Feb 24, 2017
The diameter of its lens or mirror, the so-called aperture, fundamentally limits any telescope. In simple terms, the bigger the mirror or lens, the more light it gathers, allowing astronomers to detect fainter objects, and to observe them more clearly. A statistical concept known as 'Nyquist sampling theorem' describes the resolution limit, and hence how much detail can be seen.
The Swiss study, led by Prof Kevin Schawinski of ETH Zurich, uses the latest in machine learning technology to challenge this limit. They teach a neural network, a computational approach that simulates the neurons in a brain, what galaxies look like, and then ask it to automatically recover a blurred image and turn it into a sharp one. Just like a human, the neural net needs examples - in this case a blurred and a sharp image of the same galaxy - to learn the technique.
Their system uses two neural nets competing with each other, an emerging approach popular with the machine learning research community called a "generative adversarial network", or GAN. The whole teaching programme took just a few hours on a high performance computer.
The trained neural nets were able to recognise and reconstruct features that the telescope could not resolve - such as star-forming regions, bars and dust lanes in galaxies. The scientists checked it against the original high-resolution image to test its performance, finding it better able to recover features than anything used to date, including the 'deconvolution' approach used to improve the images made in the early years of the Hubble Space Telescope.
Schawinski sees this as a big step forward: "We can start by going back to sky surveys made with telescopes over many years, see more detail than ever before, and for example learn more about the structure of galaxies. There is no reason why we can't then apply this technique to the deepest images from Hubble, and the coming James Webb Space Telescope, to learn more about the earliest structures in the Universe."
Professor Ce Zhang, the collaborator from computer science, also sees great potential: "The massive amount of astronomical data is always fascinating to computer scientists. But, when techniques such as machine learning emerge, astrophysics also provides a great test bed for tackling a fundamental computational question - how do we integrate and take advantage of the knowledge that humans have accumulated over thousands of years, using a machine learning system? We hope our collaboration with Kevin can also shed light on this question."
Read more at Science Daily
The finding, published Feb. 23, 2017 in the journal Nature, is important because it provides the first hard proof for what scientists call the "chaotic solar system," a theory proposed in 1989 to account for small variations in the present conditions of the solar system. The variations, playing out over many millions of years, produce big changes in our planet's climate -- changes that can be reflected in the rocks that record Earth's history.
The discovery promises not only a better understanding of the mechanics of the solar system, but also a more precise measuring stick for geologic time. Moreover, it offers a better understanding of the link between orbital variations and climate change over geologic time scales.
Using evidence from alternating layers of limestone and shale laid down over millions of years in a shallow North American seaway at the time dinosaurs held sway on Earth, the team led by UW-Madison Professor of Geoscience Stephen Meyers and Northwestern University Professor of Earth and Planetary Sciences Brad Sageman discovered the 87 million-year-old signature of a "resonance transition" between Mars and Earth. A resonance transition is the consequence of the "butterfly effect" in chaos theory. It plays on the idea that small changes in the initial conditions of a nonlinear system can have large effects over time.
In the context of the solar system, the phenomenon occurs when two orbiting bodies periodically tug at one another, as occurs when a planet in its track around the sun passes in relative proximity to another planet in its own orbit. These small but regular ticks in a planet's orbit can exert big changes on the location and orientation of a planet on its axis relative to the sun and, accordingly, change the amount of solar radiation a planet receives over a given area. Where and how much solar radiation a planet gets is a key driver of climate.
"The impact of astronomical cycles on climate can be quite large," explains Meyers, noting as an example the pacing of Earth's ice ages, which have been reliably matched to periodic changes in the shape of Earth's orbit, and the tilt of our planet on its axis. "Astronomical theory permits a very detailed evaluation of past climate events that may provide an analog for future climate."
To find the signature of a resonance transition, Meyers, Sageman and UW-Madison graduate student Chao Ma, whose dissertation work this comprises, looked to the geologic record in what is known as the Niobrara Formation in Colorado. The formation was laid down layer by layer over tens of millions of years as sediment was deposited on the bottom of a vast seaway known as the Cretaceous Western Interior Seaway. The shallow ocean stretched from what is now the Arctic Ocean to the Gulf of Mexico, separating the eastern and western portions of North America.
