Fossilized bubbles and cyanobacterial fabric from 1.6 billion-year-old phosphatized microbial mats from Vindhyan Supergroup, central India. Credit: Stefan Bengtson. Credit: Stefan Bengtson
Take a good look at this photo: It shows you 1.6 billion years old fossilized oxygen bubbles, created by tiny microbes in what was once a shallow sea somewhere on young Earth.
The bubbles were photographed and analyzed by researchers studying early life on Earth.
Microbes are of special interest: They were not only the first life forms on Earth. They also turned our planet into a tolerable environment for plants and animals and thus their activity paved the way for life as we know it today.
Some of these early microbes were cyanobacteria that thrived in early shallow waters. They produced oxygen by photosynthesis, and sometimes the oxygen got trapped as bubbles within sticky microbial mats.
Fossilized bubbles and cyanobacterial fabric from 1.6 billion-year-old phosphatized microbial mats from Vindhyan Supergroup, central India. Credit Stefan Bengtson.
The bubbles in the photo were preserved, and today they can be seen as a signature for life.
Ph.D. Therese Sallstedt and colleagues from University of Southern Denmark, Swedish Museum of Natural History and Stockholm University studied fossilized sediments from India, and they found round spheres in the microbial mats.
We interpret them as oxygen bubbles created in cyanobacterial biomats in shallow waters 1,6 billion years ago, said Therese Sallstedt.
Cyanobacteria changed the face of the Earth irreversibly since they were responsible for oxygenating the atmosphere. Simultaneously they constructed sedimentary structures called stromatolites, which still exist on Earth today.
The researchers now think that cyanobacteria played a larger role than previously believed in creating phosphorites in shallow waters, thereby allowing today’s scientists a unique window into ancient ecosystems. They published their findings in the journal Geobiology.
Reference:
T. Sallstedt, S. Bengtson, C. Broman, P. M. Crill, D. E. Canfield. Evidence of oxygenic phototrophy in ancient phosphatic stromatolites from the Paleoproterozoic Vindhyan and Aravalli Supergroups, India. Geobiology, 2018; 16 (2): 139 DOI: 10.1111/gbi.12274
UConn researchers analyzed leaf wax compounds in soils and sediment to reconstruct ancient climates, with a view to better understanding the impact of future climate change. Credit: Getty Images
In Scientific Reports today, UConn researchers report a novel approach to reconstructing ancient climates using analyses of organic compounds in sediments and soils.
This method was developed by former UConn postdoctoral scientist Yvette Eley (now in the Department of Geography, Earth and Environmental Sciences at the University of Birmingham, U.K.) and assistant professor Michael Hren in the UConn Center for Integrative Geosciences. Their new approach makes use of organic compounds found in the waxy, lipid-rich cuticle of plants. These waxy surfaces are critical to plant survival, as they minimize water loss and provide protection from factors such as UV radiation.
The distribution of organic compounds in leaf waxes records information about their growing environment. For instance, when confronted with stressful conditions such as shortage of water, plants can respond by changing the distribution of organic compounds in their leaf wax to combat water loss and improve their chances of survival. Various environmental parameters can therefore result in plants with different distributions of lipids, and these profiles can reveal a lot about the climate those plants were growing in.
Once incorporated into the soil, these organic compounds can be preserved over tens to hundreds of millions of years, offering the potential to quantify changes to regional and global moisture budgets on geologic timescales. The leaf wax lipids are extracted from soils and sediments, which are complex mixtures containing, among many other components, weathered rock, minerals, and decayed plant materials that have accumulated over time.
“Looking at soil today, you’re observing the integrated history of all the plant matter that went into forming that soil over the course of hundreds to thousands of years,” says Hren.
In the past, various methods have been used to give a snapshot of environmental conditions at a point in time, such as analyzing stable isotopes in mammal bones and teeth, or looking at the chemistry of ice cores. However, all methods have limits to the information they can provide.
Eley and Hren investigated the relationship between leaf wax biomarker profiles and modern climate in a series of soils from North and Central America. A clear relationship began to emerge regarding leaf wax lipid distribution profiles and atmospheric moisture, suggesting that it is possible to use the distribution of leaf wax lipids to identify changes in moisture availability in the past.
This new approach represents a significant addition to the paleoclimate scientist’s toolkit, as atmospheric moisture is a parameter that has been challenging to estimate over long periods of Earth history, until now.
With today’s increasing CO2 levels, scientists know there is going to be climate change in the future, but it has not been clear how that may affect regional moisture patterns.
“One of the huge gaps in the past is we didn’t have great quantitative records of moisture,” says Hren. “We’re now managing to get a really nice glimpse of the whole ecosystem and how it’s responding.”
As the researchers focus on the biomarker profiles of soils, they are capturing an integrated chemical signature of a whole ecosystem preserved in ancient soils and sediments.
Hren says they found that the distribution of organic compounds preserved in soils of these ecosystems seems to be strongly related not just to relative humidity, but also to the difference between how much water is in an air mass and how much the air mass can hold, or what is known as the vapor pressure deficit.
Once the researchers established this relationship using modern data, they applied the method to sediments dating back to between 16.5 and 12.4 million years from a well studied area in Spain. They were able to reconcile their lipid-based reconstruction of vapor pressure deficit with existing stable isotope and fossil data for the area, highlighting the utility of this new tool.
Says Eley, “The hope is that we’ll be able to use this approach to tackle key questions about changing moisture availability over time.”
Past, present, and future
Hren and Eley are now applying this method to a range of other ancient terrestrial sediments, to investigate the relationship between changes in past climate and atmospheric moisture. They hope to use insights from these studies, which reconstruct temperature and moisture availability over many millions of years of Earth’s history, to advance understanding of the global changes in environmental conditions anticipated in the coming decades.
“By looking into the past, we’re trying to understand the potential for future change,” says Hren. “This is a powerful tool as we move forward.”
The ultimate hope is that data generated by this new leaf wax biomarker proxy will improve knowledge of past climate responses to CO2, and fill in the gaps – like missing pieces of a puzzle – in spatial reconstructions of paleoclimate during past warm periods of earth history. This in turn will feed into climate predictions of the long-term future of our planet.
This is professor Rais Latypov in front of an example of the stratified chromite layers. Credit: Wits University
South Africa’s history and economy has been built on its rich natural treasures of a number of precious metals, stones and minerals.
The country’s mineral deposits have been created over hundreds of millions of years through processes that are still not completely understood.
One of these processes, that has troubled scientists and geologists for years, is the origin of chromitite layers hosted by layered intrusions — a major source of chromium on our planet. This process has been a mystery for decades, as scientists tried to work out how layers of pure chromite form from magmas that are coming from Earth’s mantle. These are supposed to be rich in a mineral called olivine — not chromite.
“It has been widely believed that magmas sourced from the mantle cannot directly crystallise chromite, as the mantle rocks that are being melted are rich in olivine, and therefore these melts should crystallise olivine, not chromite,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa, whose research team published a paper in Nature Communications in 2018.
“Together with a large group of my colleagues, I have been trying hard for several decades to find a mechanism that can explain the formation of these large chromite deposits in shallow crustal chambers but it turned out that we have been looking in the wrong place.”
To find the answer to these questions, Latypov and his team have been studying layers of chromite in South Africa’s Bushveld Complex, where over 80% of the global resources of platinum-bearing chromite deposits can be found.
They discovered that some basaltic magmas will form chromite after decompression as they rise up from the mantle through the crust towards the Earth’s surface. The reduction in pressure, as the magma rises up from the mantle to the crust, is key to the crystallisation process of the chromite.
“When these magmas arrive into a shallow magma chamber, sitting only a few kilometres below the surface of the Earth, they are already saturated in pure chromite, and, on cooling, can crystallise layers of platinum-bearing massive chromitite.
Chromium is an important industrial element that substantially improves the physical and chemical properties of steels, increasing their strength and making them corrosion-resistant. The platinum that is associated with these rocks is used in catalytic converters within cars to break down toxic exhaust gases into relatively benign species.
These zebra-striped coloured layers of platinum-bearing chromite that are formed through this process can be seen clearly in the ridges at the top of the Bushveld Complex, near Steelpoort in Mpumalanga, which became exposed through erosion over the many millions of years since they formed. Some of these layers can be several meters thick and extend for hundreds of kilometres.
“The Bushveld Complex covers an area of 100s of square kilometres. It stretches from Steelpoort in Mpumalanga in the East, past Pretoria to the Pilanesberg in the West; and from Bethal, Mpumalanga in the South to north of Polokwane in Limpopo. We believe that the Bushveld chamber must have been operating as a flow-through system into which magmas were entering and depositing their chromite, before flowing out of the chamber and erupting as basalts via volcanoes, which have now been eroded away,” says Latypov.
