воскресенье, 23 сентября 2018 г.

Matter falling into a black hole at 30 percent of the speed of light

A UK team of astronomers report the first detection of matter falling into a black hole at 30% of the speed of light, located in the centre of the billion-light year distant galaxy PG211+143. The team, led by Professor Ken Pounds of the University of Leicester, used data from the European Space Agency’s X-ray observatory XMM-Newton to observe the black hole. Their results appear in a new paper in Monthly Notices of the Royal Astronomical Society.

Matter falling into a black hole at 30 percent of the speed of light
Characteristic disc structure from the simulation of a misaligned disc around a spinning black hole
[Credit: K. Pounds et al./University of Leicester]

Black holes are objects with such strong gravitational fields that not even light travels quickly enough to escape their grasp, hence the description ‘black’. They are hugely important in astronomy because they offer the most efficient way of extracting energy from matter. As a direct result, gas in-fall – accretion – onto black holes must be powering the most energetic phenomena in the Universe.

The centre of almost every galaxy – like our own Milky Way – contains a so-called supermassive black hole, with masses of millions to billions of times the mass of our Sun. With sufficient matter falling into the hole, these can become extremely luminous, and are seen as a quasar or active galactic nucleus (AGN).

However black holes are so compact that gas is almost always rotating too much to fall in directly. Instead it orbits the hole, approaching gradually through an accretion disc – a sequence of circular orbits of decreasing size. As gas spirals inwards, it moves faster and faster and becomes hot and luminous, turning gravitational energy into the radiation that astronomers observe.

The orbit of the gas around the black hole is often assumed to be aligned with the rotation of the black hole, but there is no compelling reason for this to be the case. In fact, the reason we have summer and winter is that the Earth’s daily rotation does not line up with its yearly orbit around the Sun.

Until now it has been unclear how misaligned rotation might affect the in-fall of gas. This is particularly relevant to the feeding of supermassive black holes since matter (interstellar gas clouds or even isolated stars) can fall in from any direction.

Matter falling into a black hole at 30 percent of the speed of light
The XMM-Newton spacecraft [Credit: ESA]

Using data from XMM-Newton, Prof. Pounds and his collaborators looked at X-ray spectra (where X-rays are dispersed by wavelength) from the galaxy PG211+143. This object lies more than one billion light years away in the direction of the constellation Coma Berenices, and is a Seyfert galaxy, characterised by a very bright AGN resulting from the presence of the massive black hole at its nucleus.

The researchers found the spectra to be strongly red-shifted, showing the observed matter to be falling into the black hole at the enormous speed of 30 per cent of the speed of light, or around 100,000 kilometres per second. The gas has almost no rotation around the hole, and is detected extremely close to it in astronomical terms, at a distance of only 20 times the hole’s size (its event horizon, the boundary of the region where escape is no longer possible).

The observation agrees closely with recent theoretical work, also at Leicester and using the UK’s Dirac supercomputer facility simulating the ‘tearing’ of misaligned accretion discs. This work has shown that rings of gas can break off and collide with each other, cancelling out their rotation and leaving gas to fall directly towards the black hole.

Prof. Pounds, from the University of Leicester’s Department of Physics and Astronomy, said: “The galaxy we were observing with XMM-Newton has a 40 million solar mass black hole which is very bright and evidently well fed. Indeed some 15 years ago we detected a powerful wind indicating the hole was being over-fed. While such winds are now found in many active galaxies, PG1211+143 has now yielded another ‘first’, with the detection of matter plunging directly into the hole itself.”

He continues: “We were able to follow an Earth-sized clump of matter for about a day, as it was pulled towards the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole.”

A further implication of the new research is that ‘chaotic accretion’ from misaligned discs is likely to be common for supermassive black holes. Such black holes would then spin quite slowly, being able to accept far more gas and grow their masses more rapidly than generally believed, providing an explanation for why black holes which formed in the early Universe quickly gained very large masses.

Source: Royal Astronomical Society [September 20, 2018]



What makes a mammal a mammal? Our spine, say scientists

Mammals are unique in many ways. We’re warm-blooded and agile in comparison with our reptilian relatives.

