An international group of specialists in the field of planetary sciences has found strong evidence that lava flows on Mars may also host base and precious metals.
The Martian surface geology is dominated by volcanic rocks, which are broadly similar to ancient lava flows on earth, such as komatiites and ferropicrites.
On Earth, these rocks are significant hosts of precious and base metals such as nickel, copper and the immensely valuable platinum group elements.
In a paper published online today in Ore Geology Reviews Professor Marco Fiorentini and Ph.D. researcher Raphael Baumgartner, from the Centre for Exploration Targeting (CET) at The University of Western Australia and the ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), together with an international group, present their findings on whether lava flows on the Red Planet also host base and precious metals.
“We found strong evidence that mechanisms crucial in the formation of ore deposits on Earth also acted on our neighbour planet, where lava flows may have formed base and precious metal rich mineralisation,” Ph.D. researcher Raphael Baumgartner said.
The study’s lead scientist and project coordinator, Professor Marco Fiorentini, added: “Answering the question of whether this style of mineralisation also exists on Mars offers a chance to enhance our fundamental understanding of the processes governing the evolution of such mineral systems on Earth – improving the scientific foundation upon which mineral exploration models are built.”
David Baratoux, a project collaborator from the Université de Toulouse, said the outcomes of the study provide a comprehensive foundation for further research targeting individual Martian igneous provinces to host precious and base metal rich mineralisation.
“As a first step, we examined the prospectivity of Mars at the planetary scale. We are confident that our future work will shed light on specific settings where these mineralised occurrences likely occur on Mars,” he said.
Kerim Sener, a project sponsor from Matrix Exploration Pty. Ltd., a private mineral resources consultancy, emphasised the importance of the research for future Martian exploration.
“Understanding how and where potential ore forming processes occurred on Mars is a prerequisite for long-term planning for future space missions to the planet and for designing exploration criteria for certain sample-return programmes,” he said.
The Martian geology is surprisingly well documented. Orbiting satellites have imaged and analysed Mars surface remotely, Landers and Rovers have directly observed and analysed the Martian surface, and even limited rock specimens are available to the scientific community – with the Martian meteorites representing fragments of the Martian crust ejected by asteroid impacts.
Baumgartner RJ, Fiorentini M, Baratoux D, Micklethwaite S, Lorand JP, Sener AK, McCuaig C. Magmatic Controls on the Genesis of Ni-Cu±(PGE) Sulphide Mineralisation on Mars. Ore Geology Reviews (in press).
Chemical Formula: Au Locality: Sierra Nevada Mountains, Nome, Alaska and many other places in the world. Name Origin: Anglo Saxon, of uncertain origin.
Gold is a chemical element with symbol Au (from Latin: aurum) and atomic number 79. It is a bright yellow dense, soft, malleable and ductile metal. The properties remain when exposed to air or water. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements, and is solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains, in rocks, in veins and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).
Gold’s atomic number of 79 makes it one of the higher atomic number elements that occur naturally in the universe, and is traditionally thought to have been produced in supernova nucleosynthesis to seed the dust from which the Solar System formed. Because the Earth was molten when it was just formed, almost all of the gold present in the Earth sank into the planetary core. Therefore most of the gold that is present today in the Earth’s crust and mantle is thought to have been delivered to Earth later, by asteroid impacts during the late heavy bombardment, about 4 billion years ago.
Gold resists attacks by individual acids, but it can be dissolved by aqua regia (nitro-hydrochloric acid), so named because it dissolves gold into a soluble gold tetrachloride cation. Gold compounds also dissolve in alkaline solutions of cyanide, which have been used in mining. It dissolves in mercury, forming amalgam alloys; it is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to confirm the presence of gold in items, giving rise to the term acid test.
Dinosaur footprints at Gantheaume Point near Broome. Credit: Bjarni Thorbjornsson
While audiences in Perth attend Walking with Dinosaurs this weekend palaeontologists working near Broome will be documenting the extinct vertebrates’ extensive fossilised footsteps using laser scanning technology.
The researchers are using the hand-held scanner Zebedee to help build three-dimensional images of the prints, as part of the government-funded Walking with Dinosaurs in the Kimberley project.
Queensland University senior lecturer Steven Salisbury is leading the project.
He returned to Broome this week, to take advantage of massive tides (up to 12m) at this time of year which expose tracks on rock platforms which are mostly underwater.
He says it is an intense period of research, trying to gather as much data as possible at low tide for interpretation back in the laboratory.
Dr Salisbury says some areas are exposed just a few hours, a few days of the year.
“So we don’t get many chances,” he says.
“At one time in the past, you’d have been able to lay out some tape measures and transect line and using some graph paper go about casually recording it but we can’t do that here because we’d be washed away.”
Previous expeditions have used on-ground and aerial photography from drones and aircraft and photogrammetry to build-up 3D images but it is the first time Zebedee has been deployed.
It is a lightweight LiDAR laser scanner developed by CSIRO that fires lasers into the atmosphere from a spinning mirror. Distance is measured when the lasers bounce back.
The scanner earned its name from the spring-loaded children’s TV character Zebedee from The Magic Roundabout.
Dr Salisbury says Zebedee is better suited to 3D spaces like caves and its use on flat terrain has needed some modifications.
However, the results are very exciting.
“The more you do it, the bigger the three dimensional point cloud and you can build-up a three-dimensional terrain,” he says
“What we are doing now is trying to overlay the three dimensional photographs into that terrain.
“We obviously have a lot of processing and cataloguing to do back at the uni but already we are able to do a lot of work with what we’ve got.
“Two student on the team are working on interpreting one of the nice sauropod track site close to Broome which we haven’t been able to do previously because it’s too tricky with tides and the extent of the track sites.
Dr Salisbury says the Kimberley has the only example of Australian dinosaurs, up to 20 different types, from 130 million years ago.
An ancient footprint from Ileret, Kenya: one of several sets showing evidence of Homo erectus males travelling in groups. Credit: Brian Richmond
A long-past hunting party left a permanent sign of its outing — and it was not empty beer cans. Dozens of 1.5-million-year-old human footprints in Kenya may be evidence of an early antelope hunt, offering a rare look at the lives of ancient humans, researchers reported at a conference in California this week.
Footprints are the rarest of human relics. They tend to erode away very quickly; only the choicest of conditions keep them preserved for thousands or millions of years. But unlike collections of bones and tools — which are difficult to link to a single individual or group — footprints offer a snapshot of daily life.
In the late 2000s, researchers exploring the area near a village in northwestern Kenya, called Ileret, for human bones and tools instead stumbled on a collection of 22 human footprints. Their 2009 publication on the discovery, in Science1, focused on the anatomy of the people who left the prints: tall individuals who probably belonged to the species Homo erectus, and who walked very much like modern humans (Homo sapiens).
But Neil Roach, a palaeoanthropologist at the American Museum of Natural History in New York, saw the prints as an opportunity to catch a glimpse in the day of a life of Homo erectus. He and his colleagues returned to Ileret to take a closer look at the prints and to search for more.
They have now found around 100 human footprints, split between several sets that were probably each laid down on the same day. Roach says that the prints represent groups of multiple individuals, rather than lone ramblers. The size of the prints point to adult males, he told the annual meeting of the Paleoanthropology Society in San Francisco.
One direction
To get a better sense of the purpose of these jaunts, Roach and his colleagues looked at the prints of other animals, including crocodiles, antelopes and other bovids, and birds such as storks and pelicans. This mix suggests that the ancient humans were walking on a lakeside buffered by grasslands, Roach says. And unlike the grass-eating bovids, whose prints tended to lead from the grasslands to the lake shore, the humans all walked in one direction along the lake — similar to the movements of other hunting animals.
Roach and his team propose that the tracks represent group hunts for antelope or wildebeest. “What we can say is that we have a number of individuals, probably males, that are moving across a lake shore in a way that is consistent with how carnivores move,” he says. The researchers now plan to study the movement patterns of present-day subsistence hunters in Africa to get a better idea of what their footprints look like. “Hunting is a difficult thing to prove in human evolution,” Roach says. The presence of numerous adult males also points to some level of cooperation.