“It seems that the reduction of lithostatic pressure during the transfer of mantle-derived melts towards the surface plays a vital role in the formation of magmas that produce planetary resources, without which modern human society cannot develop in a sustainable manner.”
Further research is being conducted on whether other magmatic deposits around the world, such as vanadium-bearing magnetite in layered intrusions, can also be related to lithostatic pressure reduction.
Reference:
Rais Latypov, Gelu Costin, Sofya Chistyakova, Emma J. Hunt, Ria Mukherjee, Tony Naldrett. Platinum-bearing chromite layers are caused by pressure reduction during magma ascent. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-017-02773-w
Figure 2. Transmitted-light, cross-polarized-light, and scanning electron microscopy (SEM) image of starch-bearing Lagenicula-type megaspore from the Baode section, north China. AL Details of the starch grain in D (rectangle) in transmitted light. Note the hilum (small depression) in center, and Y-shaped fissures. B: Another detail of the same grain under cross-polarized light. Note the Maltese-cross extinction in the center. C: Detail of compound starch grains under cross-polarized light. D: SEM image showing a complete starch-bearing Lagenicula-type megaspore. E: Detail of D, showing starch grains on the gula surface. Black arrow indicates the hilum appearing as a small depression. Credit: Liu et al. and Geology
Everyone loves a nice plate of pasta. After all, starch is the ultimate energy food. Now, we have proof that carbo-loading has been a thing for at least 280 million years.
A team of Chinese and German scientists has discovered the oldest unequivocal fossilized starch ever found, in the form of granular caps on the megaspores of a Permian-age plant called a lycopsid. They also found evidence that these high energy treats may have been the power bars of early spore spreading.
“We suggest that these starch caps were used to attract and reward animals for megaspore dispersal,” explains lead author Feng Liu, of the Nanjing Institute of Geology and Palaeontology, in Nanjing, China. The study, published online ahead of print for the journal Geology, also provides early evidence for mutualism between plants and animals.
Lycopsids were vascular plants, ancestors of modern club mosses. They thrived in the teeming swamp forests of the Permian, about 280 million years ago. The fossil megaspores of lycopsids, with remarkably well-preserved starch granule toppings, were found in Permian-age coal in northern China.
Plant seeds store starch internally to nourish seedlings. But after analyzing the starch masses in the fossil megaspores using scanning electron microscopy and transmission electron microscopy, and comparing them to modern seeds, the scientists concluded that the starch caps were only outside, not inside, the megaspore. That means the starch wasn’t part of the lycopsids’ embryo nutrient system. Instead, the granules likely existed specifically as a spore-spreading device.
Ants, birds, and mammals weren’t around 280 million years ago, so the authors speculate that snails, along with arthropods like millipedes and cockroaches, may have been the main consumers of the scrumptious starch snacks. In turn, they dispersed the lycopsid megaspores. While starch certainly existed long before the Permian, this discovery dishes up new insights into its ecological role, says Feng Liu. “It can help us better understand the terrestrial animal food habit and the complexity of biotic interactions in deep geological time.” Plus, it shows that starchy food was a creature comfort long before the days of fettucine.
Reference:
Feng Liu, Benjamin Bomfleur, Huiping Peng, Quan Li, Hans Kerp, Huaicheng Zhu. 280-m.y.-old fossil starch reveals early plant–animal mutualism. Geology, 2018; DOI: 10.1130/G39929.1
An example of coastal boulder deposits on Inishmaan, Aran Islands. The cliffs are about 20 m high, and the boulders are piled 32-42 m inland from the cliff edge. Note the people near the cliff edge, showing the scale. Some of the boulders in this ridge, weighing many tonnes, were moved by storm waves in the winter of 2013-2014. Credit: Peter Cox
It’s not just tsunamis that can change the landscape: storms shifted giant boulders four times the size of a house on the coast of Ireland in the winter of 2013-14, leading researchers to rethink the maximum energy storm waves can have — and the damage they can do.
In a new paper in Earth Science Reviews, researchers from Williams College in the US show that four years ago, storms moved huge boulders along the west coast of Ireland. The same storms shifted smaller ones as high as 26 meters above high water and 222 meters inland. Many of the boulders moved were heavier than 100 tons, and the largest moved was 620 tons — the equivalent of six blue whales or four single-storey houses.
It was previously assumed that only tsunamis could move boulders of the size seen displaced in Ireland, but the new paper provides direct evidence that storm waves can do this kind of work. According to the UN, about 40 percent of the world’s population live in coastal areas (within 100 meters of the sea), so millions of people are at risk from storms. Understanding how those waves behave, and how powerful they can be, is key for preparation. It is therefore important to know the upper limits of storm wave energy, even in areas where these kinds of extreme wave energies are not expected.
“The effect of the storms of winter 2013-14 was dramatic,” said Dr. Rónadh Cox, Professor and Chair of Geosciences at Williams College and lead author of the study. “We had been studying these sites for a number of years, and realised that this was an opportunity to measure the coastal response to very large storm events.”
In the summer after the storms, Prof. Cox and a team of seven undergraduate students from Williams College surveyed 100 sites in western Ireland, documenting with photos the displacement of 1,153 boulders. They measured the dimensions and calculated the mass of each boulder. They knew where 374 of the boulders had come from, so for those they also documented the distance travelled. The largest boulder, at 237-239 m3 was an estimated 620 tons; the second biggest, at 180-185 m3, was about 475 tons. These giant rocks were close to sea level (although above the high tide mark). At higher elevations, and at greater distances inland, smaller boulders moved upwards and inland.
Analysis of this information showed that the waves had most power at lower elevations and closer to the shore. While this may not be surprising, the sheer energy of the waves and their ability to move such large boulders was — and this evidence proves that not only tsunami but also storm waves can move such large objects.
“These data will be useful to engineers and coastal scientists working in other locations,” said Prof. Cox. “Now that we know what storm waves are capable of, we have much more information for policy makers who are responsible for preparing coastal communities for the impact of high-energy storms.”
Reference:
Rónadh Cox, Kalle L. Jahn, Oona G. Watkins, Peter Cox. Extraordinary boulder transport by storm waves (west of Ireland, winter 2013–2014), and criteria for analysing coastal boulder deposits. Earth-Science Reviews, 2018; 177: 623 DOI: 10.1016/j.earscirev.2017.12.014
Note: The above post is reprinted from materials provided by Elsevier.
The application of extreme pressure dramatically affects the chemical properties of xenon, so that it stops acting aloof and interacts with iron and nickel. This illustration shows how the changes in the electromagnetic properties of xenon, iron, and nickel under these intense pressures allow for the formation of XeFe3 and XeNi3. Credit: Image is courtesy of the research team: Alexander Goncharov, Hanyu Liu, Elissaios Stavrou, Sergey Lobanov, Yansun Yao, Joseph Zaug, Eran Greenberg, and Vitali Prakapenka
The paradox of the missing xenon might sound like the title of the latest airport thriller, but it’s actually a problem that’s stumped geophysicists for decades. New work from an international team including Carnegie’s Alexander Goncharov and Hanyu Liu, and Carnegie alumni Elissaios Stavrou and Sergey Lobanov, is chasing down the solution to this longstanding puzzle.
The mystery stems from meteorites, which retain a record of our Solar System’s earliest days. One type, called carbonaceous chondrites, contain some of the most-primitive known samples of Solar System material, including a lot more xenon than is found in our own planet’s atmosphere.
“Xenon is one of a family of seven elements called the noble gases, some of which, such as helium and neon, are household names,” said lead author Stavrou, now at Lawrence Livermore National Laboratory, about the team’s paper in Physical Review Letters. “Their name comes from a kind of chemical aloofness; they normally do not combine, or react, with other elements.”
Because xenon doesn’t play well with others, it’s deficiency in Earth’s atmosphere — even in comparison to other, lighter noble gases, like krypton and argon, which theoretical predictions tell us should be even more depleted than xenon — is difficult to explain.
That doesn’t mean many haven’t tried.
This research team — which also included Yansun Yao of the University of Saskatchewan, Joseph Zaug also of LLNL, and Eran Greenberg, and Vitali Prakapenka of the University of Chicago — focused their attention on the idea that the missing xenon might be found deep inside the Earth, specifically hidden in compounds with nickel and, especially, iron, which forms most of the planet’s core.
It’s been known for a while that although xenon doesn’t form compounds under ambient conditions, under the extreme temperatures and pressures of planetary interiors it isn’t quite so aloof.