"The Niobrara Formation exhibits pronounced rhythmic rock layering due to changes in the relative abundance of clay and calcium carbonate," notes Meyers, an authority on astrochronology, which utilizes astronomical cycles to measure geologic time. "The source of the clay (laid down as shale) is from weathering of the land surface and the influx of clay to the seaway via rivers. The source of the calcium carbonate (limestone) is the shells of organisms, mostly microscopic, that lived in the water column."
Meyers explains that while the link between climate change and sedimentation can be complex, the basic idea is simple: "Climate change influences the relative delivery of clay versus calcium carbonate, recording the astronomical signal in the process. For example, imagine a very warm and wet climate state that pumps clay into the seaway via rivers, producing a clay-rich rock or shale, alternating with a drier and cooler climate state which pumps less clay into the seaway and produces a calcium carbonate-rich rock or limestone."
The new study was supported by grants from the National Science Foundation. It builds on a meticulous stratigraphic record and important astrochronologic studies of the Niobrara Formation, the latter conducted in the dissertation work of Robert Locklair, a former student of Sageman's at Northwestern.
Dating of the Mars-Earth resonance transition found by Ma, Meyers and Sageman was confirmed by radioisotopic dating, a method for dating the absolute ages of rocks using known rates of radioactive decay of elements in the rocks. In recent years, major advances in the accuracy and precision of radioisotopic dating, devised by UW-Madison geoscience Professor Bradley Singer and others, have been introduced and contribute to the dating of the resonance transition.
The motions of the planets around the sun has been a subject of deep scientific interest since the advent of the heliocentric theory -- the idea that Earth and planets revolve around the sun -- in the 16th century. From the 18th century, the dominant view of the solar system was that the planets orbited the sun like clockwork, having quasiperiodic and highly predictable orbits. In 1988, however, numerical calculations of the outer planets showed Pluto's orbit to be "chaotic" and the idea of a chaotic solar system was proposed in 1989 by astronomer Jacques Laskar, now at the Paris Observatory.
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|Gem quality diamond from Letlhakane, containing multiple orange garnets.|
'Although a jeweller would consider diamonds with lots of inclusions to be flawed, for a geologist these are the most valuable and exciting specimens,' said Prof Gareth Davies, of Vrije Universiteit (VU) Amsterdam, who co-authored the study. 'We can use the inclusions to date different parts of an individual diamond, and that allows us to potentially look at how the processes that formed diamonds may have changed over time and how this may be related to the changing carbon cycle on Earth.'
Sixteen diamonds from two mines in north eastern Botswana were analysed in the study: seven specimens from the Orapa mine and nine from the Letlhakane mine. A team at VU Amsterdam measured the radioisotope, nitrogen and trace element contents of inclusions within the diamonds. Although the mines are located just 40 kilometres apart, the diamonds from the two sources had significant differences in the age range and chemical composition of inclusions.
The Orapa diamonds contained material dating from between around 400 million and more than 1.4 billion years ago. The Letlhakane diamond inclusions ranged from less than 700 million and up to 2-2.5 billion years old. In every case, the team were able to link the age and composition of material in the inclusions to distinct tectonic events occurring locally in the Earth's crust, such as a collision between plates, continental rifting or magmatism. This suggests that diamond formation is triggered by heat fluctuations and magma fluid movement associated with these events.
The Letlhakane diamonds also provided a rare opportunity to look back in time to the early Earth. The oldest inclusions date back to before the Great Oxidation Event (GOE) around 2.3 billion years ago, when oxygen produced by multicellular cyanobacteria started to fill the atmosphere, radically changing the weathering and sediment formation processes and thus altering the chemistry of rocks.
Read more at Science Daily
|Sunrise at Lagoa Santa, Minas Gerais, Brazil.|
The many differences in cranial morphology, the study of skull shape, seen in Paleoamerican remains found in the Lagoa Santa region of Brazil suggest a model of human history that included multiple waves of population dispersals from Asia, across the Bering Strait, down the North American coast and into South America.