What makes a mammal a mammal? Our spine, say scientists
Illustration showing an early mammal relative, Thrinaxodon, which was part of the first group
to have an extra fourth section of their backbones [Credit: April Neander]

But a new study, funded by the National Science Foundation (NSF) and led by Harvard University researchers Stephanie Pierce and Katrina Jones, suggests we’re unique in one more way — the makeup of our spines. The researchers describe their finding in a paper published this week in the journal Science.

“The spine is basically like a series of beads on a string, with each bead representing a single bone — a vertebra,” said Pierce, curator of vertebrate paleontology at Harvard. “In most four-legged animals, like lizards, the vertebrae all look and function the same.

“But mammal backbones are different. The different sections or regions of the spine — like the neck, thorax and lower back — take on very different shapes. They function separately and so can adapt to different ways of life, like running, flying, digging and climbing.”

While mammal backbones are specialized, the regions that underlie them were believed to be ancient, dating back to the earliest land animals. Mammals made the most of the existing anatomical blueprint, or so scientists believed. However, the new study is challenging this idea by looking into the fossil record.

What makes a mammal a mammal? Our spine, say scientists
Edaphosaurus, an early mammal relative that lived around 300 million years ago, which had
a more primitive backbone with just three different regions [Credit: Field Museum]

“There are no animals alive today that record the transition from a ‘lizard-like’ ancestor to a mammal,” said Jones, lead author of the study. “To do that, we have to dive into the fossil record and look at the extinct forerunners of mammals, the non-mammalian synapsids.”

These ancient ancestors hold the key to understanding the origin of mammal-specific characteristics, including the spine. But studying fossils isn’t easy. “Fossils are scarce and finding extinct animals with all 25-plus vertebrae in place is incredibly rare,” Jones said.

To tackle this problem, the researchers combed museum collections around the world to study the best-preserved fossils of animals that lived some 320 million years ago.

“Looking into the ancient past, an early change in mammals’ spinal columns was an important first step in their evolution,” said Dena Smith, a program director in NSF’s Division of Earth Sciences, which funded the research. “Changes in the spine over time allowed mammals to develop into the myriad species we know today.”

What makes a mammal a mammal? Our spine, say scientists
Skeletons of a modern dog and cat – note the regions with different shapes of bones that make up the spine
[Credit: Field Museum]

Pierce and Jones, along with co-author Ken Angielczyk of the Field Museum in Chicago, examined dozens of fossil spines, as well as more than 1,000 vertebrae of living animals, including mice, alligators, lizards and amphibians. They wanted to find out whether mammal vertebral regions were as ancient as previously thought, or if mammals were doing something unique.

“If vertebral regions had remained unchanged through evolution, as hypothesized, we would expect to see the same regions in the non-mammalian synapsids that we see in mammals today,” said Pierce.

But that doesn’t seem to be the case. When the researchers compared the positioning and shape of the vertebrae, they found something surprising. The spine had gained new regions during mammal evolution.

“The earliest non-mammalian synapsids had fewer regions than living mammals,” said Jones.

What makes a mammal a mammal? Our spine, say scientists
The three stages of mammal backbone evolution on a phylogenetic tree. Bottom right: Edaphosaurus;
middle left: Thrinaxodon; top: a modern day mouse [Credit: Stephanie E. Pierce,
Museum of Comparative Zoology, Harvard University]

About 250 million years ago, a new region evolved near the shoulders and front legs. Dramatic changes also began to appear in the forelimbs of animals known as non-mammalian therapsids.

These simultaneous developments, the scientists believe, likely occurred in conjunction with changes in how creatures walked and ran.

“There appears to be some sort of cross-talk during development between the tissues that form the vertebrae and the shoulder blade,” Pierce said. “We think this interaction resulted in the addition of a region near the shoulder as the forelimbs of our ancestors evolved to take on new shapes and functions.”

Later, a region emerged near the pelvis. “It is this last region, the ribless lumbar region, that appears to be able to adapt the most to different environments,” said Pierce.

Shows the primitive number of regions (3) for synapsids (mammals and their relatives). The fossil, Edaphosaurus, belongs

 to a group of mammal ancestors known as ‘pelycosaurs.’ Edaphosaurus lived during the late Carboniferous to early 

Permian (300-280 million years ago) of North America and Europe [Credit: Stephanie E. Pierce, 

Museum of Comparative Zoology, Harvard University]

The final step in building the mammal backbone may be linked with changes in Hox genes, important to spine regions early in their development.

