The Great London [Search results for Ancient Environment] 

Extensive systems of fossilised riverbeds have been discovered on an ancient region of the Martian surface, supporting the idea that the now cold and dry Red Planet had a warm and wet climate about 4 billion years ago, according to UCL-led research>.

The study, >published in Geology and funded by the Science & Technology Facilities Council and the UK Space Agency, identified over 17,000km of former river channels on a northern plain called Arabia Terra, providing further evidence of water once flowing on Mars.

"Climate models of early Mars predict rain in Arabia Terra and until now there was little geological evidence on the surface to support this theory. This led some to believe that Mars was never warm and wet but was a largely frozen planet, covered in ice-sheets and glaciers. We've now found evidence of extensive river systems in the area which supports the idea that Mars was warm and wet, providing a more favourable environment for life than a cold, dry planet," explained lead author, Joel Davis (UCL Earth Sciences).

Since the 1970s, scientists have identified valleys and channels on Mars which they think were carved out and eroded by rain and surface runoff, just like on Earth. Similar structures had not been seen on Arabia Terra until the team analysed high resolution imagery from NASA's Mars Reconnaissance Orbiter (MRO) spacecraft.

The new study examined images covering an area roughly the size of Brazil at a much higher resolution than was previously possible -- 6 metres per pixel compared to 100 metres per pixel. While a few valleys were identified, the team revealed the existence of many systems of fossilised riverbeds which are visible as inverted channels spread across the Arabia Terra plain.

The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low -- in most other environments, the channels are worn away before they can become inverted.

"The networks of inverted channels in Arabia Terra are about 30m high and up to 1-2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9-3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present," added Joel Davis.

"These ancient Martian flood plains would be great places to explore to search for evidence of past life. In fact, one of these inverted channels called Aram Dorsum is a candidate landing site for the European Space Agency's ExoMars Rover mission, which will launch in 2020," said Dr Matthew Balme, Senior Lecturer at The Open University and co-author of the study.

The researchers now plan on studying the inverted channels in greater detail, using higher-resolution data from MRO's HiRISE camera.

Source: University College London [August 23, 2016]

Using the oldest fossil micrometeorites -- space dust -- ever found, Monash University-led research has made a surprising discovery about the chemistry of Earth's atmosphere 2.7 billion years ago.

The findings of a new study >published in the journal Nature -- led by Dr Andrew Tomkins and a team from the School of Earth, Atmosphere and Environment at Monash, along with scientists from the Australian Synchrotron and Imperial College, London -- challenge the accepted view that Earth's ancient atmosphere was oxygen-poor. The findings indicate instead that the ancient Earth's upper atmosphere contained about the same amount of oxygen as today, and that a methane haze layer separated this oxygen-rich upper layer from the oxygen-starved lower atmosphere.

Dr Tomkins explained how the team extracted micrometeorites from samples of ancient limestone collected in the Pilbara region in Western Australia and examined them at the Monash Centre for Electron Microscopy (MCEM) and the Australian Synchrotron.

"Using cutting-edge microscopes we found that most of the micrometeorites had once been particles of metallic iron -- common in meteorites -- that had been turned into iron oxide minerals in the upper atmosphere, indicating higher concentrations of oxygen than expected," Dr Tomkins said.

"This was an exciting result because it is the first time anyone has found a way to sample the chemistry of the ancient Earth's upper atmosphere," Dr Tomkins said.

Imperial College researcher Dr Matthew Genge -- an expert in modern cosmic dust -- performed calculations that showed oxygen concentrations in the upper atmosphere would need to be close to modern day levels to explain the observations.

"This was a surprise because it has been firmly established that the Earth's lower atmosphere was very poor in oxygen 2.7 billion years ago; how the upper atmosphere could contain so much oxygen before the appearance of photosynthetic organisms was a real puzzle," Dr Genge said.

Dr Tomkins explained that the new results suggest the Earth at this time may have had a layered atmosphere with little vertical mixing, and higher levels of oxygen in the upper atmosphere produced by the breakdown of CO 2 by ultraviolet light.

"A possible explanation for this layered atmosphere might have involved a methane haze layer at middle levels of the atmosphere. The methane in such a layer would absorb UV light, releasing heat and creating a warm zone in the atmosphere that would inhibit vertical mixing," Dr Tomkins said.

"It is incredible to think that by studying fossilised particles of space dust the width of a human hair, we can gain new insights into the chemical makeup of Earth's upper atmosphere, billions of years ago." Dr Tomkins said.

Dr Tomkins outlined next steps in the research.

"The next stage of our research will be to extract micrometeorites from a series of rocks covering over a billion years of Earth's history in order to learn more about changes in atmospheric chemistry and structure across geological time. We will focus particularly on the great oxidation event, which happened 2.4 billion years ago when there was a sudden jump in oxygen concentration in the lower atmosphere."

