воскресенье, 9 сентября 2018 г.

Mysterious ‘lunar swirls’ point to moon’s volcanic, magnetic past

The mystery behind lunar swirls, one of the solar system’s most beautiful optical anomalies, may finally be solved thanks to a joint Rutgers University and University of California Berkeley study. The solution hints at the dynamism of the moon’s ancient past as a place with volcanic activity and an internally generated magnetic field. It also challenges our picture of the moon’s existing geology.

Mysterious 'lunar swirls' point to moon's volcanic, magnetic past
Sonia Tikoo, an assistant professor in Rutgers-New Brunswick’s Department of Earth and Planetary Sciences,
looks at moon rock samples in a Petri dish [Credit: Nick Romanenko/Rutgers University]

Lunar swirls resemble bright, snaky clouds painted on the moon’s dark surface. The most famous, called Reiner Gamma, is about 40 miles long and popular with backyard astronomers. Most lunar swirls share their locations with powerful, localized magnetic fields. The bright-and-dark patterns may result when those magnetic fields deflect particles from the solar wind and cause some parts of the lunar surface to weather more slowly.

“But the cause of those magnetic fields, and thus of the swirls themselves, had long been a mystery,” said Sonia Tikoo, coauthor of the study recently published in the Journal of Geophysical Research – Planets and an assistant professor in Rutgers University-New Brunswick’s Department of Earth and Planetary Sciences. “To solve it, we had to find out what kind of geological feature could produce these magnetic fields – and why their magnetism is so powerful.”

Working with what is known about the intricate geometry of lunar swirls, and the strengths of the magnetic fields associated with them, the researchers developed mathematical models for the geological “magnets.” They found that each swirl must stand above a magnetic object that is narrow and buried close to the moon’s surface.

The picture is consistent with lava tubes, long, narrow structures formed by flowing lava during volcanic eruptions; or with lava dikes, vertical sheets of magma injected into the lunar crust.

Mysterious 'lunar swirls' point to moon's volcanic, magnetic past
This is an image of the Reiner Gamma lunar swirl from NASA’s Lunar Reconnaissance Orbiter
[Credit: NASA LRO WAC science team]

But this raised another question: How could lava tubes and dikes be so strongly magnetic? The answer lies in a reaction that may be unique to the moon’s environment at the time of those ancient eruptions, over 3 billion years ago.

Past experiments have found that many moon rocks become highly magnetic when heated more than 600 degrees Celsius in an oxygen-free environment. That’s because certain minerals break down at high temperatures and release metallic iron. If there happens to be a strong enough magnetic field nearby, the newly formed iron will become magnetized along the direction of that field.

This doesn’t normally happen on earth, where free-floating oxygen binds with the iron. And it wouldn’t happen today on the moon, where there is no global magnetic field to magnetize the iron.

But in a study published last year, Tikoo found that the moon’s ancient magnetic field lasted 1 billion to 2.5 billion years longer than had previously been thought – perhaps concurrent with the creation of lava tubes or dikes whose high iron content would have become strongly magnetic as they cooled.

“No one had thought about this reaction in terms of explaining these unusually strong magnetic features on the moon. This was the final piece in the puzzle of understanding the magnetism that underlies these lunar swirls,” Tikoo said.

The next step would be to actually visit a lunar swirl and study it directly. Tikoo serves on a committee that is proposing a rover mission to do just that.

The findings are published in Journal of Geophysical Research: Planets.

Source: Rutgers University [September 06, 2018]



From dust to pebbles to planets – insight into the birth of a solar system

Detailed simulations of planetary formation are revealing how tiny grains of dust turn into giant planets and could shed light on where to find new Earth-like worlds.

From dust to pebbles to planets – insight into the birth of a solar system
Scientists are working out how cosmic dust turns into hard, spherical pebbles which can then develop into planets
[Credit: NASA/JPL-Caltech]

Scientists theorise that planets form from rotating discs of gas that surround newly formed stars, known as proto-planetary discs. Pebble-sized objects in these discs then clump together to form cores of would-be planets.

Professor Anders Johansen from Lund University in Sweden, has gone right down to the level of atomic nuclei and molecules to try and work out how cosmic dust particles stick together in pebbles and then turn into baby planets, known as planetesimals.

“Planet formation takes place when these dust particles collide, and they grow to larger and larger sizes,” he said. “This growth takes us then from micrometres, all the way up to 10,000 kilometres or so.”

One clue to how this dust forms into pebbles can be found on Earth in meteorites – pieces of asteroids that are leftovers from the formation of the solar system.

“There’s a mystery in there,” Prof. Johansen said. “If you look inside an asteroid, you do find millimetre-sized pebbles, which is fine. But the problem with those pebbles is they are not what we expect them to be. We would expect them to be fluffy dust aggregates, a bit like if you have a sandbox after it rains, and you can pick up a piece of dried out sand that is very fragile,” he said.

Instead, the pebbles are spherical and hard, like they have been heated and cooled – similar to objects that have been struck by lightning.

“Lightning takes place as thunderclouds discharge their electric charge to the ground,” said Prof. Johansen. “This discharge is very similar to the shock you experience from the static electricity when you put on a jumper.”

Prof. Johansen theorised that there must be a mechanism during planet formation that creates positively and negatively charged particles, and he and his team investigated what that was.

“While a thundercloud obtains a charge difference between its top and bottom by falling hail particles, we found that in the protoplanetary disc the decay of a radioactive element called Aluminium-26 is very efficient at charging dust clouds,” he said.

Chemical composition

The finding was part of a project called PLANETESYS, which is using computer simulations to replicate the physical processes taking place when planets form – all the way from dust to a planetary system. It includes details about the chemical composition of each pebble.

One thing Prof. Johansen can examine from looking at this chemical composition is how planets accrete water – a vital ingredient for life.

“An obvious question is, “How much water does a planet get?” We can begin to speculate about if it’s normal to get the Earth’s amount of water, if it’s a lot of water or a little bit. But maybe you can also get too much water, which may be good for life but not good for civilisations,” he said.

Dr. Bertram Bitsch from the Max Planck Institute for Astronomy in Heidelberg, Germany, says that understanding more about how planets arise would help identify potentially habitable planets elsewhere in the universe.

“If you understand more (about) the formation process of how we can make a system like the solar system, then we can maybe make predictions (about) how often these systems would exist and how common it would be to find Earth-like planets (orbiting) other stars.”

“Then, if we see a certain composition of the system … that might allow us to see that there might be habitable planets in those systems.”


Dr. Bitsch thinks he might know the recipe for how solar systems end up with Earth-like planets. With a careful blending of conditions, from where baby planets form, to their chemical composition and gravitational interactions, he can try to model the conditions to generate solar systems with habitable planets.

But figuring out the right recipe requires working backwards after running many simulations with complex supercomputing power, which he’s doing in a project called PAMDORA which runs until 2022.

