Throughout the universe, supersonic shock waves propel cosmic rays and supernova particles to velocities near the speed of light. The most high-energy of these astrophysical shocks occur too far outside the solar system to be studied in detail and have long puzzled astrophysicists. Shocks closer to Earth can be detected by spacecraft, but they fly by too quickly to probe a wave's formation. Opening the door to new understanding
Now a team of scientists has generated the first high-energy shock waves in a laboratory setting, opening the door to new understanding of these mysterious processes. "We have for the first time developed a platform for studying highly energetic shocks with greater flexibility and control than is possible with spacecraft," said Derek Schaeffer, a physicist at Princeton University and the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL), and lead author of a July paper in Physical Review Letters that outlines the experiments.
Schaeffer and colleagues conducted their research on the Omega EP laser facility at the University of Rochester Laboratory for Laser Energetics. Collaborating on the project was PPPL physicist Will Fox, who designed the experiment, and researchers from Rochester and the universities of Michigan and New Hampshire. "This lets you understand the evolution of the physical processes going on inside shock waves," Fox said of the platform.
To produce the wave, scientists used a laser to create a high-energy plasma -- a form of matter composed of atoms and charged atomic particles -- that expanded into a pre-existing magnetized plasma. The interaction created, within a few billionths of a second, a magnetized shock wave that expanded at a rate of more than 1 million miles per hour, congruent with shocks beyond the solar system. The rapid velocity represented a high "magnetosonic Mach number" and the wave was "collisionless," emulating shocks that occur in outer space where particles are too far apart to frequently collide.
Discovery by accident
Discovery of this method of generating shock waves actually came about by accident. The physicists had been studying magnetic reconnection, the process in which the magnetic field lines in plasma converge, separate and energetically reconnect. To investigate the flow of plasma in the experiment, researchers installed a new diagnostic on the Rochester laser facility. To their surprise, the diagnostic revealed a sharp steepening of the density of the plasma, which signaled the formation of a high Mach number shock wave.
To simulate the findings, the researchers ran a computer code called "PSC" on the Titan supercomputer, the most powerful U.S. computer, housed at the DOE's Oak Ridge Leadership Computing Facility. The simulation utilized data derived from the experiments and results of the model agreed well with diagnostic images of the shock formation.
Humans aren't the only actors on the planet. To avoid being eaten, some jumping spiders pretend to be ants, according to Cornell University research published in Proceedings of the Royal Society B.
Ants are aggressive at defending themselves: They are well-armed with bites, stings and formic acid. Ant-mimicking jumping spiders -- Myrmarachne formicaria -- in contrast, can't do much more than run on their eight legs when attacked. Not surprisingly, insect predators tend to prefer spiders over ants, so appearing to be an ant confers significant protection.
Protective mimicry is a remarkable example of adaptive evolution: Moths can be colored like butterflies and grasshoppers may look like tiger beetles. While most mimicry studies focus on traits like color and shape, the researchers used multiple high-speed cameras and behavioral experiments to pinpoint how the spider's movements mimic ants.
Ant-mimicking spiders walk using all eight legs but pause frequently to raise their forelegs to mimic ant antennae. When walking, they take winding trajectories of about five to 10 body lengths, which made them look like ants following pheromone trails. While the researchers could see what the spiders were doing thanks to high-speed cameras, many potential predators have slower visual systems, so that to them the mimics appear to be moving just like an ant would.
The researchers note that the findings "highlight the importance of dynamic behaviors and observer perception in mimicry."
Researchers at Argonne looked at the dynamics of the transport of
certain elements -- especially rubidium -- at the interface between
water and mica, a flat transparent mineral pictured here.
In order to understand various environmental processes and learn to better address the effects of pollution, scientists have been interested in tracking the movement of elements through the environment, particularly at interfaces between water and minerals.
In a new study from the U.S. Department of Energy's (DOE) Argonne National Laboratory, in collaboration with the University of Illinois and Chicago and the University of Delaware, chemists have been able to look at the interface between water and muscovite mica, a flat mineral commonly found in granite, soils and many sediments. In particular, the researchers looked at the capture and release of rubidium -- a metal closely related to but more easily singled out than common elements like potassium and sodium.
Essentially, it's like looking for a goldfinch in a tree, and using a technique that only shows you where yellow things are."
In the experiment, the researchers flowed a rubidium-containing solution over the mica, which caused rubidium atoms to replace the potassium that occurs naturally near the surface of the mica. Then the rubidium solution was replaced for one containing sodium, which in turn replaced the rubidium atoms.
According to Argonne chemist Sang Soo Lee, who led the study, the dynamics of the ion transport were largely controlled by electrostatic properties at the interface between the mica and the water. Essentially, the rubidium atoms "clung" to the mica's surface similarly to how lint clings to clothing. The strength of the clinging behavior was determined mainly by how many water molecules were in between the mica's surface and the rubidium -- the fewer water molecules, the tighter the cling.
Lee and his Argonne colleague, chemist Paul Fenter, used Argonne's Advanced Photon Source, a DOE Office of Science User Facility, to observe the activity of the rubidium using a technique called resonant anomalous X-ray reflectivity. This technique allows scientists to probe the position of a single element at an interface.
"Essentially, it's like looking for a goldfinch in a tree, and using a technique that only shows you where yellow things are," Fenter said.
By using the technique, the researchers were able to condense the timeframe it takes to measure the signal from the data. "Normally these data take hours to measure, but now we can have a time resolution of one or two seconds," Fenter said.
Scientists ask how it's possible that certain coral reefs are thriving in this location.
Scientists have long believed that the waters of the Central and Northeast Pacific Ocean were inhospitable to deep-sea scleractinian coral, but a Florida State University professor's discovery of an odd chain of reefs suggests there are mysteries about the development and durability of coral colonies yet to be uncovered.
Associate Professor of Earth, Ocean and Atmospheric Science Amy Baco-Taylor, in collaboration with a team from Texas A&M University, observed these reefs during an autonomous underwater vehicle survey through the seamounts of the Northwestern Hawaiian Islands.
In an article published in the journal Scientific Reports, Baco-Taylor and her team document these reefs and discuss possible explanations for their appearance in areas considered impossibly hostile to reef-forming scleractinia, whose communities are formed by small, stony polyps that settle on the seabed and grow bony skeletons to protect their soft bodies.
"I've been exploring the deep-sea around the Hawaiian Archipelago since 1998, and I'd seen enough to know that the presence of these reefs at these depths was definitely unexpected," Baco-Taylor said.
Areas like the North Atlantic and South Pacific are particularly fertile habitats for deep-sea scleractinian reefs, but a combination of factors led scientists to believe that the accumulation of deep-sea coral colonies into healthy reefs was exceedingly unlikely in the deep waters of the North Pacific.
Low levels of aragonite, an essential mineral in the formation of scleractinian skeletal structures, in the region make it difficult for the coral polyps to develop their rugged coral skeletons. In addition, North Pacific carbonate dissolution rates, a measure of the pace at which carbonate substances like coral skeletons dissolve, exceed those of the more amenable North Atlantic by a factor of two.
In other words, these reefs simply should not exist.
"Even if the corals could overcome low aragonite saturation and build up robust skeletons, there are areas on the reefs that are just exposed skeleton, and those should be dissolving," Baco-Taylor said. "Even if the species could survive in the area, we shouldn't be finding an accumulation of reef."
In the study, Baco-Taylor and her team articulate two potential reasons for the improbable success of these hardy reefs. Higher concentrations of chlorophyll in the areas of pronounced reef growth suggests that an abundance of food may provide the excess energy needed for calcification in waters with low aragonite saturation. Suitable current velocities in the area may also help the reefs to flourish.
But neither of these factors tell the whole story.
"Neither the chlorophyll nor the currents explain the unusual depth distributions of the reefs, why they actually get shallower moving to the northwest along the seamounts," Baco-Taylor said. "There's still a mystery as to why these reefs are here."
