Plankton key to origin of Earth’s first breathable atmosphere

Researchers studying the origin of Earth’s first breathable atmosphere have zeroed in on the major role played by some very unassuming creatures: plankton.

In a paper to appear in the online Early Edition of the Proceedings of the National Academy of Sciences (PNAS), Ohio State University researcher Matthew Saltzman and his colleagues show how plankton provided a critical link between the atmosphere and chemical isotopes stored in rocks 500 million years ago.

This work builds on the team’s earlier discovery that upheavals in the earth’s crust initiated a kind of reverse-greenhouse effect 500 million years ago that cooled the world’s oceans, spawned giant plankton blooms, and sent a burst of oxygen into the atmosphere.

The new study has revealed details as to how oxygen came to vanish from Earth’s ancient atmosphere during the Cambrian Period, only to return at higher levels than ever before.

It also hints at how, after mass extinctions, the returning oxygen allowed enormous amounts of new life to flourish.

Saltzman and his team were able to quantify how much oxygen was released into the atmosphere at the time, and directly link the amount of sulfur in the ancient oceans with atmospheric oxygen and carbon dioxide.

The result is a clearer picture of life on Earth in a time of extreme turmoil.

“We know that oxygen levels in the ocean dropped dramatically [a condition called anoxia] during the Cambrian, and that coincides with the time of a global extinction,” said Saltzman, associate professor of earth sciences at Ohio State.

In a paper in the journal Nature just last month, the same researchers presented the first geochemical evidence that the anoxia spread even to the world’s shallow waters.

“We still don’t know why the anoxia spread all over the world. We may never know,” Saltzman said. “But there have been many other extinction events in Earth’s history, and with the exception of those caused by meteor impacts, others likely share elements of this one – changes in the balance of oxygen and carbon dioxide in the atmosphere and oceans.”

“By getting a handle on what was happening back then, we may improve our understanding of what’s happening to the atmosphere now.”

Something enabled oxygen to re-enter the oceans and the atmosphere 500 million years ago, and the study suggests that the tiny plant and animal life forms known as plankton were key.

Plankton may be at the bottom our food chain today, but back then, they ruled the planet. There was no life on land at all. And aside from an abundance of trilobites, life in the oceans was not very diverse.

Not diverse, that is, until a geologic event that scientists call the Steptoean Positive Carbon Isotope Excursion (SPICE) occurred. In previous work, Saltzman and his collaborators showed that the SPICE event was caused by the burial of huge quantities of organic matter in ocean sediments, which pulled carbon dioxide from the atmosphere and released oxygen.

The more oxygen plankton encounter in their cells, the more selective they become for the light isotope of carbon in carbon dioxide, and absorb it into their bodies.

By studying isotopes in fossilized plankton contained in rocks found in the central United States, the Australian outback, and China, the researchers determined that the SPICE event happened around the same time as an explosion of plankton diversity known as the “plankton revolution.”

“The amount of oxygen rebounded, and so did the diversity of life,” Saltzman explained.

Other researchers have tried to gauge how much oxygen was in the air during the Cambrian, but their estimates have varied widely, from a few percent to as much as 15-20 percent.

If the higher estimates were correct, then the SPICE event would have boosted oxygen content to greater than 30 percent – or almost 50 percent richer than today’s standard of 21 percent.

This study has provided a new perspective on the matter.

“We were able to bring together independent lines of evidence that showed that if the total oxygen content was around 5-10 percent before the SPICE, then it rose to just above modern levels for the first time after the SPICE,” Saltzman said.

The study has some relevance to modern geoengineering. Scientists have begun to investigate what we can do to forestall climate change, and altering the chemistry of the oceans could help remove carbon dioxide and restore balance to the atmosphere.
The ancient and humble plankton would be a necessary part of that equation, he added.

“When it comes to ancient life, they don’t sound as exciting as dinosaurs, but the plankton are critical to this story.”

The world’s oldest water?

New evidence bolsters the notion that deep saline groundwaters in South Africa’s Witwatersrand Basin may have remained isolated for many thousands, perhaps even millions, of years.

The study, recently accepted for publication in Chemical Geology, found the noble gas neon dissolved in water in three-kilometre deep crevices.

The unusual neon profile, along with the high salinities and some other unique chemical signatures, is very different from anything seen in molten fluid and gases rising from beneath the Earth’s crust, according to University of Toronto professor Barbara Sherwood Lollar, who is the Canadian member of the international team that produced the results.

“The chemical signatures also don’t match those of ocean water or waters higher up in the Witwatersrand Basin, where as in most regions of the crust ground waters show evidence of mixing with surface waters and are extensively colonized by microorganisms,” she said. “We concluded that the deeper waters were the product of isolation and extensive chemical interaction between water and rock over incredibly long geological time scales.”

