Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia.
A pair of researchers, Pascal Audet and Roland Burgmann of the Universities of Ottawa and California, respectively, has found a connection between the amount of silica rich quartz above subduction zones and the frequency rate of “slow” earthquakes. In their paper published in the journal Nature, the two describe how they measured quartz amounts in the Cascadia subduction zone using seismic waves, and how it relates to slow earthquakes.
Scientists have only known about slow earthquakes for a few years—since they can’t be felt, there was no real indication that they were occurring. They happen when silica rich sediment is pushed from below when one plate pushes beneath another. The fluid is trapped causing pressure to build—eventually that pressure is released by slow sliding (due to lubrication provided by the silica), rather than the jolt associated with surface quakes. After the sliding stops, the pressure begins to build up again and the whole process is repeated. Such quakes can occur over days or even weeks, releasing energy equivalent to large surface quakes. Scientists now know that such quakes occur off the coast of Japan, New Zealand, the United States and Canada, but, they all have a different frequency rate. They happen every two years in New Zealand, every six months in Japan and every 14 months beneath Canada’s Vancouver Island. The difference in rates, the researchers have found, is due to the amount of silica in the fluid—there more there is, the faster faults knit together after the sliding has stopped.
The pair of researchers note that much more study needs to be done before it can be determined if slow earthquakes can be used to help predict surface quakes. In their experiments, they found the crust to be 5 to 15 percent quartz above the plates in the Cascadia subduction zone, an area that experienced a magnitude 9 quake in 1700. Scientists believe a major quake will likely occur again there sometime over the next 200 years. If slow earthquakes are found to portend larger ones, perhaps enough warning time can be given to save lives in the heavily populated area.
More information:
Possible control of subduction zone slow-earthquake periodicity by silica enrichment, Nature 510, 389–392 (19 June 2014) DOI: 10.1038/nature13391
Abstract
Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution–precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening15 caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour.
Miriam Reichel’s research shows that the T. rex’s front teeth gripped and pulled, while the teeth along the side of the jaw punctured and tore flesh. Credit: Image courtesy of University of Alberta
One of the most prominent features of life-size models of Tyrannosaurus rex is its fearsome array of flesh-ripping, bone-crushing teeth.
Until recently, most researchers who studied the carnivore’s smile only noted the varying sizes of its teeth. But University of Alberta paleontologist Miriam Reichel discovered that beyond the obvious size difference in each tooth family in T. rex’s gaping jaw, there is considerable variation in the serrated edges of the teeth.
“The varying edges, or keels, not only enabled T. rex’s very strong teeth to cut through flesh and bone,” says Reichel, “the placement and angle of the teeth also directed food into its mouth.”
Reichel analyzed the teeth of the entire tyrannosaurid family of meat-eating dinosaurs and found T. rex had the greatest variation in tooth morphology or structure. The dental specialization was a great benefit for a dinosaur whose preoccupation was ripping other dinosaurs apart.
Reichel’s research shows that the T. rex’s front teeth gripped and pulled, while the teeth along the side of the jaw punctured and tore flesh. The teeth at the back of the mouth did double duty: not only could they slice and dice chunks of prey, they forced food to the back of the throat.
Reichel says her findings add strength to the classification of tyrannosaurids as heterodont animals, which are animals with teeth adapted for different functions depending on their position in the mouth.
One surprising aspect of T. rex teeth, common to all tyrannosaurid’s, is that they weren’t sharp and dagger-like. “They were fairly dull and wide, almost like bananas,” said Reichel. “If the teeth were flat, knife-like and sharp, they could have snapped if the prey struggled violently when T. rex’s jaws first clamped down.”
Reichel’s research was published in The Canadian Journal of Earth Science.
Journal Reference:
Miriam Reichel, Hans-Dieter Sues. The variation of angles between anterior and posterior carinae of tyrannosaurid teeth. Canadian Journal of Earth Sciences, 2012; 49 (3): 477 DOI: 10.1139/e11-068
Note : The above story is based on materials provided by University of Alberta.
Chemical Formula: Cu2(AsO4)(OH) Locality: Carharrack mine, Gwennap, Cornwall, England, GB Name Origin: From the German olivernerz, literally “olive” ore, in allusion to its typical color.
Olivenite is a copper arsenate mineral, formula Cu2(AsO4)(OH). It crystallizes in the monoclinic system (pseudo-orthorhombic), and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. More commonly, it occurs as globular aggregates of acicular crystals, these fibrous forms often having a velvety lustre; sometimes it is lamellar in structure, or soft and earthy.
A characteristic feature, and one to which the name alludes (German, Olivenerz, of A. G. Werner, 1789), is the olive-green color, which varies in shade from blackish-green in the crystals to almost white in the finely fibrous variety known as woodcopper. The hardness is 3, and the specific gravity is 4.3. The mineral was formerly found in some abundance, associated with limonite and quartz, in the upper workings in the copper mines of the St Day district in Cornwall; also near Redruth, and in the Tintic Mining District in Utah. It is a mineral of secondary origin, a result of the oxidation of copper ores and arsenopyrite.
The arsenic of olivenite is sometimes partly replaced by a small amount of phosphorus, and in the species libethenite we have the corresponding copper phosphate Cu2PO4OH. This is found as small dark green crystals resembling olivenite at Libethen in the Slovak Republic, and in small amount also in Cornwall. Other members of this isomorphous group of minerals are adamite, Zn2(AsO4)(OH), and eveite, Mn2(AsO4)(OH).
History
Discovery date : 1820 Town of Origin: CORNOUAILLES Country of Origin: ANGLETERRE
Physical Properties
Hardness: 3,00 Density: from 4,37 to 4,38 Color : olive-green; greenish brown; yellow; grayish green; yellowish white; blackish green; brown; grayish white Luster: vitreous;silky; greasy Streak : green yellow; white Break: irregular; conchoidal Cleavage: {110} Indistinct, {010} Indistinct, {110} Indistinct
Photos:
OLIVENITE Wheal Phoenix, Linkinhorne, Liskeard, Cornwall, England, Europe Size: 6.5 x 6 x 3 cm (Small Cabinet) Owner: Crystal ClassicsOlivenite Inubia mine, Bahia, Brazil Specimen weight:76 gr. Crystal size:3 mm Overall size: 72mm x 60 mm x 30 mm minserviceOlivenite Mine du Cap Garonne, Pradet, Var, Provence-Alpes-Côte d’Azur, France Specimen weight:18 gr. Crystal size:0,15 cm Overall size:4 x 3,7 x 1,3 cm minserviceOLIVENITE on CORNWALLITE Wheal Phoenix, Linkinhorne, Liskeard, Cornwall, England, Europe Size: 5 x 3 x 2.5 cm (Small Cabinet) Owner: Crystal Classics
Mount St. Helens as it appeared two years after its catastrophic eruption on May 18, 1980. Credit: U.S. Geological Survey
University and government scientists are embarking on a collaborative research expedition to improve volcanic eruption forecasting by learning more about how a deep-underground feeder system creates and supplies magma to Mount St. Helens.