“I want to use computer simulations … where we look at the gravitational interactions between multiple bodies to model the stages from planetesimals all the way to fully formed planetary systems with terrestrial planets, super Earths, and gas giants,” he said.

In his simulations, Dr. Bitsch looks at the how pebbles in the swirling discs form into moon-size planetary embryos, which then develop into fully formed planets.

Altering the different mechanisms at work can influence what types of planets a solar system may end up with.

“There are many different pathways that can happen, and many different parameters that can influence the outcome of the simulations,” he said. “For example, how big are the pebbles, how many would there be, and where would your initial planetesimals form that would then start to form proto-planets?”

To see which variables matter most, he runs hundreds of computer simulations that last weeks at a time and can simulate tens of millions of years to model the highly chaotic meetings of multiple objects.

For Earth-like planets, one key factor is how close baby planets form to their home star, since the difference in temperature can determine if planets accrete water directly during the gas-disc stage or from a late water delivery from asteroids or comets, like for our own Earth.

“One thing that is already in the code is looking at the composition of super-Earths. For example, are they rocky or dominated by water-ice?” Dr. Bitsch said.

Super-Earths, which are planets like the Earth, but maybe two to ten times more massive, don’t exist in our solar system, but are relatively common among other stars.

“Lots of super-Earths have been found and detected, and the question is what are they made of? This can give us the answer to where they have been formed.”

Author: Ethan Bilby | Source: Horizon: The EU Research & Innovation Magazine [September 06, 2018]



Galactic ‘wind’ stifling star formation is most distant yet seen

For the first time, a powerful “wind” of molecules has been detected in a galaxy located 12 billion light-years away. Probing a time when the universe was less than 10 percent of its current age, University of Texas at Austin astronomer Justin Spilker’s research sheds light on how the earliest galaxies regulated the birth of stars to keep from blowing themselves apart.

Galactic 'wind' stifling star formation is most distant yet seen
An artist impression of an outflow of molecular gas from an active star-forming galaxy
[Credit: NRAO/AUI/NSF, D. Berry]

“Galaxies are complicated, messy beasts, and we think outflows and winds are critical pieces to how they form and evolve, regulating their ability to grow,” Spilker said.

Some galaxies such as the Milky Way and Andromeda have relatively slow and measured rates of starbirth, with about one new star igniting each year. Other galaxies, known as starburst galaxies, forge hundreds or even thousands of stars each year. This furious pace, however, cannot be maintained indefinitely.

To avoid burning out in a short-lived blaze of glory, some galaxies throttle back their runaway starbirth by ejecting — at least temporarily — vast stores of gas into their expansive halos, where the gas either escapes entirely or slowly rains back in on the galaxy, triggering future bursts of star formation.

Until now, however, astronomers have been unable to directly observe these powerful outflows in the very early universe, where such mechanisms are essential to prevent galaxies from growing too big, too fast.

Spilker’s observations with the Atacama Large Millimeter/submillimeter Array (ALMA), show — for the first time — a powerful galactic wind of molecules in a galaxy seen when the universe was only 1 billion years old. This result provides insights into how certain galaxies in the early universe were able to self-regulate their growth so they could continue forming stars across cosmic time.

Astronomers have observed winds with the same size, speed and mass in nearby starbursting galaxies, but the new ALMA observation is the most distant unambiguous outflow ever seen in the early universe.

Galactic 'wind' stifling star formation is most distant yet seen
ALMA, aided by a gravitational lens, imaged the outflow, or ‘wind,’ from a galaxy seen when the universe was only one
billion years old. The ALMA image (circle call out) shows the location of hydroxyl (OH) molecules. These molecules trace
 the location of star-forming gas as it is fleeing the galaxy, driven by either supernovas or a black-hole powered ‘wind.’ The
 background star field (Blanco Telescope Dark Energy Survey) shows the location of the galaxy. The circular, double-lobe
 shape of the distant galaxy is due to the distortion caused by the cosmic magnifying effect of an intervening galaxy
[Credit: ALMA (ESO/NAOJ/NRAO), J. Spilker/UT-Austin; NRAO/AUI/NSF, S. Dagnello; AURA/NSF]

The galaxy, known as SPT2319-55, is more than 12 billion light-years away. It was discovered by the National Science Foundation’s South Pole Telescope.

ALMA was able to observe this object at such tremendous distance with the aid of a gravitational lens provided by a different galaxy that sits almost exactly along the line of sight between Earth and SPT2319-55. Gravitational lensing — the bending of light due to gravity — magnifies the background galaxy to make it appear brighter, which allows the astronomers to observe it in more detail than they would otherwise be able to. Astronomers use specialized computer programs to unscramble the effects of gravitational lensing to reconstruct an accurate image of the more-distant object.

This lens-aided view revealed a powerful wind of star-forming gas exiting the galaxy at nearly 800 kilometers per second. Rather than a constant, gentle breeze, the wind is hurtling away in discrete clumps, removing the star-forming gas just as quickly as the galaxy can turn that gas into new stars.

The outflow was detected by the millimeter-wavelength signature of a molecule called hydroxyl (OH), which appeared as an absorption line: essentially, the shadow of an OH fingerprint in the galaxy’s bright infrared light.

Molecular winds are an efficient way for galaxies to self-regulate their growth, the researchers note. These winds are probably triggered by either the combined effects of all the supernova explosions that go along with rapid, massive star formation, or by a powerful release of energy as some of the gas in the galaxy falls down onto the supermassive black hole at its center.

“So far, we have only observed one galaxy at such a remarkable cosmic distance, but we’d like to know if winds like these are also present in other galaxies to see just how common they are,” Spilker concluded. “If they occur in basically every galaxy, we know that molecular winds are both ubiquitous and also a really common way for galaxies to self-regulate their growth.”

The research is published in the journal Science.

Source: University of Texas at Austin [September 06, 2018]



2018 September 9 M1: The Crab Nebula from Hubble Image Credit:…

2018 September 9

M1: The Crab Nebula from Hubble
Image Credit: NASA, ESA, Hubble, J. Hester, A. Loll (ASU)

Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula’s very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

∞ Source: apod.nasa.gov/apod/ap180909.html

Study reveals impact of habitat fragmentation on migrant birds

Experts at the University of Stirling have shed new light on the impact of habitat fragmentation on migrant birds.

Study reveals impact of habitat fragmentation on migrant birds
Willow warbler [Credit: Andreas Trepte/WikiCommons]

Scientists used audio technology to analyse the behaviour of willow warblers, after spring migration, in 23 woodland patches across Scotland and England. While the patches were of a similar size, the landscapes in which they were located had differing amounts of available habitat.

Significantly, the study found that migrant male willow warblers arrived earlier in woodland patches when there was less habitat in the surrounding landscape, within a 2km radius.