The smoking gun was the ancient basement rock.

“We know that this specific neon isotope signature was produced and trapped within the rock at least two billion years ago. We can still find it there today,” Dr. Sherwood Lollar said. “The study shows some of the neon found its way outside of the rock minerals, gradually dissolving into, and accumulating in, fluids in crevices. This could only happen in waters that have indeed been cut off from the surface for extremely long time periods.”

The discovery adds yet another dimension to what has only recently been recognized as a truly unique environment.

One of these fracture systems contains the deepest known microbial ecosystems on Earth. These are organisms that eke out an existence independent from sunlight on chemical energy that originates from rock.

“These deep microbial communities radically expand our concept of the habitability of the Earth’s subsurface and, indeed, our biosphere,” said Dr. Sherwood Lollar.

“Given that they have a genetic similarity to organisms found at hydrothermal vents, we assume this is not a separate origin of life, but instead these organisms arrived from elsewhere to colonize these rocks in ancient times,” she said.

“Clearly the long period of isolation affected their evolution. This is one area we hope to explore with continuing research with our microbiology colleagues.”

The lead author of the paper is Johanna Lippmann-Pipke of the Helmholtz-Zentrum Dresden-Rossendorf in Leipzig, Germany. Researchers from that country, South Africa, the United States and Canada participated in the study.

Dr. Sherwood Lollar will be available to discuss the new findings at this year’s meeting of the American Association for the Advancement of Science (AAAS) in Washington, DC. On Sunday, February 20, she will take part in a panel discussion on global water issues at the Think Canada Press Breakfast.

Earth’s core rotating faster than rest of the planet but slower than previously believed

New research gives the first accurate estimate of how much faster the Earth’s core is rotating compared to the rest of the planet.

Previous research had shown that the Earth’s core rotates faster than the rest of the planet. However, scientists from the University of Cambridge have discovered that earlier estimates of 1 degree every year were inaccurate and that the core is actually moving much slower than previously believed – approximately 1 degree every million years. Their findings are published today, Sunday 20 February, in the journal Nature Geoscience.

The inner core grows very slowly over time as material from the fluid outer core solidifies onto its surface. During this process, an east-west hemispherical difference in velocity is frozen into the structure of the inner core.

“The faster rotation rates are incompatible with the observed hemispheres in the inner core because it would not allow enough time for the differences to freeze into the structure,” said Lauren Waszek, first author on the paper and a PhD student from the University of Cambridge’s Department of Earth Sciences. “This has previously been a major problem, as the two properties cannot coexist. However, we derived the rotation rates from the evolution of the hemispherical structure, and thus our study is the first in which the hemispheres and rotation are inherently compatible.”

For the research, the scientists used seismic body waves which pass through the inner core – 5200km beneath the surface of the Earth – and compared their travel time to waves which reflect from the inner core surface. The difference between the travel times of these waves provided them with the velocity structure of the uppermost 90 km of the inner core.

They then had to reconcile this information with the differences in velocity for the east and west hemispheres of the inner core. First, they observed the east and west hemispherical differences in velocity. They then constrained the two boundaries which separate the hemispheres and found that they both shifted consistently eastward with depth. Because the inner core grows over time the deeper structure is therefore older, and the shift in the boundaries between the two hemispheres results in the inner core rotating with time. The rotation rate is therefore calculated from the shift of the boundaries and the growth rate of the inner core.

Although the inner core is 5200km beneath our feet, the effect of its presence is especially important on the Earth’s surface. In particular, as the inner core grows, the heat released during solidification drives convection in the fluid in the outer core. This convection generates the Earth’s geomagnetic field. Without our magnetic field, the surface would not be protected from solar radiation, and life on Earth would not be able to exist.

“This result is the first observation of such a slow inner core rotation rate,” said Waszek “It therefore provides a confirmed value which can now be used in simulations to model the convection of the Earth’s fluid outer core, giving us additional insight into the evolution of our magnetic field.”

Magma power for geothermal energy?

When a team of scientists drilling near an Icelandic volcano hit magma in 2009, they had to abandon their planned experiments on geothermal energy. But the mishap could point the way to an alternative source of geothermal power.

“Because we drilled into magma, this borehole could now be a really high-quality geothermal well,” said Peter Schiffmann, professor of geology at UC Davis and a member of the research team along with fellow UC Davis geology professor Robert Zierenberg and UC Davis graduate student Naomi Marks. The project was led by Wilfred Elders, a geology professor at UC Riverside.

