пятница, 12 октября 2018 г.

Improving paleotemperature reconstruction—Swiss lakes as a model system

For years, scientists have been trying to determine the climate of the past in order to make better predictions about future climate conditions. Now, there has been a breakthrough in the methodology of climate reconstruction based on microbial molecular fossils. Researchers under the direction of the University of Basel analyzed sediment samples collected from more than 30 Swiss lakes. Their findings can be applied to lakes worldwide, as the scientists report in Proceedings of the National Academy of Sciences.











Improving paleotemperature reconstruction—Swiss lakes as a model system
The researchers filtered hundreds of liters of water from Lake Lugano at depths of up to 275 m using a battery-operated
in-situ pump [Credit: University of Basel, Department of Environmental Sciences]

The remains of bacteria found in lake sediments are important for the reconstruction of past environmental conditions. Particularly, cell fragments known as membrane lipids allow climate geologists to infer historic temperatures. A team led by Professor Moritz Lehmann and Dr. Helge Niemann from the Department of Environmental Sciences at the University of Basel have now investigated a very specific class of climate-sensitive lipids in 36 alpine lakes.
Their application in climate reconstruction has long been known, but the biological sources of the lipids remained unclear. This severely complicated their application as a temperature indicator. “We initially assumed that these compounds were primarily produced by bacteria in soil and were washed into the lakes by rivers. But increasing evidence suggested that they are also formed within lake water itself,” explains Lehmann. Therefore, the aim of the research project was to characterize the ecology of the unknown bacteria that produce these lipids.


Link to methane


At the heart of the investigations was Lake Lugano in Switzerland, which offers an outstanding model system due to its strong stratification and great depth. “Using stable isotope analysis, we were able to show that these bacterial lipids are dominantly formed in the cold, deep waters of the lake—where oxygen is depleted and large amounts of the greenhouse gas methane are present,” says Dr. Yuki Weber, lead author of the study. The scientists were then able to confirm their findings from Lake Lugano by similar measurements from 35 other alpine lakes.


In addition to lipid analysis, the researchers also applied molecular biological methods, which allowed them to capture the bacterial diversity at various water depths in Lake Lugano. For the first time, the research team was able to show that these climate-sensitive lipids are produced under widely different environmental conditions, by distinct groups of microbes that reside at different water depths.


Refining the paleothermometer


Despite the numerous environmental factors that may influence the composition of these lipids, the researchers were able to determine the conditions under which the lipid thermometer still yields reliable temperature estimates. “By means of stable carbon isotope analysis, we can now determine whether the lipids were formed in soil or lake water. We are therefore confident that our study will make an important contribution to the improvement of paleoclimate data worldwide,” concludes Weber.


Source: University of Basel [October 10, 2018]



TANN



Archive


Newly described fossils could help reveal why some dinos got so big

By the time non-avian dinosaurs went extinct, plant-eating sauropods like the Brontosaurus had grown to gargantuan proportions. Weighing in as much as 100 tons, the long-neck behemoths are the largest land animals to ever walk the earth.











Newly described fossils could help reveal why some dinos got so big
Artist’s interpretation of Sarahsaurus aurifontanalis. The dinosaur was about the size of a car and
had powerful forelimbs with large claws. It lived during the Early Jurassic in North America
[Credit: Brian Engh]

How they grew so large from ancestors that were small enough to be found in a modern-day petting zoo has remained a mystery. A new, in-depth anatomical description of the best preserved specimens of a car-sized sauropod relative from North America could help paleontologists with unraveling the mystery.


Adam Marsh, a paleontologist at Petrified Forest National Park, led the description of the dinosaur while earning his master’s degree from The University of Texas at Austin Jackson School of Geosciences. The findings were published in the journal PLOS ONE. Marsh co-authored the paper with his advisor, Jackson School Professor Timothy Rowe.


The dinosaur—called Sarahsaurus aurifontanalis— lived about 185 million years ago during the Early Jurassic. It could hold important clues about sauropods’ size because it belonged to the dinosaur grouping that preceded them. Its evolutionary placement combined with the exquisite preservation of the specimens is giving researchers a detailed look into its anatomy and how it relates to its larger cousins.


“Sarahsaurus preserves in its anatomy the anatomical changes that were happening in the Late Triassic and Early Jurassic that were occurring in the evolutionary lineage,” Marsh said. “It can help tell us how getting big happens.”


The description is based on two skeletons discovered in Arizona by Rowe in 1997. The bones belong to the Navajo Nation, which owns the land where the fossils were discovered, and are curated by the Jackson School Museum of Earth History Vertebrate Paleontology Collections. The bones are slightly crushed, and in some cases still linked together into body parts such as the hand and tail. The only major missing part is the skull.


“The specimens are well preserved in three dimensions and remarkably complete, which is very rare in the fossil record,” said collections Director Matthew Brown. “Such complete specimens help paleontologists better understand the fragmentary and incomplete fossils remains we typically find.”











Newly described fossils could help reveal why some dinos got so big
Nearly complete skeleton of Sarahsaurus aurifontanalis; the only major missing piece is the skull. Paleontologist
Adam Marsh used this skeleton and one other to describe the anatomy of Sarahsaurus [Credit: The Jackson School
Museum of Earth History Vertebrate Paleontology Collections/The University of Texas at Austin]

Marsh describes Sarahsaurus as a “ground sloth-like” dinosaur. It stood upright, walked on its hind-legs and had powerful forelimbs with a large, curved claw capping the first finger of each hand. It had a lot in common with the earliest sauropod ancestors—like walking on two legs—but it was also starting to show features that would foreshadow how its massive relatives would evolve—such as an increase in body size and a lengthening of the neck vertebrae.


“It’s starting to gain the characters of getting large compared to the earliest members of the group,” Marsh said.


Size and neck-length are features that sauropods would take to extremes as they evolved. By studying these traits and others in Sarahsaurus, and seeing how they compare to those of other dinosaurs, scientists can help reveal how these changes occurred across evolutionary history and how different dinosaurs relate to one another.


For example, the anatomical review helped clarify the relationship between Sarahsaurus and two other sauropod relatives that lived in North America during the Early Jurassic. The researchers found that the three don’t have a common North American ancestor—instead they evolved from dinosaur lineages that came to North America independently.


Marsh is currently working on another study that could shed more light on how sauropods evolved. Led by Sterling Nesbitt, an assistant professor at Virginia Tech and research associate at the Jackson School’s vertebrate collections, the project involves tracking anatomical differences in dinosaur limb bones to determine which features relate to evolution and which relate to the age of an animal. Marsh said that the two Sarahsaurus skeletons examined for this paper are a great addition to the project.


“We’ve got two individuals from basically the same hole in the ground with different bumps and grooves on their femora,” Marsh said. “It lends itself really well to this comprehensive anatomical description and it’s going to be really important for comparisons of early dinosaur anatomy.”