“We’ve been able to make connections among changes in the skeletons of extinct animals and ideas in modern developmental biology and genetics,” Jones said. “This combined approach is helping us understand what makes a mammal a mammal.”

Source: National Science Foundation [September 20, 2018]



Fat from 558 million years ago reveals earliest known animal

Scientists from The Australian National University (ANU) and overseas have discovered molecules of fat in an ancient fossil to reveal the earliest confirmed animal in the geological record that lived on Earth 558 million years ago.

Fat from 558 million years ago reveals earliest known animal
Dickinsonia fossil [Credit: The Australian National University (ANU)]

The strange creature called Dickinsonia, which grew up to 1.4 metres in length and was oval shaped with rib-like segments running along its body, was part of the Ediacara Biota that lived on Earth 20 million years prior to the ‘Cambrian explosion’ of modern animal life.

ANU PhD scholar Ilya Bobrovskiy discovered a Dickinsonia fossil so well preserved in a remote area near the White Sea in the northwest of Russia that the tissue still contained molecules of cholesterol, a type of fat that is the hallmark of animal life.

Lead senior researcher Associate Professor Jochen Brocks said the ‘Cambrian explosion’ was when complex animals and other macroscopic organisms – such as molluscs, worms, arthropods and sponges – began to dominate the fossil record.

“The fossil fat molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought,” said Associate Professor Jochen Brocks from the ANU Research School of Earth Sciences.

“Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Edicaran Biota were: giant single-celled amoeba, lichen, failed experiments of evolution or the earliest animals on Earth. The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology.”

Fat from 558 million years ago reveals earliest known animal
Scientists from The Australian National University (ANU) have discovered molecules of fat in an ancient fossil to 
reveal the earliest confirmed animal in the geological record that lived on Earth 558 million years ago 
[Credit: The Australian National University]

Mr Bobrovskiy said the team developed a new approach to study Dickinsonia fossils, which hold the key between the old world dominated by bacteria and the world of large animals that emerged 540 million years ago during the ‘Cambrian explosion’.

“The problem that we had to overcome was finding Dickinsonia fossils that retained some organic matter,” said Mr Bobrovskiy from the ANU Research School of Earth Sciences.

“Most rocks containing these fossils such as those from the Ediacara Hills in Australia have endured a lot of heat, a lot of pressure, and then they were weathered after that – these are the rocks that palaeontologists studied for many decades, which explained why they were stuck on the question of Dickinsonia’s true identity.”

Palaeontologists normally study the structure of fossils, but Mr Bobrovskiy extracted and analysed molecules from inside the Dickinsonia fossil found in ancient rocks in Russia to make the breakthrough discovery.

“I took a helicopter to reach this very remote part of the world – home to bears and mosquitoes – where I could find Dickinsonia fossils with organic matter still intact,” Mr Bobrovskiy said.

“These fossils were located in the middle of cliffs of the White Sea that are 60 to 100 metres high. I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone and repeat this process until I found the fossils I was after.”
Associate Professor Brocks said being able to study molecules from these ancient organisms was a gamechanger.

“When Ilya showed me the results, I just couldn’t believe it,” he said.

“But I also immediately saw the significance.”

ANU led the research in collaboration with scientists from the Russian Academy of Science and the Max Planck Institute for Biogeochemistry and the University of Bremen in Germany.

The research is published in Science.

Source: Australian National University [September 20, 2018]



Nomadic hunter-gatherers show that cooperation is flexible, not fixed

In the realm of evolutionary biology and survival of the fittest, cooperation is a risky business. Yet humans do it on a scope and a scale unmatched by any group in the animal world.

Nomadic hunter-gatherers show that cooperation is flexible, not fixed
The Hadza way of life offers the chance to study how certain human traits have evolved. Between 2010 and 2016,
psychologist Coren Apicella visited more than 50 camps in Hadzaland to study cooperation. Her new paper,
co-authored by Penn doctoral candidates Kristopher Smith and Tomás Larroucau, finds that this
trait is flexible, highlighting humans’ capacity to adapt to different social environments
[Credit: Eduardo Azevedo]

“We engage in costly acts to help others,” says University of Pennsylvania psychologist Coren Apicella. “Figuring out how humans became a cooperative species is often called one of science’s great puzzles. One solution is to ensure that cooperators only interact with other cooperators, so they can benefit from that trait and not be taken advantage of by cheaters.”