The unexpected discovery of these reefs has prompted some to reconsider the effects of ocean acidification on vulnerable coral colonies. At a time when stories about the wholesale demise of reefs around the world are sparking alarm, these findings may offer a glimmer of hope.
"These results show that the effect of ocean acidification on deep-water corals may not be as severe as predicted," said David Garrison, a program director in the National Science Foundation's Division of Ocean Sciences, which funded the research. "What accounts for the resilience of these corals on seamounts in the Pacific remains to be determined."
The reefs observed during this research occur primarily outside of the local protected Papah?naumoku?kea Marine National Monument, which means they exist in areas where destructive trawling is permitted and active.
Nicole Morgan, an FSU doctoral candidate and a coauthor of the article, said that locating these survivalist reefs is crucial because it gives scientists a chance to preserve them.
"We want to know where these habitats are so that we can protect them," Morgan said. "We don't want important fisheries to collapse, which often happens when reefs disappear, but we also want to protect them because they're vulnerable, and we don't want to destroy habitats."
The discovery of these puzzling reefs shows that there are still gaps at the edges of our scientific understanding waiting to be filled. The success of hypothesis-driven exploration, like the kind that produced these findings, demonstrates the importance of continuing to strike out into the unknown.
"These results highlight the importance of doing research in unexplored areas, or 'exploration sciences' as we like to call it," said Brendan Roark, associate professor of geography at Texas A&M University and Baco-Taylor's co-principal investigator.
If there are additional reefs sprinkled across the Northwestern Hawaiian seamounts, Baco-Taylor wants to find them. Further study of these reefs could reveal important secrets about how these organisms might endure in the age of climbing carbon dioxide levels and ocean acidification.
A new species looking after their offspring, Daenerytanais maieuticus,
is named after the fiction character Daenerys Targaryen "Mother of
Dragons", Khaleesi in the TV series Game of Thrones.
A scientific team has found the first evidence of parental care in Tanaidaceans, dating back to more than 105 million years, according to a new study published in the journal Scientific Reports, from Nature group. These new findings are based on the study of three small crustaceans from different species of the Cretaceous -Alavatanais carabe, Alavatanais margulisae and Daenerytanais maieuticus- preserved in amber pieces from the sites in Peñacerrada (Álava, Spain) and La Buzinie (Charente, France), reference models in the study of fossil records in amber with bioinclusions of the Mesozoic in Europe.
The authors of the study are the researchers Alba Sánchez and Xavier Delclòs, from the Faculty of Earth Sciences and the Biodiversity Research Institute (IRBio) of the University of Barcelona; Enrique Peñalver, from the Geological and Mining Institute of Spain; Michael S. Engel, from the University of Kansas (United States); Graham Bird (New Zealand), and Vincent Perrichot, from the University Rennes 1 (France).
Parental care: protecting offspring millions of years ago
Lots of extant crustacean species show parental care, increasing survival possibilities in the natural habitat. This reproductive strategy, which evolved independently in different lineages, is common in terrestrial and water aquatic species (in oceans, lakes, etc.).
However, there is not a lot of fossil evidence of caring behaviours in crustaceans. Although parental care is documented in fossil records -for instance in ostracods from 450 million years ago- the published article in the journal Scientific Reports shows the first evidence of this behavior in Tanaidacea; a group of small crustaceans belonging to the superorder Peracarida.
"These new findings make up for the first fossil evidence of parental care in the order Tanaidacea. The findings show that certain caring behaviours and related morphological adaptations already existed during the Lower Cretaceous and were almost kept without changes for more than 105 million years" says the researcher Alba Sánchez (UB-IRBio), first author of the study.
Marsupial care of brood-offspring
A feature of Tanaidaceans -and other peracarid crustaceans- is that females have the marsupium, a ventral brood pouch to retain and protect the eggs. After the fertilization, eggs develop into embryos and then young individuals inside the marsupium.
According to the lecturer Xavier Delclòs (UB-IRBio), "The marsupium represents a safe environment for the offspring and may contribute to the success of tanaidaceans in different habitats (marine and freshwater environments, and even humid terrestrial areas), as proposed for some tanaidaceans found in Cretaceous amber." Daenerytanais maieuticus: the Khaleesi of crustaceans According to the new study, the two tanaidacean specimens found in amber pieces from Álava (Spain) -two females of Alavatanais carabe and Alavatanais margulisae- show structures involved in the formation of a marsupium to carry eggs and offspring in sexually mature females.
Regarding the French site of La Buzinie, the specimen they identified is a female of Daenerytanais maieuticus, which was preserved in amber together with her marsupium full of eggs. This fossil, representing a new genus and species, is named after the fiction character Daenerys Targaryen, "Mother of Dragons," from the series of fantasy novels A Song of Ice and Fire, written by George R. R. Martin, which inspired the well-known TV series Game of Thrones.
The soft artificial heart resembles the human heart in appearance and function.
It looks like a real heart. And this is the goal of the first entirely soft artificial heart: to mimic its natural model as closely as possible. The silicone heart has been developed by Nicholas Cohrs, a doctoral student in the group led by Wendelin Stark, Professor of Functional Materials Engineering at ETH Zurich. The reasoning why nature should be used as a model is clear. Currently used blood pumps have many disadvantages: their mechanical parts are susceptible to complications while the patient lacks a physiological pulse, which is assumed to have some consequences for the patient. "Therefore, our goal is to develop an artificial heart that is roughly the same size as the patient's own one and which imitates the human heart as closely as possible in form and function," says Cohrs.
A well-functioning artificial heart is a real necessity: about 26 million people worldwide suffer from heart failure while there is a shortage of donor hearts. Artificial blood pumps help to bridge the waiting time until a patient receives a donor heart or their own heart recovers.
The soft artificial heart was created from silicone using a 3D-printing, lost-wax casting technique; it weighs 390 grams and has a volume of 679 cm3. "It is a silicone monoblock with complex inner structure," explains Cohrs. This artificial heart has a right and a left ventricle, just like a real human heart, though they are not separated by a septum but by an additional chamber. This chamber is in- and deflated by pressurized air and is required to pump fluid from the blood chambers, thus replacing the muscle contraction of the human heart.
Thinking in a new direction
Anastasios Petrou, a doctoral student of the Product Development Group Zurich, led by Professor Mirko Meboldt evaluated the performance of this soft artificial heart. The young researchers have just published the results of the experiments in the scientific journal Artificial Organs.
They proved that the soft artificial heart fundamentally works and moves in a similar way to a human heart. However, it still has one problem: it currently lasts for about only 3,000 beats, which corresponds to a lifetime of half to three quarters of an hour. After that, the material can no longer withstand the strain. Cohrs explains: "This was simply a feasibility test. Our goal was not to present a heart ready for implantation, but to think about a new direction for the development of artificial hearts." Of course, the tensile strength of the material and the performance would have to be enhanced significantly. Zurich Heart brings researchers together
Cohrs and Petrou met in the Zurich Heart Project, a flagship project of University Medicine Zurich that brings together 20 research groups from various disciplines and institutions in Zurich and Berlin. Part of the research focuses on improvements on existing blood pumps, such as how to reduce blood damage induced from the mechanical parts of the pump, while others explore extremely elastic membranes or more biocompatible surfaces. This is done in close collaboration with the clinicians in Zurich and Berlin.
The lively exchanges among the researchers also helped this Zurich Heart sub-project. Doctoral students of Product Development Group Zurich, who are working on new technologies for blood pumps, have developed a testing environment with which they can simulate the human cardiovascular system. The researchers of the silicone heart made use of this testing environment for their development process which also included the use of a fluid with comparable viscosity as human blood. "Currently, our system is probably one of the best in the world," says Petrou proudly.