Other evidence suggests that Homo erectus — a forebear to modern Homo sapiens — were more predatory than their ancestors, who may have scavenged the meat that they ate. Stone tools and cut-marked bones become more common in the archaeological record after around 2 million years ago (when Homo erectus emerged). And some researchers have speculated that their svelte bodies helped them to track down fast-moving prey, while their bulging brains demanded loads of calories. “There’s starting to be a consensus that around 2 million years ago we see more carnivory that has to do with hunting,” Roach says.
“Who knows what they’re doing there,” says Curtis Marean, a palaeoanthropologist at Arizona State University in Tempe. “It could be a group hunt, but it could also be lakeshore foraging.” Some lakeshore plants produce nutritious bulbs on which the footprint-makers may have gorged.
But Marean thinks that Roach and his team are onto something by using footprints to study daily life. “It’s a completely novel piece of data,” he says. “I think it’s a really interesting way to get an angle on what communities were doing in the past.”
Note : The above story is based on materials provided by Nature
This marine scene shows an assortment of marine tetrapods that lived in Cretaceous oceans near the end of the “Age of Reptiles,” including a sea turtle, an early flightless marine bird, a large mosasaur and a long-necked elasmosaur. Artwork by Karen Carr
For more than 250 million years, four-limbed land animals known as tetrapods have repeatedly conquered the Earth’s oceans. These creatures–such as plesiosaurs, penguins and sea turtles–descended from separate groups of terrestrial vertebrates that convergently evolved to thrive in aquatic environments.
In a new scientific review, a team of Smithsonian scientists synthesized decades of scientific discoveries to illuminate the common and unique patterns driving the extraordinary transitions that whales, dolphins, seals and other species underwent as they moved from land to sea. Drawing on recent breakthroughs in diverse fields such as paleontology, molecular biology and conservation ecology, their findings offer a comprehensive look at how life in the ocean has responded to environmental change over time. The paper also highlights how evolutionary history informs an understanding of the impact of human activities on marine species today. More information is available in the April 17 issue of Science.
Marine tetrapods represent a diverse group of living and extinct species of mammals, reptiles, amphibians and birds that all play–or played–a critical role as large ocean predators in marine ecosystems. The repeated transitions between land and sea have driven innovation, convergence and diversification against a backdrop of changing marine ecosystems and mass extinctions dating back to the Triassic period. In this way, they provide ideal models for testing hypotheses about the evolution of species over long periods of time. Modern species of marine tetrapods now face a suite of human-driven impacts to their environment, including climate change, habitat degradation, ship collisions and underwater noise.
“We know from the fossil record that previous times of profound change in the oceans were important turning points in the evolutionary history of marine species,” said Neil Kelley, a Peter Buck post-doctoral researcher in the National Museum of Natural History’s department of paleobiology and lead author in the study. “Today’s oceans continue to change, largely from human activities. This paper provides the evolutionary context for understanding how living species of marine predators will evolve and adapt to life in the Anthropocene.”
Recent investigations in the fossil record have provided new insight into the evolution of traits that allowed marine tetrapods to thrive in the sea. In some cases, similar anatomy evolved among lineages that adapted to marine lifestyles. For example, modern dolphins and extinct marine reptiles called ichthyosaurs descended from distinct terrestrial species, but independently converged on an extremely similar fish-like body plan although they were separated in time by more than 50 million years. The repeated transformation of legs adapted for walking on land into fins is another classic example of convergent evolution. Species ranging from seals to mosasaurs independently developed streamlined forelimbs as they transitioned from living on land to the ocean, allowing them to move quickly and efficiently in the water. This transformation may have been achieved by parallel changes at the genome level.
“Land to sea transitions have happened dozens of times among reptiles, mammals and birds, across major mass extinctions,” said Nicholas Pyenson, the museum’s curator of fossil marine mammals. “You often get similar looking results but convergence is more than skin deep. It can be seen on a broad range of scales, from molecules to food webs, over hundreds of millions of years.”
In the case of deep divers such as beaked whales and seals, these species have independently evolved to have positively charged oxygen-binding proteins called myoglobin in their muscles, allowing them to survive underwater for long periods of time. Scientists also have found identical genetic sequences in different marine species, such as whales, seals and sea cows. Whether these invisible molecular similarities account for larger-scale visible patterns of convergent evolution, or whether convergent anatomy follows different genetic pathways in different groups, remains an important open question to be tackled as genomic sequences become available for more species.
Not all adaptations observed in marine tetrapods can be attributed to convergent evolution. For instance, as baleen whales evolved to live underwater, they developed a unique filter-feeding system that depends on hair-like plates instead of teeth. In contrast, toothed whales evolved to catch and feed on prey by emitting calls and using echolocation, a kind of sonar, to process the echoes from these noises and detect objects in the sea.
Kelley and Pyenson synthesized research from existing studies and referenced the Smithsonian’s paleobiology collections during the course of their research. They intend that this comprehensive review will encourage future collaboration between researchers across scientific fields and lead to new insights about evolutionary biology, paleontology and marine conservation.
Reference:
Neil P. Kelley, Nicholas D. Pyenson. Evolutionary innovation and ecology in marine tetrapods from the Triassic to the Anthropocene. Science, 2015 DOI: 10.1126/science.aaa3716
This image shows a meteorite fragment found after a 17-20 meter asteroid disrupted in the atmosphere near Chelyabinsk, Russia on Feb. 15, 2013. Credit: Vishnu Reddy, Planetary Science Institute
Through a combination of data analysis and numerical modeling work, researchers have found a record of the ancient Moon-forming giant impact observable in stony meteorites. Their work will appear in the April 2015 issue of the Journal Science. The work was done by NASA Solar System Exploration Research Virtual Institute (SSERVI) researchers led by Principal Investigator Bill Bottke of the Institute for the Science of Exploration Targets (ISET) team at the Southwest Research Institute and included Tim Swindle, director of the University of Arizona’s Lunar and Planetary Laboratory.
The inner Solar System’s biggest known collision was the Moon-forming giant impact between a large protoplanet and the proto-Earth. The timing of this giant impact, however, is uncertain, with the ages of the most ancient lunar samples returned by the Apollo astronauts still being debated. Numerical simulations of the giant impact indicate this event not only created a disk of debris near Earth that formed the Moon, but it also ejected huge amounts of debris completely out of the Earth-Moon system. The fate of this material, comprising as much as several percent of an Earth mass, has not been closely examined until recently.
However, it is likely some of it blasted main belt asteroids, with a record plausibly left behind in their near-surface rocks. Collisions on these asteroids in more recent times delivered these shocked remnants to Earth, which scientists have now used to date the age of the Moon.
The research indicates numerous kilometer-sized fragments from the giant impact struck main belt asteroids at much higher velocities than typical main belt collisions, heating the surface and leaving behind a permanent record of the impact event. Evidence that the giant impact produced a large number of kilometer-sized fragments can be inferred from laboratory and numerical impact experiments, the ancient lunar impact record itself, and the numbers and sizes of fragments produced by major main belt asteroid collisions.
Once the team concluded that pieces of the Moon-forming impact hit main belt asteroids and left a record of shock heating events in some meteorites, they set out to deduce both the timing and the relative magnitude of the bombardment. By modeling the evolution of giant impact debris over time and fitting the results to ancient impact heat signatures in stony meteorites, the team was able to infer the Moon formed about 4.47 billion years ago, in agreement with many previous estimates. The most ancient Solar System materials found in meteorites are about one hundred million years older than this age.
Insights into the last stages of planet formation in the inner solar system can be gleaned from these impact signatures. For example, the team is exploring how they can be used to place new constraints on how many asteroid-like bodies still existed in the inner Solar System in the aftermath of planet formation. They can also help researchers deduce the earliest bombardment history of ancient bodies like Vesta, one of the targets of NASA’s Dawn mission and a main belt asteroid whose fragments were delivered to Earth in the form of meteorites. It is even possible that tiny remnants of the Moon-forming impactor or proto-Earth might still be found within meteorites that show signs of shock heating by giant impact debris. This would allow scientists to explore for the first time the unknown primordial nature of our homeworld.
Co-author Swindle, who specializes in finding the times when meteorites or lunar samples were involved in large collisions, said: “Bill Bottke had the idea of looking at the asteroid belt to see what effect a Moon-forming giant impact would have, and realized that you would expect a lot of collisions in the period shortly after that.
