|Lunar crater Daedalus on the Moon's far side|
Wednesday, 25 May 2016
In 1961, the formal announcement of an American lunar landing was made by President John F. Kennedy speaking to the Congress: “I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth. No single space program in this period will be more impressive to mankind, or more important in the long-range exploration of space; and none will be so difficult or expensive to accomplish.”
Since, a total of twelve men have landed on the Moon. This was accomplished with two US pilot-astronauts flying a Lunar Module on each of six NASA missions across a 41-month time span starting on 20 July 1969 UTC, with Neil Armstrong and Buzz Aldrin on Apollo 11, and ending on 14 December 1972 UTC with Gene Cernan and Jack Schmitt on Apollo 17. Cernan was the last to step off the lunar surface.
All Apollo lunar missions had a third crew member who remained on board the Command Module. The last three missions had a rover for increased mobility.
The atmosphere of the moon
The Moon has an atmosphere so tenuous as to be nearly vacuum, with a total mass of less than 10 metric tons (9.8 long tons; 11 short tons). The surface pressure of this small mass is around 3 × 10−15 atm (0.3 nPa); it varies with the lunar day. Its sources include outgassing and sputtering, the release of atoms from the bombardment of lunar soil by solar wind ions. Elements that have been detected include sodium and potassium, produced by sputtering, which are also found in the atmospheres of Mercury and Io; helium-4 and neon from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle.
The absence of such neutral species (atoms or molecules) as oxygen, nitrogen, carbon, hydrogen and magnesium, which are present in the regolith, is not understood. Water vapour has been detected by Chandrayaan-1 and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the sublimation of water ice in the regolith. These gases can either return into the regolith due to the Moon's gravity or be lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field.
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Wednesday, 18 May 2016
Higher intakes of boiled, baked, or mashed potatoes, and French fries is associated with an increased risk of developing high blood pressure (hypertension) in adult women and men, according to a study published by The BMJ today.
The US-based researchers suggest that replacing one serving a day of boiled, baked, or mashed potatoes with one serving of a non-starchy vegetable is associated with a lower risk of developing hypertension.
But a linked editorial argues that studying overall dietary patterns and risk of disease is more useful than a focus on individual foods or nutrients.
|Various potato dishes by Scott Bauer (United States Department of Agriculture (link)) [Public domain], via Wikimedia Commons|
Potatoes are one of the world's most commonly consumed foods - and have recently been included as vegetables in US government healthy meals programs, due to their high potassium content. But the association of potato intake with hypertension has not been studied.
So researchers based at Brigham and Women's Hospital and Harvard Medical School set out to determine whether higher long term intake of baked, boiled, or mashed potatoes, French fries, and potato chips (crisps) was associated with incident hypertension.
They followed over 187,000 men and women from three large US studies for more than 20 years. Dietary intake, including frequency of potato consumption, was assessed using a questionnaire. Hypertension was reported by participants based on diagnosis by a health professional.
After taking account of several other risk factors for hypertension, the researchers found that four or more servings a week of baked, boiled, or mashed potatoes was associated with an increased risk of hypertension compared with less than one serving a month in women, but not in men.
Higher consumption of French fries was also associated with an increased risk of hypertension in both women and men. However, consumption of potato chips (crisps) was associated with no increased risk.
After further analyses, the researchers suggest that replacing one serving a day of boiled, baked, or mashed potatoes with one serving of a non-starchy vegetable is associated with a decreased risk of hypertension.
The authors point out that potatoes have a high glycaemic index compared with other vegetables, so can trigger a sharp rise in blood sugar levels, and this could be one explanation for the findings.
They also acknowledge some study limitations and say that, as with any observational study, no firm conclusions can be drawn about cause and effect.
Nevertheless, they say their findings "have potentially important public health ramifications, as they do not support a potential benefit from the inclusion of potatoes as vegetables in government food programs but instead support a harmful effect that is consistent with adverse effects of high carbohydrate intakes seen in controlled feeding studies."
In a linked editorial, researchers at the University of New South Wales argue that, although diet has an important part to play in prevention and early management of hypertension, dietary behaviour and patterns of consumption are complex and difficult to measure.
