New tool for measuring frozen gas in ocean floor sediments

<IMG SRC="/Images/409444153.jpg" WIDTH="350" HEIGHT="319" BORDER="0" ALT="The figure shows how methane migrates up through the seabed and escapes as plumes of gas bubbles. The image is taken from Westbrook et al. (2009) GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15608, doi:10.1029/2009GL039191 – From Westbrook et al. (2009) GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15608, doi:10.1029/2009GL039191″>
The figure shows how methane migrates up through the seabed and escapes as plumes of gas bubbles. The image is taken from Westbrook et al. (2009) GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15608, doi:10.1029/2009GL039191 – From Westbrook et al. (2009) GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15608, doi:10.1029/2009GL039191

A collaboration between the National Oceanography Centre (NOC) and the University of Southampton is to develop an instrument capable of simulating the high pressures and low temperatures needed to create hydrate in sediment samples.

Dr Angus Best of NOC and Professors Tim Leighton and Paul White from the University of Southampton’s Institute of Sound and Vibration Research (ISVR) have been awarded a grant of £0,8 million by the Natural Environment Research Council (NERC) to investigate methods for assessing the volume of methane gas and gas hydrate locked in seafloor sediments.

Dr Best, who is leading the project, explained: “Greenhouse gases, such as methane and carbon dioxide, are trapped in sediments beneath the seafloor on continental shelves and slopes around the world. Currently, there are only very broad estimates of the amount of seafloor methane and hydrate.”

The team plan a series of experiments on a range of sediment types, such as sand and mud. They intend to map out the acoustic and electrical properties of differing amounts of free methane gas and frozen solid methane hydrate.

The laboratory-based approach adopted by the team will involve the development of a major new Acoustic Pulse Tube instrument at NOC. Using acoustic techniques and theories developed by the ISVR team, they aim to provide improved geophysical remote sensing capabilities for better quantification of seafloor gas and hydrate deposits in the ocean floor.

“Not much is known about the state of gas morphology – bubbles. Muddy sediments show crack-like bubbles, while sandy sediments show spherical bubbles. Only dedicated lab experiments can hope to unravel the complex interactions. By creating our own ‘cores’ of sediment material in a controlled environment where we know the concentrations of methane or carbon dioxide, we can create models to help us with in situ measurements on the seafloor.”

There is significant interest in sub-seafloor carbon-dioxide storage sites. Methane hydrates are a potential energy resource that could be exploited in future. They may also contribute to geo-hazards such as seafloor landslides – it is thought that earthquakes and the release of gas hydrates caused the largest-ever landslide, the Storegga Slide, around 8,000 years ago.

Professor Leighton said: “The three of us have collaborated in recent years in an experiment that used acoustics to take preliminary measurements of gas in the muddy sediments revealed at low tide. Those measurements, and the acoustic theory we developed to interpret the data, provided exactly the foundation we needed to undertake this critically important study that will be relevant to the seabed in somewhat deeper waters.

“As a greenhouse gas, methane is 20 times more potent per molecule than carbon dioxide. There is the potential for climate change to alter sea temperatures and cause more methane gas to be released from seabed hydrates into bubbles which reach the atmosphere. It is therefore vital that we have the tools to quantify and map the amount of methane that is down there.”

Fragments of continents hidden under lava in the Indian Ocean

The islands Reunion and Mauritius, both well-known tourist destinations, are hiding a micro-continent, which has now been discovered. The continent fragment known as Mauritia detached about 60 million years ago while Madagascar and India drifted apart, and had been hidden under huge masses of lava. Such micro-continents in the oceans seem to occur more frequently than previously thought, says a study in the latest issue of Nature Geoscience (“A Precambrian microcontinent in the Indian Ocean,” Nature Geoscience, Vol 6, doi: 10.1038/NGEO1736).

The break-up of continents is often associated with mantle plumes: These giant bubbles of hot rock rise from the deep mantle and soften the tectonic plates from below, until the plates break apart at the hotspots. This is how Eastern Gondwana broke apart about 170 million years ago. At first, one part was separated, which in turn fragmented into Madagascar, India, Australia and Antarctica, which then migrated to their present position.

Plumes currently situated underneath the islands Marion and Reunion appear to have played a role in the emergence of the Indian Ocean. If the zone of the rupture lies at the edge of a land mass (in this case Madagascar / India), fragments of this land mass may be separated off. The Seychelles are a well-known example of such a continental fragment.

A group of geoscientists from Norway, South Africa, Britain and Germany have now published a study that suggests, based on the study of lava sand grains from the beach of Mauritius, the existence of further fragments. The sand grains contain semi-precious zircons aged between 660 and 1970 million years, which is explained by the fact that the zircons were carried by the lava as it pushed through subjacent continental crust of this age.