They hope the research will produce science that will lead to better understanding of eruptions, which in turn could lead to greater public safety.
The Imaging Magma Under St. Helens project involves three distinct components: active-source seismic monitoring, passive-source seismic monitoring and magnetotelluric monitoring, using fluctuations in Earth’s electromagnetic field to produce images of structures beneath the surface.
Researchers are beginning passive-source and magnetotelluric monitoring, while active-source monitoring – measuring seismic waves generated by underground detonations – will be conducted later.
Passive-source monitoring involves burying seismometers at 70 different sites throughout a 60-by-60-mile area centered on Mount St. Helens in southwestern Washington. The seismometers will record data from a variety of seismic events.
“We will record local earthquakes, as well as distant earthquakes. Patterns in the earthquake signatures will reveal in greater detail the geological structures beneath St. Helens,” said John Vidale, director of the University of Washington-based Pacific Northwest Seismic Network.
Magnetotelluric monitoring will be done at 150 sites spread over an area running 125 miles north to south and 110 miles east to west, which includes both Mount Rainier and Mount Adams. Most of the sites will only be used for a day, with instruments recording electric and magnetic field signals that will produce images of subsurface structures.
Besides the UW, collaborating institutions are Oregon State University, Lamont-Doherty Earth Observatory at Columbia University, Rice University, Columbia University, the U.S. Geological Survey and ETH-Zurich in Switzerland. The work is being funded by the National Science Foundation.
Mount St. Helens has been the most active volcano in the Cascade Range during the last 2,000 years and has erupted twice in the last 35 years. It also is more accessible than most volcanoes for people and equipment, making it a prime target for scientists trying to better understand how volcanoes get their supply of magma.
The magma that eventually comes to the surface probably originates 60 to 70 miles deep beneath St. Helens, at the interface between the Juan de Fuca and North American tectonic plates. The plates first come into contact off the Pacific Northwest coast, where the Juan de Fuca plate subducts beneath the North American plate and reaches great depth under the Cascades. As the magma works its way upward, it likely accumulates as a mass several miles beneath the surface.
As the molten rock works its way toward the surface, it is possible that it gathers in a large chamber a few miles beneath the surface. The path from great depth to this chamber is almost completely unknown and is a main subject of the study.
The project is expected to conclude in the summer of 2016.
Note : The above story is based on materials provided by University of Washington
An artist’s conception of two possible views of asteroid 2011 MD. Credit: Image courtesy NASA Jet Propulsion Laboratory
What seemed to be rock-solid assumptions about the nature of small asteroids may end in collections of rubble or even a cloud of dust, but in such findings lies the lure of the unexpected.
Northern Arizona University researchers David Trilling and Michael Mommert, while playing a well-defined role in the NASA Asteroid Initiative, are beginning to wonder if they have found a separate path of investigation.
The two researchers presented their findings about asteroid 2011 MD on Thursday during a NASA event updating progress on the path to capturing a small asteroid and relocating it for a closer look by astronauts in the 2020s.
The job of Trilling and Mommert was to use the infrared capabilities of the Spitzer Space Telescope to determine the size of 2011 MD, which needs to be within a narrow range for the mission to succeed. Trilling, an associate professor, explained that using infrared light is the most accurate way to determine an asteroid’s size because visible light through a traditional telescope fails to distinguish a small, highly reflective asteroid from a large one with little reflectivity.
At around 6 meters in diameter, 2011 MD is just right. But that’s not the whole story.
“People have assumed that small asteroids are debris from collisions of larger asteroids, so those really small guys would be just single slabs of rock flying in space,” said Mommert, a post-doctoral researcher. “But we found that this one is 65 percent empty.”
The findings, which suggest a flying cluster of rocks or a cloud of dust with a solid rock at its nucleus, are similar to observations the NAU researchers published earlier this year of yet another asteroid, 2009 BD.
Trilling said long-held assumptions are yielding to something “weirder and more exotic. The first time you see it, you think, ‘Well, that’s just an anomaly.’ But two out of two, and you start to think that maybe the small ones really don’t look like everyone thought.”
The latest findings appear online today in Astrophysical Journal Letters, coinciding with the NASA presentation. And while NASA seeks to use the asteroid mission to test the technologies and capabilities needed to send astronauts to Mars, Trilling and Mommert are setting their sights elsewhere.
“Now we can go back and propose some more observation time just for the science investigation,” Trilling said. “Now we want to learn something more about the universe.” Mommert said this is a prime opportunity to add data to a field — the study of small asteroids — that is sparsely populated.
“It’s a field that hasn’t been studied a lot because it’s really difficult to observe them and derive their physical properties,” he said. “The density of 99.9 percent of all asteroids is unknown.” He and Trilling have now added two to a single-digit list.
As far as 2011 MD is concerned, NASA will have to be satisfied with the information compiled by the full team, which includes NAU, the University of Hawaii and a number of other NASA and affiliated labs. The asteroid is about to disappear behind the sun, at least from Earth’s perspective, for the next seven years, and will not be observable again before the spacecraft to retrieve it would have to be launched.
Note : The above story is based on materials provided by Northern Arizona University.
Chemical Formula: (Na,Ca)[Al(Si,Al)Si2O8] Locality: Twedestrand, Norway. Name Origin: From the Greek, oligos and kasein, “little cleavage.”
Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite (NaAlSi3O8) and anorthite (CaAl2Si2O8). The albite:anorthite molar ratio ranges from 90:10 to 70:30.
Oligoclase is a high sodium feldspar crystallizing in the triclinic system. The Mohs hardness is 6 to 6.5 and the specific gravity is 2.64 to 2.66. The refractive indices are: nα=1.533–1.543, nβ=1.537–1.548, and nγ=1.542–1.552. In color it is usually white, with shades of grey, green, or red.
Name and discovery
The name oligoclase was given by August Breithaupt in 1826 from the Greek oligos, little, and clasein, to break, because the mineral was thought to have a less perfect cleavage than albite. It had previously been recognized as a distinct species by J. J. Berzelius in 1824, and was named by him soda-spodumene (Natron-spodumen), because of its resemblance in appearance to spodumene.
History
Discovery date : 1826 Town of Origin: DANVIKS-ZOLL, STOCKHOLM Country of Origin: SUEDE
Physical Properties
Cleavage: {001} Perfect, {010} Good Color: Brown, Colorless, Greenish, Gray, Yellowish. Density: 2.64 – 2.66, Average = 2.65 Diaphaneity: Transparent to Translucent Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern. Hardness: 7 – Quartz Luminescence: Fluorescent, Long UV=yellow. Luster: Vitreous (Glassy) Streak: white
Mercuriceratops gemini (center) compared to horned dinosaurs Centrosaurus (left) and Chasmosaurus (right), also from the Dinosaur Park Formation of Alberta, Canada. Credit: Courtesy Danielle Dufault
Scientists have named a new species of horned dinosaur (ceratopsian) based on fossils collected from Montana in the United States and Alberta, Canada. Mercuriceratops (mer-cure-E-sare-ah-tops) gemini was approximately 6 meters (20 feet) long and weighed more than 2 tons. It lived about 77 million years ago during the Late Cretaceous Period. Research describing the new species is published online in the journal Naturwissenschaften.