"We will continue to rely on prospective cohort studies, but those that examine associations between various dietary patterns and risk of disease provide more useful insights for both policy makers and practitioners than does a focus on individual foods or nutrients," they conclude.
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Tuesday, 10 May 2016
Skywatchers across the globe are observing Mercury transit the Sun, the little planet's third such pass of 14 it will make this century.
Mercury's sojourn between Earth and our star lasts from 11:12 until 18:42 GMT.
It will not make another transit until 2019 and then 2032.
The event is impossible - and dangerous - to view with the naked eye or binoculars, but astronomy groups worldwide are offering the chance view it through filtered telescopes.
Live views from space and ground telescopes are also available online.
They show Mercury as a tiny black circle, smaller but darker than many sunspots, slowly traversing the Sun's giant yellow disc.
Mercury spins around the Sun every 88 days, but its orbit is tilted relative to the Earth's. It is that discrepancy which makes it relatively rare for the three bodies to line up in space.
From western Europe, north-western Africa and much of the Americas, Mercury's seven-and-a-half-hour glide across the Sun will be visible in its entirety. A further swathe of the planet will catch part of the transit, depending on local sunrise and sunset times.
The only land masses to miss out completely are Australasia, far eastern Asia and Antarctica.
Because Mercury is so small - just one-third as big as Earth and, from our perspective, 1/150th of the Sun's diameter - its transit can only be glimpsed under serious magnification; the "eclipse glasses" used by thousands of people to view last year's solar eclipse will be useless.
And to avoid permanent eye damage, any telescope must be fitted with a solar filter before being trained on the Sun. The British Astronomical Association explains on its website how amateur stargazers can enjoy the spectacle safely.
Open University's Prof David Rothery said the celestial event would not present any novel scientific opportunities - but was special nonetheless.
"From this transit, we're unlikely to learn anything we don't already know," he told BBC Inside Science. "But what a wonderful event for showing people Mercury. It's a hard planet to see.
"Historically, transits were of immense importance."
In the 1700s, for example, it was observations of Mercury and Venus slipping across the Sun that allowed astronomers, led by Edmund Halley, to pin down the dimensions of the known Solar System.
Prof Rothery is a Mercury expert and a leading scientist on the European Space Agency's BepiColombo mission to the diminutive planet, which will launch in 2017 or 2018.
Mercury has already been visited by two Nasa probes: Mariner 10 flew past in 1974 and 1975 and Messenger spent four years in orbit until its planned crash landing in 2015.
Messenger spent four years in orbit taking images and measurements of Mercury
"[Messenger] told us an awful lot. It really told us we don't understand Mercury - because there's a lot of things which just don't stack up," Prof Rothery said.
"It's an airless body, with lots of craters... But there's been a long history of volcanic activity, fault activity - and the composition, that began to be revealed by Messenger, is weird.
"There's very little iron at the surface but it must have a ginormous iron core, because it generates a magnetic field - which Venus, Mars and the Moon don't."
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Tuesday, 3 May 2016
Livestock farming is responsible for 18 percent of the world's greenhouse gases, and ruminants such as cattle, sheep and goats generate 35 percent of one of these gases - methane, and according to experts they make a significant contribution to climate change.
Researchers at the Spanish National Research Council (CSIC) have taken part in a study of the effect of one molecule, 3-nitrooxypropanol, in inhibiting methane production in ruminants. The work has been published in the magazine, Proceedings of the National Academy of Sciences (PNAS).
|Stereo, skeletal formula of methane with some measurements added. By Jynto [Public domain], via Wikimedia Commons.|
Ruminants are animals which digest their food through fermentation carried out by microorganisms living in the rumen. This process produces organic acids: acetic acid, propionic acid, and butyric acid, all of which are absorbed and metabolized by the organism as a source of energy. But, in addition, it also produces methane, which escapes into the atmosphere in the form of gas.
How 3-nitrooxypropanol works
By 2014, scientists had demonstrated the effectiveness of this molecule in sheep, but were unaware of how it actually worked. Now, in vivo research, using incubated anaerobic microorganisms from ruminants' digestive systems have revealed how the compound 3-nitrooxypropanol only had an effect on methane producing microorganisms (arqueas methanogens) and not on those which contribute to digestion (bacterias). As David Yáñez, a CSIC researcher at the Zaidin Experimental Research Centre in Granada (southern Spain) explains, "Up until now, no-one had described the mode of action of a compound which can repeatedly reduce (by 30%) methane production in animals without any risks, either to the animal's health, or to their productivity."