Source: Monash University [May 12, 2016]

Ancient Britons may have intentionally mummified some of their dead during the Bronze Age, according to archaeologists at the University of Sheffield.

The study, published in the Antiquity Journal, is the first to provide indications that mummification may have been a wide-spread funerary practise in Britain.

Working with colleagues from the University of Manchester and University College London, Dr Tom Booth analysed skeletons at several Bronze Age burial sites across the UK. The team from the University of Sheffield’s Department of Archaeology found that the remains of some ancient Britons are consistent with a prehistoric mummy from northern Yemen and a partially mummified body recovered from a sphagnum peat bog in County Roscommon, Ireland.

Building on a previous study conducted at a single Bronze Age burial site in the Outer Hebrides, Dr Booth used microscopic analysis to compare the bacterial bioerosion of skeletons from various sites across the UK with the bones of the mummified bodies from Yemen and Ireland.

Archaeologists widely agree that the damp British climate is not favourable to organic materials and all prehistoric mummified bodies that may be located in the UK will have lost their preserved tissue if buried outside of a preservative environment such as a bog.

Dr Booth, who is now based at the Department of Earth Sciences at London’s Natural History Museum, said: “The problem archaeologists face is finding a consistent method of identifying skeletons that were mummified in the past – especially when they discover a skeleton that is buried outside of a protective environment.

“To help address this, our team has found that by using microscopic bone analysis archaeologists can determine whether a skeleton has been previously mummified even when it is buried in an environment that isn’t favourable to mummified remains.

“We know from previous research that bones from bodies that have decomposed naturally are usually severely degraded by putrefactive bacteria, whereas mummified bones demonstrate immaculate levels of histological preservation and are not affected by putrefactive bioerosion.”

Earlier investigations have shown that mummified bones found in the Outer Hebrides were not entirely consistent with mummified remains found elsewhere because there wasn’t a complete absence of bacterial bioerosion.

However, armed with a new technique, the team were able to re-visit the remains from the Outer Hebrides and use microscopic analysis to test the relationship between bone bioerosion and the extent of soft tissue preservation in bone samples from the Yemeni and Irish mummies.

Their examinations revealed that both the Yemeni and Irish mummies showed limited levels of bacterial bioerosion within the bone and therefore established that the skeletons found in the Outer Hebrides as well as other sites across Britain display levels of preservation that are consistent with mummification.

The research team also found that the preservation of Bronze Age skeletons at various sites throughout the UK is different to the preservation of bones dating to all other prehistoric and historic periods, which are generally consistent with natural decomposition. Furthermore, the Sheffield-led researchers also found that Bronze Age Britons may have used a variety of techniques to mummify their dead.

Dr Booth added, “Our research shows that smoking over a fire and purposeful burial within a peat bog are among some of the techniques ancient Britons may have used to mummify their dead. Other techniques could have included evisceration, in which organs were removed shortly after death.

“The idea that British and potentially European Bronze Age communities invested resources in mummifying and curating a proportion of their dead fundamentally alters our perceptions of funerary ritual and belief in this period.”

The research also demonstrates that funerary rituals that we may now regard as exotic, novel and even bizarre were practised commonly for hundreds of years by our predecessors.

Also, this method of using microscopic bone analysis to identify formerly-mummified skeletons means that archaeologists can continue searching for Bronze Age mummies throughout Europe.

“It’s possible that our method may allow us to identify further ancient civilisations that mummified their dead,” Dr Booth concluded.

Source: University of Sheffield [September 30, 2015]

Archaeologists have created a new database from the teeth of prehistoric humans found at ancient burial sites in Britain and Ireland that tell us a lot about their climate, their diet and even how far they may have travelled. In a paper, led by Dr Maura Pellegrini from the University of Oxford, researchers say that individuals in prehistoric Britain were highly mobile.

The study is part of the international Beaker People project lead by Professor Mike Parker Pearson of University College London, and involves scientists from many institutions, including the universities of Oxford, Durham, Bradford, University College London, and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The paper says most of the teeth in the collection date back to Chalcolithic and Early Bronze Age periods (from 2500 to 1500 BC) and the analysis, published in the journal >Scientific Reports, suggests not only were people moving around their own country but may also have travelled to and from continental Europe.

Researchers describe how tests on tooth fragments using an oxygen isotope analysis of tooth enamel provides evidence of where an individual lived when the tooth formed. Oxygen, a naturally occurring element in the environment, is absorbed by plants and animals and fixed in the mineral component of mammalian teeth, with an isotopic composition related to the environment in which that individual spent their childhood.  Based on the theory that prehistoric people would have sourced water and food locally, the team were able to geographically map the oxygen isotopic variability in the landscape of Britain and Ireland thereby providing a guide to where individuals sampled had lived as children.