Mercuriceratops (Mercuri + ceratops) means “Mercury horned-face,” referring to the wing-like ornamentation on its head that resembles the wings on the helmet of the Roman god, Mercury. The name “gemini” refers to the almost identical twin specimens found in north central Montana and the UNESCO World Heritage Site, Dinosaur Provincial Park, in Alberta, Canada. Mercuriceratops had a parrot-like beak and probably had two long brow horns above its eyes. It was a plant-eating dinosaur.
“Mercuriceratops took a unique evolutionary path that shaped the large frill on the back of its skull into protruding wings like the decorative fins on classic 1950s cars. It definitively would have stood out from the herd during the Late Cretaceous,” said lead author Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History. “Horned dinosaurs in North America used their elaborate skull ornamentation to identify each other and to attract mates — not just for protection from predators. The wing-like protrusions on the sides of its frill may have offered male Mercuriceratops a competitive advantage in attracting mates.”
“The butterfly-shaped frill, or neck shield, of Mercuriceratops is unlike anything we have seen before,” said co-author Dr. David Evans, curator of vertebrate palaeontology at the Royal Ontario Museum. “Mercuriceratops shows that evolution gave rise to much greater variation in horned dinosaur headgear than we had previously suspected.”
The new dinosaur is described from skull fragments from two individuals collected from the Judith River Formation of Montana and the Dinosaur Park Formation of Alberta. The Montana specimen was originally collected on private land and acquired by the Royal Ontario Museum. The Alberta specimen was collected by Susan Owen-Kagen, a preparator in Dr. Philip Currie’s lab at the University of Alberta. “Susan showed me her specimen during one of my trips to Alberta,” said Ryan. “I instantly recognized it as being from the same type of dinosaur that the Royal Ontario Museum had from Montana.”
The Alberta specimen confirmed that the fossil from Montana was not a pathological specimen, nor had it somehow been distorted during the process of fossilization,” said Dr. Philip Currie, professor and Canada research chair in dinosaur paleobiology at the University of Alberta. “The two fossils — squamosal bones from the side of the frill — have all the features you would expect, just presented in a unique shape.”
“This discovery of a previously unknown species in relatively well-studied rocks underscores that we still have many more new species of dinosaurs to left to find,” said co-author Dr. Mark Loewen, research associate at the Natural History Museum of Utah.
This dinosaur is just the latest in a series of new finds being made by Ryan and Evans as part of their Southern Alberta Dinosaur Project, which is designed to fill in gaps in our knowledge of Late Cretaceous dinosaurs and study their evolution. This project focuses on the paleontology of some of oldest dinosaur-bearing rocks in Alberta and the neighbouring rocks of northern Montana that are of the same age.
Journal Reference:
Michael J. Ryan, David C. Evans, Philip J. Currie, Mark A. Loewen. A new chasmosaurine from northern Laramidia expands frill disparity in ceratopsid dinosaurs. Naturwissenschaften, 2014; 101 (6): 505 DOI: 10.1007/s00114-014-1183-1
Note : The above story is based on materials provided by Cleveland Museum of Natural History.
Geothermal energy is harvested by pumping cold water down an injection well, and bringing hot water up again via a production well. Left: In areas that produce geothermal energy today, the water flows through natural fractures in the bedrock between the wells, heating up in the process. Right: In future drilling in hard rock that lacks natural cracks, as in Norway, drilling a series of radiating bore-holes between the wells is a possibility. An alternative method is to create such cracks by subjecting the bedrock to extremely high hydraulic pressure (so-called “fracking”). Click Here for large photo Credit: SINTEF/Knut Gangåssæter.
Capturing green energy from deep in the Earth will bring competitive electricity and district heating – with help from Norway.
Ever since Jules Verne’s 1864 novel ” A Journey to the Centre of the Earth”, people have dreamt of capturing the heat of planet Earth. It exists in huge amounts, is completely renewable and emits no CO2.
“What we have done so far is no more than to scratch the surface of the Earth. The heat that many people extract from their gardens and then upgrade in heat pumps is not geothermal, but rather solar energy,” says SINTEF research scientist Alexandre Kane.
Backed by a troop of industrial and technology companies, Kane is manager of the Nextdrill research project, whose members are going ahead at full speed to develop drilling tools that will make it profitable to exploit true geothermal heat.
Stringent cost requirements
The immediate aim is to drill wells to depths of five to six kilometres, where we encounter temperatures that are high enough to allow the heat to be used for district heating and electricity generation.
“For this to be commercially viable we will need to drill much more cheaply than the petroleum industry does, and without needing permanent subsidies. At the same time, we need to penetrate bedrock that is much harder than we find on the continental shelf in the North Sea. It may sound as though it will be impossible to do both of these things at once, but we have a great belief in the possibility, as long as research continues along the same lines after this preliminary project has come to an end,” says Kane.
High speed; long working life
As in all drilling operations, the taximeter rises rapidly. If geothermal heat is to be competitive as a source of energy, the time put into drilling must be kept to a minimum. Drilling operators who want to capture this heat therefore need to be able to drill at high speed. Nor can they afford the loss of time involved if the drill-bit is always having to be brought to the surface and replaced.
The Nextdrill project is a response to this challenge. Three of its members – SINTEF, the Swedish company Sandvik and Germany’s H.C. Starck – are collaborating on the development of materials for a drill-bit with a long working life.
Another participant is the Norwegian technology company Resonator, which is in the process of developing an electric percussion rotary drill, a tool that crushes rock by dealing it hammer-like blows as the drill-bit turns. Electrical operation offers the possibility of remote control and more energy-efficient drilling systems than technology based on today’s pneumatic or hydraulic systems.
First test in August
In the course of this year the Nextdrill project will carry out its first small-scale drilling trials near Ås in Akershus County. In August and again in November, a specially designed version of Resonator’s percussion rotary drill will tackle hard rock. It will be fitted in turn with commercially available drill-bits and bits made of the highly wear-resistant materials that are being developed by the project.
These trials have two main purposes. They will provide new knowledge about how wear occurs on drill-bits when rock is crushed using an electric percussion rotary drill. The tests will also show how the number of impacts per unit time affects the speed of drilling.
“Although we will not be drilling very deep during these tests we do expect to gather important data for the next stages of our efforts to develop highly durable materials,” says Kane.
Geothermal energy
The heat that SINTEF’s French project manager wants to capture is known as geothermal energy, and is derived from two sources that lie far beneath our feet. About one third of it is heat that has been stored in the Earth’s molten core since our planet was formed. The other two-thirds have their origin in the decay of radioactive isotopes in the Earth’s crust. This process releases heat, which means that the temperature rises, metre by metre, the further we drill into the interior of the planet.
