вторник, 25 сентября 2018 г.

Narrowing down the mass of the Milky Way

Since the birth of modern astronomy, scientists have sought to determine the full extent of the Milky Way galaxy and learn more about its structure, formation and evolution. At present, astronomers estimate that it is 100,000 to 180,000 light-years in diameter and consists of 100 to 400 billion stars – though some estimates say there could be as many as 1 trillion.











Narrowing down the mass of the Milky Way
Credit: NASA

And yet, even after decades of research and observations, there is still much about our galaxy astronomers do not know. For example, they are still trying to determine how massive the Milky Way is, and estimates vary widely. In a new study, a team of international scientists presents a new method for weighing the galaxy based the dynamics of the Milky Way’s satellites galaxies.


The study, titled “The mass of the Milky Way from satellite dynamics,” recently appeared in the Monthly Notices of the Royal Astronomical Society. The study was led by Thomas Callingham from the University of Durham’s Institute of Computational Cosmology, and included members from the Massachusetts Institute of Technology (MIT), the Heidelberg Institute for Theoretical Studies, and multiple universities.


As they indicate in their study, the mass of the Milky Way is fundamental to our understanding of astrophysics. Not only is it important in terms of placing our galaxy into the context of the general galaxy population, but it also plays a major role when addressing some of the greatest mysteries that arise from our current astrophysical and cosmological theories.


These include the intricacies of galaxy formation, discrepancies with the current Lambda Cold Dark Matter (Lambda CDM) model, alternative theories on the nature of dark matter, and the large-scale structure of the universe. What’s more, previous studies have been hampered by a number of factors, which include the fact that the Milky Way’s dark matter halo (which makes up most of its mass) cannot be observed directly.











Narrowing down the mass of the Milky Way
Artist’s impression of the Milky Way Galaxy [Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)]

Another major issue is the fact that it is difficult to measure the extent and mass of the Milky Way because we are within it. As a result, previous studies that have attempted to infer the mass of our galaxy resulted in mass estimates ranging from about 500 billion to 2.5 trillion times the mass of our sun (solar masses). As Callingham explained to universe Today via email, refined approach was needed:


“The majority of the galaxy is in its dark matter halo, which cannot be directly observed. Instead, we infer its properties through observations of various dynamical tracers that feel the gravitational effects of the dark matter – such as stellar populations, globular clusters, steams and satellite galaxies. Most of these lie at the center of a our galaxy in the the galactic disc ( within ~10kpc) and the stellar halo (~15kpc) which can give good mass estimates of the inner region. However the DM halo reaches ~200kpc, and for this reason we chose to focus on satellite galaxies, as one of the only tracers that probe these outer parts of the galaxy.”


For the sake of their study, the team relied on data from the Gaia satellite’s second data release (DR2 release) to place better constraints on the Milky Way’s mass. The Gaia mission, which has provided more information than ever before about our galaxy, includes the position and relative motions of countless stars in the Milky Way – including those that are in satellite galaxies. As Callingham indicated, this proved very useful for constraining the mass of the Milky Way:


“We compare the orbital properties Energy and Angular Momentum of the MWs satellite galaxies to those found in simulations. We used the latest observations of the MWs satellites from the recent Gaia DR2 dataset and a sample of suitable galaxies and satellite galaxies from the EAGLE simulations, a leading simulation ran in Durham with a large volume and full hydrodynamical baryonic physics.”











Narrowing down the mass of the Milky Way
The Gaia mission’s first sky map [Credit: ESA/Gaia/DPAC/A. Moitinho & M. Barros,
CENTRA – University of Lisbon]

The EAGLE software (Evolution and Assembly of GaLaxies and their Environments), which was developed by Durham University’s Institute of Computational Cosmology, models the formation of structures in a cosmological volume measuring 100 Megaparsecs on a side (over 300 million light-years). However, using this software to infer the mass of the Milky Way presented some challenges.


“A challenge to this is the limited sample of MW size galaxies in EAGLE (or indeed any simulation),” said Callingham. “To help this we use a mass scaling relation to scale our total sample of galaxies to be the same mass. This allows us to effectively use more from our dataset and greatly improves our statistics. Our method was then rigorously tested by finding the mass of simulated galaxies from EAGLE and the Auriga simulations – an independent suite of high resolution simulations. This ensures that our mass estimate is robust and has realistic errors (something the field sometimes struggles with due to analytic assumptions).”


From this, they found that the total halo mass of the Milky Way was about 1.04 x 1012 (over 1 trillion) solar masses, with a 20 percent margin of error. This estimate places much tighter constraints on the Milky Way’s mass than previous estimates, and could have some significant implications in the fields of astronomy, astrophysics and cosmology. As Callingham summarized:


“A tighter mass estimate can be used in many ways. In galaxy modelling, the DM halo is the backdrop on which stellar components are fit. Many methods to probe the nature of DM, such as the structure of the DM halo, as well as the density of DM on Earth for direct detection purposes depend on the mass of the MW. The mass can also be used to predict the number of satellite galaxies around the MW that we expect.”











Narrowing down the mass of the Milky Way
All galaxies are thought to have a dark matter halo. This image shows the distribution of dark matter
surrounding our very own Milky Way [Credit: J. Diemand, M. Kuhlen and P. Madau (UCSC)]

In addition to providing astronomers with refined measurements of the Milky Way’s mass – which will go a long way towards informing our understanding of its size, extent, and satellite galaxy population – this study also has implications for our understanding of the universe as a whole. What’s more, it is yet another groundbreaking study that was made possible through Gaia’s second data release.