An analysis of the teeth of those buried in the Stonehenge region, the Peak District, and the hills of the Yorkshire Wolds (in East Riding and North Yorkshire) show many were not 'local' to their final resting place. They were drawn from far and wide, sometimes to focal points containing sacred monuments. The variability in the isotope values was found to be particularly marked in individuals recovered from Woodhenge, a timber circle situated near Stonehenge; Bee Low, a Bronze Age round cairn in the Peak District, and Garton Slack in Yorkshire where there is a complex range of barrow types and burial practices.

Tooth enamel fragments from 261 individual teeth were tested with researchers focusing on the central part of the tooth crown in each case. The teeth sampled from these individuals mineralise from the age of two years up to 8 years old, providing the clues to the environmental conditions, including the water they drank as a child. The possibility that people were outsiders who came into areas where they eventually died was calculated by comparing their values with the 'isoscape' information gleaned from most of the other samples in each area, as it was assumed the latter represented 'local' individuals. As individuals' signatures in the teeth were matched with areas where the majority, or 'local' people, were found, the researchers identified those who had lived in other areas as children.

Source: University of Oxford [October 08, 2016]

The transition from hunter-gatherer to sedentary farming 10,000 years ago occurred in multiple neighbouring but genetically distinct populations according to research by an international team including UCL.

“It had been widely assumed that these first farmers were from a single, genetically homogeneous population. However, we’ve found that there were deep genetic differences in these early farming populations, indicating very distinct ancestries,” said corresponding author Dr Garrett Hellenthal, UCL Genetics.

The study, published today in >Science and funded by Wellcome and Royal Society, examined ancient DNA from some of the world’s first farmers from the Zagros region of Iran and found it to be very different from the genomes of early farmers from the Aegean and Europe. The team identified similarities between the Neolithic farmer’s DNA and that of living people from southern Asia, including from Afghanistan, Pakistan, Iran, and Iranian Zoroastrians in particular.

“We know that farming technologies, including various domestic plants and animals, arose across the Fertile Crescent, with no particular centre” added co-author Professor Mark Thomas, UCL Genetics, Evolution & Environment.

“But to find that this region was made up of highly genetically distinct farming populations was something of a surprise. We estimated that they separated some 46 to 77,000 years ago, so they would almost certainly have looked different, and spoken different languages. It seems like we should be talking of a federal origin of farming.”

The switch from mobile hunting and gathering to sedentary farming first occurred around 10,000 years ago in south-western Asia and was one of the most important behavioural transitions since humans first evolved in Africa some 200,000 years ago. It led to profound changes in society, including greater population densities, new diseases, poorer health, social inequality, urban living, and ultimately, the rise of ancient civilizations.

Animals and plants were first domesticated across a region stretching north from modern-day Israel, Palestine and Lebanon to Syria and eastern Turkey, then east into, northern Iraq and north-western Iran, and south into Mesopotamia; a region known as the Fertile Crescent.

“Such was the impact of farming on our species that archaeologists have debated for more than 100 years how it originated and how it was spread into neighbouring regions such as Europe, North Africa and southern Asia,” said co-author Professor Stephen Shennan, UCL Institute of Archaeology.

“We’ve shown for the first time that different populations in different parts of the Fertile Crescent were coming up with similar solutions to finding a successful way of life in the new conditions created by the end of the last Ice Age.”

By looking at how ancient and living people share long sections of DNA, the team showed that early farming populations were highly genetically structured, and that some of that structure was preserved as farming, and farmers, spread into neighbouring regions; Europe to the west and southern Asia to the east.

“Early farmers from across Europe, and to some extent modern-day Europeans, can trace their DNA to early farmers living in the Aegean, whereas people living in Afghanistan, Pakistan, Iran and India share considerably more long chunks of DNA with early farmers in Iran. This genetic legacy of early farmers persists, although of course our genetic make-up subsequently has been reshaped by many millennia of other population movements and intermixing of various groups,” concluded Dr Hellenthal.

Source: University College London [July 14, 2016]

Mammals immortalise their genes through eggs and sperm to ensure future generations inherit good quality mitochondria to power the body's cells, according to new UCL research.

Before now, it was not known why mammals rely on dedicated sex cells that are formed early in development (a germline) to make offspring whereas plants and other simple animals, such as corals and sponges, use sex cells produced later in life from normal body tissues.

In a new study, published today in >PLOS Biology and funded by Natural Environment Research Council, Engineering & Physical Sciences Research Council and the Leverhulme Trust, UCL scientists developed an evolutionary model to investigate how these differences evolved over time and discovered that the germline in mammals developed in response to selection on mitochondria (the powerhouses of cells).