This dating method was supplemented by a recalculation of plate tectonics, which explains exactly how and where the fragments ended up in the Indian Ocean. Dr. Bernhard Steinberger of the GFZ German Research Centre for Geosciences and Dr. Pavel Doubrovine of Oslo University calculated the hotspot trail: “On the one hand, it shows the position of the plates relative to the two hotspots at the time of the rupture, which points towards a causal relation,” says

Steinberger. “On the other hand, we were able to show that the continent fragments continued to wander almost exactly over the Reunion plume, which explains how they were covered by volcanic rock.” So what was previously interpreted only as the trail of the Reunion hotspot, are continental fragments which were previously not recognized as such because they were covered by the volcanic rocks of the Reunion plume. It therefore appears that such micro-continents in the ocean occur more frequently than previously thought.

Caves point to thawing of Siberia

Evidence from Siberian caves suggests that a global temperature rise of 1.5 degrees Celsius could see permanently frozen ground thaw over a large area of Siberia, threatening release of carbon from soils, and damage to natural and human environments.

A thaw in Siberia’s permafrost (ground frozen throughout the year) could release over 1000 giga-tonnes of the greenhouse gases carbon dioxide and methane into the atmosphere, potentially enhancing global warming.

The data comes from an international team led by Oxford University scientists studying stalactites and stalagmites from caves located along the ‘permafrost frontier’, where ground begins to be permanently frozen in a layer tens to hundreds of metres thick. Because stalactites and stalagmites only grow when liquid rainwater and snow melt drips into the caves, these formations record 500,000 years of changing permafrost conditions, including warmer periods similar to the climate of today.

Records from a particularly warm period (Marine Isotopic Stage 11) that occurred around 400,000 years ago suggest that global warming of 1.5°C compared to the present is enough to cause substantial thawing of permafrost far north from its present-day southern limit.

A report of the research is published in this week’s Science Express. The team included scientists from Britain, Russia, Mongolia and Switzerland.

‘The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia,’ said Dr Anton Vaks of Oxford University’s Department of Earth Sciences, who led the work. ‘As permafrost covers 24% of the land surface of the Northern hemisphere significant thawing could affect vast areas and release giga-tonnes of carbon.

‘This has huge implications for ecosystems in the region, and for aspects of the human environment. For instance, natural gas facilities in the region, as well as power lines, roads, railways and buildings are all built on permafrost and are vulnerable to thawing. Such a thaw could damage this infrastructure with obvious economic implications.’

The team used radiometric dating techniques to date the growth of cave formations (stalactites and stalagmites). Data from the Ledyanaya Lenskaya Cave – near the town of Lensk latitude 60°N – in the coldest region showed that the only period when stalactite growth took place occurred about 400,000 years ago, during a period with a global temperature 1.5°C higher than today. Periods when the world was 0.5-1°C warmer than today did not see any stalactite growth in this northernmost cave, suggesting that around 1.5°C is the ‘tipping point’ at which the coldest permafrost regions begin to thaw.

Dr Vaks said: ‘Although it wasn’t the main focus of our research our work also suggests that in a world 1.5°C warmer than today, warm enough to melt the coldest permafrost, adjoining regions would see significant changes with Mongolia’s Gobi Desert becoming much wetter than it is today and, potentially, this extremely arid area coming to resemble the present-day Asian steppes.’

Researchers propose new way to probe Earth’s deep interior

The picture depicts the long-range spin-spin interaction (blue wavy lines) in which the spin-sensitive detector on Earth's surface interacts with geoelectrons (red dots) deep in Earth's mantle. The arrows on the geoelectrons indicate their spin orientations, opposite that of Earth's magnetic field lines (white arcs). -  Marc Airhart (University of Texas at Austin) and Steve Jacobsen (Northwestern University).
The picture depicts the long-range spin-spin interaction (blue wavy lines) in which the spin-sensitive detector on Earth’s surface interacts with geoelectrons (red dots) deep in Earth’s mantle. The arrows on the geoelectrons indicate their spin orientations, opposite that of Earth’s magnetic field lines (white arcs). – Marc Airhart (University of Texas at Austin) and Steve Jacobsen (Northwestern University).

Researchers from Amherst College and The University of Texas at Austin have described a new technique that might one day reveal in higher detail than ever before the composition and characteristics of the deep Earth.