“When xenon is squashed by extreme pressures, its chemical properties are altered, allowing it to form compounds with other elements,” Lobanov explained.
Using a laser-heated diamond anvil cell, the researchers mimicked the conditions found in the Earth’s core and employed advanced spectroscopic tools to observe how xenon interacted with both nickel and iron.
They found that xenon and nickel formed XeNi3 under nearly 1.5 million times normal atmospheric pressure (150 gigapascals) and at temperatures of above about 1,200 degrees Celsius (1,500 kelvin). Furthermore, at nearly 2 million times normal atmospheric pressure (200 gigapascals) and at temperatures above about degrees 1,700 degrees Celsius (2000 kelvin), they synthesized complex XeFe3 compounds.
“Our study provides the first experimental evidence of previously theorized compounds of iron and xenon existing under the conditions found in the Earth’s core,” Goncharov said. “However, it is unlikely that such compounds could have been made early in Earth’s history, while the core was still forming, and the pressures of the planet’s interior were not as great as they are now.”
The researchers are investigating whether a two-stage formation process could have trapped xenon in Earth’s early mantle and then later incorporated it into XeFe3 when the core separated and the pressure increased. But more work remains to be done.
Reference:
Elissaios Stavrou, Yansun Yao, Alexander F. Goncharov, Sergey S. Lobanov, Joseph M. Zaug, Hanyu Liu, Eran Greenberg, Vitali B. Prakapenka. Synthesis of Xenon and Iron-Nickel Intermetallic Compounds at Earth’s Core Thermodynamic Conditions. Physical Review Letters, 2018; 120 (9) DOI: 10.1103/PhysRevLett.120.096001
Illustration of Euoplocephalus, an ankylosaur. Ankylosaurids are sometimes called the ‘tanks of the Cretaceous’ given their squat bodies and armored hides. Credit: Brett Booth Brett Booth
A scientist with the Canadian Museum of Nature has answered a long-standing mystery about why fossils of ankylosaurs—the “armoured tanks” of the dinosaur world—are mainly found belly-side up. In doing so, he has ruled out three other competing theories involving clumsiness, predation, and the effects of bloating as seen in armadillo roadkills.
Palaeontologist Dr. Jordan Mallon says the evidence points to a phenomenon called “bloat-and-float”, whereby the bloating carcasses of ankylosaurs would end up in a river, flip belly-side up due to the weight of their heavy armour, and then float downstream. The remains would wash ashore, where decomposition and then fossilization would seal the dinosaur remains in their upside-down death pose.
“Textbooks have touted that ankylosaur fossils are usually found upside down, but no one has gone back and checked the records to make sure that’s the case,” explains Mallon. The observations date from the 1930s. Indeed, the fossils of two star ankylosaurs described in 2017, Borealopelta from Alberta and Zuul from Montana, were found upside down.
Mallon examined 32 ankylosaur fossils from Alberta (of which 26 were found belly up), photos of specimens, field notes, and other signs such as erosion of the exposed surface, sun bleaching, and the presence of lichens.
The results are published in the online journal Palaeogeography, Palaeoclimatology, Palaeoecology. Collaborators included armadillo experts Drs. Colleen McDonough and Jim Loughry of Valdosta State University in Georgia, and Dr. Don Henderson, with Drumheller Alberta’s Royal Tyrrell Museum of Palaeontology.
Mallon ruled out three other theories before settling on “bloat-and-float” to explain the preponderance of the belly-up remains.
“One idea was that ankylosaurs were simply clumsy, tripping over themselves or rolling down hills and ending up dying that way,” he says. But since ankylosaurs existed for about 100 million years, clumsy habits would not fit with their apparent evolutionary success.
Another theory was that ankylosaurs were prey for carnivores, such as hungry tyrannosaurids, which would flip the armoured dinosaurs onto their backs to get at the soft underbelly. “If this was true, we would expect to see signs of bite marks, especially on upside-down ones, but we saw marks on only one specimen,” explains Mallon. “Since they were armoured, it makes sense that ankylosaurs were not regularly preyed upon, and the fossil evidence in museum collections supports this.”
The third idea, proposed in the 1980s, is an analogy to what happens with some armadillo roadkills—as the carcass rots and bloats, gas accumulates, and the limbs would splay out, eventually rolling the animal onto its back.
The challenge was to test this hypothesis. Enter McDonough and Loughry who are experts on modern armadillos, which also have an armoured shell. Over the summer of 2016, they studied 174 examples of dead armadillo. “Sure enough, the data show that they do not occur more often on their backs,” says Mallon. The pair even examined dead armadillos placed in plexiglass cases in their backyard to keep away scavengers. Regardless of the positioning of the carcasses, bloating did not cause them to roll over onto their backs.
That left the “bloat-and-float” hypothesis as the most likely explanation for the presence of upside-down fossils. To study this, Mallon turned to computer simulations developed by Dr. Don Henderson, who specializes in the floating behaviour of animals in water.
Ankylosaur fossils in North America are found in river channel deposits, and in the Late Cretaceous Period these animals would have been living along a coastline of what is known as the Western Interior Seaway.
“We designed these models of ankylosaurs, both clubless and clubbed, and looked at their floating behavior,” explains Mallon. The computer modelling showed that the animals would tend to flip upside down quite easily in water. Nodosaurids, which are ankylosaurs with no tail clubs, would flip most easily at the slightest tilt; the ankyosaurids (with clubbed tails), were more stable but could still be flipped.
“So ‘bloat-and-float'” fits with their known environment, and this research helps inform about the transport behavior of dead dinosaurs, which is important to know when studying fossil ecosystems. Ultimately, this is a classic case study of the scientific method: examining alternative hypotheses, finding ways to test them, and ruling them out one-by-one. What you are left with at the end is the most likely explanation.”
Reference:
Jordan C. Mallon et al, A “bloat-and-float” taphonomic model best explains the upside-down preservation of ankylosaurs, Palaeogeography, Palaeoclimatology, Palaeoecology (2018). DOI: 10.1016/j.palaeo.2018.02.010
A fieldwork photo from Réunion Island shows the flank of the Cirque de Cilaos, looking out towards the Indian Ocean. Credit: Courtesy of Bradley Peters
Plumes of hot magma from the volcanic hotspot that formed Réunion Island in the Indian Ocean rise from an unusually primitive source deep beneath Earth’s surface, according to new work in Nature from Carnegie’s Bradley Peters, Richard Carlson, and Mary Horan along with James Day of the Scripps Institution of Oceanography.
Réunion marks the present-day location of the hotspot that 66 million years ago erupted the Deccan Traps flood basalts, which cover most of India and may have contributed to the extinction of the dinosaurs. Flood basalts and other hotspot lavas are thought to originate from different portions of Earth’s deep interior than most volcanoes at Earth’s surface and studying this material may help scientists understand our home planet’s evolution.
The heat from Earth’s formation process caused extensive melting of the planet, leading Earth to separate into two layers when the denser iron metal sank inward toward the center, creating the core and leaving the silicate-rich mantle floating above.
Over the subsequent 4.5 billion years of Earth’s evolution, deep portions of the mantle would rise upwards, melt, and then separate once again by density, creating Earth’s crust and changing the chemical composition of Earth’s interior in the process. As crust sinks back into Earth’s interior — a phenomenon that’s occurring today along the boundary of the Pacific Ocean — the slow motion of Earth’s mantle works to stir these materials, along with their distinct chemistry, back into the deep Earth.
But not all of the mantle is as well-blended as this process would indicate. Some older patches still exist — like powdery pockets in a poorly mixed bowl of cake batter. Analysis of the chemical compositions of Réunion Island volcanic rocks indicate that their source material is different from other, better-mixed parts of the modern mantle.
Using new isotope data, the research team revealed that Réunion lavas originate from regions of the mantle that were isolated from the broader, well-blended mantle. These isolated pockets were formed within the first ten percent of Earth’s history.
Isotopes are elements that have the same number of protons, but a different number of neutrons. Sometimes, the number of neutrons present in the nucleus make an isotope unstable; to gain stability, the isotope will release energetic particles in the process of radioactive decay. This process alters its number of protons and neutrons and transforms it into a different element. This new study harnesses this process to provide a fingerprint for the age and history of distinct mantle pockets.
Samarium-146 is one such unstable, or radioactive, isotope with a half-life of only 103 million years. It decays to the isotope neodymium-142. Although samarium-146 was present when Earth formed, it became extinct very early in Earth’s infancy, meaning neodymium-142 provides a good record of Earth’s earliest history, but no record of Earth from the period after all the samarium-146 transformed into neodymium-142. Differences in the abundances of neodymium-142 in comparison to other isotopes of neodymium could only have been generated by changes in the chemical composition of the mantle that occurred in the first 500 million years of Earth’s 4.5 billion-year history.