Two types of well need to be drilled to exploit this heat; one to pump cold water down, and the other to bring hot water up again (see illustration). The drill-bit that does this job must be able to crush hard rock types such as granite. The main aim of the Nextdrill project is to identify a combination of hard-wearing, durable materials and technical solutions that can do this (see fact-sheet).
Laboratory trials and computer models
The drill-bit needs to be able to withstand a high level of friction, in addition to enormous amounts of mechanical abuse resulting from the high-frequency hammer impacts.
“Laboratory trials and virtual experiments performed by computer models have taught us a great deal about drilling through granite, and have enabled us to develop models that we use to find the optimal form and composition of the drill-bit. The drilling trials at Ås will give us measurements that will let us further improve the computer model,” says Kane.
Note : The above story is based on materials provided by SINTEF
Chemical Formula: CaSi2O5·2H2O Locality: Disko Island, Greenland. Poona, near Bombay, India. Name Origin: Named for Lorenz Oken (1779-1851), German natural historian, Munich Germany.
Okenite (CaSi2O5·2H2O) is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white “cotton ball” formations within basalt geodes. These formations are clusters of straight, radiating, fibrous crystals that are both bendable and fragile.
Discovery and occurrence
It was first described in 1828 for an occurrence at Disko Island, Greenland and named for German naturalist Lorenz Oken (1779–1851).
Minerals associated with okenite include apophyllite, gyrolite, prehnite, chalcedony, goosecreekite and many of the other zeolites. Okenite is found in India, mainly within the state of Maharashtra. Other localities include Bulla Island, Azerbaijan; Aranga, New Zealand; Chile; Ireland and Bordo Island in the Faroe Islands.
History
Discovery date: 1828 Town of Origin : ILE DISKO Country of Origin: GROENLAND
Physical Properties
Cleavage: {001} Good Color: White, Yellowish white, Bluish white. Density: 2.3 – 2.33, Average = 2.31 Diaphaneity:Transparent to Translucent Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). Hardness: 5 – Apatite Luminescence: Non-Fluorescent. Luster: Pearly Streak: white
It is likely that most of the large impact craters on Earth have already been discovered and that others have been erased, according to a new calculation by a pair of Purdue University graduate students.
“Over the past 3.5 billion years it is thought that more than 80 asteroids similar in size to, or larger than, the one which killed the dinosaurs have struck the Earth, leaving behind craters which are over 100 kilometers across, but our model suggests only about eight of these massive craters could still exist today,” said Timothy Bowling, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences. “Geologists have already found six or seven such craters, so odds are not in the favor of those hoping to find the next big crater.”
The movement of the Earth’s tectonic plates and other geologic processes erase craters over time, he said.
“Impact craters dominate the surface of other planets and bodies in our solar system, like the famously pockmarked moon and Mercury, but the Earth looks different,” Bowling said. “The Earth’s crust is very dynamic and active, and over time it pushes and pulls these craters deep below the surface, until eventually they are sunk into the Earth’s mantle and disappear.”
Although it is known that natural processes erase craters fairly quickly from the Earth’s surface, this model was the first to quantify how many craters have likely been erased, he said.
Brandon Johnson, a postdoctoral researcher at the Massachusetts Institute of Technology who at the time was a graduate student at Purdue, led the study, which is to be published in the journal Geology. Both Bowling and Johnson worked under Jay Melosh, a Purdue distinguished professor of earth, atmospheric and planetary sciences and physics. A NASA planetary geology and geophysics grant funded this research.
Bowling and Johnson used the age of the Earth’s terrestrial and oceanic crusts and three different scenarios of Earth’s bombardment history to determine the maximum probability that a crater made a given number of years ago would still exist today. They then estimated the percentage of craters that could persist and be observed today for each of the bombardment scenarios.
The model’s ability to estimate the percentage of large craters that would survive to present day could be useful in supporting or refuting different theories of the ratio of large to small impacts, called the size frequency distribution, Bowling said.
“The number of smaller impacts that would have likely occurred for every large impact we find is a looming question in the field,” he said. “Existing theories are mostly based on studies of craters on the surfaces of other bodies, like the moon. No one had attempted this before using the Earth’s crater record because it couldn’t be done without having an idea of how many craters have been erased. This model could be used to help confirm or refute proposed theories.”
While the model could be applied to studies of the size frequency distribution, it cannot be used to distinguish between different models of the rate at which large objects hit Earth, he said. These models vary from those that expect constant bombardment to those that predict that earlier time periods were responsible for a greater number of impacts.
An ability to accurately determine the date of impact is needed to distinguish between different proposed bombardment scenarios, Bowling said.
Instead of hunting for craters, scientists should search for layers of debris ejected on impact to better understand the Earth’s bombardment history, Bowling said.
When asteroids larger than about 10 kilometers, or six miles, in diameter crash into the Earth a plume of vaporized rock rises into space. Small droplets of this plume condense, solidify and fall back to the surface. A thin layer of these particles, called spherules, then blankets the Earth. This layer of spherules persists in the geologic record and can be used to determine the date of impact. The thickness of the spherule layer and the size of the individual spherules within it also provide information about the asteroid and its size. These spherule layers persist long after the craters have been erased, he said.
More information:
Paper: Where have all the craters gone? Earth’s bombardment history and the expected terrestrial cratering record, Geology, 2014.
Note : The above story is based on materials provided by Purdue University
A sample of the 4.5 billion-year-old Tenham meteorite that contains submicrometer-sized crystals of bridgmanite. Credit: Chi Ma / Caltech
Deep below the earth’s surface lies a thick, rocky layer called the mantle, which makes up the majority of our planet’s volume. For decades, scientists have known that most of the lower mantle is a silicate mineral with a perovskite structure that is stable under the high-pressure and high-temperature conditions found in this region. Although synthetic examples of this composition have been well studied, no naturally occurring samples had ever been found in a rock on the earth’s surface. Thanks to the work of two scientists, naturally occurring silicate perovskite has been found in a meteorite, making it eligible for a formal mineral name.
The mineral, dubbed bridgmanite, is named in honor of Percy Bridgman, a physicist who won the 1946 Nobel Prize in Physics for his fundamental contributions to high-pressure physics.
“The most abundant mineral of the earth now has an official name,” says Chi Ma, a mineralogist and director of the Geological and Planetary Sciences division’s Analytical Facility at Caltech.
“This finding fills a vexing gap in the taxonomy of minerals,” adds Oliver Tschauner, an associate research professor at the University of Nevada-Las Vegas who identified the mineral together with Ma.
High-pressure and temperature experiments, as well as seismic data, strongly suggest that (Mg,Fe)SiO3-perovskite—now simply called bridgmanite—is the dominant material in the lower mantle. But since it is impossible to get to the earth’s lower mantle, located some 400 miles deep within the planet and rocks brought to the earth’s surface from the lower mantle are exceedingly rare, naturally occurring examples of this material had never been fully described.