Source: University of Texas at Austin [October 10, 2018]



TANN



Archive


Wild chimpanzees share food with their friends

Sharing meat after hunting and exchanging other valued food items is considered key in the evolution of cooperation in human societies. One prominent idea is that humans share valuable foods to gain future favors, such that those we chose to share with are more likely to cooperate with us in the future. Despite regularly occurring in humans, sharing food outside of kinship or mating relationships is rare in non-human animals. Our two closest living relatives, chimpanzees and bonobos, are two of the rare exceptions, and because of the important role of food sharing in human evolution, examining the sharing patterns of chimpanzees can help to answer questions on how sharing food amongst adults evolved and how it may have shaped human cooperation.











Wild chimpanzees share food with their friends
Chimpanzees share food with their friends [Credit: Liran Samuni, Tai Chimpanzee Project]

Researchers from the MPI-EVA observed natural food sharing behavior of the chimpanzees of the Tai National Park, Ivory Coast, and found that chimpanzees are very selective in who they share desirable food items, like meat, honey or large fruits, with. They show that chimpanzees were more likely to share food with their friends, and that neither high dominance status nor harassment by beggars influenced their decision. This complements results from another study by the same team published last month that examined meat sharing after group hunting of monkeys. There they found that chimpanzees in possession of meat after successful hunts were likely to reward other hunters by sharing with them. “Collectively our research shows that the chimpanzees decide when to share food based on the likelihood that this favor will be returned in the future”, says Liran Samuni, first author of both studies. “Or, in case of sharing after group hunts, sharing of meat is returning the favor for helping out.”
Previous studies in another subspecies of chimpanzees have suggested that food sharing in chimpanzees mainly occurs because of harassment pressure from beggars. “This was not the case for the Tai chimpanzees”, Catherine Crockford, senior author on the studies, points out, “emphasizing the high variation in cooperation across chimpanzee populations.” Human populations also vary in how cooperative they are and research is ongoing in both humans and non-human animals assessing what might make some populations more cooperative than others. “The need to stay in a cohesive unit, because of high predation pressure, or the capability to exhibit strong cohesion, because of rich food sources, are two possible scenarios to promote the expression of cooperative acts”, suggests Roman Wittig, the second senior author of the studies.
Additionally, the researchers collected urine samples from chimpanzees after hunting and food sharing events and measured the hormone oxytocin. “We know that oxytocin plays a strong role in lactation, which you could look at as an example of food sharing between mother and infant, and is generally involved in social behavior and bonding”, Liran Samuni explains. The researchers found high levels of oxytocin after chimpanzees shared meat and other valued foods, and after chimpanzee participated in hunting with others. “That we found higher oxytocin levels after both hunting and sharing adds to the idea that oxytocin is a key hormone involved in cooperation in general”, Liran Samuni points out.


The researchers conclude that like humans, Tai chimpanzee sharing is selective, and that friends and others that helped acquiring the food benefit more. Emotional connection, as is obvious amongst friends, likely played a crucial role in the evolution of human cooperation.


The study is published in Proceedings of the Royal Society B.


Source: Max Planck Institute For Evolutionary Anthropology [October 10, 2018]



TANN



Archive


Cambodia’s city of Koh Ker was occupied for centuries longer than previously...

The classic account of the ancient city of Koh Ker is one of a briefly-occupied and abruptly-abandoned region, but in reality, the area may have been occupied for several centuries beyond what is traditionally acknowledged, according to a study published in the open-access journal PLOS ONE by Tegan Hall of the University of Sydney, Australia and colleagues.











Cambodia's city of Koh Ker was occupied for centuries longer than previously thought
Coring locations across Koh Ker and its surrounds [Credit: Background image
supplied by Google Earth Credit: Hall et al., 2018]

Koh Ker was part of the Khmer kingdom during the Angkor period in what is now Cambodia. For a mere two decades in the tenth century CE, the city served as royal capital, and it has long been proposed that after the royal seat moved back to Angkor, the city and its surroundings were abandoned.


In this study, Hall and colleagues tested this theory by analyzing charcoal and pollen remains in sediment cores spanning several centuries in three Koh Ker localities, including the moat of the main central temple. From these data, they inferred a long history of fluctuations in fire regimes and vegetation which are highly indicative of patterns of human occupation and land use over time.


The newly-painted picture is of a region that was occupied well before the Angkor period, at least as far back as the late 7th century CE, and continuing seven centuries or more after the royal seat’s departure. The authors suggest that the mobility of royal houses may have had less of an impact on regional populations in the Khmer kingdom than previously thought. This study also highlights the utility of palaeoecological tools to reconstruct the occupational history of ancient urban settlements.


Hall adds: “When the environmental record is analyzed, it becomes clear that Koh Ker was much more than a temporary 10th century capital of the Khmer kingdom. The settlement history of the site is extensive and complex, beginning in the pre-Angkor period and lasting for centuries beyond the decline of Angkor.”


Source: Public Library of Science [October 10, 2018]



TANN



Archive


Humans may have colonized Madagascar later than previously thought

New archaeological evidence from southwest Madagascar reveals that modern humans colonized the island thousands of years later than previously thought, according to a study published in the open-access journal PLOS ONE by Atholl Anderson from the Australian National University, Canberra, Australia, and colleagues.











Humans may have colonized Madagascar later than previously thought
Taolambiby cut-marked bone dated to 1200 years ago [Credit: Anderson et al., 2018]

Madagascar’s colonization is key for tracing prehistoric human dispersal across the Indian Ocean, but exactly when human settlement began in the island remains unclear. Several pieces of evidence, including archaeological findings such as chert tools and charcoal, provide a direct indication of human occupation in Madagascar from about 1500 years before present (BP).
However, recent studies have suggested that the island’s early settlers made first landfall as early as 5000 years BP, based on indirect evidence from animal bones with damage (cutmarks) presumably resulting from human activity. Anderson and colleagues revisited these bone collections and excavated three new sites in southwest Madagascar to collect a larger sample of animal bone material.


They recovered 1787 bones belonging to extinct megafauna, such as hippos, crocodiles, giant lemurs, giant tortoise and elephant birds, dated between 1900 BP and 1100 years BP. Microscopic analyses revealed that potential cutmarks in bones dated before 1200 years BP were in fact animal biting and gnawing marks, root etching, or chop marks from the excavation, suggesting that cutmarking (and human activity) only appeared after that time point.


Similar results were obtained upon re-examination of bone damage previously interpreted as cutmarks in samples from old collections. The study also confirmed previous evidence of megafaunal extinction starting around 1200 years BP. These findings add to the evidence showing that prehistoric human colonization of Madagascar began between 1350 and 1100 years BP, and suggest that hunting gradually led to the extinction of the island’s megafauna.


The authors add: “Recent estimates indicate human arrival in Madagascar as early as ~10,000 years ago. Diverse evidence (from bone damage, palaeoecology, genomic and linguistic history, archaeology, introduced biota and seafaring capability) indicate initial human colonization of Madagascar was later at 1350-1100 y B.P. Results have implications for decline and extinction of megafauna, a proposed early African hunter-gatherer phase, and transoceanic voyaging from Southeast Asia.”


