Geologists reveal ancient connection between England and France

The British mainland was formed from the collision of not two, but three ancient continental land masses, according to new research.

Scientists have for centuries believed that England, Wales and Scotland were created by the merger of Avalonia and Laurentia more than 400 million years ago. However, geologists based at the University of Plymouth now believe that a third land mass — Armorica — was also involved in the process.

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England, Scotland and Wales. Credit: University of Plymouth

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England, Scotland and Wales.
Credit: University of Plymouth

The findings are published in Nature Communications and follow an extensive study of mineral properties at exposed rock features across Devon and Cornwall. They reveal a clear boundary running across the two counties, with areas north of it sharing their geological roots with the rest of England and Wales but everything south being geologically linked to France and mainland Europe. Among other things, scientists believe the research explains the abundance of tin and tungsten in the far South West of England — metals also found in Brittany and other areas of mainland Europe, but not so evident in the rest of the UK.

The research’s lead author, Lecturer in Igneous Petrology Dr Arjan Dijkstra, said: “This is a completely new way of thinking about how Britain was formed. It has always been presumed that the border of Avalonia and Armorica was beneath what would seem to be the natural boundary of the English Channel. But our findings suggest that although there is no physical line on the surface, there is a clear geological boundary which separates Cornwall and south Devon from the rest of the UK.” For the research, Dr Dijkstra and Masters student Callum Hatch (now working at the Natural History Museum) visited 22 sites in Devon and Cornwall that were left exposed following geological events, such as underground volcanic eruptions. These took place around 300 million years ago and brought magma from depths of 100 km to the Earth’s surface. They took rock samples from each site, subjecting them to detailed chemical analysis in the lab using X-ray fluorescence (XRF) spectrometry.
The samples were also then dissolved in acid in order to conduct a more intensive isotopic analysis, with scientists examining the levels of two elements — strontium and neodymium — to understand the full history of the rocks. These findings were then compared with previous studies elsewhere in the UK and mainland Europe, with the results showing the clear boundary running from the Exe estuary in the East to Camelford in the west. “We always knew that around 10,000 years ago you would have been able to walk from England to France,” Dr Dijkstra added. “But our findings show that millions of years before that, the bonds between the two countries would have been even stronger. It explains the immense mineral wealth of South West England, which had previously been something of a mystery, and provides a fascinating new insight into the geological history of the UK.”
Citation:University of Plymouth. “Geologists reveal ancient connection between England and France.” ScienceDaily. ScienceDaily, 14 September 2018. <www.sciencedaily.com/releases/2018/09/180914084835.htm>.

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.

Sébastien Castelltort facing the Eocene Cis conglomerate cliff, near Roda de Isabena, Spain. Credit: UNIGE

Sébastien 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 Sébastien 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,” Sébastien 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 Sébastien 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 Sébastien Castelltort.

Citation: Université de Genève. “Global warming: Worrying lessons from the past.” ScienceDaily. ScienceDaily, 6 September 2018. <www.sciencedaily.com/releases/2018/09/180906082126.htm>.

Ancient farmers 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.

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.”

Citation:University of Wisconsin-Madison. “Ancient farmers spared us from glaciers but profoundly changed Earth’s climate.” ScienceDaily. ScienceDaily, 6 September 2018. <www.sciencedaily.com/releases/2018/09/180906141507.htm>.

Mammal forerunner that reproduced like a reptile sheds light on brain evolution

Compared with the rest of the animal kingdom, mammals have the biggest brains and produce some of the smallest litters of offspring. A newly described fossil of an extinct mammal relative — and her 38 babies — is among the best evidence that a key development in the evolution of mammals was trading brood power for brain power.

The find is among the rarest of the rare because it contains the only known fossils of babies from any mammal precursor, said researchers from The University of Texas at Austin who discovered and studied the fossilized family. But the presence of so many babies — more than twice the average litter size of any living mammal — revealed that it reproduced in a manner akin to reptiles. Researchers think the babies were probably developing inside eggs or had just recently hatched when they died.

