirm this in their modelling but show also the role played by the concentration of greenhouse gases in the atmosphere.
And one of their findings is that Earth probably missed the inception by only a narrow margin a few hundred years ago, just before the industrial revolution took hold.
"We are now in a period when our (northern) summer is furthest from the Sun," the Potsdam researcher explained.
"Under normal circumstances, the interglacial would be terminated, and a new ice age would start. So, in principle, we are in the perfect conditions from an astronomical point of view. If we had a CO2 concentration of 240 parts per million (200 years ago) then an ice age could start, but luckily we had a concentration that was higher, 280ppm." Today, industrial society has taken that concentration to over 400ppm.
The team says that an interglacial climate would probably have been sustained anyway for at least 20,000 years, and, very probably, for 50,000 years, even if CO2 had stayed at its eighteenth century level.
But the almost 500 gigatonnes of carbon that has been released since the Industrial Revolution means we will likely miss the next best astronomical entry point into a glaciation, and with a further 500 gigatonnes of emissions the "probability of glacial inception during the next 100,000 years is notably reduced", the scientists say in their Nature paper.
Add a further 500 Gt C on top of that and the next ice age is virtually guaranteed to be delayed beyond the next 100,000 years.
Commenting on the study, Prof Eric Wolff from the University of Cambridge, UK, said: "There have been previous papers suggesting that the next ice age is many tens of thousands of years away, and that the combination of seasonal solar energy at the latitude where an ice sheet would form, plus CO2, is what determines the onset of an ice age. But this paper goes much further towards quantifying where the limits are.
"It represents a nice confirmation that there is a relatively simple way of estimating the combination of insolation and CO2 to start an ice age," he told the Science Media Centre.
And Prof Chris Rapley, from University College London, added: "This is an interesting result that provides further evidence that we have entered a new geological [Epoch] - 'The Anthropocene' - in which human actions are affecting the very metabolism of the planet."
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Wednesday, 13 January 2016
In 1404, English alchemists were forbidden to use their knowledge to create precious metals. Since the time of Roger Bacon, it had fascinated the imagination of many ardent men in England. During the reign of Henry IV, the Act of Multipliers was passed by the Parliament, declaring the use of transmutation to “multiply” gold and silver to be felony. Great alarm was felt at that time lest any alchemist should succeed in his projects, and perhaps bring ruin upon the state, by furnishing boundless wealth to some designing tyrant, who would make use of it to enslave his country. In 1689, Robert Boyle lobbied for repeal of the Act.
|The world's largest gold bar, by PHGCOM (Own work by uploader, Toi Mine) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons|
What is Alchemy?
Alchemy is a philosophical and protoscientific tradition practiced throughout Egypt and Eurasia which aimed to purify, mature, and perfect certain objects. Common aims were chrysopoeia, the transmutation of "base metals" (e.g. lead) into "noble" ones (particularly gold); the creation of an elixir of immortality; the creation of panaceas able to cure any disease; and the development of an alkahest, a universal solvent. The perfection of the human body and soul was thought to permit or result from the alchemical magnum opus and, in the Hellenistic and western tradition, the achievement of gnosis. In Europe, the creation of a philosopher's stone was variously connected with all of these projects.
In English, the term is often limited to descriptions of European alchemy, but similar practices existed in the Far East, the Indian subcontinent, and the Muslim world. In Europe, following the 12th-century Renaissance produced by the translation of Arabic works on science and the Recovery of Aristotle, alchemists played a significant role in early modern science (particularly chemistry and medicine). Islamic and European alchemists developed a structure of basic laboratory techniques, theory, terminology, and experimental method, some of which are still in use today. However, they continued antiquity's belief in four elements and guarded their work in secrecy including cyphers and cryptic symbolism. Their work was guided by Hermetic principles related to magic, mythology, and religion.
Modern discussions of alchemy are generally split into an examination of its exoteric practical applications and its esoteric spiritual aspects, despite the arguments of scholars like Homyard and von Franz that they should be understood as complementary. The former is pursued by historians of the physical sciences who examine the subject in terms of protochemistry, medicine, and charlatanism. The latter interests historians of esotericism, psychologists, and some philosophers and spiritualists. The subject has also made an ongoing impact on literature and the arts. Despite this split, which von Franz believes has existed since the Western traditions' origin in a mix of Greek philosophy was mixed with Egyptian and Mesopotamian technology, numerous sources have stressed an integration of esoteric and exoteric approaches to alchemy as far back as Bolus of Mendes's 3rd-century bc On Physical and Mystical Matters (Greek: Physika kai Mystika).