First author and UCL PhD student, Arunas Radzvilavicius, said: "There have been many theories about why mammals have a specialised germline when plants and other ancient animals don't. Some suggest it was due to complexity of tissues or a selfish conflict between cells. The distinction between sex cells and normal body tissues seems to be necessary for the evolution of very complex specialised tissues like brain.

"Surprisingly, we found that these aren't the reason. Rather, it's about the number of genetic mutations in mitochondrial DNA over time, which differs between organisms, and the variation between cells caused by the mitochondria being randomly partitioned into daughter cells at each division."

In plants, mitochondrial mutations creep in slowly, so a germline isn't needed as mutations are corrected by natural selection. Mitochondrial variation is maximised by forming the next generation from the same cells used to make normal tissue cells. When the cells divide to form new daughter cells, some receive more mutant mitochondria than others and these cells are then removed through natural selection, preserving the reproductive cells containing higher quality mitochondria.

In mammals, genetic errors in mitochondria accumulate more quickly due to our higher metabolic rate so using cells that have undergone lots of division cycles would be a liability. Mitochondria are therefore only passed along to the next generation through a dedicated female germline in the form of large eggs. This protects against errors being introduced as eggs undergo many fewer replication cycles than cells in other tissues such as the gut, skin and blood.

The germline ensures that the best quality mitochondria are transferred but restricts the genetic variation in the next generation of cells in the developing embryo. This is corrected for by mammals generating far too many egg cells which are removed during development. For example, humans are born with over 6 million egg-precursor cells, 90% of which are culled by the start of puberty in a mysterious process called atresia.

Senior author, Dr Nick Lane (UCL CoMPLEX and Genetics, Evolution & Environment) added: "We think the rise in mitochondrial mutation rate likely occurred in the Cambrian explosion 550 million years ago when oxygen levels rose. This was the first appearance of motile animals in the fossil record, things like trilobites that had eyes and armour plating - predators and prey. By moving around they used their mitochondria more and that increased the mutation rate. So to avoid these mutations accumulating they needed to have fewer rounds of cell division, and that meant sequestering a specialized germline."

Co-author, Professor Andrew Pomiankowski (UCL Genetics, Evolution & Environment), concluded: "Without a germline, animals with complex development and brains could not exist. Scientists have long tried to explain the evolution of the germline in terms of complexity. Who would have thought it arose from selection on mitochondrial genes? We hope our discovery will transform the way researchers understand animal development, reproduction and aging."

Source: University College London [December 20, 2016]

Scientists have discovered that the mineral jarosite breaks down organic compounds when it is flash-heated, with implications for Mars research.

Jarosite is an iron sulphate and it is one of several minerals that NASA’s Curiosity Mission is searching for, as its presence could indicate ancient habitable environments, which may have once hosted life on the red planet.

In a new study published today in the journal Astrobiology, researchers from Imperial College London and the Natural History Museum replicated a technique that one of the Curiosity Rover’s on-board instruments is using to analyse soil samples, in its quest to find organic compounds. They tested a combination of jarosite and organic compounds. They discovered that the instrument’s technique -which uses intense bursts of heat called flash-heating – broke down jarosite into sulphur dioxide and oxygen, with the oxygen then destroying the organic compounds, leaving no trace of it behind.

The concern is that if jarosite is present in soil samples that Curiosity analyses, researchers may not be able to detect it because both the jarosite and any organic compounds could be destroyed by the flash-heating process.

In 2014, Professor Mark Sephton, co-author of today’s study, investigated the mineral perchlorate. This mineral also causes problems for flash-heating experiments as it breaks down to give off oxygen and chlorine gas, which in turn react with any organic compounds, breaking them down into carbon dioxide and water. Professor Sephton showed that though perchlorate was problematic, scientists could potentially use the carbon dioxide resulting from the experiment to detect the presence of organic compounds in the sample being analysed.

Professor Sephton, from the Department of Earth Science and Engineering at Imperial College London, said: “The destructive properties of some iron sulphates and perchlorate to organic matter may explain why current and previous missions have so far offered no conclusive evidence of organic matter preserved on Mars’ surface. This is despite the fact that scientists have known from previous studies that organic compounds have been delivered to Mars via comets, meteorites and interplanetary dust throughout its history.”

To make Curiosity’s search for signs of life more effective, the team are now exploring how Curiosity might be able to compensate for the impact of these minerals on the search for organic compounds. Their work could have important implications for both the Curiosity mission and also the upcoming European-led ExoMars 2018 Rover mission, which will be drilling for subsurface samples of the red planet and using the same flash-heating method to look for evidence of past or present alien life.

James Lewis, co-author of the study from the Department of Earth Science and Engineering at Imperial College London, added: “Our study is helping us to see that if jarosite is detected then it is clear that flash-heating experiments looking for organic compounds may not be completely successful. However, the problem is that jarosite is evidence of systems that might have supported life, so it is not a mineral that scientists can completely avoid in their analysis of soils on Mars. We hope our study will help scientists with interpreting Mars data and assist them to sift through the huge amount of excellent data that Curiosity is currently generating to find signs that Mars was once able to sustain life.”