A paper describing geological results from the well was published this month in the journal Geology.

When tested, the magma well produced dry steam at 750 degrees Fahrenheit (400 degrees Celsius). The team estimated that this steam could generate up to 25 megawatts of electricity — enough to power 25,000 to 30,000 homes.

That compares to 5 to 8 megawatts produced by a typical geothermal well, Elders said. Iceland already gets about one-third of its electricity and almost all of its home heating from geothermal sources.

The team was drilling into the Krafla caldera as part of the Iceland Deep Drilling Project, an industry-government consortium, to test whether “supercritical” water — very hot water under very high pressure — could be exploited as a source of power.

They planned to drill to 15,000 feet — more than two miles deep– but at 6,900 feet, magma (molten rock from the Earth’s core) flowed into the well, forcing them to stop.

The composition of magma from the borehole is also providing insight into how magmas form beneath Iceland, Schiffmann said.

Thawing permafrost likely will accelerate global warming

Up to two-thirds of Earth's permafrost likely will disappear by 2200 as a result of warming temperatures, unleashing vast quantities of carbon into the atmosphere, says a new study by the University of Colorado Boulder's Cooperative Institute for Research in Environmental Sciences. -  University of Colorado
Up to two-thirds of Earth’s permafrost likely will disappear by 2200 as a result of warming temperatures, unleashing vast quantities of carbon into the atmosphere, says a new study by the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences. – University of Colorado

Up to two-thirds of Earth’s permafrost likely will disappear by 2200 as a result of warming temperatures, unleashing vast quantities of carbon into the atmosphere, says a new study by the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences.

The carbon resides in permanently frozen ground that is beginning to thaw in high latitudes from warming temperatures, which will impact not only the climate but also international strategies to reduce fossil fuel emissions, said CU-Boulder’s Kevin Schaefer, lead study author. “If we want to hit a target carbon dioxide concentration, then we have to reduce fossil fuel emissions that much lower than previously thought to account for this additional carbon from the permafrost,” he said. “Otherwise we will end up with a warmer Earth than we want.”

The escaping carbon comes from plant material, primarily roots trapped and frozen in soil during the last glacial period that ended roughly 12,000 years ago, he said. Schaefer, a research associate at CU-Boulder’s National Snow and Ice Data Center, an arm of CIRES, likened the mechanism to storing broccoli in a home freezer. “As long as it stays frozen, it stays stable for many years,” he said. “But if you take it out of the freezer it will thaw out and decay.”

While other studies have shown carbon has begun to leak out of permafrost in Alaska and Siberia, the study by Schaefer and his colleagues is the first to make actual estimates of future carbon release from permafrost. “This gives us a starting point, and something more solid to work from in future studies,” he said. “We now have some estimated numbers and dates to work with.”

The new study was published online Feb. 14 in the scientific journal Tellus. Co-authors include CIRES Fellow and Senior Research Scientist Tingjun Zhang from NSIDC, Lori Bruhwiler of the National Oceanic and Atmospheric Administration and Andrew Barrett from NSIDC. Funding for the project came from NASA, NOAA and the National Science Foundation.

Schaefer and his team ran multiple Arctic simulations assuming different rates of temperature increases to forecast how much carbon may be released globally from permafrost in the next two centuries. They estimate a release of roughly 190 billion tons of carbon, most of it in the next 100 years. The team used Intergovernmental Panel on Climate Change scenarios and land-surface models for the study.

“The amount we expect to be released by permafrost is equivalent to half of the amount of carbon released since the dawn of the Industrial Age,” said Schaefer. The amount of carbon predicted for release between now and 2200 is about one-fifth of the total amount of carbon in the atmosphere today, according to the study.

While there were about 280 parts per million of CO2 in Earth’s atmosphere prior to the Industrial Age beginning about 1820, there are more than 380 parts per million of carbon now in the atmosphere and the figure is rising. The increase, equivalent to about 435 billion tons of carbon, resulted primarily from human activities like the burning of fossil fuels and deforestation.

Using data from all climate simulations, the team estimated that about 30 to 60 percent of Earth’s permafrost will disappear by 2200. The study took into account all of the permanently frozen ground at high latitudes around the globe.

The consensus of the vast majority of climate scientists is that the buildup of CO2 and other greenhouse gases in Earth’s atmosphere is the primary reason for increasingly warm temperatures on Earth. According to NOAA, 2010 was tied for the hottest year on record. The hottest decade on record occurred from 2000 to 2010.

Greater reductions in fossil fuel emissions to account for carbon released by the permafrost will be a daunting global challenge, Schaefer said. “The problem is getting more and more difficult all the time,” he said. “It is hard enough to reduce the emissions in any case, but now we have to reduce emissions even more. We think it is important to get that message out now.”