“Here at LPL, we had been determining ages of impact events that affected meteorites, and when we got together, we found that our data matched his predictions,” he added. “It’s a great example of taking advantage of groups that work in two different specialties — orbital dynamics and chronology — and combining their expertise.”
Intriguingly, some debris may have also returned to hit the Earth and Moon after remaining in solar orbit over timescales ranging from tens of thousands of years to 400 million years.
“The importance of giant impact ejecta returning to strike the Moon could also play an intriguing role in the earliest phase of lunar bombardment,” said Bottke, who is an alumnus of the University of Arizona’s Lunar and Planetary Laboratory. “This research is helping to refine our time scales for ‘what happened when’ on other worlds in the Solar System.”
Yvonne Pendleton, Director of the NASA SSERVI Institute, notes: “This is an excellent example of the power of multidisciplinary science. By linking studies of the Moon, of main belt asteroids, and of meteorites that fall to Earth, we gain a better understanding of the earliest history of our Solar System.”
Video
One possible realization of the Moon-forming impact event is animated. Here it is assumed that a Mars-sized protoplanet, defined as having 13 percent of an Earth-mass, struck the proto-Earth at a 45-degree angle near the mutual escape velocity of both worlds. The “red” particles, comprising 0.3 percent of an Earth-mass, were found to escape the Earth-Moon system. Some of this debris may eventually go on to strike other solar system bodies like large main belt asteroids. “Yellow-green” particles go into the disk that makes the Moon. “Blue” particles were accreted by the proto-Earth. The details of this simulation can be found in Canup, R. (2004, Simulations of a late lunar-forming impact, Icarus 168, 433-456).
Credit: Robin Canup, Southwest Research Institute
Reference:
W. F. Bottke, D. Vokrouhlický, S. Marchi, T. Swindle, E. R. D. Scott, J. R. Weirich, H. Levison. Dating the Moon-forming impact event with asteroidal meteorites. Science, 2015 DOI: 10.1126/science.aaa0602
A key question in the climate debate is how the occurrence and distribution of species is affected by climate change. But without information about natural variation in species abundance it is hard to answer. In a major study, published in the scientific journal Current Biology, researchers can now for the first time give us a detailed picture of natural variation.
The impact of climate change on species occurrence and distribution is a central issue in the climate debate, since human influence on the climate risks posing threats to biodiversity. But until now methods for investigating how natural climate variation in the past has affected the abundance of species have been lacking.
Now, for the first time, Krystyna Nadachowska-Brzyska and Hans Ellegren of Uppsala University’s Evolutionary Biology Centre in collaboration with researchers at the Beijing Genomics Institute, have managed to clarify the issue in detail by analysing the whole genome of some 40 bird species. By studying the genetic variation of DNA molecules, they have succeeded in estimating how common these species were at various points in time, from several million years ago to historical times.
Ellegren says: ‘The majority of all species exhibit cyclical swings in numbers and these swings often coincide with the periods of ice ages.’
During the Quaternary Period (the past two million years, including the Pleistocene epoch, i.e. up to some 11,500 years ago), inland ice periodically spread across large land areas of Earth. Species distribution then became compressed with falling numbers of individuals as a result. When the climate became milder and the ice sheets retreated, many species expanded.
Rising and falling species numbers thus seem to result naturally from climate variation. Nevertheless, Ellegren warns of the effects of human influence on the environments in which many birds live, and in the long term on the climate as well.
‘The last Ice Age (110,000-12,000 years ago) had a particularly heavy impact on birds. Many species suffered their most dramatic falls in numbers then.’
Accordingly, there is a risk of the relatively recent influence exerted by human beings on environments and habitats, and of course the climate, having a particularly adverse effect on species that have already ‘declined’. Anthropogenic impact may therefore be what irrevocably pushes their decline beyond the ‘tipping point’ to eventual extinction.
‘We’ve analysed several species classified as “endangered” in the IUCN Red List of Threatened Species. Several, such as the crested ibis, crowned crane, brown mesite and kea, were already at a low level even before human activities affected their ranges,’ says Ellegren.
The survey, which is based on advanced mathematical calculations of how many individuals of each species have existed at different periods, yielding the genetic variation in the genome that is now observable, is the most extensive of its kind to date.
Reference:
Nadachowska-Brzyska K, Li C, Smeds L, Zhang G & Ellegren H. Temporal Dynamics of Avian Populations during Pleistocene Revealed by Whole-Genome Sequences. Current Biology, April 2015 DOI: 10.1016/j.cub.2015.03.047
This is an 18,000 year-old mastodon molar (Mammut americanum). Credit: Tom Robinette, UC
“The answers to extinction, survival and evolution are right here in the dirt,” says University of Cincinnati Quaternary science researcher Ken Tankersley, associate professor of anthropology and geology. “And we are continually surprised by what we find.”
While many scientists focus on species’ extinction wherever there has been rapid and profound climate change, Tankersley looks closely at why certain species survived.
For many years he has invited students and faculty from archeology and geology, and representatives from the Cincinnati Museum Center and Kentucky State Parks to participate in an in-the-field investigation at a rich paleontological and archeological site not too far from UC’s campus.
Through scores of scientific data extracted from fossilized vegetation and the bones and teeth of animals and humans, Tankersley has been able to trace periods of dramatic climate change, what animals roamed the Earth during those epochs and how they survived. And his most recent evidence reveals when humans came on the scene and how they helped change the environment in Big Bone Lick, Kentucky.
“What we found is that deforestation efforts over 5,000 years ago by humans significantly modified the environment to the degree that the erosion began filling in the Ohio River Valley, killing off much of the essential plant life,” says Tankersley. “At that point animals had to either move, evolve or they simply died off.”
Tankersley will present the culmination of his years of Surviving Climate Change research – including countless hours in the field and in the lab as well as multiple published works – at the Society for American Archeology annual meeting, April 15-19 in San Francisco titled, Quaternary Chronostratigraphy of Big Bone Lick, Kentucky, USA. He also has a paper published online in the March issue of the prestigious journal Quaternary Research titled, “Quaternary chronostratigraphy and stable isotope paleoecology of Big Bone Lick, Kentucky, USA.”
Big Bone Lick (BBL) State Park in north-central Kentucky has over 25,000 years of well-preserved bones, rocks and other archeological treasures that have been easily accessible since the 1700s. But until recently, the evidence for why some of this region’s former inhabitants evolved into present-day animals, while others simply died off, was buried deep in the sediment.
Only 20 minutes away from UC’s main campus by interstate, Tankersley and his students have been taking advantage of BBL’s rich and accessible history for the past three years. By digging through layers of soil, scavenging around in creek bottoms and scraping specimens from bone fragments, they have unearthed a treasure trove of ancient specimens – some more than 25,000 years old.
“One of my students, Stephanie Miller, discovered a 10-foot mastodon tusk beneath the water table at the bottom of a creek when she reached below the mud and felt a hard object pointed at the end,” says Tankersley. “That tusk is now on display at the Cincinnati Museum Center.”
Possessing a proud ancestry of part Native American Cherokee, Tankersley feels a strong need for all this discovery is in his bones, too.
Tankersley originally thought that when the ice reached its maximum advance 25,000 years ago – covering the area now known as Sharonville – the mammoths were grazing on C4 tundra vegetation of herbaceous plants and sedges. To his surprise, what he found is that he couldn’t have been more wrong.
While mammoths and mastodons are two distinct species of the proboscidean family, they were originally thought to have lived in different epochs in time and in separate areas of the world:
Mastodons existed earlier, about 27-30 million years ago primarily in North and Central America.
Mammoths came on the scene 5.1 million years ago arising out of Africa.
The evidence at BBL now shows that mammoths and mastodons both roamed together – possibly through intercontinental migration – and were both eating the same vegetation, even with the difference in the shape of their molars.
The original model of the changing landscape botanically, and in terms of the animals’ diet was completely wrong, and was a big shock to Tankersley.
Tankersley’s evidence also revealed significant periods of radical shifts in environmental temperature since the last glacial maximum more than 25,000 years ago, which caused an increase in the deposit of sediment that was greater than the system was able to support. And those radical shifts from cold and dry to warm and moist significantly altered the landscape and the vegetation and plant life.