The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).


Author: Matt Williams | Source: Universe Today [September 21, 2018]



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Land-based bird populations are at risk of local extinction

Land-based bird populations are becoming confined to nature reserves in some parts of the world — raising the risk of global extinction — due to the loss of suitable habitat, according to a report led by UCL.











Land-based bird populations are at risk of local extinction
Credit: University College London

Researchers analysed biodiversity in the area known as Sundaland, which covers the peninsula of Thailand, Borneo, Malaysia, Sumatra, Java and Bali, one of the world’s most biologically degraded regions.


The study, published in Conservation Letters, focuses on galliformes — heavy-bodied ground-feeding birds such as pheasants, grouse and quail — as their numbers are well-recorded and they are amongst the most threatened species in some parts of the world.


Scientists found that up to 13 populations (25 per cent of galliform populations in the area) have been extirpated (made locally extinct) in the region and no longer exist outside nature reserves (protected areas). The island of Sumatra has suffered the highest proportion of extirpations among the areas studied, having lost 50 percent of its galliform species in unprotected land.


As a result, certain species are only found in protected areas — raising questions about the ultimate goal of conservation. The researchers argue that these areas were never intended to be a last resort for the existence of species and are also coming under increasing threat from human activity.


Professor Elizabeth Boakes (UCL Life Sciences) said: “Land outside of protected areas is increasingly being lost to agriculture and infrastructure, leading to species becoming confined to Sundaland’s protected areas. Biodiversity in the unprotected landscape is required to maintain connectivity and ecosystem function.


“It is also critical that protected areas are managed effectively. However, nearly 20 per cent of Malaysia’s and over 40 per cent of Indonesia’s protected land is subject to intense human pressure.


“As one of the most biologically degraded areas, Sundaland offers a stark warning to the rest of the world should global rates of land conversion continue unabated. Conservation’s end goal is not islands of biodiversity, marooned in a sea of destruction. More land must be managed in a way that accommodates biodiversity for the long term.”


Sundaland is a biological hotspot, meaning it is rich in biodiversity but at risk of destruction. Despite the existence of protected areas, forest cover in Sumatra declined by five per cent between 1990 and 2000, while Kalimantan’s protected lowland forests declined by more than 56 per cent between 1985 and 2001.


In addition to this, protected areas are not necessarily permanent, with downgrading over the last few years equating to a loss of 8360km² of protected land. As they become more isolated in agricultural landscapes or by the spread of roads and other infrastructure, species lose the opportunity to track and adapt to climate change.


An example of this is that just 12 per cent of Borneo’s protected areas are topographically diverse enough to allow species to survive a high warming scenario.


Dr Philip McGowan, Newcastle University School of Natural and Environmental Sciences and Chair of IUCN Species Survival Commission Task Force on post 2020 biodiversity targets said: “These findings present new insights into how we should view protected areas and their ability to conserve species across landscapes.


“At a time when there is debate about how much land should be given over to protected areas, it is how they are integrated into global biodiversity targets that is perhaps critical. These targets are currently being reviewed by the Convention on Biological Diversity, which is also discussing what should follow them when they expire in 2020.”


Southeast Asia’s deforestation rate is the highest among tropical regions, above five per cent annually in parts of Sumatra and Sarawak. Sundaland’s lowland forests are rapidly disappearing, giving us an insight into the future global conservation status of the remainder of the world if land outside of protected areas continues to be lost, putting the reserves at increased risk from climate change and human activity.


Source: University College London [September 21, 2018]



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Subducting slabs of the Earth’s crust may generate unusual features spotted near...

Nearly 1,800 miles below the earth’s surface, there are large odd structures lurking at the base of the mantle, sitting just above the core. The mantle is a thick layer of hot, mostly plastic rock that surrounds the core; atop the mantle is the thin shell of the earth’s crust. On geologic time scales, the mantle behaves like a viscous liquid, with solid elements sinking and rising through its depths.











Subducting slabs of the Earth's crust may generate unusual features spotted near the core
The diamond anvil in which samples of magnesiowüstite were placed under
extreme pressure and studied [Credit: Jennifer Jackson/Caltech]

The aforementioned odd structures, known as ultra-low velocity zones (ULVZs), were first discovered in 1995 by Caltech’s Don Helmberger. ULVZs can be studied by measuring how they alter the seismic waves that pass through them. But observing is not necessarily understanding. Indeed, no one is really sure what these structures are.


ULVZs are so-named because they significantly slow down the speeds of seismic waves; for example, they slow down shear waves (oscillating seismic waves capable of moving through solid bodies) by as much as 30 percent. ULVZs are several miles thick and can be hundreds of miles across. Several are scattered near the earth’s core roughly beneath the Pacific Rim. Others are clustered underneath North America, Europe, and Africa.


“ULVZs exist so deep in the inner earth that they are impossible to study directly, which poses a significant challenge when trying to determine what exactly they are,” says Helmberger, Smits Family Professor of Geophysics, Emeritus.


Earth scientists at Caltech now say they know not just what ULVZs are made of, but where they come from. Using experimental methods at high pressures, the researchers, led by Professor of Mineral Physics Jennifer Jackson, have found that ULVZs consist of chunks of a magnesium/iron oxide mineral called magnesiowüstite that could have precipitated out of a magma ocean that is thought to have existed at the base of the mantle millions of years ago.


The other leading theory for ULVZs formation had suggested that they consist of melted material, some of it possibly leaking up from the core.