Apicella and doctoral candidates Kristopher Smith and Tomás Larroucau conducted research with the Hadza people of Tanzania, one of the last remaining nomadic hunter-gatherer populations. The six years of work shows that, year after year, cooperators live with other cooperators–results remarkable in light of Hadza residence patterns. Their group settings, called camps, change every six to eight weeks, meaning individuals reside with different people each year.

One of the work’s goals was to clarify how hunter-gatherers, known for their fluid living arrangements, maintain this pattern, according to Apicella, an assistant professor of Psychology in the School of Arts and Sciences. In one theory, people are consistently either cooperative or selfish; individuals gravitate toward those who behave similarly to themselves, what’s known as homophily.

The researchers discovered that this wasn’t case, however. A person’s level of cooperation in a past year did not predict her level of cooperation in a future year. Instead, a person’s propensity to cooperate depended largely on how much her new camp shared as a whole. The findings, which appeared in the journal Current Biology, highlight humans’ capacity to adapt to different social environments.

“There’s a whole lot to be optimistic about here,” Apicella says. “People are changeable. We’re not permanently altered by our experiences at a single point in time. We’re flexible and largely in sync with the people around us.”

Data collected from visits to 56 camps between 2010 and 2016 lead to a greater understanding of this facet of human biology. Nearly 400 Hadza adults of all ages participated in the work with the Penn psychologists, playing what’s called a public goods game. It’s a tool often used in similar contexts to determine how much someone might contribute to the overall good of a group at a cost to herself.

In Western settings, the public goods game often includes money. Every participant receives a set dollar amount, say $10. Each $1 that they contribute to the public pot gets tripled, and the resulting amount gets evenly shared amongst everyone, regardless of individual contribution. Individuals keep the money they don’t donate.

“You can always do better by not contributing anything,” says Smith, a fifth-year psychology graduate student. “Economists predict that in this game, people should not contribute anything. But humans don’t always act in pure self-interest, and in fact, many do contribute to the public good.”

For the Hadza, a resource like honey–their favorite food–is more relevant than money. So Apicella and Smith played the game using the same general concept, but with straws filled with honey. Each participant started with four, and any they put toward the whole group got tripled; they knew ahead of time they could keep whatever they didn’t distribute.

“You have some camps in which everyone is contributing, and some where people are contributing very little,” Smith says. “In a random population, you’d expect all the camps to contribute similar amounts.”

Apicella interprets that behavior to mean that the Hadza choose to cooperate based on local camp norms. And, she speculates, that because sharing norms are so powerful, people are choosing campmates not based on their level of cooperation, but instead, on their ability to produce.

“Food that comes into camp is shared widely,” she says. “How cooperative people are will not matter as much as how much food they can obtain. Inept hunters or gatherers will not have food to share, regardless of how cooperative they might be.”

Broadly, these findings point to the importance of adapting to new local environments, as well as humans’ ability to do so quickly. For the Hazda, that equates to the ever-changing camps, but for Western populations, it could mean, for instance, starting a new job, marrying into a family, or sending a child to a new daycare.

“This has important implications for boosting cooperation in other settings, too,” Apicella says, “for policymakers, employers, school administration–really anyone interested in increasing teamwork among individual members.”

The findings are correlational, though they are consistent within and across years and control for many variables, including geography, age, sex, and number of children. In the future, Smith says they would like to conduct experimental work on cooperation, potentially replicating the frequently changing environments of the Hadza culture within a Western setting.

“If the hunter-gatherers are living with people who cooperate, they themselves cooperate,” Smith says. “The Hadza are changing camps every six to eight weeks. It might be that if people in Western populations had that sort of movement, that change in their social environment, then we’d see more adoption of local norms.”

Source: University of Pennsylvania [September 20, 2018]



5,000-year-old baskets, ropes and nets discovered in Oman

Fossilised baskets, ropes and nets that date back to the early Bronze Age, between 3,100 BCE and 2,700 BCE, have recently been discovered, the National Museum Oman has announced.