“To determine what animals roamed the area and how they survived, we looked at the stable carbon and nitrogen isotope chemistry of both the animals and plants that were in the sediment for the past 25,000 years,” says Tankersley. “Since we are what we eat, we discovered that the mammoths, mastodons and bison were not eating the plants we originally thought. As it turns out, they were eating more C3 vegetation, which is tree leaves and weedy vegetation more like we see outside today.”
After incidents like cataclysmic cosmic events caused temperatures to drop and darkened the air with clouds of poisonous gas, the resulting climate change presented challenges for most plant and animal species to continue living. According to Tankersley, life at that time became a true test of survival skills for all living things, so those that could move or adapt to their new surroundings survived – many by evolving into a smaller, lighter and faster species.
Larger animal species that could not move fast or for long distances starved or were imprisoned in the muddy landscape and became easy prey for hungry predators.
“My students discovered all of this,” says Tankersley. “My job in this ‘Surviving Climate Change’ project was to give them the resources and tools and teach them the scientific techniques we use, but then let them be the discoverers, which is exactly what happened.”
SURVIVAL OF THE MOST FLEXIBLE
At BBL, Tankersley focused on which species survived and which ones went extinct. They determined that during times when food sources were declining, animals had to move to more fruitful environments or learn to do with less food, which ultimately led to the evolution of today’s surviving species.
Looking closer at those survival patterns, Tankersley found that species like caribou could no longer make a living in this area, but they could up north. And although bison are still around, they are a lot smaller than they were thousands of years ago.
The moral to this story, explains Tankersley, is that many species evolved into smaller animals over time as their food sources started to decline. While some larger species simply died off from a lack of necessary resources, bison and deer were two mammals that were able to survive by evolving with a smaller body mass and shorter stature.
“If you look at a species and you have an environmental downturn or major change in the amount of solar radiation, the amount of water moisture and the amount of frost-free days, can all plants respond to that equally? Of course not,” says Tankersley. “As individuals, we all have different tolerance levels for change. So in the case of the caribou, when the climate changed rapidly and profoundly it could no longer make a living at BBL. But it could continue to make a living up north where it had the environment for survival.
“Species get bigger when there is a lot of food available and smaller when there is not. So the bison downsized, but the mammoth and mastodon did not. They could neither move nor downsize quickly enough so they simply died off.”
BEAVERS THE SIZE OF BLACK BEARS – OH MY! Tankersley’s team also discovered different species within a species. For example, while there were small beavers then just like there are now, from 25,000 until 10,000 years ago there were also large beavers the size of black bears.
“The larger extinct beaver lost its battle to survive because it was dependent on a certain environment that was dying off, but the modern beaver could make its own environment and consequently survived,” says Tankersley. “So there is a lesson there. Animals had to adapt, downsize or go extinct.”
Last year Tankersley and his students excavated over 17,000 specimens that are now housed at the Cincinnati Museum Center. While digging up animal bones they found evidence of humans who had butchered these animals.
ENTER THE HUMANS
To effectively date the plant and animal specimens, Tankersley’s students examined radiocarbon and optically stimulated luminescence (OSL) ages. Dating much of the material to 5,000 years ago using OSL procedures, Tankersley was shocked to find the evidence for human activity and a new anthropological time period now called the Anthropocene – when humans became the most powerful, natural force.
“So much of science is serendipitous,” claims Tankersley. “What the students discovered serendipitously, by dating these deposits, was that humans came in and broke the sod.
Deeper into the sediment, Tankersley found that humans had dug pits into the ground to process animal skins to wear as clothing. Based on ethnographic French literature, the Native Americans had put piles of rocks inside the pits along with hickory nuts, then they used hot rocks to boil the water. The oily, greasy meat of the hickory nut would float to the top and the non-edible remains like the shell and hull would sink to the bottom.
“They would skim it off and drink the water, as it was very nutritious,” says Tankersley. “When they were finished, they would grab the softened deerskin and leave the rocks and nutshells behind, which is what we found.”
To protect their hickory-nut trees from squirrels and other animals, Tankersley found evidence for human deforestation, where large areas of trees were cleared to create separate hickory-tree orchards, protecting them from animal invasion. That deforestation and degradation resulted in substantial erosion of the uplands, which caused the overbank and backwater flooding of the Ohio Valley area.
The changing vegetation, as a result of this deforestation also contributed to the demise, adaptation or evolution of several species.
Furthermore, Tankersley and his students uncovered evidence for animals being hunted by humans during this same period. Looking closely at the hash marks in animal bones, there was strong clues that humans had greatly contributed to the extinction of some of the species in BBL like the larger bison.
Consequently, through deforestation and arboriculture behavior, and the hunting and extinction of many species of animals, Tankersley found clear evidence that humans indeed contributed to the changing landscape even as far back as 5,000 years ago.
“It’s hard to believe, but there is no volcano, no earthquake or tsunami that is moving more sediment than we are,” says Tankersley. “Humans are the most powerful force on the planet right now.”
To help prevent an underlying assumption of landscape change or stability where it does not exist, Tankersley’s team efforts show that both natural and human anthropogenic erosional processes were taking place 5,000 years ago. This activity is directly responsible for the primary and secondary deposits of animal, plant and human artifact remains at Big Bone Lick, Kentucky.
The planet Mercury reflects only one-third of the amount of light that the moon reflects. At last, scientists may know why. (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)
A Mercury-like body smashed into a young Earth and gave our planet’s core the radioactive elements necessary to generate a magnetic field, two Oxford geochemists say.
Without that magnetic field, there would be no shield to protect us from the onslaught of radiation constantly bombarding Earth from space, making the existence of life as we know it impossible, scientists say.
The study, published in the journal Nature, offers insight into how Earth’s magnetic field – and, perhaps, the moon – came to be.
Our planet is thought to have formed from small rocky bodies like the ones in the asteroid belt today, study co-author Bernard Wood, a geochemist at the University of Oxford, said in an interview. It’s a theory that fits quite well with what’s been studied on Earth, though it’s not a perfect fit, he said.
“That sort of roughly works, but there are all kinds of little questions that don’t quite work,” Wood said, “and one of them is, what is the energy source that drives the Earth’s magnetic field?”
Here’s the problem. To drive Earth’s magnetic field, you need radioactive elements like potassium, thorium or uranium – elements that give off heat as they decay – to also be in the planet’s churning iron core. Those elements love getting together with oxygen, making oxides – but oxides are really light and would float toward the planet’s surface; they wouldn’t be heavy enough to stay in the core. These elements also hate getting together with iron.
“They love oxygen so much and they hate being metals so much that they shouldn’t go into the Earth’s core,” Wood said.
So there’s no good way, under current models, to keep enough radioactive material in Earth’s center to power our vital magnetic field – a conundrum for planetary scientists.
But Wood and Oxford colleague Anke Wohlers realized that if you had a source of reduced sulfides – sulfur compounds that don’t have oxygen – into the iron core, it would make it easier for these iron-hating radioactive elements to hang with the metal.
“We said OK, we’ll re-create those conditions in our high-pressure apparatus and we’ll look and see whether the radioactive elements uranium and thorium, and also some of the so-called rare earth elements, would partition into the sulfur-rich metal under those conditions,” Wood said. “And we found much to our pleasure and surprise that uranium very strongly partitions into sulfur-rich metal under those very oxygen-poor or -reducing conditions.”
It would also explain why the ratio of two such rare-earth elements, samarium to neodymium, is higher in the crust and mantle than it is in the rest of the solar system, he added. Because neodymium mixes with iron sulfides more easily than samarium, it more easily sinks into the core, leaving relatively more samarium behind in Earth’s upper layers.
But how did Earth, which is full of oxides, get all these reduced sulfides in the first place? It probably came from a body that looked a lot like Mercury, which is rich in sulfur and very poor in oxygen.
The scientists think that, early in the planet’s history, Earth gobbled up a Mercury-like body, and those sulfides allowed the uranium to stay in the core, which is what has allowed it to power our magnetic field for an estimated 3.5 billion years.
“Before Wohlers and Wood’s experiments, there was only limited (and controversial) experimental evidence that either uranium or potassium can be incorporated in iron metal at the high temperatures and pressures of core formation,” Richard Carlson of the Carnegie Institution for Science in Washington, who was not involved in the study, wrote in a commentary on the paper.