The multiple images of the discovered galaxy are indicated by white
arrows (bottom right shows the scale of the image in seconds of arc).
According to Einstein's theory of General Relativity when a ray of light passes close to a very massive object, the gravity of the object attracts the photons and deviates them from their intial path. This phenomenon, known as gravitational lensing, is comparable to that produced by lenses on light rays, and acts as a sort of magnifier, changing the size and intensity of the apparent image of the original object.
Using this effect, a team of scientists from the Instituto de Astrofisica de Canarias (IAC) led by researcher Anastasio Díaz-Sánches of the Polytechnic University of Cartagena (UPT) has discovered a very distant galaxy, some 10 thousand million light years away, about a thousand times brighter than the Milky Way. It is the brightest of the submillimetre galaxies, called this because of their very strong emissionin the far infrared. To measure it they used the Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory (Garafía, La Palma).
"Thanks to the gravitational lens" notes Anastasio Díaz Sánchez, a researcher at the UPCT and first author of the article " produced by a cluster of galaxies between ourselves and the source, which acts as if it was a telescope, the galaxy appears 11 times bigger and brighter than it really is, and appears as several images on an arc centred on the densest part of the cluster, which is known as an "Einstein Ring." The advantage of this kind of amplification is that it does not distort the spectral properties of the light, which can be studied for these very distant objects as if they were much nearer."
To find this galaxies, whose discovery was recently published in an article in the Astrophysical Journal Letters, a search of the whole sky was carried out, combining the data bases of the satellites WISE (NASA) and Planck (ESA) in order to identify the brightest submillimetre galaxies. Its light, amplified by a much nearer galaxy cluster acting as a lens, forms an image which appears much bigger than it should, and thanks to this effect they could characterize its nature and properties spectroscopically using the GTC.
Forming stars at high velocity
The galaxy is notable for having a high rate of star formation. It is forming stars at a rate of 1000 solar masses per year, compared to the Milky Way which is forming stars at a rate of some twice a solar mass per year. Susana Iglesias-Groth, an IAC astrophysicist and a co-author of the article, adds. "This type of objects harbour the most powerful star forming regions known in the universe. The next step will be to study their molecular content."
The fact that the galaxy is so bright, its light is gravitationally amplifed, and has multiple images allows us to look into its internal properties, which would otherwise not be possible with such distant galaxies.
Spiral galaxy Messier 61, picture taken with the Hubble Space Telescope. Our Milky Way might look like this galaxy.
How does the gas in the centre of the Milky Way behave? Researchers from Heidelberg University, in collaboration with colleagues from the University of Oxford, recently investigated the motion of gas clouds in a comprehensive computer simulation. The new model finally makes it possible to conclusively explain this complex gas motion. Astrophysicists Dr Mattia C. Sormani (Heidelberg) and Matthew Ridley (Oxford) conducted the research, on Heidelberg's part, at the Collaborative Research Centre "The Milky Way System" (CRC 881).
Our solar system is located in the outer regions of the Milky Way, a disk-shaped galaxy with an approximate diameter of 100,000 light years. From Earth, its appearance can only be observed indirectly, by measuring positions and movements of stars and gas clouds. The Milky Way is most likely a barred spiral galaxy, a very commonly observed type of galaxy in the universe. A well-known example is the galaxy M61.
In addition to the luminous stars, a substantial portion of the visible matter in our Milky Way is interstellar gas. The distribution and motion of this gas is very complex. Especially in the centre of the Galaxy, there are substantial discrepancies between the measured quantities of gas and the low rate of star formation. "Our simulation not only eliminates these discrepancies found in previous models, but also allows us to reproduce the observed motion of the gas surprisingly well," says Prof. Dr Ralf S. Klessen, one of the researchers at the Institute of Theoretical Astrophysics at the Centre for Astronomy of Heidelberg University (ZAH).
In the new model, gas clouds in the so-called central molecular zone (CMZ) -- the innermost 1,500 light years of the Milky Way -- move on an elliptical central disk that has two spiral arms. Gas from the surroundings flows through these arms into the CMZ. Collisions of gas clouds create shock waves, generating turbulence. "This turbulence could prevent the gas clouds from collapsing into stars, providing a consistent explanation for the unexpectedly low rate of star formation in this region," says Dr Sormani.
The computer simulation allowed the researchers to create a spatial image of the centre of the Galaxy and determine the position of some known gas clouds within this three-dimensional "map" for the first time. The astrophysicists now plan to optimise their simulation in order to improve their results and better match observational data. They also hope to clear up any remaining questions such as the pronounced asymmetry of the gas distribution in the central zone of the Milky Way. Further simulations, based on the temporal development of the chemical composition of the gas, are intended to unravel this mystery.
After a massive asteroid slammed into Earth 66 million years ago, an estimated three-quarters of all plant and animal species went extinct. While scientists continue to study the K-T extinction event, as the cataclysmic episode is known, it is clear that astrophysical events have the potential to cause unfathomable damage to celestial bodies and anything living on them.
Our mammalian ancestors survived the K-T extinction, but today’s mammals — including humans — would likely not be so fortunate should an event of greater scale happen again. The same holds true for birds, reptiles, and many of the world’s species.
At least one animal, however, is predicted to survive nearly every natural disaster, except for the death of the sun. According to a new study published in Scientific Reports, that extraordinarily resilient creature is the tardigrade, an eight-legged micro-animal that is also known as the water bear, space bear, and moss piglet. Whatever one wants to call it, researchers predict that this tiny species will be around for at least 10 billion years.
Tardigrades can survive for up to 30 years without food or water. They endure temperature extremes ranging from well below freezing to 302 degrees Fahrenheit, and have been found in the ocean depths. Although just .02 inches long, their lifespan is about 60 years.
To assess what apocalyptic event could lead to the annihilation of all life on Earth, the researchers used detailed mathematical modeling to predict what would happen to the tardigrade — the world’s most indestructible species — should there be a major asteroid impact, supernova, or gamma-ray burst. The overarching goal of the research was to find out how long life can survive on a planet once it has formed there.
“Most previous studies focused on the survival of humans, which are very sensitive to changes in the atmosphere or climate of the earth and can be eliminated by the impact of an asteroid, nuclear winter, or bad politics,” said senior author Abraham Loeb, who is a professor and chair of the Harvard Astronomy Department and is the director of the Institute for Theory and Computation. “To our surprise, tardigrades are likely to survive all astrophysical catastrophes.”
RELATED: Tardigrade ‘Water Bear’ Dries to a Crisp and Then Comes Back to Life
Loeb conducted the investigation with lead author David Sloan of the University of Oxford’s department of physics-astrophysics and his Oxford colleague and co-author Rafael Alves Batista.
Regarding asteroids, the scientists calculated that there are only a dozen known rocky sun-orbiting bodies with enough mass to boil the oceans — a calamity that could wipe out even the sturdy tardigrades. These include Vesta and Pluto.
“In terms of species death, a big asteroid would be the largest threat,” Sloan said.
But Loeb added that “such events are extremely rare and will not happen before the sun will die.”
In terms of supernovae, the researchers found that in order for an exploding star to boil the oceans, it would need to be 0.14 light-years away. The threat posed from these exploding stars to Earth is negligible, they determined, since the closest star to the sun is four light years away. The probability of a massive star exploding close enough to Earth to kill all forms of life on it, within the sun’s lifetime, is therefore very low.
If this phenomenon were to happen, Sloan said, “a nearby supernova would be a disastrous event for most life on a planet, but species like the tardigrade could well live on.”
Gamma-ray bursts are even brighter than supernovae, but the scientists believe that they are too far away from Earth to be considered a viable threat. To boil our planet’s oceans, they would need to be no more than 40 light-years away, so the likelihood of a burst occurring at such proximity to Earth is minor.