On Earth, iron sulphate minerals like jarosite form in the harsh acidic waters flowing out of sulphur rich rocks. Despite the adverse conditions, these waters are a habitat for bacteria that use these dissolved sulphate ions. This makes these minerals of great interest to scientists studying Mars, as their presence on the red planet provide evidence that acidic liquid water was present at the same time the minerals formed, which could have provided an environment favourable for harbouring ancient microbial Martian life.

On board Curiosity, the Sample Analysis at Mars (SAM) instrument analyses soil samples for evidence of organic compounds by progressively heating samples up to around 1000 C, which releases gases. These gases can then be analysed by techniques called gas chromatography and mass spectrometry, which can identify molecules in the gas and see if any organic compounds are present. It is these SAM instrument experiments that the researchers behind today’s study replicated with jarosite and organic compounds.

The researchers stress that not all sulphates break down to react with organic compounds. For example, those containing calcium and magnesium would not break down until extremely high temperatures were reached during the analysis, and therefore would not affect any organic compounds present.

The team suggest that if jarosite is found in samples on Mars, then it may be possible for Curiosity’s SAM instrument to distinguish a spike in carbon dioxide level, which, as Professor Sephton has shown previously with perchlorate, would act as an indicator that organic material is present and being broken down by the heating process.

The next step will see the researchers using synthetic jarosite in their experiments, which will enable a cleaner decomposition process to occur when the mineral is flash-heated. This will allow for more precise quantitative measurements to be taken when the oxygen is being released. Ultimately, they hope this will enable more precise calculations to be carried out on Mars mineral samples to find ways in which Curiosity can identify the presence of these mineral to mitigate their impact on organic matter.

The jarosite samples used in the experiments in the study were collected from Brownsea Island in Dorset, with the permission and assistance from the National Trust.

Source: Imperial College London [February 19, 2015]

An unidentified fossilised bone in a museum has revealed the size of a fearsome abelisaur and may have solved a hundred-year old puzzle.

Alessandro Chiarenza, a PhD student from Imperial College London, last year stumbled across a fossilised femur bone, left forgotten in a drawer, during his visit to the Museum of Geology and Palaeontology in Palermo Italy. He and a colleague Andrea Cau, a researcher from the University of Bologna, got permission from the museum to analyse the femur. They discovered that the bone was from a dinosaur called abelisaur, which roamed the Earth around 95 million years ago during the late Cretaceous period.

Abelisauridae were a group of predatory, carnivorous dinosaurs, characterised by extremely small forelimbs, a short deep face, small razor sharp teeth, and powerful muscular hind limbs. Scientists suspect they were also covered in fluffy feathers. The abelisaur in today's study would have lived in North Africa, which at that time was a lush savannah criss-crossed by rivers and mangrove swamps. This ancient tropical world would have provided the abelisaur with an ideal habitat for hunting aquatic animals like turtles, crocodiles, large fish and other dinosaurs.

By studying the bone, the team deduced that this abelisaur may have been nine metres long and weighed between one and two tonnes, making it potentially one of the largest abelisaurs ever found. This is helping researchers to determine the maximum sizes that these dinosaurs may have reached during their peak.

Alfio Alessandro Chiarenza, co-author of the study from the Department of Earth Science and Engineering at Imperial, said: "Smaller abelisaur fossils have been previously found by palaeontologists, but this find shows how truly huge these flesh eating predators had become. Their appearance may have looked a bit odd as they were probably covered in feathers with tiny, useless forelimbs, but make no mistake they were fearsome killers in their time."

The fossil originated from a sedimentary outcrop in Morocco called the Kem Kem Beds, which are well known for the unusual abundance of giant predatory dinosaur fossils. This phenomenon is called Stromer's Riddle, in honour the German palaeontologist Ernst Stromer, who first identified this abundance in 1912. Since then scientists have been asking how abelisaurs and five other groupings of predatory dinosaurs could have co-existed in this region at the same time, without hunting each other into extinction.

Now the researchers in today's study suggest that these predatory dinosaur groups may not have co-existed so closely together. They believe that the harsh and changing geology of the region mixed the fossil fragment records together, destroying its chronological ordering in the Kem Kem beds, and giving the illusion that the abelisaurs and their predatory cousins shared the same terrain at the same time. Similar studies of fossil beds in nearby Tunisia, for example, show that creatures like abelisaurs were inland hunters, while other predators like the fish eating spinosaurs probably lived near mangroves and rivers.

Chiarenza added: "This fossil find, along with the accumulated wealth of previous studies, is helping to solve the question of whether abelisaurs may have co-existed with a range of other predators in the same region. Rather than sharing the same environment, which the jumbled up fossil records may be leading us to believe, we think these creatures probably lived far away from one another in different types of environments."

