Scanning Electron Micrographs of Fossil Charcoal of a small primitive fern-like plant from from the late Devonian (355 million years ago) from North America. Credit: Image courtesy of University of Royal Holloway London
A study, carried out by Professor Andrew C. Scott of the Department of Earth Sciences at Royal Holloway, University of London and Professor Sue Rimmer from Southern Illinois University, reveals widespread fire occurred on Earth more than 80 million years after plants first invaded the land.
The findings, published in the American Journal of Science, indicate that although plants were first detected on land more than 440 million years ago there is only scant evidence of fire at that time.
Professor Scott, said: “What surprised us was that many of these early extensive fires were surface fires burning the undergrowth, as we can see the anatomy of the plants being burned through scanning electron microscope studies of larger pieces of the fossil charcoal.”
He added: “This may be because plants were small and were limited in their distribution but over the following 50 million years they diversified and spread across the globe and some of the plants were trees and could have provided a good fuel to burn. Extensive forest fires soon followed, however and we see widespread charcoal deposits throughout the Lower Carboniferous (Mississippian) Period 358-323 million years ago.”
Professor Scott and Professor Rimmer made the discovery after analysing charcoal which was washed in to an ocean that lay across what is now part of present day North America.
The team believes that it was not fuel availability that prevented widespread fire, or climate, but that the atmospheric oxygen levels were too low. It had been suggested that only when oxygen levels rose to above 17% (it is 21% today) that widespread fires would be found. This new data suggests that it was at around 360 million years ago, in the latest Devonian Period, that this threshold was reached and probably never went below this level for the rest of geological history.
This time period defines a new phase of the evolution of Earth System and regular wildfire would have played an important role in the evolution of both animals and plants.
Reference:
S. M. Rimmer, S. J. Hawkins, A. C. Scott, W. L. Cressler. The rise of fire: Fossil charcoal in late Devonian marine shales as an indicator of expanding terrestrial ecosystems, fire, and atmospheric change. American Journal of Science, 2015; 315 (8): 713 DOI: 10.2475/08.2015.01
Setting of the La Habra quake. Red dots show the magnitude 5.1 main shock, magnitude 4.1 aftershock and magnitude 5.4 Chino quake in 2008. Relocated aftershocks are green dots. Modeled faults are in brown, with the heavier reddish brown line denoting the bottom of the fault and labeled with italics. Credit: NASA/JPL-Caltech
A new NASA-led analysis of a moderate magnitude 5.1 earthquake that shook Greater Los Angeles in 2014 finds that the earthquake deformed Earth’s crust across a broad region encompassing the northern Los Angeles Basin and northern Orange County. The shallow ground movements observed from this earthquake likely reflect strain accumulated on deeper faults, which remain locked and may be capable of producing future earthquakes.
A team of NASA and university researchers led by geophysicist Andrea Donnellan of NASA’s Jet Propulsion Laboratory, Pasadena, California, used GPS and NASA airborne radar data to measure surface deformation in Earth’s crust caused by the March 28, 2014, earthquake, which was centered in La Habra, California. The earthquake was felt widely in Orange, Los Angeles, Ventura, Riverside, San Bernardino, Kern and San Diego counties. While the earthquake was relatively moderate in size, the earthquake’s depth (3.6 miles, or 5.85 kilometers) and location within a highly populated region resulted in more than $12 million in damage. Most of the damage occurred within a 3.7-mile (6-kilometer) radius of the epicenter, with a substantial amount of damage south of the main rupture.
Donnellan’s team found the earthquake deformed Earth’s crust across a broad region, but mostly south of the main rupture, consistent with the observed damage. They measured 3.1 inches (80 millimeters) of northward horizontal motion and about 0.2 to 0.4 inches (5 to 10 millimeters) of upward motion.
They also discovered that the total amount of surface deformation associated with the La Habra earthquake was larger than what would be expected from the magnitude 5.1 main shock. Eighty-two percent of the surface motion was attributed to the earthquake itself, with the remaining 18 percent occurring aseismically, without producing any ground shaking. The amount of aseismic motion was greater than expected. The team’s results show that even moderate earthquakes near Los Angeles can produce ground deformation and damage to water mains away from their epicenters.
The team used computer models to explain the observed patterns of ground deformation and found that the best explanation for the observed ground deformation was shallow movement along several active buried fault-like zones in the West Coyote Hills in northern Orange County; in the Chino Hills on the border of Orange, Los Angeles and San Bernardino Counties; and in the San Gabriel Valley. The modeled movements identified by the team in the San Gabriel Valley and Chino Hills are part of a series of incompletely mapped active faults in a geologically complex region. It is likely the deeper portions of these faults remain locked and thus are capable of producing future earthquakes.
“The earthquake faults in this region are part of a system of faults,” said Donnellan. “They can move together in an earthquake and produce measurable surface deformation, even during moderate magnitude earthquakes. This fault system accommodates the ongoing shortening of Earth’s crust in the northern Los Angeles region.” Tectonic motion across the Los Angeles region is distributed on an intricate network of horizontally and vertically moving faults that eventually release accumulated strain in the form of earthquakes, such as the destructive 1994 magnitude-6.7 Northridge earthquake.
Donnellan said a future earthquake to release the accumulated strain on these faults could occur on any one or several of these fault structures, which may not have been mapped at the surface. “Identifying specific fault structures most likely to be responsible for future earthquakes for this system of many active faults is often very difficult,” she said.
The earthquake ground displacements were measured by combining pre- and post-earthquake continuous GPS data from the National Science Foundation’s Plate Boundary Observatory with NASA’s airborne radar data from the JPL-developed Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). UAVSAR is an L-band Interferometric SAR instrument mounted beneath a C-20A Earth science research aircraft from NASA’s Armstrong Flight Research Center, Edwards, California. It detects minute (less than centimeter-level) changes in Earth’s surface that occur over time between flights. NASA has been using UAVSAR to monitor deformation across the Los Angeles region about every six months since 2009.
Co-author Lisa Grant Ludwig of the University of California, Irvine, said the team’s analysis can be used by policymakers and government agencies to improve assessments of earthquake risk in the Los Angeles area that are critical for disaster planning.
“The study builds upon more than two decades of NASA-led research to develop new methods to better measure and monitor movements of the solid Earth using satellite and airborne data and advanced computer modeling,” Donnellan said. “It also provides a means of using these technologies to identify which faults moved during earthquakes, to measure exactly how much Earth’s surface deformed during earthquakes, and to use these measurements to estimate future earthquake potential.”
Reference:
Andrea Donnellan et al. Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake, Earth and Space Science (2015). DOI: 10.1002/2015EA000113
Note: The above post is reprinted from materials provided by NASA.
It is well known that an earthquake in one part of the world can trigger others thousands of kilometers away.
But in a paper published in the journal Science Advances, researchers reveal that these triggered earthquakes are just one outward sign of far more widespread changes taking place below the Earth’s surface.
Earthquakes can fundamentally change the elastic properties of the Earth’s crust in regions up to 6,000 kilometers away, altering its ability to withstand stresses for a period of up to a few weeks, according to Kevin Chao, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences and a member of a research team led by Andrew Delorey at Los Alamos National Laboratory.
The research demonstrates that the Earth is a dynamic and interconnected system, where one large earthquake can create a cascading sequence of events thousands of kilometers away, Chao says.
Earthquakes occur when stress builds up along a tectonic fault. This stress causes the two surfaces of the fault, which had previously been stuck together due to friction, to suddenly move, or slide, releasing energy in the form of seismic waves.
These waves take the form of both body waves, which cause the shaking movement that does so much damage during a quake, and surface waves. Surface waves can travel thousands of kilometers beneath the ground.
Surface wave propagation
When a surface wave from an earthquake some way off passes through another fault region, it changes the balance between the frictional properties that keep the surfaces locked together, the elasticity that allows the crust to withstand strain, and the stress state that can cause it to fail, Chao says.
“When surface waves pass through, all of these properties rearrange and change,” he says. “If a fault with high stress is ready to fail, it will accumulate more stresses in the fault, meaning an earthquake could occur at any time.”
To demonstrate these changes, the researchers studied the 2012 earthquake off the coast of North Sumatra in the Indian Ocean. The earthquake, which had a magnitude of 8.6, is known to have been followed by two earthquakes in Japan with a magnitude greater than 5.5.
When the researchers studied data from strain meter readings, GPS equipment, and information on seismicity — or the number of small-magnitude earthquakes — in the region, as well as the migration of the earthquakes, they found that the two triggered quakes with a magnitude of greater than 5.5 were part of a cluster of activity in the area in the days after the Indian Ocean event.
“When the Indian Ocean earthquake occurred, the surface wave passed through the northeast of Japan, and the seismicity in the region was suddenly triggered,” Chao says. “During that time of increased seismicity, there were three triggered earthquakes in the region with a magnitude of greater than 5.5,” he says.
This region of the Earth’s crust was already critically stressed following the major Japanese earthquake of 2011, so the additional stress, albeit temporary, caused by the surface wave passing through, was enough to trigger another cluster of quakes.
When a fault fails and an earthquake occurs, it also pushes into the neighboring region, reducing the available space and compressing the crust in this area.