There’s just one catch: The technique relies on a fifth force of nature (in addition to gravity, the weak and strong nuclear forces and electromagnetism) that has not yet been detected, but which some particle physicists think might exist. Physicists call this type of force a long-range spin-spin interaction. If it does exist, this exotic new force would connect matter at Earth’s surface with matter hundreds or even thousands of kilometers below, deep in Earth’s mantle. In other words, the building blocks of atoms-electrons, protons, and neutrons-separated over vast distances would “feel” each other’s presence. The way these particles interact could provide new information about the composition and characteristics of the mantle, which is poorly understood because of its inaccessibility.

“The most rewarding and surprising thing about this project was realizing that particle physics could actually be used to study the deep Earth,” says Jung-Fu “Afu” Lin, associate professor at The University of Texas at Austin’s Jackson School of Geosciences and co-author of the study appearing this week in the journal Science.

This new force could help settle a scientific quandary. When earth scientists have tried to model how factors such as iron concentration and physical and chemical properties of matter vary with depth – for example, using the way earthquake rumbles travel through the Earth or through laboratory experiments designed to mimic the intense temperatures and pressures of the deep Earth – they get different answers. The fifth force, assuming it exists, might help reconcile these conflicting lines of evidence.

Earth’s mantle is a thick geological layer sandwiched between the thin outer crust and central core, made up mostly of iron-bearing minerals. The atoms in these minerals and the subatomic particles making up the atoms have a property called spin. Spin can be thought of as an arrow that points in a particular direction. It is thought that Earth’s magnetic field causes some of the electrons in these mantle minerals to become slightly spin-polarized, meaning the directions in which they spin are no longer completely random, but have some preferred orientation. These electrons have been dubbed geoelectrons.

The goal with this project was to see whether the scientists could use the proposed long-range spin-spin interaction to detect the presence of these distant geoelectrons.

The researchers, led by Larry Hunter, professor of physics at Amherst College, first created a computer model of Earth’s interior to map the expected densities and spin directions of geoelectrons. The model was based in part on insights gained from Lin’s laboratory experiments that measure electron spins in minerals at the high temperatures and pressures of Earth’s interior. This map gave the researchers clues about the strength and orientations of interactions they might expect to detect in their specific laboratory location in Amherst, Mass.

Second, the researchers used a specially designed apparatus to search for interactions between geoelectrons deep in the mantle and subatomic particles at Earth’s surface. The team’s experiments essentially explored whether the spins of electrons, neutrons or protons in various laboratories might have a different energy, depending on the direction with respect to the Earth that they were pointing.

“We know, for example, that a magnet has a lower energy when it is oriented parallel to the geomagnetic field and it lines up with this particular direction – that is how a compass works,” explains Hunter. “Our experiments removed this magnetic interaction and looked to see if there might be some other interaction with our experimental spins. One interpretation of this ‘other’ interaction is that it could be a long-range interaction between the spins in our apparatus and the electron spins within the Earth, that have been aligned by the geomagnetic field. This is the long-range spin-spin interaction we were looking for.”

Although the apparatus was not able to detect any such interactions, the researchers could at least infer that such interactions, if they exist, must be incredibly weak – no more than a millionth of the strength of the gravitational attraction between the particles. That’s useful information as scientists now look for ways to build ever more sensitive instruments to search for the elusive fifth force.

“No one had previously thought about the possible interactions that might occur between the Earth’s spin-polarized electrons and precision laboratory spin-measurements,” says Hunter.

“If the long-range spin-spin interactions are discovered in future experiments, geoscientists can eventually use such information to reliably understand the geochemistry and geophysics of the planet’s interior,” says Lin.

Flow of research on ice sheets helps answer climate questions

Just as ice sheets slide slowly and steadily into the ocean, researchers are returning from each trip to the Arctic and Antarctic with more data about climate change, including information that will help improve current models on how climate change will affect life on the earth, according to a Penn State geologist.

“It is not just correlation, it is causation,” said Richard Alley, Evan Pugh Professor of Geosciences. “We know that warming is happening and it’s causing the sea levels to rise and if we expect more warming, we can expect the sea levels to rise even more.”

Alley, who reports on his research today (Feb. 16) at the annual meeting of the American Association for the Advancement of Science in Boston, has studied the movement of ice sheets in Greenland and the Antarctic over the years. One way researchers are measuring climate change is by collecting data on how fast ice sheets are flowing toward the sea and comparing those speeds over time, according to Alley.

Ice sheets are miles-thick, continent-wide layers of ice that spread toward the oceans. The researcher said that rising air temperature speeds melting in warmer parts of ice sheets, contributing to sea-level rise. Ocean warming can melt the floating ice shelves that form in bays and fjords around ice sheets. This lowers the friction with the rocky coast, allowing non-floating ice to flow more rapidly into the ocean and raise the sea level, Alley said.

