Astronomy
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NASA's Opportunity Rover Will Explore A Gully On Mars
NASA’s Opportunity Mars rover will do what no other rover has done before: drive down a gully created by a fluid that could have been water.
The rover will also visit the interior of the Endeavour Crater as a part of a two-year extended mission.
Opportunity was launched in July of 2003 for a mission that was to last 90 Martian days, or 92.4 Earth days. It landed on Mars in January of 2004.
Opportunity’s latest extended mission was in the “Bitterroot Valley,” a portion on the western rim of the Endeavour Crater. After seven years investigating, the rover finally reached the edge of the crater in 2011 and had discovered evidence of acidic ancient water.
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"Fluid-carved gullies on Mars have been seen from orbit since the 1970s, but none had been examined up close on the surface before,” [Opportunity Principal Investigator Steve Squyres of Cornell University, Ithaca, New York] said in the press release. “One of the three main objectives of our new mission extension is to investigate this gully. We hope to learn whether the fluid was a debris flow, with lots of rubble lubricated by water, or a flow with mostly water and less other material."
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We Land On Mars In Just 4 days!
Cross your fingers for good weather on the Red Planet on October 19. That’s the day the European Space Agency’s Schiaparelli lander pops open its parachute, fires nine, liquid-fueled thrusters and descends to the surface of Mars. Assuming fair weather, the lander should settle down safely on the wide-open plains of Meridiani Planum near the Martian equator northwest of NASA’s Opportunity rover. The region is rich in hematite, an iron-rich mineral associated with hot springs here on Earth.
The 8-foot-wide probe will be released three days earlier from the Trace Gas Orbiter (TGO) and coast toward Mars before entering its atmosphere at 13,000 mph (21,000 km/hr). During the 6-minute-long descent, Schiaparelli will decelerate gradually using the atmosphere to brake its speed, a technique called aerobraking. Not only is Meridiani Planum flat, it’s low, which means the atmosphere is thick enough to allow Schiaparelli’s heat shield to reduce its speed sufficiently so the chute can be safely deployed. The final firing of its thrusters will ensure a soft and controlled landing.
The lander is one-half of the ExoMars 2016 mission, a joint venture between the European Space Agency and Russia’s Roscosmos. The Trace Gas Orbiter (TGO) will fire its thrusters to place itself in orbit about the Red Planet the same day Schiparelli lands. Its job is to inventory the atmosphere in search of organic molecules, methane in particular. Plumes of methane, which may be biological or geological (or both) in origin, have recently been detected at several locations on Mars including Syrtis Major, the planet’s most prominent dark marking. The orbiter will hopefully pinpoint the source(s) as well as study seasonal changes in locations and concentrations.
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While TGO’s mission will require years, the lander is expected to survive for only four Martian days (called ‘sols’) by using the excess energy capacity of its batteries. A set of scientific sensors will measure wind speed and direction, humidity, pressure and electric fields on the surface. A descent camera will take pictures of the landing site on the way down; we’ll should see those photos the very next day. Data and imagery from the lander will be transmitted to ESA’s Mars Express and a NASA Relay Orbiter, then relayed to Earth.
If you’re wondering why the lander’s mission is so brief, it’s because Schiaparelli is essentially a test vehicle. Its primary purpose is to test technologies for landing on Mars including the special materials used for protection against the heat of entry, a parachute system, a Doppler radar device for measuring altitude and liquid-fueled braking thrusters.
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Biology
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Why Naked Mole Rats Feel No Pain
The African naked mole rat is an odd, homely creature with the closest thing to real-life super powers on earth. These small rodents can live for 32 years, they are cancer-resistant, and they are impervious to some types of pain.
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Imagine the sting of entering a hot tub with a bad sunburn. The naked mole rat wouldn't be bothered, but most animals would sense this as thermal hyperalgesia, and the scientists who conducted the study have a good idea of what goes on at a cellular level when this happens.
In response to high temperatures and inflammation around sensory neurons, nerve growth factor (NGF) molecules bind to a receptor called TrkA. This kicks off a cascade of chemical signals that "sensitize" an ion channel -- called TRPV1 -- on the surface of the sensory neuron so that it opens. Once TRPV1 opens, it results in sensory nerve firing that tells the brain to register pain at temperatures that are not normally painful.
Through more than a dozen carefully designed experiments, Lewin and colleagues found what differentiates the naked mole rat from other animals in this process -- a small change in their TrkA receptor.