Fossilised femora are useful for palaeontologists to study because they can determine the overall size of the dinosaur. This is because femora are attached to the thigh and tail muscles and have scars, or bumps, which tell palaeontologists where the ligaments and muscles were attached to the bone and how big those muscles and ligaments would have been.

Andrea Cau, co-author from the University of Bologna, said: "While palaeontologists usually venture to remote and inaccessible locations, like the deserts of Mongolia or the Badlands of Montana, our study shows how museums still play an important role in preserving specimens of primary scientific value, in which sometimes the most unexpected surprises can be discovered. As Stephen Gould, an influential palaeontologist and evolutionary biologist, once said, sometimes the greatest discoveries are made in museum drawers."

The study is published in the journal Peer J. Chiarenza did the underpinning analysis with Cau while at the University of Bologna.

The next step will see the team looking for more complete remains from these predatory dinosaurs trying to better understand their environment and evolutionary history.

Author: Colin Smith | Source: Imperial College London [February 29, 2016]

The world's largest canyon may lie under the Antarctic ice sheet, according to analysis of satellite data by a team of scientists, led by Durham University.

Although the discovery needs to be confirmed by direct measurements, the previously unknown canyon system is thought to be over 1,000km long and in places as much as 1km deep, comparable in depth to the Grand Canyon in USA, but many times longer.

The canyon system is made up of a chain of winding and linear features buried under several kilometres of ice in one of the last unexplored regions of the Earth's land surface: Princess Elizabeth Land (PEL) in East Antarctica. Very few measurements of the ice thickness have been carried out in this particular area of the Antarctic, which has led to scientists dubbing it one of Antarctica's two 'Poles of Ignorance'.

The researchers believe that the landscape beneath the ice sheet has probably been carved out by water and is either so ancient that it was there before the ice sheet grew or it was created by water flowing and eroding beneath the ice.

Although not visible to the naked eye, the subglacial landscape can be identified in the surface of the ice sheet.

Faint traces of the canyons were observed using satellite imagery and small sections of the canyons were then found using radio-echo sounding data, whereby radio waves are sent through the ice to map the shape of the rock beneath it. These are very large features which appear to reach from the interior of Princess Elizabeth Land to the coast around the Vestfold Hills and the West Ice Shelf.

The canyons may be connected to a previously undiscovered subglacial lake as the ice surface above the lake shares characteristics with those of large subglacial lakes previously identified. The data suggests the area of the lake could cover up to 1250km², more than 80 times as big as Lake Windermere in the English Lake District.

An airborne survey taking targeted radio-echo sounding measurements over the whole buried landscape is now underway with the aim of unambiguously confirming the existence and size of the canyon and lake system, with results due later in 2016.

Lead researcher, Dr Stewart Jamieson, from the Department of Geography at Durham University in the UK, said: "Our analysis provides the first evidence that a huge canyon and a possible lake are present beneath the ice in Princess Elizabeth Land. It's astonishing to think that such large features could have avoided detection for so long.

"This is a region of the Earth that is bigger than the UK and yet we still know little about what lies beneath the ice. In fact, the bed of Antarctica is less well known than the surface of Mars. If we can gain better knowledge of the buried landscape we will be better equipped to understand how the ice sheet responds to changes in climate."

Co-Author Dr Neil Ross from Newcastle University in the UK, said: "Antarctic scientists have long recognised that because the way ice flows, the landscape beneath the ice sheet was subtly reflected in the topography of the ice sheet surface. Despite this, these vast deep canyons and potential large lake had been overlooked entirely.

"Our identification of this landscape has only been possible through the recent acquisition, compilation and open availability of satellite data by many different organisations (e.g. NASA, ESA and the US National Snow and Ice Data Center), to whom we are very grateful, and because of some serendipitous reconnaissance radio-echo sounding data acquired over the canyons by the ICECAP project during past Antarctic field seasons."

Co-Author Professor Martin Siegert, from the Grantham Institute at Imperial College London, UK, said: "Discovering a gigantic new chasm that dwarfs the Grand Canyon is a tantalising prospect. Geoscientists on Antarctica are carrying out experiments to confirm what we think we are seeing from the initial data, and we hope to announce our findings at a meeting of the ICECAP2 collaboration, at Imperial, later in 2016.

"Our international collaboration of US, UK, Indian, Australian and Chinese scientists are pushing back the frontiers of discovery on Antarctica like nowhere else on earth. But the stability of this understudied continent is threatened by global warming, so all the countries of the world now must rapidly reduce their greenhouse gas emissions and limit the damaging effects of climate change."

>The research is >published in >Geology>.