So the researchers also looked for signs of compressive stress in this region of Japan following the Indian Ocean earthquake. They found signs that cracks in the rock under the Japanese mainland were closing as a result of compressive stress, increasing the shear strength of the crust.
Pervasive deformation
While the research will not in itself allow us to predict earthquakes, it does help to increase our understanding of how they are triggered, as well as how the Earth’s crust behaves, Chao says.
“We still cannot say that there will definitely be another earthquake after the first one has struck, because although we know there will be changes, we do not know the existing stress conditions in every region, so we cannot predict anything with certainty,” Chao says.
“But one important thing we can say is that we know earthquakes do interact with each other, because surface waves can travel thousands of kilometers, and change the elasticity in another region,” he adds.
Reference:
Andrew A. Delorey, Kevin Chao, Kazushige Obara and Paul A. Johnson. Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake. DOI: 10.1126/sciadv.1500468
An artist’s impression of the innumerable Earth-like planets that have yet to be born over the next trillion years in the evolving universe. Credit: NASA / ESA / G. Bacon (STScI)
Earth came early to the party in the evolving universe. According to a new theoretical study, when our solar system was born 4.6 billion years ago only eight percent of the potentially habitable planets that will ever form in the universe existed. And, the party won’t be over when the sun burns out in another 6 billion years. The bulk of those planets — 92 percent — have yet to be born.
This conclusion is based on an assessment of data collected by NASA’s Hubble Space Telescope and the prolific planet-hunting Kepler space observatory.
“Our main motivation was understanding the Earth’s place in the context of the rest of the universe,” said study author Peter Behroozi of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, “Compared to all the planets that will ever form in the universe, the Earth is actually quite early.”
Looking far away and far back in time, Hubble has given astronomers a “family album” of galaxy observations that chronicle the universe’s star formation history as galaxies grew. The data show that the universe was making stars at a fast rate 10 billion years ago, but the fraction of the universe’s hydrogen and helium gas that was involved was very low. Today, star birth is happening at a much slower rate than long ago, but there is so much leftover gas available that the universe will keep cooking up stars and planets for a very long time to come.
“There is enough remaining material [after the big bang] to produce even more planets in the future, in the Milky Way and beyond,” added co-investigator Molly Peeples of STScI.
Kepler’s planet survey indicates that Earth-sized planets in a star’s habitable zone, the perfect distance that could allow water to pool on the surface, are ubiquitous in our galaxy. Based on the survey, scientists predict that there should be 1 billion Earth-sized worlds in the Milky Way galaxy at present, a good portion of them presumed to be rocky. That estimate skyrockets when you include the other 100 billion galaxies in the observable universe.
This leaves plenty of opportunity for untold more Earth-sized planets in the habitable zone to arise in the future. The last star isn’t expected to burn out until 100 trillion years from now. That’s plenty of time for literally anything to happen on the planet landscape.
The researchers say that future Earths are more likely to appear inside giant galaxy clusters and also in dwarf galaxies, which have yet to use up all their gas for building stars and accompanying planetary systems. By contrast, our Milky Way galaxy has used up much more of the gas available for future star formation.
A big advantage to our civilization arising early in the evolution of the universe is our being able to use powerful telescopes like Hubble to trace our lineage from the big bang through the early evolution of galaxies. The observational evidence for the big bang and cosmic evolution, encoded in light and other electromagnetic radiation, will be all but erased away 1 trillion years from now due to the runaway expansion of space. Any far-future civilizations that might arise will be largely clueless as to how or if the universe began and evolved.
Reference:
Peter Behroozi and Molly Peeples. On The History and Future of Cosmic Planet Formation. Monthly Notices of the Royal Astronomical Society, 2015 DOI: 10.1093/mnras/stv1817
Scientists think that New Zealand’s new shorebird species Hakawai melvillei, the Australian Plains-wanderer (Pedionomidae) and the South American Seedsnipes (Thinocoridae) all originated in East Gondwana. Credit: Image courtesy of Taylor & Francis
It is commonly known that birds evolved from dinosaurs. But what happened next? Today, shorebirds (otherwise known as waders) live in a wide variety of environments worldwide, from the Himalayas to Antarctica. With their long legs, shorebirds have long been a subject of evolutionary discussion, but where did they originate and how did they diverge into so many habitats across the globe? Due to a poor fossil record, these questions remain largely unanswered. However, a new article published in Journal of Systematic Palaeontology sheds new light on this mystery.
A new piece in this evolutionary puzzle has been presented by an international team of New Zealand and Australian-based scientists, including researchers at Canterbury Museum, who have confirmed that a 19-16 million-year-old shorebird fossil, discovered in Central Otago, New Zealand, belongs to a group of small birds including the Australian Plains-wanderer and the South American Seedsnipes.
The new species, Hakawai melvillei, is named after a ‘mystery bird’ in Māori mythology and in honour of New Zealand-based ornithologist and ecologist David Melville.
Hakawai melvillei was a small wading bird that lived about 19 million years ago during the Miocene epoch, around an ancient subtropical lake on the edge of a floodplain, with many other waterbirds, waterfowl, crocodilians and bats. The finding of individuals at chick or near fledging stage (known from their bone surface texture) shows that Hakawai melvillei was breeding in New Zealand and was not migratory, unlike many birds of this group today.
The closest relative of Hakawai melvillei is the extant Australian Plains-wanderer. These birds are also closely related to the South American Seedsnipes. Hakawai melvillei is extinct, but its ancient lineage and close relationships show how all these birds have a common ancestry in East Gondwana, before the landmass subsequently split up and New Zealand became isolated.
The long legs of the 19 million year old Hakawai melvillei show that it was a wader. The Australian Plains-wanderer and South American Seedsnipes have since independently evolved terrestrial adaptations, but this is evidence that these birds were ancestral waders.
Reference:
Vanesa L. De Pietri, R. Paul Scofield, Alan J. D. Tennyson, Suzanne J. Hand, Trevor H. Worthy. Wading a lost southern connection: Miocene fossils from New Zealand reveal a new lineage of shorebirds (Charadriiformes) linking Gondwanan avifaunas. Journal of Systematic Palaeontology, 2015; 1 DOI: 10.1080/14772019.2015.1087064
Millimeter-sized quartz crystals like this, which formed in molten magma, are the basis of the geospeedometer. The black dots are blebs of molten rock captured in the crystal when it formed. Credit: Gualda Lab, Vanderbilt University
Repeatedly throughout Earth’s history, giant pools of magma greater than 100 cubic miles in volume have formed a few miles below the surface.
They are the sources of super-eruptions – gigantic volcanic outbursts that throw 100 times more superheated gas, ash and rock into the atmosphere than run-of-the-mill eruptions, enough to blanket continents and plunge the globe into decades-long volcanic winters.
The most recent super-eruption took place about 27,000 years ago in New Zealand, well before humans kept records of volcanic eruptions and their aftermath. Geologists today are studying deposits from past super-eruptions to try and understand where and how rapidly these magma bodies develop and what causes them to eventually erupt. Despite considerable study, geologists are still debating how quickly these magma pools can be activated and erupted, with estimates ranging from millions to hundreds of years.
Now a team of geologists have developed a new “geospeedometer” that they argue can help resolve this controversy by providing direct measurements of how long the most explosive types of magma existed as melt-rich bodies of crystal-poor magma before they erupted. They have applied their new technique to two super-eruption sites and a pair of very large eruptions and found that it took them no more than 500 years to move from formation to eruption.
These results are described in the article “Melt inclusion shapes: Timekeepers of short-lived giant magma bodies” appearing in the November issue of the journal Geology.
“Geologists have developed a number of different ‘timekeepers’ for volcanic deposits. The fact that these techniques measure different processes and have different resolutions, has contributed to this lack of consensus. Our new method indicates that the process can take place within historically relevant spans of time,” said Guilherme Gualda, associate professor of earth and environmental sciences at Vanderbilt University, who directed the project. The method was developed as part of the doctoral thesis of Ayla Pamukcu, who is now a post-doctoral researcher at Brown and Princeton Universities.
“The hot spot under Yellowstone National Park has produced several super-eruptions in the past. The measurements that have been made indicate that this magma body doesn’t currently have a high-enough percentage of melt to produce a super-eruption. But now we know that, when or if it does reach such a state, we will only have a few hundred years to prepare ourselves for the consequences,” Gualda said.
The researchers’ geospeedometer is based on millimeter-sized quartz crystals that grew within the magma bodies that produced these giant eruptions. Quartz crystals are typically found in magmas that have a high percentage of silica. This type of magma is very viscous and commonly produces extremely violent eruptions. Mount St. Helens was a recent example.
When the crystals form, they often capture small blobs of molten magma – known as blebs or melt inclusions. Blebs are initially round. While the crystal is floating in hot magma, diffusion causes them to gradually acquire the polygonal shape of the crystal void that they occupy. But this faceting process can be halted if eruption occurs before complete faceting is achieved.
Using advanced 3-D X-ray tomography, the researchers were able to measure the size and shape of the melt inclusions with exquisite precision. In cases where the inclusions had not become completely faceted, the researchers could determine how much time had elapsed since they were enclosed.