Jackson and her colleagues, who reported on their work in a recent paper in the Journal of Geophysical Research: Solid Earth, found evidence supporting the magnesiowüstite theory by studying the mineral’s elastic (or seismic) anisotropy; elastic anisotropy is a variation in the speed at which seismic waves pass through a mineral depending on their direction of travel.











Subducting slabs of the Earth's crust may generate unusual features spotted near the core
Cross-section illustration shows slabs of the earth’s crust descending through
the mantle and aligning magnesiowüstite in ultra-low velocity zones
[Credit: California Institute of Technology]

One particularly unusual characteristic of the region where ULVZs exist—the core-mantle boundary (CMB)—is that it is highly heterogenous (nonuniform in character) as well as anisotropic. As a result, the speed at which seismic waves travel through the CMB varies based not only on the region that the waves are passing through but on the direction in which those waves are moving. The propagation direction, in fact, can alter the speed of the waves by a factor of three.


“Previously, scientists explained the anisotropy as the result of seismic waves passing through a dense silicate material. What we’re suggesting is that in some regions, it is largely due to the alignment of magnesiowüstite within ULVZs,” says Jackson.


At the pressures and temperatures experienced at the earth’s surface, magnesiowüstite exhibits little anisotropy. However, Jackson and her team found that the mineral becomes strongly anisotropic when subjected to pressures comparable to those found in the lower mantle.


Jackson and her colleagues discovered this by placing a single crystal of magnesiowüstite in a diamond anvil cell, which is essentially a tiny chamber located between two diamonds. When the rigid diamonds are compressed against one another, the pressure inside the chamber rises. Jackson and her colleagues then bombarded the sample with x-rays. The interaction of the x-rays with the sample acts as a proxy for how seismic waves will travel through the material. At a pressure of 40 gigapascals—equivalent to the pressure at the lower mantle—magnesiowüstite was significantly more anisotropic than seismic observations of ULVZs.


In order to create objects as large and strongly anisotropic as ULVZs, only a small amount of magnesiowüstite crystals need to be aligned in one specific direction, probably due to the application of pressure from a strong outside force. This could be explained by a subducting slab of the earth’s crust pushing its way to the CMB, Jackson says. (Subduction occurs at certain boundaries between earth’s tectonic plates, where one plate dives below another, triggering volcanism and earthquakes.)


“Scientists are still in the process of discovering what happens to the crust when it’s subducted into the mantle,” Jackson says. “One possibility, which our research now seems to support, is that these slabs push all the way down to the core-mantle boundary and help to shape ULVZs.”


Next, Jackson plans to explore the interaction of subducting slabs, ULVZs, and their seismic signatures. Interpreting these features will help place constraints on processes that happened early in Earth’s history, she says.


Author: Robert Perkins | Source: California Institute of Technology [September 21, 2018]



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The first predators and their self-repairing teeth

The earliest predators appeared on Earth 480 million years ago — and they even had teeth which were capable of repairing themselves. A team of palaeontologists led by Bryan Shirley and Madleen Grohganz from the Chair for Palaeoenviromental Research at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have been able to discover more about how these organisms were able to grow and regenerate their teeth. The results have now been published in Proceedings of the Royal Society B.











The first predators and their self-repairing teeth
Image of a conodont’s tooth [Credit: FAU/Bryan Shirley]

In a land before time: A fast-moving predator with sharp teeth goes hunting in the prehistoric sea. It spies some prey and advances stealthily. All of a sudden, it goes in for the kill and devours its prey. Some of the predator’s teeth have broken, but they will grow back.
This is not the description of some prehistoric monster from a horror film, but rather of a conodont. Although these eel-like vertebrates were only a few centimetres long, they are considered the Earth’s very first predators. Their small teeth, which are known as elements and are among the most important microfossils, could repair themselves after being damaged.


How exactly this happened is difficult to ascertain, as although the fossilised teeth are often found in marine rock, their soft tissue is only rarely preserved. Since only a few examples of soft tissue from conodonts have survived, it is very difficult to determine how they grew.


Microscopes and X-rays provide insight


Analyses carried out by FAU researchers are now shedding more light on the subject. By using scanning electron microscopes, the scientists examined the various layers of conodonts’ teeth to learn more about how they grew.


During this process, a material is bombarded with electrons. Different materials reflect a different number of electrons back to the microscope. For example, heavy elements reflect electrons more strongly than lighter ones, which is why they are shown in a lighter colour on the image. This method enabled the individual layers to be reproduced and investigated at a much higher resolution than before.


By using X-ray spectroscopy where elements are detected by means of the the radiation they emit, the scientists were also able to analyse the chemical composition of each layer.


Three stages of growth


The teeth grew in cycles, which is shown in the alternating cycle between wear and growth of new layers. Furthermore, the shape of the teeth varied greatly depending on the animals’ stage of growth.


Using the chemical composition and the shape of the teeth, the researchers were able to identify three stages of growth during the development of an animal that were influenced (amongst others) by feeding habits.


After the first stage, a type of larval state, in which food was not digested mechanically (by chewing), conodonts evolved into the first hunters during the second and third stages of growth. During this time, their teeth underwent a metamorphosis — the transition to being predators.


Existing hypothesis has been corroborated


Up to now, there have been two models to explain how conodont teeth were able to regenerate themselves. In contrast to human teeth, for example, that grow from the inside out, conodonts’ teeth repaired themselves from the outside where new layers were continuously added.


One theory put forward by scientists is that conodonts retracted their teeth during periods of rest and growth occurred by the apposition of new layers in epidermal pockets. This could be compared to the mechanism of retractable teeth used for injecting venom by some species of snake.