The findings published Wednesday (Feb. 22, 2017) in the journal Science Advances suggest that Paleoamericans share a last common ancestor with modern native South Americans outside, rather than inside, the Americas and underscore the importance of looking at both genetic and morphological evidence, each revealing different aspects of the human story, to help unravel our species' history.
"When you look at contemporary genomic data, the suggestion, particularly for South America, was for one wave of migration and that indigenous South American people are all descendants of that wave," says Noreen von Cramon-Taubadel, an associate professor of anthropology at the University at Buffalo and the paper's lead author. "But our data is suggesting that there were at least two, if not more, waves of people entering South America."
How people settled the Americas is a debate that has continued for years in the scientific community. It's now clear that the first human entry into the Americas began at least 15,000 years ago and dispersed quickly into South America following a coastal Pacific route.
The conundrum of conflicting data between morphology and genetics is among the issues fueling the debate of how people first entered the New World, but von Cramon-Taubadel's conclusions are similar to previous morphological research while also relying on a pioneering method to reach those conclusions.
"We've adopted and modified the method from ecology, but to my knowledge this method has never been used in an anthropological setting before," she says.
In the past, researchers have looked mainly at the overall similarities between the morphology of prehistoric skeletons from the Americas compared with the morphology of living people. Models of dispersal, each with a different number of waves that attempt to match existing data, have also been used.
But von Cramon-Taubadel's current research with Mark Hubbe, an associate professor in the Department of Anthropology at Ohio State University, and University of Tübingen researcher André Strauss, doesn't make any previous assumptions about dispersals. It looks at an existing population as descendants of many possible branches of a theoretical tree of relatedness and then uses statistics to determine where in the tree their sample best fits.
This method has the advantage of not needing pre-determined models of dispersal but rather considers all possible patterns of relatedness.
All living people, von Cramon-Taubadel explains, have a common ancestor, but not all fossils necessarily contribute to the ancestry of living people. Some populations of modern humans did not survive or made only a marginal contribution to living people. So fossils of these extinct humans provide few clues about the ancestry of living people.
Read more at Science Daily
Feb 23, 2017
|These are mounds of the cathedral termite Nasutitermes triodiae at Litchfield National Park.|
Referred to as "cathedral" termites, the Nasutitermes triodiae build huge mounds up to eight metres high in the Northern Territory, Western Australia and Queensland -- representing some of the tallest non-human animal structures in the world.
DNA sequencing found the forebearers, called nasute termites, colonised Australia three times in the past 20 million years or so and evolved from wood to grass-feeding as they adapted to significant environmental changes, including increasingly arid conditions and the conversion of woodlands to grassland habitats in subtropical savannahs and central Australia.
Now a prominent feature of the arid landscape "Down Under," the mounds house millions of termites; this study is the first comprehensive investigation of the evolution of the nesting and feeding of the extended family of termites, through the Australian refugee descendants.
The findings of the international research are published in the Royal Society journal Biology Letters.
Co-lead author of the paper from the University of Sydney, Associate Professor Nathan Lo, said although much was known about the functions of termite mounds -- which include protection from predators -- little had been known about their evolutionary origins.
"We found that the ancestors of Australia's fortress-building termites were coastal tree-dwellers, which arrived in Australia by rafting long distances over the oceans from either Asia or South America," Associate Professor Lo said.
"Once in Australia, they continued to build their nests in trees, but later descended and began building mounds on the ground instead, paralleling the evolution of the other great architects of the world -- human beings, whose ancestors lived in the tree tops some millions of years ago."
Associate Professor Lo, from the University of Sydney's School of Life and Environmental Sciences, said the mounds are an engineering feat when considered in comparison to the tallest structure on Earth -- Dubai's skyscraper the Burj Khalifas.
"Given that a worker termite stands about 3mm in height, these mounds are in human terms the equivalent of four Burj Khalifas stacked on top of each other," he said.
The paper, "Parallel evolution of mound-building and grass-feeding in Australian nasute termites," said ancestral wood feeders would likely have lost the ability to feed on wood as they transitioned to feeding on litter and grass.