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However, the new study found that naked mole rats are born with roughly the same number of pain sensors as newborn mice. It's only by adulthood that the naked mole rat's pain sensors dwindle by two-thirds compared to any other mammal. Evolution may have selected a TrkA receptor that works well enough for the animal developing as an embryo, but leaves adults with fewer nerve receptors and partially pain-free.
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Animal Hybrids May Hold Clues To Neandertal-Human Interbreeding
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Thanks to ancient hookups, between 20 and 35 percent of Neandertals’ genes live on in various combinations from one person to another. About 1.5 to 4 percent of DNA in modern-day non-Africans’ genomes comes from Neandertals, a population that died out around 40,000 years ago.
Even more surprising, H. sapiens’ Stone Age dalliances outside their own kind weren’t limited to Neandertals. Ancient DNA shows signs of interbreeding between now-extinct Neandertal relatives known as Denisovans and ancient humans. Denisovans’ DNA legacy still runs through native populations in Asia and the Oceanic islands. [...] Genetic clues also suggest that Denisovans mated with European Neandertals.
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Streaming evolution
Interbreeding is no rare event. Genome comparisons have uncovered unexpectedly high levels of hybridization among related species of fungi, plants, rodents, birds, bears and baboons, to name a few. Species often don’t fit the traditional concept of populations that exist in a reproductive vacuum, where mating happens only between card-carrying species members.
Evolutionary biologists increasingly view species that have diverged from a common ancestor within the last few million years as being biologically alike enough to interbreed successfully and evolve as interconnected populations. These cross-species collaborations break from the metaphor of an evolutionary tree sprouting species on separate branches. Think instead of a braided stream, with related species flowing into and out of genetic exchanges, while still retaining their own distinctive looks and behaviors.
Research now suggests that hybridization sometimes ignites helpful evolutionary changes. An initial round of interbreeding — followed by hybrid offspring mating among themselves and with members of parent species — can result in animals with a far greater array of physical traits than observed in either original species. Physical variety in a population provides fuel for natural selection, the process by which individuals with genetic traits best suited to their environment tend to survive longer and produce more offspring.
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Chemistry
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Secret Of Frankincense’s Evocative Smell Unravelled
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Although frankincense has been used for thousands of years, the exact identity of the compounds that give it its distinctive smell remained a mystery. Because classic techniques like thin layer chromatography, GC–MS or even HPLC were not sensitive enough to identify all of frankincense’s many odorants, the team led by Nicolas Baldovini at the University of Nice Sophie Antipolis in France, used chromatography–olfactometry. This system splits the output of a gas chromatograph into two different lines: a classic mass spectrometry detector, and a sniffing port, where a researcher can smell and hopefully identify the aroma of every peak. For scientists working in this area, the human nose remains a valuable tool and can be more sensitive to certain smells than lab instruments.
Chemists identified two unknown peaks with a smell that was highly characteristic of frankincense in the acidic fraction of the extract, which represents just 0.2% of the oil. ‘Although it was quite difficult, it was also very hopeful to find an odour zone that had never been identified before,’ says Baldovini. Because these molecules were present in trace amounts, researchers had to refine 3kg of essential oil to obtain just 1mg of them. The team then synthesised the four isomers of 2-octylcyclopropanecarboxylic acid, also known as olibanic acid, to prove that they had correctly identified the two molecules responsible for frankincense’s distinctive smell. ‘These molecules are not commercially available in enantiopure forms, so we had to make them in the lab. We had no other choice,’ adds Baldovini.
Baldovini says that molecules previously linked to frankincense’s smell ‘lack the characteristic, church like smell; actually most of them are odourless’. The only antecedent of a compound with a true olibanum note was a very similar molecule called cis isocascarillic acid isolated from oranges. ‘This molecule probably fits the same olfactory receptor, but nothing like it had ever been isolated from frankincense,’ said Baldovini.
Johannes Niebler, a researcher who has investigated the odour of frankincense at Friedrich–Alexander University, Erlangen–Nuremberg in Germany, remarks that ‘we had unravelled two other highly potent odorants contributing to the smell of Boswellia sacra frankincense, but the main “key” was still missing. This publication closes a big gap in the research on frankincense odorants.’ Niebler is also surprised by the structure of olibanic acids: ‘A ring of three carbons embedded in a fatty acid is quite rare in nature. It seems these compounds may only be found in the botanic genus of frankincense.’