However, when the climate is warmer, water levels build up beneath the ice and allow it to float higher above the rocks, cutting down on the friction. Researchers have reported that the speed of the ice shelf movement has nearly doubled in recent years.

Rapid ice-shelf melting also leads to sea level rises, Alley said.
The more quickly the ice can enter the sea, causing sea levels to rise. The areas of uncertainty are how much the sea levels will rise and how soon it will happen, the researcher said.

Currently, scientists have projected a range of probabilities about how high and how quickly the seas will rise, Alley said. Now, they are trying to better understand whether sea level rise will happen gradually, like a dial, or abruptly, like a switch, he said.
“If you turn a dial, such as a dimmer on an overhead light, you can change the brightness gradually, but with a switch, it is either on or off,” said Alley.

Most planners expect the sea level to rise gradually. If sea levels do change minimally and slowly, there will still be costs, but people and governments will have more time to deal with the problems — for instance, by building walls and replenishing beaches with sand.

However, if sea levels rise fast and suddenly, the cost to fix the damage and prepare for further problems will increase rapidly, according to Alley.

“If the sea rises faster, then it can be much more expensive,” said Alley. “The prices will go up much faster than the sea levels.”
Alley expects future research projects will help scientists better predict the rate and size of sea level rise.

“The great thing is that this is a wonderful period of discovery and exploration in places like Greenland and the Antarctic,” said Alley. “In the next few year we’ll see even more progress.”

Conference aims to spur development of geothermal production in oil and gas fields

SMU’s renowned Geothermal Lab will host its sixth Geothermal Energy Utilization Conference March 12-14 on the SMU campus in Dallas. Jon Wellinghoff, chairman of the Federal Energy Regulatory Commission, will be the keynote speaker and Doug Hollett, program manager of the U.S. Department of Energy Geothermal Technologies Program, will speak at an evening reception.

The conference will advance the understanding of technology that allows the production of emission-free energy while extending the life of an oil or gas field – developing a sedimentary basin into a total energy solution. The conference (and pre-conference workshop on March 12) bring together leaders from business, engineering, finance, law, and research to explore specific topics relevant to capturing energy that is often overlooked or discarded during oil and gas production.

The same technology that can power oil and gas surface equipment from waste heat (WHP) also is capable of converting waste fluids from oil and gas wells into electrical power. Both technologies have proven applications in oil and gas fields in Mississippi and Wyoming, and WHP installations are widespread in manufacturing.Generating electricity on-site in an oil and/or gas field reduces overall project expenses, eliminates CO2 emissions, decreases dependency on the local electrical grid and may qualify for state Renewable Energy Credits (RECs).

David Blackwell, SMU’s Hamilton Professor of Physics and an internationally recognized expert in geothermal energy, said, “Collaborative research between UT Austin’s Bureau of Economic Geology and SMU’s Geothermal Laboratory has dramatically advanced the understanding of unconventional reservoir thermal capacity within Texas oil and gas fields. The quantities of heat that can be extracted from these reservoirs are more measurable than previously stated, and the estimated pricing of this renewable electricity using geothermal technology drops to below 10 cents per kilowatt-hour with the use of existing oil and gas well sites.

“The next steps are to prove the reservoir fluid flow rates and longevity,” Blackwell said. “The current Texas Legislature session includes geothermal energy related bills, as the legislators now understand that geothermal energy development will be realized in the state.”

Register for the conference and pre-conference workshop at

Separate registration is available at the same site for Wellinghoff’s keynote luncheon for those unable to attend the entire conference. All conference attendees will hear a single track of presentations, with 30-minute breaks designed for networking and team building.

SMU’s Geothermal Laboratory is a national resource for the development of clean, green energy from the Earth’s heat.

Historically, geothermal development was restricted to areas with substantial tectonic activity or volcanism, such as The Geysers field in California. But sophisticated mapping of geothermal resources in recent years directed by Blackwell and Maria Richards, coordinator of SMU’s Geothermal Laboratory, makes it clear that vast geothermal resources reachable through current technology could replace the levels of energy now produced in the United States, mostly by coal-fired power plants.

Recent technological developments are feeding increased geothermal development in areas with little or no tectonic activity or volcanism:

  • Low Temperature Hydrothermal – Energy is produced from subsurface areas with naturally occurring high fluid volumes at temperatures ranging from less than boiling to 300°F (150°C).

  • Geopressure and Coproduced Fluids Geothermal – Oil and/or natural gas are produced together with electricity generated from hot geothermal fluids drawn from the same well.