Researchers from The University of Texas at Austin found a fossil of an extinct mammal relative with a clutch of 38 babies that were near miniatures of their mother. Credit: Eva Hoffman / The University of Texas at Austin

Researchers from The University of Texas at Austin found a fossil of an extinct mammal relative with a clutch of 38 babies that were near miniatures of their mother.
Credit: Eva Hoffman / The University of Texas at Austin

The study, published in the journal Nature on Aug. 29, describes specimens that researchers say may help reveal how mammals evolved a different approach to reproduction than their ancestors, which produced large numbers of offspring.

“These babies are from a really important point in the evolutionary tree,” said Eva Hoffman, who led research on the fossil as a graduate student at the UT Jackson School of Geosciences. “They had a lot of features similar to modern mammals, features that are relevant in understanding mammalian evolution.”

Hoffman co-authored the study with her graduate adviser, Jackson School Professor Timothy Rowe.

The mammal relative belonged to an extinct species of beagle-size plant-eaters called Kayentatherium wellesi that lived alongside dinosaurs about 185 million years ago. Like mammals, Kayentatherium probably had hair.

When Rowe collected the fossil more than 18 years ago from a rock formation in Arizona, he thought that he was bringing a single specimen back with him. He had no idea about the dozens of babies it contained.

Sebastian Egberts, a former graduate student and fossil preparator at the Jackson School, spotted the first sign of the babies years later when a grain-sized speck of tooth enamel caught his eye in 2009 as he was unpacking the fossil.

“It didn’t look like a pointy fish tooth or a small tooth from a primitive reptile,” said Egberts, who is now an instructor of anatomy at the Philadelphia College of Osteopathic Medicine. “It looked more like a molariform tooth (molar-like tooth) — and that got me very excited.”

A CT scan of the fossil revealed a handful of bones inside the rock. However, it took advances in CT-imaging technology during the next 18 years, the expertise of technicians at UT Austin’s High-Resolution X-ray Computed Tomography Facility, and extensive digital processing by Hoffman to reveal the rest of the babies — not only jaws and teeth, but complete skulls and partial skeletons.

The 3D visualizations Hoffman produced allowed her to conduct an in-depth analysis of the fossil that verified that the tiny bones belonged to babies and were the same species as the adult. Her analysis also revealed that the skulls of the babies were like scaled-down replicas of the adult, with skulls a tenth the size but otherwise proportional. This finding is in contrast to mammals, which have babies that are born with shortened faces and bulbous heads to account for big brains.

The brain is an energy-intensive organ, and pregnancy — not to mention childrearing — is an energy-intensive process. The discovery that Kayentatherium had a tiny brain and many babies, despite otherwise having much in common with mammals, suggests that a critical step in the evolution of mammals was trading big litters for big brains, and that this step happened later in mammalian evolution.

“Just a few million years later, in mammals, they unquestionably had big brains, and they unquestionably had a small litter size,” Rowe said.

The mammalian approach to reproduction directly relates to human development — including the development of our own brains. By looking back at our early mammalian ancestors, humans can learn more about the evolutionary process that helped shape who we are as a species, Rowe said.

“There are additional deep stories on the evolution of development, and the evolution of mammalian intelligence and behavior and physiology that can be squeezed out of a remarkable fossil like this now that we have the technology to study it,” he said.

Funding for the research was provided by the National Science Foundation, The University of Texas Geology Foundation and the Jackson School of Geosciences.

Citation: University of Texas at Austin. “Mammal forerunner that reproduced like a reptile sheds light on brain evolution.” ScienceDaily. ScienceDaily, 29 August 2018. <www.sciencedaily.com/releases/2018/08/180829133422.htm>.

Rare fossils give researchers insight into evolution of bird-like dinosaur

An international team of researchers discovered a new species of dinosaur, Xiyunykus pengi, during an expedition to Xinjiang, China. The discovery is the latest stemming from a partnership between the George Washington University and the Chinese Academy of Sciences. The findings were published today in Current Biology along with the description of a second new intermediate species, Bannykus wulatensis.

 Xiyunykus bones in the lab before their removal from the rock. Credit: James Clark

Xiyunykus bones in the lab before their removal from the rock.
Credit: James Clark

Xiyunykus and Bannykus are both alvarezsaurs, an enigmatic group of dinosaurs that share many characteristics with birds. Their bodies are slender, with a bird-like skull and many small teeth instead of the usual large, sharp cutting teeth of their meat-eating relatives.