The team also found that an individual’s decision to remain in a patch after initial colonisation depended on patch quality, as measured by vegetation characteristics. In particular, birds preferred to stay in woodlands with a relatively open understorey, also known as undergrowth.

Robin Whytock, of the Faculty of Natural Sciences, led the work as part of his PhD alongside colleagues at the University, Professor Kirsty Park, Dr Elisa Fuentes-Montemayor and co-supervisor Dr Kevin Watts at Forest Research.

“Habitat fragmentation and loss has changed how animals move through landscapes and use the remaining habitat,” Dr Whytock said. “Whether an animal colonises a fragmented habitat patch – for example, a small woodland – depends on a variety of factors, including the content of the surrounding landscape and the quality of the patch itself.

“This study gives a valuable insight into how habitat fragmentation affects the behaviour of even very mobile species, such as migrant birds.

“Our results support prior research in aquatic study systems that have looked at colonisation of artificial reefs and ponds – and, as far as we know, this is the first time that the patterns observed in our study have been observed over such large spatial scales and with such a highly mobile species.”

The scientists conducted the study in spring 2016 to focus on the spring migration of the willow warbler, which migrates bi-annually between northern Europe and sub-Saharan Africa.

They combined the latest bio-acoustic technology – which recorded the first song dates of male willow warblers – with Stirling’s unique Woodland Creation and Ecological Networks (WrEN) project to test how the amount of habitat in a regional landscape affects colonisation timing of isolated woodland patches.

On analysing the audio data, the team found first song dates were on average five days earlier in patches with five percent woodland cover in the landscape, when compared to patches with around 30 percent cover.

Dr Whytock added: “These findings are particularly interesting when you consider that previous research has suggested this species benefits from large expanses of woodland during migration. Therefore, it’s surprising that individuals should choose to settle earlier in isolated woodlands.”

He said further work is now required to examine whether this has consequences for the survival and reproduction of willow warblers.

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

Source: University of Stirling [September 06, 2018]



Unravelling the reasons why mass extinctions occur

Scientists from the University of Leicester have shed new light on why mass extinctions have occurred through history — and how this knowledge could help in predicting upcoming ecological catastrophes.

Unravelling the reasons why mass extinctions occur
University of Leicester research could help to predict approaching ecological catastrophes
[Credit: University of Leicester]

The international team has investigated sudden ecological transitions throughout history, from mass mortality events in the far past to more recent extinctions which have occurred over the last few decades.

In a paper published in the journal Science, co-authored by Professor Sergei Petrovskii and Dr Andrew Morozov from the University of Leicester’s Department of Mathematics, and a group of leading scientists from the USA and Canada, the team has explored the long-standing mystery of why these ecological transitions occur.

Ecological systems sometimes experience sudden changes in their properties or function which often results in species extinction and significant loss of biodiversity.

Understanding why these significant changes occur remains a challenge, in particular because transitions often happen under apparently steady, constant conditions and therefore cannot be directly linked to a specific environmental change.

By bringing together empirical data, insights from ecological theory and mathematical models, the team has revealed that abrupt transitions in an ecosystem can occur as a result of long-term transient dynamics, including ‘ghost attractors’ and ‘crawl-bys’.

An attractor is an ‘end-state’ of a given ecosystem, that is where it expected to be found over an infinitely long period of time and/or where it returns after small perturbations.

A ‘ghost attractor’ is a special configuration of a dynamical system that exhibits the same behaviour as an attractor but only for a finite time within an ecosystem. After that time, the system would normally experience a fast evolution or transition to another state which can have very different properties. Such transition would therefore correspond to a catastrophe or major ecological shift.

‘Crawl-bys’, on the other hand, exist when changes to the dynamic of an ecosystem happen slowly over a long period of time.

Professor Petrovskii explained: “An ecological catastrophe emerging from a ‘ghost attractor’ or a ‘crawl-by’ may be a debt that we have to pay for the actions or mistakes — for example unsustainable use of natural resources — made many generations ago.

“Our research shows that a healthy ecosystem will not necessarily remain healthy, even in the absence of any significant environmental change. Therefore, better monitoring of the state of an ecosystem is required to mitigate potential disasters.

“We also can predict an approaching catastrophe in the sense that our study advises where to look for its signs and what is the relevant time scale: the environmental change (whether it is natural or human-made) that will finally lead to big changes might have happened a very long time ago.

“These findings create a new paradigm as well as a powerful theoretical framework for understanding — and potentially predicting — ecological catastrophes and for their efficient management.”

Source: University of Leicester [September 06, 2018]



Bird bacteria study reveals evolutionary arms race

A study of a songbird and a bacterium that infects it has revealed how species in conflict evolve in response to each other.

Bird bacteria study reveals evolutionary arms race
Healthy house finches [Credit: Geoff Hill, Auburn University]

University of Exeter researchers found North American house finches developed greater resistance to a bacterial pathogen (Mycoplasma gallisepticum) thereby pushing the pathogen to become more virulent.

This process – known as “host-pathogen coevolution” – is believed to play a key role in evolution, but until now evidence for it has been scarce. “Our results show how these competitors respond to each other over time,” said Dr Camille Bonneaud, of the Centre for Ecology and Conservation on the University of Exeter’s Penryn Campus in Cornwall.

“As the finches evolve better resistance to the pathogen, the pathogen becomes more potent to overcome these defences. “It is widely assumed that animals – including humans – coevolve with their infectious pathogens and become ever more resistant, but in fact most direct evidence for this comes from studies of bacteria and their viral pathogens.

Bird bacteria study reveals evolutionary arms race
Healthy house finches [Credit: Geoff Hill, Auburn University]

“In this study we show how a pathogen can shape evolution in a vertebrate and how this has consequences for the pathogen.”

The research, supported by universities in Alabama (Auburn University) and Arizona (Arizona State University), was made possible by differences in finch populations in these two US states. House finches in Arizona have not been exposed to Mycoplasma gallisepticum, while those in Alabama have been exposed to it for over 20 years.

Researchers found that exposure to the pathogen led to eye swelling in birds from both states, but that resistant Alabama birds were three times less likely to show symptoms that would lead to death in the wild.

Bird bacteria study reveals evolutionary arms race
House finch with severe symptoms of conjunctivitis [Credit: Geoff Hill, Auburn University]

Similarly, the pathogen evolved to become better able to infect and transmit as the birds became more resistant. The findings have implications for our knowledge of diseases that affect humans.

Dr Bonneaud explained: “The Plague and more recently the pandemic of HIV are sobering reminders of the impacts that emerging infectious diseases can have on us. “We know that we can see the signature of such impacts on our genome.

“This study provides a direct demonstration that these outbreaks can shape our evolution and that how we respond will, in turn, shape the evolution of our infectious pathogens.”