  • Enhanced Geothermal Systems (EGS) – Subsurface areas with low fluid content but high temperatures are “enhanced” with injection of fluid and other reservoir engineering techniques. EGS resources are typically deeper than hydrothermal resources and represent the largest share of total geothermal resources capable of supporting larger capacity power plants.

Volcano location could be greenhouse-icehouse key

This is Cin-Ty Lee. -  Rice University
This is Cin-Ty Lee. – Rice University

A new Rice University-led study finds the real estate mantra “location, location, location” may also explain one of Earth’s enduring climate mysteries. The study suggests that Earth’s repeated flip-flopping between greenhouse and icehouse states over the past 500 million years may have been driven by the episodic flare-up of volcanoes at key locations where enormous amounts of carbon dioxide are poised for release into the atmosphere.

“We found that Earth’s continents serve as enormous ‘carbonate capacitors,'” said Rice’s Cin-Ty Lee, the lead author of the study in this month’s GeoSphere. “Continents store massive amounts of carbon dioxide in sedimentary carbonates like limestone and marble, and it appears that these reservoirs are tapped from time to time by volcanoes, which release large amounts of carbon dioxide into the atmosphere.”

Lee said as much as 44 percent of carbonates by weight is carbon dioxide. Under most circumstances that carbon stays locked inside Earth’s rigid continental crust.

“One process that can release carbon dioxide from these carbonates is interaction with magma,” he said. “But that rarely happens on Earth today because most volcanoes are located on island arcs, tectonic plate boundaries that don’t contain continental crust.”

Earth’s climate continually cycles between greenhouse and icehouse states, which each last on timescales of 10 million to 100 million years. Icehouse states — like the one Earth has been in for the past 50 million years — are marked by ice at the poles and periods of glacial activity. By contrast, the warmer greenhouse states are marked by increased carbon dioxide in the atmosphere and by an ice-free surface, even at the poles. The last greenhouse period lasted about 50 million to 70 million years and spanned the late Cretaceous, when dinosaurs roamed, and the early Paleogene, when mammals began to diversify.

Lee and colleagues found that the planet’s greenhouse-icehouse oscillations are a natural consequence of plate tectonics. The research showed that tectonic activity drives an episodic flare-up of volcanoes along continental arcs, particularly during periods when oceans are forming and continents are breaking apart. The continental arc volcanoes that arise during these periods are located on the edges of continents, and the magma that rises through the volcanoes releases enormous quantities of carbon dioxide as it passes through layers of carbonates in the continental crust.

Lee, professor of Earth science at Rice, led the four-year study, which was co-authored by three Rice faculty members and additional colleagues at the University of Tokyo, the University of British Columbia, the California Institute of Technology, Texas A&M University and Pomona College.

Lee said the study breaks with conventional theories about greenhouse and icehouse periods.

“The standard view of the greenhouse state is that you draw carbon dioxide from the deep Earth interior by a combination of more activity along the mid-ocean ridges — where tectonic plates spread — and massive breakouts of lava called ‘large igneous provinces,'” Lee said. “Though both of these would produce more carbon dioxide, it is not clear if these processes alone could sustain the atmospheric carbon dioxide that we find in the fossil record during past greenhouses.”

Lee is a petrologist and geochemist whose research interests include the formation and evolution of continents as well as the connections between deep Earth and its oceans and atmosphere..

Lee said the conclusions in the study developed over several years, but the initial idea of the research dates to an informal chalkboard-only seminar at Rice in 2008. The talk was given by Rice oceanographer and study co-author Jerry Dickens, a paleoclimate expert; Lee and Rice geodynamicist Adrian Lenardic, another co-author, were in the audience.

“Jerry was talking about seawater in the Cretaceous, and he mentioned that 93.5 million years ago there was a mass extinction of deepwater organisms that coincided with a global marine anoxic event — that is, the deep oceans became starved of oxygen,” Lee said. “Jerry was talking about the impact of anoxic conditions on the biogeochemical cycles of trace metals in the ocean, but I don’t remember much else that he said that day because it had dawned on me that 93 million years ago was a very interesting time for North America. There was a huge flare-up of volcanism along the western margin of North America, and the peak of all this activity was 93 million years ago.

“I thought, ‘Wow!'” Lee recalled. “I know coincidence doesn’t mean causality, but it certainly got me thinking. I decided to look at whether the flare-up in volcanic activity that helped create the Sierra Nevada Mountains may also have affected Earth’s climate.”

Over the next two years, Lee developed the idea that continental-arc volcanoes could pump carbon dioxide into the atmosphere. One indicator was evidence from Mount Etna in Sicily, one of the few active continental-arc volcanoes in the world today. Etna produces large amounts of carbon dioxide, Lee said, so much that it is often considered an outlier in global averages of modern volcanic carbon dioxide production.