The results of this work open up the possibility of reducing methane emissions and of contributing to a reduction in global temperatures which is caused by greenhouse gases. In addition, "We will see an increase in the efficiency of ruminant production systems as better use is made of the energy taken in in animal feed, given that methane production accounts for a loss of up to 12% of the energy an animal ingests" notes Yáñez.
Both the University of Auburn in the USA and the Max Planck Institute in Germany collaborated on this project as did the Swiss company, DSM Nutritional Products, which developed and owns the patent to 3-nitrooxypropanol.
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Tuesday, 26 April 2016
In 1986, in Pripet, Russia, one of the four reactors at the Chernobyl nuclear plant exploded in the world's worst civil nuclear catastrophe. It sent a cloud of radioactive dust over Europe.
The disaster began during a systems test on 26 April 1986 at reactor number four of the Chernobyl plant. There was a sudden and unexpected power surge, and when an emergency shutdown was attempted, an exponentially larger spike in power output occurred, which led to a reactor vessel rupture and a series of steam explosions. These events exposed the graphite moderator of the reactor to air, causing it to ignite. The resulting fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area, including Pripyat. The plume drifted over large parts of the western Soviet Union and Europe. From 1986 to 2000, 350,400 people were evacuated and resettled from the most severely contaminated areas of Belarus, Russia, and Ukraine. According to official post-Soviet data, about 60% of the fallout landed in Belarus.
|The abandoned city of Pripyat with Chernobyl plant in the distance, by Jason Minshull [Public domain], via Wikimedia Commons|
Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and health care costs of the Chernobyl accident. A report by the International Atomic Energy Agency examines the environmental consequences of the accident. Another UN agency, UNSCEAR, has estimated a global collective dose of radiation exposure from the accident "equivalent on average to 21 additional days of world exposure to natural background radiation"; individual doses were far higher than the global mean among those most exposed, including 530,000 local recovery workers who averaged an effective dose equivalent to an extra 50 years of typical natural background radiation exposure each. Estimates of the number of deaths that will eventually result from the accident vary enormously; disparities reflect both the lack of solid scientific data and the different methodologies used to quantify mortality—whether the discussion is confined to specific geographical areas or extends worldwide, and whether the deaths are immediate, short term, or long term.
Thirty-one deaths are directly attributed to the accident, all among the reactor staff and emergency workers. An UNSCEAR report places the total confirmed deaths from radiation at 64 as of 2008. The Chernobyl Forum predicts the eventual death toll could reach 4,000 among those exposed to the highest levels of radiation (200,000 emergency workers, 116,000 evacuees and 270,000 residents of the most contaminated areas); this figure is a total causal death toll prediction, combining the deaths of approximately 50 emergency workers who died soon after the accident from acute radiation syndrome, nine children who have died of thyroid cancer and a future predicted total of 3940 deaths from radiation-induced cancer and leukemia.
In a peer-reviewed publication in the International Journal of Cancer in 2006, the authors (following a different conclusion methodology to the Chernobyl Forum study, which arrived at the total predicted death toll of 4,000 after cancer survival rates were factored in) stated, without entering into a discussion on deaths, that in terms of total excess cancers attributed to the accident:
The risk projections suggest that by now Chernobyl may have caused about 1000 cases of thyroid cancer and 4000 cases of other cancers in Europe, representing about 0.01% of all incident cancers since the accident. Models predict that by 2065 about 16,000 cases of thyroid cancer and 25,000 cases of other cancers may be expected due to radiation from the accident, whereas several hundred million cancer cases are expected from other causes.
Also based upon extrapolations from the linear no-threshold model of radiation induced damage, down to zero, the Union of Concerned Scientists estimates that, among the hundreds of millions of people living in broader geographical areas, there will be 50,000 excess cancer cases resulting in 25,000 excess cancer deaths.