The paper is published in the journal Current Biology.

Source: University of Exeter [September 06, 2018]



Elucidating the Chara genome: Implications for emergence of land plants in Paleozoic era

Land plants dominate terrestrial flora, and our foodstuff heavily depends on them. How land plants evolved from aquatic algae has been a problem attracting much scientific attention. In 2011, Dr. Nishiyama, one of the present authors published an article in collaboration with other researchers comparing Chlamydomonas reinhardtii, the moss Physcomitrella patens, a spikemoss species (Selaginella moellendorffii) and the thale cress (Arabidopsis thaliana). The comparison revealed that, after the separation of the ancestor of land plants from Chlamydomonas, a number of genes were acquired before the diversification of land plants. However, Chlamydomonas and land plants are distantly related with a divergence time of a billion years, so the genome sequences of green algae, closer to land plants, was of clear interest.

Elucidating the Chara genome: Implications for emergence of land plants in Paleozoic era
Left: Thallus with a stem-like structure (axes) with whorls of branch-like structures (called branchlets), looking like
a wheel. Scale bar, 100 µm. Right: Sexual reproductive organs formed on a branchlet. Upper, an oogonium;
lower, an antheridium [Credit: Prof. Sakayama, Kobe University]

In 2014, Dr. Hori and others lead by Prof. Ohta at Tokyo Institute of Technology published the genome sequence of Klebsormidium nitens, a filamentous green alga closer to land plants than Chlamydomonas; they showed that Klebsormidium nitens has genes important for living on land equivalent to those of land plants.

Three groups of green algae are evolutionarily closer to land plants than Klebsormidiophyceae, that is, Charophyceae, Coleochaetophyceae and Zygnematophyceae. Among them, the Charophyceae form the most complex bodyplan with reproductive organs, antheridia and oogonia. In fact, Pringsheim, in the 1860s, already suggested that Chara (presently placed in Charophyceae) is closely related to land plants.

Zygnematophyceae are considered to be the extant lineage closest to land plants, but they have a sexual reproduction system, in which gametes (reproductive cells) that are almost equal in size fuse to form zygotes, rather than with a large egg and a small swimming sperm cell. In the present study, we reveal the genome of Chara braunii), which is considered to have separated from land plants 550 to 750 million years ago.

Here, 60 researchers from 40 institutions of 13 countries participated in the genome analysis of Chara braunii, a representative of Charophyceae). They have obtained a draft genome sequence, which is practically sufficient for comparison with the genomes of other organisms. The draft genome sequence is deposited at the DNA Data Bank of Japan (DDBJ)) and available through the International Nucleotide Sequence Database Collaboration (INSDC).

This study was originated by the researchers at Kanazawa University and Kobe University. Chara braunii individuals were collected at Lake Kasumigaura, Ibaraki and at Saijo city, Ehime, Japan. Strains were established, free from other algae, which can be grown in laboratories, and used for genome analysis. The genome size was estimated to be large (about 2 Gbp, about two-thirds of the human genome). Illumina next generation sequencers at the National Institute of Genetics, Japan, were used for most of genome sequencing.

After assembling raw sequences into scaffolds, the scaffold sequences that appeared to have originated from bacteria were excluded, and 1.75 Gbp of scaffold sequences were obtained. cDNA (mRNA was reverse transcribed into complementary DNA) was cloned in Escherichia coli at the University of Tokyo and the resulting library was randomly selected and sequenced by a conventional sequencer to produce short sub-sequences (referred to as expressed sequence tag, EST). These data were used together with the high-throughput sequence data obtained from cDNA by using Illumina next generation sequencers at the University of Tokyo and another data obtained from cDNA by the European group to predict the genes contained, and 35,422 gene structures were estimated.

Elucidating the Chara genome: Implications for emergence of land plants in Paleozoic era
Lineages with published genomes are shown with bold lines. Chara braunii, whose genome is described in
 the present study, represents the earliest diverging lineage to land plants in the Phragmoplastophyta
[Credit: Kanazawa University]

The last common ancestor of Charophyceae and land plants was estimated, in this study, to possess all the genes known from land plants for cell division except one, TANGLED1. Among the genes known to be involved in the phytohormone biosynthesis and responses of land plants, Chara braunii was found to possess all the genes involved in the ethylene signaling system, while Klebsormidium nitens lacks one gene, EIN2. In addition, Chara braunii is found to have genes encoding Aux/IAA and ARF, transcription factors (genes that regulate expression of other genes) involved in the auxin response.

These genes were not found in Klebsormidium nitens. On the other hand, since the TIR1-type receptor is not found in either Chara braunii or in Klebsormidium nitens, there may be unknown mechanisms acting in auxin response. Receptors for abscisic acid (PYR), jasmonic acid, and salicylic acid were not identified, indicating that the receptors found in land plants were probably gained after separation of Charophyceae and land plants. Furthermore, Chara braunii has an ortholog of GUN1, a key of the system to regulate the synthesis of chloroplast proteins by the “retrograde-” signaling from chloroplast to nucleus as seen in land plants. Chara braunii possesses more transcription factors than other green algae whose genomes have been determined.

The morphological complexity of Charophyceae may have originated from expansion of gene families after separation from land plants; thus such expansion should be independent from that of land plants. In particular, reactive oxygen species (ROS) gene network, LysM receptor-like kinases and expansion of trihelix transcription factor families should be noted. Transcriptomic analysis of sexual reproductive structures reveals intricate control by transcription factors, activity of the ROS gene network, and proteins involved in storage of nutrients and the ancestral use of plant-like storage and stress protection proteins in the zygote.

These analyses based on the Chara braunii draft genome sequence show that a variety of traits important for land plants for their terrestrial life already exist in the common ancestors of Charophyceae and land plants, which reveals that those traits peculiar to land plants were acquired before the emergence of the oldest land plants.

The present study successfully revealed the genome sequence of Chara braunii. This sequence will be referred to in developmental and genetic studies in land plants, and contribute to understanding the evolution of land plants. Since Chara cells are so large, they have been used for electrophysiological studies using a micro-electrode to measure the membrane potential. Knowledge of its genome will be beneficial understanding the molecular mechanisms underlying such physiological parameters.

In addition, Chara braunii is a cosmopolitan species distributed widely around the globe except in Antarctica and is ecologically adapted to a variety of environments. The Chara braunii strains used in this study were collected at Lake Kasumigaura, Ibaraki and at Saijo city, Ehime, Japan. The one from Lake Kasumigaura appears to be adapted to shallow water with abundant light, while the one from Saijo city is apparently adapted to deep water with lower light levels. By studying the genome sequences in relation to different environmental conditions, it may be possible to analyze and elucidate adaptation mechanisms.

The research is published in the journal Cell.