Tectonic and petrological evidence indicated that many Etna-like volcanoes existed during the Cretaceous greenhouse, Lee said. He and colleagues traced the likely areas of occurrence by looking for tungsten-rich minerals like scheelite, which are formed on the margins of volcanic magma chambers when magma reacts with carbonates. It wasn’t easy; Lee spent an entire year pouring through World War II mining surveys from the western U.S. and Canada, for example.

“There is evidence to support our idea, both in the geological record and in geophysical models, the latter of which show plausibility,” he said. For example, in a companion paper published last year in G-Cubed, Lenardic used numerical models that showed the opening and breakup of continents could change the nature of subduction zones, generating oscillations between continental- and island-arc dominated states.

Though the idea in the GeoSpheres study is still a theory, Lee said, it has some advantages over more established theories because it can explain how the same basic set of geophysical conditions could produce and sustain a greenhouse or an icehouse for many millions of years.

“The length of subduction zones and the number of arc volcanoes globally don’t have to change,” Lee said. “But the nature of the arcs themselves, whether they are continental or oceanic, does change. It is in the continental-arc stage that CO2 is released from an ever-growing reservoir of carbonates within the continents.”

Scientists discover how the world’s saltiest pond gets its salt

Antarctica’s Don Juan Pond might be the unlikeliest body of water on Earth. Situated in the frigid McMurdo Dry Valleys, only the pond’s high salt content – by far the highest of any body of water on the planet – keeps it from freezing into oblivion.

Now a research team led by Brown University geologists has discovered how Don Juan Pond gets the salty water it needs to exist.

Using time lapse photography and other data, the researchers show that water sucked out of the atmosphere by parched, salty soil is the source of the saltwater brine that keeps the pond from freezing. Combine that with some fresh water flowing in from melting snow, and you’ve got a pond able to remain fluid in one of the coldest and driest places on Earth. And because of the similarities between the Dry Valleys and the frozen desert of Mars, the findings could have important implications for water flow on the Red Planet both in the past and maybe in the present.

The study, by James Dickson and James Head from Brown, Joseph Levy from Oregon State, and David Marchant from Boston University, is published in Nature Publishing Group’s open access journal, Scientific Reports.

The research represents the most detailed observations ever made of Don Juan Pond. “It was a simple idea,” Dickson said of the team’s approach. “Let’s take 16,000 pictures of this pond over the course of two months and then see which way the water’s flowing. So we took the pictures, correlated them to the other measurements we were taking, and the story told itself.”

What the pictures showed was that water levels in the pond increase in pulses that coincide with daily peaks in temperature, suggesting that the water comes partly from snow warmed just enough by the midday sun to melt. But that influx of fresh water doesn’t explain the pond’s high salt content, which is eight times higher than that of the Dead Sea. For that explanation, the researchers looked to a second source of liquid documented in the photos.

The second source comes from a channel of loose sediment located to the west of the pond. Previous research had found that sediment to be high in calcium chloride salt. To see if that was the source of the pond’s salt, the researchers set up a second time-lapse camera to monitor the channel and synchronized the pictures with data collected from nearby weather stations.

The pictures show dark streaks of moisture called water tracks forming in the soil whenever the relative humidity in the air spiked. Similar water tracks also form on a cliff face north of the pond. What’s forming these tracks is the salt in the soil absorbing any available moisture in the air, a process known as deliquescence. Those water-laden salts then trickle down through the loose soil until they reach the permafrost layer below. There they sit until the occasional flow of snowmelt washes the salts down the channel and into the pond.

When the team saw how closely correlated the appearance of water tracks was to their humidity readings, they knew the tracks were the result of deliquescence and that the process was key to keeping the pond salty enough to persist.

The findings refute the dominant interpretation of Don Juan Pond’s origin. Since the pond’s discovery in 1961, most researchers had agreed that its briney waters must be supplied mainly from deep in the ground. However, these new images show no evidence at all that groundwater contributes to the pond.

Implication for Mars

Head and Dickson mainly study the geology of bodies other than Earth, so they approach Antarctica as a model for the cold, dry desert of Mars. What they have learned about Don Juan Pond could tell us something about the possibilities for flowing water on Mars, both in the past and in the present.

The images of water tracks at Don Juan Pond look a lot like features recently imaged on Mars called recurring slope lineae, the researchers say. The features appear on Mars as dark streaks that seem to flow downslope on cliff faces. They often recur in the same places at the same times of year, hence their name. Some scientists believe these streaks indicate some kind of flowing brine, the best evidence yet that there might be flowing water on present day Mars.