However, he added, “a more stringent test” of whether uranium made it into the core in this way would be to study the radio of different isotopes of neodymium in Earth’s crust and mantle.
This body, by the way, was Mercury-like in composition, but it was not Mercury-sized, Wood said. It was probably closer to the mass of Mars.
That’s interesting, because scientists think that a Mars-sized body’s dramatic collision with Earth is what gave birth to the moon. It’s possible that this Mercury-like body was in fact that selfsame Earth-shattering missile.
“We think that that is quite conceivable,” Wood said. “It’s kind of exciting to think that this reduced body could actually be the thing which caused the moon.”
Reference:
A Mercury-like component of early Earth yields uranium in the core and high mantle 142Nd, Nature 520, 337–340 (16 April 2015) DOI: 10.1038/nature14350
Note : The above story is based on materials provided by Los Angeles Times, Distributed by Tribune Content Agency, LLC.
This is the Kapp Starostin Formation, Festningen section, Spitsbergen. The uppermost of the 3 yellow limestone beds records the Middle Permian mass extinction. This is the first high latitude record of this crisis, which is now seen to be of global extent. The photo, from Isfjorden, Spitsbergen, was taken by Dierk Blomeier. Credit : Dierk Blomeier. For David P.G. Bond and colleagues, GSA Bulletin, 2015.
Since the Cambrian Explosion, ecosystems have suffered repeated mass extinctions, with the “Big 5” crises being the most prominent. Twenty years ago, a sixth major extinction was recognized in the Middle Permian (262 million years ago) of China, when paleontologists teased apart losses from the “Great Dying” at the end of the period. Until now, this Capitanian extinction was known only from equatorial settings, and its status as a global crisis was controversial.
David P.G. Bond and colleagues provide the first evidence for severe Middle Permian losses amongst brachiopods in northern paleolatitudes (Spitsbergen). Their study shows that the Boreal crisis coincided with an intensification of marine oxygen depletion, implicating this killer in the extinction scenario.
The widespread loss of carbonates across the Boreal Realm also suggests a role for acidification. The new data cements the Middle Permian crisis’s status as a true “mass extinction.” Thus the “Big 5” extinctions should now be considered the “Big 6.”
Reference:
David P.G. Bond et al., University of Hull, Hull, UK. Published online ahead of print on 14 Apr. 2015; DOI: 10.1130/B31216.1
Pacific Northwest National Laboratory’s new geothermal stimulation fluid could make geothermal power production more environmentally friendly and less costly where conventional geothermal doesn’t work. The nontoxic fluid is designed to be used in enhanced geothermal systems, where fluids are injected into drilled wells that lead to underground geothermal reservoirs. The fluid expands when exposed to carbon dioxide underground, which creates tiny, but deep cracks in otherwise impermeable rock. Credit: Pacific Northwest National Laboratory
More American homes could be powered by the earth’s natural underground heat with a new, nontoxic and potentially recyclable liquid that is expected to use half as much water as other fluids used to tap into otherwise unreachable geothermal hot spots.
The fluid might be a boon to a new approach to geothermal power called enhanced geothermal systems. These systems pump fluids underground, a step that’s called “reservoir stimulation,” to enable power production where conventional geothermal doesn’t work.
The new reservoir stimulation fluid features an environmentally friendly polymer that greatly expands the fluid’s volume, which creates tiny cracks in deep underground rocks to improve power production. This fluid could also substantially reduce the water footprint and cost of enhanced geothermal systems. A paper describing the fluid has been published by the Royal Society of Chemistry in an advance online version of the journal Green Chemistry.
“Our new fluid can make enhanced geothermal power production more viable,” said lead fluid developer Carlos Fernandez, a chemist at the Department of Energy’s Pacific Northwest National Laboratory. “And, though we initially designed the fluid for geothermal energy, it could also make unconventional oil and gas recovery more environmentally friendly.”
Geothermal power is generated by tapping the heat that exists under the Earth’s surface to extract steam and turn power plant turbines. Conventional geothermal power plants rely on the natural presence of three things: underground water, porous rock and heat. Existing U.S. geothermal power plants generate up to 3.4 gigawatts of energy, making up about 0.4 percent of the nation’s energy supply.
Enhanced geothermal power can be generated at sites where heat exists, but isn’t easily accessible because of impermeable rock or insufficient water. A 2006 report led by the Massachusetts Institute of Technology estimates enhanced geothermal systems could boost the nation’s geothermal energy output 30-fold to more than 100 gigawatts, or enough to power 100 million typical American homes.
Interested in this potential, DOE has funded five enhanced geothermal system demonstration projects across the country. At one demonstration project in Nevada, enhanced geothermal methods increased a conventional geothermal plant’s productivity by 38 percent. But the use of enhanced geothermal systems has been limited due to technical challenges and concerns over their cost and heavy use of water.
Creating enhanced geothermal systems requires injecting millions of gallons of water – a valuable resource in the arid American West, where enhanced geothermal has the most potential. That water is sometimes mixed with a very small amount of chemicals to help the fluid better create and spread tiny cracks underground, which ultimately extends the life of a geothermal power plant.
Some geothermal reservoir stimulation fluids are similar to oil and gas hydraulic fracturing fluids in that a small percentage of their volume can include proprietary chemicals, according to a 2009 paper in Geothermics and other sources. These chemicals can be toxic if ingested, leading geothermal developers to retrieve and treat used fluids. This protects aquifers, but increases the cost of power generation as well. Environmental reviews must be conducted to receive permits for enhanced geothermal injections.
A better solution
PNNL’s fluid is a solution of water and 1 percent polyallylamine, a chemical made of a long carbon chain with nitrogen attachments that’s similar to well-understood polymers used in medicine. The fluid is pumped into a well drilled at a geothermal hot spot. Soon after, workers also inject pressurized carbon dioxide, which could come from carbon captured at fossil fuel power plants.
Within 20 seconds, the polyallylamine and carbon dioxide link together to form a hydrogel that expands the fluid up to 2.5 times its original volume. The swelling gel pushes against the rocks, causing existing cracks to expand while also creating new ones. The expansion is expected to cut in half the amount of water and time needed to open up an enhanced geothermal reservoir, which shrinks the cost of power generation.
Passing the test
To test the fluid’s performance, geophysicist and co-author Alain Bonneville led the development of an experimental set up. Five cylindrical samples of rocks, about the size of C batteries, taken near a working enhanced geothermal power plant in California, were placed inside a high-pressure, high-temperature test cell created by the PNNL team. Small amounts of the fluid and liquid carbon dioxide were injected into the test cell. Pressure and temperature were gradually adjusted to match the conditions of underground geothermal reservoirs.
The researchers found their fluid consistently created small, but effective cracks in rock samples. Some of the new fractures were too small to be seen with a high-resolution imaging method called X-ray microtomography. But when they watched fluids such as water or carbon dioxide being injected, the team saw liquids moving through the previously impermeable rock samples. Moving liquids did not pass through rock samples that were injected with plain water or the common hydraulic fracturing chemicals sodium dodecyl sulfate and xanthan gum. The team reasoned larger-scale tests might produce bigger cracks.
Reduce, reuse & recycle
Two other benefits are the fluid’s potential to be recycled and cut costs. The fluid could be recycled by reducing or stopping the fluids that are pumped underground, or by injecting an acid. Modeling shows either would cause the hydrogel to disassemble into its original components: the water-polyallylamine solution and carbon dioxide. A pump would move the separated fluids to the surface, where they would be retrieved and used again. The fluid’s recyclability hasn’t been tested in the lab yet, however.
The operational cost of enhanced geothermal systems could also be reduced with the new fluid. With less liquid to pump underground, there will be less water to purchase, capture and treat, which lowers project costs. However, a detailed analysis is needed to precisely quantify by how much the fluid could lower enhanced geothermal’s price tag.
Additional studies are needed to further evaluate the fluid’s performance for enhanced geothermal systems. Fernandez and his team are planning lab studies to examine the fluid’s recyclability and its ability to fracture larger pieces of rock. Their ultimate goal is to conduct a controlled field test.
The Geothermal Technologies Office within the Department of Energy’s Office of Energy Efficiency and Renewable Energy funded this research. This study used X-ray computed tomography and magic angle spinning nuclear magnetic resonance instruments at EMSL, the Environmental Molecular Sciences Laboratory DOE user facility at PNNL.