“Previous studies provided us with the data we needed to calculate the rate of the faceting process. We then used this rate, in combination with our shape measurements, to calculate how long the crystal existed in the magma before the eruption,” said Pamukcu.
In addition, the researchers compared the results obtained with faceting with results obtained using other techniques. Crystallization may cause variations in concentration of certain elements. In quartz, the element titanium can vary sharply between different zones or layers within the crystal. Over time, however, the process of diffusion gradually smooths out these variations. This process also stops at the eruption, so the shallower the slope of titanium concentrations across these boundaries today, the longer the crystal spent in magmatic conditions.
The physics of this process is also well known, so the researchers could use these measurements to provide an independent estimate of how long a crystal spent floating around in the melt. They found that the duration times they derived from the titanium diffusion measurements agreed closely with those produced by the faceting method.
They applied their geospeedometer to four large eruptions:
Bishop Tuf in California that produced a super-eruption 760,000 years ago that blasted 240 cubic miles of dust, gas and rock into the atmosphere;
Oruanui in the Taupo Volcanic Zone in New Zealand that produced a super-eruption 27,000 years ago that released 130 cubic miles of material;
Ohakuri-Mamaku, a pair of high-volume eruptions that took place simultaneously in Taupo Volcanic Zone in New Zealand 240,000 years ago that together spewed out 60 cubic miles of material.
“Our current method will also work on smaller volcanic systems, as long as they erupt magmas that contain quartz crystals,” said Pamukcu. “We are also confident that we can adapt these techniques to work with other minerals, which will allow us to make similar timescale calculations for other types of magmas and volcanoes, like the low-silica basalts commonly erupted from Hawaiian volcanoes.”
Video
The outline of a millimeter-sized quartz crystal that formed in a magma chamber is shown in grey. Five blebs – blobs of molten rock that were captured in the crystal as it formed and grew – are shown as colored polygons. By analyzing the faceting of these blebs, the researchers can determine the length of time that the crystal spent floating in the molten rock before the volcano erupted. By comparing the time determined by the faceting with the distance between the blebs and the surface of the crystal, the researchers can also determine the growth rate of the crystals themselves – something which is still an unknown factor.
The bacteria M. alcaliphilum, shown here, was recently discovered to produce large amounts of the biolipid tetrahymanol. Credit: Paula Welander
Stanford scientists have discovered a surprising source for an organic molecule used as an indicator for life on early Earth.
Tetrahymanol is a fatty molecule, or lipid, found in the membranes enclosing eukaryotic cells, the class of cells that carry their genetic material in compartments called nuclei. Eukaryotes can be single-celled or multicellular; humans and plants are eukaryotes, as are plants.
It was thought that tetrahymanol was produced primarily by eukaryotes, but a new study suggests many bacteria might also produce the lipid. The finding, published in this week’s issue of the journal Proceedings of the National Academy of Sciences, could mean scientists will have to reevaluate their views about ancient organisms and ecosystems.
Evidence of tetrahymanol, and thus eukaryotic life, have been found in rocks dating back to 1.6 billion years ago. “Because they are so well preserved, these lipids allow us to go really deep into the rock record and learn about what life was like back then,” said geobiologist Paula Welander, an assistant professor of Earth system science at Stanford School of Earth, Energy & Environmental Sciences.
Unlike most other organic molecules, cyclic lipids – the class of lipids that tetrahymanol belongs to – are quite durable and can linger in the environment. So even after a cell has died and its other biomolecules such as DNA have degraded, the tetrahymanol that helped make up its cell membrane can remain. Over time, the lipid can become part of the rock itself.
Geobiologists use tetrahymanol not only as an indicator of ancient life, but also as a gauge of the environmental conditions that existed when the organisms that made the lipid lived. For example, modern marine eukaryotes ramp up the production of lipids such as tetrahymanol when stressed by a lack of oxygen. From this, scientists infer that ancient eukaryotes – which are also thought to have lived primarily in oceans – produced tetrahymanol when oxygen levels dropped, such as can occur in aquatic zones made up of water layers with varying oxygen concentrations.
“Tetrahymanol is a valuable indicator of water column stratification on the early Earth,” Welander said.
Prior to the new study, scientists knew of only two bacterial species that produced tetrahymanol in small amounts. “The conventional wisdom was that these organisms produced tetrahymanol accidentally,” Welander said.
But recently Amy Banta, a postdoctoral researcher in Welander’s group, and Jeremy Wei, a lab manager at Stanford, found evidence that the bacteria Methylomicrobium alcaliphilum produces lots of tetrahymanol. Using genetic manipulation techniques, the group showed that M. alcaliphilum was not making the lipid by accident.
“We could change the amount of tetrahymanol in the bacteria by tweaking its growth conditions. To us, that means it’s somehow controlling the production of this lipid,” Welander said.
By comparing the genomes of various bacteria, the team was also able to identify and delete the gene in M. alcaliphilum that produces the lipid – an important first step for determining what function tetrahymanol plays in bacteria.
Welander says her team’s finding that eukaryotes are not unique in producing and using tetrahymanol means that geobiologists will have to consider alternative explanations for its presence in ancient records.
“Scientists will have to take on a much more nuanced interpretation of what this molecule is telling us about life on early Earth,” she said.
Reference:
Amy B. Banta, Jeremy H. Wei1, and Paula V. Welander. A distinct pathway for tetrahymanol synthesis in bacteria. DOI: 10.1073/pnas.1511482112
The red abalone makes the lustrous but hard-as-nails nacre lining of its shell by changing the atomic structure of amorphous calcium carbonate to produce crystalline aragonite, the mineral that is the basis of nacre. Also known as mother-of-pearl, nacre has been worked by humans for millennia to make jewelry and fancy inlay for furniture and musical instruments. Credit: Pupa Gilbert
How nature makes its biominerals—things like teeth, bone and seashells—is a playbook scientists have long been trying to read.
Among the most intriguing biominerals is nacre, or mother-of-pearl—the silky, iridescent, tougher-than-rock composite that lines the shells of some mollusks and coats actual pearls. The material has been worked by humans for millennia to make everything from buttons and tooth implants to architectural tile and inlay for furniture and musical instruments.
But how nacre is first deposited by the animals that make it has eluded discovery despite decades of scientific inquiry. Now, a team of Wisconsin scientists reports the first direct experimental observations of nacre formation at its earliest stages in a mollusk.
Writing in the Journal of the American Chemical Society, a team led by University of Wisconsin-Madison physics Professor Pupa Gilbert and using the U.S. Department of Energy’s Advanced Light Source at the Lawrence Berkeley National Laboratory describes the precursor phases of nacre formation at both the atomic and nanometer scale in red abalone, a marine mollusk with a domed shell lined with mother-of-pearl.
“People have been trying to understand if nacre had an amorphous calcium carbonate precursor for a long time,” explains Gilbert, an expert on biomineral formation, referencing the non-crystalline calcium carbonate observed to set the stage for nacre formation. “There is just a tiny amount of amorphous material. It is very hard to catch it before it transforms.”
Gilbert and her colleagues, using the synchrotron radiation generated by the Advanced Light Source, employed spectro-microscopy to directly observe the chemical transformation of amorphous calcium carbonate to the mineral aragonite, which manifests itself as nacre by layering microscopic polygonal aragonite tablets like brickwork to underpin the lustrous and durable biomaterial. “We could only capture it in a handful of pixels, about 20 nanometers in size, at the surface of forming nacre tablets,” says Gilbert of the way the mollusk deposits hydrated amorphous calcium carbonate, which rapidly dehydrates and then crystalizes into aragonite.
“Amazing chemistry happens at the surface of forming nacre,” says Gilbert, noting that the transformation of amorphous calcium carbonate into crystalline aragonite involves calcium atoms, initially bonded to six oxygen atoms, and ultimately to nine in the crystalline biomineral. “It is how the atoms are arranged that matters. The actual chemical composition of calcium carbonate does not change. Only the structure does upon crystallization.”
That was the big surprise, observes Gilbert: “The change in atomic symmetry around calcium atoms, from six to nine oxygen atoms, surprised us. Everyone expected to find amorphous precursor minerals that already had the symmetry of the final crystal at the atomic scale, lacking only the long-range order of the crystals. We stand corrected.”
Gilbert says the new, detailed understanding of how nature makes mother-of-pearl may one day lend itself to industrial application. Highly durable bone implants are one example, and the material is also environmentally friendly.
Carbon in 4.1 billion year old zircon. Credit: Stanford/UCLA.
UCLA geochemists have found evidence that life likely existed on Earth at least 4.1 billion years ago — 300 million years earlier than previous research suggested. The discovery indicates that life may have begun shortly after the planet formed 4.54 billion years ago.
The research is published today in the online early edition of the journal Proceedings of the National Academy of Sciences.
“Twenty years ago, this would have been heretical; finding evidence of life 3.8 billion years ago was shocking,” said Mark Harrison, co-author of the research and a professor of geochemistry at UCLA.
“Life on Earth may have started almost instantaneously,” added Harrison, a member of the National Academy of Sciences. “With the right ingredients, life seems to form very quickly.”