The ratio of neodymium-142 to neodymium-144 in Réunion volcanic rocks, together with the results of lab-based mimicry and modeling studies, indicate that despite billions of years of mantle mixing, Réunion plume magma likely originates from a preserved pocket of the mantle that experienced a compositional change caused by large-scale melting of Earth’s earliest mantle.
The team’s findings could also help explain the origin of dense regions right at the boundary of the core and mantle called large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs), reflecting the unusually slow speed of seismic waves as they travel through these regions of the deep mantle. Such regions may be relics of early melting events.
“The mantle differentiation event preserved in these hotspot plumes can both teach us about early Earth geochemical processes and explain the mysterious seismic signatures created by these dense deep-mantle zones,” said lead author Peters.
Funding for fieldwork for this study was provided by the National Geographic Society (NGS 8330-07), the Geological Society of America (GSA 10539-14), and by a generous personal donation from Dr. R. Rex. Support for laboratory work was provided by Carnegie Institution for Science.
Reference:
Bradley J. Peters, Richard W. Carlson, James M. D. Day, Mary F. Horan. Hadean silicate differentiation preserved by anomalous 142Nd/144Nd ratios in the Réunion hotspot source. Nature, 2018; 555 (7694): 89 DOI: 10.1038/nature25754
Earth’s geomagnetic field surrounds and protects our planet from harmful space radiation. Credit: CC BY-SA 2.0 photo / Flickr user NASA Goddard Space Flight Center
Using new data gathered from sites in southern Africa, University of Rochester researchers have extended their record of Earth’s magnetic field back thousands of years to the first millennium.
The record provides historical context to help explain recent, ongoing changes in the magnetic field, most prominently in an area in the Southern Hemisphere known as the South Atlantic Anomaly.
“We’ve known for quite some time that the magnetic field has been changing, but we didn’t really know if this was unusual for this region on a longer timescale, or whether it was normal,” says Vincent Hare, who recently completed a postdoctoral associate appointment in the Department of Earth and Environmental Sciences (EES) at the University of Rochester, and is lead author of a paper published in Geophysical Research Letters.
The new data also provides more evidence that a region in southern Africa may play a unique role in magnetic pole reversals.
“We’re getting stronger evidence that there’s something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field.”
The magnetic field that surrounds Earth not only dictates whether a compass needle points north or south, but also protects the planet from harmful radiation from space. Nearly 800,000 years ago, the poles were switched: north pointed south and vice versa. The poles have never completely reversed since, but for the past 160 years, the strength of the magnetic field has been decreasing at an alarming rate. The region where it is weakest, and continuing to weaken, is a large area stretching from Chile to Zimbabwe called the South Atlantic Anomaly.
In order to put these relatively recent changes into historical perspective, Rochester researchers — led by John Tarduno, a professor and chair of EES — gathered data from sites in southern Africa, which is within the South Atlantic Anomaly, to compile a record of Earth’s magnetic field strength over many centuries. Data previously collected by Tarduno and Rory Cottrell, an EES research scientist, together with theoretical models developed by Eric Blackman, a professor of physics and astronomy at Rochester, suggest the core region beneath southern Africa may be the birthplace of recent and future pole reversals.
“We were looking for recurrent behavior of anomalies because we think that’s what is happening today and causing the South Atlantic Anomaly,” Tarduno says. “We found evidence that these anomalies have happened in the past, and this helps us contextualize the current changes in the magnetic field.”
The researchers discovered that the magnetic field in the region fluctuated from 400-450 AD, from 700-750 AD, and again from 1225-1550 AD. This South Atlantic Anomaly, therefore, is the most recent display of a recurring phenomenon in Earth’s core beneath Africa that then affects the entire globe.
“We’re getting stronger evidence that there’s something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field,” Tarduno says.
The researchers gathered data for this project from an unlikely source: ancient clay remnants from southern Africa dating back to the early and late Iron Ages. As part of a field called “archaeomagnetism,” geophysicists team up with archaeologists to study the past magnetic field.
The Rochester team, which included several undergraduate students, collaborated with archaeologist Thomas Huffman of the University of Witwatersrand in South Africa, a leading expert on Iron Age southern Africa. The group excavated clay samples from a site in the Limpopo River Valley, which borders Zimbabwe, South Africa, and Botswana.
During the Iron Age in southern Africa, around the time of the first millennium, there was a group of Bantu-speaking people who cultivated grain and lived in villages composed of grain bins, huts, and cattle enclosures. Draughts were devastating to their agriculturally based culture. During periods of draught, they would perform elaborate ritual cleansings of the villages by burning down the huts and grain bins.
“When you burn clay at very high temperatures, you actually stabilize the magnetic minerals, and when they cool from these very high temperatures, they lock in a record of the Earth’s magnetic field,” Tarduno says.
Researchers excavate the samples, orient them in the field, and bring them back to the lab to conduct measurements using magnetometers. In this way, they are able to use the samples to compile a record of Earth’s magnetic field in the past.
The magnetic field is generated by swirling, liquid iron in Earth’s outer core. It is here, roughly 1800 miles beneath the African continent, that a special feature exists. Seismological data has revealed a denser region deep beneath southern Africa called the African Large Low Shear Velocity Province. The region is located right above the boundary between the hot liquid outer core and the stiffer, cooler mantle. Sitting on top of the liquid outer core, it may sink slightly, disturbing the flow of iron and ultimately affecting Earth’s magnetic field.
A major change in the magnetic field would have wide-reaching ramifications; the magnetic field stimulates currents in anything with long wires, including the electrical grid. Changes in the magnetic field could therefore cause electrical grid failures, navigation system malfunctions, and satellite breakdowns. A weakening of the magnetic field might also mean more harmful radiation reaches Earth — and trigger an increase in the incidence of skin cancer.
Hare and Tarduno warn, however, that their data does not necessarily portend a complete pole reversal.
“We now know this unusual behavior has occurred at least a couple of times before the past 160 years, and is part of a bigger long-term pattern,” Hare says. “However, it’s simply too early to say for certain whether this behavior will lead to a full pole reversal.”
Even if a complete pole reversal is not in the near future, however, the weakening of the magnetic field strength is intriguing to scientists, Tarduno says. “The possibility of a continued decay in the strength of the magnetic field is a societal concern that merits continued study and monitoring.”
This study was funded by the US National Science Foundation.
Reference:
Vincent J. Hare, John A. Tarduno, Thomas Huffman, Michael Watkeys, Phenyo C. Thebe, Munyaradzi Manyanga, Richard K. Bono, Rory D. Cottrell. New Archeomagnetic Directional Records From Iron Age Southern Africa (ca. 425-1550 CE) and Implications for the South Atlantic Anomaly. Geophysical Research Letters, 2018; 45 (3): 1361 DOI: 10.1002/2017GL076007
A tiny extinct rail (30-40g) is overshadowed by a regular duck. Credit: Gavin Mouldey
Fossilized bones of two new species of tiny, flightless extinct birds have been discovered by Australasian scientists in 19 to 16-million-year-old sediments of an ancient lake on the South Island of New Zealand.
The two miniscule species—one barely larger than a sparrow—were members of the rail family, a group of birds common today in wetlands that includes swamphens, moorhens, coots and crakes. Their remains were unearthed near the town of St Bathans in Central Otago.
Many rail species can fly well and have dispersed to far-flung oceanic islands. However, flightlessness has evolved more times in this group of birds that in any other, especially on predator-free islands. The world’s largest rails evolved in New Zealand, notably the flightless takahe and weka.
The study, led by scientists from Flinders University with colleagues from UNSW, Canterbury Museum and the Museum of New Zealand, is published in the Journal of Systematic Palaeontology.
Team member UNSW Professor Mike Archer, says: “This new discovery emphasizes the fact that New Zealand has long been one of the world’s most extraordinary engines driving bird evolution.
“Charting how lineages like these rails have changed through time on an island that has been geographically isolated for more than 80 million years will test basic presumptions made about bird evolution in general,” says Professor Archer of the of the PANGEA Research Centre in the School of Biological, Earth and Environmental Sciences.
Nineteen to 16 million years ago, a 5600 square kilometre megalake dominated the landscape of New Zealand’s South Island. It was surrounded by a subtropical rainforest and plants typical of Australia and long lost from New Zealand, such as eucalypts, casuarinas, palms and cycads, were common there.
“Flightlessness in birds is often associated with an increase in size,” says Ellen Mather, study lead author and Ph.D. student at Flinders University. “The weka, which is in the same family as our fossil birds and lives in New Zealand today, is about the size of a chicken. The Banded Rail, their closest flying relative, is about half that size.”