The team also recently started a PNNL-funded study to examine a similar fluid for unconventional oil and gas recovery. The oil and gas extraction fluid being considered would use a different polyamine that is related to the chemical used in the geothermal extraction fluid. Both fluids are stable and can withstand extreme temperatures, pressures and acidity levels. Many of the fluids used for oil and gas recovery degrade, making them less effective over time. That characteristic, combined with the fluid’s decreased water use, its nontoxic nature and its potential to be recycled, makes the PNNL fluid a candidate for oil and gas extraction.
Video
Reference:
HB Jung, KC Carroll, S Kabilan, DJ Heldebrant, D Hoyt, L Zhong, T Varga, S Stephens, L Adams, A Bonneville, A Kuprat & CA Fernandez, “Stimuli-responsive/rheoreversible hydraulic fracturing fluids as a greener alternative to support geothermal and fossil energy production,” Green Chemistry Advance Online, March 25, 2015, DOI: 10.1039/C4GC01917B
Research reveals fossil record may have been impacted by the appetite of Osedax. Credit: Image copyright Nicholas Higgs, courtesy of University of Plymouth
A species of bone-eating worm that was believed to have evolved in conjunction with whales has been dated back to prehistoric times when it fed on the carcasses of giant marine reptiles.
Scientists at Plymouth University found that Osedax — popularised as the ‘zombie worm’ — originated at least 100 million years ago, and subsisted on the bones of prehistoric reptiles such as plesiosaurs and sea turtles.
Reporting in the Royal Society journal Biology Letters this month, the research team at Plymouth reveal how they found tell-tale traces of Osedax on plesiosaur fossils held in the Sedgwick Museum at the University of Cambridge.
Dr Nicholas Higgs, a Research Fellow in the Marine Institute, said the discovery was important for both understanding the genesis of the species and its implications for fossil records. “The exploration of the deep sea in the past decades has led to the discovery of hundreds of new species with unique adaptations to survive in extreme environments, giving rise to important questions on their origin and evolution through geological time.” said Nicholas. “The unusual adaptations and striking beauty of Osedax worms encapsulate the alien nature of deep-sea life in public imagination.
“And our discovery shows that these bone-eating worms did not co-evolve with whales, but that they also devoured the skeletons of large marine reptiles that dominated oceans in the age of the dinosaurs. Osedax, therefore, prevented many skeletons from becoming fossilised, which might hamper our knowledge of these extinct leviathans.”
The finger-length Osedax is found in oceans across the globe at depths of up to 4,000m, and it belongs to the Siboglinidae family of worms, which, as adults, lack a mouth and digestive system. Instead, they penetrate bone using root-like tendrils through which they absorb bone collagen and lipids that are then converted into energy by bacteria inside the worm.
Typically they consume whale bones, prompting many scientists to believe that they co-evolved 45 million years ago, branching out from their cousins that used chemosysnthesis to obtain food.
But Nicholas, and research lead Dr Silvia Danise, of Plymouth’s School of Geography, Earth and Environmental Sciences, studied fossil fragments taken from a plesiosaur unearthed in Cambridge, and a sea turtle found in Burham, Kent.
Using a computed tomography scanner at the Natural History Museum — essentially a three-dimensional X-ray — they were able to create a computer model of the bones, and found tell-tale bore holes and cavities consistent with the burrowing technique of Osedax.
Dr Danise said: “The increasing evidence for Osedax throughout the oceans past and present, combined with their propensity to rapidly consume a wide range of vertebrate skeletons, suggests that Osedax may have had a significant negative effect on the preservation of marine vertebrate skeletons in the fossil record.
“By destroying vertebrate skeletons before they could be buried, Osedax may be responsible for the loss of data on marine vertebrate anatomy and carcass-fall communities on a global scale. The true extent of this ‘Osedax effect’, previously hypothesized only for the Cenozoic, now needs to be assessed for Cretaceous marine vertebrates.”
Reference:
S. Danise, N. D. Higgs. Bone-eating Osedax worms lived on Mesozoic marine reptile deadfalls. Biology Letters, 2015; 11 (4): 20150072 DOI: 10.1098/rsbl.2015.0072
Note: The above story is based on materials provided by University of Plymouth. The original article was written by Andrew Merrington.
A new analysis of the chemical make-up of meteorites has helped scientists work out when the Earth formed its layers.
The research by an international team of scientists confirmed the Earth’s first crust had formed around 4.5 billion years ago.
The team measured the amount of the rare elements hafnium and lutetium in the mineral zircon in a meteorite that originated early in the solar system.
“Meteorites that contain zircons are rare. We had been looking for an old meteorite with large zircons, about 50 microns long, that contained enough hafnium for precise analysis,” said Dr Yuri Amelin, from The Australian National University (ANU) Research School of Earth Sciences.
“By chance we found one for sale from a dealer. It was just what we wanted. We believe it originated from the asteroid Vesta, following a large impact that sent rock fragments on a course to Earth.”
The heat and pressure in the Earth’s interior mixes the chemical composition of its layers over billions of years, as denser rocks sink and less dense minerals rise towards the surface, a process known as differentiation.
Determining how and when the layers formed relies on knowing the composition of the original material that formed into the Earth, before differentiation, said Dr Amelin.
“Meteorites are remnants of the original pool of material that formed all the planets,” he said.
“But they have not had planetary-scale forces changing their composition throughout their five billion years orbiting the sun.”
The team accurately measured the ratio of the isotopes hafnium-176 and hafnium-177 in the meteorite, to give a starting point for the Earth’s composition.
The team were then able to compare the results with the oldest rocks on Earth, and found that the chemical composition had already been altered, proving that a crust had already formed on the surface of the Earth around 4.5 billion years ago.
Reference:
Tsuyoshi Iizuka, Takao Yamaguchi, Yuki Hibiya, and Yuri Amelin. Meteorite zircon constraints on the bulk Lu−Hf isotope composition and early differentiation of the Earth. PNAS, April 13, 2015 DOI: 10.1073/pnas.1501658112
The researchers believe that Gale Crater was a large lake between 3.5 and 2.7 billion years ago. Mount Sharp, which is now an approximately five kilometer tall mountain in the middle of the crater, was probably formed by deposits from the crater and the surrounding area. Credit: NASA/JPL/Caltech/ESA/DLR/MSSS
Researchers have long known that there was water in the form of ice on Mars. Now, new research from NASA’s Mars rover Curiosity shows that it is possible that there is liquid water close to the surface of Mars. The explanation is that the substance perchlorate has been found in the soil, which lowers the freezing point so the water does not freeze into ice, but is liquid and present in very salty salt water — a brine. The results are published in the scientific journal Nature.
“We have discovered the substance calcium perchlorate in the soil and, under the right conditions, it absorbs water vapour from the atmosphere. Our measurements from the Curiosity rover’s weather monitoring station show that these conditions exist at night and just after sunrise in the winter. Based on measurements of humidity and the temperature at a height of 1.6 meters and at the surface of the planet, we can estimate the amount of water that is absorbed. When night falls, some of the water vapour in the atmosphere condenses on the planet surface as frost, but calcium perchlorate is very absorbent and it forms a brine with the water, so the freezing point is lowered and the frost can turn into a liquid. The soil is porous, so what we are seeing is that the water seeps down through the soil. Over time, other salts may also dissolve in the soil and now that they are liquid, they can move and precipitate elsewhere under the surface,” explains Morten Bo Madsen, associate professor and head of the Mars Group at the Niels Bohr Institute at the University of Copenhagen.
Riverbed and enormous lake
Observations by the Mars probe’s stereo camera have previously shown areas characteristic of old riverbed with rounded pepples that clearly show that a long time ago there was flowing, running water with a depth of up to one meter. Now the new close-up images taken by the rover all the way en route to Mount Sharp show that there are expanses of sedimentary deposits, lying as ‘plates’ one above the other and leaning a bit toward Mount Sharp.
“These kind of deposits are formed when large amounts of water flow down the slopes of the crater and these streams of water meet the stagnant water in the form of a lake. When the stream meets the surface, the solid material carried by the stream falls down and is deposited in the lake just at the lakeshore. Gradually, a slightly inclined slope is built up just below the surface of the water and traces of such slanting deposits were found during the entire trip to Mount Sharp. Very fine-grained sediments, which slowly fell down through the water, were deposited right at the very bottom of the crater lake. The sediment plates on the bottom are level, so everything indicates that the entire Gale Crater may have been a large lake,” explains Morten Bo Madsen.