The new research suggests that life existed prior to the massive bombardment of the inner solar system that formed the moon’s large craters 3.9 billion years ago.
“If all life on Earth died during this bombardment, which some scientists have argued, then life must have restarted quickly,” said Patrick Boehnke, a co-author of the research and a graduate student in Harrison’s laboratory.
Scientists had long believed the Earth was dry and desolate during that time period. Harrison’s research — including a 2008 study in Nature he co-authored with Craig Manning, a professor of geology and geochemistry at UCLA, and former UCLA graduate student Michelle Hopkins — is proving otherwise.
“The early Earth certainly wasn’t a hellish, dry, boiling planet; we see absolutely no evidence for that,” Harrison said. “The planet was probably much more like it is today than previously thought.”
The researchers, led by Elizabeth Bell — a postdoctoral scholar in Harrison’s laboratory — studied more than 10,000 zircons originally formed from molten rocks, or magmas, from Western Australia. Zircons are heavy, durable minerals related to the synthetic cubic zirconium used for imitation diamonds. They capture and preserve their immediate environment, meaning they can serve as time capsules.
The scientists identified 656 zircons containing dark specks that could be revealing and closely analyzed 79 of them with Raman spectroscopy, a technique that shows the molecular and chemical structure of ancient microorganisms in three dimensions.
Bell and Boehnke, who have pioneered chemical and mineralogical tests to determine the condition of ancient zircons, were searching for carbon, the key component for life.
One of the 79 zircons contained graphite — pure carbon — in two locations.
“The first time that the graphite ever got exposed in the last 4.1 billion years is when Beth Ann and Patrick made the measurements this year,” Harrison said.
How confident are they that their zircon represents 4.1 billion-year-old graphite?
“Very confident,” Harrison said. “There is no better case of a primary inclusion in a mineral ever documented, and nobody has offered a plausible alternative explanation for graphite of non-biological origin into a zircon.”
The graphite is older than the zircon containing it, the researchers said. They know the zircon is 4.1 billion years old, based on its ratio of uranium to lead; they don’t know how much older the graphite is.
The research suggests life in the universe could be abundant, Harrison said. On Earth, simple life appears to have formed quickly, but it likely took many millions of years for very simple life to evolve the ability to photosynthesize.
The carbon contained in the zircon has a characteristic signature — a specific ratio of carbon-12 to carbon-13 — that indicates the presence of photosynthetic life.
“We need to think differently about the early Earth,” Bell said.
Wendy Mao, an associate professor of geological sciences and photon science at Stanford University, is the other co-author of the research.
The research was funded by the National Science Foundation and a Simons Collaboration on the Origin of Life Postdoctoral Fellowship granted to Bell.
Reference:
Elizabeth A. Bell, Patrick Boehnke, T. Mark Harrison, and Wendy L. Mao. Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon. PNAS, October 19, 2015 DOI: 10.1073/pnas.1517557112
Using a rapid X-ray scanning technique developed for fossil studies at SLAC’s Stanford Synchrotron Radiation Lightsource, researchers studied the detailed chemistry of fossilized burrows, likely produced by sea worms 80 million years ago. These images show a black and white photograph of a cross-section of a fossil sample (left), a false-color scan of the sample’s iron content (middle, with iron concentrations shown in lighter shades), and a false-color scan of the phosphorous content (right, with phosphorous concentrations shown in lighter shades). Credit: D. Harazim, et al., Geology
Research at the Department of Energy’s SLAC National Accelerator Laboratory reveals new details about how tiny, burrowing sea organisms can influence the chemistry and structure of rocks where hydrocarbon deposits such as oil and gas are found.
An international team of scientists used X-rays to image the chemistry of rock samples containing well-preserved 80-million-year-old fossilized burrows, which may have been made by millimeter-sized bristly worms known as polychaetes. They found that the worms appeared to concentrate some chemical elements in their burrows while depleting others.
The study, published online Oct. 7 in the journal Geology, provides new insight into how ancient sea worms interact with the sediment on the ocean bottom and control the composition and geochemical signature of rocks formed by that sediment, which today serve as markers for ancient climate patterns and oil and gas reservoirs.
The pioneering X-ray scanning method that researchers used at SLAC opens up new ways to study Earth’s distant environmental and geological past and supports research about the formation of hydrocarbon deposits.
While it’s only in its early stages, the research shows a lot of promise, said Dario Harazim, a petroleum geologist who led the study while working as instructor at Memorial University of Newfoundland in Canada. “We might need to rethink the processes of how certain elements are incorporated into the rock record — how they are preserved and how we use them to reconstruct the chemistry and other properties of the ancient ocean,” Harazim said.
“To date, the ancient ocean temperatures, oxygen levels and other factors important in rock formation have been considered major drivers controlling the accumulation of trace elements in the rock,” he said. “Here, we provide new insight into how burrowing organisms play a major role in controlling the trace amounts of some elements in rocks formed from sediment.”
While the sea worms like the ones that likely made these ancient burrows are still important in the modern environment, they are difficult to observe because they are embedded in the sticky mud of the sea floor. Removing worms and their surrounding mud to a more convenient location for study would disrupt their relationship with their natural environment and might not yield trustworthy results.
From Dino Birds to Burrowing Worms
Harazim partnered with a research group based at University of Manchester to study exceptionally preserved rock samples from Baja California in Mexico. The Manchester group had worked with SLAC distinguished staff scientist Uwe Bergmann to develop a fast X-ray scanning technique for studying fossils at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility. The technique has been used to study chemical traces of feathers and tissues in a famous fossil link between birds and dinosaurs.
Unlike many conventional techniques, the unique fast-scanning technique at SSRL is non-destructive, so it preserved the features and localized chemistry of the worm burrows. It can also image large sample surfaces of up to tens of square centimeters.
“The large-scale imaging capabilities at SSRL permitted the precise mapping of very small chemical concentrations associated with these organisms’ interaction with their environment,” said Phillip Manning, a University of Manchester paleontologist who helped to pioneer the technique. “This latest collaboration between accelerator physics and paleontology has once again resurrected chemical ghosts that shed new light on key scientific questions.”
The study shows how a unique and sophisticated feeding strategy allows the sea worms to separate sediment particles of different sizes, Harazim said: “They consume mineral particles, clay and bacteria that live on the mineral surfaces. As this mix passes through their chemically aggressive gut, this material is getting broken down and degraded.”
The way the worms redistribute and digest these grains, and how they control the concentration of some elements, is still not well understood. Their feeding creates pockets of porous sediment that can potentially fill over time with concentrations of mineral cement, organic material and potentially even hydrocarbons.
The researchers, who verified the SSRL results with those obtained from other conventional methods, found that certain elements, including strontium and barium, are depleted from all areas of the rock. These elements were likely either being absorbed into the worms’ bodies or released to the surrounding waters.
Applications in Ancient Climate, Ocean Chemistry Studies
Further research may lead to a better understanding of how analyzing the chemical signature of these burrowing organisms may relate to ancient climate patterns and changes in ocean chemistry, Harazim said. “This technique allows you to study how the activity of burrowing organisms can influence the chemistry and composition of the rock they are living in. It helps us to better understand the geological record and helps us to read Earth’s geological past in a more sophisticated way,” he said.
He said there are plans for follow-up research with different types of fossilized samples to see if there are commonalities in their chemical concentration and distribution.
“There is still a lot to learn about how these organisms impact the porosity and geochemical composition of rocks, and how loose sediment becomes rock,” he said.
The work was supported by the American Association of Petroleum Geologists, the International Association of Sedimentologists, the Society for Sedimentary Geology, the Geological Society of America, the Natural Sciences and Engineering Research Council of Canada, and the Science and Technology Facilities Council.
Reference:
Dario Harazim, Duncan McIlroy, Nicholas P. Edwards, Roy A. Wogelius, Phillip L. Manning, Kristin M. Poduska, Graham D. Layne, Dimosthenis Sokaras, Roberto Alonso-Mori, Uwe Bergmann. Bioturbating animals control the mobility of redox-sensitive trace elements in organic-rich mudstone. Geology, 2015; G37025.1 DOI: 10.1130/G37025.1
Fossils in a flooded cave reveal the impact of human activities on biodiversity. A recent National Science Foundation grant will allow University of Florida researchers to excavate in more caves, including this one on Crooked Island in the Bahamas.
Nearly 100 fossil species pulled from a flooded cave in the Bahamas reveal a true story of persistence against all odds — at least until the time humans stepped foot on the islands.
University of Florida researchers say the discovery, detailed in a study appearing in the Proceedings of the National Academy of Sciences, shows many human activities pose a threat to the future of island biodiversity, with modern human-driven climate change not necessarily the most alarming. A new $375,000 National Science Foundation grant will allow further exploration of caves on Caribbean islands beginning in December.
Thirty-nine of the species discussed in the new study no longer exist on Great Abaco Island in the Bahamas. Of those, 17 species of birds likely fell victim to changes in climate and rising sea levels around the end of the Ice Age, about 10,000 years ago. Twenty-two other species of reptiles, birds and mammals persisted through those dramatic environmental changes only to vanish when humans first arrived on the island 1,000 years ago.