5,000-year-old baskets, ropes and nets discovered in Oman
Credit: National Museum Oman/Twitter

The new set of archaeological discoveries were found at a human settlement near Ra’s Al Hadd and are over 5,000 years old. These discoveries have shed light on how people in Oman lived during that age. Back then, Ra’s Al Hadd was an important seaside town in the Arabian Gulf and happened to be its easternmost point, jutting into the Sea of Oman.

Originally made from organic materials and fibres, chemical reactions over thousands of years have turned the discoveries into hardened, calcified fossils.

“Inside the houses of an Early Bronze Age settlement at Ra’s al-Hadd, archaeologists have discovered fossilised imprints of baskets, ropes and nets,” said a spokesperson for the museum.

“The perishable organic materials originally used to produce these objects have been slowly replaced by concretions of calcium carbonate over thousands of years. This find has provided a rare glimpse of materials and techniques used in the local manufacture of such everyday crafts objects in prehistoric times,” the spokesperson added.

The remains of these household items can now be found on display at the National Museum of Oman.

Source: Times of Oman [September 20, 2018]



Site in Jericho offers clues into burial rites of ancient world

The transition in burial practice and rites during different phases of the Bronze Age intrigued researchers studying the ancient site of Jericho, they recently told The Jordan Times.

Site in Jericho offers clues into burial rites of ancient world
General view of the site of Tell es-Sultan/ancient Jericho from south, with the Middle Bronze Age (1900–1550 BC)
fortification works at the southern side of the tell [Credit: Lorenzo Nigro]

Jericho contains skeletal assemblages that represent fractions of past populations from most of the different archaeological periods covering a time span from 3,500 to 586 BC, said Senior Fellow at the Research Centre for Anatolian Civilisations of Koҫ University in Istanbul Rula Nuri Shafiq.

“The collection is composed of isolated crania [skull], dentition and almost complete individuals with postcranial remains,” Shafiq continued, adding that this kind of variable skeletal representation presents a good reflection of the mortuary practices found at Jericho during the different archaeological periods.

The Jericho site is divided into two parts: Tell Es-Sultan, which represents the city-settlement itself, and the associated large cemetery that contains numerous shaft burials cut directly into limestone.

“Most of the tombs are located under housing constructions at a Palestinian refugee camp, which caused some difficulties and limitations during an excavation by Kathleen Kenyon [1906-1978] in the 1950s,” she said.

 The cemetery consists of a large number of tombs, all carved into the rock, the archaeologist elaborated, adding that the tombs are made of two parts,” the shaft and burial chamber, which both vary in size between the different archaeological periods”.

“The tomb structure usually has a vertical shaft entrance with rounded edges and a depth that varies between one to two metres. The maximum size of shaft reported by Kenyon [1957] was 4.8 metres long and 3 metres wide, with a chamber 4.5 metres in diameter,” Shafiq outlined.

After the burials were completed, the chamber was blocked by rocks, and the shafts were filled with rubble that came from carving the tombs, the scholar explained, adding that most of the periods represented at Jericho were characterised by communal burials, with the exception of the Early Bronze IV period, which was distinguished by single interments.

Site in Jericho offers clues into burial rites of ancient world
Tomb D.641 during the excavation [Credit: Lorenzo Nigro]

“Kenyon reported that the burial practices consisted of two phases: first, the deceased would be placed at the central part of the chamber with their burial goods; second, after some time, the disarticulated skeletons were removed to allow room for new interments. The skulls were collected and placed around the chamber walls, while the postcranial bones were discarded outside the tomb. Analysis of the skeletal remains showed clear evidence of cremation that was conducted inside the tombs,” Shafiq said.

Tombs dating to the Early Bronze II-III periods were partly damaged by the collapse of the roofs of the burial chambers, thus affecting the preservation of the skeletal remains, the researcher said, stressing that most of the remains were represented by only skulls and a few mixed piles of long bones.

“The Early Bronze IV period showed a striking difference in the burial practices from the preceding Early Bronze II-III and the following Middle Bronze. Early Bronze IV is the only period characterised by single interment burials. There are a few cases of double burials, but the majority are single with much smaller burial chambers than the other periods.” Shafiq elaborated.

Furthermore, several of the Early Bronze IV burials are primary but the majority are secondary as indicated by the disarticulated skeletons. Burial goods are simple with a few pots, a dagger, some beads and the remains of animal bones.