“Mainly we’ve found that, once life starts, it seems very unlikely that it will be killed off by any of the usual suspects for annihilating humans,” Sloan said. “If we find planets fit for life and search them, if life ever was there, it probably still should be in some form.”
The researchers speculate that tardigrades, or animals similar to them, could be living on planets other than Earth, so long as there is a source of water.
Last year, genetic analysis on one of the most stress-tolerant tardigrade species — Ramazzottius varieornatus — identified a unique protein that makes it so tough. An accompanying video (above) showed how a severely dehydrated tardigrade will display no visible signs of life before it is resuscitated with a drop of water.
“Water is needed to revive them, but they have been shown to stay alive after being dehydrated,” Loeb said. “Their systems shut down without water, but once water is introduced they are brought back to life and can reproduce again. This was demonstrated in an experiment done a decade ago where they were taken out to space for a week and exposed to vacuum and dehydration; when brought back, a significant fraction of them produced healthy embryos.”
Astronomers are soon hoping to perform spectroscopy, a process that seeks signatures for life, on exoplanets. The new experimental study suggests what they might find.
A George Washington University researcher helped design and construct a prototype for a new solar cell that integrates multiple cells stacked into a single device capable of capturing nearly all of the energy in the solar spectrum.
The new design, which converts direct sunlight to electricity with 44.5 percent efficiency, has the potential to become the most efficient solar cell in the world.
The approach is different from the solar panels commonly seen on rooftops or in fields. The new device uses concentrator photovoltaic (CPV) panels that use lenses to concentrate sunlight onto tiny, micro-scale solar cells. Because of their small size -- less than one millimeter square -- solar cells that utilize more sophisticated materials can be developed cost effectively.
The study, "GaSb-based Solar Cells for Full Solar Spectrum Energy Harvesting," was published in the journal Advanced Energy Materials.
The stacked cell acts almost like a sieve for sunlight, with the specialized materials in each layer absorbing the energy of a specific set of wavelengths, said Matthew Lumb, lead author of the study and a research scientist at the School of Engineering and Applied Science. By the time the light is funneled through the stack, just under half of the available energy has been converted into electricity. By comparison, the most common solar cell today converts only a quarter of the available energy into electricity.
"Around 99 percent of the power contained in direct sunlight reaching the surface of Earth falls between wavelengths of 250 nanometers and 2,500 nanometers, but conventional materials for high-efficiency multi-junction solar cells cannot capture this entire spectral range," Dr. Lumb said. "Our new device is able to unlock the energy stored in the long-wavelength photons, which are lost in conventional solar cells, and therefore provides a pathway to realizing the ultimate multi-junction solar cell."
Scientists have worked to develop more efficient solar cells for years, however this approach has two novel aspects. It uses a family of materials based on gallium antimonide (GaSb) substrates, which are usually found in applications for infrared lasers and photodetectors. These GaSb-based solar cells are assembled into a stacked structure along with high efficiency solar cells grown on conventional substrates that capture shorter wavelength solar photons. In addition, the stacking procedure uses a technique known as transfer-printing, which enables three dimensional assembly of these tiny devices with a high degree of precision.
This particular solar cell is very expensive, but researchers believe it was important to show the upper limit of what is possible in terms of efficiency. Despite the current costs of the materials involved, the technique used to create the cells shows promise, researchers say. Eventually a similar product enabled by cost reductions from very high solar concentration levels and technology to recycle the expensive growth substrates could be brought to market.
A female raven named “None” was recently disqualified from a study on bird smarts. The reason? She was too clever.
The experiment involved using a tool — a stone — to operate a “puzzle box” device that functioned like a vending machine. To receive a savory food reward, bird participants had to place the stone in a tubular slot at the top of the vending machine-type box. The action triggered the release of a meaty dog kibble that many ravens love.
The problem with None was that she figured out how to get the food without using the stone.
“Instead of using the stone and dropping it through the tube to push the platform down, she stuffed the tube with bark pieces and pushed on it with her beak or a stick, which collapsed the platform,” co-author Mathias Osvath of Lund University said. “We had to exclude her from the rest of the experiments as she did not need the functional tool anymore.”
The experiments of Osvath and co-author Can Kabadayi went on with ravens Rickard, Juno, Embla, and Siden that, like None, live in outdoor aviaries at Lund’s Corvid Cognition Station, Sweden. The results, published in the journal Science, show that ravens can plan for the future, forgo immediate rewards in order to gain better ones later on, and even have the ability to barter using tokens that function like money.
Because ravens typically do not use tools in the wild, and bartering is not one of their known natural behaviors, the findings provide evidence that these birds possess complex cognitive skills that can be flexibly applied to novel situations. Their brain power includes reasoning, drawing from both long and short-term memory and, at times, exhibiting restraint.
Great apes, such as chimps and gorillas, possess similar skills, but monkeys previously flunked tests that ravens could ace. Even human kids must be at least 4 years old in order to achieve certain cognition and behavior feats, with control of impulsiveness being particularly challenging, as many parents with youngsters in the “terrible twos” might observe.
Kids, as well as ravens, require time to learn that restraint can often be beneficial. Considering that the average lifespan of a raven in the wild is just 10–15 years, their cognitive achievements are all the more remarkable.
Regarding raven memory, prior research found that a “raven can remember a single encounter with a human for at least a month,” so “they can remember information for a very long time,” Osvath said.
For the new series of experiments, Osvath and Kabadayi first trained the ravens to use a tool, which again was a stone, to open the puzzle box in order to access a food reward. The ravens were then presented with the box, but not the tool. The box was subsequently removed.
One hour later, the ravens were presented with the tool, as well as several toy “distractors” that were too large to fit into the slot of the vending machine-like puzzle box. The distractors included a wooden wheel, a wooden ball, a T-shaped metal pipe and a plastic toy car. Nearly every raven chose the correct, apparatus-opening tool, with a success rate of 86%.
A high success rate (78 percent) was also seen in similar experiments where ravens used a token — a blue plastic bottle cap — to later barter for a food reward. The ravens planned for bartering more accurately than apes have done in earlier studies, the researchers reported. The birds even began to store their tokens, like saving money, for future trades.
Finally, the ravens were presented with the correct, apparatus-opening tool, distractor tools, and an immediate food reward, but were only permitted to select one item. The ravens demonstrated self-control on par with great apes by opting for the tool, which eventually earned them a better food reward than the immediate treat.
The study only looked at ravens, but it is possible that other corvids, such as crows and scrub jays, possess similar — if not equally impressive — smarts.
Florida scrub jay
“When it comes to brains, recent research suggests that bird brains can pack a much larger number of neurons than mammalian brains,” Osvath said. “In particular, song birds and parrots have very high numbers of neurons per unit of volume.”
“Corvids are among the largest song birds — the raven is the largest — hence they have the largest brains and more neurons than others,” he continued. “This might be a clue to why corvids are cognitively more complex than other birds, given that neurons are the basic information processing units.”
Markus Boeckle and Nicola Clayton of the University of Cambridge Department of Psychology wrote an “Insights” commentary, also published in Science, concerning the new discoveries about ravens.
Boeckle said that the determinations advance “our understanding of complex cognition, as we did not have evidence in any (non-human) animal that future planning is flexibly used across behaviors.”
“By providing evidence for flexible use of future planning in animals, we can assume that, in some species, the cognitive abilities are based on general intelligence,” Boeckle added. “Furthermore, we can start to understand the selective pressures, which led to the evolution of flexible problem solving abilities.”
Other times, they win so much they get sick and tired of winning.
Now, scientists have figured out how to reach inside a mouse’s brain and flick a neuronal switch that triggers them to either become alpha males who excel at aggressive encounters — or become more likely to retreat.
A team of researchers in China identified a circuit in the brain that plays a strong role in social dominance in mice, and were able to activate the region — known as the dorsomedial prefrontal cortex — by hitting it with light beams.