On the other hand, a theory exists that the teeth were permanently enveloped by tissue and a type of horn cap, allowing new layers to build up over time. The research carried out by FAU scientists has now confirmed the first theory.


Source: University of Erlangen-Nuremberg [September 22, 2018]




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Chinese Cretaceous fossil highlights avian evolution

A newly identified extinct bird species from a 127 million-year-old fossil deposit in northeastern China provides new information about avian development during the early evolution of flight.











Chinese Cretaceous fossil highlights avian evolution
A 127-million-year-old fossil bird, Jinguofortis perplexus (reconstruction on the right, artwork by Chung-Tat Cheung),
second earliest member of the short-tailed birds Pygostylia [Credit: WANG Min]

Drs. Wang Min, Thomas Stidham, and Zhou Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences reported their study of the well-preserved complete skeleton and feathers of this early bird in the Proceedings of the National Academy of Sciences.
The analysis of this early Cretaceous fossil shows it is from a pivotal point in the evolution of flight—after birds lost their long bony tail, but before they evolved a fan of flight feathers on their shortened tail.


The scientists named this extinct species Jinguofortis perplexus. The genus name “Jinguofortis” honors women scientists around the world. It derives from the Chinese word “jinguo,” meaning female warrior, and the Latin word “fortis” meaning brave.











Chinese Cretaceous fossil highlights avian evolution
Major changes of the coracoid and scapula (main components of the shoulder girdle) across the major vertebrate
groups; the right is a simplified cladogram shows the phylogeny of Mesozoic birds with highlights
of the changes of the shoulder and hand [Credit: WANG Min]

Jinguofortis perplexus has a unique combination of traits, including a jaw with small teeth like its theropod dinosaur relatives; a short bony tail ending in a compound bone called a pygostyle; gizzard stones showing that it mostly ate plants; and a third finger with only two bones, unlike other early birds.
The fossil’s shoulder joint also gives clues about its flight capacity. In flying birds, the shoulder, which experiences high stress during flight, is a tight joint between unfused bones. In contrast, Jinguofortis perplexus preserves a shoulder girdle where the major bones of the shoulder, the shoulder blade (scapula) and the coracoid, are fused to one another, forming a scapulocoracoid.


The existence of a fused shoulder girdle in this short-tailed fossil suggests evolutionary variety during this stage of evolution, which probably resulted in different styles of flight.Based on its skeleton and feathers, Jinguofortis perplexus probably flew a bit differently than birds do today.


Measurement of the fossil’s wing size and estimation of its body mass show that the extinct species had a wing shape and wing loading (wing area divided by body mass) similar to living


Source: Chinese Academy of Sciences [September 24, 2018]



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Violence in pre-Columbian Panama exaggerated, new study shows

Buried alive. Butchered. Decapitated. Hacked. Mutilated. Killed. Archaeologist Samuel K. Lothrop did not obfuscate when describing what he thought had happened to the 220 bodies his expedition excavated from Panama’s Playa Venado site in 1951. The only problem is that Lothrop likely got it wrong. A new evaluation of the site’s remains by Smithsonian archaeologists revealed no signs of trauma at or near time of death. The burial site likely tells a more culturally nuanced story.











Violence in pre-Columbian Panama exaggerated, new study shows
One of two cases of healed blows to the cranium from the Playa Venado excavations. Most of the evidence of violence
 was interpreted by Harvard archaeologist, Samuel Lothrop based on body positioning in graves at the site.
Smithsonian post-doctoral fellow, Nicole Smith-Guzmán, found no examples of trauma that occurred
 near the time of death among the skeletons in the collection [Credit: Nicole Smith-Guzmán, STRI]

The “long-overdue” reexamination of the Playa Venado site, which dates to 500-900 A.D. and is located near the Pacific entrance to the Panama Canal, revealed no evidence of ritual killing, said Nicole E. Smith-Guzmán, post-doctoral fellow at the Smithsonian Tropical Research Institute (STRI). Lothrop’s misinterpretations are likely due to the era of “Romantic archaeology,” underdeveloped methods for mortuary studies and literal readings of Spanish accounts of indigenous peoples after European contact.
“We now realize that many of these Spanish chroniclers were motivated to show the indigenous populations they encountered as ‘uncivilized’ and in need of conquering,” said Smith-Guzmán, adding that many accounts of sacrifice and cannibalism have not been confirmed by the archaeological record. “Rather than an example of violent death and careless deposition, Playa Venado presents an example of how pre-Columbian societies in the Isthmo-Colombian area showed respect and care for their kin after death.”


The article, co-authored by STRI staff archaeologist Richard Cooke, was published in Latin American Antiquity. But Lothrop’s 1954 paper, “Suicide, sacrifice and mutilations in burials at Venado Beach, Panama,” left its mark on the annals of Panamanian archaeology. It has been cited more than 35 times as evidence of violence, cannibalism or trophy decapitation. Some authors have used the paper to suggest Playa Venado is a mass burial site or a manifestation of conflict.











Violence in pre-Columbian Panama exaggerated, new study shows
A female skeleton in situ with a ceramic pedestal bowl in the shape of a turtle at her head. Amateur archaeologist
Kenneth Vinton kept this ceramic artifact and there were several photos of it on display
in his classroom in Panama [Credit: Ripon College, Kenneth Vinton estate]

In defense of Lothrop, who was an archaeologist with Harvard University’s Peabody Museum of Archaeology and Enthnology, bioarchaeology (the study of human remains from archaeological contexts) did not exist as a sub-discipline until two decades after his work concluded at Playa Venado. Today’s practitioners also benefit from methods developed in the 1980s and 1990s.
Lothrop’s careful documentation and preservation of remains made reevaluation possible. Remains from more than 70 individuals from Playa Venado are at the Smithsonian’s National Museum of Natural History, sent there by Lothrop for osteological evaluation.