Source: Public Library of Science [October 10, 2018]



TANN



Archive


‘Vampire burial’ reveals efforts to prevent child’s return from grave

The discovery of a 10-year-old’s body at an ancient Roman site in Italy suggests measures were taken to prevent the child, possibly infected with malaria, from rising from the dead and spreading disease to the living.











'Vampire burial' reveals efforts to prevent child's return from grave
A rock was inserted into the mouth of a 10-year-old to keep the deceased child from rising from the grave
and spreading malaria, researchers believe [Credit: David Pickel/Stanford University]

The skeletal remains, uncovered by archaeologists from the University of Arizona and Stanford University, along with archaeologists from Italy, included a skull with a rock intentionally inserted into the mouth. Researchers believe the stone may have been placed there as part of a funeral ritual designed to contain disease — and the body itself.


The discovery of this unusual, so-called “vampire burial” was made over the summer in the commune of Lugnano in Teverina in the Italian region of Umbria, where UA archaeologist David Soren has overseen archaeological excavations since 1987.


“I’ve never seen anything like it. It’s extremely eerie and weird,” said Soren, a Regents’ Professor in the UA School of Anthropology and Department of Religious Studies and Classics. “Locally, they’re calling it the ‘Vampire of Lugnano.'”


The discovery was made at La Necropoli dei Bambini, or the Cemetery of the Babies, which dates to the mid-fifth century when a deadly malaria outbreak swept the area, killing many vulnerable babies and small children. The bodies of the young victims were buried at the site of an abandoned Roman villa that was originally constructed at the end of the first century B.C.


Until now, archaeologists believed the cemetery was designated specifically for infants, toddlers and unborn fetuses; in previous excavations of more than 50 burials, a 3-year-old girl was the oldest child found.


The discovery of the 10-year-old, whose age was determined based on dental development but whose sex is unknown, suggests that the cemetery may have been used for older children as well, said bioarcheologist Jordan Wilson, a UA doctoral student in anthropology who analyzed the skeletal remains in Italy.


“There are still sections of the cemetery that we haven’t excavated yet, so we don’t know if we’ll find other older kids,” Wilson said.











'Vampire burial' reveals efforts to prevent child's return from grave
The 10-year-old was discovered lying on its side in a fifth-century Italian cemetery
previously believed to be designated for babies, toddlers and unborn fetuses
[Credit: David Pickel/Stanford University]

Excavation director David Pickel, who has a master’s degree in classical archaeology from the UA and is now a doctoral student at Stanford, said the discovery has the potential to tell researchers much more about the devastating malaria epidemic that hit Umbria nearly 1,500 years ago, as well as the community’s response to it.


“Given the age of this child and its unique deposition, with the stone placed within his or her mouth, it represents, at the moment, an anomaly within an already abnormal cemetery,” Pickel said. “This just further highlights how unique the infant — or now, rather, child — cemetery at Lugnano is.”


In previous excavations at the Cemetery of the Babies, archaeologists found infant and toddler bones alongside items like raven talons, toad bones, bronze cauldrons filled with ash and the remains of puppies that appear to have been sacrificed — all objects commonly associated with witchcraft and magic. In addition, the body of the 3-year-old girl had stones weighing down her hands and feet — a practice used by different cultures throughout history to keep the deceased in their graves.


“We know that the Romans were very much concerned with this and would even go to the extent of employing witchcraft to keep the evil — whatever is contaminating the body — from coming out,” Soren said.


The “evil,” in the case of the babies and toddlers uncovered in Lugnano, was malaria, Soren believed. DNA testing of several of the excavated bones supported his theory.


Although the 10-year-old’s remains have not yet undergone DNA testing, the child had an abscessed tooth — a side effect of malaria — that suggests he or she may also have fallen victim to the disease, Wilson said.











'Vampire burial' reveals efforts to prevent child's return from grave
The rock that was inserted into the child’s mouth in this so-called “vampire burial”
[Credit: David Pickel/Stanford University]

The child was one of five new burials uncovered at the cemetery over the summer. The body was found lying on its left side in a makeshift tomb created by two large roof tiles propped against a wall — an alla cappuccina-style burial typical of Roman Italy.


“Knowing that two large roof tiles were used for this burial, I was expecting something unique to be found inside, perhaps a ‘double-inhumation’ — not uncommon for this cemetery — where a single burial contains two individuals,” Pickel said. “After removing the roof tiles, however, it became immediately clear to us that we were dealing with an older individual.”


The open position of the child’s jaw, which would not have opened naturally during decomposition with the body positioned on its side, suggests that the rock was intentionally inserted in the mouth after death, Wilson said. Teeth marks on the surface of the stone provide further evidence that it was placed purposefully.


The 10-year old was the first at the cemetery to be found with a stone in its mouth. Similar burials have been documented in other locations, including in Venice, where an elderly 16th-century woman dubbed the “Vampire of Venice” was found with a brick in her mouth in 2009. In Northamptonshire, England, in 2017, an adult male from the third or fourth century was found buried facedown with his tongue removed and replaced with a stone.


These types of burials are often referred to as vampire burials, since they are associated with a belief that the dead could rise again. Other examples of vampire burials throughout history include bodies being staked to the ground through the heart or dismembered prior to interment.


“This is a very unusual mortuary treatment that you see in various forms in different cultures, especially in the Roman world, that could indicate there was a fear that this person might come back from the dead and try to spread disease to the living,” Wilson said.


Archaeologists will return to Lugnano next summer to complete excavations of the cemetery and learn more about a dark time in history.


“It’s a very human thing to have complicated feelings about the dead and wonder if that’s really the end,” Wilson said. “Anytime you can look at burials, they’re significant because they provide a window into ancient minds. We have a saying in bioarchaeology: ‘The dead don’t bury themselves.’ We can tell a lot about people’s beliefs and hopes and by the way they treat the dead.”


Source: University of Arizona [October 12, 2018]



TANN



Archive


Dying Star Emits a Whisp


The three panels represent moments before, during, and after the faint supernova iPTF14gqr, visible in the middle panel, appeared in the outskirts of a spiral galaxy located 920 million light years away. The massive star that died in the supernova left behind a neutron star in a very tight binary system. These dense stellar remnants will ultimately spiral into each other and merge in a spectacular explosion, giving off gravitational and electromagnetic waves. Credit: SDSS/Caltech/Keck

The death of a massive star and the birth of a compact neutron star binary

A Caltech-led team of researchers has observed the peculiar death of a massive star that exploded in a surprisingly faint and rapidly fading supernova. These observations suggest that the star has an unseen companion, gravitationally siphoning away the star’s mass to leave behind a stripped star that exploded in a quick supernova. The explosion is believed to have resulted in a dead neutron star orbiting around its dense and compact companion, suggesting that, for the first time, scientists have witnessed the birth of a compact neutron star binary system.


The research was led by graduate student Kishalay De and is described in a paper appearing in the October 12 issue of the journal Science. The work was done primarily in the laboratory of Mansi Kasliwal (MS ’07, PhD ’11), assistant professor of astronomy. Kasliwal is the principal investigator of the Caltech-led Global Relay of Observatories Watching Transients Happen (GROWTH) project.