“When we described the first well-known alvarezsaur, Mononykus, in 1993, we were amazed at the contrast between its mole-like arms and its roadrunner-like body, but there were few fossils connecting it back to other theropod groups,” James Clark, the Ronald Weintraub Professor of Biology at the GW Columbian College of Arts and Sciences, said.

However, alvarezsaurs did not always look this way. Early members of the group had relatively long arms with strong-clawed hands and typical meat-eating teeth. Over time, the alvarezsaurs evolved into dinosaurs with mole-like arms and a single claw. The discovery of the new specimens allowed the researchers to uncover an important shift in how the specialized features of the alvarezsaurs evolved.

“It can be hard to pin down the relationships of highly specialized animals. But fossil species with transitional features, like Xiyunykus and Bannykus, are tremendously helpful because they link bizarre anatomical features to more typical ones,” Jonah Choiniere, an associate professor at Wits University and member of the research team, said.

The fossils were discovered during an expedition co-led by Dr. Clark and Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences. Xiyunykus pengi is the ninth species of dinosaur identified by the partnership between GW and the academy.

“Our international field teams have been tremendously productive over the years,” Dr. Xu said. “This research showcases just some of our incredible discoveries.”

The fieldwork and research were supported by U.S. National Science Foundation grant EAR 0922187.

Citation: George Washington University. “Rare intermediate fossils give researchers insight into evolution of bird-like dinosaur: Discovery fills in missing link in evolutionary transition of the alvarezsaurs.” ScienceDaily. ScienceDaily, 23 August 2018. <www.sciencedaily.com/releases/2018/08/180823140932.htm>.

Research into deadly 2016 Italian earthquakes could improve future seismic forecasts

The timing and size of three deadly earthquakes that struck Italy in 2016 may have been pre-determined, according to new research that could improve future earthquake forecasts.

A joint British-Italian team of geologists and seismologists have shown that the clustering of the three quakes might have been caused by the arrangement of a cross-cutting network of underground faults.

The findings show that although all three earthquakes occurred on the same major fault, several smaller faults prevented a single massive earthquake from occurring instead and also acted as pathways for naturally occurring fluids that triggered later earthquakes.

The cluster of three earthquakes, termed a “seismic sequence” by seismologists, each had magnitudes greater than six and killed more than 300 people in Italy’s Apennine mountains between 24 August and 30 October 2016.

Location of survey site at rupture across a road near Castelluccio, Italy. The rupture occurred during the third earthquake in the seismic sequence and gives researchers a record of the deformation. Credit: Laura Gregory, University of Leeds

Location of survey site at rupture across a road near Castelluccio, Italy. The rupture occurred during the third earthquake in the seismic sequence and gives researchers a record of the deformation.
Credit: Laura Gregory, University of Leeds

The research, led by Durham University, UK, comes ahead of the second anniversary of the start of the earthquake sequence.

The study is published in the journal Earth and Planetary Science Letters.

The researchers say the findings could have wider implications for the study of seismic hazards, enabling scientists to better understand potential earthquake sequences following a quake.

Dr Richard Walters, Assistant Professor in the Department of Earth Sciences, Durham University, said: “These results address a long-standing mystery in earthquake science — why a major fault system sometimes fails in a single large earthquake that ruptures its entire length, versus failing in multiple smaller earthquakes drawn-out over months or years.

“Our results imply that even though we couldn’t have predicted when the earthquake sequence would start, once it got going, both the size and timing of the major earthquakes may have been pre-determined by the arrangement of faults at depth.

“This is all information we could hypothetically know before the event, and therefore, this could be a hugely important avenue for improving future earthquake forecasts.”

Dr Walters and the team used satellite data to estimate which part of the fault failed in each earthquake, and compared this pattern with the location and timing of thousands of tiny aftershocks throughout the seismic sequence.

They found that intersections of small faults with the main fault system separated each of the three largest earthquakes, strongly suggesting these intersections stop the growth of each earthquake and prevent the faults failing in a single large event.