Geologists get unique and unexpected opportunity to study magma

This is a view of the exploratory geothermal well during flow testing. -  Bjarni Palssen.
This is a view of the exploratory geothermal well during flow testing. – Bjarni Palssen.

Geologists drilling an exploratory geothermal well in 2009 in the Krafla volcano in Iceland encountered a problem they were simply unprepared for: magma (molten rock or lava underground) which flowed unexpectedly into the well at 2.1 kilometers (6,900 ft) depth, forcing the researchers to terminate the drilling.

“To the best of our knowledge, only one previous instance of magma flowing into a geothermal well while drilling has been documented,” said Wilfred Elders, a professor emeritus of geology in the Department of Earth Sciences at the University of California, Riverside, who led the research team. “We were drilling a well that was designed to search for very deep – 4.5 kilometers (15,000 feet) – geothermal resources in the volcano. While the magma flow interrupted our project, it gave us a unique opportunity to study the magma and test a very hot geothermal system as an energy source.”

Currently, a third of the electric power and 95 percent of home heating in Iceland is produced from steam and hot water that occurs naturally in volcanic rocks.

“The economics of generating electric power from such geothermal steam improves the higher its temperature and pressure,” Elders explained. “As you drill deeper into a hot zone the temperature and pressure rise, so it should be possible to reach an environment where a denser fluid with very high heat content, but also with unusually low viscosity occurs, so-called ‘supercritical water.’ Although such supercritical water is used in large coal-fired electric power plants, no one had tried to use supercritical water that should occur naturally in the deeper zones of geothermal areas.”

Elders and colleagues report in the March issue of Geology (the research paper was published online on Feb. 3) that although the Krafla volcano, like all other volcanoes in Iceland, is basaltic (a volcanic rock containing 45-50 percent silica), the magma they encountered is a rhyolite (a volcanic rock containing 65-70 percent silica).

“Our analyses show that this magma formed by partial melting of certain basalts within the Krafla volcano,” Elders said. “The occurrence of minor amounts of rhyolite in some basalt volcanoes has always been something of a puzzle. It had been inferred that some unknown process in the source area of magmas, in the mantle deep below the crust of the Earth, allows some silica-rich rhyolite melt to form in addition to the dominant silica-poor basalt magma.”

Elders explained that in geothermal systems water reacts with and alters the composition of the rocks, a process termed “hydrothermal alteration.” “Our research shows that the rhyolite formed when a mantle-derived basaltic magma encountered hydrothermally altered basalt, and partially melted and assimilated that rock,” he said.

Elders and his team studied the well within the Krafla caldera as part of the Iceland Deep Drilling Project, an industry-government consortium, to test whether geothermal fluids at supercritical pressures and temperatures could be exploited as sources of power. Elders’s research team received support of $3.5 million from the National Science Foundation and $1.5 million from the International Continental Scientific Drilling Program.

In the spring of 2009 Elders and his colleagues progressed normally with drilling the well to 2 kilometers (6,600 feet) depth. In the next 100 meters (330 feet), however, multiple acute drilling problems occurred. In June 2009, the drillers determined that at 2104 meters (6,900 feet) depth, the rate of penetration suddenly increased and the torque on the drilling assembly increased, halting its rotation. When the drill string was pulled up more than 10 meters (33 feet) and lowered again, the drill bit became stuck at 2095 meters (6,875 feet). An intrusion of magma had filled the lowest 9 meters (30 feet) of the open borehole. The team terminated the drilling and completed the hole as a production well.

“When the well was tested, high pressure dry steam flowed to the surface with a temperature of 400 Celsius or 750 Fahrenheit, coming from a depth shallower than the magma,” Elders said. “We estimated that this steam could generate 25 megawatts of electricity if passed through a suitable turbine, which is enough electricity to power 25,000 to 30,000 homes. What makes this well an attractive source of energy is that typical high-temperature geothermal wells produce only 5 to 8 megawatts of electricity from 300 Celsius or 570 Fahrenheit wet steam.”

Elders believes it should be possible to find reasonably shallow bodies of magma, elsewhere in Iceland and the world, wherever young volcanic rocks occur.

“In the future these could become attractive sources of high-grade energy,” said Elders, who got involved in the project in 2000 when a group of Icelandic engineers and scientists invited him to join them to explore concepts of developing geothermal energy.

The Iceland Deep Drilling Project has not abandoned the search for supercritical geothermal resources. The project plans to drill a second deep hole in southwest Iceland in 2013.