When a massive star—at least eight times the mass of the sun—runs out of fuel to burn in its core, the core collapses inwards upon itself and then rebounds outward in a powerful explosion called a supernova. After the explosion, all of the star’s outer layers have been blasted away, leaving behind a dense neutron star—about the size of a small city but containing more mass than the sun. A teaspoon of a neutron star would weigh as much as a mountain.


During a supernova, the dying star blasts away all of the material in its outer layers. Usually, this is a few times the mass of the sun. However, the event that Kasliwal and her colleagues observed, dubbed iPTF 14gqr, ejected matter only one fifth of the mass of the sun.


“We saw this massive star’s core collapse, but we saw remarkably little mass ejected,” Kasliwal says. 

“We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter.”


The fact that the star exploded at all implies that it must have previously been enveloped in lots of material, or its core would never have become heavy enough to collapse. But where, then, was the missing mass?


The researchers inferred that the mass must have been stolen—the star must have some kind of dense, compact companion, either a white dwarf, neutron star, or black hole—close enough to gravitationally siphon away its mass before it exploded. The neutron star that was left behind from the supernova must have then been born into orbit with that dense companion. Observing iPTF 14gqr was actually observing the birth of a compact neutron star binary. Because this new neutron star and its companion are so close together, they will eventually merge in a collision similar to the 2017 eventthat produced both gravitational waves and electromagnetic waves. 


Not only is iPTF 14gqr a notable event, the fact that it was observed at all was fortuitous since these phenomena are both rare and short-lived. Indeed, it was only through the observations of the supernova’s early phases that the researchers could deduce the explosion’s origins as a massive star.


“You need fast transient surveys and a well-coordinated network of astronomers worldwide to really capture the early phase of a supernova,” says De. “Without data in its infancy, we could not have concluded that the explosion must have originated in the collapsing core of a massive star with an envelope about 500 times the radius of the sun.”


The event was first seen at Palomar Observatory as part of the intermediate Palomar Transient Factory (iPTF), a nightly survey of the sky to look for transient, or short-lived, cosmic events like supernovae. Because the iPTF survey keeps such a close eye on the sky, iPTF 14gqr was observed in the very first hours after it had exploded. As the earth rotated and the Palomar telescope moved out of range, astronomers around the world collaborated to monitor iPTF 14gqr, continuously observing its evolution with a number of telescopes that today form the GROWTH network of observatories.


The Zwicky Transient Facility, the successor of iPTF at Palomar Observatory, is examining the sky even more broadly and frequently in the hopes of catching more of these rare events, which make up only one percent of all observed explosions. Such surveys, in partnership with coordinated follow-up networks like GROWTH, will enable astronomers to better understand how compact binary systems evolve from binary massive stars. 


The research was primarily funded by the National Science Foundation under the PIRE GROWTH project. A full list of funding sources and co-authors can be found in the Science study, titled “A hot and fast ultra-stripped supernova that likely formed a compact neutron star binary.” In addition to De and Kasliwal, other Caltech co-authors are Gary Doran of the Jet Propulsion Laboratory; graduate student Gina Duggan; Shri Kulkarni, George Ellery Hale Professor of Astronomy and Planetary Science; and Russ Laher and Frank Masci of Caltech’s Infrared Processing and Analysis Center.

For more about GROWTH, visit: http://growth.caltech.edu.


Written by Lori Dajose


Contact: 


Whitney Clavin
(626) 395-1856wclavin@caltech.edu


Source: Caltech/News



Archive link


Wind holds key to climate change turnaround

Antarctica has a current that circles the landmass as part of the Southern Ocean. This current is called the Antarctic Circumpolar Current. When the westerly winds strengthen during the Southern Hemisphere’s summer, waters south of the current acidify faster than can be accounted for in carbon dioxide from the atmosphere alone. The opposite pattern was observed north of the current.











Wind holds key to climate change turnaround
Understanding the factors that control ocean acidification is important for predicting the impact that the changing
chemistry of the ocean will have on marine organisms and ecosystems in the future. Though not all penguin
species live in Antarctica, all penguin species live naturally in the Southern Hemisphere
[Credit: Liang Xue/University of Delaware]

Why does this happen and why does it matter?


Researchers involved in the study say these effects are due to a combination of processes driven by these westerly winds — a theory that was borne out by two decades’ worth of observational data from south of Tasmania.


Understanding the factors that control ocean acidification is important for predicting the impact that the changing chemistry of the ocean will have on marine organisms and ecosystems in the future. The Southern Ocean, also known as the Antarctic Ocean, is a critical place to study these mechanisms because of its vast capacity to store carbon dioxide from the atmosphere, a crucial component of climate change.


Data-driven results benefit future prediction models


The fourth largest ocean, the Southern Ocean has a naturally low pH and saturation state for aragonite, a carbonate mineral that marine organisms need to build their shells. This is considered to be due to the Southern Ocean’s cold temperatures, which average -2 to 7 degrees Celsius (approximately 28 to 45 degrees Fahrenheit), and strong vertical mixing throughout the water column.


Because of these cold temperatures and deep mixing, the carbon dioxide absorbed at the water’s surface can be quickly transferred to and stored in the deep regions of the Southern Ocean, unlike most lower latitude oceans where huge temperature differences prevent the surface water and the deep ocean from mixing.


As atmospheric carbon dioxide levels continue to increase, however, surface waters in the Southern Ocean are expected to become increasingly vulnerable to ocean acidification.


“The Southern Ocean is a window to the deep ocean,” said Cai, an expert in inorganic carbon chemistry and the Mary A.S. Lighthipe Chair of Earth, Ocean and Environment at UD. ” Better understanding the mechanisms of ocean acidification here can help improve prediction models for how much atmospheric carbon dioxide the ocean can take up here and elsewhere.”


In the southern hemisphere, the main way that the atmosphere varies is through what is known as the Southern Annual Mode (SAM). As this mode changes from one extreme to another, the pressure difference causes the belt of westerly winds (or jet stream) around Antarctica to move north or south. When the jet stream of air strengthens (a positive SAM trend), it contracts toward Antarctica. When the jet stream weakens (a negative SAM trend), it expands north toward the equator.











Wind holds key to climate change turnaround
“The Southern Ocean is a window to the deep ocean” said Wei-Jun Cai, an expert in inorganic carbon
chemistry and the Mary A.S. Lighthipe Chair of Earth, Ocean and Environment at UD
[Credit: Liang Xue/University of Delaware]

In their study, the researchers explored how westerly winds regulate the rates of ocean acidification, using continuous data measurements of carbon dioxide from south of Tasmania recorded over two contrasting decades, 1991-2000 and 2001-2011. The researchers attributed the enhanced acidification to the westerly winds transporting more acidic waters horizontally from higher latitude locations toward the equator and vertically from the subsurface to the surface.