Source: Durham University [January 13, 2016]

When the Black Death swept through Europe in 1347, it was one of the deadliest disease outbreaks in human history, eventually killing between a third and half of Europeans.

Prior work by investigators has traced the cause to plague-carrying fleas borne by rats that jumped ship in trading ports. In addition, historical researchers believe that famine in northern Europe before the plague came ashore may have weakened the population there and set the stage for its devastation.

Now, new research using a unique combination of ice-core data and written historical records indicates that the cool, wet weather blamed for the northern European famine actually affected a much wider area over a much longer period. The work, which researchers say is preliminary, paints a picture of a deep, prolonged food shortage in the years leading to the Black Death.

“The evidence indicates that the famine was a broader phenomenon, geographically and chronologically,” said Alexander More, a postdoctoral fellow in the Harvard History Department and a lecturer in the History of Science Department.

A widespread famine that weakened the population over decades could help explain the Black Death’s particularly high mortality. Over four or five years after arriving in Europe in 1347, the pandemic surged through the continent in waves that killed millions.

The ice-core data is part of a unique program linking traditional historical research with scientific data-collecting techniques. The program, called the Initiative for the Science of the Human Past at Harvard (SoHP), is headed by Michael McCormick, the Francis Goelet Professor of Medieval History. SoHP’s ice-core project is being conducted in collaboration with the University of Maine’s Climate Change Institute and researchers at Heidelberg University. The project’s approach puts it at the juncture of environmental science, archaeology, and history. It is supported by the Arcadia Fund of London.

More presented his findings at a conference in November arranged to discuss the project. Joining him was Harvard junior Matthew Luongo, an Earth sciences and environmental engineering concentrator from Dunster House, who discussed the discovery of volcanic tephra in the ice core. Tephra, microscopic airborne volcanic particles, are generally believed absent from cores in European glaciers, make Luongo’s assumption-puncturing discovery potentially significant.

Luongo spent several days at the Climate Change Institute last summer performing chemical analyses and examining the volcanic bits through a scanning electron microscope. Each volcanic eruption has a slightly different chemical fingerprint, so he was able to trace the tephra to the 1875 Askja eruption in Iceland, one of the largest eruptions there in history.

Since many eruptions were written about contemporaneously, the ice core’s volcanic traces can be used to align ice-core data with written records, providing greater certainty in dating other chemical traces in the ice, such as those from human activities like lead from Roman-era smelting.

“I think it was a really important project,” Luongo said.

McCormick said that the advanced technologies scientists used to understand areas like the human genome and climate change are increasingly being applied to the humanities, and opening new avenues of investigation.

McCormick was part of a team that in 2011 used tree-ring data to reconstruct European climate over the last 2,500 years, showing that the period before the fall of the Roman Empire was marked by wide climactic variability. In November, McCormick summed up the use of climate data in historical research as reading history “from the environment itself.”

“All these things are happening in the sciences and spilling over into the humanities,” McCormick said. “Twenty years ago, if you’d have told me that climate could have caused the collapse of the Roman Empire and that we would have the means to test that, I wouldn’t have believed you.”

The new data emerging from the ice core could be the first of a flood of information about the last millennium and beyond. McCormick’s University of Maine colleagues, led by Paul Mayewski, have developed a laser-based method of ice analysis. It requires far smaller samples of ice and can take 50,000 samples in a one-meter ice core, compared with just 100 in the previous method. The new technology allows much higher resolution analysis of even very thin ice layers — to the specific year and potentially to individual storms — and can go back farther than the 1500 A.D. limit of this glacier with previous techniques.

The ice core was the first ever taken specifically for historical research, McCormick said, and was drilled in 2013 from the Colle Gnifetti glacier, high in the Alps near the Swiss-Italian border. It was divided between partner organizations, with the portion allocated to the Initiative for the Science of the Human Past and the Climate Change Institute being held at the University of Maine.

The findings about the period preceding the Black Death described by More continue to fill in an emerging and newly complex picture of a key period in human history. Recent research has traced the genesis of the European plague to animal groups in Asia and climate-related outbreaks that traveled along Silk Road trade routes.

McCormick said this application of scientific methods opens new avenues of inquiry, akin to discovering colossal collections of historical records, whether read directly from the DNA of ancient people, from the trees that grew at the time, or from the ice deposited in ancient storms.

“It’s a gigantic set of archives that document the least-documented part of [history],” McCormick said. “It’s kind of a renaissance of history.”

Author: Alvin Powell | Source: Harvard University [January 07, 2016]

Fluctuating sea levels and global cooling caused a significant decline in the number of crocodylian species over millions of years, according to new research.

Crocodylians include present-day species of crocodiles, alligators, caimans and gavials and their extinct ancestors. Crocodylians first appeared in the Late Cretaceous period, approximately 85 million years ago, and the 250 million year fossil record of their extinct relatives reveals a diverse evolutionary history.