But in addition, the scientists also found that after the first earthquake, thousands of aftershocks crept northwards along these same fault intersections at a rate of around 100 metres per day, in a manner consistent with naturally occurring water and gas being pumped along the faults by the first earthquake on 24 August, 2016.

The second earthquake, on the 26 October, occurred exactly when these fluids reached its location, therefore controlling the relative timing of failure.

Dr Walters added: “It was a big surprise that these relatively small faults were having such a huge influence over the whole sequence.

“They stop the first earthquake in its tracks, and then they channel the fluids that start the sequence up again months later. No-one’s ever seen this before.”

Co-author Dr Laura Gregory, in the School of Earth and Environment, at the University of Leeds, UK, said it was important to understand whether or not a fault fails in a seismic sequence, and that the team’s results were only made possible by combining a varied array of different datasets.

Dr Gregory said: “A seismic sequence has vastly different implications for seismic hazard compared to a single large earthquake. If the faults in Italy in 2016 had failed together in one big event, the impact on the local population would have been much worse.

“This is the first time we’ve ever had this quality of modern data over one of these earthquake sequences, and bringing together a range of specialists was key for unpicking how the earthquakes related to one another.

“I was scrambling over the mountainside immediately after each earthquake with British and Italian colleagues, measuring the metre-high cliffs that had suddenly formed. Meanwhile, other members of our team were analysing data from seismometers stationed around the world, or were mapping the tiny bending of the ground around the faults using satellites orbiting the planet at 500 miles altitude.”

The research was partly supported by the UK’s Natural Environment Research Council, via an Urgency Grant, and through the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET).

Study of material surrounding distant stars shows that Earth’s ingredients are pretty normal

The Earth’s building blocks seem to be built from ‘pretty normal’ ingredients, according to researchers working with the world’s most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth.

This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere.

“Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth,” said researcher Dr Siyi Xu of the Gemini Observatory in Hawaii, who was presenting the work at the Goldschmidt conference in Boston.

The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system.

“It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves” said Siyi Xu. “So we needed to look at other methods.”

Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense — it is anticipated that our Sun will become a white dwarf in around 5 billion years.

Dr Xu continued, “White dwarfs’ atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn. As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star’s spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected.”

The team took measurements using spectrographs on the Keck telescope in Hawaii, the world’s largest optical and infrared telescope, and on the Hubble Space Telescope.

Siyi Xu continued, “In this study, we have focused on the sample of white dwarfs with dust disks. We have been able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. We may also have found water in one of the systems, but we have not yet quantified it: it’s likely that there will be a lot of water in some of these worlds. For example, we’ve previously identified one star system, 170 light years away in the constellation Boötes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley’s Comet. In general though, their composition looks very similar to bulk Earth.

This would mean that the chemical elements, the building blocks of earth are common in other planetary systems. From what we can see, in terms of the presence and proportion of these elements, we’re normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy.”

Dr Xu continued “This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. We hope to determine the chemical compositions of extrasolar planetary material to a much higher precision”

Professor Sara Seager, Professor of Planetary Science at Massachusetts Institute of Technology, is also the deputy science director of the recently-launched TESS (Transiting Exoplanet Survey Satellite) mission, which will search for exoplanets. She said:

“It’s astonishing to me that the best way to study exoplanet interiors is by planets ripped apart and absorbed by their white dwarf host star. It is great to see progress in this research area and to have solid evidence that planets with Earth-like compositions are common — fueling our confidence that an Earth-like planet around a very nearby normal star is out there waiting to be found.”

Citation: Goldschmidt Conference. “Study of material surrounding distant stars shows Earth’s ingredients ‘pretty normal’.” ScienceDaily. ScienceDaily, 15 August 2018. <www.sciencedaily.com/releases/2018/08/180815190530.htm>.

New Antarctic rift data has implications for volcanic evolution

New data revealing two tectonic plates fused to form a single Antarctic Plate 15 million years later than originally predicted and this extra motion has major implications for understanding of the tectono-volcanic activity surrounding the Pacific Ocean, from the Alpine mountains in New Zealand to the California geological setting, according to research from Ben-Gurion University of the Negev (BGU).