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Tuesday, 5 January 2016
Oxygen is crucial for the existence of animals on Earth. But, an increase in oxygen did not apparently lead to the rise of the first animals. New research shows that 1.4 billion years ago there was enough oxygen for animals - and yet over 800 million years went by before the first animals appeared on Earth.
|The Earth seen from Apollo 17 by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans|
Animals evolved by about 600 million years ago, which was late in Earth's history. The late evolution of animals, and the fact that oxygen is central for animal respiration, has led to the widely promoted idea that animal evolution corresponded with a late a rise in atmospheric oxygen concentrations.
"But sufficient oxygen in itself does not seem to be enough for animals to rise. This is indicated by our studies," say postdoc Emma Hammarlund and Professor Don Canfield, Nordic Center for Earth Evolution, University of Southern Denmark.
Together with colleagues from the China National Petroleum Corporation and the University of Copenhagen, Hammarlund and Canfield have analyzed sediment samples from the Xiamaling Formation in China. Their analyses reveal that a deep ocean 1.4 billion years ago contained at least 4% of modern oxygen concentrations.
The new study is published in the journal Proceedings of National Academy of Sciences.
Usually it is very difficult to precisely determine past oxygen concentrations. The new study, however, combines several approaches to break new ground in understanding oxygen concentrations 1.4 billion years ago.
The study uses trace metal distributions to show that the bottom waters where the Xiamaling Formation sediments deposited contain oxygen. The distribution of biomarkers, molecules derived from ancient organisms, demonstrate that waters of intermediate depth contain no oxygen. Therefore, the Xiamaling Formation deposited in an ancient oxygen-minimum zone, similar to (but also different) from those found off the present coasts of Chile and Peru.
With this backdrop, the researchers used a simple ocean model to estimate the minimum concentrations to atmospheric oxygen required to reproduce the distribution of water-column oxygen in the Xiamaling Formation.
"The water column had an oxygen concentration at least 4 % of present atmospheric levels (PAL). That should be sufficient for animals to exist and evolve," says Canfield.
"Having determined the lowest concentration of oxygen in the air almost one and a half billion years ago is unique," says Hammarlund, adding:
"Researchers know of simple animals, such as sponges and worms, that today are capable of managing with less than 4% PAL, even much less."
"Sponges probably resemble some of the first animals on Earth. If they manage with less than 4 % today's oxygen levels, it is likely that the first animals could do with these concentrations or less," says Canfield.
The results differ from other studies and raise several questions, such as: Why then did animals rise so late in Earth's history?
"The sudden diversification of animals probably was a result of many factors. Maybe the oxygen rise had less to do with the animal revolution than we previously assumed," says Hammarlund.
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Tuesday, 29 December 2015
In 1927, Krakatoa began a new volcanic eruption on the seafloor along the same line as the cones of previous activity. By 26 Jan 1928, a growing cone had reached sea level and formed a small island called Anak Krakatoa (Child of Krakatoa). Sporadic activity continued until, by 1973, the island had reached a height of 622 ft above sea level. It was still in eruption in the early 1980s. The volcano Krakatoa is on Pulau (island) Rakata in the Sunda Strait between Java and Sumatra, Indonesia. It had been quiet since its previous catastrophic eruption of 1883. That threw sulphur and pumice 33 miles high and 36,380 people were killed either by the ash fall or by the resulting tidal wave. The only earlier known eruption was in 1680, and was only moderate.
|Volcano, by ISS Crew Earth Observations experiment and the Image Science & Analysis Group, Johnson Space Center. [Public domain], via Wikimedia Commons|
The combination of pyroclastic flows, volcanic ash, and tsunamis had disastrous results in the region. There were no survivors from the 3,000 people located on the island of Sebesi, about 13 km (8.1 mi) from Krakatoa. Pyroclastic flows killed around 1,000 people at Ketimbang on the coast of Sumatra some 48 km (30 mi) north from Krakatoa. The official death toll recorded by the Dutch authorities was 36,417, although some sources put the estimate at 120,000 or more. Many settlements were destroyed, including Teluk Betung (Bandar Lampung), and Sirik and Serang in Java. The areas of Banten on Java and Lampung on Sumatra were devastated. There are numerous documented reports of groups of human skeletons floating across the Indian Ocean on rafts of volcanic pumice and washing up on the east coast of Africa, up to a year after the eruption. Some land on Java was never repopulated; it reverted to jungle, and is now the Ujung Kulon National Park.
Ships as far away as South Africa rocked as tsunamis hit them, and the bodies of victims were found floating in the ocean for months after the event. The tsunamis which accompanied the eruption are believed to have been caused by gigantic pyroclastic flows entering the sea; each of the four great explosions was accompanied by massive pyroclastic flows resulting from the gravitational collapse of the eruption columns.This caused several cubic kilometers of material to enter the sea, displacing an equally huge volume of seawater. The town of Merak was destroyed by a tsunami 46 m (151 ft) high. Some of the pyroclastic flows reached the Sumatran coast as much as 40 km (25 mi) away, having apparently moved across the water on a cushion of superheated steam. There are also indications of submarine pyroclastic flows reaching 15 km (9.3 mi) from the volcano.