The most common of the new fossil rails has been named Priscaweka parvales, meaning ancient weka with small wings. It was a mere one twentieth of the weight of a weka and was similar in size to the recently extinct Chatham rail Cabalus modestus.
Small flightless birds only exist in the absence of terrestrial mammalian predators, and New Zealand has long been recognised as the iconic example of a country with an avifauna which evolved in the absence of such predators.
When humans discovered New Zealand, the main islands had many flightless birds including giants within the nine species of moa, several kiwi, two huge geese, two adzebills, even some tiny wrens, and at least five flightless rails.
Team member, Dr. Paul Scofield, a Senior Curator at the Natural History at Canterbury Museum, says: “The new St Bathans’ rails join a host of other fossil birds recovered from these deposits that show New Zealand has long been a land of birds. The discovery of these two miniscule flightless rails raises the question of ‘Where did they come from?'”
The researchers suggest they had ancestors in Australia which flew across the 1500 km ocean to New Zealand in previous millennia. However, the new species are unlike any rail known elsewhere, so their exact origin or closest relatives remain a mystery.
Other than hints of large flightless moa ancestors, these rails are the first flightless birds to be described from this fauna. This is unexpected as the St Bathans Fauna contains small terrestrial mammals, which normally preclude evolution of small flightless species. The tiny flightless rails therefore strongly suggest that the mysterious mammals were not predators of small birds. Flightless birds have been a feature of the New Zealand avifauna for millions of years, much longer than previously thought. They are probably the oldest flightless rails known globally.
“The ongoing research into the fossil birds of New Zealand builds on that begun over 150 years ago. It continues to throw up revelations into the timing and origins of major groups of birds that characterize modern avifaunas” says Associate Professor Trevor Worthy of Flinders University.
Mount Etna. Credit: Angelo T. La Spina, Lizenz: CC BY-SA 4.0
Mount Etna in southern Italy is one of the most active volcanoes on Earth, while the Hyblean Volcanoes, located further south, are extinct today. An international team of scientists with the participation of the GFZ searched for the source of magmas of Etna and examined why the ground south of Etna does not emit lava anymore. The results have now been published in the scientific journal Earth & Planetary Science Letters.
Volcanic eruptions and earthquakes most frequently occur alongside of tectonic plate margins. Some volcanoes, however, also arise within a plate; researchers refer to this as “intraplate volcanism”. Well known examples are the chain of islands of Hawaii or the Canary Islands. The volcanoes in Eastern Sicily are of the same type. For about five hundred thousand years now, Etna, a mountain of 3300 meters height, is an active volcano. The Hyblean Volcanoes, however, that were active until about one million years ago, form a mountain range on the southernmost edge of Sicily.
Movements in the deep migrate volcanoes
The scientists modelled the pathways of magma below the Hyblean Volcanoes and Etna, down to the Earth’s crust-mantle boundary in about 30 kilometers depth. The model shows: Magma pathways, also referred to as dikes, both for Etna and the Hyblean Volcanoes all bend to the East and meet with the crust-mantle boundary below the Malta Escarpment. The Malta Escarpment is a system tectonically active now for hundreds of millions of years. It stretches alongside the eastern Sicilian coastline for more than three hundred kilometres, far into the Mediterranean Sea. Often, earthquakes originate in this region. Over the past ten million years, the Earth’s crust in this region was compressed and expanded in different directions again and again.
These movements together with a deepening of the fault scarp led to bent, not vertical, magmatic dikes. Over time, this also resulted in a northwestward migration of active volcanism. Eleonora Rivalta, GFZ section Physics of Earthquakes and Volcanoes, co-author of the study: „Our findings show that Etna and the Hyblean Volcanoes represent eruptions of different ages of the same volcanic system.“ In the future, similar models may be applied to other regions to show where origins of magmas are and how dikes develop over time. (ak)
Reference:
Neri, M., Rivalta, E., Maccaferri, F., Acocella, V., Cirrincione, R., 2018. Etnean and Hyblean volcanism shifted away from the Malta Escarpment by crustal stresses. Earth and Planetary Science Letters, Volume 486, 15-22 pp. DOI: 10.1016/j.epsl.2018.01.006
This is crushed dentine from a Woolly Mammoth for DNA extraction. Credit: JD Howell, McMaster University
An international team of researchers has produced one of the most comprehensive evolutionary pictures to date by looking at one of the world’s most iconic animal families — namely elephants, and their relatives mammoths and mastodons-spanning millions of years.
The team of scientists-which included researchers from McMaster, the Broad Institute of MIT and Harvard, Harvard Medical School, Uppsala University, and the University of Potsdam-meticulously sequenced 14 genomes from several species: both living and extinct species from Asia and Africa, two American mastodons, a 120,000-year-old straight-tusked elephant, and a Columbian mammoth.
The study, published in the Proceedings of the National Academy of Science, sheds light on what scientists call a very complicated history, characterized by widespread interbreeding. They caution, however, the behaviour has virtually stopped among living elephants, adding to growing fears about the future of the few species that remain on earth.
“Interbreeding may help explain why mammoths were so successful over such diverse environments and for such a long time, importantly this genomic data also tells us that biology is messy and that evolution doesn’t happen in an organized, linear fashion,” says evolutionary geneticist Hendrik Poinar, one of the senior authors on the paper and Director of the McMaster Ancient DNA Centre and principal investigator at the Michael G. DeGroote Institute for Infectious Research.
“The combined analysis of genome-wide data from all these ancient elephants and mastodons has raised the curtain on elephant population history, revealing complexity that we were simply not aware of before,” he says.
A detailed DNA analysis of the ancient straight-tusked elephant, for example, showed that it was a hybrid with portions of its genetic makeup stemming from an ancient African elephant, the woolly mammoth and present-day forest elephants.
“This is one of the oldest high-quality genomes that currently exists for any species,” said Michael Hofreiter at the University of Potsdam in Germany, a co-senior author who led the work on the straight-tusked elephant.
Researchers also found further evidence of interbreeding among the Columbian and woolly mammoths, which was first reported by Poinar and his team in 2011. Despite their vastly different habitats and sizes, researchers believe the woolly mammoths, encountered Columbians mammoths at the boundary of glacial and in the more temperate ecotones of North America.
Strikingly, scientists found no genetic evidence of interbreeding among two of the world’s three remaining species, the forest and savanna elephants, suggesting they have lived in near-complete isolation for the past 500,000 years, despite living in neighbouring habitats.
“There’s been a simmering debate in the conservation communities about whether African savannah and forest elephants are two different species,” said David Reich, another co-senior author at the Broad Institute who is also a professor at the Department of Genetics at Harvard Medical School (HMS) and a Howard Hughes Medical Institute Investigator. “Our data show that these two species have been isolated for long periods of time — making each worthy of independent conservation status.”
Interbreeding among closely related mammals is fairly common, say researchers, who point to examples of brown and polar bears, Sumatran and Bornean orangutans, and the Eurasian gold jackal and grey wolves. A species can be defined as a group of similar animals that can successfully breed and produce fertile offspring.
“This paper, the product of a grand initiative we started more than a decade ago, is far more than just the formal report of the elephant genome. It will be a reference point for understanding how diverse elephants are related to each other and it will be a model for how similar studies can be done in other species groups,” said co-senior author Kerstin Lindblad-Toh, a senior associate member of the Broad Institute and Director of the Science for Life Laboratory at Uppsala University in Sweden.
“The findings were extremely surprising to us,” says Eleftheria Palkopoulou, a post-doctoral scientist in at HMS. “The elephant population relationships could not be explained by simple splits, providing clues for understanding the evolution of these iconic species.”
Researchers suggest that future work should explore whether the introduction of new genetic lineages into elephant populations-both living and ancient-played an important role in their evolution, allowing them to adapt to new habitats and fluctuating climates.
Reference:
Eleftheria Palkopoulou, Mark Lipson, Swapan Mallick, Svend Nielsen, Nadin Rohland, Sina Baleka, Emil Karpinski, Atma M. Ivancevic, Thu-Hien To, R. Daniel Kortschak, Joy M. Raison, Zhipeng Qu, Tat-Jun Chin, Kurt W. Alt, Stefan Claesson, Love Dalén, Ross D. E. MacPhee, Harald Meller, Alfred L. Roca, Oliver A. Ryder, David Heiman, Sarah Young, Matthew Breen, Christina Williams, Bronwen L. Aken, Magali Ruffier, Elinor Karlsson, Jeremy Johnson, Federica Di Palma, Jessica Alfoldi, David L. Adelson, Thomas Mailund, Kasper Munch, Kerstin Lindblad-Toh, Michael Hofreiter, Hendrik Poinar, David Reich. A comprehensive genomic history of extinct and living elephants. Proceedings of the National Academy of Sciences, 2018; 201720554 DOI: 10.1073/pnas.1720554115
Note: The above post is reprinted from materials provided by McMaster University.