Tombs dating to the Middle Bronze II-III periods are mostly re-used Early Bronze IV burial chambers, with only a few tombs of Middle Bronze origin, the scholar said, noting that Kenyon in 1960 reported that the majority of the preserved Middle Bronze tombs showed primary articulated burials.

All Middle Bronze tombs exhibited richer burial goods and more elaborate body treatments compared to the other periods, she highlighted, saying: “Several of the tombs had the remains of wooden objects such as tables, stools, cups and bowls. There were also the remains of sheep and goat bones placed in pots evidently cooked before being placed into the tombs; and parts of these animal bones were found in full articulation with the desiccated meat still preserved. There were also remains of fruits such as pomegranates and possibly grapes [Kenyon 1960].”

“Certain tombs showed special burial treatments for certain individuals, which might be interpreted as ‘elite burials’; Several tombs showed the body of a main individual being placed on a wooden bed or a raised platform, while the remaining interments were placed just below the platform,” she emphasised.

“Generally, weapons were not a frequent find in any of these archaeological periods, with the only exception — the Early Bronze IV period — that had the highest number of weapons in the form of daggers [Kenyon 1957],” Shafiq said.

Author: Saeb Rawashdeh | Source: The Jordan Times [September 20, 2018]



Caerleon Roman Barracks Ruins, Caerleon, Newport, South Wales, 22.9.18.The barracks...

Caerleon Roman Barracks Ruins, Caerleon, Newport, South Wales, 22.9.18.

The barracks foundations show the rows of small rooms that housed eight infantry each. The slightly larger rooms at the end were for centurions. Also pictured is the communal latrine, corner tower and round ovens (last image).

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The Twelve Apostles, Australia | #Geology #GeologyPage…

The Twelve Apostles, Australia | #Geology #GeologyPage #Australia

The Twelve Apostles is a collection of limestone stacks off the shore of the Port Campbell National Park, by the Great Ocean Road in Victoria, Australia. Their proximity to one another has made the site a popular tourist attraction.

Read more & More Photos: http://www.geologypage.com/2016/05/the-twelve-apostles-australia.html

Geology Page



Fluorite | #Geology #GeologyPage #Mineral Locality: Elmwood…

Fluorite | #Geology #GeologyPage #Mineral

Locality: Elmwood Mine, Carthage, Smith Co., Tennessee, USA

Size: 6.3 x 5.9 x 5.3 cm

Photo Copyright © Anton Watzl Minerals

Geology Page



Calcite | #Geology #GeologyPage #Mineral Locality: Iraí, Alto…

Calcite | #Geology #GeologyPage #Mineral

Locality: Iraí, Alto Uruguai region, Rio Grande do Sul, Brazil

Size: 7.1 x 6.7 x 4.7 cm

Photo Copyright © Anton Watzl Minerals

Geology Page



Calcite with Chalcosite | #Geology #GeologyPage #Mineral Size:…

Calcite with Chalcosite | #Geology #GeologyPage #Mineral

Size: 8 x 5.5 x 4 cm

Photo Copyright © Anton Watzl Minerals

Geology Page



Ajoite | #Geology #GeologyPage #Mineral Locality: Messina…

Ajoite | #Geology #GeologyPage #Mineral

Locality: Messina District, Limpopo Province, South Africa

Size: 12 x 9 x 8 cm

Photo Copyright © Anton Watzl Minerals

Geology Page



Tour Percée | #Geology #GeologyPage #France The Tour Percée…

Tour Percée | #Geology #GeologyPage #France

The Tour Percée double arch, also named the Tour Isabelle arch, is a double natural arch, located in the Parc Naturel Régional de la Chartreuse, Chartreuse Mountains, France.

Its span is 32 metres (105 ft), which makes it the biggest natural arch in the Alps.