For this broader group, the 2006 TORCH report, commissioned by the European Greens political party, predicts 30,000 to 60,000 excess cancer deaths. The environmental advocacy group Greenpeace reports the figure at 200,000 or more.
The Russian founder of that region's chapter of Greenpeace also authored a book titled Chernobyl: Consequences of the Catastrophe for People and the Environment, which concludes that among the billions of people worldwide who were exposed to radioactive contamination from the disaster, nearly a million premature cancer deaths occurred between 1986 and 2004. The book, however, has failed the peer review process. Of the five reviews published in the academic press, four considered the book severely flawed and contradictory, and one praised it while noting some shortcomings. The review by M. I. Balonov published by the New York Academy of Sciences concludes that the report is of negative value because it has very little scientific merit while being highly misleading to the lay reader. It characterized the estimate of nearly a million deaths as more in the realm of science fiction than science.
The accident raised concerns about nuclear power worldwide and slowed or reversed the expansion of nuclear power stations. The accident also raised concerns about the safety of the Soviet nuclear power industry, slowing its expansion for a number of years and forcing the Soviet government to become less secretive about its procedures. The government coverup of the Chernobyl disaster was a "catalyst" for glasnost, which "paved the way for reforms leading to the Soviet collapse".
The final shutdown of the undamaged last reactor on the site took place ceremoniously on 15 Dec 2000.
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Tuesday, 19 April 2016
An unexpected discovery has led to a rechargeable battery that's as inexpensive as conventional car batteries, but has a much higher energy density. The new battery could become a cost-effective, environmentally friendly alternative for storing renewable energy and supporting the power grid.
A team based at the Department of Energy's Pacific Northwest National Laboratory identified this energy storage gem after realizing the new battery works in a different way than they had assumed.
The journal Nature Energy published a paper today that describes the battery.
"The idea of a rechargeable zinc-manganese battery isn't new; researchers have been studying them as an inexpensive, safe alternative to lithium-ion batteries since the late 1990s," said PNNL Laboratory Fellow Jun Liu, the paper's corresponding author. "But these batteries usually stop working after just a few charges. Our research suggests these failures could have occurred because we failed to control chemical equilibrium in rechargeable zinc-manganese energy storage systems."
|A range of different batteries|
After years of focusing on rechargeable lithium-ion batteries, researchers are used to thinking about the back-and-forth shuttle of lithium ions. Lithium-ion batteries store and release energy through a process called intercalation, which involves lithium ions entering and exiting microscopic spaces in between the atoms of a battery's two electrodes.
This concept is so engrained in energy storage research that when PNNL scientists, collaborating with the University of Washington, started considering a low-cost, safe alternative to lithium-ion batteries - a rechargeable zinc-manganese oxide battery - they assumed zinc would similarly move in and out of that battery's electrodes.
After a battery of tests, the team was surprised to realize their device was undergoing an entirely different process. Instead of simply moving the zinc ions around, their zinc-manganese oxide battery was undergoing a reversible chemical reaction that converted its active materials into entirely new ones.
Liu and his colleagues started investigating rechargeable zinc-manganese batteries because they are attractive on paper. They can be as inexpensive as the lead-acid batteries because they use abundant, inexpensive materials (zinc and manganese). And the battery's energy density can exceed lead-acid batteries. The PNNL scientists hoped they could produce a better-performing battery by digging deeper into the inner workings of the zinc-manganese oxide battery.
So they built their own battery with a negative zinc electrode, a positive manganese dioxide electrode and a water-based electrolyte in between the two. They put small, button-sized test batteries through the wringer, repeatedly charging and discharging them. As others had found before them, their test battery quickly lost its ability to store energy after just a few charging cycles. But why?
To find out, they first performed a detailed chemical and structural analysis of the electrolyte and electrode materials. They were surprised to not find evidence of zinc interacting with manganese oxide during the battery's charge and discharge processes, as they had initially expected would happen. The unexpected finding led them to wonder if the battery didn't undergo a simple intercalation process as they had previously thought. Perhaps the zinc-manganese battery is less like a lithium-ion battery and more like the traditional lead-acid battery, which also relies on chemical conversion reactions.