Upon examination, Smith-Guzmán found only wounds that showed signs of healing well before the individuals died, including blows to the head and a dislocated thumb. Various broken bones and disarticulated remains discovered by Lothrop more likely explained by normal processes of decomposition and secondary burial of remains, which is believed to have a common ancestor-veneration practice in pre-Colombian Panama.











Violence in pre-Columbian Panama exaggerated, new study shows
Overhead: Bioarchaeologist Nicole Smith-Guzmán looks for clues that might explain the cause of death
of individuals from ancient Panamanian gravesites [Credit: Sean Mattson, STRI]

Evidence suggests certain people’s remains were preserved for long periods of time before being buried in ritual contexts. “At Playa Venado, we see a lot of evidence of adults being buried next to urns containing children, multiple burials including one primary and one secondary burial, and disturbance of previously laid graves in order to inter another individual in association,” said Smith-Guzmán.
“The uniform burial positioning and the absence of perimortem (around the time of death) trauma stands in contradiction to Lothrop’s interpretation of violent death at the site,” said Smith-Guzmán, who also used evidence from other archaeological sites around Panama about burial rites as part of the investigation. “There are low rates of trauma in general, and the open mouths of skeletons Lothrop noted are more easily explained by normal muscle relaxation after death and decay.”


Smith-Guzmán and Cooke’s reassessment of the Playa Venado burials suggests that ideas about widespread violence in pre-Columbian Panama need to be reconsidered. The research is part of a larger, interdisciplinary site reanalysis that will be published by the Dumbarton Oaks Museum in Washington, D.C..


Source: Smithsonian Tropical Research Institute [September 24, 2018]



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AmtDB: an interactive ancient human mitogenome database

A very useful new resource called AmtDB has just come online. For background info, check out the relevant paper by Ehler et al. here. Below is the paper abstract:



Ancient mitochondrial DNA is used for tracing human past demographic events due to its population-level variability. The number of published ancient mitochondrial genomes has increased in recent years, alongside with the development of high-throughput sequencing and capture enrichment methods. Here, we present AmtDB, the first database of ancient human mitochondrial genomes. Release version contains 1107 hand-curated ancient samples, freely accessible for download, together with the individual descriptors, including geographic location, radiocarbon dating, and archaeological culture affiliation. The database also features an interactive map for sample location visualization. AmtDB is a key platform for ancient population genetic studies and is available at https://amtdb.org.



To give an example of how this thing works, I’ll search for a very specific mitochondrial (mtDNA) haplogroup, H6a1b, which was recorded, perhaps unexpectedly, in a sample from Hittite era Anatolia (individual MA2208 from Damgaard et al. 2018). I say perhaps unexpectedly, because it’s a marker that is today, by and large, restricted to Northern Europe. Here are the results…



Interestingly, H6a1b only pops up in Copper and Bronze Age individuals from what are now Czechia, Great Britain, Poland and Russia, with not a single instance from the Near East. Moreover, the oldest sample on the list is from an Yamnaya culture burial in Samara, Russia. Thus, if the presence of this marker in the Hittite sample isn’t due to contamination or poor quality sequencing, then it’s likely that some Hittites belonged to mtDNA haplogroups that arrived in Anatolia from the steppes of what is now Russia.
See also…
Focus on Hittite Anatolia

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Secrets of Secretion Responsible for causing tuberculosis, a…


Secrets of Secretion


Responsible for causing tuberculosis, a disease affecting millions of people worldwide, Mycobacterium tuberculosis can infect macrophages, immune cells which normally engulf and destroy pathogens. Critical to the bacterium’s success is a sophisticated secretion system, enabling it to transport useful compounds into host cells. Multiple proteins make up this system but their specific roles are difficult to disentangle, so researchers are investigating them in a closely-related pathogen, Mycobacterium marinum, causing tuberculosis in fish. They found especially intriguing results for one protein, named EspH. While bacteria lacking EspH were less effective at infecting macrophages in the lab, they were very virulent when infecting zebrafish larvae, forming aggregates inside and around zebrafish blood vessels, a phenomenon known as cording (pictured, with bacteria in red, blood vessels in green and macrophages in blue).This suggests that host factors interact with the bacterium’s own proteins, adding another layer of complexity to the processes behind tuberculosis infections.


Written by Emmanuelle Briolat



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Spotlight on sea-level rise


ESA – European Space Agency patch.


25 September 2018


Scientists are gathering in the Azores this week to share findings on how satellite has revealed changes in the height of the sea, ice, inland bodies of water and more. Of concern to all is the fact that global sea level has not only been rising steadily over the last 25 years, but recently it is rising at a much fast rate.


The 25 Years of Progress in Radar Altimetry Symposium gives participants the opportunity to share information gained from this particular sort of satellite instrument.



Regional sea-level trends

Radar altimeters record the surface topography along the satellite’s ground track. They precisely measure the height of water, land and ice by timing the interval between the transmission and reception of very short radar pulses.


This is the only technology that can measure, systematically and globally, changes in the height of the ocean – and is therefore essential for monitoring sea-level rise.


The 25-year record of altimetry data allows scientists to determine trends. For example, between 1993 and 2018 the global ocean rose 3.2 mm every year, on average.


But, altimetry measurements also reveal that the over the last five years the global ocean has risen, on average, 4.8 mm a year.