Extinct crocodylians and their relatives came in all shapes and sizes, including giant land-based creatures such as Sarcosuchus, which reached around 12 metres in length and weighed up to eight metric tonnes. Crocodylians also roamed the ocean -- for example, thalattosuchians were equipped with flippers and shark-like tails to make them more agile in the sea.

Many crocodylians survived the mass extinction that wiped out almost all of the dinosaurs 66 million years ago, but only 23 species survive today, six of which are classified by the International Union for Conservation of Nature as critically endangered and a further four classified as either endangered or vulnerable.

In a new study published in Nature Communications, researchers from Imperial College London, the University of Oxford, the Smithsonian Institution and the University of Birmingham compiled a dataset of the entire known fossil record of crocodylians and their extinct relatives and analysed data about Earth's ancient climate. They wanted to explore how the group responded to past shifts in climate, to better understand how the reptiles may cope in the future.

Crocodylians are ectotherms, meaning they rely on external heat sources from the environment such as the Sun. The researchers conclude that at higher latitudes in areas we now know as Europe and America, declining temperatures had a major impact on crocodylians and their relatives.

At lower latitudes the decline of crocodylians was caused by areas on many continents becoming increasingly arid. For example, in Africa around ten million years ago, the Sahara desert was forming, replacing the vast lush wetlands in which crocodylians thrived. In South America, the rise of the Andes Mountains led to the loss of a proto-Amazonian mega wetland habitat that crocodylians lived in around five million years ago.

Marine species of crocodylians were once widespread across the oceans. The team found that fluctuations in sea levels exerted the main control over the diversity of these creatures. For example, at times when the sea level was higher it created greater diversity because it increased the size of the continental shelf, providing the right conditions near the coast for them and their prey to thrive.

Interestingly, the Cretaceous-Paleogene mass extinction event, which wiped out many other creatures on Earth nearly 66 million years ago including nearly all of the dinosaurs, had positive outcomes for the crocodylians and their extinct relatives. The team found that while several groups did go extinct, the surviving groups rapidly radiated out of their usual habitats to take advantage of territories that were now uninhabited.

In the future, the team suggest that a warming world caused by global climate change may favour crocodylian diversification again, but human activity will continue to have a major impact on their habitats.

Dr Philip Mannion, joint lead author from the Department of Earth Science and Engineering at Imperial College London, said: "Crocodylians are known by some as living fossils because they've been around since the time of the dinosaurs. Millions of years ago these creatures and their now extinct relatives thrived in a range of environments that ranged from the tropics, to northern latitudes and even deep in the ocean. However, all this changed because of changes in the climate, and crocodylians retreated to the warmer parts of the world. While they have a fearsome reputation, these creatures are vulnerable and looking back in time we've been able to determine what environmental factors had the greatest impact on them. This may help us to determine how they will cope with future changes."

The next step for the researchers will be for them to look at similar patterns in other fossil groups with long histories, such as mammals and birds to determine how past climate influenced them.

Source: Imperial College London [September 24, 2015]

The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, according to new research published today in Nature.

Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. Human actions are now changing the planet, but are we really a geological force of nature driving Earth into a new epoch that will last millions of years?

Scientists at UCL have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.

Defining an epoch requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. Such a marker -- like the chemical signature left by the meteorite strike that wiped out the dinosaurs -- is called a golden spike.

The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria: 1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth's history.

They argue that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries. This irreversible exchange of species satisfies the first criteria for dating an epoch -- long-term changes to Earth.

The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right -- as Earth-changing as a meteorite strike

The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.

The researchers have named the 1610 dip in carbon dioxide the 'Orbis Spike'. They chose the Latin word for 'world' because this golden spike was caused by once-disconnected peoples becoming globally linked.

Lead author, Dr Simon Lewis (UCL Geography and University of Leeds), said: "In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right -- as Earth-changing as a meteorite strike."

He added: "Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth's last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene."

The authors also considered the merits of dating the Anthropocene to 1964, which saw a peak in radioactive fallout following nuclear weapons testing. This marker is seen in many geological deposits, and by the 1960s human impact on the Earth was large. However, the researchers note that while nuclear war could dramatically alter Earth, so far it has not. While the fallout from nuclear bomb tests is a very good marker, the testing of nuclear weapons has not been -- in geological terms -- an Earth-changing event.

The beginning of the Industrial Revolution, in the late 18th century, has most commonly been suggested as the start of the Anthropocene. This linked a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. However, the researchers did not find a golden spike at that time because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker.

The authors' new paper ends by highlighting some implications of formally defining the Anthropocene.

Co-author, geologist Professor Mark Maslin (UCL Geography) said: "A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognising it."

An official decision on whether to formally recognise the Anthropocene, including when it began, will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy, due in 2016.

Source: University College London [March 11, 2015]