“When you have a pressure difference, you have a stronger wind and the wind always moves from high pressure to low pressure, driving the surface ocean currents from one point to another. In physical oceanography we call this wind-driven Ekman transport,” said Cai.


When westerly winds decrease, the result is the opposite and less acidic surface water is transferred toward the South Pole.


“Whether we study this in the Chesapeake Bay, the Gulf of Mexico or the Southern Ocean, it is all the same reason that another source of carbon dioxide or acidified water comes into the study area. But depending on the location, this mechanism can manifest itself differently,” said Cai.


This Southern Ocean mixing extends to a depth of approximately 300 to 400 meters (around 1,000 to 1,300 feet). This is far deeper than, say, in the Chesapeake Bay or oxygen-deficient Gulf of Mexico where the water’s deepest regions might extend only 20 to 50 meters (54-164 feet deep).


In theory, as atmospheric carbon dioxide increases, ocean carbon dioxide levels (i.e., ocean acidification) should increase in parallel. However, Cai explained that upwelling of deeper waters that contain more carbon dioxide combined with ocean circulation patterns, or mixing of different layers of the ocean, can cause the water’s pH and carbonate saturation state to vary quite a lot. Cai said though there have been a few recent papers in this area, he and his colleagues are the first to show with direct data that this is caused by wind stress.


“There is a lot of debate on this issue, but when put together, the two decades’ worth of data gave a consistent story that ocean circulation patterns really affect ocean acidification,” said Cai.


So, what does the Southern Ocean have to do with Delaware?


“The Southern Ocean is an area that really changes the deep ocean carbon dioxide signal because of this rapid mixing to the deep ocean,” said Cai. “Consequently, when wind speeds cause the layers of the water to mix and change circulation patterns, it really can drive changes that may be significant to the global ocean, and broadly, would eventually influence other areas, including the Atlantic Ocean.”


The study is published in Nature Communications.


Author: Karen B. Roberts | Source: University of Delaware [October 09, 2018]



TANN



Archive


A warmer climate will also be a drier climate, with negative impacts on forest growth

Warmer temperatures brought on by climate change will lead to drier soils and reduce tree photosynthesis and growth in forests later this century, according to a new University of Minnesota study published in the journal Nature.











A warmer climate will also be a drier climate, with negative impacts on forest growth
Credit: University of Minnesota

That important conclusion comes as scientists have speculated the opposite: that a warming climate might speed up a forests’ photosynthesis and facilitate growth in cold-weather climates found in North America, Europe and Asia.
“These results have important implications for the future,” said Peter Reich, a professor of forest resources in the College of Food, Agricultural and Natural Resource Sciences and the study’s lead author. “Typical dry spells already occur frequently enough to erase most of the potential benefits to tree growth of warmer summer temperatures. In a warmer future, the extra evaporation from warmer plants and soils will make those dry spells drier, further suppressing photosynthesis.”


Cool summers slow the growth of forests in cold places. That’s why scientists had hypothesized that warmer climatological conditions might help increase a forest’s growth rate in the future.


In their study, University of Minnesota researchers looked at more than 2,000 young trees from 11 different species—including birch, maple, oak, pine and spruce—growing in 48 plots in two forests in northern Minnesota. During the three-year study, researchers increased temperatures at the test plots—without use of chambers of any kind—by 3.4 degrees Celsius (6 degrees Fahrenheit), an increase that might happen in Minnesota by the end of the 21st century.


During the course of the study, researchers routinely measured photosynthesis at the plots to see how fast leaves were taking carbon dioxide out of the air to make sugars for the trees. Researchers found that:


– when soils were moist, photosynthesis was higher in plants growing at warmer than at ambient temperatures;


– in moderately to severely dry soils, which occurred during two-thirds of the growing season, warmer temperatures reduced photosynthesis;


– as a result, photosynthesis was reduced—on average—by the experimental climate warming.


“These results show that low soil moisture will slow down or eliminate any potential benefits of climate warming on tree photosynthesis even in moist, cold climates like Minnesota, Canada and Siberia,” said Reich.


The University of Minnesota research comes as the latest report from the United Nations’ Intergovernmental Panel on Climate Change was released. The U.N. report explains the likely global impacts of climate change by the year 2040, highlighting the multiple ways climate change will impact nature and humanity, including sustainability of food, fibre, water and biodiversity.


“Our work, alongside that of the community of scientists worldwide, can inform decisions that can put the world on a path toward a sustainable future,” said Reich. “This will be the largest challenge humanity has ever faced and unless we shift gears to effectively tackle it, future generations will view us as having completely failed in our responsibility as stewards of the earth.”


The study is based on B4Warmed, a multiyear project aimed at understanding how a changing climate might impact forests.


Source: University of Minnesota [October 09, 2018]



TANN



Archive


Increase in plastics waste reaching remote South Atlantic islands

The amount of plastic washing up onto the shores of remote South Atlantic islands is 10 times greater than it was a decade ago, according to new research published in the journal Current Biology.











Increase in plastics waste reaching remote South Atlantic islands
Plastics found washed up on the beach in St Helena [Credit: Dave Barnes]

Scientists investigating plastics in seas surrounding the remote British Overseas Territories discovered they are invading these unique biologically-rich regions. This includes areas that are established or proposed Marine Protected Areas (MPAs).


The study shows for the first time that plastic pollution on some remote South Atlantic beaches is approaching levels seen in industrialised North Atlantic coasts.


During four research cruises on the BAS research ship RRS James Clark Ross between 2013 and 2018, a team of researchers from ten organisations sampled the water surface, water column and seabed, surveyed beaches and examined over 2000 animals across 26 different species.


The amount of plastic reaching these remote regions has increased at all levels, from the shore to the seafloor. More than 90% of beached debris was plastic, and the volume of this debris is the highest recorded in the last decade.


Lead author Dr David Barnes from British Antarctic Survey (BAS) explains: “Three decades ago these islands, which are some of the most remote on the planet, were near-pristine. Plastic waste has increased a hundred-fold in that time, it is now so common it reaches the seabed. We found it in plankton, throughout the food chain and up to top predators such as seabirds.”


The largest concentration of plastic was found on the beaches. In 2018 we recorded up to 300 items per metre of shoreline on the East Falkland and St Helena — this is ten times higher than recorded a decade ago. Understanding the scale of the problem is the first step towards helping business, industry and society tackle this global environmental issue.”


Plastic causes many problems including entanglement, poisoning and starving through ingestion. The arrival of non-indigenous species on floating plastic “rafts” has also been identified as a problem for these remote islands. This study highlights that the impacts of plastic pollution are not only affecting industrialised regions but also remote biodiverse areas, which are established or proposed MPAs.


Andy Schofield, biologist, from the RSPB, who was involved in this research says: “These islands and the ocean around them are sentinels of our planet’s health. It is heart-breaking watching Albatrosses trying to eat plastic thousands of miles from anywhere. This is a very big wake up call. Inaction threatens not just endangered birds and whale sharks, but the ecosystems many islanders rely on for food supply and health.”