In a study published in Nature Communications, Dr. Roi Granot of BGU’s Department of Geological and Environmental Sciences, and Dr. Jérôme Dyment from the Institut de Physique du Globe de Paris, France, present marine magnetic data collected near the northern edge of the West Antarctic rift system that shows motion between East and West Antarctica, which was assumed to have ended abruptly 26 million years ago, actually continued for another 15 million years.

“Since Antarctica tectonically connects the Pacific Plate to the rest of the world, these results have important ramifications for understanding the tectonic evolution around the Pacific Ocean — the rise of New Zealand’s Alpine Mountains, motions along the San Andreas Fault in California, and more,” says Dr. Granot.

Over 200 million years ago, a rift bisected Antarctica. The motion between East Antarctic and West Antarctic Plates accommodated along the length of this rift created one of the longest mountain ranges in the world (the Transantarctic Mountains). It also caused the eruption of hundreds of volcanoes, mostly under the ice sheets, and shaped the sub-ice topography. These motions dictated, and still dictate, the heat flow rate that the crust releases under the ice and is one of the factors controlling the rate by which the glaciers are advancing toward the surrounding southern ocean.

GPS data and a lack of seismic activity suggest that the rift in Antarctica is no longer tectonically active. According to the researchers, one of the key unanswered question was: How did the plates drift relative to each other over the last 26 million years and when did the rift stop being active?

New marine geophysical data recorded during two excursions on a French icebreaker enabled Drs. Roi Granot and Jérôme Dyment to date the ocean floor and calculate the relative motion between the Antarctic Plates and the Australian Plate.

“Antarctica forms an important link in the global plate tectonic circuits which enable to calculate the motion along different plate boundaries. Understanding past plate motions between East and West Antarctica therefore affects our ability to accurately predict the kinematic evolutions of other plate boundaries,” says Dr. Granot.

Citation: American Associates, Ben-Gurion University of the Negev. “New Antarctic rift data has implications for volcanic evolution.” ScienceDaily. ScienceDaily, 21 August 2018. <www.sciencedaily.com/releases/2018/08/180821094150.htm>.

Meteorite bombardment likely to have created the Earth’s oldest rocks

Scientists have found that 4.02-billion-year-old silica-rich felsic rocks from the Acasta River, Canada — the oldest rock formation known on Earth — probably formed at high temperatures and at a surprisingly shallow depth of the planet’s nascent crust. The high temperatures needed to melt the shallow crust were likely caused by a meteorite bombardment around half a billion years after the planet formed. This melted the iron-rich crust and formed the granites we see today. These results are presented for the first time at the Goldschmidt conference in Boston (14 August), following publication in the peer-reviewed journal Nature Geoscience.

Oldest rock on Earth: Acasta River gneiss (stock image). Credit: © Xenomanes / Fotolia

Oldest rock on Earth: Acasta River gneiss (stock image).
Credit: © Xenomanes / Fotolia

The felsic rocks (rocks rich in silica/quartz) found at the Acasta River in Canada, are the Earth’s oldest rocks, although there are older mineral crystals*. Scientists have long known that the Acasta rocks are different to the majority of felsic rocks we see today, such as the granites widely used as a building or decorative material. Now a group of scientists from Australia and China have modelled the formation of the oldest Acasta felsic rocks and found that they could only have been formed at low pressures and very high temperatures.

Scientists believe that the primitive crust largely comprised dark, silica-poor mafic rocks, so there has been a question over how the Acasta River felsic rocks could have formed.

“Our modelling shows that the Acasta River rocks derived from the melting of pre-existing iron-rich basaltic rock, which formed the uppermost layers of crust on the primitive Earth,” said team leader Tim Johnson, from Curtin University, Perth.

“We used phase equilibria and trace element modelling to show that the Acasta River rocks were produced by partial melting of the original mafic rocks at very low pressures. It would have needed something special to produce the 900°C temperatures needed to generate these early felsic rocks at such low pressures, and that probably means a drastic event, most likely the intense heating caused by meteorite bombardment.