That is until Ma and Tschauner began poking around a sample from the Tenham meteorite, a space rock that fell in Australia in 1879.
Because the 4.5 billion-year-old meteorite had survived high-energy collisions with asteroids in space, parts of it were believed to have experienced the high-pressure conditions we see in the earth’s mantle. That, scientists thought, made it a good candidate for containing bridgmanite.
Tschauner used synchrotron X-ray diffraction mapping to find indications of the mineral in the meteorite. Ma then examined the mineral and its surroundings with a high-resolution scanning electron microscope and determined the composition of the tiny bridgmanite crystals using an electron microprobe. Next, Tschauner analyzed the crystal structure by synchrotron diffraction. After five years and multiple experiments, the two were finally able to gather enough data to reveal bridgmanite’s chemical composition and crystal structure.
“It is a really cool discovery,” says Ma. “Our finding of natural bridgmanite not only provides new information on shock conditions and impact processes on small bodies in the solar system, but the tiny bridgmanite found in a meteorite could also help investigations of phase transformation mechanisms in the deep Earth. ”
The mineral and the mineral name were approved on June 2 by the International Mineralogical Association’s Commission on New Minerals, Nomenclature and Classification.
Note : The above story is based on materials provided by California Institute of Technology
Chemical Formula: Ni Locality: Bogota, Canala, New Caledonia. Name Origin: From the German Nickel – “demom”, from a contraction of kupfernickel, or “Devil’s Copper”, as the mineral was believed to contain copper but yielded none when smelted.
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile. Pure nickel shows a significant chemical activity that can be observed when nickel is powdered to maximize the exposed surface area on which reactions can occur, but larger pieces of the metal are slow to react with air at ambient conditions due to the formation of a protective oxide surface. Even then, nickel is reactive enough with oxygen that native nickel is rarely found on Earth’s surface, being mostly confined to the interiors of larger nickel–iron meteorites that were protected from oxidation during their time in space. On Earth, such native nickel is always found in combination with iron, a reflection of those elements’ origin as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earth’s inner core.
The use of nickel (as a natural meteoric nickel–iron alloy) has been traced as far back as 3500 BC. Nickel was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. The element’s name comes from a mischievous sprite of German miner mythology, Nickel (similar to Old Nick), that personified the fact that copper-nickel ores resisted refinement into copper. An economically important source of nickel is the iron ore limonite, which often contains 1-2% nickel. Nickel’s other important ore minerals include garnierite, and pentlandite. Major production sites include the Sudbury region in Canada (which is thought to be of meteoric origin), New Caledonia in the Pacific, and Norilsk in Russia.
History
Discovery date : 1967 Town of Origin : BOGOTA, CANALA Country of Origin: NOUVELLE CALEDONIE
This is the VIRTUAL GEOSCIENCE WORKBENCH project (“vgw”)
This project was registered on SourceForge.net on Aug 21, 2008, and is described by the project team as follows:
The Virtual Geoscience Workbench for discontinuous systems is a computer software environment for modelling. We have made the combined Finite-Discrete Element Method (FEMDEM) the core of our solids technology.
Screenshots :
Download :
Source code for this project may be available as downloads or through one of the SCM repositories used by the project, as accessible from the project develop page.
The Niger River is the principal river of western Africa, extending about 4,180 km (2,600 mi). Its drainage basin is 2,117,700 km2 (817,600 sq mi) in area. Its source is in the Guinea Highlands in southeastern Guinea. It runs in a crescent through Mali, Niger, on the border with Benin and then through Nigeria, discharging through a massive delta, known as the Niger Delta or the Oil Rivers, into the Gulf of Guinea in the Atlantic Ocean. The Niger is the third-longest river in Africa, exceeded only by the Nile and the Congo River (also known as the Zaïre River). Its main tributary is the Benue River.
Etymology
The Niger is called Jeliba or Joliba “great river” in Manding; Orimiri or Orimili “great water” in Igbo; Egerew n-Igerewen “river of rivers” in Tuareg; Isa Ber “big river” in Songhay; Kwara in Hausa; and Oya in Yoruba. The origin of the name Niger, which originally applied only to the middle reaches of the river, is uncertain. The likeliest possibility is an alteration, by influence of Latin niger “black”, of the Tuareg name egerew n-igerewen, which is used along the middle reaches of the river around Timbuktu. As Timbuktu was the southern end of the principal Trans-Saharan trade route to the western Mediterranean, it was the source of most European knowledge of the region.
Medieval European maps applied the name Niger to the middle reaches of the river, in modern Mali, but Quorra (Kworra) to the lower reaches in modern Nigeria, as these were not recognized as being the same river. When European colonial powers began to send ships along the West coast of Africa in the 16th and 17th centuries, the Senegal River was often postulated to be seaward end of the Niger. The Niger Delta, pouring into the Atlantic through mangrove swamps and thousands of distributaries along more than a hundred miles, was thought to be no more than coastal wetlands. It was only with the 18th century visits of Mungo Park, who travelled down the Niger River and visited the great Sahelian empires of his day, that Europeans correctly identified the course of the Niger, and extending the name to its entire course.
The modern nations of Nigeria and Niger take their names from the river, marking contesting national claims by colonial powers of the “Upper”, “Lower” and “Middle” Niger river basin during the Scramble for Africa at the end of the 19th century.
Geography
The Niger River is a relatively “clear” river, carrying only a tenth as much sediment as the Nile because the Niger’s headwaters lie in ancient rocks that provide little silt. Like the Nile, the Niger floods yearly; this begins in September, peaks in November, and finishes by May.
An unusual feature of the river is the Inner Niger Delta, which forms where its gradient suddenly decreases. The result is a region of braided streams, marshes, and lakes the size of Belgium; the seasonal floods make the Delta extremely productive for both fishing and agriculture.
The river ‘loses’ nearly two-thirds of its potential flow in the Inner Delta between Ségou and Timbuktu to seepage and evaporation. All the water from the Bani River, which flows into the Delta at Mopti, does not compensate for the ‘losses’. The average ‘loss’ is estimated at 31 km3/year, but varies considerably between years. The river is then joined by various tributaries, but also loses more water to evaporation. The quantity of water entering Nigeria measured in Yola was estimated at 25 km3/year before the 1980s and at 13.5 km3/year during the 1980s. The most important tributary of the Niger in Nigeria is the Benue River which merges with the river at Lokoja in Nigeria. The total volume of tributaries in Nigeria is six times higher than the inflow into Nigeria, with a flow near the mouth of the river standing at 177.0 km3/year before the 1980s and 147.3 km3/year during the 1980s.
The above story is based on materials provided by Wikipedia
Chemical Formula: Na3Mg(CO3)2Cl Locality: Searles Lake, San Bernardino Co., California. Name Origin: Named after C. H. Northup (b.1861), grocer, of San Jose, California, who found the first specimen.