The research in Antarctica strengthens the view that these lineae on Mars are indeed formed by flowing brine. Frost has been observed on Mars, suggesting that the atmosphere contains at least a little water vapor. There have also been chloride-bearing salts detected on Mars, which would be capable of the same kind deliquescence seen in Antarctica. And importantly, the processes at Don Juan Pond require no groundwater, which is not thought to exist currently on Mars.

“Broadly speaking, all the ingredients are there for a Don Juan Pond-type hydrology on Mars,” Dickson said. It’s not likely that there’s enough water currently on Mars for the water to form ponds, but stronger flows in Mars’s past might have formed plenty of Don Juan Ponds.

“Don Juan Pond is a closed basin pond and we just documented a couple hundred closed basins on Mars,” Head said. “So what we found in Antarctica may be a key to how lakes worked on early Mars and also how moisture may flow on the surface today.”

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Antarctica’s Don Juan Pond, the world’s saltiest body of water, needs its salt to keep from freezing into oblivion. Scientists had assumed that the saltwater brine that sustains the pond must come from groundwater. But using time-lapse photography, Brown University researchers show the pond actually gets its water from snowmelt, and its salt from nearby surface sediment. The video shows pond levels increasing in daily pulses correlated with peaks in surface temperature (charted on the right), a sure signal that the water comes from melting snow. The saltwater is seen entering the pond from the west. The hydrology of a pond in one of the coldest and driest places on Earth could shed light on the potential for flowing water on Mars. – Head Lab/Brown University/Nature Scientific Reports

New report in Science illuminates stress change during the 2011 Tohoku-Oki earthquake

The 11 March 2011 Tohoku-Oki earthquake (Mw9.0) produced the largest slip ever recorded in an earthquake, over 50 meters. Such huge fault movement on the shallow portion of the megathrust boundary came as a surprise to seismologists because this portion of the subduction zone was not thought to be accumulating stress prior to the earthquake. In a recently published study, scientists from the Integrated Ocean Drilling Program (IODP) shed light on the stress state on the fault that controls the very large slip. The unexpectedly large fault displacements resulted in the devastating tsunamis that caused tremendous damage and loss of lives along the coast of Japan. The study, published in 8 February 2013 issue of the journal Science, presents compelling evidence that large slips are the results of a complete stress drop during the earthquake. These new findings from IODP Japan Trench Fast Drilling Project (JFAST) research are relevant to better understanding earthquakes and tsunamis in many areas of the world.

“The study investigated the stress change associated with the 2011 Tohoku-Oki earthquake and tested the hypothesis by determining the in-situ stress state of the frontal prism from the drilled holes,” says a lead author Weiren Lin of Japan Agency for Marine-Earth Science and Technology (JAMSTEC). “We have established a new framework that the large slips in this region are an indication of coseismic fault zone and nearly the total stress accumulated was released during the earthquake.”

JFAST was designed and undertaken by the international scientific community to better understand the 2011 Tohoku-oki earthquake. The expedition was carried out aboard the scientific drilling vessel Chikyu from April to July 2012. JFAST drill sites were located approximately 220 km from the eastern coast of Honshu, Japan, in nearly 7000 m of water.

“The project is looking at the stress and physical properties of the fault zone soon after a large earthquake,” co-author James Mori of Kyoto University, Co-Chief Scientist who led the JFAST expedition explains.

It is the first time that “rapid-response drilling” (within 13 months after the earthquake) has been attempted to measure the temperature across a subduction fault zone. The fast mobilization is necessary to observe time sensitive data, such as the temperature signal. JAMSTEC successfully mobilized a research expedition for IODP to investigate the large displacement by drilling from the ocean floor to the plate boundary, reaching a maximum depth of more than 850 m below seafloor (mbsf).

“Understanding the stress conditions that control the very large slip of this shallow portion of the megathrust may be the most important seismological issue for this earthquake.” Mori says.

The research published this week determined the stress field from breakouts observed in a borehole around 820 mbsf, in a region thought to contain the main slip zone of the 2011 earthquake. Lin and his co-authors analyzed a suite of borehole-logging data collected while drilling with Logging-While-Drilling (LWD) tools during IODP Expedition 343. Local compressive failures (borehole breakouts) are formed in the borehole wall during the drilling and are imaged with the LWD tools. The orientation and size of the breakouts are used to infer the present direction and magnitudes of the stress field. An important finding of the paper is that the present shear stress on the fault is nearly zero, indicating that there was a nearly complete stress change during the earthquake. Usually, earthquakes are thought to release only a portion of the stress on the fault.