Research led by The University of Texas at Austin has found that weathered bedrock can store a significant amount of rock moisture inside its fractures and pores. This moisture in the layer of weathered rock that is commonly located beneath soils is an important part of the water cycle on the local and global level. Tree roots tap into the rock moisture and release it back into the atmosphere as water vapor, and water flows through the fractures and becomes part of the seasonal groundwater storage (blue arrows). Credit: University of Texas at Austin Jackson School of Geosciences.
Research conducted by The University of Texas at Austin and University of California, Berkeley has found that a little-studied, underground layer of rock can hold significant amounts of water that may serve as a vital reservoir for trees, especially in times of drought.
The study, published in the journal PNAS on February 26 looked at the water stored inside the layer of weathered bedrock that commonly lies under soils in mountainous environments.
This transitional zone beneath soils and above groundwater is often overlooked when it comes to studying hydrological processes, but researchers found that the water contained within the fractures and pores of the rock could play an important role in the water cycle at the local and global level.
“There are significant hydrologic dynamics in weathered bedrock environments, but they are not traditionally investigated because they are hard to access,” said lead author Daniella Rempe, an assistant professor in the Department of Geological Sciences at the UT Austin Jackson School of Geosciences. “The study was designed to investigate this region directly.”
Researchers found the water within the bedrock has the ability to sustain trees through droughts even after the soil has become parched. At the field site in Northern California’s Mendocino County, scientists found that up to 27 percent of annual rainfall was stored as “rock moisture,” the water clinging to cracks and pores within the bedrock The impact of rock moisture will vary depending on the region and topography, but researchers said it likely explains how the trees in the study area showed little affect from the severe 2010-2015 drought that killed more than 100 million trees throughout California.
“How trees can survive extended periods of severe drought has been a mystery,” said Richard Yuretich, director of the National Science Foundation’s Critical Zone Observatories program, which funded the research. “This study has revealed a significant reservoir of trapped water that has gone unnoticed in the past. Research of this kind can help greatly in managing natural resources during times of environmental stress.”
To conduct the study, researchers monitored the rock moisture from 2013-2016 at nine wells drilled into the weathered bedrock along a steep forested hillslope. They used a neutron probe, a precision tool that measures the amount of water in a sample area by detecting hydrogen.
They found that the weathered rock layer built up a supply of 4 to 21 inches of rock moisture during the winter wet season, depending on the well. The maximum amount of rock moisture in each well stayed about the same throughout the study period, which included a significant drought year. It’s a major finding that indicates that it doesn’t matter if it rains a little or a lot during the winter dry season—the total rainfall amount does not influence the rock moisture levels.
“It doesn’t matter how much it rains in the winter, rock moisture builds up to the same maximum value,” Rempe said. “That leads to the same amount of water every summer that’s available for use by trees.”
Researchers also found that the average rock moisture at all wells exceeded the average soil moisture measurements at all locations.
“Soils are important, but when it comes to determining if a place is going to experience water stress, it could be the underlying rock that matters most,” Rempe said. “This is the first time this has been demonstrated in a multi-year field study.”
The potential for rock moisture to travel back to the atmosphere via evaporation from tree leaves or to trickle down into groundwater indicates that it could have a broad impact on the environment and climate. Zong-Liang Yang, a professor in the Jackson School’s Department of Geological Sciences who was not involved in the study, said that the research highlights the need to gather data so rock moisture can be incorporated into climate models.
“At present, most, if not all, of global climate and hydrological models neglect moisture stored in rocks,” Yang said. “This study fills a critical gap in our understanding.”
The study provides a glimpse into rock moisture at a small, intensive research site, said co-author William Dietrich, a professor at the University of California, Berkeley. He said the data collected during this study should be a starting point for more research in more places.
“The future paths are many,” Dietrich said. “We have just one site well-studied… A mixture of theory and field studies will need to be developed to provide regional information for climate modelers.”
Reference:
Daniella M. Rempe el al., “Rock moisture: Direct observations of a hidden component of the hydrologic cycle,” PNAS (2018). DOI: 10.1073/pnas.1800141115
The tropical rainforests of Central and South America are home to the largest diversity of plants on this planet. Nowhere else are there quite so many different plant species in one place. However, the entire region is increasingly threatened by human activity, which is why researchers are stepping up their efforts to record this astonishing biodiversity and find out how it developed. In a project undertaken by Johannes Gutenberg University Mainz (JGU) in collaboration with Dutch research institutions, the causes of this plant diversity were investigated by studying two closely related groups of trees of the Annonaceae family.
The researchers identified three relevant factors: the formation of the Andes mountain range, the disappearance due to natural causes of the extensive Pebas wetlands system that once existed in the Amazon region, and the formation of a land bridge between Central and South America in the form of the Panama Isthmus.
Cremastosperma and Mosannona are two genera of the Annonaceae or custard apple family the habitat of which is neotropical rainforests, where they extend from the lowlands up to elevations of 2,000 meters. They are primarily found in the Andes region of South America, but also as far north as Central America. The team of botanists led by Dr. Michael Pirie, who joined JGU as a researcher in 2013, looked at the distributions of the various species of both genera and their phylogenetic history in order to determine the influence of the geological upheavals on the continent. For this purpose they compiled a time-calibrated phylogenetic tree based on DNA data, using the so-called molecular clock technique which is calibrated using the ages of the available fossils. In total, they analyzed 11 species of the genus Mosannona and 24 species of the genus Cremastosperma.
Formation of the Andes, the Isthmus of Panama, and the drying-out of the Pebas wetland system all promoted diversification
The research has produced a biogeographical scenario that confirms in this context the significance of the geological history of north-western South America during the late Miocene and early Pliocene periods about 5 to 10 million years ago. “We have actually discovered that the diversification of these two plant genera took place in parallel with major geological events, namely the formation of the Andes, the drying-out of the Pebas system, and the development of a land bridge to Central America,” explained Pirie. Cremastosperma species, for example, were able to spread into what is today the Amazon basin and diversify, once the wetlands had silted up due to the deposition of material from the rising Andes.
One way in which diversification can be stimulated is by migration into a new ecosystem while another is adaptation to new conditions. “Natural changes over longer periods provide plants with a chance to adapt,” added Pirie. On the other hand, rapid changes, such as those that have occurred in the recent past, do not give plants sufficient time to evolve.
While the development of the two genera in line with geological conditions could be said to be more or less as might be expected, the biologists did find one clear difference between them. Although their distribution patterns mostly overlap, Cremastosperma species and Mosannona species to some extent dispersed along differing routes. In the case of Cremastosperma, colonization of an area in what is now Guyana began from north-western South America at a time before the last parts of the Andes developed and could form a barrier. Mosannona, on the other hand, began to spread here at a far later date from its base in the Amazon basin.
Taxonomic update to include five new species
Dr. Michael Pirie will be continuing his research work in 2018 with the aid of a grant from the Heisenberg Program of the German Research Foundation (DFG). This will also involve publication of an extensive monograph in which a total of 34 Cremastosperma species will be described, including five new species that Pirie and his colleagues have recently discovered.
Reference:
Michael D. Pirie, Paul J. M. Maas, Rutger A. Wilschut, Heleen Melchers-Sharrott, Lars W. Chatrou. Parallel diversifications of Cremastosperma and Mosannona (Annonaceae), tropical rainforest trees tracking Neogene upheaval of South America. Royal Society Open Science, 2018; 5 (1): 171561 DOI: 10.1098/rsos.171561
For the first time, researchers have seen life rebounding in the world’s driest desert, demonstrating that it could also be lurking in the soils of Mars.
Led by Washington State University planetary scientist Dirk Schulze-Makuch, an international team studied the driest corner of South America’s Atacama Desert, where decades pass without any rain.
Scientists have long wondered whether microbes in the soil of this hyperarid environment, the most similar place on Earth to the Martian surface, are permanent residents or merely dying vestiges of life, blown in by the weather.
In a new study published in the Proceedings of the National Academy of Sciences, Schulze-Makuch and his collaborators reveal that even the hyper-arid Atacama Desert can provide a habitable environment for microorganisms.
The researchers found that specialized bacteria are able to live in the soil, going dormant for decades, without water and then reactivating and reproducing when it rains.