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Mercury From WWII Submarine Wreck Pollutes Sediments Off Norway
The German submarine U-864 was sunk in World War II off the Norwegian island of Fedje, loaded with 67 tons of metallic mercury. When the wreck was discovered in 2003, some of the mercury was found leaking from broken containers. Now, researchers show that this material has contaminated sediments surrounding the wreck. But surprisingly, the scientists think the marine food web may not be substantially affected by the pollution, based on their analysis of crabs sampled near the sub [...].
Crabs and other seafood are often contaminated with neurotoxic mercury from industrial pollution and fossil fuel burning that is deposited from the air onto the ocean surface, making its way into the food chain. So when the mercury-laden vessel was discovered at a relatively shallow depth of 150 m, scientists, fishermen, and government officials were concerned. To determine the wreck’s impact, Norway’s Coastal Administration sampled sediments, and the National Institute of Nutrition & Seafood Research collected crabs near the site. Frank Vanhaecke of Ghent University and his colleagues then analyzed the samples with a variety of methods, including measuring mercury isotope ratios using multicollector inductively coupled plasma-mass spectrometry.
“In some sediment samples we could see small droplets of mercury,” Vanhaecke says. The wet sediments had 60 to 24,000 mg/kg of mercury—in comparison, background levels in ocean sediments are 0.02 to 0.1 mg/kg. The isotopic composition of mercury in the submarine was similar to that in the sediments. Notably, crabs collected within a four-nautical-mile radius of the wreck did not have significantly different mercury concentrations than those collected from other areas along the Norwegian coast. However, the isotopic results indicate that crabs in the immediate vicinity of the submarine did take on some mercury from the wreck in their brown meat.
The researchers hypothesize that mercury levels in crabs are not elevated because the sandy seafloor has relatively little organic matter; this may have limited methylation of mercury from the wreck by microbes. Methylmercury is the most bioavailable and toxic form of the element. Instead of methylmercury, what little mercury the crabs absorbed from the wreck was likely ingested directly from the sediments. The results show no evidence that the metal transforms into the more toxic methylmercury, Vanhaecke says. That “would make the problem much more risky,” he says, and needs to be further assessed.
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Ecology
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Salty Snow Could Affect Air Pollution In The Arctic
In pictures, the Arctic appears pristine and timeless with its barren lands and icy landscape. In reality, the area is rapidly changing. Scientists are working to understand the chemistry behind these changes to better predict what could happen to the region in the future. [...]
The Arctic’s wintertime ice hit a record low this year, and its air is warming, according to NASA. Previous research has shown that pollutants, including gaseous nitrogen oxides and ozone, have at times been recorded at levels similar to those one would see in more populated areas. Nitrogen oxides are air pollutants that, in sunlight, lead to the formation of ozone, the main component in smog normally associated with cities. The gases can be processed in the atmosphere and be deposited on Earth as nitrates, which can get trapped in snow. In sunlight, snow can act as a reactor in which nitrates may be transformed back to nitrogen oxide gases. In the Arctic, sea ice and snow contain salt and other impurities that can possibly alter the efficiency of this process. James Donaldson, Karen Morenz and colleagues took a closer look at how salt and nitrate content in snow could affect the levels of nitrogen oxides in the air during sunny conditions.
The researchers tested lab-made snow containing nitrate alone or nitrate and salt. They found that under simulated sunlight, about 40 to 90 percent more nitrogen dioxide (NO2) was reformed from the snow with low levels of salt at environmentally relevant concentrations than snow with no salt. Researchers observed the greatest effect when they used realistic sea salt in the experiment. The results suggest that sea ice and salty snow, which previously have not been considered as factors in the balance of ozone-forming chemicals in the atmosphere, should be a part of future models.
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Physics
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Theory Redraws Formation Of Early Universe
Scientists have provided a solid foundation for an alternative theory to help explain how the early universe took shape.
This theory, first devised two decades ago, proposes that the dominant expansion in the early universe some 14 billion years ago, known as cosmological inflation, took place in a warm environment.
The idea differs from existing theories which state that this time of change took place during a cold period.
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Alternative theory
The latest research, published in Physical Review Letters, contradicts an alternative theory known as standard inflation theory, which suggests that early expansion of the universe took place in a cold phase. In that theory, as the universe took shape, the temperature plummeted before getting reheated again. Their paper was highlighted by the journal as an Editors' Suggestion, which recognises its important contribution to the field.
"We are pleased to have formed a theoretical model for this phase of the universe, which is based on first principles. This could be a valuable theory for improving our understanding of how the early universe took shape," says Professor Arjun Berera of the School of Physics and Astronomy.
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