Source: Kanazawa University [September 06, 2018]



Adaptable lizards illustrate key evolutionary process proposed a century ago

Side-blotched lizards in most of the Mojave Desert have tan and brown markings that blend in well with their desert surroundings. On the Pisgah Lava Flow, however, one finds a very different population of side-blotched lizards, as black as the rocks they live on.

Adaptable lizards illustrate key evolutionary process proposed a century ago
A male lizard from the Pisgah Lava Flow photographed five days after collection in the field (left),
and the same lizard (right) after being housed for four months in the lab on light-colored sand
[Credit: Corl et al., Current Biology, 2018]

How do animals invade new environments different from the ones for which evolution has equipped them with finely tuned adaptations? Light-colored lizards on a lava flow should be easy picking for predators, so how did they survive long enough to evolve darker coloration?

One explanation has been that many of an animal’s traits are not fixed, but can change during its lifetime. This “phenotypic plasticity” enables individual animals to alter their appearance or behavior enough to survive in a new environment. Eventually, new adaptations promoting survival arise in the population through genetic changes and natural selection, which acts on the population over generations. This is known as the “Baldwin effect” after the psychologist James Mark Baldwin, who presented the idea in a landmark paper published in 1896.

Scientists studying the side-blotched lizards on the Pisgah Lava Flow have now documented this process in meticulous detail. They showed how individual lizards can change colors in a new environment to become darker on lava; they identified genes that regulate coloration and that differ between populations on and off the lava; and they found that the genetic changes in the population adapted to the lava flow make those lizards darker than others. Their findings, published in Current Biology, may be the most detailed example of the Baldwin effect occurring in a wild population.

“It’s an old and very powerful idea, and now we have genetic evidence of how it happens in the wild,” said coauthor Barry Sinervo, professor of ecology and evolutionary biology at UC Santa Cruz.

Sinervo has been studying side-blotched lizards in California for more than 30 years. First author Ammon Corl, who earned his Ph.D. in Sinervo’s lab, is now at UC Berkeley’s Museum of Vertebrate Zoology. Corl said he first learned of the Pisgah lizard population from an unpublished Ph.D. thesis by coauthor Claudia Luke, now at Sonoma State University.

Adaptable lizards illustrate key evolutionary process proposed a century ago
The Pisgah Lava Flow in the Eastern Mojave Desert [Credit: Corl et al., Current Biology, 2018]

“Claudia figured out how plastic their coloration is, and I tested for genetic changes that affected coloration in the Pisgah population,” Corl said. “Baldwin predicted that plasticity allows organisms to colonize new environments, and they then develop new adaptations through natural selection. Until now, however, we have lacked the genetic tools to show this is going on in a field setting.”

When researchers move side-blotched lizards from one background to another (for example, from sand to lava rock), changes in coloration start to appear within a week, and gradual changes in coloration continue for months afterwards. “It seems like there’s a slow, gradual build-up of the dark melanin pigment,” Corl said.

The lizard populations on and off the lava flow both have this plasticity enabling them to change color when moved to a new environment. But the two populations also have heritable differences in pigmentation. Genetic analysis revealed differences between the two populations in two genes involved in the regulation of melanin production.

The researchers cross-bred lizards from the two populations, raised the offspring in a common environment, and measured coloration of the offspring. Those experiments showed that variations in the melanin-related genes correlate with the darkness of the lizards’ skins.

Genetic sampling of side-blotched lizards surrounding the lava flow showed that the gene variants found in the lava population are restricted to that population, suggesting that the variants arose through mutations that occurred in lizards living on the lava and spread within that population. Demographic modeling studies suggested that the new mutations arose thousands of years after the lava flow occurred, about 22,000 years ago.

“We’ve studied side-blotched lizards all over, even at another lava flow, and these genetic variants are only found at Pisgah, so we know that’s where they arose,” Sinervo said. “These are genes that govern coloration by controlling the melanin production pathway, but in a complex way. The Pisgah lizards have the best match to the color of the lava of any population, yet they can still go back to sand and match a completely different background.”

The range of coloration possible for an individual lizard is remarkable. “In some ways, it’s amazing that natural selection still acts in the presence of so much plasticity. All it takes is a bit of a mismatch and that can make the difference between life and death,” Corl said. “There is still variation within the population, so we caught natural selection in the process of acting on these genes. We can now conduct further field and lab studies aimed at better understanding how highly plastic traits are shaped by evolution.”

Author: Tim Stephens | Source: University of California – Santa Cruz [September 06, 2018]



Global warming: Worrying lessons from the past

Fifty-six million years ago, Earth experienced an exceptional episode of global warming. In a very short time on a geological scale, within 10,000 to 20,000 years, the average temperature increased by 5 to 8 degrees, only returning to its original level a few hundred thousand years later. Based on the analysis of sediments from the southern slope of the Pyrenees, researchers from the University of Geneva (UNIGE) measured the impact of this warming on river floods and the surrounding landscapes: the amplitude of floods increased by a factor of eight — and sometimes even by a factor of 14 — and vegetated landscapes may have been replaced by arid pebbly plains. Their disturbing conclusions, to be discovered in Scientific Reports, show that the consequences of such global warming may have been much greater than predicted by current climate models.

Global warming: Worrying lessons from the past
Sebastien Castelltort facing the Eocene Cis conglomerate cliff, near Roda de Isabena, Spain
[Credit: UNIGE]

“The method we relied on to analyse this global warming is directly inspired by cell signaling in systems biology, where researchers analyse the response of cells to external stimuli and the ensuing signal transmission,” explains Sebastien Castelltort, professor in the Department of Earth Sciences at the UNIGE Faculty of Sciences, and leader of the study, in collaboration with researchers from the universities of Lausanne, Utrecht, Western Washington and Austin.

“We are interested in how a system, in this case the hydrologic cycle through the behavior of rivers, reacts to an external signal, here the global warming.” This project focused on an extreme climatic case that was well known to scientists: a warming of 5 to 8 degrees that occurred 56 million years ago, between the Paleocene and the Eocene epochs, also known by the acronym PETM (Palaeocene-Eocene Thermal Maximum). Named Earth Surface Signaling System (ESSS) this project is supported by the Swiss National Science Foundation (SNSF).

Palm trees at polar latitudes

As early as the 1970s, scientists observed a strong anomaly in the ratio between stable carbon isotopes (δ13C), due to the relative increase in the proportion of the light isotope (12C) compared to the heavy isotope (13C), reflecting a disruption of the carbon cycle, both in the oceans and on the continents, associated with a global warming and its spectacular consequences. Palm trees thrived at polar latitudes and some marine plankton, such as dinoflagellate Apectodinium, normally restricted to tropical waters, suddenly spread across the globe.