Exploring why some species were more flexible than others in the face of climate and human-driven changes could alter the way we think about conservation and restoration of species today, when scientists fear activities like habitat alteration and the introduction of invasive species could pose the greatest risk to island species, said lead author Dave Steadman, ornithology curator at the Florida Museum of Natural History on the UF campus.
“What we see today is just a small snapshot of how species have existed for millions of years,” Steadman said. “The species that existed on Abaco up until people arrived were survivors. They withstood a variety of environmental changes, but some could not adapt quickly or drastically enough to what happened when people showed up.
“So, there must be different mechanisms driving these two types of extinctions. What is it about people that so many island species could not adapt to? That’s what we want to find out.”
Steadman and colleagues, including plant ecologist Janet Franklin with Arizona State University, will attempt to answer that question later this year when they return to the Bahamas to further exploration of caves on Caribbean islands and expand our picture of which species were lost when humans arrived versus those that survived even though their environment was not always stable.
For species that were lost at the end of the Ice Age, climate change, habitat change and rising seas, with resulting smaller islands, may have caused their populations to become too small to remain genetically viable, resulting in inbreeding, Steadman said. A January 2015 study co-authored by Steadman found the Caribbean’s first humans depleted species as small as bats on Abaco. The new study shows several other species that endured until human arrival were lost to activities such as hunting and starting wildfires, he said.
Hayley Singleton, UF master’s student and study co-author, said the new research shows how quickly humans can drastically alter habitats. Unlike during the Ice Age, modern climate change and other human-driven changes often go hand in hand, she said.
“When humans change habitats at a rate that local species cannot keep up with, that can very quickly result in the losses,” Singleton said. “Likewise, even small climate changes can affect migration and significantly impact habitats. So, you can have the perfect storm where climate and human-driven changes are occurring at the same time, like we’re seeing in places around the world today.”
Future research will explore whether there are fundamental genetic differences between the Bahamian species that persisted and those that were lost when humans arrived. In other words, scientists want to know if there’s a genetic basis for adaptability, Steadman said.
“The answer could help us predict what animals will be affected most by a changing climate and humans,” he said.
The deformed lunar zircon at center was brought from the moon by Apollo astronauts. The fractures characteristic of meteorite impact are not seen in most lunar zircons, so the ages they record probably reflect heating by molten rock, not impact. Credit: Apollo 17/Nicholas E. Timms
Phenomenally durable crystals called zircons are used to date some of the earliest and most dramatic cataclysms of the solar system. One is the super-duty collision that ejected material from Earth to form the moon roughly 50 million years after Earth formed. Another is the late heavy bombardment, a wave of impacts that may have created hellish surface conditions on the young Earth, about 4 billion years ago.
Both events are widely accepted but unproven, so geoscientists are eager for more details and better dates. Many of those dates come from zircons retrieved from the moon during NASA’s Apollo voyages in the 1970s.
A study of zircons from a gigantic meteorite impact in South Africa, now online in the journal Geology, casts doubt on the methods used to date lunar impacts. The critical problem, says lead author Aaron Cavosie, a visiting professor of geoscience and member of the NASA Astrobiology Institute at the University of Wisconsin-Madison, is the fact that lunar zircons are “ex situ,” meaning removed from the rock in which they formed, which deprives geoscientists of corroborating evidence of impact.
“While zircon is one of the best isotopic clocks for dating many geological processes,” Cavosie says, “our results show that it is very challenging to use ex situ zircon to date a large impact of known age.”
Although many of their zircons show evidence of shock, “once separated from host rocks, ex situ shocked zircons lose critical contextual information,” Cavosie says.
The “clock” in a zircon occurs as lead isotopes accumulate during radioactive decay of uranium. With precise measurements of isotopes scientists can calculate, based on the half life of uranium, how long lead has been accumulating.
If all lead was driven off during asteroid impact, the clock was reset, and the amount of accumulated lead should record exactly how long ago the impact occurred.
Studies of lunar zircons have followed this procedure to produce dates from 4.3 billion to 3.9 billion years ago for the late heavy bombardment.
To evaluate the assumption of clock-resetting by impact, Cavosie and colleagues gathered zircons near Earth’s largest impact, located in South Africa and known to have occurred 2 billion years ago. The Vredefort impact structure is deeply eroded, and approximately 90 kilometers across, says Cavosie, who is also in the Department of Applied Geology at Curtin University in Perth, Australia. “The original size, estimated at 300 kilometers diameter, is modeled to result from an impactor 14 kilometers in diameter,” he says.
The researchers searched for features within the zircons that are considered evidence of impact, and concluded that most of the ages reflect when the zircons formed in magma. The zircons from South Africa are “out of place grains that contain definitive evidence of shock deformation from the Vredefort impact,” Cavosie says. “However, most of the shocked grains do not record the age of the impact but rather the age of the rocks they formed in, which are about 1 billion years older.”
The story is different on Earth, says zircon expert John Valley, a professor of geoscience at UW-Madison. “Most zircons on Earth are found in granite, and they formed in the same process that formed the granite. This has led people to assume that all the zircons were reset by impact, so the ages they get from the Moon are impact ages. Aaron is saying to know that, you have to apply strict criteria, and that’s not what people have been doing.”
The accuracy of zircon dating affects our view of Earth’s early history. The poorly understood late heavy bombardment, for example, likely influenced when life arose, so dating the bombardment topped a priority list of the National Academy of Sciences for lunar studies. Did the giant craters on the moon form during a brief wave or a steady rain of impacts? “It would be nice to know which,” Valley says.
“The question of what resets the zircon clock has always been very complicated. For a long time people have been saying if zircon is really involved in a major impact shock, its age will be reset, so you can date the impact. Aaron has been saying, ‘Yes, sometimes, but often what people see as a reset age may not really be reset.’ Zircons are the gift that keep on giving, and this will not change that, but we need to be a lot more careful in analyzing what that gift is telling us.”
This illustration provided by Brigham Young University on Oct. 16, 2015 depicts a pterosaur, which would have been the largest flying reptile of the time 210 million years ago, based on fossils found in 2009 at a site in Dinosaur National Monument near the town of Jensen in northeastern Utah. Its wingspan is about 1.3 meters (4.3 feet). The sphenosuchian depicted in its jaws is about 25 centimeters (10 inches) Paleontologists have discovered a cliff brimming with fossils that offers a rare glimpse of desert life in western North America early in the age of dinosaurs. Credit: Josh Cotton/Brigham Young University via AP
Paleontologists have discovered a cliff-side in Utah brimming with fossils that offers a rare glimpse of desert life in western North America early in the age of dinosaurs.
Among the discoveries in what used to be a lake shoreline between giant sand dunes is a new pterosaur that would have been the largest flying reptile of the time. It wielded its ferocious teeth and powerful skull to gobble up small crocodile type creatures as it soared over a desert some 210 million years ago.
“If you saw one of these things coming at you with its jaws open, it would freak you out of your mind,” said Brooks Britt, a Brigham Young University paleontologist who presented preliminary findings this week at the Society of Vertebrate Paleontology conference in Dallas.
He and fellow paleontologists plan to publish the findings in scientific journal next year. Eight different animals, most likely new, have been identified at a site discovered in 2009 near Dinosaur National Monument on the Utah-Colorado border. The discoveries include:
— A type of a strange-looking reptile with a head like a bird, arms like a mole and a claw on the tip of the tail called a drepanosaur.
— Several small crocodile-like creatures with armor on their backs called sphenosuchians.
— Two different types of meat-eating dinosaurs, one related to the coelophysis, a scrawny dinosaur featured in the recent movie, “Walking with Dinosaurs.”
“It’s a fantastic site,” said Brian Andres, a University of South Florida paleontologist who heard the presentation this week. “It’s in a time and a place that we really do not have a good record of.”
The pterosaur discovery is significant because it fills a gap in the fossil record between earlier, smaller pterosaurs and the giant ones that came later, Andres said.
It is related to another wicked-jawed pterosaur discovered in England: the Dimorphodon.
Each side of its lower jaw had two fangs and 28 teeth. “This thing is built like an aerial predator,” Andres said.
The skull and wing bone found are also noteworthy because they are intact, and not crushed, a rarity for pterosaurs. It is the first known Triassic pterosaur found in North America, other than one unearthed in Greenland, Britt said.
“It is absurdly rare to find delicate, small skeletons from anywhere in time, anywhere in the world,” said Adam Pritchard, a Yale paleontologist not part of the discovery team. “To have them from the Triassic period, which is the very beginning of the age of reptiles, is really unprecedented, especially in western north America.”
The site was discovered paleontologists Dan Chure of Dinosaur National Monument and George Englemann of the University of Nebraska. Chure said the duo realized right away they had stumbled upon the discovery of their lives.
So far, they’ve found 11,500 bones—and they may be only halfway through getting them all out, he said. The new pterosaur, yet to be named, was found last year by a college student carefully extracting fossils from a 300-pound block of sandstone from the site.
“This is the best stuff I’ll ever see in my life,” said Britts, 60, who has been collecting dinosaur fossils for five decades. “It’s like Christmas every day.”
The site has been named “Saints and Sinners,” a playful nod to the collaboration between Britt, a member of The Church of Jesus Christ of Latter-day Saints, and non-Mormons Chure and Englemann.