We estimate that rocks within the uppermost 3km of mafic crust would have been melted in producing the rocks we see today. We think that these ancient felsic rocks would have been very common, but the passage of 4 billion years, and the development of plate tectonics, means that almost nothing remains.

We believe that these rocks may be the only surviving remnants of a barrage of extraterrestial impacts which characterized the first 600 million years of Earth History.”

The Acasta River is part of the Slave Craton formation in Northern Canada, north of Yellowknife and the Great Slave Lake. The area is the homeland of the Tlicho people, which led to the geologists who discovered the rocks giving them the name “Idiwhaa,” derived from the Tlicho word for ancient.

Commenting, Dr Balz Kamber (Trinity College Dublin) said: “The idea of making felsic melts by large or giant impacts seems plausible considering the high-energy nature of these events and the pockmarked ancient surfaces of other inner Solar System planets and moons. However, the implied pressure-temperature regime might also permit melting of shallow crust below a super-heated impact melt sea. In other words, an indirect consequence of the impact itself.”

* Rocks from Jack Hills in Australia contain zircon crystals from up to 4.4 billion years ago, embedded in younger rocks.

Source: www.sciencedaily.com

Citation: Goldschmidt Conference. “Meteorite bombardment likely to have created the Earth’s oldest rocks.” ScienceDaily. ScienceDaily, 14 August 2018. <www.sciencedaily.com/releases/2018/08/180813113334.htm>.

99-million-year-old beetle trapped in amber served as pollinator to evergreen cycads

Flowering plants are well known for their special relationship to the insects and other animals that serve as their pollinators. But, before the rise of angiosperms, another group of unusual evergreen gymnosperms, known as cycads, may have been the first insect-pollinated plants. Now, researchers reporting in the journal Current Biology on August 16 have uncovered the earliest definitive fossil evidence of that intimate relationship between cycads and insects.

This image shows a dorsal view of the mid-Cretaceous beetle Cretoparacucujus cycadophilus, including the mandibular cavities it likely used for pollination. Credit: Chenyang Cai

This image shows a dorsal view of the mid-Cretaceous beetle Cretoparacucujus cycadophilus, including the mandibular cavities it likely used for pollination.
Credit: Chenyang Cai

The discovery came in the form of an ancient boganiid beetle preserved in Burmese amber for an estimated 99 million years along with grains of cycad pollen. The beetle also shows special adaptations, including mandibular patches, for the transport of cycad pollen.

“Boganiid beetles have been ancient pollinators for cycads since the Age of Cycads and Dinosaurs,” says Chenyang Cai, now a research fellow at the University of Bristol. “Our find indicates a probable ancient origin of beetle pollination of cycads at least in the Early Jurassic, long before angiosperm dominance and the radiation of flowering-plant pollinators, such as bees, later in the Cretaceous.”

When Cai’s supervisor Diying Huang at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, first showed him the beetle trapped in amber, he was immediately intrigued. He recognized that its large mandibles with bristly cavities might suggest the beetle was a pollinator of cycads.

After cutting, trimming, and polishing the specimen to get a better look under a microscope, Cai’s excitement only grew. The beetle carried several clumps of tiny pollen grains. Cai consulted Liqin Li, an expert in ancient pollen at the Chinese Academy of Sciences, who confirmed that the pollen grains belonged to a cycad.

The researchers also conducted an extensive phylogenetic analysis to explore the beetle’s family tree. Their analysis indicates the fossilized beetle belonged to a sister group to the extant Australian Paracucujus, which pollinate the relic cycad Macrozamia riedlei. The finding, along with the current disjunct distribution of related beetle-herbivore and cycad-host pairs in South Africa and Australia, support an ancient origin of beetle pollination of cycads, the researchers say.

Cai notes that the findings together with the distribution of modern boganiid beetles lead him to suspect that similar beetle pollinators of cycads are yet to be found. He’s been looking for them for the last five years. The challenge, he says, is that older Jurassic beetles are generally found as compression fossils not trapped in amber.

Source: www.sciendaily.com

Citation: Cell Press. “99-million-year-old beetle trapped in amber served as pollinator to evergreen cycads.” ScienceDaily. ScienceDaily, 16 August 2018. <www.sciencedaily.com/releases/2018/08/180816143240.htm>.