Read more at Science Daily
|Pyritized trilobite specimens (Triarthrus eatoni) are from the Ordovician Whetstone Gulf Formation (Lorraine Group), upstate New York (USA).|
Like other exceptionally preserved trilobites from the Lorraine Group, the complete exoskeletons are replaced with pyrite. The eggs are spherical to elliptical in shape and nearly 200 micrometers in size.
The location of the eggs is consistent with where modern female horseshoe crabs release their unfertilized eggs from the ovarian network within their head. Trilobites likely released their eggs and sperm through a genital pore of as-yet-unknown location (but probably near the posterior boundary of the head).
Because pyrite preferentially preserves the external features of fossils, there is probably a bias in the fossil record toward the preservation of arthropods that brood eggs externally. If the reproductive biology of these trilobites is representative of other trilobites, they likely spawned with external fertilization as well, which may be the ancestral mode of reproduction for early arthropods.
From Science Daily
|The foot bones of the new giant penguin (left), compared to those of an Emperor Penguin, the largest living penguin species (right).|
The fossil sites along the Waipara River in New Zealand's Canterbury region are well known for their avian fossils, which were embedded in marine sand a mere 4 million years after the dinosaurs became extinct. "Among the finds from these sites, the skeletons of Waimanu, the oldest known penguin to date, are of particular importance," explains Dr. Gerald Mayr of the Senckenberg Research Institute in Frankfurt.
Together with colleagues from the Canterbury Museum in New Zealand, Mayr now described a newly discovered penguin fossil from the famous fossil site. "What sets this fossil apart are the obvious differences compared to the previously known penguin remains from this period of geological history," explains the ornithologist from Frankfurt, and he continues, "The leg bones we examined show that during its lifetime, the newly described penguin was significantly larger than its already described relatives. Moreover, it belongs to a species that is more closely related to penguins from later time periods."
According to the researchers, the newly described penguin lived about 61 million years ago and reached a body length of approx. 150 centimeters -- making it almost as big as Anthropornis nordenskjoeldi, the largest known fossil penguin, which lived in Antarctica around 45 to 33 million years ago, thus being much younger in geological terms. "This shows that penguins reached an enormous size quite early in their evolutionary history, around 60 million years ago," adds Mayr.
In addition, the team of scientists from New Zealand and Germany assumes that the newly discovered penguin species also differed from their more primitive relatives in the genus Waimanu in their mode of locomotion: The large penguins presumably already moved with the upright, waddling gait characteristic for today's penguins.
Read more at Science Daily
The formation of sedimentary dunes requires the presence of grains and of winds that are strong enough to transport them along the ground. However, comets do not have a dense, permanent atmosphere as on Earth. Nonetheless, the OSIRIS camera on board the Rosetta spacecraft showed the presence of dune-like forms approximately ten meters apart on 67P/Churyumov-Gerasimenko. They are found on the lobes of the comet as well as on the neck that connects them. Comparison of two images of the same spot taken 16 months apart provides evidence that the dunes moved and are therefore active.
Faced with this unexpected finding, the researchers show that there is in fact a wind blowing along the comet's surface. It is caused by the pressure difference between the sunlit side, where the surface ice can sublimate due to the energy provided by the sunlight, and the night side. This transient atmosphere is still extremely tenuous, with a maximum pressure at perihelion, when the comet is closest to the Sun, 100,000 times lower than on Earth. However, gravity on the comet is also very weak, and an analysis of the forces exerted on the grains at the comet's surface shows that these thermal winds can transport centimeter-scale grains, whose presence has been confirmed by images of the ground. The conditions required to allow the formation of dunes, namely winds able to transport the grains along the ground, are thus met on Chury's surface.
This work represents a step forward in understanding the various processes at work on cometary surfaces. It also shows that the Rosetta mission still has many surprises and discoveries in store.
From Science Daily
|This is Vedran Jelic, PhD student at the University of Alberta and lead author on a new paper pioneering microscopy at terahertz frequencies.|
"We can essentially zoom in to observe very fast processes with atomic precision and over super fast time scales," says Vedran Jelic, PhD student at the University of Alberta and lead author on the new study. "THz-STM provides us with a new window into the nanoworld, allowing us to explore ultrafast processes on the atomic scale. We're talking a picosecond, or a millionth millionth of a second. It's something that's never been done before."