Anny Cazenave from the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales said, “Satellite altimeters are an essential tool for monitoring sea-level rise. We use reference missions such as the CNES–NASA series of Jason satellites along with other missions such as the Copernicus Sentinel-3 mission to gather a time series of data to understand how sea level is changing in the long term.



Satellite altimeters

“This information shows that sea level has been rising at an average rate of about 3 mm a year since these records began in 1993. However, recent re-analysis of our records has shown that sea-level rise is accelerating because of global warming.”


ESA’s Jérôme Benveniste added, “With many millions living in coastal communities around the world, sea-level rise is a major concern. The information we get from satellite altimeters is essential for understanding how fast our seas are rising so that decision-makers are equipped to take appropriate mitigating action.


“At this week’s symposium we are not only looking back over the last 25 years of satellite altimetry, but we are also looking to the future as we have the Copernicus Sentinel-6 mission in development and also a number of candidate satellite missions being studied.


“It is vital that we have satellite altimeters in the future to continue this long-term record of change.”


While trends and averages are important, it is equally important to understand regional differences. In some places the height of the sea is rising and in other places it is falling.



Causes of sea-level rise

There are a number of reasons for this. For example, when seawater warms it also expands, leading to a phenomenon called thermal expansion.


Although thermal expansion is the biggest cause of sea-level rise as a consequence of climate change, there are many local differences. These differences can be caused by events such as El Niño, for example.



Sea-level rise



Ice loss from the continental glaciers and from the polar ice sheets is also one of the most critical drivers of our rising seas. Ice loss from glaciers, Greenland and Antarctica accounts for about 45% of sea-level rise.


Another cause is discharge from waterbodies on land, but how much this contributes to sea-level rise is more uncertain.


As the symposium progresses, other scientific findings and discussions on the future will be discussed.


Observing the Earth: http://www.esa.int/Our_Activities/Observing_the_Earth


Earth System Science Data:


Global sea-level budget 1993–present: https://www.earth-syst-sci-data.net/10/1551/2018/essd-10-1551-2018.pdf


Related links


Climate Change Initiative – Sea Level: http://www.esa-sealevel-cci.org/


CNES: https://cnes.fr/en


CNES–Satellite Altimetry Data: https://www.aviso.altimetry.fr/en/home.html


Eumetsat: http://www.eumetsat.int/Home/index.htm


NASA: https://www.nasa.gov/


NOAA: https://www.noaa.gov/


Related missions:


Topex-Poseidon: https://sealevel.jpl.nasa.gov/missions/topex/


Jason-1 & Jason-2: https://jason.cnes.fr/en/JASON2/index.htm


Jason-3: https://sealevel.jpl.nasa.gov/missions/jason3/


ERS: http://www.esa.int/Our_Activities/Observing_the_Earth/ERS_overview


Envisat: http://www.esa.int/Our_Activities/Observing_the_Earth/Envisat


CryoSat: http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat


Sentinel-3: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-3


Images, Video, Text, Credits: ESA/CNES/LEGOS/CLS/EU Copernicus Marine Service/contains modified Copernicus Sentinel data (2018).


Greetings, Orbiter.chArchive link


ESA choosing CubeSat companions for Hera asteroid mission


European Space Agency (ESA) logo.


25 September 2018


As the world marvels at the hopping mini-rovers deployed on asteroid Ryugu by Japan’s Hayabusa2, ESA is due to decide on the CubeSats planned for delivery to a binary asteroid system by its proposed Hera mission.


CubeSats are nanosatellites based on standardised 10 cm-sized units. This week an ESA evaluation board decides which two ‘6-unit’ CubeSat missions will ride with the next-decade Hera mission to the Didymos asteroid system. The CubeSats will be deployed around the smaller of the two bodies for eventual landing.



Hera and CubeSats

Landing in a low-gravity environment is a rare event – more akin to a docking than a traditional touchdown – so the Hera team has been following Hayabusa2’s deployment closely. Famously the Philae lander of ESA’s Rosetta mission bounced off the surface of Comet 67P/Churyumov–Gerasimenko during its 2014 landing, coming down in a shady spot that drained its solar arrays and limited its lifetime.


The MINERVA mini-lander accompanying Japan’s Hayabusa-1 to asteroid Itokawa was lost in space in 2005 when Itokawa’s gravity failed to bring it down. The two MINERVA-II mini-rovers deployed last week are designed to hop across Ryugu’s surface because traditional wheeled motion would cast them up into space again.


The MINERVA-II mini-rovers weigh in at about 1.1 kg each, compared to Philae’s 100 kg. Hayabusa2 is planned to deliver a larger 10kg Mascot lander on 3 October – built by the DLR German Aerospace Center, responsible for Philae, in cooperation with the French space agency CNES – which will similarly be able to hop. By comparison Hera’s 6-unit CubeSats will be intermediate in size, around 6 kg each.



Mini-rover hop

“The CubeSats we are selecting have a different operating concept, intended to fly close above their asteroid with their own propulsion systems,” explains ESA space scientist and Rosetta veteran Michael Küppers, today serving as Hera project scientist.


“At just 160 m across, the smaller component of the Didymos binary asteroid is too small to truly orbit around, but instead these CubeSats will fly Rosetta-like hyperbolic arcs, maintained by manoeuvres every few days, hopefully culminating in landings.


Hera is planned to be humankind’s first mission to a binary asteroid system, with multiple goals. As well as testing technologies in deep space and gathering bonus science, Hera would also be Europe’s contribution to an international planetary defence effort: it would survey the crater and other effects on the asteroid – plus its resulting orbital deviation – due to the collision of a NASA probe, called DART.