“We can change the dominance behavior very quickly by changing the activity of this one particular brain area,” said Hailan Hu, the study’s senior principle investigator and a professor at Zhejiang University in China. “It does so without changing the physical strength or aggression level of the animals.”
Many animals engage in complex forms of competitive rituals to create intricate structures of social hierarchy. Researchers who study the process have observed a phenomenon called the "winner effect,” in which each victory over a peer increases the odds of winning the next social dominance showdown.
The researchers in China constructed a standardized competition that pitted male mice against each other inside a tube facing each other.
The researchers then recorded how much each one engaged in a range of behaviors: initiating a push against their opponent, pushing back, resistance, retreat, or stillness.
Brain monitoring revealed that a particular subset of neurons in the brain area they were looking at became more active during so-called “dominant” behaviors of pushing and resistance in the contest.
Next, the scientists took mice that had already established a social rank, and gave them drugs that inhibited the functioning of this subset of neurons. Within hours, the drugged mice engaged in fewer and less vigorous pushes and push-backs — and retreated more often.
Then, when researchers used optogenetics to stimulate the brain area with light during a social dominance encounter, the stimulated mice achieved a 90 percent success rate over other previously dominant mice, without affecting the motor performance or anxiety level of the animal receiving the light treatment.
The team published their findings today in the journal Science.
Scientists from China have just performed the first ever quantum teleportation from Earth to space. Does this mean we are now living in the future envisioned in Star Trek?
Actually, no physical matter was actually “beamed up,” unfortunately — just photons. But this breakthrough might make for a better and more secure internet in the future.
"Quantum teleportation brings to mind Star Trek’s transporter, where crew members are disassembled in one location to be reassembled in another,” explained astrophysicist Brian Koberlein from the Rochester Institute of Technology. “Real quantum teleportation is a much more subtle effect where information is transferred between entangled quantum states. It’s a quantum trick that could give us the ultimate in secure communication."
Long-distance quantum communication has been recognized as a keystone for things like large-scale quantum networks and quantum computation. But previous quantum communications — or “teleportation” — experiments have seen limited success.
Entanglement is a tenuous state, with the link easily broken. Previous attempts using fiber networks have been limited to distances of 100 km or less due to photon loss inside the fiber. Some of the first attempts at “over-the-air” teleportation using light beams were only successful at night because of daytime atmospheric turbulence.
“An outstanding open challenge for a global-scale ‘quantum internet’ is to significantly extend the range for teleportation,” wrote Ji-Gang Ren and his colleagues in their new paper about the teleportation feat. They said that the most promising solution to the distance problem is to exploit satellites, which can “conveniently connect two remote points on the Earth with greatly reduced channel loss because most of the photons’ propagation path is in empty space.”
The weird phenomenon of entanglement might seem difficult to fathom, but it occurs when two quantum objects, such as photons, form at the same instant and point in space. Basically, they share the same existence and the state of one object affects the state of the other. But in theory, this shared existence should continue even when the photons are separated by long distances.
“For quantum teleportation, one of these entangled objects is measured in combination with the object to be ‘teleported,’” explained Koberlein, who was not involved with the research, “and the result of this measurement is then sent to another location, where a similar combined measurement is made. Since the entangled objects are part of both measurements, quantum information can be teleported.”
For the latest attempt by the Chinese researchers, they used a new satellite called Micius that was launched last year by a Long March rocket. The satellite contains an extremely sensitive photon receiver that can detect the quantum states of single photons transmitted from the ground.
They used several techniques to “optimize the link efficiency and overcome atmospheric turbulence,” including a “compact ultra-bright source of multi-photon entanglement, narrow beam divergence, high-bandwidth and high-accuracy acquiring, pointing, and tracking.”
They were successful with quantum teleportation from Earth to space at distances of up to 1,400 km, the furthest ever. The link-up wasn’t 100 percent successful however, as out of millions of photon states they attempted to transmit into space, just over 900 of them were successful.
C. mast is a commensal bacterium living on the surface of the eye.
Bugs in your eyes may be a good thing. Resident microbes living on the eye are essential for immune responses that protect the eye from infection, new research shows. The study, which appears in the journal Immunity on July 11, demonstrates the existence of a resident ocular microbiome that trains the developing immune system to fend off pathogens. The research was conducted at the National Eye Institute (NEI), part of the National Institutes of Health.
"This is the first evidence that a bacterium lives on the ocular surface long-term," explained Rachel Caspi, Ph.D., senior investigator in NEI's Laboratory of Immunology. "This work addresses a longstanding question about whether there is a resident ocular microbiome."
For years, the ocular surface was thought to be sterile because of the presence of an enzyme called lysozyme that destroys bacteria, antimicrobial peptides, and other factors that rid the eye of microbes that may land from the air (or from our fingers) onto the surface of the eye.
Anthony St. Leger, Ph.D., research fellow in Caspi's laboratory, was able to culture bacteria from the mouse conjunctiva, the membrane that lines the eyelids. He found several species of Staphylococci, which are commonly found on the skin, and Corynebacterium mastitidis (C. mast). But it wasn't clear whether those microbes had just arrived on the eye and were en route to being destroyed, or whether they lived on the eye for extended periods of time.
The researchers found that C. mast, when cultured with immune cells from the conjunctiva, induced the production of interleukin (IL)-17, a signaling protein critical for host defense. Upon further investigation, they found that IL-17 was produced by gamma delta T cells, a type of immune cell found in mucosal tissues. IL-17 attracted other immune cells called neutrophils -- the most abundant type of white blood cell -- to the conjunctiva and induced the release of anti-microbial proteins into the tears. The researchers are currently investigating the unique features that can make C. mast resistant to the immune response that it itself provokes and allow it to persist in the eye.
To determine whether the microbe was contributing to the immune response in mice, St. Leger formed two groups, one control (with C. mast) and one treated with an antibiotic to kill C. mast and other ocular bacteria, and then challenged them with the fungus, Candida albicans. The mice receiving antibiotics had a reduced immune response in their conjunctiva and were not able to eliminate C. albicans, leading to full-blown ocular infection. The control mice with normal C. mast on the other hand were able to fend off the fungus.
St. Leger noticed that mice from the NIH animal facility had C. mast on their eyes, but mice from the Jackson Laboratory (JAX) in Maine and other commercial vendors did not. This fortuitous observation allowed the researchers to determine if C. mast was truly a resident microbe, as opposed to a transient microbe that lands on the eye from the environment. They did this by inoculating C. mast-free mice with the microbe and determining if the microbe could be cultured from those animals' eyes many weeks later. They also determined whether the microbe could easily be transmitted among cagemates.
When inoculated with C. mast, JAX mice produced conjunctival gamma delta T cells that released IL-17. Bacteria could still be cultured from their eyes after many weeks. By contrast, several other strains of bacteria inoculated onto the eyes of JAX mice disappeared without inducing local immunity. "We still don't know what enables C. mast to successfully establish itself in the eye, whereas other similar bacteria fail to colonize," Caspi said.
Interestingly, C. mast was not spread to cage-mates even after eight weeks of co-housing; however, C. mast can be passed from mother to pup. Both of these observations support the notion that C. mast is a resident commensal, not a bacterium that is continually re-introduced to the eye from the skin or the environment, Caspi explained.
Although C. mast appears to stimulate a beneficial immune response, there may be situations in which it could cause disease, St. Leger noted. For instance, the elderly tend to have suppressed immune systems, which might allow C. mast to grow out of control and cause disease.
The researchers are currently investigating whether other bacteria play a role in regulating eye immunity.
"We've established the proof of concept of a central ocular microbiome," St. Leger said. "It's well known that there are good bacteria in the gut that modulate the immune response. Now we show that this relationship exists in the eye. That's important for how we think about treating ocular disease."
This is a map showing detachment of iceberg, based on data from NASA's Aqua Modis satellite. July 12, 2017.