Jelic and his collaborators used their scanning tunneling microscope (STM) to capture images of silicon atoms by raster scanning a very sharp tip across the surface and recording the tip height as it follows the atomic corrugations of the surface. While the original STM can measure and manipulate single atoms -- for which its creators earned a Nobel Prize in 1986 -- it does so using wired electronics and is ultimately limited in speed and thus time resolution.
Modern lasers produce very short light pulses that can measure a whole range of ultra-fast processes, but typically over length scales limited by the wavelength of light at hundreds of nanometers. Much effort has been expended to overcome the challenges of combining ultra-fast lasers with ultra-small microscopy. The University of Alberta scientists addressed these challenges by working in a unique terahertz frequency range of the electromagnetic spectrum that allows wireless implementation. Normally the STM needs an applied voltage in order to operate, but Jelic and his collaborators are able to drive their microscope using pulses of light instead. These pulses occur over really fast timescales, which means the microscope is able to see really fast events.
By incorporating the THz-STM into an ultrahigh vacuum chamber, free from any external contamination or vibration, they are able to accurately position their tip and maintain a perfectly clean surface while imaging ultrafast dynamics of atoms on surfaces. Their next step is to collaborate with fellow material scientists and image a variety of new surfaces on the nanoscale that may one day revolutionize the speed and efficiency of current technology, ranging from solar cells to computer processing.
Read more at Science Daily
Feb 22, 2017
Six marine biodiversity hotspots in the Atlantic, Indian and Pacific Oceans are being severely impacted by climate change and overfishing, according to the paper published in Science Advances.
"We have critical areas, where you have a long-term anomaly in the environment and those areas are also of high biodiversity," said André Chiaradia, a penguin biologist and one of the study's co-authors. "In some cases these places have extra pressure from commercial fisheries."
The study is the first to overlap global species distribution in oceans with marine areas most at risk from climate change and aimed to identify areas of marine conservation priority around the globe.
In order to do so, researchers compiled a database of 2,183 marine animals and more than three decades worth of information on sea surface temperatures, ocean currents and marine productivity.
They also evaluated industrial fishing data from the Food and Agriculture Organization from the last 60 years.
The environmental data showed an uneven distribution of changes to the Earth's oceans between 1979 and 2014, with the most striking shifts at the poles and the tropics.
Due to global warming, scientists found significant changes to water temperatures, current circulation and nutrient availability.
As the global average temperature has increased, the majority of extra heat has been absorbed by the oceans, leading to changes in the ocean's density, or stratification, the study said.
Increased stratification prevents water and nutrients mixing, which can hamper primary production that forms the basis of the food chain.
Water from melting ice sheets and glaciers, meanwhile, can influence the behavior of ocean currents, changing the marine ecosystem.
To get an idea about how these environmental changes could impact marine life, the researchers identified six marine biodiversity hotspots, all concentrated in the Southern Hemisphere.
They included the Pacific waters off Peru and the Galápagos Islands, stretches of the Atlantic Ocean around Argentina and Uruguay, the coastline stretching from South Africa to Kenya, the central western Pacific Ocean, the waters around New Zealand and eastern and southern Australia, and marine areas in Oceania and the central Pacific Ocean.
|Global distribution of marine biodiversity with colors indicating the number of species — red indicating areas with the highest biodiversity.|
"We knew about the fishery impact and high biodiversity. But guess what? These areas have seen a lot of environmental change as well," Chiaradia said.
Although it is unclear on what scale environmental stressors will impact these hotspots, it is unlikely to be beneficial in most cases, according to the study.
Warming oceans may affect production of nutrients essential for bigger animals, while changes to ocean currents could affect food availability.
Combined with the impacts of overfishing, which the authors said had decimated about 70 percent of world fish stocks since World War II, biodiversity hotspots will be put under even greater pressure in the future.
"Accordingly, climate and fishing impacts should not be treated in isolation from each other when it comes to conservation of marine biodiversity," the authors argue.
Read more at Discovery News