Geologists use this type of observation as true “paleothermometres,” which in this case show a rise in surface water temperature that has reached almost 36 degrees in places, a lethal temperature for many organisms. Several phenomena are cited as possible causes for this global warming, from the intense volcanic activity in several areas of the globe at this period, to the destabilization of methane hydrates, these methane “ice cubes” that only remain stable under certain pressure and temperature conditions, and which by degassing would have released their greenhouse gas.

But although the event is known and its causes have been extensively explored, what about the consequences? “The question is important because there is an obvious analogy with the current global warming. There are lessons to be learned from this event, even more so as the rise in temperatures we are currently witnessing seems to be much faster,” Sebastien Castelltort emphasizes.

Pebbles that reveal the history of rivers

The Spanish Pyrenees offer sediments that allow us to observe the ancient river channels and to determine their size. As part of Chen Chen’s thesis project, a doctoral student at the Department of Earth Science at the UNIGE Faculty of Sciences, thousands of ancient river pebbles were measured in the field.

Step by step, thanks to the direct relationship between the size of the pebbles and the slope of the rivers, researchers were thus able to calculate their flow velocity and discharge. They have therefore unveiled the whole history of these rivers, and that of the spectacular changes that have affected them.

56 million years ago, the Pyrenees were being formed and their foothills were traversed by small isolated channels in a flood plain where they deposited very fertile alluvium, promoting the development of vegetation whose roots would anchor the soil. Leaving the Pyrenean piedmont, these small rivers then headed west into the Atlantic which was then only about thirty kilometres away.

The landscape changed completely

“With global warming, the landscape changed completely. The channel-forming floods, which occur on average every 2 to 3 years and whose flow we have been able to measure, went up to 14 times greater than before when climate was cooler,” explains Sebastien Castelltort.

During the PETM, rivers constantly changed course, they no longer adapted to increased discharge by incising their bed but instead they widened sometimes dramatically, from 15 to 160 meters wide in the most extreme case. Instead of being trapped in the floodplains, the alluvium was transferred directly towards the ocean, and the vegetation seemed to disappear. The landscape turned into arid extensive gravel plains, crossed by ephemeral and torrential rivers.

Far greater risks than expected

Scientists still do not know how precipitation patterns have changed, but they know that this warming has led to more intense floods and higher seasonality, with significantly warmer summers. Higher evaporation resulted in an unexpected increase in flood magnitude. One degree of temperature rise implies a 7% increase in the atmosphere capacity to retain moisture, and this ratio is generally used to assess the increase in precipitation.

“But our study shows that there are thresholds, non-linear evolutions that go beyond this ratio. With a ratio of 14 for flood magnitude, we face effects that we do not understand, which can perhaps be explained by local factors, but also by global factors that are not yet incorporated into current climate models. Our study proves that the risks associated with global warming may be far greater than we generally think,” concludes Sebastien Castelltort.

Source: Universite de Geneve [September 06, 2018]



Viking ‘Battle of Largs’ Monument, Largs, Scotland, 8.9.18.’The...

Viking ‘Battle of Largs’ Monument, Largs, Scotland, 8.9.18.

‘The Pencil’ monument is to commemorate the Battle of Largs in 1263, considered by many to be the last Norse assertion of rule; the final ‘Battle of Vikings’. The monument evokes the defensive towers found in Ireland during this period. Built in the early twentieth century, it stands approximately where beached Viking vessels landed, although the battle itself took place slightly further up the coastline.

Source link

Neuron and Off Our brains thrive on communication. Connections…

Neuron and Off

Our brains thrive on communication. Connections between neurons fine-tune signals zipping between brain areas, ultimately guiding everything we do. Tree-like Purkinje cells are the master communicators of the cerebellum, where their many connected branches help to coordinate precise body movements. These virtual Purkinjes, from a new computer model, predict how real cells react when nearby brain structures called climbing fibres (not shown here) turn them ‘on’. The model predicts this isn’t a simple on/off switch, though, but a sort of volume dial. Ramping up the electrical input (from left to right here) fires up an increasing number of the Purkinjes branches. These predictions fit with real experiments from all over the world. The idea of controlling brain signals sensitively, rather than just ‘on’ or ‘off’, already has researchers racing to explore the implications for development and disease.

Written by John Ankers

You can also follow BPoD on Instagram, Twitter and Facebook

Archive link

Copan excavations in Honduras reveal royal connections

Scientists from Honduras and China are working together to uncover the history of the ruins in Copan, Honduras to understand a particular Mayan community, El Chorro, and their relationship with the Copan royal court more than 1,400 years ago.

Copan excavations in Honduras reveal royal connections
Copan sculpture [Credit: © Presse750/Dreamstime]

Scientists from the Honduran Institute of Anthropology and History (IHAH) and the Institute of Archaeology of the Academy of Social Sciences of China are investigating what’s called the 8N11 Group section of Honduras’ largest archeological site, to better understand the El Chorro community and its political and economic relationship with Copan Mayan royalty.

The excavations, which began in August 2015 and are expected to run until 2020. “In five years we hope to have investigated the entire complex and completed all restoration,” explained archaeologist Jorge H. Ramos from the INAH, in charge of the excavations.

Ramos says he’s starting to see similarities between the mosaics in El Chorro and those decorating the walls of what were royal buildings.

“It seems that the same school of sculptors who worked for the royal family also worked for the group (in El Chorro), as they are very similar in artistic and architectural style. This is the most advanced group in the Copan Valley,” added the archaeologist.

Copan excavations in Honduras reveal royal connections
Copan ruins [Credit: WikiCommons]

The scientist told local media he thinks that if there were similarities in construction between the two places then there could have been a political connection between the inhabitants of El Chorro and the royal court.

“If there were a direct physical relationship and a political connection between the groups, it is probable that the families who lived in El Chorro were important to the members of the Royal Court,” concludes Ramos.

The finds so far are showing architectural connections between the El Chorro community and Mayan royalty starting with the tenth Copan ruler, Tzi B’alam (Luna Jaguar) who lead starting around 500 A.D., until the 16 ruler, Yax Pac. The height of the similarities occurred, however, during the time of Copans last two rulers.

During the three years of El Chorro, excavations scientist have also found funeral crypts and coffins containing human remains. Along the caskets offerings such as necklaces, vessels, pitchers, and glasses have also been excavated as it was common to find such items to accompany the Mayan who believe in life after death.

Copan excavations in Honduras reveal royal connections
Map Copán centre [Credit: WikiCommons]

The Archaeological Park of Copan was declared a UNESCO World Heritage site in 1982.

“The Copan ruins are the most important archaeological site in Honduras, a center where the investigations are continuous. The Mayan civilization follows us surprising every day,” says Hector Portillo, director IHAH.

“We need Hondurans to know more about their heritage,” the director added.

Source: telesur [September 05, 2018]



Ukrainian archaeologists discover unique Bronze Age burial of Yamna ‘tribal...