“It has always fascinated me to go to the places where people don’t think anything could possibly survive and discover that life has somehow found a way to make it work,” Schulze-Makuch said. “Jurassic Park references aside, our research tell us that if life can persist in Earth’s driest environment there is a good chance it could be hanging in there on Mars in a similar fashion.”
The dry limit of life
When Schulze-Makuch and his collaborators went to the Atacama for the first time in 2015 to study how organisms survive in the soil of Earth’s driest environment, the craziest of things happened.
It rained.
After the extremely rare shower, the researchers detected an explosion of biological activity in the Atacama soil.
They used sterilized spoons and other delicate instrumentation to scoop soil samples from various depths and then performed genomic analyses to identify the different microbial communities that were reproducing in the samples. The researchers found several indigenous species of microbial life that had adapted to live in the harsh environment.
The researchers returned to the Atacama in 2016 and 2017 to follow up on their initial sampling and found that the same microbial communities in the soil were gradually reverting to a dormant state as the moisture went away.
“In the past researchers have found dying organisms near the surface and remnants of DNA but this is really the first time that anyone has been able to identify a persistent form of life living in the soil of the Atacama Desert,” Schulze-Makuch said. “We believe these microbial communities can lay dormant for hundreds or even thousands of years in conditions very similar to what you would find on a planet like Mars and then come back to life when it rains.”
Implications for life on Mars
While life in the driest regions of Earth is tough, the Martian surface is an even harsher environment.
It is akin to a drier and much colder version of the Atacama Desert. However it wasn’t always this way.
Billions of years ago, Mars had small oceans and lakes where early lifeforms may have thrived. As the planet dried up and grew colder, these organisms could have evolved many of the adaptations lifeforms in the Atacama soil use to survive on Earth, Schulze-Makuch said.
“We know there is water frozen in the Martian soil and recent research strongly suggests nightly snowfalls and other increased moisture events near the surface,” he said. “If life ever evolved on Mars, our research suggests it could have found a subsurface niche beneath today’s severely hyper-arid surface.”
Next Steps
On March 15, Schulze-Makuch is returning to the Atacama for two weeks to investigate how the Atacama’s native inhabitants have adapted to survive. He said his research team also would like to look for lifeforms in the Don Juan Pond in Antarctica, a very shallow lake that is so salty it remains liquid even at temperatures as low as -58 degrees Fahrenheit.
“There are only a few places left on Earth to go looking for new lifeforms that survive in the kind of environments you would find on Mars,” Schulze-Makuch said. “Our goal is to understand how they are able to do it so we will know what to look for on the Martian surface.”
Reference:
Dirk Schulze-Makuch el al., “Transitory microbial habitat in the hyperarid Atacama Desert,” PNAS (2018). DOI: 10.1073/pnas.1714341115
This is the sampling site Lomas Bayas in the core region of the Atacama. Credit: Dirk Schulze-Makuch, TU Berlin
The core region of the Atacama Desert in South America is one of the most arid places on earth. Sometimes it is raining only once in a decade or even less, the annual precipitation is far less than 20 mm. The dry conditions resulted in high salt concentrations in the soil and low organic matter content. However, scientists have found microorganisms there. But it has remained unclear whether these environments support active microbial growth or whether the observed cells were introduced by wind transport and subsequently degraded. Detailed analyses by an international research team show: Even in the most arid zones of the Atacama a microbial community exists which becomes metabolically active following episodic increase in moisture after rainfalls. The new findings, published in the journal PNAS, are important for evolution of life and landscapes on Earth. Moreover, the results have implications for the prospect of life on other planets – certainly for Mars.
The scientists took soil samples at six different locations in the Atacama Desert between 2015 and 2017. “We have chosen sample locations along a profile of decreasing moisture from the coast up to extreme arid conditions in the core region of the Atacama”, explains first author Dirk Schulze-Makuch from the TU Berlin. “This gradient should be reflected in the life-friendly conditions – we call it habitability – as well as in the number and diversity of the microorganisms.”
To get the whole picture the scientists used a broad range of complementary methods carried out at several geoscientific institutions in Berlin and Potsdam together with international partners. Amongst others the team conducted physico-chemical characterizations of the soil habitability and molecular biological studies. The latter were done mainly at GFZ German Research Centre for Geosciences in Potsdam where intracellular and extracellular DNA was analysed. “With this method we can find out which microorganisms really exist at the different locations in the Atacama probably doing metabolism and which ones are only represented by their naked DNA in the sediment as a signal from the past,” says Dirk Wagner, Head of GFZ-Section for Geomicrobiology and one of the leading authors of the article. “Further investigations like tests on enzymes have shown that the suspected organisms in most cases are in fact metabolically active.”
To scientists it is not only important to know where microbial life exists, it is also relevant to know about changes over time. Here they were lucky: First sampling in April 2015 occurred shortly after an unexpected rain event. The moisture had positive effects on life and activity in the desert. This is documented in samples taken and analysed in the following years in February 2016 and January 2017.
“We can clearly show that some time after a precipitation event, the abundance and biological activity of microorganisms decreases”, says Wagner. But the organisms, which are predominantly bacteria, do not completely die off. According to the authors, single-celled organisms are found mainly in the deeper layers of the Atacama Desert where they have formed active communities for millions of years and have evolved to cope with the harsh conditions.
The findings from the South American desert are very useful for the question of life on other planets, especially in relation to Mars. Martian climate was initially humid, rivers and lakes had existed before the desertification began. No rain can fall from the thin Martian atmosphere today but liquid water can be present near the surface due to nightly snowfall. Additionally, there is fog and on some slopes also salty brines, which sporadically flow down and thus provide fluids. However, the exposure to hard radiation at the surface is much greater than on Earth. Based on the results of the study, the authors come to the conclusion: If life ever evolved on Mars in the past, under better conditions, it could have endured the transition to hyper-arid conditions and perhaps even be found in subsurface niches today.
Reference:
A Transitory Microbial Habitat in the Hyperarid Atacama Desert, Dirk Schulze-Makuch, Dirk Wagner, Samuel Kounaves et al., PNAS, DOI: 10.1073/pnas.1714341115
Ground-running bird model may predict bipedal dinosaur locomotion. Credit: Peter Bishop, Queensland Museum CC-BY
A new model based on ground-running birds could predict locomotion of bipedal dinosaurs based on their speed and body size, according to a study published February 21, 2018 in the open-access journal PLOS ONE by Peter Bishop from the Queensland Museum, Australia and colleagues.
Previous research has investigated the biomechanics of ground-dwelling birds to better understand the how bipedal non-avian dinosaurs moved, but it has not previously been possible to empirically predict the locomotive forces that extinct dinosaurs experienced, especially those species that were much larger than living birds. Bishop and colleagues examined locomotion in 12 species of ground-dwelling birds, ranging in body mass from 45g to 80kg, as the birds moved at various speeds along enclosed racetracks while cameras recorded their movements and forceplates measured the forces their feet exerted upon the ground.
The researchers found that many physical aspects of bird locomotion change continuously as speed increases. This supports previous evidence that unlike humans, who have distinct “walking” and “running” gaits, birds move in a continuum from “walking” to “running.” The authors additionally observed consistent differences in gait and posture between small and large birds.
The researchers used their data to construct the biomechanically informative, regression-derived statistical (BIRDS) Model, which requires just two inputs — body mass and speed — to predict basic features of bird locomotion, including stride length and force exerted per step. The model performed well when tested against known data. While more data are needed to improve the model, and it is unclear if it can be extrapolated to animals of much larger body mass, the researchers hope that it might help predict features of non-avian dinosaur locomotion using data from fossils and footprints.
Reference:
Bishop PJ, Graham DF, Lamas LP, Hutchinson JR, Rubenson J, Hancock JA, et al. The influence of speed and size on avian terrestrial locomotor biomechanics: Predicting locomotion in extinct theropod dinosaurs. PLOS ONE, 2018 DOI: 10.1371/journal.pone.0192172
Note: The above post is reprinted from materials provided by PLOS.
Schematic evolution of retrogressive slope failure due to overpressured gas below the gas haydrate stability zone (GHSZ): a submarine slope with gas hydrate-bearing sediments and overpressured gas (bright area) at the bottom of the GHSZ induces pipe generation into the GHSZ, the conduit encounters a permeable layer; gas enters and leads to overpressure transfer from the bottom of the GHSZ to the shallow subsurface, and finally overpessured gas causes shear banding in the weak layer and generates retrogressive slope failure. Credit: Helmholtz Association of German Research Centres
Like avalanches onshore, there are different processes that cause submarine landslides. One very widespread assumption is that they are associated with dissociating gas hydrates in the seafloor. However, scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel have now found evidence that the context could be quite different. Their study has been published in Nature Communications.
