Astronomy
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How Bad Is The Radiation On Mars?
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Causes:
Mars has no protective magnetosphere, as Earth does. Scientists believe that at one time, Mars also experienced convection currents in its core, creating a dynamo effect that powered a planetary magnetic field. However, roughly 4.2 billions year ago – either due to a massive impact from a large object, or rapid cooling in its core – this dynamo effect ceased.
As a result, over the course of the next 500 million years, Mars atmosphere was slowly stripped away by solar wind. Between the loss of its magnetic field and its atmosphere, the surface of Mars is exposed to much higher levels of radiation than Earth. And in addition to regular exposure to cosmic rays and solar wind, it receives occasional lethal blasts that occur with strong solar flares.
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Possible Solutions:
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Proposals have also been made to build habitats above-ground using inflatable modules encased in ceramics created using Martian soil. Similar to what has been proposed by both NASA and the ESA for a settlement on the Moon, this plan would rely heavily on robots using 3D printing technique known as “sintering“, where sand is turned into a molten material using x-rays.
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But perhaps the most radical proposal for reducing Mars’ exposure to harmful radiation involves jump-starting the planet’s core to restore its magnetosphere. To do this, we would need to liquefy the planet’s outer core so that it can convect around the inner core once again. The planet’s own rotation would begin to create a dynamo effect, and a magnetic field would be generated.
According to Sam Factor, a graduate student with the Department of Astronomy at the University of Texas, there are two ways to do this. The first would be to detonate a series of thermonuclear warheads near the planet’s core, while the second involves running an electric current through the planet, producing resistance at the core which would heat it up.
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Huge Underground Ice Deposit On Mars Is Bigger Than New Mexico
A giant deposit of buried ice on Mars contains about as much water as Lake Superior does here on Earth, a new study reports.
The ice layer, which spans a greater area than the state of New Mexico, lies in Mars' mid-northern latitudes and is covered by just 3 feet to 33 feet (1 to 10 meters) of soil. It therefore represents a vast possible resource for future astronauts exploring the Red Planet, study team members said.
"This deposit is probably more accessible than most water ice on Mars, because it is at a relatively low latitude and it lies in a flat, smooth area where landing a spacecraft would be easier than at some of the other areas with buried ice," co-author Jack Holt, of the University of Texas, Austin, said in a statement.
[Photos: The Search for Water on Mars]
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Indeed, the ice deposit probably formed during a high-tilt era, when snow accumulated at middle Martian latitudes rather than at the poles as it does now, Stuurman said. So further study of the Utopia Planitia ice deposit could also shed light on how the Martian climate has changed over the ages.
"The ice deposits in Utopia Planitia aren't just an exploration resource, they're also one of the most accessible climate change records on Mars," co-author Joe Levy, also of the University of Texas, said in the same statement.
"We don't understand fully why ice has built up in some areas of the Martian surface and not in others," Levy added. "Sampling and using this ice with a future mission could help keep astronauts alive, while also helping them unlock the secrets of Martian ice ages."
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Biology
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World Of Viruses Uncovered
A groundbreaking study of the virosphere of the most populous animals -- those without backbones such as insects, spiders and worms and that live around our houses -- has uncovered 1445 viruses, revealing people have only scratched the surface of the world of viruses -- but it is likely that only a few cause disease.
The meta-genomics research, a collaboration between the University of Sydney and the Chinese Centre for Disease Control and Prevention in Beijing, was made possible by new technology that also provides a powerful new way to determine what pathogens cause human diseases.
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"It's remarkable that invertebrates like insects carry so very many viruses -- no one had thought to look before because most of them had not been associated with human-borne illnesses." [Professor Edward Holmes, from the Marie Bashir Institute for Infectious Diseases & Biosecurity and the School of Life and Environmental Sciences]
Although insects such mosquitoes are well-known for their potential to transmit viruses like zika and dengue, Professor Holmes stressed that insects should not generally be feared because most viruses were not transferable to humans and invertebrates played an important role in the ecosystem.
Importantly, the same techniques used to discover these invertebrate viruses could also be used to determine the cause of novel human diseases, such as the controversial 'Lyme-like disease' that is claimed to occur following tick bites.
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Bacteria Help Carnivorous Plants Drown Their Prey
Bacteria may be a meat-eating plant’s best friends thanks to their power to reduce the surface tension of water.
The carnivorous pitcher plant Darlingtonia californica releases water into the tall vases of its leaves, creating deathtraps where insect prey drown. Water in a pitcher leaf starts clear. But after about a week, thanks to bacteria, it turns “murky brown to a dark red and smells horrible,” says David Armitage of the University of Notre Dame in Indiana. Now, he’s found that those bacteria can help plants keep insects trapped. Microbial residents reduce the surface tension of water enough for ants and other small insects to slip immediately into the pool instead of perching lightly on the surface, he reports November 23 in Biology Letters.