“I’m not sure we would exactly consider ourselves sinners, but it had a nice ring to it,” Chure said.
At the terminus of Yahtse Glacier, Alaska, brown, sediment-laden water from the glacier bed appears at the sea surface and mixes with the blue-green seawater. Here, and elsewhere in Alaska and Greenland, observations of background seismic noise reveal for the first time how the flux of subglacial discharge varies over time. Credit: Timothy Bartholomaus
Tidewater glaciers flow from frigid mountains and ice sheet interiors down through ice-carved valleys and terminate in the sea, within fjords. Beneath the glaciers, liquid water streams toward the ocean, where it can drive melting at the terminus of the ice sheet and promote sea level rise. But terminus melting is poorly understood because it is difficult to measure the timing and amount of subglacial water release. Now, Bartholomaus et al. have shown that seismic signals can reveal variations in water discharge and answer long-standing questions about glacier behavior.
Subglacial discharge starts out at the upstream surface of a glacier in the form of melted ice and rainfall. It flows down through icy channels to the glacial bed, where it affects glacier speed and bed erosion, before it emerges at the end of the glacier.
Discharge can vary hour to hour, day to day, and season to season. Since 1979, scientists have hypothesized that subglacial discharge events cause distinct seismic rumbles, but few have put this prediction to the test.
Over the course of one summer, the authors collected data from a seismometer located on land near the end of Alaska’s Mendenhall Glacier, which terminates in a lake. When they compared the amount of water discharge measured at the terminal lake with the strength of seismic background noise, they found that the two quantities, discharge and seismic noise, matched closely.
The relationship between water discharge and tremor also held true for Yahtse Glacier, another Alaskan glacier. There, the scientists used nine seismometers and a weather station to measure seismic tremor and discharge from 2009 to 2011. The results confirmed that seismic tremor can be used as a proxy for discharge timing and rates. Seismic tremor patterns were also detected at one other Alaskan glacier and at a glacier in Greenland.
The scientists didn’t just confirm that seismic tremor mirrors discharge; they also showed how it can be used to better understand glaciers. Data showing heavy summer discharge allowed them to discard a 1987 hypothesis that in the summer, fast ice flow would disrupt water channels melted into the sole of the glacier.
Reference:
Timothy C. Bartholomaus, Jason M. Amundson, Jacob I. Walter, Shad O’Neel, Michael E. West, Christopher F. Larsen. Subglacial discharge at tidewater glaciers revealed by seismic tremor. DOI: 10.1002/2015GL064590
Note: The above post is reprinted from materials provided by American Geophysical Union. The original article was written by Sarah Stanley, Freelance Writer.
A large clutch of titanosaur eggs has been cleaned for research. Credit: Luis Chiappe, LA County Natural History Museum
Researchers know dinosaurs once ruled the earth, but they know very little about how these animals performed the basic task of balancing their energy intake and output–how their metabolisms worked. Now, a team of Caltech researchers that has measured the body temperatures of a wide range of dinosaurs has provided insight into how the animals may have regulated their internal heat.
The study was led by John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry, and Rob Eagle, a former Caltech postdoctoral scholar now at UCLA. A paper describing the research appears in the October 13 issue of the journal Nature Communications.
The current study examined eggshells from the sauropods, a group that includes some of the biggest dinosaurs ever to live, called Titanosaurs, as well as eggshells of birdlike and approximately human-sized oviraptorid dinosaurs. The eggshells were analyzed to determine the extent to which carbon-13 and oxygen-18–rare, naturally occurring isotopes (variant forms of elements that differ in number of neutrons)–group together in the mineral structure. This “clumping” of rare isotopes previously has been shown to depend on mineral growth temperature. The eggshell data were compared with the results of a previous study by this same group that used similar techniques to examine the growth temperatures of the sauropod dinosaurs, including the giraffe-like Giraffatitan and a giant herbivore known as Camarasaurus.
The isotopic composition of the eggshells showed that smaller oviraptorid dinosaurs had body temperatures of 32 degrees Celsius–decidedly cooler than modern mammals and birds. The body temperatures of the larger Titanosaur dinosaurs were 38 degrees Celsius, indistinguishable from a previous finding for Giraffatitan teeth and similar to modern mammals. This finding–that larger dinosaurs maintained body temperatures like ours whereas smaller ones more closely resembled modern reptiles–has implications for our understanding of dinosaur physiology.
Modern mammals are described as warm blooded if they regulate their own temperature, as if tweaking an internal thermostat. In a process called endothermy, warm-blooded mammals utilize the heat generated by their own internal functions instead of drawing ambient heat from the environment, which is what a cold-blooded snake or lizard does by basking in the sun. Endothermy is relatively similar across many different sizes of mammals, from mice to humans to whales.
“Measuring cooler temperatures in small dinosaurs is the first evidence to suggest that at least some of them had lower basal metabolisms than most modern mammals and birds, and therefore the emergence of modern mechanisms of endothermy hadn’t occurred in these dinosaurs,” Eiler says.
The picture is not so clear for the larger dinosaurs that were studied. Although Eiler and his colleagues found that they had warm body temperatures similar to modern mammals, it is not known if the animals actually had endothermic metabolisms or if they were warm simply because of their enormous sizes–a phenomenon known as gigantothermy. Gigantotherms have small surface areas relative to their large volumes and thus have less area through which they can lose heat. Therefore, the heat is trapped internally. “If you weigh 80 tons, your problem is not staying warm–it’s trying not to burst into flames,” Eiler says.
The wide range of warm temperatures discovered among the various dinosaur species examined in the study suggests that “either they had a range of different metabolic strategies, or they all had low basal metabolisms, and the large ones were only warm due to gigantothermy,” Eiler says.
The technique used to determine these animal body temperatures was first conceived and used by Eiler’s group in 2011 on dinosaur tooth fossils and is related to methods they previously developed for nonbiological minerals and molecules. The method, called the clumped-isotope technique, relies on measurements of rare isotopes in bioapatite, or biologically grown calcium carbonate, a mineral present in bones, teeth, eggshells, and other fossils. In 2006, Eiler’s lab quantified the degree to which carbon-13 and carbon-18 clump together to varying degrees in a biomineral, depending on the temperature at the time the mineral formed; this relationship subsequently was examined for many mineral types by Eiler’s group at Caltech and at other laboratories.
“There’s this cool idea that if I had a fossil skeleton, I could map the body temperature of the entire creature and come up with a physiological model of how it redistributed heat within its body,” Eiler says. “There’s no reason you couldn’t do that, except that bone isn’t very well preserved.”
The team’s next step is to compare fossils from the same species across stages of maturation. “It may be that some dinosaurs have a different metabolic strategy at different phases of life,” Eiler says.
Reference:
Robert A. Eagle, Marcus Enriquez, Gerald Grellet-Tinner, Alberto Pérez-Huerta, David Hu, Thomas Tütken, Shaena Montanari, Sean J. Loyd, Pedro Ramirez, Aradhna K. Tripati, Matthew J. Kohn, Thure E. Cerling, Luis M. Chiappe & John M. Eiler. Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs. DOI:10.1038/ncomms9296
Volcanic processes touched off by a massive impact appear to have created Mafic Mound, a strange feature near the Moon’s south pole. Credit: NASA/Goddard/Arizona State University
A giant mound near the Moon’s south pole appears to be a volcanic structure unlike any other found on the lunar surface, according to new research by Brown University geologists.
The formation, known as Mafic Mound, stands about 800 meters tall and 75 kilometers across, smack in the middle of a giant impact crater known as the South Pole-Aitken Basin. This new study suggests that the mound is the result of a unique kind of volcanic activity set in motion by the colossal impact that formed the basin.
“If the scenarios that we lay out for its formation are correct, it could represent a totally new volcanic process that’s never been seen before,” said Daniel Moriarty, a Ph.D. student in Brown’s Department of Earth, Environmental and Planetary Sciences and the study’s lead author.
The research has been accepted for publication in Geophysical Research Letters, a publication of the American Geophysical Union, and is available online.
Mafic Mound (mafic is a term for rocks rich in minerals such as pyroxene and olivine) was first discovered in the 1990s by Carle Pieters, a planetary geologist at Brown and Moriarty’s adviser. What makes it curious, other than its substantial size, is the fact that it has a different mineralogical composition than the surrounding rock. The mound is rich in high-calcium pyroxene, whereas the surrounding rock is low-calcium.
“This unusual structure at the very center of the basin begs the question: What is this thing, and might it be related to the basin formation process?” Moriarty said.
A volcanic structure A topographic view of the South Pole-Aitken Basin. Reds are high; blues are low. Mafic Mound, (the reddish area in the center) stands 800 meters above the surrounding surface. Credit: NASA/Goddard/MIT/Brown
To investigate that, Moriarty and Pieters looked at a rich suite of data from multiple lunar exploration missions. They used detailed mineralogical data from the Moon Mineralogy Mapper, which flew aboard India’s Chandrayaan-1 spacecraft. NASA’s Lunar Orbiter Laser Altimeter provided precise topographic data, and data from the GRAIL mission characterized gravitational anomalies in the region.