To dig deeper, they examined the electrodes with several advanced instruments with a variety of scientific techniques, including Transmission Electron Microscopy, Nuclear Magnetic Resonance and X-Ray Diffraction. The instruments used were located at both PNNL and the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science user facility located at PNNL.
Combining these techniques revealed manganese oxide was reversibly reacting with protons from the water-based electrolyte, which created a new material, zinc hydroxyl sulfate.
Typically, zinc-manganese oxide batteries significantly lose storage capacity after just a few cycles. This happens because manganese from the battery's positive electrode begins to sluff off, making the battery's active material inaccessible for energy storage. But after some manganese dissolves into the electrolyte, the battery gradually stabilizes and the storage capacity levels out, though at a much lower level.
The team used the new knowledge to prevent this manganese sluff-off. Knowing the battery underwent chemical conversions, they determined the rate of manganese dissolution could be slowed down by increasing the electrolyte's initial manganese concentration.
So they added manganese ions to the electrolyte in a new test battery and put the revised battery through another round of tests. This time around, the test battery was able to reach a storage capacity of285 milliAmpere-hours per gram of manganese oxide over 5,000 cycles, while retaining 92 percent of its initial storage capacity.
"This research shows equilibrium needs to be controlled during a chemical conversion reaction to improve zinc-manganese oxide battery performance," Liu said. "As a result, zinc-manganese oxide batteries could be a more viable solution for large-scale energy storage than the lithium-ion and lead-acid batteries used to support the grid today."
The team will continue their studies of the zinc-manganese oxide battery's fundamental operations. Now that they've learned the products of the battery's chemical conversion reactions, they will move on to identify the various in-between steps to create those products. They will also tinker with the battery's electrolyte to see how additional changes affect its operation.
This research was supported by DOE's Office of Science and used resources at the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science user facility located at PNNL.
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Tuesday, 12 April 2016
An international team of scientists has found evidence of a series of massive supernova explosions near our solar system, which showered Earth with radioactive debris.
The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.
The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).
"We were very surprised that there was debris clearly spread across 1.5 million years," said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. "It suggests there were a series of supernovae, one after another.
"It's an interesting coincidence that they correspond with when the Earth cooled and moved from the Pliocene into the Pleistocene period."
|A supernova. NASA/ESA [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons|
The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.
Some theories suggest cosmic rays from the supernovae could have increased cloud cover.
A supernova is a massive explosion of a star as it runs out of fuel and collapses.
The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.
Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.
The supernova explosions create many heavy elements and radioactive isotopes which are strewn into the cosmic neighbourhood.
One of these isotopes is iron-60 which decays with a half-life of 2.6 million years, unlike its stable cousin iron-56. Any iron-60 dating from Earth's formation more than four billion years ago has long since disappeared.
The iron-60 atoms reached Earth in minuscule quantities and so the team needed extremely sensitive techniques to identify the interstellar iron atoms.
"Iron-60 from space is a million-billion times less abundant than the iron that exists naturally on Earth," said Dr Wallner.
Dr Wallner was intrigued by first hints of iron-60 in samples from the Pacific Ocean floor, found a decade ago by a group at TU Munich.
He assembled an international team to search for interstellar dust from 120 ocean-floor samples spanning the past 11 million years.
The first step was to extract all the iron from the ocean cores. This time-consuming task was performed by two groups, at HZDR and the University of Tokyo.
The team then separated the tiny traces of interstellar iron-60 from the other terrestrial isotopes using the Heavy-Ion Accelerator at ANU and found it occurred all over the globe.
The age of the cores was determined from the decay of other radioactive isotopes, beryllium-10 and aluminium-26, using accelerator mass spectrometry (AMS) facilities at DREsden AMS (DREAMS) of HZDR, Micro Analysis Laboratory (MALT) at the University of Tokyo and the Vienna Environmental Research Accelerator (VERA) at the University of Vienna.
The dating showed the fallout had only occurred in two time periods, 3.2 to 1.7 million years ago and eight million years ago. Current results from TU Munich are in line with these findings.
A possible source of the supernovae is an aging star cluster, which has since moved away from Earth, independent work led by TU Berlin has proposed in a parallel publication. The cluster has no large stars left, suggesting they have already exploded as supernovae, throwing out waves of debris.
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