Tuesday, 22 December 2015
New Mars rover findings revealed - much higher concentrations of silica indicate 'considerable water activity'
New findings by NASA's Mars Curiosity rover are the focus of a press conference this morning at the American Geophysical Union (AGU) meeting in San Francisco, Calif. A group of scientists, including one from Los Alamos National Laboratory, revealed that the Curiosity rover found much higher concentrations of silica at some sites the rover has investigated in the past seven months than anywhere else it has visited since landing on Mars 40 months ago. Silica makes up nine-tenths of the composition of some of the rocks.
|Mars, by NASA, ESA, and The Hubble Heritage Team (STScI/AURA)|
"The high silica was a surprise," said Jens Frydenvang of Los Alamos National Laboratory and the University of Copenhagen, also a Curiosity science team member. "While we're still working with multiple hypotheses on how the silica got so enriched, these hypotheses all require considerable water activity, and on Earth high silica deposits are often associated with environments that provide excellent support for microbial life. Because of this, the science team agreed to make a rare backtrack to investigate it more."
The first discovery was as Curiosity approached the area "Marias Pass," where a lower geological unit contacts an overlying one. ChemCam, the rover's laser-firing instrument for checking rock composition from a distance, detected bountiful silica in some targets the rover passed along the way to the contact zone. The ChemCam instrument was developed at Los Alamos in partnership with the French IRAP laboratory in Toulouse and the French Space Agency.
Adding information about silica clues was a major emphasis in rover operations over a span of four months and a distance of about one-third of a mile (half a kilometer). It involves many more readings from ChemCam, plus elemental composition measurements by the Alpha Particle X-ray Spectrometeter (APXS) on the rover's arm and mineral identification of drilled rock-powder samples analyzed by the Chemistry and Mineralogy (CheMin) instrument inside the rover.
Curiosity's science team is working with two main hypotheses to explain the recent findings on Mount Sharp, both of which require water. Water that is acidic would tend to carry other ingredients away and leave silica behind. Alkaline or neutral water could bring in dissolved silica that would be deposited from the solution. Apart from presenting a puzzle about the history of the region where Curiosity is working, the recent findings on Mount Sharp have intriguing threads to what an earlier rover, Spirit, found halfway around Mars. There, signs of sulfuric acidity were observed.
Adding to the puzzle, some of the silica found at one rock Curiosity drilled, called "Buckskin," is in a mineral named tridymite, which is found in Bandelier tuff, common in New Mexico but rare elsewhere, and never before seen on Mars. The usual origin of tridymite on Earth involves high temperatures in igneous or metamorphic rocks, but the finely layered sedimentary rocks examined by Curiosity have been interpreted as lakebed deposits.
Curiosity has been studying geological layers of Mount Sharp, starting from the bottom, since 2014, following two years of productive work on the plains surrounding the mountains. The mission delivered evidence in its first year that lakes in the area billions of years ago offered favorable conditions for life, if microbes ever lived on Mars. As Curiosity studies successively younger layers up Mount Sharp's slopes, the mission is investigating how ancient environmental conditions evolved from lakes, rivers and deltas to the harsh aridity of today's Mars.
Buckskin was the first of three rocks where drilled samples were collected during that period. The CheMin identification of tridymite prompted the team to look at possible explanations for it: "We could solve this by determining whether trydymite in the sediment comes from a volcanic source or has another origin," said Liz Rampe, of Aerodyne Industries at NASA's Johnson Space Center. "A lot of us are in our labs trying to see if there's a way to make tridymite without such a high temperature."
Beyond Marias Pass, ChemCam and APXS readings showed a pattern of high silica in pale zones along fractures in the bedrock, linking the silica enrichment there to alteration by fluids that flowed through the fractures and permeated into the bedrock. CheMin analyzed drilled material from a target called "Big Sky" in bedrock away from a fracture and from a fracture-zone target called "Greenhorn." Greenhorn indeed has much more silica, but not any in the form of tridymite. Much of it is in the form of noncrystalline opal, which can form in many types of environments, including hot springs, acid leaching and other wet settings.
"What we're seeing on Mount Sharp is dramatically different from what we saw in the first two years of the mission," said Curiosity Project Scientist Ashwin Vasavada of JPL. "There's so much variability within relatively short distances. The silica is one indicator of how the chemistry changed. It's such a multifaceted and curious discovery, we're going to take a while figuring it out."
The ChemCam has just passed 300,000 laser shots on Mars, each of which returns a color spectrum of the resulting plasma.
For more about Curiosity, which is examining sand dunes this month, visit the Mars Science Laboratory webpage: mars.jpl.nasa.gov/msl/
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