He explains that about 4.5 billion years ago, Mars had 6½ times as much water as it does now and a thicker atmosphere. But most of this water has disappeared out into space and the reason is that Mars no longer has global magnetic fields, which we have on Earth.
Currents of liquid iron in the Earth’s interior generate the magnetic fields and they act as a shield that protects us from cosmic radiation. The magnetic field protects the Earth’s atmosphere against degradation from energy rich particles from the Sun. But Mars no longer has a global magnetic field and this means that the atmosphere is not protected from radiation from the Sun, so the solar particles (protons) simply ‘shoot’ the atmosphere out into space little by little.
Even though liquid water has now been found, it is not likely that life will be found on Mars — it is too dry, too cold and the cosmic radiation is so powerful that it penetrates at least one meter into the surface and kills all life — at least life as we know it on Earth.
An international team, including researchers at the University of Liverpool, have shown that south east Iceland is underlain by continental crust.
The team found that the accepted theory, that Iceland consists only of very thick oceanic crust, is incorrect. Maps of crustal thickness produced from satellite gravity data, together with geochemical, plate tectonic reconstruction and mantle plume track analysis (an upwelling of abnormally hot rock), were used to show that south east Iceland is underlain by continental crust which extends offshore to the east.
Professor Nick Kusznir, from the University’s School of Environmental Sciences, who produced the satellite data, said: “The established theory is that geological features such as Iceland, known as oceanic plateaux, are generated by the interaction of ocean-ridge sea-floor spreading with a hot mantle upwelling.
“Our results suggest that there is another critical ingredient which is the presence of fragments of continental crust. This discovery has important implications for how mantle plumes interact with plate tectonics.”
Crustal thickness mapping shows thick crust under south east Iceland of up to 30 km, which is more ‘typical’ of continental crust in comparison to much thinner crust in the surrounding ocean basins and under the rest of Iceland.
The thick crust of south east Iceland extends eastwards offshore and is interpreted as being a sliver of continental crust originally part of, but now separated from, the Jan Mayan micro-continent to the north from which it has rifted during the formation of the north east Atlantic in the last 55 million years.
Professor Kusznir added: “Global crustal thickness mapping, using gravity inversion, suggests that tectonic features, such as Iceland, formed by the interaction of mantle plumes, sea-floor spreading and micro-continent fragments, are quite common.
“Other examples include Mauritius in the Indian Ocean; the Rio Grande High in the south Atlantic; and the Canary Islands in the Central Atlantic.
“Not only is this discovery important for the science of geo-dynamics, our findings also has important implications for natural resources in these regions. Continental crust has a very different composition and history to oceanic crust and is much richer in natural resources.”
Oil and gas exploration
Crustal thickness mapping using the satellite gravity inversion methodology was developed by Professor Kusznir and has been used for locating the transition between continental and oceanic crust and micro-continents for the United Nations Convention on the Law of the Sea (UNCLOS) territorial claims and is used extensively by the hydrocarbon industry in deep water oil and gas exploration.
Reference:
Trond H. Torsvik, Hans E. F. Amundsen, Reidar G. Trønnes, Pavel V. Doubrovine, Carmen Gaina, Nick J. Kusznir, Bernhard Steinberger, Fernando Corfu, Lewis D. Ashwal, William L. Griffin, Stephanie C. Werner, Bjørn Jamtveit. Continental crust beneath southeast Iceland. Proceedings of the National Academy of Sciences, 2015; 201423099 DOI: 10.1073/pnas.1423099112
Ultra-slow spreading ocean ridges were discovered in the Arctic in 2003 by scientists at Woods Hole Ocenographic Institution. They found that for large regions the sea floor splits apart by pulling up solid rock from deep within the earth. These rocks, known as peridotites (after the gemstone peridot) come from the deep layer of the earth known as the mantle. Credit: Dr. Henry J.B. Dick, WHOI/nsf.gov
Methane, a highly effective greenhouse gas, is usually produced by decomposition of organic material, a complex process involving bacteria and microbes.
But there is another type of methane that can appear under specific circumstances: Abiotic methane is formed by chemical reactions in the oceanic crust beneath the seafloor.
New findings show that deep water gas hydrates, icy substances in the sediments that trap huge amounts of the methane, can be a reservoir for abiotic methane. One such reservoir was recently discovered on the ultraslow spreading Knipovich ridge, in the deep Fram Strait of the Arctic Ocean. The study suggests that abiotic methane could supply vast systems of methane hydrate throughout the Arctic.
The study was conducted by scientists at Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT The Arctic Univeristy of Norway. The results were recently published in Geology online and will be featured in the journal´s May issue.
“Current geophysical data from the flank of this ultraslow spreading ridge shows that the Arctic environment is ideal for this type of methane production. ” says Joel Johnson associate professor at the University of New Hampshire (USA), lead author, and visiting scholar at CAGE.
This is a previously undescribed process of hydrate formation; most of the known methane hydrates in the world are fueled by methane from the decomposition of organic matter.
“It is estimated that up to 15 000 gigatonnes of carbon may be stored in the form of hydrates in the ocean floor, but this estimate is not accounting for abiotic methane. So there is probably much more.” says co-author and CAGE director Jürgen Mienert.
Life on Mars?
NASA has recently discovered traces of methane on the surface of Mars, which led to speculations that there once was life on our neighboring planet. But an abiotic origin cannot be ruled out yet.
On Earth it occurs through a process called serpentinization.
“Serpentinization occurs when seawater reacts with hot mantle rocks exhumed along large faults within the seafloor. These only form in slow to ultraslow spreading seafloor crust. The optimal temperature range for serpentinization of ocean crust is 200 – 350 degrees Celsius.” says Johnson.
Methane produced by serpentinization can escape through cracks and faults, and end up at the ocean floor. But in the Knipovich Ridge it is trapped as gas hydrate in the sediments. How is it possible that relatively warm gas becomes this icy substance?
“In other known settings the abiotic methane escapes into the ocean, where it potentially influences ocean chemistry. But if the pressure is high enough, and the subseafloor temperature is cold enough, the gas gets trapped in a hydrate structure below the sea floor. This is the case at Knipovich Ridge, where sediments cap the ocean crust at water depths up to 2000 meters. ” says Johnson.
Stable for 2 million years
Another peculiarity about this ridge is that because it is so slowly spreading, it is covered in sediments deposited by fast moving ocean currents of the Fram Strait. The sediments contain the hydrate reservoir, and have been doing so for about 2 million years.
“This is a relatively young ocean ridge, close to the continental margin,. It is covered with sediments that were deposited in a geologically speaking short time period –during the last two to three million years. These sediments help keep the methane trapped in the sea floor.” says Stefan Bünz of CAGE, also a co-author on the paper.
Bünz says that there are many places in the Arctic Ocean with a similar tectonic setting as the Knipovich ridge, suggesting that similar gas hydrate systems may be trapping this type of methane along the more than 1000 km long Gakkel Ridge of the central Arctic Ocean.
The Geology paper states that such active tectonic environments may not only provide an additional source of methane for gas hydrate, but serve as a newly identified and stable tectonic setting for the long-term storage of methane carbon in deep-marine sediments.
Need to drill
The reservoir was identified using CAGE’s high resolution 3D seismic technology aboard ice going research ressel Helmer Hanssen. Now the authors of the paper wish to sample the hydrates 140 metres below the ocean floor, and decipher their gas composition.
Knipovich Ridge is the most promising location on the planet where such samples can be taken, and one of the two locations where sampling of gas hydrates from abiotic methane is possible.
” We think that the processes that created this abiotic methane have been very active in the past. It is however not a very active site for methane release today. But hydrates under the sediment, enable us to take a closer look at the creation of abiotic methane through the gas composition of previously formed hydrate.” says Jürgen Mienert who is exploring possibilities for a drilling campaign along ultra-slow spreading Arctic ridges in the future.