Source: British Antarctic Survey [October 09, 2018]



TANN



Archive


‘Sentinels of the sea’ at risk from changing climate

Climate change’s effect on coastal ecosystems is very likely to increase mortality risks of adult oyster populations in the next 20 years.











'Sentinels of the sea' at risk from changing climate
Credit: S. Pouvreau/Ifremer

That is the finding of a new study led by the University of Nantes, the LEMAR (the Marine Environmental Science Laboratory) in Plouzané and the Cerfacs (European center for research and advanced training in scientific computing) in Toulouse (France).


Published in the journal Environmental Research Letters, the research highlights a novel and comprehensive relationship between climate variability and historical mortality of adult oysters on the French Atlantic coast from 1993 to 2015.


The team’s results show oyster mortality usually increases after warm and wet winters over Northern Europe, affected by recurrent storms embedded in large weather circulation patterns covering the whole North Atlantic basin — known as the positive phase of the North Atlantic Oscillation (NAO).


The study’s lead author is Dr Yoann Thomas, from the French National Research Institute for Sustainable Development (IRD) at LEMAR. He said: “Benthic species like oysters are keystone species in coastal ecosystems. For example, they build reef habitats, which sustain a high biodiversity, and provide tremendous food source worldwide though fishing or aquaculture activities.


“But they are very sensitive to changes in climate and water quality, because they cannot move if a location becomes inhospitable. In this sense, oyster populations are sentinels of long-term climate fluctuations and climate trends, and more broadly of the ‘health’ of coastal ecosystems.


“We know the NAO is one of the key drivers of ecological variations like species individual growth rate, geographical distribution, phenology and survival. We show that recurrent positive NAO episodes in winter, leading to milder temperatures along the northern European coast, have a long-lasting effect on the biological and environmental factors influencing oyster mortality.


“We also show that the cumulative mortality rate over a year significantly increases after winters dominated by positive NAO. From a practical perspective, this lagged relationship can be used for potential predictability of annual mortality at several months lead-time.”


The researchers linked this climate-related risk to several environmental factors like the unlocking of the winter cold-water barrier for pathogens, the shortening of the resting phase for oyster, and enhanced metabolic rates leading to higher vulnerability in spring and summer.


The storms also caused more fresh water to flow from rivers into the sea, which impacts oysters by lowering the salinity of the water.


By analysing the results of more than 30 climate models and several greenhouse gases emission scenarios, the team used the extreme winter temperatures of the present-day NAO+ climate conditions as an analog to produce forecast assessments of oyster mortality risk factor in the next decades.


Dr Thomas said: “What today are exceptional levels of mortality could become the norm by 2035, even if the global temperature increase is limited to ~2°C above the pre-industrial period as per the Paris agreement. Natural long-term climate variability on top of anthropogenic-induced warming could ever accelerate or delay the increasing risk by only a decade or so.


He concluded: “The near-future looks bleak, but we show that this will be even worse without a clear reduction of the greenhouse gases emissions by human activities. We obviously need to take rapid action now to avoid further damage to very sensitive and vulnerable coastal ecosystems.”


Author: Simon Davies | Source: IOP Publishing [October 09, 2018]



TANN



Archive


Does it really matter if one animal goes extinct?

Imagine what it must have been like for those early ocean explorers setting foot on new islands full of interesting animals that they had never seen before. Giant tortoises with horns and spiny tails and gigantic birds that could not fly.











Does it really matter if one animal goes extinct?
Many large animals that eat fruit (birds, tortoises, lizards, bats) have gone extinct on islands. The remaining small
animals cannot swallow and disperse the largest fruits and those plants are now at risk of extinction too
[Credit: Julia Heinen]

Unfortunately, for the animals, these encounters often led to their extinction. Not used to running away from predators, they were easy prey to hungry sailors.


Explorers also brought along their ship rats, pigs, and cats, which ate the eggs of flightless birds laying on the ground.


But how bad was it? What are the consequences of these extinctions? And can we identify what animals or islands are most at risk?


Extinctions can cause more extinctions


First off, it is not only the animals themselves that are affected. The extinction of island animals in turn affects the plants that co-exist on these islands.


This is because many birds, mammals, and reptiles perform a vital service to the plants by eating their fruits, which contain seeds. After a while, these seeds will come out again and land somewhere else. This is how many plants move between different areas and make sure their little seeds can grow up in a good spot.


If there are no animals left to spread seeds, the plants are at risk of becoming extinct themselves. An island without animals and plants would be a lot less exciting than what the early explorers encountered.


Comparing islands across the world


In our research, we wanted to know just how bad the situation was for fruit-eating animals on islands across the world.


Were some animals more likely to go extinct then others? Have there been more extinctions on certain types of islands?











Does it really matter if one animal goes extinct?
Extinction of birds, mammals and reptiles that eat fruit on islands. Circle sizes show the number of animals that used
to live on each island and the colour shows what percentage of these animals have since gone extinct
[Credit: Adapted from Heinen et al. 2018, Ecography]

Together with my colleagues Daniel Kissling and Emiel van Loon from the University of Amsterdam, and Dennis Hansen from the Zoological Museum of Zurich, we investigated data from 74 islands across the world.


We wanted to get the full picture, so we looked at all of the birds, mammals, and reptiles that eat fruit. We also included animals that have recently become extinct. We checked to see whether the island size and remoteness could explain differences between the numbers of extinctions that we found. Then, we compared characteristics between the animals that had gone extinct with those that survived, such as differences in their weight and whether or not they can fly.


Large dodo-like animals are most at risk


We saw that large animals that cannot fly go extinct more often than any other. The Dodo bird on Mauritius is a famous example. But interestingly, we saw a knock-on effect of such extinctions. In fact, the mean weight of all fruit-eating animals on islands has reduced by 37 per cent due to the loss of large animals, such as a giant bird on New Caledonia, several large flying foxes and some of the Galapagos giant tortoises.


Many of the islands in our study have lost their biggest fruit-eating animal and sometimes also the second biggest. Today, only the smallest animals remain. Our data show that the largest animals that can be found on islands today are 51 per cent smaller than the largest animals that used to live there.


The loss of so many large fruit-eaters is extra challenging for the plants. This is because large fruit-eaters have larger beaks and mouths and can swallow the largest fruits. The smaller animals that remain on the islands today are simply not capable of swallowing and dispersing large fruits.


This means that the seeds of large plants are less likely to end up in good growing spots and make little plants of their own. Soon, we may not see many islands with such large trees with large fruits.


Small and remote islands are worse off


Luckily, not all islands have lost their fruit-eating animals. But the smallest islands have suffered most, and have lost the largest percentage of the fruit-eating animals that used to live there.



This is probably because it is more difficult to escape predators and hunters on small islands. Plus, compared to larger islands, they have relatively little forest and fewer fruiting trees to eat.


So, any problems that occur on small islands can easily have a big impact.


Isolated islands, far away from the mainland have also lost a large percentage of their fruit-eating animals. Again, these animals have lived without predators for a very long time, making them extra vulnerable to hunting by people and accompanying rats and cats.