Armitage seeded tubes of clean water with fluid from the trap pools of pitcher plants and added dead crickets to feed the microbes. After sitting for a month, the mess had about the same surface tension properties as natural pitcher plant pools. Then, he created a series of increasingly dilute samples of pool soup and dropped harvester ants into each one. He found that the ants sank immediately in all but the bacteria-free water sample.
Bacterial populations in a pitcher leaf are akin to those in a mammal gut or bovine rumen, Armitage’s preliminary analysis finds. The microbes can help digest the prey as well as catch it, he says.
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Chemistry
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Clever Computers Find Solutions To NaOH Structural Puzzle
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Sodium hydroxide is one of the most commonly used chemical reagents; yet until now researchers have not fully explored the structural properties of its aqueous solutions. NaOH can be found in any laboratory and concentrated solutions of this strong base are frequently used in chemical industry for example in paper production. As such, there is significant interest in determining its fundamental properties.
Jörg Behler and Matti Hellström at Ruhr University Bochum, have now discovered that there’s more to this deceptively simple and common reagent. The compound shows a broad distribution of possible three-dimensional arrangements of its ions and the surrounding water molecules (called coordination polyhedra) that vary with concentration. The arrangement of these polyhedra with respect to each other is equally complex.
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They discovered a total of 12 distinct coordination polyhedra. In a fully saturated solution, there are only two water molecules per formula unit NaOH. At these high concentrations, each coordination polyhedron prefers to share ligands with different types of polyhedra leading to complex structural patterns. Until now such research has been hindered by this extraordinary complexity as predicting these structures through traditional methods can be very computationally intensive.
Behler and Hellström used a method based on artificial neural networks. ‘We ended up using [this method] because it is both very accurate and less computationally demanding than quantum-chemical “first-principles” methods,’ reflects Hellström.
Artificial neural networks mimic the way the brain works. Rather than programming the entire simulation from scratch, Behler and Hellström feed the program training examples based on neutron and x-ray diffraction data. The neural network takes these examples and uses them to learn how to solve the problem by itself. ‘This is a remarkably thorough and complete application of the impressive methodology,’ says Paul Popelier, an expert in chemical theory and computation at the University of Manchester, UK. ’It offers a computationally attractive and more feasible alternative to ab initio molecular dynamics to obtain insight in the microstructure of solutes, independently of experiment.’
-Editors Note: The band scheduled for this week, Coordination Polyhedra, will not be available due to the absence of one of its members, Flap Pyramid, whose present whereabouts remains uncertain. An artist’s rendering of Flap Pyramid's current theoretical appearance, as well as those of the rest of the band, is contained at the link.-
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What Will It Take To Find A Human Pheromone?
In 1991, at a conference sponsored by a fragrance company called Erox Corp., two University of Utah scientists presented research on a tantalizing pair of chemical compounds provided by the company. They reported that in a few dozen human volunteers, the molecules androstadienone and estratetraenol activated the vomeronasal organ (VNO)—an olfactory organ that senses pheromones in many animals—in a sex-specific manner. The company patented these molecules as putative human pheromones.
About 10 years later, University of Chicago biopsychologist Martha K. McClintock and a colleague tested the molecules’ ability to affect the emotional states of men and women. The results, when published in 2000, did not support Erox’s claim: “It is premature to call these steroids human pheromones,” the authors concluded [...]. Still, the paper brought the compounds to the attention of the scientific community.
The human body naturally produces androstadienone and estratetraenol, but the compounds’ activity as pheromones—substances produced and emitted by one individual of a species as signals affecting the behavior or physiology of another individual of the same species—has never been rigorously demonstrated. Most researchers today also agree that the VNO in humans, located just behind the nasal septum, is vestigial, an organ that’s no longer of use to today’s Homo sapiens.
[Tristram Wyatt, a zoologist at the University of Oxford] and other researchers have long tried to address a thorny question: Do human pheromones actually exist? Despite more than half a century of vigorous debate on the topic, there’s still no answer in sight. Indirect evidence suggests they might. For Wyatt, one strong indicator is that humans develop a permanently strong body odor during puberty; it’s at least possible that such odors act as chemical signals, as they do in some other sexually mature mammals at breeding times. The fact that other mammals have pheromones suggests that we may, too. Knowing either way would shed light on this primal and poorly understood communication system.