A one trillion tonne iceberg -- one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice, monitored by the Swansea University-led MIDAS project, finally completed its path through the ice.
The calving occurred sometime between Monday 10th July and Wednesday 12th July, when a 5,800 square km section of Larsen C finally broke away.
The final breakthrough was detected in data from NASA's Aqua MODIS satellite instrument, which images in the thermal infrared at a resolution of 1km.
The iceberg, which is likely to be named A68, weighs more than a trillion tonnes.
Its volume is twice that of Lake Erie, one of the Great Lakes.
The iceberg weighs more than a trillion tonnes (1,000,000,000,000 metric tonnes), but it was already floating before it calved away so has no immediate impact on sea level. The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12%, and the landscape of the Antarctic Peninsula changed forever.
The development of the rift over the last year was monitored using data from the European Space Agency Sentinel-1 satellites -- part of the European Copernicus Space Component. Sentinel-1 is a radar imaging system capable of acquiring images regardless of cloud cover, and throughout the current winter period of polar darkness. The detachment of the iceberg was first revealed in a thermal infrared image from NASA's MODIS instrument, which is also able to acquire data in the Antarctic winter when cloud cover permits.
Although the remaining ice shelf will continue naturally to regrow, Swansea researchers have previously shown that the new configuration is potentially less stable than it was prior to the rift. There is a risk that Larsen C may eventually follow the example of its neighbour, Larsen B, which disintegrated in 2002 following a similar rift-induced calving event in 1995.
Professor Adrian Luckman of Swansea University, lead investigator of the MIDAS project, said:
"We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice. We will continue to monitor both the impact of this calving event on the Larsen C Ice Shelf, and the fate of this huge iceberg.
The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters.
The recent development in satellite systems such as Sentinel-1 and MODIS has vastly improved our ability to monitor events such as this."
The Larsen C Ice Shelf, which has a thickness of between 200 and 600 metres, floats on the ocean at the edge of The Antarctic Peninsula, holding back the flow of glaciers that feed into it.
Researchers from the MIDAS Project have been monitoring the rift in Larsen C for many years, following the collapse of the Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002. They reported rapid advances of the rift in January, May and June, which increased its length to over 200 km and left the iceberg hanging on by a thread of ice just 4.5 km (2.8 miles) wide.
The team monitored the earlier development of the rift using a technique called satellite radar interferometry (SRI) applied to ESA Sentinel-1 images. While the rift is only visible in radar images when it is more than 50m wide, by combining pairs of images, SRI allows the impact of very small changes in ice shelf geometry to be detected, and the rift tip to be monitored precisely.
Dr Martin O'Leary, a Swansea University glaciologist and member of the MIDAS project team, said of the recent calving:
"Although this is a natural event, and we're not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position. This is the furthest back that the ice front has been in recorded history. We're going to be watching very carefully for signs that the rest of the shelf is becoming unstable."
Professor Adrian Luckman of Swansea University added:
"In the ensuing months and years, the ice shelf could either gradually regrow, or may suffer further calving events which may eventually lead to collapse -- opinions in the scientific community are divided. Our models say it will be less stable, but any future collapse remains years or decades away."
Will another planet be added to the list of Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus and Neptune in our Solar System?
Last year, the existence of an unknown planet in our Solar system was announced. However, this hypothesis was subsequently called into question as biases in the observational data were detected. Now Spanish astronomers have used a novel technique to analyse the orbits of the so-called extreme trans-Neptunian objects and, once again, they point out that there is something perturbing them: a planet located at a distance between 300 to 400 times the Earth-Sun separation.
Scientists continue to argue about the existence of a ninth planet within our Solar System. At the beginning of 2016, researchers from the California Institute of Technology (Caltech, USA) announced that they had evidence of the existence of this object, located at an average distance of 700 AU or astronomical units (700 times the Earth-Sun separation) and with a mass ten times that of Earth.
Their calculations were motivated by the peculiar distribution of the orbits found for the trans-Neptunian objects (TNO) of the Kuiper belt, which apparently revealed the presence of a Planet Nine or X in the confines of the Solar System.
However, scientists from the Canadian-French-Hawaiian project OSSOS detected biases in their own observations of the orbits of the TNOs, which had been systematically directed towards the same regions of the sky, and considered that other groups, including the Caltech group, may be experiencing the same issues. According to these scientists, it is not necessary to propose the existence of a massive perturber (a Planet Nine) to explain these observations, as these are compatible with a random distribution of orbits.
Now, however, two astronomers from the Complutense University of Madrid have applied a new technique, less exposed to observational bias, to study a special type of trans-Neptunian objects: the extreme ones (ETNOs, located at average distances greater than 150 AU and that never cross Neptune's orbit). For the first time, the distances from their nodes to the Sun have been analysed, and the results, published in the journal 'MNRAS: Letters', once again indicate that there is a planet beyond Pluto.
The nodes are the two points at which the orbit of an ETNO, or any other celestial body, crosses the plane of the Solar System. These are the precise points where the probability of interacting with other objects is the largest, and therefore, at these points, the ETNOs may experience a drastic change in their orbits or even a collision.
Like the comets that interact with Jupiter
"If there is nothing to perturb them, the nodes of these extreme trans-Neptunian objects should be uniformly distributed, as there is nothing for them to avoid, but if there are one or more perturbers, two situations may arise," explains Carlos de la Fuente Marcos, one of the authors. "One possibility is that the ETNOs are stable, and in this case they would tend to have their nodes away from the path of possible perturbers, he adds, but if they are unstable they would behave as the comets that interact with Jupiter do, that is tending to have one of the nodes close to the orbit of the hypothetical perturber."
Using calculations and data mining, the Spanish astronomers have found that the nodes of the 28 ETNOs analysed (and the 24 extreme Centaurs with average distances from the Sun of more than 150 AU) are clustered in certain ranges of distances from the Sun; furthermore, they have found a correlation, where none should exist, between the positions of the nodes and the inclination, one of the parameters which defines the orientation of the orbits of these icy objects in space.
"Assuming that the ETNOs are dynamically similar to the comets that interact with Jupiter, we interpret these results as signs of the presence of a planet that is actively interacting with them in a range of distances from 300 to 400 AU," says De la Fuente Marcos, who emphasizes: "We believe that what we are seeing here cannot be attributed to the presence of observational bias."
Until now, studies that challenged the existence of Planet Nine using the data available for these trans-Neptunian objects argued that there had been systematic errors linked to the orientations of the orbits (defined by three angles), due to the way in which the observations had been made. Nevertheless, the nodal distances mainly depend on the size and shape of the orbit, parameters which are relatively free of observational bias.
"It is the first time that the nodes have been used to try to understand the dynamics of the ETNOs," the co-author points out, as he admits that discovering more ETNOs (at the moment, only 28 are known) would permit the proposed scenario to be confirmed and subsequently constrain the orbit of the unknown planet via the analysis of the distribution of the nodes.
The authors note that their study supports the existence of a planetary object within the range of parameters considered both in the Planet Nine hypothesis of Mike Brown and Konstantin Batygin from Caltech, and in the original one proposed in 2014 by Scott Sheppard from the Carnegie Institute and Chadwick Trujillo from the University of North Arizona; in addition to following the lines of their own earlier studies (the latest led by the Instituto de Astrofísica de Canarias), which suggested that there is more than one unknown planet in our Solar System.
Is there also a Planet Ten?
De la Fuente Marcos explains that the hypothetical Planet Nine suggested in this study has nothing to do with another possible planet or planetoid situated much closer to us, and hinted at by other recent findings. Also applying data mining to the orbits of the TNOs of the Kuiper Belt, astronomers Kathryn Volk and Renu Malhotra from the University of Arizona (USA) have found that the plane on which these objects orbit the Sun is slightly warped, a fact that could be explained if there is a perturber of the size of Mars at 60 AU from the Sun.