We can prevent further extinctions


All these extinctions are of course very sad, but they are certainly no reason to give up hope!


We now know what animals and islands are most at risk: large animals that cannot fly, such as the Solomon flightless rails and megapode birds, on islands that are small and remote. And we now need to use this information to help prevent extinctions in the future.


Many organizations are working very hard to do this, and there are some great success stories of islands that have been restored to the way they were before humans arrived.


But a lot more effort is needed and anyone can help, either by volunteering for projects, donating or simply spreading the word. Hopefully, we will not lose the many exciting island animals and plants that we still have, and we can continue to be amazed, just like those early explorers.


The study is published in the journal Ecology.


Author: Julia Heinen | Source: ScienceNordic [October 09, 2018]


This article was originally published on ScienceNordic. Read the original here.



TANN



Archive


Ancient shipwrecks found in Greek waters tell tale of trade routes

Archaeologists in Greece have discovered at least 58 shipwrecks, many laden with antiquities, in what they say may be the largest concentration of ancient wrecks ever found in the Aegean and possibly the whole of the Mediterranean.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

The wrecks lie in the small island archipelago of Fournoi, in the Eastern Aegean, and span a huge period from ancient Greece right through to the 20th century. Most are dated to the Greek, Roman and Byzantine eras.
Although shipwrecks can be seen together in the Aegean, until now such a large number have not been found together.


Experts say they weave an exciting tale of how ships full of cargo travelling through the Aegean, the Mediterranean and the Black Sea met their fate in sudden storms and surrounded by rocky cliffs in the area.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

“The excitement is difficult to describe, I mean, it was just incredible. We knew that we had stumbled upon something that was going to change the history books,” said underwater archaeologist and co-director of the Fournoi survey project Dr. Peter Campbell of the RPM Nautical Foundation.


The foundation is collaborating on the project with Greece’s Ephorate of Underwater Antiquities, which is conducting the research.


When the international team began the underwater survey in 2015, they were astounded to find 22 shipwrecks that year. With their latest finds that number has climbed to 58, and the team believe there are even more secrets lying on the seabed below.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

“I would call it, probably, one of the top archaeological discoveries of the century in that we now have a new story to tell of a navigational route that connected the ancient Mediterranean,” Campbell told Reuters.
The vessels and their contents paint a picture of ships carrying goods on routes from the Black Sea, Greece, Asia Minor, Italy, Spain, Sicily, Cyprus, the Levant, Egypt and north Africa.


The team has raised more than 300 antiquities from the shipwrecks, particularly amphorae, giving archaeologists rare insight into where goods were being transported around the Mediterranean.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

“Ninety percent of the shipwrecks that we found in the Fournoi archipelago carried a cargo of amphorae.


“The amphora is a vessel used mainly for transporting liquids and semi-liquids in antiquity, so the goods it would be transporting were mostly wine, oil, fish sauces, perhaps honey,” archaeologist and Fournoi survey project director Dr. George Koutsouflakis from the Ephorate of Underwater Antiquities, said. Fish sauce from the Black Sea region in antiquity was an expensive commodity, he added.


They were particularly excited by amphorae they found originating from the Black Sea and north Africa in shipwrecks from the late Roman period, as it is rare to find cargo from these regions intact in shipwrecks in the Aegean, said Koutsouflakis.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

Bad weather is the most likely explanation for why the ships all sank in the same area, he said. The region experiences lots of sudden, fierce squalls and is surrounded by rocky shores.
Fournoi was a stoppover point for ships to spend the night during their journey.


“Because there are narrow passages between the islands, a lot of gulfs, and descending winds from the mountains, sudden windstorms are created.











Ancient shipwrecks found in Greek waters tell tale of trade routes
Credit: Vassilis Mentogiannis/Hellenic Ephorate of Underwater Antiquities/via Reuters

“It is not a coincidence that a large number of the wrecks have been found in those passages…if there is a sudden change in the wind’s direction, and if the captain was from another area and was not familiar with the peculiarities of the local climate, he could easily end up losing control of the ship and falling upon the rocks,” said Koutsouflakis.


In later times Fournoi was considered a pirate’s haven, said Campbell. Pirates were drawn to the area by the abundant flow of vessels laden with rich cargo. Although weather was believed to be the primary reason for the sinkings, piracy may have contributed in some cases, he said.


The condition of the shipwrecks vary. Some are well preserved, others are in pieces after the ships crashed on the rocks.



“We have wrecks that are completely virgin. We feel we were the first ones to find them, but they are in very deep waters – at a depth of 60 meters. Usually from 40 meters and below we have wrecks in good condition. Anything above 40 meters has either lost its consistency or has been badly looted in the past,” said Koutsouflakis.
The survey team discovered the shipwrecks from sightings by local sponge divers and fishermen.


Fournoi is made up of 20 small islands, islets and reefs between the larger Ikaria, Patmos and Samos islands. The population does not reach more than 1,500, mainly located on the main island of Fournoi.


The team, which includes archaeologists, architects, conservators, and divers, want to create a centre for underwater archaeology in Fournoi for students, as well as a local museum to house their finds.


Authors: Vassilis Triandafyllou & Idyli Tsakiri | Source: Reuters [October 11, 2018]



TANN



Archive


2018 October 12 The Falcon 9 Nebula Image Credit &…


2018 October 12


The Falcon 9 Nebula
Image Credit & Copyright: Brian Haidet


Explanation: Not the Hubble Space Telescope’s latest view of a distant planetary nebula, this illuminated cloud of gas and dust dazzled even casual U.S. west coast skygazers on October 7. Taken about three miles north of Vandenberg Air Force Base, the image follows plumes and exhaust from the first and second stage of a SpaceX Falcon 9 rocket rising through southern California’s early evening skies. In the fading twilight, the reddish smoke drifting in the foreground at the right is from the initial ascent of the rocket. The expanding blue and orange filamentary plumes are from first and second stage separation and the first stage boostback burn, still in sunlight at extreme altitudes. But the bright spot below center is the second stage itself headed almost directly away from the camera, accelerating to orbital velocity and far downrange. Pulsed thrusters form the upside down V-shape at the top as they guide the reusable Falcon 9 first stage back to the landing site.


∞ Source: apod.nasa.gov/apod/ap181012.html


Carved Roman Stones, Arbeia Roman Fort, South Shields, Tyne and WearCarved Roman...






Carved Roman Stones, Arbeia Roman Fort, South Shields, Tyne and Wear


Carved Roman tombstones, altars and columns.


Source link


HiPOD (11 October 2018): The Walls in Milankovic Crater   – The…




HiPOD (11 October 2018): The Walls in Milankovic Crater


   – The objective of this observation is to determine the nature of depressions in the mantle on the wall of Milankovic Crater. It seems that the deeper depressions into the mantle have a straight edge along the southern wall. Perhaps, the straight forms are related to the latitude and sun angles together with a deeper, darker layer. (310 km above the surface. Black and white is less than 5 km across; enhanced color is less than 1 km.)