To date, though, no actual molecules that serve as human pheromones have ever been identified—in part because molecules falsely called pheromones diverted the search, but also because identifying the molecular basis of human behaviors is exceedingly complicated. A close look at the history of research on pheromones in other mammals reveals some of the challenges in the search and why settling the question will be no easy matter.
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Ecology
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102 Million Trees Have Died In California's Drought
California’s six years of drought has left 102 million dead trees across 7.7 million acres of forest in its wake, the U.S. Forest Service (USFS) announced following an aerial survey. If that is not horrendous enough, 62 million trees died in the year 2016 alone—an increase of more than 100 percent compared to 2015.
“The scale of die-off in California is unprecedented in our modern history,” Randy Moore, a forester for the U.S. Forest Service, told the Los Angeles Times, adding that trees are dying “at a rate much quicker than we thought.”
“You look across the hillside on a side of the road, and you see a vast landscape of dead trees,” added Adrian Das, a U.S. Geological Survey ecologist whose office is located in Sequoia National Park. “It’s pretty startling.”
Most of the dead trees are located in 10 counties in the southern and central Sierra Nevada region.
“Five consecutive years of severe drought in California, a dramatic rise in bark beetle infestation and warmer temperatures are leading to these historic levels of tree die-off,” the USFS said.
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Saharan Dust In The Wind
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Dust’s climate role
McGee and his colleagues obtained sediment core samples from the Bahamas that were collected in the 1980s by scientists from the Woods Hole Oceanographic Institution. They brought the samples back to the lab and analyzed their chemical composition, including isotopes of thorium — an element that exists in windblown dust worldwide, at known concentrations.
They determined how much dust was in each sediment layer by measuring the primary isotope of thorium, and determined how fast it was accumulating by measuring the amount of a rare thorium isotope in each layer.
In this way, the team analyzed sediment layers from the last 23,000 years, and showed that around 16,000 years ago, toward the end of the last ice age, the dust plume was at its highest, lofting at least twice the amount of dust over the Atlantic, compared to today. However, between 5,000 and 11,000 years ago, this plume weakened significantly, with just half the amount of today’s windblown dust.
Colleagues at Yale University then plugged their estimates into a climate model to see how such changes in the African dust plume would affect both ocean temperatures in the North Atlantic and overall climate in North Africa. The simulations showed that a drop in long-range windblown dust would raise sea surface temperatures by 0.15 degrees Celsius, drawing more water vapor over the Sahara, which would have helped to drive more intense monsoon rains in the region.
“The modeling showed that if dust had even relatively small impacts on sea surface temperatures, this could have pronounced impacts on precipitation and winds both in the north Atlantic and over North Africa,” McGee says. Noting that the next key step is to reduce uncertainties in the modeling of dust’s climate impacts, he adds: “We’re not saying, the expansion of monsoon rains into the Sahara was caused solely by dust impacts. We’re saying we need to figure out how big those dust impacts are, to understand both past and future climates.”
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Physics
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Nylon Thread Made Into Artificial Muscles
Using a combination of ordinary nylon thread and conductive ink, MIT scientists have created artificial muscles that can perform many of the motions found in natural muscle tissue. The researchers believe that the new flexing devices could be used in a range of applications, from robotics and artificial limbs to powered flexible components for use in the automobile and aviation industries.
Created by manipulating nylon fibers in a relatively simple manufacturing process, the new material responds to heat by contracting in length and expanding in girth. In this way, when a heat source is applied, such as using conductive ink that warms the nylon filaments when a voltage is applied, the researchers have demonstrated that the new "muscles" are capable of reliable performance even after at 100,000 bending cycles, and able to bend and spring back at over 17 times per second.
To make this artificial muscle, the cross-section of the nylon thread first needed to be specifically shaped using a rolling mill to compress its cross-section from round to rectangular or square. Then, by painting conductive ink on one side and making it heat up, the fiber bends in that direction. By altering the direction of this heating, the researchers found that they could also make the material produce more intricate motions, including moving in circles and figures-of-eight.
Other attempts at making artificial muscles from polymer fishing line using twisted coils of filament have been able to emulate basic straight-line muscle activity that could stretch and retract in greater amounts, as well as hold and release more energy than natural muscles. But these devices needed linear actuators to move them, so were slower and more energy intensive than the new MIT versions. And though other research, such as using carbon nanotubes combined with rubber, could provide more than a million linear contraction cycles, they are far too expensive for common applications.
"This method is novel and elegant, with very good experimental data supported by appropriate physics-based models," said Geoffrey Spinks, a professor at the University of Wollongong Australia, who was not connected with this research. "This is a simple idea that works really well. The materials are inexpensive. The manufacturing method is simple and versatile. The method of actuation is by simple electrical input. The bending actuation performance is impressive in terms of bending angle, force generated, and speed."
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