The giant storm on Jupiter known as the Great Red Spot has been raging for centuries. Now scientists may finally be on the verge of attaining greater insight into this tempest.
Images and data are being returned to Earth from the Juno spacecraft’s recent close pass over the GRS on Monday, July 10, when it passed directly above the coiling crimson cloud tops at a height of just 5,600 miles (9,000 kilometers). The spacecraft's eight instruments gathered data, including its citizen science-based imager, JunoCam. As soon as the raw images hit the JunoCam website, amateur image processing gurus pounced into action.
The images — the closest ever taken of the GRS — weren’t expected to be available until July 14 because the spacecraft’s main antenna was pointed away from Earth during the closest approach. But they arrived earlier that expected on Wednesday.
“The Juno team must have fast-tracked them!” enthused amateur image processor Kevin Gill, who works as a science data software engineer at NASA's Jet Propulsion Laboratory.
The science team knows there has been avid public interest in Juno’s seventh science flyby over Jupiter’s cloud tops that focused on the GRS.
"This monumental storm has raged on the solar system's biggest planet for centuries,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “Now, Juno and her cloud-penetrating science instruments will dive in to see how deep the roots of this storm go, and help us understand how this giant storm works and what makes it so special."
It will likely take weeks or perhaps months for the science team to analyze the data gathered by Juno’s instruments in order to reveal some of the enduring storm’s secrets. But JunoCam images processed by amateurs can be seen here.
“We made JunoCam an instrument that belongs to the public,” Juno’s Project Scientist Steve Levin told me last year. “We solicit the aid of the public in picking which areas to look at and making the maps that go in to the images and processing the data, and releasing the data to the world. We release it in the rawest form we can, and allow the public to make the images.”
The JunoCam images captured three different views of the GRS. One that looks at the northern edge, one centered as Juno fly right over the GRS, and one looking from the south. The third one also included data with a methane filter.
While the images are stunning, it will be the other instruments that will reveal the most insights into the GRS, the storm that is twice as big as Earth.
While astronomers have actively monitored the GRS since the early 1800s, and other spacecraft such as Voyager in the late 1970s and Galileo in the 1990s, "there’s still a lot of mystery surrounding this massive storm," said Bolton.
Questions abound, such as why is the storm red? Why has it endured for so long, and why has it been shrinking over the past several years?
This is what dawn on Saturn looks like, from afar.
The ringed planet is partly hidden in darkness and partly illuminated by the faint light of a distant sun in a gorgeous photo taken by NASA's Cassini spacecraft.
"The light has traveled around 80 minutes since it left the sun's surface by the time it reaches Saturn," NASA officials wrote in a description of the image, which was released yesterday (July 10). "The illumination it provides is feeble; Earth gets 100 times the intensity, since it's roughly 10 times closer to the sun. Yet compared to the deep blackness of space, everything at Saturn still shines bright in the sunlight, be it direct or reflected."[Cassini's Saturn 'Grand Finale' Plan in Pictures]
Cassini took the photo on Feb. 25, at a distance of about 762,000 miles (1.23 million kilometers) from the ringed planet.
The $3.2 billion Cassini-Huygens mission — a joint effort of NASA, the European Space Agency, and the Italian Space Agency — has been orbiting Saturn since July 2004, but its days are numbered: The spacecraft is scheduled to plunge into the gas giant's cloud tops on Sept. 15, in an intentional death dive designed to ensure that Cassini doesn't contaminate the Saturn moons Titan or Enceladus with microbes from Earth. (Both Titan and Enceladus may be capable of supporting life, scientists have said.)
Huygens was a piggyback lander that separated from the Cassini mothership and made a historic touchdown on Titan in January 2005 — the first soft touchdown ever achieved on a body in the outer solar system.
This is an artist’s impression of a young star surrounded by a
protoplanetary disk in which planets (not shown to scale) are forming.
A new model giving rise to young planetary systems offers a fresh solution to a puzzle that has vexed astronomers ever since new detection technologies and planet-hunting missions such as NASA's Kepler space telescope have revealed thousands of planets orbiting other stars: While the majority of these exoplanets fall into a category called super-Earths -- bodies with a mass somewhere between Earth and Neptune -- most of the features observed in nascent planetary systems were thought to require much more massive planets, rivaling or dwarfing Jupiter, the gas giant in our solar system.
In other words, the observed features of many planetary systems in their early stages of formation did not seem to match the type of exoplanets that make up the bulk of the planetary population in our galaxy.
"We propose a scenario that was previously deemed impossible: how a super-Earth can carve out multiple gaps in disks," says Ruobing Dong, the Bart J. Bok postdoctoral fellow at the University of Arizona's Steward Observatory and lead author on the study, soon to be published in the Astrophysical Journal. "For the first time, we can reconcile the mysterious disk features we observe and the population of planets most commonly found in our galaxy."
How exactly planets form is still an open question with a number of outstanding problems, according to Dong.
"Kepler has found thousands of planets, but those are all very old, orbiting around stars a few billion years old, like our sun," he explains. "You could say we are looking at the senior citizens of our galaxy, but we don't know how they were born."
To find answers, astronomers turn to the places where new planets are currently forming: protoplanetary disks -- in a sense, baby sisters of our solar system.
Such disks form when a vast cloud of interstellar gas and dust condenses under the effect of gravity before collapsing into a swirling disk. At the center of the protoplanetary disk shines a young star, only a few million years old. As microscopic dust particles coalesce to sand grains, and sand grains stick together to form pebbles, and pebbles pile up to become asteroids and ultimately planets, a planetary system much like our solar system is born.
"These disks are very short-lived," Dong explains. "Over time the material dissipates, but we don't know exactly how that happens. What we do know is that we see disks around stars that are 1 million years old, but we don't see them around stars that are 10 million years old."
In the most likely scenario, much of the disk's material gets accreted onto the star, some is blown away by stellar radiation and the rest goes into forming planets.
Although protoplanetary disks have been observed in relative proximity to the Earth, it is still extremely difficult to make out any planets that may be forming within. Rather, researchers have relied on features such as gaps and rings to infer the presence of planets.
"Among the explanations for these rings and gaps, those involving planets certainly are the most exciting and drawing the most attention," says co-author Shengtai Li, a research scientist at Los Alamos National Laboratory in Los Alamos, New Mexico. "As the planet orbits around the star, the argument goes, it may clear a path along its orbit, resulting in the gap we see."
Except that reality is a bit more complicated, as evidenced by two of the most prominent observations of protoplanetary disks, which were made with ALMA, the Atacama Large Millimeter/submillimeter Array in Chile. ALMA is an assembly of radio antennas between 7 and 12 meters in diameter and numbering 66 of them once completed. The images of HL Tau and TW Hydra, obtained in 2014 and 2016, respectively, have revealed the finest details so far in any protoplanetary disk, and they show some features that are difficult, if not impossible, to explain with current models of planetary formation, Dong says.
"Among the gaps in HL Tau and TW Hya revealed by ALMA, two pairs of them are extremely narrow and very close to each other," he explains. "In conventional theory, it is difficult for a planet to open such gaps in a disk. They can never be this narrow and this close to each other for reasons of the physics involved."
In the case of HL Tau and TW Hya, one would have to invoke two planets whose orbits hug each other very closely -- a scenario that would not be stable over time and therefore is unlikely.
While previous models could explain large, single gaps believed to be indicative of planets clearing debris and dust in their path, they failed to account for the more intricate features revealed by the ALMA observations.
The model created by Dong and his co-authors results in what the team calls synthetic observations -- simulations that look exactly like what ALMA would see on the sky. Dong's team accomplished this by tweaking the parameters going into the simulation of the evolving protoplanetary disk, such as assuming a low viscosity and adding the dust to the mix. Most previous simulations were based on higher disk viscosity and accounted only for the disk's gaseous component.