NASA/JPL/University of Arizona 


Meteor Activity Outlook for October 13-19, 2018

This pole grazing meteor was captured by on September 8, 2018, by Joseph Msallam from Troodos, Limassol on the island of Cyprus. Its trajectory indicates that it is a possible member of the September epsilon Perseid stream.

During this period the moon will reach its new phase on Tuesday October 16th. At this time the moon will be located 90 degrees east of the sun and will set near midnight local daylight saving time (DST). This weekend the waxing crescent moon will set during the late evening hours leaving the remainder of the night nice and dark for meteor observing. The estimated total hourly meteor rates for evening observers this week is near 3 for those viewing from the northern hemisphere and 2 for those located south of the equator. For morning observers the estimated total hourly rates should be near 22 as seen from mid-northern latitudes and 16 from the southern tropics. Evening rates are slightly reduced during this period due to moonlight. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.


The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning October 13/14. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.





Radiant Positions at 9pm LDT


Radiant Positions at 21:00

Local Daylight Saving Time






Radiant Positions at 01:00 Local Daylight Saving Time


Radiant Positions at 01:00

Local Daylight Saving Time






Radiant Positions at 5am LDT


Radiant Positions at 5:00

Local Daylight Saving Time





These sources of meteoric activity are expected to be active this week..


The Northern Taurids (NTA) are active from a large radiant located at 01:56 (029) +16. This area of the sky is located in southwestern Aries, 3 degrees south of the 3rd magnitude double star known as Mesarthim (gamma 2 Arietis). This position is close to the Southern Taurids so care must be taken in separating these meteors. You should have the two radiants near the center of your field of view to properly differentiate these sources. The maximum is not expected until early November so current rates would be 1 per hour or less. These meteors may be seen all night long but the radiant is best placed near 0200 DST when it lies on the meridian and is located highest in the sky. With an entry velocity of 28 km/sec., the average Northern Taurid meteor would be of slow velocity.


The Southern Taurids (STA) are active from a large radiant centered near 02:12 (033) +09. This position lies in northeastern Cetus, near the spot occupied by the 4th magnitude star known as xi 2 Ceti. These meteors may be seen all night long but the radiant is best placed near 0200 DST when it lies on the meridian and is located highest in the sky. Rates at this time should be near 3 per hour regardless of your location. With an entry velocity of 27 km/sec., the average Southern Taurid meteor would be of slow velocity.


The omicron Eridanids (OER) were discovered by Japanese observers using video data from SonotoCo in 2007-2008. The activity period ranges from October 16 – November 24 with maximum activity  occurring on November 4th. This is a weak shower that usually produces rates less than 1 per hour, even at maximum activity. The radiant is currently located at  02:20 (035) -06, which places it in eastern Cetus, 8 degrees southwest of the 4th magnitude star known as delta Ceti. This location is close to the source of the Southern Taurids so care must be taken to separate these meteors. Like the STA’s these meteors may be seen all night long but the radiant is best placed near 0200 DST when it lies on the meridian and is located highest in the sky. With an entry velocity of 29 km/sec., the average omicron Eridanid meteor would be of slow velocity.


The Orionids (ORI) are active from a radiant located at 05:51 (088) +16. This area of the sky is located on the Taurus/Orion border, 8 degrees north of the bright 1st magnitude orange star known as Betelgeuse (alpha Orionis). This area of the sky is best placed near 05:00 DST, when it lies highest above the horizon. Current rates should be near 3-5 per hour no matter your location. With an entry velocity of 67 km/sec., most activity from this radiant would be of swift speed.


The nu Eridanids (NUE) were co-discovered by Japanese observers using SonotoCo and Juergen Rendtel and Sirko Molau of the IMO. Activity from this long-period stream stretches from August 23 all the way to November 16. A very shallow maximum occurred near September 24. The radiant currently lies at 06:24 (096) +10, which places it in northwestern Monoceros, 7 degrees south of the 2nd magnitude star known as Alhena (gamma Geminorum). This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to be near 1 per hour during this period no matter your location. With an entry velocity of 67 km/sec., the average meteor from this source would be of swift velocity. Some experts feel that these meteors are early members of the Orionid shower, which peaks on October 22.


The epsilon Geminids (EGE) are active from September 30 through October 25 with maximum activity occurring on October 11. The radiant is currently located at 06:29 (097) +28, which places where the borders of Auriga, and Gemini, 3 degrees northwest of the 3rd magnitude star known as Mebsuta (epsilon Geminorum). This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates should be near 2 per hour from the northern hemisphere and 1 as seen from south of the equator. With an entry velocity of 70 km/sec., most activity from this radiant would be of swift speed.


The October Ursae Majorids (OCU) were discovered by a group of Japanese observers in 2006. This source is only active for 3 nights centered on October 15th. The radiant is located at 09:40 (145) +65. This position lies in western Ursa Major, 3 degrees northwest of the faint star known as 23 Ursae Majoris. This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Rates at maximum would be most likely near 1 per hour as seen from the northern hemisphere. Due to the high northern declination, these meteors would be extremely difficult to see from the southern hemisphere. With an entry velocity of 56km/sec., most activity from this radiant would be of swift speed.


The Leonis Minorids (LMI) are active from October 12-Nov 5 with maximum activity occurring on October 22nd. This radiant is currently located at 10:07 (152) +40, which places it in northern Leo Minor, 3 degrees southwest of the 3rd magnitude star known as Tania Australis (mu Ursae Majoris). The radiant is best placed just before dawn when it lies highest in a dark sky. This shower is better situated for observers situated in the northern hemisphere where the radiant rises far higher into the sky before the start of morning twilight. Current rates would be less than 1 no matter your location. At 62km/sec., the average Leonis Minorid is swift. From my personal experience this minor shower produces a high proportion of bright meteors.


As seen from the mid-northern hemisphere (45N) one would expect to see approximately 10 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 7 per hour as seen from rural observing sites and 1 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the evening hours due to moonlight.


The list below offers the information from above in tabular form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.































































































SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS
RA (RA in Deg.) DEC Km/Sec Local Daylight Saving Time North-South
Northern Taurids (NTA) Nov 02 01:56 (029) +16 28 02:00 1 – <1 II
Southern Taurids (STA) Oct 29 02:12 (033) +09 27 02:00 3 – 3 II
omicron Eridanids (OER) Nov 04 02:20 (035) -06 29 02:00 <1 – <1 IV
Orionids (ORI) Oct 22 05:51 (088) +16 67 05:00 4 – 3 I
nu Eridanids (NUE) Sep 24 06:24 (096) +10 67 06:00 1 -1 IV
epsilon Geminids (EGE) Oct 11 06:29 (097) +28 70 06:00 2 – 2 II
October Ursae Majorids (OCU) Oct 15 09:40 (145) +65 56 09:00 1 – <1 IV
Leonis Minorids (LMI) Oct 22 10:07 (152) +40 62 10:00 <1 – <1 IV

Source link


Featured

    Солнечное затмение 14 декабря 2020 года  — полное  солнечное затмение  142  сароса , которое лучше всего будет видно в юго-восточной час...

Popular