Northupite is an uncommon evaporite mineral, with the chemical formula Na3Mg(CO3)2Cl. It occurs as colourless to dark grey or brown octahedral crystals and as globular masses. In synthetic material it forms a series with tychite (Na6Mg2(CO3)4SO4).
It was discovered in 1895 at Searles Lake, San Bernardino County, California by C. H. Northup (born 1861) from San Jose, California, for whom Northupite is named.
It occurs associated with tychite, pirssonite at Searles Lake and with shortite, trona, pirssonite, gaylussite, labuntsovite, searlesite, norsethite, loughlinite, pyrite and quartz in the Green River Formation of Wyoming.
History
Discovery date : 1895 Town of Origin : SEARLES LAKE, BORAX LAKE, SAN BERNARDINO CO., CALIFORNIE Country of Origin: USA
Optical properties
Optical and misc. Properties : Transparent Refractive Inde : 1,51
Physical Properties
Cleavage: None Color: Brownish, Colorless, Gray, Gray brown, Yellow. Density: 2.38 Diaphaneity: Transparent to translucent Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 3.5-4 – Copper Penny-Fluorite Luminescence: Fluorescent and Phosphorescent, Long UV=bright cream white. Luster: Vitreous (Glassy) Magnetism: Nonmagnetic Streak: white
View looking north at the Ice River spring, the highest latitude perennial spring known. Located in the polar desert of northern Ellesmere Island, Nunavut, the high discharge spring carves a gully remarkable similar to those observed on Mars. Credit: Photo by Stephen Grasby
A Canadian team lead by Stephen Grasby reports the discovery of the highest latitude perennial spring known in the world. This high-volume spring demonstrates that deep groundwater circulation through the cryosphere occurs, and can form gullies in a region of extreme low temperatures and with morphology remarkably similar to those on Mars. The 2009 discovery raises many new questions because it remains uncertain how such a high-volume spring can originate in a polar desert environment.
Grasby and colleagues encountered the northernmost perennial spring in the world, which they have dubbed the Ice River Spring, on Ellesmere Island, Nunavut, Canadian High Arctic. The specific study area is north of Otto Fiord in a mountainous region underlain by carbonates of the Nansen Formation. The spring discharges at 300 m elevation from colluvium on a south-facing (21° incline) mountain slope. The unnamed mountain rises 800 m above sea level. Detailed recordings show that this spring flows year-round, even during 24 hours of darkness in the winter months, when air temperatures are as low as minus 50 degrees Celsius.
Detailed geochemistry shows that the waters originate from the surface and circulate down as deep as 3 km before returning through thick permafrost as a spring. This points to a much more active hydrogeological system in polar regions than previously thought possible, which is perhaps driven by glacial meltwater.
Another intriguing feature of the Ice River site is the remarkable similarity to mid-latitude gullies observed on Mars. The discovery of these features on Mars has led to suggestions that recent groundwater discharge has occurred from confined aquifers.
Note : The above story is based on materials provided by Geological Society of America.
Climate change is unlikely to lead to more days of extreme cold, similar to those that gripped the United States in a deep freeze last winter, new research has shown.
The Arctic amplification phenomenon refers to the faster rate of warming in the Arctic compared to places further south. It is this phenomenon that has been linked to a spike in the number of severe cold spells experienced in recent years over Europe and North America.
However, new research by University of Exeter expert Dr James Screen has shown that Arctic amplification has actually reduced the risk of cold extremes across large swathes of the Northern Hemisphere.
The intriguing new study, published in the scientific journal Nature Climate Change, questions growing fears that parts of Europe and North America will experience a greater number, or more severe, extreme cold days over the course of the next century.
Dr Screen, a Mathematics Research Fellow at the University of Exeter, said: “Autumn and winter days are becoming warmer on average, and less variable from day-to-day. Both factors reduce the chance of extremely cold days.”
The idea that there was a link between Arctic amplification and extreme weather conditions became prevalent during the severe winter weather that plagued large areas of the United States in January 2014, leading to major transport disruption, power cuts and crop damage.
In his study, Dr Screen examined detailed climate records to show that autumn and winter temperature variability has significantly decreased over the mid-to-high latitude Northern Hemisphere in recent decades.
He found that this has occurred mainly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days.
Dr Screen said: “Cold days tend to occur when the wind is blowing from the north, bringing Arctic air south into the mid-latitudes. Because the Arctic air is warming so rapidly these cold days are now less cold than they were in the past.”
Using the latest mathematical climate modelling, Dr Screen has also been able to show that these changes will continue in to the future, with projected future decreases in temperature variability in all seasons, except summer.
Note : The above story is based on materials provided by University of Exeter.
Chemical Formula: Mg3(SiO4)(F,OH)2 Locality: Ostanmosoa iron mine, Norberg, Vastmanland, Sweden. Name Origin: Named after its locality.
Norbergite is a nesosilicate mineral with formula Mg3(SiO4)(F,OH)2. It is a member of the humite group.
It was first described in 1926 for an occurrence in the Ostanmosoa iron mine in Norberg, Västmanland, Sweden, for which it is named. It occurs in contact metamorphic zones in carbonate rocks intruded by plutonic rocks or pegmatites supplying the fluorine. Associated minerals include dolomite, calcite, tremolite, grossular, wollastonite, forsterite, monticellite, cuspidine, fluoborite, ludwigite, fluorite and phlogopite.
History
Discovery date : 1926 Town of Origin : NORBERG Country of Origin : SUEDE
Optical properties
Optical and misc. Properties: Transparent – Translucide – fluorescent Refractive Index: from 1,56 to 1,59 Axial angle 2V: 44-50°
Physical Properties
Cleavage: Distinct Color: White, Yellow, Brown, Red. Density: 3.1 – 3.2, Average = 3.15 Diaphaneity: Transparent to translucent Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces. Hardness: 6-6.5 – Orthoclase-Pyrite Luminescence: Fluorescent, Short UV=bright yellow. Luster: Vitreous – Resinous Streak: white
Chinese and American scientists collaborating in the study of an active seismic fault that produced one of China’s most deadly earthquakes say their deployment of an airborne LiDAR system, which uses pulses of laser light to calculate distances and chart terrain features, has helped them produce the most precise topographical measurements ever of the fault zone.
“Light detection and ranging (LiDAR) presents a new approach to build detailed topographic maps effectively,” they report. They add that these high-precision three-dimensional models can be used to illustrate not only land surface changes following past quakes, but also features of past ruptures that could point to the possibility of future temblors.
Experts at the State Key Laboratory of Earthquake Dynamics and at the National Earthquake Infrastructure Service in Beijing, working with a colleague at the United States Geological Survey (USGS) in Pasadena, California, mounted a Leica ALS-60 LiDAR system aboard a Chinese Yun Five aircraft and then began scanning the Haiyuan fault zone in a series of flights over the course of a week. The fault zone is similar to the San Andreas fault in California, which has similarly been scanned and studied as a comparison.