Those combined datasets suggested that Mafic Mound was created by one of two unique volcanic processes set in motion by the giant South Pole-Aitken impact. An impact of that size would have created a cauldron of melted rock as much as 50 kilometers deep, some researchers think. As that sheet of impact melt cooled and crystalized, it would have shrunk. As it did, still-molten material in the middle of the melt sheet may have been squeezed out the top like toothpaste from a tube. Eventually, that erupted material may have formed the mound.
Such a process could explain the mound’s strange mineralogy. Models of how the South Pole-Aitken melt sheet may have crystalized suggest that the erupting material should be rich in high-calcium pyroxene, which is consistent with the observed mineralogy of the mound.
Another scenario that fits the data involves possible melting of the Moon’s mantle shortly after the South Pole-Aitken impact. The impact would have blasted tons of rock out of the basin, creating a low-gravity region. The lower gravity condition could have enabled the center of the basin to rebound upward. Such upward movement would have caused partial melting of mantle material, which could have erupted to form the mound.
These scenarios make for a strong fit to those very detailed datasets, Moriarty said. And if either is true, it would represent a unique process on lunar surface. Moriarty said a sample return mission to the South Pole Aitken Basin would be a great way to try to verify the results. The basin has long been an interesting mission target for lunar scientists.
“It’s the largest confirmed impact structure in the solar system and has shaped many aspects of the evolution of the Moon,” Moriarty said. “So a big topic in lunar science is studying this basin and the effects it had on the geology of the Moon through time.”
A sample return mission to the basin could bring back bits of lunar mantle, the composition of which is still not fully understood. A returned sample could also put a firm date on when the impact occurred, which could be used as a standard to date other features on the surface.
And in light of this work, a sample could also help to shed light on a unique lunar volcanic process.
Reference:
Daniel P. Moriarty III and Carle M. Pieters. The nature and origin of Mafic Mound in the South Pole-Aitken Basin. DOI: 10.1002/2015GL065718
Assorted pieces of juvenile mammoth tusks used in an ongoing study of Siberian woolly mammoth weaning ages. A longitudinal cross-section, foreground, several tusk segments used for isotope sampling, and a small tusk cut in half for CT scanning, background. Credit: Image courtesy of University of Michigan
Chemical clues about weaning age embedded in the tusks of juvenile Siberian woolly mammoths suggest that hunting, rather than climate change, was the primary cause of the elephant-like animal’s extinction.
Woolly mammoths disappeared from Siberia and North America about 10,000 years ago, along with other giant mammals that went extinct at the end of the last glacial period. Current competing hypotheses for the mammoth’s extinction point to human hunting or climate change, possibly combining in a deadly one-two punch.
Despite decades of study, the issue remains unresolved and hotly debated. But two University of Michigan paleontologists may have found an ingenious way around the logjam.
U-M doctoral student Michael Cherney and his adviser, Museum of Paleontology Director Daniel Fisher, say an isotopic signature in 15 tusks from juvenile Siberian woolly mammoths suggests that the weaning age, which is the time when a calf stops nursing, decreased by about three years over a span of roughly 30,000 years leading up to the woolly mammoth’s extinction.
Climate-related nutritional stress is associated with delayed weaning in modern elephants, while hunting pressure is known to accelerate maturation in animals and would likely result in earlier weaning, according to Cherney and Fisher.
“This shift to earlier weaning age in the time leading up to woolly mammoth extinction provides compelling evidence of hunting pressure and adds to a growing body of life-history data that are inconsistent with the idea that climate changes drove the extinctions of many large ice-age mammals,” said Cherney, who is conducting the work for his doctoral dissertation in the U-M Department of Earth and Environmental Sciences.
“These findings will not end the debate, but we hope they will show people the promise of a new approach toward solving a question that, so far, has just led to divided camps,” said Cherney, who is scheduled to present his findings Oct. 15 at a meeting of the Society of Vertebrate Paleontology in Dallas.
The study was made possible by the extensive collection of Siberian mammoth tusks that Fisher has amassed over the past 20 years. The specimens–collected and exported under permits from the Russian government with the help of colleagues in Russia, France and the Netherlands–include about three dozen juvenile tusks.
“We have known for about a decade that valuable information about weaning age could be extracted from these tusks,” said Fisher, a professor in the Department of Earth and Environmental Sciences and the Department of Ecology and Evolutionary Biology. Fisher also led the team that recovered the partial remains of a mammoth this month near Chelsea, Mich.
“But this is the first time we’ve had data from enough individuals, and covering a wide enough range of geologic ages, to show a pattern through time,” Fisher said. “This is a milestone in the development of our approach, and it shows that the extinction problem is solvable.”
Fifteen tusks from individuals ranging in age from 3 to 12 were analyzed. The 3-year-old’s tusk is about 10 inches long, while the 12-year-old’s tusk is about 30 inches long.
As part of the study, Cherney measured the isotopic composition of tail hairs from a mother-calf pair of African elephants at the Toledo Zoo. The elephant calf was in the process of being weaned from mother’s milk, which enabled Cherney to observe the isotopic effects of nursing and the long transition to a fully solid diet for a close relative of mammoths.
Cherney compared the ratio of the two stable isotopes of nitrogen, nitrogen-14 and nitrogen-15, from proteins in elephant tail hairs. He found that as the proportion of solid food in the elephant calf’s diet increased, the ratio of nitrogen-15 to nitrogen-14 steadily dropped. This pattern had been previously documented in other mammals, including humans, but never in elephants.
Armed with this isotopic weaning signature, he then turned to the mammoth tusks. CT scans enabled Cherney to identify annual growth increments–which resemble a tree’s annual growth rings–in the tusks. Samples for each year of growth were collected, and nitrogen isotopes from collagen proteins were measured.
The isotopic ratios from the calves’ early years of life consistently displayed a trend toward lower nitrogen-15 values, reflecting the decreased contribution of milk to the overall diet, Cherney said.
“It was the same pattern we saw in the Toledo Zoo elephant calf,” he said.
The gradual decrease in nitrogen-15 was followed, in most cases, by an abrupt increase that Cherney and Fisher interpret as a sign of short-term nutritional stress during the first year after being fully weaned.
Radiocarbon dating of the 15 Siberian tusks showed they span the period from about 40,000 years ago to about 10,000 years ago.
Cherney and Fisher showed that over the span of 30,000 years, the average weaning age decreased from age 8 to age 5.
The current weaning study is part of a much larger, decades-long effort by Fisher and a series of graduate students to extract “life history” information preserved in fossil tusks. Biologists use the term life history to refer to the full range of changes an organism experiences in the course of its growth and development.
“I started studying tusks 30 years ago and realized early on that life histories are the key,” Fisher said. “Nobody else has used tusks, which are after all a record of life and growth, as a source of data in this way.”
Over the years, Fisher and his students have shown that mammoth tusks hold life-history information about growth rates, age of sexual maturation, spacing of pregnancies, and weaning.
Because the timing of those life-history milestones can be affected by various environmental pressures, the tusks provide a way to “look directly at how the animals themselves were impacted by, and responded to, changes in their environment,” Cherney said.
Often, environmental changes have predictable effects on life histories. By analyzing evidence from mammoth tusks, Fisher and his students can test those predictions.
“The strength of life-history analyses for resolving the extinction debate rests in the knowledge that the age of final weaning is a life-history landmark that is expected to change differently in response to predation and climate-related nutritional stress,” said Cherney, who will speak during the Romer Prize Session at the paleontology meeting. “Our analysis sets up a test of competing hypotheses, and our preliminary results are consistent with expectations under hunting pressure.”
The work was funded in part by grants from the National Science Foundation, the National Geographic Society and CRDF Global. Cherney and Fisher plan to submit their findings for publication in a scientific journal.
Video
Chemical clues about weaning age embedded in the tusks of juvenile Siberian woolly mammoths suggest that hunting, rather than climate change, was the primary cause of the elephant-like animal’s extinction.
The texture of the ocean floor is determined by the enormous stretching and cracking that takes place at the mid-ocean ridge, where tectonic plates are pulling apart and magma is rising to form new sea floor. On either side of the ridge, rows of abyssal hills form and then move away as the plates pull apart over time. Exactly how those forces combine to influence the size and shape of the hills, however, hasn’t been entirely clear.
A provocative study released earlier this year suggested that climate change may play a role – it attributed the frequency of the abyssal hills to the amount of magma rising, magma that a concurrent study showed is sensitive to changing pressure on the ocean floor as sea level rises and falls during warm periods and ice ages.
The idea that we might be able to read climate history in the sea floor is exciting, but while rising magma likely is modulated by changes in sea level, the claim that climate determines abyssal hill spacing doesn’t match observations from all the world’s oceans, say the authors of a new paper published in this week’s journal Science.
Jean-Arthur Olive, the lead author of the new study and a post-doctoral research scientist at Lamont-Doherty Earth Observatory, and his co-authors argue that the fabric of the sea floor is better explained by faults that form, offsetting the crust as the plates pull apart. The authors combined sea floor observations with recently developed models of mid-ocean ridge dynamics to test the climate theory from several angles and found that even large fluctuations in melt supply at the height of ice ages and warm periods didn’t affect the fault process shaping the sea floor. Physical signals of the changing pressure of rising and falling sea level on the ocean floor may still be present, but those signals are more likely to be picked up in the thickness of the plate, the authors say.