Geology Page



Old women in traditional dress, the Aran Islands, IrelandPhoto ©…

Old women in traditional dress, the Aran Islands, Ireland

Photo © David Shaw


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Sunlight and shadows, Balltinglass Abbey, Wicklow

Sunlight and shadows, Balltinglass Abbey, Wicklow

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Fairy ring…… the remains of a Neolithic tomb at…

Fairy ring…… the remains of a Neolithic tomb at Carrowmore, Co Sligo

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This bronze pendant of a Viking axe is decorated in a complex…

This bronze pendant of a Viking axe is decorated in a complex design which is inspired by Norse art. Available here: Viking Axe Pendant 

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Stone cross, Cashel, Co. Tipperary, Ireland Photo:  Andrzej…

Stone cross, Cashel, Co. Tipperary, Ireland 

Photo:  Andrzej Staszok

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The Dingle peninsula, Co. Kerry, Ireland 

The Dingle peninsula, Co. Kerry, Ireland 

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This silver Tree of Life pendant features a spreading oak and it…

This silver Tree of Life pendant features a spreading oak and it comes with a silver chain. There are seven noble trees in Celtic mythology: oak, apple, yew, pine, hazel, holly and ash – each with its own spiritual meaning.

Of these the oak tree was considered the most sacred and is described in the medieval Irish text, The Book of Ballymote thus: ‘The oak tree of the Druids is king of trees. The wren, bird of the Druids and king of the birds, is the soul of the oak’.

Available here: Celtic Tree of Life Pendant 

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The Augustinian Friary in Adare, Co Limerick. Also known as the…

The Augustinian Friary in Adare, Co Limerick. Also known as the Black Abbey, it was founded in AD 1316


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Sunset over Dunamase Castle, IrelandSource

Sunset over Dunamase Castle, Ireland


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Hit-and-run heist of water by terrestrial planets in the early solar system

A study simulating the final stages of terrestrial planet formation shows that ‘hit-and-run’ encounters play a significant role in the acquisition of water by large protoplanets, like those that grew into Mars and Earth. The results will be presented by Christoph Burger at the European Planetary Science Congress (EPSC) 2018 in Berlin.

Hit-and-run heist of water by terrestrial planets in the early solar system
Artist’s concept of a celestial body about the size of the moon colliding with a body the size of Mercury
[Credit: NASA/JPL-Caltech]

Four and a half billion years ago, the inner Solar System was a chaotic place with around 50-100 protoplanets ranging in size from the Moon to Mars that were prone to giant collisions. Bodies that formed within what is now the orbit of Mars contained no water as the conditions were too hot for volatile material, like water or methane, to condense. For water to make its way onto the developing terrestrial planets, water needed to be delivered from outside this region via a sequence of collisions.

Burger and colleagues from the University of Vienna and Tübingen have used high-resolution simulations to track the fate of water and other materials through a series of different impact scenarios. Outcomes of collisions could include bodies sticking together, material being lost, or being redistributed between the two objects. The results depend on various factors like the speed and angle of impact, the difference in mass between the bodies and their total mass.

“We found that ‘hit-and-run’ collisions, where the impact is off-centre and the bodies have enough speed to separate again after the encounter, are very common. In these scenarios, tens of percent of water can be transferred between the colliding bodies or ejected and lost entirely,” said Burger.

The smaller of the colliding pair is often modified down to the core and effectively stripped of water, while the more-massive body remains more-or-less unaltered. The team is now focusing on how long chains of successive collisions affect the evolution of a disk of planetesimals and protoplanets.

Hit-and-run heist of water by terrestrial planets in the early solar system
Snapshots from the simulations illustrating water transfer and loss in a typical hit-and-run encounter.
The blue and white colours represent water on the initial bodies, while red is rocky
material from their interiors [Credit: Burger et al.]

“Recent research shows that comets can only account for a small fraction of the terrestrial planets’ water. These giant collisions early in the Solar System’s history must also be a major source. Our results strongly suggest we need to track the water in both survivors following hit-and-run encounters. This will help us predict the properties of planets that form as the end-product of a long sequence of successive collisions,” said Burger.

Source: Europlanet [September 19, 2018]



Mercury and its depressions

One of the most surprising discoveries of the NASA’s Messenger mission was the presence of unusual, bright, irregular and rimless flat-floored depressions on the surface of Mercury. These depressions, called hollows, are usually found on crater walls, rims, floors and central peaks.

Mercury and its depressions
One of the three craters, the Canova crater, hosting hollows analyzed in this work
[Credit: NASA]

Since the hollows appear fresh, they may be actively forming today through a mechanism that could involve the loss of volatile compounds, but understanding how the hollows formed is still a major challenge for scientists.