In the mid-1990s, German scientists, among others, were able to prove that the continental slopes at ocean margins contain large amounts of gas hydrates. These solid, ice-like compounds of water and gas are often considered a kind of cement, which stabilizes the slopes. Since gas hydrates are only stable at high pressure and low temperature, rising water temperatures can cause gas hydrates to dissociate, or ‘melt’, in simple terms. It has been suggested previously that large-scale gas hydrate dissociation could cause submarine landslides that could in turn trigger tsunamis. The fact that many fossil landslides correlate spatially with sediments containing gas hydrates seems to strengthen this argument.
Now, researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, together with colleagues from Kiel University and the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, have found evidence that gas hydrates and submarine landslides are indeed linked — but in a quite different way than previously thought. “Our data show that stable gas hydrates can indirectly destabilize the sediment above,” says Dr. Judith Elger from GEOMAR. She is the lead author of the study, which has been published in the international journal Nature Communications.
An inconsistency in the previous theory, which focused on melting gas hydrates as the cause of submarine landslides, was the starting point of the new research. “The water depths did not match. With rising water temperatures or decreasing sea levels, gas hydrate melting would be initiated around the upper parts of continental slopes. However, most known fossil submarine landslides were triggered in greater depths,” explains Dr. Elger.
To resolve this contradiction, the geophysicist examined seismic data from the area of the Hinlopen Slide, which occurred about 30,000 years ago north of Svalbard in 750 to 2,200 meters water depth. The team used the seismic data to simulate new processes with a computer model.
It turned out that gas hydrates can form a solid, impermeable layer beneath the seafloor. Free gas and other fluids can accumulate below this layer. Over time they create overpressure. Eventually, gas hydrates and sediments no longer withstand this elevated pore pressure and hydro fractures form in the sediments. These fractures form conduits that transfer overpressure to shallower coarse-grained sediments and thereby trigger shallow slope failure. In the case of the Hinlopen Slide, these fluid conduits are still visible in the seismic data.
“We were able to show that this process is a realistic alternative to other triggering processes for the Hinlopen Slide, and it is completely independent of climatic changes. However, important information about the properties of gas hydrate-bearing sediments is still lacking to improve our models,” says Dr. Elger.
In any case, the study shows a new causal process that has not been considered so far in the search for causes of submarine landslides. “Further studies that combine seismic data and geotechnical laboratory experiments must now show whether similar fractures can be detected beneath the seafloor on other historical landslides and whether this is a common phenomenon,§ Dr. Elger concludes.
Reference:
Judith Elger, Christian Berndt, Lars Rüpke, Sebastian Krastel, Felix Gross, Wolfram H. Geissler. Submarine slope failures due to pipe structure formation. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-03176-1
Teide volcano in Tenerife. Credit: Dr Janine Kavanagh, University of Liverpool
A novel research study by scientists at the University of Liverpool has provided new insights into how molten rock (magma) moves through the Earth’s crust to feed volcanic eruptions.
Using laboratory experiments involving water, jelly and laser imaging, researchers were able to demonstrate how magma flows through the Earth’s crust to the surface through magma-filled cracks called dykes.
This new approach to studying magma flow revealed that prior to a volcanic eruption there was recirculation of the fluid in the dyke and instability in the flow, details which had previously not been documented before.
Nearly all volcanic eruptions are fed by dykes that transport magma from its source to the surface. Understanding how magma travels through these dykes to the surface is central to forecasting the style, longevity and climatic impact of volcanic eruptions.
Researchers created a scaled-down model of an active volcanic plumbing system using a perspex tank filled with gelatine, representing the Earth’s crust, and then injected this with dyed water, representing the magma.
They applied cutting-edge laser imaging techniques to look inside the model. Passive-tracer particles added to the fluid glowed in a laser sheet to allow the flow of the model magma to be mapped as the dyke grew.
Digital cameras recorded changes in the shape of the model volcanic plumbing system over time and the changes to the surface of the crust was recorded using an overhead laser scanner. Polarized light allowed subsurface stress patterns that would result in rock fracturing in nature to be observed as the dyke grew.
This novel experimental setup allowed, for the first time, the simultaneous measurement of fluid flow, sub-surface and surface deformation during the magma ascent through magma-filled fractures.
This finding will help inform the interpretation of data from field studies and geophysical surveys, which will ultimately improve our ability to understand if an eruption is likely to happen.
Liverpool volcanologist, Dr Janine Kavanagh, who heads up the University’s specialist MAGMA laboratory, said “For the first time, using innovative laboratory experiments that combined our knowledge of volcanic plumbing systems with engineering expertise, we have managed to see how magma flows through the Earth’s crust to the surface through dykes.
“Our experiments, the first to use laser imaging technology in this way, revealed a strong coupling between surface deformation patterns and subsurface processes.
“This indicates that it is both the magma properties and the host rock properties that controls how the dyke ascends, which is a brand new finding and challenges our existing thinking on magma flow through rocks.
“As it’s not possible to always successfully predict volcanic events due to the lack of complete knowledge of the signals leading to catastrophes, these results are an important new finding and ultimately we hope they will contribute to our understanding of where and when the next volcanic eruption will be.”
With more than 800 million people worldwide living near a volcano at risk of eruptive activity, understanding the triggers for volcanic eruptions is vital for forecasting efforts, hazard assessment, and risk mitigation.
The paper ‘Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism’ is published in the Journal of Volcanology and Geothermal Research.
Reference:
Janine L. Kavanagh et al, Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism, Journal of Volcanology and Geothermal Research (2018). DOI: 10.1016/j.jvolgeores.2018.01.002
Erosional Pleistocene shorelines in Surprise Valley, California, USA. Credit: Anne Egger
The vestiges of lakes long extinct dot the landscape of the American desert west. These fossilized landforms provide clues of how dynamic climate has been over the past few million years.
Identification of ancient lake shoreline features began with early explorers of the continent. The first detailed studies were conducted by pioneering American geologists such as G.K. Gilbert and I.C. Russell in the late 1800s, who studied Lake Bonneville, now the remnant Great Salt Lake in Utah, and Lake Lahonton, located in northwestern Nevada.
Through this long history of studying fossil shorelines and lake sediments, we know that these lakes existed during two periods with distinct environmental conditions during the geologically recent past. The first was during ice age maxima, such as the last ice age, 14 to 30 thousand years ago, when global temperatures were 4 to 6 degrees colder and continental ice sheets expanded into the continental United States.
The second time period was about three million years ago during the middle of the Pliocene epoch—a global climate characterized by warmer temperatures and atmospheric CO2 levels roughly equivalent to today’s values, which has led many scientists to view the Pliocene as a potential analogue for future climate change.
These observations lead to an important question, says the study’s lead author, Daniel Ibarra, “Why are there lake systems under both colder and warmer climates, but not today?” Of particular interest, he says, is the presence of lakes under warmer conditions, which, under a “wet gets wetter, dry gets drier” paradigm, goes against projections of future warming.
To answer this question, Ibarra and colleagues looked at the competing influences of temperature and precipitation, and how they combine to allow for the existence of lakes under these dual climate states.
The authors compiled evidence for, and created models of, lakes during both colder and warmer than modern periods of the Pliocene-Pleistocene (the last 5 million years). During colder glacial periods, they found that increased precipitation and decreased evaporation combined to form large lakes that occupied the inward draining basins in the western United States, particularly in northern Nevada and Utah.
Increased precipitation also drove the formation of lakes, particularly in southern Nevada and southern California during the warmer middle Pliocene, outpacing higher temperatures and evaporation rates during that time. This increase in precipitation during the middle Pliocene and dominantly southwestern distribution of lake deposits is similar to the pattern of precipitation during modern El Niño years, corroborating previous hypotheses for mean “El Niño-like” conditions during the mid-Pliocene.
The team’s interdisciplinary approach explains the conditions driving lake systems in mid-latitude regions today and over the geologic past. Further, notes Ibarra, “This work illustrates the importance of understanding how the El Niño Southern Oscillation drives precipitation patterns in arid regions, which is important for future water resources planning for the western United States.”
Reference:
Gilbert G. K., 1884, The topographic features of lake shores. United States Geological Survey, Fifth Annual Report, 69–123.
DE Ibarra, AE Egger, KL Weaver, CR Harris, K Maher, 2014, Rise and fall of late Pleistocene pluvial lakes in response to reduced evaporation and precipitation: Evidence from Lake Surprise, California, Geological Society of America Bulletin, 126 (11-12), 1387-1415. DOI: 10.1130/G39962.1