A group of Ukrainian archaeologists have discovered a unique Bronze Age burial near the village of Pologi, in the Zaporozhye region, said to date from the third millennium BC.

Ukrainian archaeologists discover unique Bronze Age burial of Yamna 'tribal leader'
Credit: Андрея Тощева/061

The burial, found under a layer of soil just over 10 centimetres deep, belongs to a male estimated to have been between 40-50 years old. The researchers said the man was about 2 metres tall.
Near the skeleton, archaeologists found a bronze knife and staff or sceptre, suggesting that the deceased may have been a tribal leader of the Yamna.

Ukrainian archaeologists discover unique Bronze Age burial of Yamna 'tribal leader'

Ukrainian archaeologists discover unique Bronze Age burial of Yamna 'tribal leader'

Ukrainian archaeologists discover unique Bronze Age burial of Yamna 'tribal leader'

Ukrainian archaeologists discover unique Bronze Age burial of Yamna 'tribal leader'
Credit: Андрея Тощева/061

Archaeologist Gennady Toshchev noted that the burial is a unique find for the steppe zone of the Zaporozhye region.
The Yamna culture, also variously known as the Pit Grave culture or Ochre Grave culture, flourished in the Pontic–Caspian steppes during the late Chalcolithic and Early Bronze Ages, ie. between 3300–2600 BC.

The Yamna culture is identified today with the late Proto-Indo-Europeans.

Source: 061 [September 06, 2018]



What Anglo Saxon teeth can tell us about modern health

Evidence from the teeth of Anglo Saxon children could help identify modern children most at risk from conditions such as obesity, diabetes and heart disease.

What Anglo Saxon teeth can tell us about modern health
CT scan of 5 year old Anglo Saxon jawbone from Raunds Furnells
[Credit: University of Bradford]

Researchers from the University of Bradford found that analysis of milk teeth of children’s skeletons from a 10th Century site in Northamptonshire, England, gave a more reliable indicator of the effects of diet and health than bone.

The study, published in the American Journal of Physical Anthropology, shows that by analysing dentine from the milk teeth of the Anglo Saxon children, a picture emerges of the development of these children from the third trimester of pregnancy onwards, and is a proxy indicator of the health of the mothers. This is the first time that secure in utero data has been measured.

The skeletons analysed at the University of Bradford come from a settlement at Raunds Furnells and are from a group known to have been under nourished. The effect of this under nourishment, or stress, is to limit the growth of bones. This can limit the evidence available from analysis of bones alone, such as age.

Researchers were also able to look at children of different ages to see whether those who survived the first 1,000 days from conception, during which factors such as height are set, had different biomarkers for stress than those who died during this high-risk period.

Teeth, unlike bone, continue to grow under such stress and, unlike bone, record high nitrogen values. This evidence gives a clearer picture of what is happening to the child from before birth. The teeth are, in effect, acting as an archive of diet and health of both the child and mother.

Dr Julia Beaumont, of the University of Bradford’s School of Archaeological and Forensic Sciences, said: “This is the first time that we have been able to measure with confidence the in utero nitrogen values of dentine. We find that when bone and teeth form at the same time, bone doesn’t record high nitrogen values that occur during stress. Our hypothesis is that bone isn’t growing but teeth are. So archaeology can’t rely on the evidence from bones alone because bone is not forming and recording during high stress and we can’t be sure, for example, of the age of a skeleton. Teeth are more reliable as they continue to grow even when a child is starving.”

As well as the archaeological significance of this method of analysis, Dr Beaumont believes it has a direct application to modern medicine.

She said: “There is a growing consensus that factors such as low birthweight have a significant impact on our likelihood of developing conditions such as heart disease, diabetes and obesity and that the first 1,000 days from conception onwards set our ‘template’. By analysing the milk teeth of modern children in the same way as the Anglo Saxon skeletons, we can measure the same values and see the risk factors they are likely to face in later life, enabling measures to be taken to mitigate such risks.”

Source: University of Bradford [September 06, 2018]



Ancient farmers spared us from glaciers but profoundly changed Earth’s climate

Millennia ago, ancient farmers cleared land to plant wheat and maize, potatoes and squash. They flooded fields to grow rice. They began to raise livestock. And unknowingly, they may have been fundamentally altering the climate of Earth.

Ancient farmers spared us from glaciers but profoundly changed Earth's climate
Life in a wet rice farming village in Japan c.300 BC [Credit: Heritage of Japan]

A study published in the journal Scientific Reports provides new evidence that ancient farming practices led to a rise in the atmospheric emission of the heat-trapping gases carbon dioxide and methane — a rise that has continued since, unlike the trend at any other time in Earth’s geologic history.

It also shows that without this human influence, by the start of the Industrial Revolution, the planet would have likely been headed for another ice age.

“Had it not been for early agriculture, Earth’s climate would be significantly cooler today,” says lead author, Stephen Vavrus, a senior scientist in the University of Wisconsin-Madison Center for Climatic Research in the Nelson Institute for Environmental Studies. “The ancient roots of farming produced enough carbon dioxide and methane to influence the environment.”

The findings are based on a sophisticated climate model that compared our current geologic time period, called the Holocene, to a similar period 800,000 years ago. They show the earlier period, called MIS19, was already 2.3 degrees Fahrenheit (1.3 C) cooler globally than the equivalent time in the Holocene, around the year 1850. This effect would have been more pronounced in the Arctic, where the model shows temperatures were 9-to-11 degrees Fahrenheit colder.

Using climate reconstructions based on ice core data, the model also showed that while MIS19 and the Holocene began with similar carbon dioxide and methane concentrations, MIS19 saw an overall steady drop in both greenhouse gases while the Holocene reversed direction 5,000 years ago, hitting peak concentrations of both gases by 1850. The researchers deliberately cut the model off at the start of the Industrial Revolution, when sources of greenhouse gas emissions became much more numerous.

For most of Earth’s 4.5-billion-year history, its climate has largely been determined by a natural phenomenon known as Milankovitch cycles, periodic changes in the shape of Earth’s orbit around the sun — which fluctuates from more circular to more elliptical — and the way Earth wobbles and tilts on its axis.

Astronomers can calculate these cycles with precision and they can also be observed in the geological and paleoecological records. The cycles influence where sunlight is distributed on the planet, leading to cold glacial periods or ice ages as well as warmer interglacial periods. The last glacial period ended roughly 12,000 years ago and Earth has since been in the Holocene, an interglacial period. The Holocene and MIS19 share similar Milankovitch cycle characteristics.

All other interglacial periods scientists have studied, including MIS19, begin with higher levels of carbon dioxide and methane, which gradually decline over thousands of years, leading to cooler conditions on Earth. Ultimately, conditions cool to a point where glaciation begins.

Fifteen years ago, study co-author William Ruddiman, emeritus paleoclimatologist at the University of Virginia, was studying methane and carbon dioxide trapped in Antarctic ice going back tens of thousands of years when he observed something unusual.