Hera surveying DART crater

‘It’s extremely helpful scientifically when asteroid missions get to touch the surface of their target,” comments CNRS Director of Research Patrick Michel of France’s Côte d’Azur Observatory. As well as serving as a co-investigator and interdisciplinary scientist on Hayabusa2’s science team he is also Hera’s lead scientist.


“With Hera this will already have been done by the DART impact: we’ll have a crater for which we have the initial conditions of its formation, offering us a documented impact experiment at actual asteroid scale. This will enable us to assess the effectiveness of asteroid deflection as a planetary defence technique and allow us to infer many things about collisions more generally and their fundamental role in all the stages of the history of the Solar System.



Hera networking with CubeSats

“In addition Hera’s CubeSats will give us additional close-up views and information, risking much closer approaches than their parent spacecraft before eventually landing.”


“The two proposals chosen to move to definition stage this week would be Europe’s first CubeSats to fly beyond Earth orbit,” explains Hera manager Ian Carnelli.



Hera mission

“CubeSats give an excellent opportunity for some Member States to oversee deep space missions for the first time. Hera’s CubeSats will let us investigate a novel intersatellite communications link technology and gather invaluable low gravity operational experience by flying very close to a small body, as well as crucial planetary defence findings and bonus science data.”


The two winning CubeSats will be announced later this week.


Related links:


ESA’s Hera mission: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Hera


ESA’s comet chaser Rosetta: http://www.esa.int/Our_Activities/Space_Science/Rosetta


JAXA’s Hayabusa2: http://www.hayabusa2.jaxa.jp/en/


Images, Animation, Video, Text, Credits: ESA/ScienceOffice.org/JAXA.


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10 Steps to Confirm a Planet Around Another Star


So you think you found an exoplanet – a planet around another star? It’s not as simple as pointing a telescope to the sky and looking for a planet that waves back. Scientists gather many observations and carefully analyze their data before they can be even somewhat sure that they’ve discovered new worlds.


Here are 10 things to know about finding and confirming exoplanets.


image



This is an illustration of the different elements in our exoplanet program, including ground-based observatories, like the W. M. Keck Observatory, and space-based observatories like Hubble, Spitzer, Kepler, TESS, James Webb Space Telescope, WFIRST and future missions.



1. Pick your tool to take a look.


The vast majority of planets around other stars have been found through the transit method so far. This technique involves monitoring the amount of light that a star gives off over time, and looking for dips in brightness that may indicate an orbiting planet passing in front of the star.


We have two specialized exoplanet-hunting telescopes scanning the sky for new planets right now – Kepler and the Transiting Exoplanet Survey Satellite (TESS) – and they both work this way. Other methods of finding exoplanets include radial velocity (looking for a “wobble” in a star’s position caused by a planet’s gravity), direct imaging (blocking the light of the star to see the planet) and microlensing (watching for events where a star passes in front of another star, and the gravity of the first star acts as a lens).


Here’s more about finding exoplanets.


image

2. Get the data.


To find a planet, scientists need to get data from telescopes, whether those telescopes are in space or on the ground. But telescopes don’t capture photos of planets with nametags. Instead, telescopes designed for the transit method show us how brightly thousands of stars are shining over time. TESS, which launched in April and just began collecting science data, beams its stellar observations back to Earth through our Deep Space Network, and then scientists get to work.


image

3. Scan the data for planets.


Researchers combing through TESS data are looking for those transit events that could indicate planets around other stars. If the star’s light lessens by the same amount on a regular basis – for example, every 10 days – this may indicate a planet with an orbital period (or “year”) of 10 days. The standard requirement for planet candidates from TESS is at least two transits – that is, two equal dips in brightness from the same star.


image

4. Make sure the planet signature couldn’t be something else.


Not all dips in a star’s brightness are caused by transiting planets. There may be another object – such as a companion star, a group of asteroids, a cloud of dust or a failed star called a brown dwarf, that makes a regular trip around the target star. There could also be something funky going on with the telescope’s behavior, how it delivered the data, or other “artifacts” in data that just aren’t planets. Scientists must rule out all non-planet options to the best of their ability before moving forward.


image

5. Follow up with a second detection method.


Finding the same planet candidate using two different techniques is a strong sign that the planet exists, and is the standard for “confirming” a planet. That’s why a vast network of ground-based telescopes will be looking for the same planet candidates that TESS discovers. It is also possible that TESS will spot a planet candidate already detected by another telescope in the past. With these combined observations, the planet could then be confirmed. The first planet TESS discovered, Pi Mensae c, orbits a star previously observed with the radial-velocity method on the ground. Scientists compared the TESS data and the radial-velocity data from that star to confirm the presence of planet “c.”


Scientists using the radial-velocity detection method see a star’s wobble caused by a planet’s gravity, and can rule out other kinds of objects such as companion stars. Radial-velocity detection also allows scientists to calculate the mass of the planet.


image

6. …or at least another telescope.


Other space telescopes may also be used to help confirm exoplanets, characterize them and even discover additional planets around the same stars. If the planet is detected by the same method, but by two different telescopes, and has received enough scrutiny that the scientists are more than 99 percent sure it’s a planet, it is said to be “validated” instead of “confirmed.”


image

7. Write a paper.


After thoroughly analyzing the data, and running tests to make sure that their result still looks like the signature of a planet, scientists write a formal paper describing their findings. Using the transit method, they can also report the size of the planet. The planet’s radius is related to how much light it blocks from the star, as well as the size of the star itself. The scientists then submit the study to a journal.


image

8. Wait for peer review.


Scientific journals have a rigorous peer review process. This means scientific experts not involved in the study review it and make sure the findings look sound. The peer-reviewers may have questions or suggestions for the scientists. When everyone agrees on a version of the study, it gets published.