“This was the first time for such nearly complete stress change has been recognized by direct measurement in drilling through the ruptured fault. This is the first time direct stress measurements have been reported, a little over a year after a great subduction zone earthquake.” Lin says.

The expedition set new milestones in scientific ocean drilling by drilling a borehole to 854.81 mbsf in water depths of 6897.5 meters. Deep core was obtained and analyzed from this depth. The Japan Trench plate boundary was sampled and a parallel borehole was instrumented with a borehole observatory system. The core samples and borehole observatory provide scientists with valuable opportunities to learn about residual heat, coseismic frictional stress, fluid and rock properties, and other factors related to megathrust earthquakes.

“We will be able to address very fundamental and important questions about the physics of slip of the thrust near the trench, and how to identify past events in the rock record.” says Frederick Chester, Texas A&M University, co-author of the Science report and the other expedition Co-Chief Scientist.

The expedition science party, comprising both ship-board and shore-based scientists, is conducting further investigations of core samples and borehole logging data. Data from the borehole observatory are expected to be retrieved later this month using the JAMSTEC ROV Kaiko7000II, and those data will be combined with the current results to continue to increase understanding of the processes involved in this large slip earthquake.

“We anticipate that the results from the JFAST expedition will provide us with a better understanding of the faulting mechanisms for this critical location,” says Mori. “Investigations and research findings from the expedition have obvious consequences for evaluating future tsunami hazards at other subduction zones around the world, such as the Nankai Trough in Japan and Cascadia in the Pacific of North America.”

Shimmering water reveals cold volcanic vent in Antarctic waters

The image, taken by SHRIMP, shows the small relict chimney (around two meters high) found on the seafloor at Hook Ridge at a depth of around 1,200 meters. Emanating hydrothermal fluid is visible as shimmering water. Image courtesy of the National Oceanography Centre, Southampton. -  Image courtesy of National Oceanography Centre, Southampton
The image, taken by SHRIMP, shows the small relict chimney (around two meters high) found on the seafloor at Hook Ridge at a depth of around 1,200 meters. Emanating hydrothermal fluid is visible as shimmering water. Image courtesy of the National Oceanography Centre, Southampton. – Image courtesy of National Oceanography Centre, Southampton

The location of an underwater volcanic vent, marked by a low-lying plume of shimmering water, has been revealed by scientists at the National Oceanography Centre, Southampton.

Writing in the journal PLOS ONE the researchers describe how the vent, discovered in a remote region of the Southern Ocean, differs from what we have come to recognise as “classic” hydrothermal vents. Using SHRIMP, the National Oceanography Centre’s high resolution deep-towed camera platform, scientists imaged the seafloor at Hook Ridge, more than 1,000 metres deep.

The study, funded by the Natural Environment Research Council (NERC), aimed to build on our knowledge of how deep-sea creatures associated with hydrothermal activity evolve and migrate between different regions.

Hydrothermal vents are like hot springs, spewing jets of water from the seafloor out into the ocean. The expelled water, if hot enough, is rich in dissolved metals and other chemicals that can nourish a host of strange-looking life, via a process called “chemosynthesis”. The hot water, being more buoyant than the surrounding cold seawater, rises up like a fountain or “plume”, spreading the chemical signature up and out from the source.

The Hook Ridge vent, however, was found to lack the high temperatures and alien-like creatures that we now associate with hot hydrothermal vents. Instead there was a low-lying plume of shimmering water, caused by differences relative to the surrounding seawater in certain properties, such as salinity.

“Geochemical measurements of the water column provided evidence of slightly reducing, localized plumes close to the seafloor at Hook Ridge,” said Dr Alfred Aquilina, lead author and former research fellow at University of Southampton Ocean and Earth Science, which is based at the center.

“We therefore went in with sled-mounted cameras towed behind the Royal Research Ship James Cook and saw shimmering water above the seafloor, evidence of hydrothermal fluid seeping through the sediment.”

So why were there no strange creatures around the vent? The team investigated this particular area of the deep-sea because prior measurements of the water column above Hook Ridge detected chemical changes consistent with a hydrothermal plume. On investigation, there was also a small relict “chimney” of precipitated minerals on the seafloor, which suggests that the hydrothermal fluid flowing from the vent was once warmer.

The researchers therefore propose that hydrothermal activity at Hook Ridge is too irregular to provide the vital chemicals that support chemosynthetic life.

Dr Aquilina explained why this was an important finding: “This region was investigated because hydrothermal systems in this part of the Southern Ocean may potentially act as stepping stones for genetic material migrating between separate areas in the world ocean,” he said.

“The more hydrothermal vents we can find and investigate, the more we can understand about the evolution and dispersal of the creatures that live off the chemicals expelled in these dark, deep environments.”