The new paper is the first to explain the characteristic spacing of abyssal hills quantitatively as a function of seafloor spreading rate within a single theoretical framework. That texture matters because it influences ocean currents, which influence how ocean water mixes and flows.
The Snickers Bar Experiment
To visualize what happens at the mid-ocean ridge, try this experiment, a favorite of Lamont-Doherty geophysicist and research professor Roger Buck, a co-author of the new paper.
Take a Snickers bar with both hands and try to pull it apart. You’ll see that the hardened outer shell of chocolate cracks, while the gooey middle stretches. As you pull on the candy bar, stress builds up and the chocolate shell weakens, finally cracking at the weakest points. If you were to inject molten chocolate between the gooey center and the outer shell – simulating magma at the mid-ocean ridges – the molten chocolate would flow into those cracks as soon as they formed, reducing the stress.
“We’re arguing that it’s pretty much the same process,” Olive said. “You’re adding melt from below. If you don’t have a lot of melt being supplied to the ridge, you’ll see lots of faults.” The big faults develop and grow and move to the side with the spreading of the plates while melted mantle intrudes. At some point, too much energy is required for the faults to continue to grow continue, a new fault forms near the ridge, and a new hill is created.
Atlantic Hills vs. Pacific Hills
The visual difference in the spacing and size of abyssal hills along the Atlantic and Pacific mid-ocean ridges first raised questions in the authors’ minds about the climate paper.
At the Mid-Atlantic Ridge, where less magma is produced, you’ll see large hills on either side of the ridge with sharp scarps where faults opened up and slipped to release stress. They can be 5 to 10 kilometers apart and look much like a row of books that has tipped over on a shelf, Olive says.
At the East Pacific Rise, where more magma is flowing and the plates are pulling apart faster, the hills are smaller, as little as 2 kilometers apart, and the sea floor is smoother. If past climate cycles had influenced the spacing of the hills, the faster spreading in the Pacific should have meant hills farther apart, Olive said.
Lamont-Doherty scientists have been involved in research into plate tectonics and other processes at mid-ocean ridges since the 1950s, when Marie Tharp used seismic data collected from ships to develop the first complete map of the ocean floor. She found distinct ridges through the oceans that were symmetric on each side. Sediment eventually smooths the floor farther from the ridge, but close to each mid-ocean ridge the roughness of the abyssal hills is clear.
Reference:
Maya Tolstoy. Mid-ocean ridge eruptions as a climate valve, Geophysical Research Letters (2015). DOI: 10.1002/2014GL063015
J. W. Crowley et al. Glacial cycles drive variations in the production of oceanic crust, Science (2015). DOI: 10.1126/science.1261508
A view of Antoliñako Koba site (Gautegiz-Arteaga, Bizkaia, Basque Country, Spain) during the excavation. Credit: Mikel Aguirre.
By combining three important palaeoclimatic records (small vertebrates, marine microfauna and stable isotopes of herbivores), a multidisciplinary team of the UPV/EHU has reconstructed past environments with the best resolution ever achieved. The study, led by Juan Rofes, currently a researcher at the Musèum National d’Histoire Naturelle, CNRS, Paris, has been published in the prestigious British Scientific Reports, which is one of the Nature group journals.
This group of archaeologists, palaeontologists, geologists, geochemists and palaeo-oceanographers has for the first time reconstructed the environment covering a period of nearly 35,000 years of the Cantabrian Region during the Upper Pleistocene. To do this, they have combined three palaeoclimatic records: marine microfauna, small vertebrates and stable isotopes of herbivores. The latter two records come from the Antoliñako Koba site (Gautegiz-Arteaga, Bizkaia, Basque Country, Spain), an exceptional archaeological deposit containing a long chrono-cultural sequence of nine levels, ranging from the Aurignacian and going right up to the Epipalaeolithic. This site was excavated and processed over a 20-year period by the archaeologist Mikel Aguirre (UNED-Open University), who is also a member of the multidisciplinary team.
“The two principal merits of the study are, firstly, having compared the continental and marine records of the same region, filling the gaps that existed in the terrestrial sequence by using the marine record, which tends to be more complete; and, secondly, having produced a continuous palaeo-environmental reconstruction of the period between 44 and 9 million years before present in the Cantabrian Region”, explained archaeozoologist and palaeontologist Juan Rofes. The article has been published by the journal Scientific Reports, which, owing to its high impact index (WOS 2014: 5.58), is the fifth most important multidisciplinary publication in the world.
Specifically, the changes in the communities of microvertebrates (mammals, amphibians and reptiles) and the stable isotope data (carbon and nitrogen) obtained from the bone collagen of deer in the continental site, have been compared with marine microfaunal evidence (foraminifera, planktonic and benthic species, ostracods and oxygen isotopes) gathered in the south of the Bay of Biscay by Dr Blanca Martínez-García (UPV/EHU). The sequence at the Antoliñako Koba site was dated by means of radiocarbon, which made it possible to compare the various signs with each other, and also with other known environmental records of the North Atlantic (sedimentary and pollen phases of the Cantabrian Region, variations in the sea level and ice cores made to the north of Greenland).
The research confirms a series of warm and cold events in the Cantabrian Region, which to a greater or lesser extent coincide with the climate evolution in the northern hemisphere during the Upper Pleistocene. “The contribution of this exhaustive palaeo-environmental reconstruction to regional and continental prehistory is unquestionable, since it enables us to get to know the climatic and environmental framework in which human groups in the past moved and which determined many of their strategies to adapt and survive. What is more, at this time of climate change increased by human pressure, it is a good idea to look at the past in order to learn lessons for the future,” explained Rofes. The study came about during the postdoctoral training period that Juan Rofes (Lima, Peru, 1974), PhD holder of the University of Zaragoza, spent at the UPV/EHU’s Faculty of Science and Technology. Today, he is on a European Union post-doctoral Marie Curie contract at the Musèum National d’Histoire Naturelle, CNRS, Paris.
Reference:
Rofes, J., Garcia-Ibaibarriaga, N., Aguirre, M., Martínez-García, B., Ortega, L., Zuluaga, M.C., Bailon, S., Alonso-Olazabal, A., Castaños, J. & Murelaga, X. Combining Small-Vertebrate, Marine and Stable-Isotope Data to Reconstruct Past Environments. Scientific Reports 5, 14219; DOI: 10.1038/srep14219 (2015).
Perinatal specimens of Saurolophus angustirostris (MPC-D100/764). Bones on the right side of the block show a certain degree of articulation, whereas bones on the left are disarticulated. Credit: Dewaele et al.. Perinatal Specimens of Saurolophus angustirostris (Dinosauria: Hadrosauridae), from the Upper Cretaceous of Mongolia. PLoS ONE, 2015; 10 (10): e0138806
Scientists describe a perinatal group of Saurolophus angustirostris, a giant hadrosaur dinosaur, all likely from the same nest, found at “Dragon’s Tomb” in Mongolia, according to a study published October 14, 2015 in the open-access journal PLOS ONE by Leonard Dewaele from Ghent University and the Royal Belgian Institute of Natural Sciences, Belgium and colleagues.
Discovered in an area called the “Dragon’s Tomb,” a famous location for finding Late Cretaceous dinosaur fossils in the Gobi Desert, Mongolia, the authors of this study described three or four perinatal specimens or “babies” and two associated eggshell fragments. The young dinosaurs were likely part of a nest originally located on a river sandbank, and the authors suggest they are likely Saurolophus angustirostris (meaning ‘lizard crest’), a dinosaur that is known from multiple well-preserved complete skeletons.
The skull length of these Saurolophus was around 5% that of the largest known S. angustirostris specimens, indicating that these specimens were in the earliest development stages. The perinatal bones already resembled S. angustirostris characteristics, including the upwardly directed snout (the premaxillary bones). The specimens did not yet have the characteristic cranial crest at the top of the head and areas of the skull-the cervical neural arches-were not yet fused, which suggest they may be in the earliest stages of the development of S. angustirostris.
Leonard Dewaele notes, “The poorly developed crest in Saurolophus babies provides evidence of ontogenetic crest growth within the Saurolophini tribe. The Saurolophini are the only Saurolophinae to bear supra cranial crests as adults.”
Scientists can’t tell whether the individuals were still in the eggs or had just hatched when they died, but they were apparently already dead and partly decomposed when they were buried by river sediment during the wet summer season. The fossilized eggshell fragments associated with the perinatal individuals closely resemble those found from S. angustirostris relatives in Mongolia, and scientists suggest these specimens may bridge a gap in our knowledge of the development of S. angustirostris.
Reference:
Dewaele L, Tsogtbaatar K, Barsbold R, Garcia G, Stein K, Escuillié F, et al. Perinatal Specimens of Saurolophus angustirostris (Dinosauria: Hadrosauridae), from the Upper Cretaceous of Mongolia. PLoS ONE, 2015; 10 (10): e0138806 DOI: 10.1371/journal.pone.0138806
Note: The above post is reprinted from materials provided by PLOS.