“During the past century,” they explain in a new study, “the Haiyuan fault zone produced two great earthquakes: the M 8.5 Haiyuan earthquake in 1920, along the eastern Haiyuan fault, and the M 8–8.3 Gulang earthquake in 1927.”
“The Haiyuan earthquake of 16 December 1920 is one of the largest intra- continental earthquakes ever documented in history,” they add, “and ruptured about a 237-kilometer-long ground surface, with a maximum left-lateral slip of 10.2 m, and claimed over 220,000 lives.”
In the new study, “Quantitative study of tectonic geomorphology along the Haiyuan fault based on airborne LiDAR,” lead scientist Jing Liu and her colleagues at the Earthquake Dynamics Lab, part of the China Earthquake Administration in Beijing, state their experiments with the LiDAR scanning system and related building of a high-resolution topographical model provide “an example of how LiDAR data may be used to improve the study of active faults and the risk assessment of related hazards.”
Sections of the 3D digital model generated with the LiDAR data are “intensively analyzed to demonstrate tectonic geomorphic feature identification and displacement measurement,” they state. The LiDAR data are also used, for example, to calculate horizontal and vertical coseismic offsets in one section of the fault zone.
LiDAR data can be used to verify measurements made during fieldwork on offsets of tectonic landform features, state co-authors Tao Chen, Pei Zhen Zhang, Jing Liu, Chuan You Li, and Zhi Kun Ren, along with Ken Hudnut at the USGS, who visited the China Earthquake Administration to participate in this study. “The offset landforms are visualized on an office computer workstation easily, and specialized software may be used to obtain fault displacement measurements quantitatively,” they explain.
With LiDAR-generated digital models of the topography across fault zones, the “link between fault activity and large earthquakes is better recognized, as well as the potential risk for future earthquake hazards,” says the team of scientists.
More precise measurements of the active fault zone made possible by the LiDAR system, and their depiction in sophisticated three-dimensional maps, are helping scientists not only in basic research, but also in terms of calculating the probability of a seismic shock recurring, say the co-authors of the new study, which was published online in the journal Chinese Science Bulletin by Science China Press and Springer-Verlag.
Airborne laser swath mapping helps scientists to virtually remove the vegetation covering from topographical models; this “bare earth” representation provides for more accurate identification of tectonic features and changes following a quake.
A LiDAR airborne scanning system of the Earth’s terrain was deployed over the section of the southwestern Chinese province of Sichuan that was the epicenter of a Mw7.9 earthquake that struck in May of 2008; LiDAR data were used to map the scale of landslides and ultimately to develop rescue schemes.
In the new study, the Chinese and American scientists say that digital models created using LiDAR data from the Haiyuan fault zone “have a much higher resolution than existing topographic data and most aerial photographs, allowing us to map the locations of fault traces more accurately than ever.”
The high level of precision of the digital models constructed with information from the LiDAR laser scans of the topography in this fault zone will encourage future “site-specific fault activity studies,” state the scientists.
“In the future,” they predict, “we can expect that more and more concepts or models of fault activity would benefit from this unprecedented survey technique.”
Along the Haiyuan fault zone in the western Chinese province of Gansu, LiDAR scans and related digital models have already been used to identify 600 channels and other linear geomorphic features slated for more comprehensive analysis.
“The next step is to measure the displacements along the whole Haiyuan fault and analyze the principle of the slip distribution,” states the team of scientists, “which would help people better understand the fundamental link between fault activity and large earthquakes and assess potential risk for future earthquake hazards.”
In places where slip during past earthquakes was less pronounced, it is possible that future earthquakes could have greater slip in order to accommodate and equalize motions along the fault system. Alternatively, slip may be large repeatedly in some places and small elsewhere. Such variations in slip may help to assess future hazards, so observations of this kind are very important to answer unresolved questions that are central to research on hazards of earthquake fault zones around the world. More information:
Chinese Science Bulletin July 2014, Volume 59, Issue 20, pp 2396-2409. link.springer.com/article/10.1… %2Fs11434-014-0199-4
Note : The above story is based on materials provided by Science China Press
Roy Price first heard about the hydrothermal vents in New Caledonia’s Bay of Prony a decade ago. Being a scuba diver and a geologist, he was fascinated by the pictures of a 38-meter-high calcite “chimney” that had precipitated out of the highly-alkaline vent fluid.
His attraction to this South Pacific site intensified over the years, as it was later revealed that the geochemistry of the hydrothermal fluids discharging in the Bay of Prony resemble that of the mid-Atlantic’s “Lost City,” one of the most spectacular of all hydrothermal vent systems. The unique chemical and biological conditions at the Lost City has led some scientists to speculate that the origin of life may have occurred around similar sorts of vents in the Earth’s distant past.
“The site in New Caledonia is very similar to the Lost City in many ways,” Price said.
Like the Lost City, the water that bubbles out of the Prony vents has an extremely alkaline pH of around 11. Temperatures reach up to 40° C (104° F) in some places, and fluids are highly enriched in dissolved hydrogen (H2) and methane (CH4). Calcium dissolved in the fluids reacts with bicarbonate in seawater, which leads to the formation of tall, monolithic calcite chimneys that look like ruins from an ancient civilization.
Besides having many geochemical similarities, Prony and the Lost City also have similar microbiology, as demonstrated by recent work from the “HYDROPRONY” research group, an interdisciplinary research team affiliated with the Mediterranean Institute of Oceanography (MIO) and the French Institute of Research for Development (IRD).
One big difference, however, is that the Lost City is nearly a kilometer underwater, whereas the main Prony chimney, called “the Needle of Prony” or “l’Aiguille” in French, nearly breaches the water surface, making the site accessible to divers.
Price, who is now a researcher at the School of Marine and Atmospheric Sciences, State University of New York, Stony Brook, asked the HYDROPRONY group for permission to join them on a field expedition in April 2014. His motivation was to test whether the Prony vents can produce organic compounds abiotically, without any biological influence.
“The abiotic production of hydrocarbons and other simple organic compounds in places such as these may have led or at least contributed to abiogenesis—the [long-ago] switch from abiotic chemical reactions to biologically-mediated reactions probably similar to today’s microbial metabolisms,” Price said.
With funding from a NASA Early Career Collaboration award, Price flew to New Caledonia to test whether the chemical precursors of this ancient switch can be found in Prony Bay.
Early Earth analog
As soon as he arrived on New Caledonia, Price was struck by the red soil that covers the southern part of the main island. This soil comes from the erosion of ultramafic rock, which is a rare type of iron-rich, silica-poor rock, only found in a few places on earth today.
Ultramafic rocks give rise to the hydrothermal vents in both Prony Bay and the Lost City. When exposed to water, ultramafic rocks go through a chemical weathering process called serpentinization. Specifically, the iron in the rock oxidizes, producing hydrogen gas (H2), as well as heat. The hydrogen reacts with carbon dioxide in the water to produce one of the simplest organic molecules, methane (CH4).