In a new study published in Journal of Geophysical Research: Planets, a journal of the American Geophysical Union, lead author Alice Lucchetti and her Italian team analyzed the nature of Mercury’s hollows inside three different impact craters: Dominici, Canova and Velazquez. The new study focuses understanding the geomorphology and compositional mineralogy of the hollows through the use of multi-color images acquired from the Mercury Dual Imaging System, or MDIS, instrument.

“We performed detailed geological mapping of the craters hosting hollows, making use of high- resolution images, in order to fully characterize the geological framework where these features formed.” Lucchetti said.

The researchers separated the craters’ areas into different units characterized by their spectral behavior. Comparing the results coming from the geomorphological and spectral analysis, we revealed a strong correlation between the spectral units and those identified in high-resolution geological maps,” Lucchetti said.

Mercury and its depressions
Comparison between the geological map and the spectral analysis for Canova crater.
Hollows are identified by a well-defined spectrum (cluster #9)
[Credit: Lucchetti et al.]

The new research shows the hollows in all three craters show a similar, well-defined, visible spectrum. When this spectrum is compared with laboratory spectra, it is indicative of a mixture of different materials.

“We found that both sulfides and pyroxene presenting transitional elements are responsible for the hollows absorption presented in the spectra,” Lucchetti said. “This provides new insights into the hollows’ nature and composition, suggesting that hollows terrains are the expression of not only the remnant material coming from a process that involve devolatilization, but also of the bedrock-forming material in which the hollows formed.”

This work is important to scientists’ overall understanding of the hollows.

“We are already studying other regions of Mercury to understand if it is a common behavior of these features or if different terrains affect their formation in different ways,” she said.

The hollows will also be one of the main targets of interest of the upcoming European Space Agency and Japan Aerospace Exploration Agency BepiColombo mission, which will be launched in mid-October.

Author: Alice Lucchetti | Source: American Geophysical Union [September 19, 2018]



Moderate warming could melt East Antarctic Ice Sheet

Parts of the world’s largest ice sheet would melt if Antarctic warming of just 2°C is sustained for millennia, according to international research.

Moderate warming could melt East Antarctic Ice Sheet
These are researchers at dusk on the research vessel JOIDES Resolution, on expedition to Antarctica
[Credit: IODP Imaging Office]

University of Queensland scientist Dr Kevin Welsh was part of a team that used evidence from warm periods in Earth’s history to see how the East Antarctic Ice Sheet might react to a warming climate.

Dr Welsh said marine sediment layers indicated the ice sheet had retreated during warming in the late Pleistocene period, when temperatures were like those predicted for this century.

“Antarctica is around twice the size of Australia, with ice sheets several kilometres thick and containing around half of the world’s fresh water,” he said.

“The East Antarctic Ice Sheet covers about two thirds of the area, and because its base is largely above sea level it was generally thought to be less sensitive to warming climates than the adjacent West Antarctic Ice Sheet.

Moderate warming could melt East Antarctic Ice Sheet
These are researchers taking in the sights on the research vessel JOIDES Resolution, on expedition to Antarctica
[Credit: IODP Imaging Office]

“However, some areas — like the Wilkes Land Subglacial Basin, directly south of Australia — are below sea level and contain enough ice to raise global sea levels by several metres.

“The evidence we have suggests that with the predicted 2°C warming in Antarctica — if sustained over a couple of millennia — the sheet would start melting in these locations.”

Dr Welsh, from UQ’s School of Earth and Environmental Sciences, said the team chemically analysed layers of sediment deposited on the Southern Ocean floor by glaciers.

“We found that the most extreme changes in the ice sheet occurred during two interglacial periods 125,000 and 400,000 years ago, when global sea levels were several metres higher than they are today,” he said.

Moderate warming could melt East Antarctic Ice Sheet
An iceberg floats in the distance [Credit: IODP Imaging Office]

“These periods could be analogues for future climates and it seems likely that ice loss from the East Antarctic Ice Sheet contributed to those higher sea levels.

“Ice loss contributes to rising global sea levels which are a threat to many coastal communities, and making projections requires a solid understanding of how sensitive these ice sheets are.”

Imperial College London researcher Dr David Wilson said the findings were extremely concerning for humanity.

“With current global temperatures already one degree higher than during pre-industrial times, future ice loss seems inevitable if we fail to reduce carbon emissions,” Dr Wilson said.

The findings are published in the journal Nature.

Source: University of Queensland [September 19, 2018]




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