9. Publish the study.


When the study is published, scientists can officially say they have found a new planet. This may still not be the end of the story, however. For example, the TRAPPIST telescope in Chile first thought they had discovered three Earth-size planets in the TRAPPIST-1 system. When our Spitzer Space Telescope and other ground-based telescopes followed up, they found that one of the original reported planets (the original TRAPPIST-1d) did not exist, but they discovered five others –bringing the total up to seven wondrous rocky worlds.


image

10. Catalog and celebrate – and look closer if you can!


Confirmed planets get added to our official catalog. So far, Kepler has sent back the biggest bounty of confirmed exoplanets of any telescope – more than 2,600 to date. TESS, which just began its planet search, is expected to discover many thousands more. Ground-based follow-up will help determine if these planets are gaseous or rocky, and possibly more about their atmospheres. The forthcoming James Webb Space Telescope will be able to take a deeper look at the atmospheres of the most interesting TESS discoveries.


Scientists sometimes even uncover planets with the help of people like you: exoplanet K2-138 was discovered through citizen scientists in Kepler’s K2 mission data. Based on surveys so far, scientists calculate that almost every star in the Milky Way should have at least one planet. That makes billions more, waiting to be found! Stay up to date with our latest discoveries using this exoplanet counter.



Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.


2018 September 25 Highlights of the North Autumn Sky…


2018 September 25


Highlights of the North Autumn Sky
Illustration Credit & Copyright: Universe2go.com


Explanation: What can you see in the night sky this season? The featured graphic gives a few highlights for Earth’s northern hemisphere. Viewed as a clock face centered at the bottom, early (northern) autumn sky events fan out toward the left, while late autumn events are projected toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center – although almost everything pictured can be seen without a telescope. As happens during any season, constellations appear the same year to year, and, as usual, the Leonids meteor shower will peak in mid-November. Also as usual, the International Space Station (ISS) can be seen, at times, as a bright spot drifting across the sky after sunset. Planets visible after sunset this autumn include Jupiter and Mars, and during late autumn, Saturn.


∞ Source: apod.nasa.gov/apod/ap180925.html


Stones Monolith 1, Stones Farm, Todmorden, Yorkshire, 24.9.18.A first visit to this...







Stones Monolith 1, Stones Farm, Todmorden, Yorkshire, 24.9.18.


A first visit to this complex for me and what a location! Massive stones located on windswept farmlands and moorlands. Extensively re-erected and now with a millstone base.


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Japan Delivery Due Thursday as Trio Preps Russian Spacecraft for Return


ISS – Expedition 56 Mission patch.


September 24, 2018


A Japanese cargo craft is orbiting Earth today and on its way to resupply the International Space Station. Meanwhile, the six Expedition 56 crew members are researching a variety of space phenomena as a trio prepares to return to Earth.


JAXA’s (Japan Aerospace Exploration Agency) resupply ship launched Saturday from Japan loaded with over five tons of new science and supplies destined for the crew. The H-II Transfer Vehicle-7 (HTV-7) is scheduled to arrive at the space station on Thursday. Flight Engineer Serena Auñón-Chancellor will be in the cupola backing up Commander Drew Feustel when he captures the HTV-7 with the Canadarm2 around 8 a.m. on Thursday.



Image above: Two docked Russian spacecraft are seen as the International Space Station orbited nearly 262 miles above New Zealand. Image Credit: NASA.


Included among the critical payloads packed inside the HTV-7 is the Life Sciences Glovebox. The new facility will enable research to advance human health on Earth and in space. HTV-7 is also delivering new lithium-ion batteries to upgrade power systems on the station’s truss structure. NASA TV begins its live coverage of the HTV-7 arrival and capture Thursday at 6:30 a.m.


Today’s science work aboard the orbital lab included looking at DNA and fluid physics. Auñón-Chancellor sequenced DNA extracted from microbial samples collected inside the station. Feustel activated gear for an experiment researching the atomization of liquids that could improve fuel efficiency on Earth and in space.



Image above: Flying over Austral Ocean, seen by EarthCam on ISS, speed: 27’570 Km/h, altitude: 422,36 Km, image captured by Roland Berga (on Earth in Switzerland) from International Space Station (ISS) using ISS-HD Live application with EarthCam’s from ISS on September 24, 2018 at 20:45 UTC. Image Credits: Orbiter.ch Aerospace/Roland Berga.


Feustel later joined his Soyuz crewmates Oleg Artemyev of Roscosmos and Ricky Arnold of NASA and began preparations for their return to Earth Oct. 4. Artemyev will command the ride back to Earth inside the Soyuz MS-08 spacecraft flanked by the two astronauts. He and Feustel practiced on a computer their Soyuz descent back into Earth’s atmosphere. Arnold packed up crew provisions and other items inside the Russian spacecraft.


Related links:


Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html


Life Sciences Glovebox: https://cms.nasa.gov/feature/partnership-teamwork-enable-landmark-science-glovebox-launch-to-space-station


Sequenced DNA: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7687


Atomization of liquids: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=282


NASA TV: https://www.nasa.gov/nasatv


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Images (mentioned), Text, Credits: NASA/Mark Garcia/Orbiter.ch Aerospace/Roland Berga.


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