“This is a key point—an organic compound produced without any biological interactions whatsoever,” Price explained. “Other slightly more complex organic molecules can also be produced abiotically.”
Ultramafic rocks are not very common on the Earth’s surface now, so it’s rare to find areas with ongoing serpentinization. But billions of years ago when life was getting its start, “ultramafic rocks may have been much more abundant,” Price said. The Earth was much hotter back then, allowing more iron-rich (ultramafic-producing) lava to flow up from the mantle to the crust.
One might imagine, then, that the first precursors to life took advantage of the conditions around these types of hydrothermal vents, co-opting the geochemical reactions to form their own “biological serpentinization” that extracted energy from the reduction of carbon dioxide with hydrogen, forming methane in the process.
Price’s experiments in New Caledonia could provide some ground truth for these origin-of-life speculations. The methane and hydrogen in the hydrothermal fluids from Prony will be analyzed in the lab to determine their carbon and hydrogen isotopic abundances. If the vent’s methane is enriched in carbon-13 and depleted in deuterium (heavy hydrogen), that could be evidence of abiotic production.
“If the methane is produced abiotically, then we will have in the Prony hydrothermal site an early Earth analog which may help us understand the complex sequence of events which led to the origin of life,” Price said.
Fielding an answer
In the days leading up to his first dive, Price spoke with several IRD researchers, including Bernard Pelletier and Claude Payri, the investigators who recently ‘rediscovered’ the hydrothermal cones in the Bay of Prony.
On April 16, Price met the diving leader, Eric Folcher of IRD, who drove him out to the boat launch on the bay. They were joined in the field by two members of the HYDROPRONY group—microbiologists Gaël Erauso of the Mediterranean Institute of Oceanography (University of Marseille) and Mylène Hugoni of the University Blaise Pascal. They are studying the genetic make-up of the microbes and viruses that inhabit the vent environments.
“The weather was particularly good this day, lacking the nearly constant wind the island experiences,” Price recounted. “This not only meant a very smooth ride out to the Needle, but also hinted that there would be very good visibility during the dive.”
When the team’s boat pulled into position, Price caught his first glimpse of the Needle, with its mineral-crusted dome clearly visible about 3 meters below the surface.
Price prepared his sampling equipment, which included several gas-tight syringes to syphon fluids discharging from the vents. When he and Folcher dived in the water, they were immediately surprised by a swarm of moon jellyfish.
“Within my field of view at the surface, I could see dozens of these stinging medusa,” Price said.
The top of the Needle has no active venting, so the divers swam down the side of the chimney to a depth of about 12 meters (39 feet), where they began to see white-tipped, cone-like structures out of which hydrothermal fluids flow.
The water coming out of the vents is fresh, not salty, causing it to shimmer when it mixes with the surrounding seawater. The vent fluid is fresh because it originates from rainwater, which percolates down through the rocks on the island. This water then reacts with the rocks by the serpentinization reactions described earlier, and finally drains down beneath the bay before discharging at the Needle and other areas in and around the bay.
This freshwater distinguishes the Prony hydrothermal field from other sites such as Lost City, which are fed with saltwater. Another unique feature of Prony is that it is in the photic zone, where sunlight can reach the microbial communities, as it does in terrestrial hot springs.
“All this suggests that Prony is a hybrid vent system, with geochemical and microbial characteristics similar to both terrestrial and marine systems,” Price said.
The divers approached a striking cone-like structure at approximately 16 meters (52 feet) deep to obtain samples. A temperature reading showed that the exiting fluids were about 33° C (91° F), which is 8 to 9°C higher than the ambient seawater. The fluids are heated by the serpentinization process, rather than the volcanic processes that power other vents.
The venting is very slow, so it took Price about 10 minutes to fill just one of his 50-milliliter syringes with vent fluid while preventing seawater from being sucked in as well. Maintaining position in the water during this filling procedure was one of the main challenges on this diving expedition.
“We cannot touch the cone, for fear of breaking it or crushing some of the reef organisms,” he said. “For a scuba diver, having the ability to hang in the water column like this takes a lot of practice, and it is not so easy. I use my breathing to maintain my position. If I’m dropping a little too low, I’ll take a slightly deeper breath. The air in my lungs then raises me a little. Too much and I breath out, which drops me back into position.”
With an hour of dive time, Price managed to collect five syringes of hydrothermal fluids. Back on the boat, he “fixed” the samples so that their geochemical properties wouldn’t begin evolving inside the sample tubes. He measured a pH of 10.1 in the samples, which is one of the highest values obtained for these submarine vents. Full analysis will occur later in the lab.
Spring loading
In addition to the syringe samples, the researchers also needed to collect larger volume samples in order to ‘capture’ organisms living in this unique environment. Erauso and Hugoni plan to do a thorough DNA survey in order to catalogue the diversity of species, and perhaps cultivate unidentified microorganisms, including Archaea, who thrive in these very alkaline environments.
For this biological research, the team collected mineral precipitates, where these vent organisms might be living. Underwater, the divers also installed a funnel above one vent in order to concentrate the discharge into a large plastic bag. The goal was to collect around 40 liters of fluid, which could then be filtered to remove microbes and viruses. However, the low flow rate posed a problem in filling the large bags.
The team had better luck at two nearby hot springs, the Bain des Japonais Spring and the Rivière des Kaoris Spring. Both of these sites are intertidal, located right on the coast of the Bay of Prony, where they get covered by seawater in high tide.
The Japonais site consists of a handful of outcroppings, which are shorter versions of the chimneys found in the middle of bay. At low tide, hydrothermal fluid discharges from the depths without much mixing with seawater. The team found that this ‘pristine’ fluid had a temperature 41° C (106° F) and a pH of 11.2, giving some indication of the geochemical characteristics of the subsurface fluids.
The Kaoris Spring is at the mouth of a stream that empties into Prony Bay. It consists of a large terrace, where warm hydrothermal fluid helps to support a variety of microbial biofilms. The researchers collected 40 liters of the fluids along with some slices of these biofilms.
Primordial soup kitchens
The samples from the Needle and the two intertidal hot springs are currently being analyzed, and Price plans to use the results in an upcoming NASA Exobiology proposal, which aims to give the first detailed carbon cycling geochemistry from the Prony hydrothermal field.
“The more I think about it, the more I wonder about systems like this on the early Earth,” Price said. “Today, groundwater that reacts with underlying rocks can be seen discharging along the coastlines everywhere around the world. This phenomenon must have occurred on the early Earth, but [back then] many of the rocks would have been ultramafic.”
Hybrid, Prony-like systems may therefore have been very common during our planet’s beginnings, Price said. They may also have existed on Mars and other planetary bodies in our solar system.
“Based on our current understanding of the early Earth, these types of transitional environments could have been highly important for origin of life scenarios,” Price said.
Note : The above story is based on materials provided by Astrobio.net