"The viscosity in protoplanetary disks may be driven by turbulence and other physical effects," Li says. "It's a somewhat mysterious quantity -- we know it's there, but we don't know its origin or how large its value is, so we think our assumptions are reasonable, considering that they result in the pattern that has actually been observed on the sky."
Even more important, the synthetic observations emerged from the simulations without the necessity to invoke gas giants the size of Jupiter or larger.
"One super-Earth turned out to be sufficient to create the multiple rings and multiple, narrow gaps we see in the actual observations," Dong says.
The icy gas world that strangely orbits the sun on its side may also have a wonky magnetic field that constantly flickers on and off, new research suggests.
Magnetic fields around planets, or magnetospheres, create shields against the bombardment of radiation from the sun known as solar wind. On Earth, for example, the magnetosphere lines up pretty closely with the planet's axis of rotation, and magnetic field lines emerge from Earth's north and south poles. On Uranus, however, the magnetosphere is a bit more chaotic.
Uranus' spin axis is tilted by a whopping 98 degrees, and the planet's off-center magnetic field is tilted by another 60 degrees. Every time the planet rotates (about every 17.24 hours), this lopsided magnetic field tumbles around, opening and closing periodically as the magnetic field lines disconnect and reconnect, the study found.
Researchers at the Georgia Institute of Technology (Georgia Tech) in Atlanta figured this out by simulating Uranus' messy magnetosphere using numerical models and data from NASA's Voyager 2 spacecraft, which flew by the planet in 1986.
"Uranus is a geometric nightmare," Carol Paty, an associate professor at Georgia Tech's School of Earth & Atmospheric Sciences and co-author of the study, said in a statement. "The magnetic field tumbles very fast, like a child cartwheeling down a hill head over heels. When the magnetized solar wind meets this tumbling field in the right way, it can reconnect, and [so] Uranus' magnetosphere goes from open to closed to open on a daily basis."
When the magnetosphere opens up, it allows solar particles to bombard the planet. Then, when the magnetic field lines reconnect, this natural shield can continue to block the solar wind.
This process may be related to auroras on Uranus. Just like the auroras on Earth and other planets, Uranus' atmosphere lights up when particles from the solar wind enter it and interact with gases like nitrogen and oxygen.
NASA's Hubble Space Telescope has previously observed auroras on Uranus, but astronomers face difficulties in studying how these auroras interact with the magnetosphere, because the planet is so far away — nearly 2 billion miles (3.2 billion kilometers) from Earth. The space agency is currently considering sending another spacecraft to Uranus and Neptune to investigate those planet's magnetic fields, among other things.
Xin Cao, a Ph.D. candidate at Georgia Tech who led the study, said that studying Uranus can teach scientists a lot about planets outside of the solar system. "The majority of exoplanets [worlds outside the solar system] that have been discovered appear to also be ice giants in size," he said. "Perhaps what we see on Uranus and Neptune is the norm for planets: very unique magnetospheres and less-aligned magnetic fields.
Deforestation along the Jari River, a northern tributary of the Amazon river, Brazil, May 2014
On June 24, 2012, Lonesome George, the last of the Pinta Island tortoises, died quietly in his pen at a research facility in the Galapagos.
The island where his species once flourished had been ravaged by a flock of goats introduced to the island by fishermen in 1959 as a source of fresh meat for their voyages. The goats devastated the island’s vegetation, wiping out the Pinta tortoises’ habitat.
You may not have heard of Lonesome George. But his death was a sign of our times.
Two vertebrate species go extinct every year amid a man-made mass extinction unrivaled since the dinosaurs died out 66 million years ago. Today, the phenomenon is known as the Sixth Extinction. Some 200 species have disappeared over the past century — a pace approximately 100 times faster than the “normal” rate.
At the turn of the millennium, Nobel prize winning atmospheric chemist Paul Crutzen and his colleague Eugene Stoermer published an article suggesting that humans had altered Earth so much that the planet should be thought to have entered a new geological epoch, which they dubbed the Anthropocene, or “Age of Humans.” The 11,700-year-old Holocene, which began at end of the most recent ice age and extended through the rise of modern human civilization, should be considered over, they argued.
Now, new research from scientists at the Universidad Nacional Autónoma de México and Stanford University provides a fresh picture of the size and scale of the threat facing the planet’s biodiversity at the hands of humanity.
“Earth’s sixth mass extinction is more severe than perceived,” constituting a “biological annihilation” that translates into a “frightening assault on the foundations of human civilization,” the study says.
The rate of loss of different types of species — two per year — doesn’t take into account the fact that surviving species are declining dramatically both in terms of their population numbers and in the geographical range over which they can be found, the authors write.
The scientists used geographical range as a proxy for population sizes, and looked at 27,600 vertebrate species, with an even more detailed analysis of 177 mammals between the years 1900 and 2015.
All of the 177 mammals lost 30 percent or more of their geographic ranges, according to the study, which was published in the Proceedings of the National Academy of Sciences. More than 40 percent of the species experienced severe range decline of over 80 percent.
The declining number of animals on earth “is already damaging the services ecosystems provide to civilization,” the authors wrote.
To be sure, not all dire warnings about the future of the planet pan out. One of the three authors of this very paper, Paul Erhlich, professor of population studies of the Department of Biology of Stanford University, famously predicted in his controversial 1968 book, "The Population Bomb," that overpopulation would lead to mass starvation and social upheaval in the 1970s and 1980s.
When the famous 15th-century inventor and scientist Leonardo da Vinci examined petrified shells with borings in them long ago, he had a remarkable insight. The strange fossilized formations, he determined, were likely left behind by ancient organisms.
Half a millennium later, this perspective is potentially useful in our search for alien life, argues a new paper that appears in Earth-Science Reviews, whose findings were recently presented at the European Astrobiology Network Association congress in the Netherlands.
Astronomers have been weighing options for how to identify the existence of life on other planets and moons in our solar system. There are a range of possibilities. Mars could be host to ancient or current life, depending on how much water flows on the surface and how salty it is. There are also many icy moons (some with water geysers) in the outer regions of our solar system — among them Saturn’s Titan and Enceladus, and Jupiter’s Europa and Ganymede.
“Leonardo understood the biological nature of borings based on their shape, not their biochemistry,” said Andrea Baucon, the lead researcher. Baucon is an ichnologist, a type of scientist that studies life’s traces through burrows, borings and trails. He previously studied da Vinci’s work and is a researcher at the University of Modena and UNESCO Geopark Naturtejo.
“This observation appears to be trivial,” he went on, “but it potentially allows [us] to detect extra-terrestrial life that differs from known life.”
A major limitation of this kind of study, however, is that animal traces and alterations by geology can sometimes appear very similar. For example, researchers have identified what they say are more than four-billion-year-old fossils in formations in northern Quebec, Canada. This finding was announced earlier this year; in 2016, a separate team claimed to find 3.7-billion-year-old microbial mats in Greenland.
But given that the Earth is about 4.5 billion years old, critics of these discoveries argue, the changes in Earth’s geology over billions of years can sometimes mimic the appearances of lifeforms. Microbiologists therefore need to prove that the older lifeforms did indeed exist by comparing the older fossils to much younger and better-verified examples of life. Researchers must also attempt to verify markings by life against the chemistry in the rocks, although again this can be altered by rock deformation over time.
Baucon is a member of ROSAE, an Italian acronym that in English stands for Organism-Sediment Relationships in Extreme Environments. It’s a scientific project that looks at how organisms and sediments interact in so-called “extreme environments,” such as the deep sea.
In this latest study, Baucon and his colleagues attempt to explain the best way to find extra-terrestrial traces. One method could be looking for “meandering” trails and burrows, which is an efficient way for microorganisms to look for food. Rather than making straight lines in an environment or repeatedly crossing a surface, the meandering allows a creature to search for food without exerting too much energy.