“I noticed that methane concentrations started decreasing about 10,000 years ago and then reversed direction 5,000 years ago and I also noted that carbon dioxide also started decreasing around 10,000 years ago and then reversed direction about 7,000 years ago,” says Ruddiman. “It alerted me that there was something strange about this interglaciation … the only explanation I could come up with is early agriculture, which put greenhouse gases into the atmosphere and that was the start of it all.”

Ruddiman named this the Early Anthropogenic Hypothesis and a number of studies have recently emerged suggesting its plausibility. They document widespread deforestation in Europe beginning around 6,000 years ago, the emergence of large farming settlements in China 7,000 years ago, plus the spread of rice paddies — robust sources of methane — throughout northeast Asia by 5,000 years ago.

Ruddiman and others have also been working to test the hypothesis. He has collaborated with Vavrus, an expert in climate modeling, for many years and their newest study used the Community Climate System Model 4 to simulate what would have happened in the Holocene if not for human agriculture. It offers higher resolution than climate models the team has used previously and provides new insights into the physical processes underlying glaciation.

For instance, in a simulation of MIS19, glaciation began with strong cooling in the Arctic and subsequent expansion of sea ice and year-round snow cover. The model showed this beginning in an area known as the Canadian archipelago, which includes Baffin Island, where summer temperatures dropped by more than 5 degrees Fahrenheit.

“This is consistent with geologic evidence,” says Vavrus.

Today, the Arctic is warming. But before we laud ancient farmers for staving off a global chill, Vavrus and Ruddiman caution that this fundamental alteration to our global climate cycle is uncharted territory.

“People say (our work) sends the wrong message, but science takes you where it takes you,” says Vavrus. “Things are so far out of whack now, the last 2,000 years have been so outside the natural bounds, we are so far beyond what is natural.”

The reality is, we don’t know what happens next. And glaciers have long served as Earth’s predominant source of freshwater.

“There is pretty good agreement in the community of climate scientists that we have stopped the next glaciation for the long, foreseeable future, because even if we stopped putting carbon dioxide into the atmosphere, what we have now would linger,” says Ruddiman. “The phenomenal fact is, we have maybe stopped the major cycle of Earth’s climate and we are stuck in a warmer and warmer and warmer interglacial.”

Author: Kelly April Tyrrell | Source: University of Wisconsin-Madison [September 06, 2018]



Cemetery from prehistoric and historical times excavated in Aliveri, Greece

A cemetery was excavated this summer by the Ephorate of Antiquities of Euboea at the site Makria Rachi of Karavos in Aliveri. This proved to be a real palimpsest in terms of the region’s archaeological data, since during a rescue survey carried out on a private plot of land, it was found that the cemetery had been in continuous use for over 2,500 years.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Finds from the Mycenaean chamber tomb [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

Specifically, the following were located in chronological order:

1. An unplundered shaft grave of monumental construction belonging to the Early Helladic IIB era (Lefkandi I phase–Kastri 2400-2300 BC). The floor was strewn with river sand and its interior, during its second phase, had been divided by a transverse wall into two sections.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Proto-Helladic grave [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

A secondary burial was located in the east section, containing grave goods of a pair of gold earrings, one silver and two bronze ornamental pins. Αn in situ burial in the foetal/contracted position was discovered in the west section, with grave goods of a bronze dagger, an arrow head and a polished spherical prochous with a beaked spout. The head of a marble Cycladic figurine of the Louros type (3200-2800 BC) was discovered a short distance from the grave.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Bronze dagger from the tomb of the Early Helladic era [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

2. An unplundered chamber tomb of the Late Helladic IIIB-C era (1300-1100 BC) with a chamber diameter of 2.40m and a corridor length of 7.50m. It contained 11 retrieval burials and one in situ. Inside it were discovered 6 intact and at least 7 more fragmented vases, mainly stirrup jars, alabastra, prochoi and cups, a bronze ornamental pin, 53 loom weights of steatite, stone beads, elaborate ivory buttons and three seals of great artistic value.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
The interior of the Mycenaean chamber tomb [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

On the first seal a wild goat is depicted being attacked by two wolves, on the second a deer is depicted in a twisted position.Τhe third seal, however, which is made of carnelian is particularly interesting as it depicts an upright daemonic figure, a Minoan Genius, which is carrying a dead deer on its shoulders. An identical theme is encountered on a seal from Crete and an ivory tile from Thebes.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Quartz seal from the Mycenaean chamber tomb [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

In Roman times, part of the tomb’s roof collapsed and was used as a depositor without the lower burial layers being disturbed. Many animal bones came from the upper layers as well as pieces of vases from the Roman period (1st-3rd century AD).

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Carnelian seal from the Mycenaean chamber tomb [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

3. In all, 24 more graves were investigated on the same plot of land, consisting of one jar burial and a cremation of the Late Classical (end of 4th c. BC), Hellenistic (3rd-1st c. B.C.) and Roman times (1st-3rd c. A.D.), in clusters of 2 to 4 graves. Seven of the graves belong to the tiled roof hut type, 16 to the simple pit grave covered by rough slabs and one is a built shaft grave of the Roman era. The following artefacts have been unearthed from them: a gold earring, an ornamental bone pin, bronze coins, black glazed miniature vases of the 4th century BC, such as lekythia, a pyxis, a clay statuette of a pig, an unpainted trefoil oinochoe and a prochous of the Roman era.

Cemetery from prehistoric and historical times excavated in Aliveri, Greece
Finds from tombs of the Classical era (4th c. BC) [Credit: Ministry of Culture and Sports/
Ephorate of Antiquities of Euboea]

4. Lastly, an underground rock hewn and partially built water conduit of the Roman era was located, that runs across the cemetery in a NE to SW direction for a length of almost 25 m and very probably supplied water to the adjacent bath house of the early Christian era.

This year’s excavation provides valuable information about the inhabitants of the settlement that was excavated while the new factory of the Public Power Company of Greece was being built in the same region between 2007 and 2014. The grave goods that were studied from inside the tombs show that the inhabitants of the coastal settlement of Karavos, Aliveri, by making good use of their natural harbour had developed significant trading relations with the mainland and the islands. In the Mycenaean era, these relations reached as far as Crete.

The excavation, which continues, is reaching its end. It is headed by archaeologist Konstantinos Boukaras of the Ephorate of Antiquities of Euboea, while the conservation of the findings is being conducted by Fotini Popoli and Georgia Kageli, conservators of antiquities.

Source: Greek Ministry of Culture and Sports via Archaeology and Arts [September 06, 2018]




https://t.co/hvL60wwELQ — XissUFOtoday Space (@xufospace) August 3, 2021 Жаждущий ежик наслаждается пресной водой после нескольких дней в о...