Reference:
“Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates.” DOI: 10.1130/G36440.1
The fossil remains of two oviraptorosaurs , nicknamed ‘Romeo and Juliet’ , were reported in 2001. Credit: Amanda Kelly
Researchers think they have come up with a way to tell fossils of male dinosaurs from those of females — at least for some small feathered species. The key differences between the sexes lie in bones near the base of the tail, the scientists reported on 31 March in Scientific Reports.
The team examined a pair of fossils unearthed in Mongolia in the mid-1990s and first described in 20012. Because the turkey-sized oviraptorosaurs (“egg-thief lizards”) were found mere centimetres from each other in a 75-million-year-old rock layer, some scientists have nicknamed the pair ‘Romeo and Juliet’.
The joints in the creatures’ vertebrae were fused, so researchers think that the dinosaurs had stopped growing — meaning they were adults, says Scott Persons, a vertebrate palaeontologist at the University of Alberta in Edmonton, Canada, and a co-author of the study.
But determining whether the pair were indeed male and female was tricky, because, as with most fossils, no trace of soft tissue remains: only the bones are preserved. One fossil is a complete skeleton, whereas the other is missing the middle and end of its tail. But that was enough to reveal distinct differences in the length and shape of blade-like bones called chevrons, which jut down from the vertebrae near the base of the tail and provide attachments for muscles and tendons.
A number of chevrons in one of the fossils were longer and had broader tips than those in the other specimen. The differences do not seem to be due to injury or disease, says Persons. Nor do they seem to be the result of changes in the bones during fossilization.
Instead, the researchers suggest that the variations are a sign of sex differences. The bones might be shorter in females to ease the process of laying eggs. In males, a set of longer, broad-tipped chevrons could have offered a better anchor for a penis-retracting muscle that the creatures are presumed to have had.
But the most tantalizing explanation might be that males needed larger chevrons to anchor the muscles that controlled their flexible, feather-tipped tails. The researchers suspect that male oviraptorosaurs shook their tail feathers in intricate displays to woo potential mates, akin the the behaviour of modern-day peacocks.’
Two by two
The shape and size of chevron tail bones varied between the fossils that researchers tentatively identified as female (top) and male.
Thomas Holtz, a vertebrate palaeontologist at the University of Maryland in College Park, says that the theory is intriguing, but not yet totally convincing. Because the study’s authors compared only two oviraptorosaur specimens, they cannot rule out the possibility that the differences in chevron shape are merely variations on a spectrum, rather than signs of sexual dimorphism.
Analyses of other oviraptorosaur fossils should reveal whether chevrons clump into two shape groups — supporting the idea of a sex split — or come in a range of forms, says Holtz.
Confirmation of the findings could allow researchers to use chevron comparisons to determine sex in other small dinosaurs that might have used feathers for display. But Holtz says that the method would not be widely applicable to multi-tonne dinosaurs such as Tyrannosaurus rex and Triceratops.
If proved, the method would join one other technique to ascertain whether a dinosaur was male or female. In 2005, researchers noted that some T. rex fossils contain bone tissue similar to the medullary bone of modern female birds, for which it provides a short-term reservoir of calcium to produce eggshells. This method works for other large dinosaurs, but it is not foolproof because the medullary bone is only found in female specimens that are sexually mature and ready to lay eggs.
Note : The above story is based on materials provided by Nature. The original article was written by Sid Perkins.
Trilobites survived for roughly 270 million years before disappearing at the end of the Permian period. Credit: Florilegius/SSPL/Getty
Earth’s greatest extinction event happened in a one-two punch 252 million years ago. Research now suggests that the second pulse of extinction, during which nearly all marine species vanished from the planet, happened in the wake of huge volcanic eruptions that spewed out carbon dioxide and made the oceans more acidic.
The work, published in Science1, is the latest to try to pinpoint the causes of the ‘Great Dying’, at the end of the Permian period. The study uses chemical evidence in rocks from that period to calculate how quickly ocean chemistry shifted.
Volcanoes in Siberia belched so much CO2 in such a short period of time that the oceans simply could not absorb it all, says team leader Matthew Clarkson, a geochemist at the University of Otago in Dunedin, New Zealand. Within just 10,000 years, pH levels in at least some of the world’s oceans plummeted.
“There was already enormous pressure on life on the oceans,” Clarkson says. “And suddenly we have what appears to be a rapid volcanic eruption, the final blow that drove the acidification.”
Reflections in the water
Today, oceans are becoming more acidic as a result of the large amounts of CO2 produced by human activities such as the burning of fossil fuels; the average pH has dropped by 0.1 units since the beginning of the Industrial Revolution. The Great Dying might represent a worst-case scenario for the future if CO2 emissions continue to rise, says Clarkson.
Other researchers have proposed all sorts of ideas for what caused the end-Permian extinction, from oxygen-starved oceans to methane-belching microbes. Top contenders have included both the Siberian volcanoes and acidifying oceans, separately or in sequence as the new study describes. In 2010, a study that examined calcium isotopes in ancient rocks found that oceans got more acidic during the end of the Permian period2.
But the latest work measures pH more directly than before, says Clarkson. His team looked at the ratios of boron isotopes in Permian-age rocks from the United Arab Emirates. Boron exists in sea-water in two forms, the relative amounts of which are controlled by how acidic or alkaline the water is. By measuring the levels of each boron isotope, the researchers could directly calculate the pH of the water that once covered the marine rocks.
The team saw little change in acid levels during the first phase of the Permian extinction, which lasted about 50,000 years. But during the second, much faster pulse, pH levels dropped by about 0.7 units over 10,000 years, Clarkson says.
That is probably because the Siberian volcanoes were putting out so much CO2 so quickly, the researchers argue. “It’s such a rapid change, the ocean can’t buffer the CO2 increase,” Clarkson says.
Many questions remain. The team cannot explain definitively what caused the first phase of extinction, which seems to have happened before the volcanoes began to erupt. And the researchers need to confirm whether Permian marine rocks in other parts of the world — not just those in the United Arab Emirates — also show the same sharp ocean acidification during the second extinction pulse.
“We’ve still got quite a lot of work to do,” says Clarkson. “Everyone always wants the smoking gun for these things.”
Andy Ridgwell, an earth systems scientist at the University of Bristol, agrees. “In principle the approach is good,” he says. “But there may be different explanations for what they’re seeing.” The end of the Permian was so geochemically complicated, he says, that untangling the various factors may take some time yet.
An evenly-layered rock on the planet Mars, photographed by the Mast Camera (Mastcam) on NASA’s Curiosity Mars Rover is shown in the NASA handout provided December 9, 2014. Credit: Reuters/NASA/JPL-Caltech/MSSS/Handout via Reuters
Mars has thousands of glaciers buried beneath its dusty surface, enough frozen water to blanket the planet with a 3.6-foot(1.1- meter) thick layer of ice, scientists said on Wednesday.
The glaciers are found in two bands in the mid-southern and mid-northern latitudes. Radar data, collected by Mars-orbiting satellites, combined with computer models of ice flows show the planet has about 5.3 trillion cubic feet (150 billion cubic meters) of water locked in the ice, according to a study published in this week’s issue of the journal Geophysical Research Letter.
“The ice at the mid-latitudes is therefore an important part of Mars’ water reservoir,” Nanna Bjornholt Karlsson, a researcher at the University of Copenhagen’s Neils Bohr Institute, said in a statement.
Scientists have been trying to figure out how Mars transformed from a warm, wet and presumably Earth-like planet early in its history into the cold, dry desert that exists today.
Billions of years ago, Mars, which lacks a protective, global magnetic field, lost much of its atmosphere. Several initiatives are under way to determine how much of the planet’s water was stripped away and how much remains locked in ice in underground reservoirs.
“The atmospheric pressure on Mars is so low that water ice simply evaporates and becomes water vapor,” the institute said in a news release.
Scientists suspect that the glaciers remained intact because they are protected under a thick layer of dust.
In addition to evidence of river beds, streams and hydrated minerals, scientists studying telltale molecules in the Martian atmosphere last month concluded that the planet probably had an ocean more than a mile deep covering almost half of its northern hemisphere. Mars has lost about 87 percent of that water, scientists said.
Currently, the planet’s largest known water reservoir is in the polar caps.
Note : The above story is based on materials provided by Reuters. The original article was Reporting by Irene Klotz; Editing by Jonathan Oatis.