Scientists delve into ‘hotspot’ volcanoes along Pacific Ocean Seamount Trail

Like a string of underwater pearls, the Louisville Seamount Trail is strung across the Pacific. -  IODP
Like a string of underwater pearls, the Louisville Seamount Trail is strung across the Pacific. – IODP

Nearly half a mile of rock retrieved from beneath the seafloor is yielding new clues about how underwater volcanoes are created and whether the hotspots that led to their formation have moved over time.

Geoscientists have just completed an expedition to a string of underwater volcanoes, or seamounts, in the Pacific Ocean known as the Louisville Seamount Trail.

There they collected samples of sediments, basalt lava flows and other volcanic eruption materials to piece together the history of this ancient trail of volcanoes.

The expedition was part of the Integrated Ocean Drilling Program (IODP).

“Finding out whether hotspots in Earth’s mantle are stationary or not will lead to new knowledge about the basic workings of our planet,” says Rodey Batiza, section head for marine geosciences in the National Science Foundation’s (NSF) Division of Ocean Sciences.

Tens of thousands of seamounts exist in the Pacific Ocean. Expedition scientists probed a handful of the most important of these underwater volcanoes.

“We sampled ancient lava flows, and a fossilized algal reef,” says Anthony Koppers of Oregon State University. “The samples will be used to study the construction and evolution of individual volcanoes.”

Koppers led the expedition aboard the scientific research vessel JOIDES Resolution, along with co-chief scientist Toshitsugu Yamazaki from the Geological Survey of Japan at the National Institute of Advanced Industrial Science and Technology.

IODP is supported by NSF and Japan’s Ministry of Education, Culture, Sports, Science and Technology.

Over the last two months, scientists drilled 1,113 meters (3,651 feet) into the seafloor to recover 806 meters (2,644 feet) of volcanic rock.

The samples were retrieved from six sites at five seamounts ranging in age from 50 to 80 million years old.

“The sample recovery during this expedition was truly exceptional. I believe we broke the record for drilling igneous rock with a rotary core barrel,” says Yamazaki.

Igneous rock is rock formed through the cooling and solidification of magma or lava, while a rotary core barrel is a type of drilling tool used for penetrating hard rocks.

Trails of volcanoes found in the middle of tectonic plates, such as the Hawaii-Emperor and Louisville Seamount Trails, are believed to form from hotspots–plumes of hot material found deep within the Earth that supply a steady stream of heated rock.

As a tectonic plate drifts over a hotspot, new volcanoes are formed and old ones become extinct. Over time, a trail of volcanoes is formed. The Louisville Seamount Trail is some 4,300 kilometers (about 2,600 miles) long.

“Submarine volcanic trails like the Louisville Seamount Trail are unique because they record the direction and speed at which tectonic plates move,” says Koppers.

Scientists use these volcanoes to study the motion of tectonic plates, comparing the ages of the volcanoes against their location over time to calculate the rate at which a plate moved over a hotspot.

These calculations assume the hotspot stays in the same place.

“The challenge,” says Koppers, “is that no one knows if hotspots are truly stationary or if they somehow wander over time. If they wander, then our calculations of plate direction and speed need to be re-evaluated.”

“More importantly,” he says, “the results of this expedition will give us a more accurate picture of the dynamic nature of the interior of the Earth on a planetary scale.”

Recent studies in Hawaii have shown that the Hawaii hotspot may have moved as much as 15 degrees latitude (about 1,600 kilometers or 1,000 miles) over a period of 30 million years.

“We want to know if the Louisville hotspot moved at the same time and in the same direction as the Hawaiian hotspot. Our models suggest that it’s the opposite, but we won’t really know until we analyze the samples from this expedition,” says Yamazaki.

In addition to the volcanic rock, the scientists also recovered sedimentary rocks that preserve shells and an ancient algal reef, typical of living conditions in a very shallow marine environment.

These ancient materials show that the Louisville seamounts were once an archipelago of volcanic islands.

“We were really surprised to find only a thin layer of sediments on the tops of the seamounts, and only very few indications for the eruption of lava flows above sea level,” says Koppers.

The IODP Louisville Seamount Trail Expedition wasn’t solely focused on geology.

More than 60 samples from five seamounts were obtained for microbiology research.

Exploration of microbial communities under the seafloor, known as the “subseafloor biosphere,” is a rapidly developing field of research.

Using the Louisville samples, microbiologists will study both living microbial residents and those that were abundant over a large area, but now occupy only a few small areas.

They will examine population differences in microbes in the volcanic rock and overlying sediments, and in different kinds of lava flows.

They will also look for population patterns at various depths in the seafloor and compare them with seamounts of varying ages.

Samples from the Louisville Seamount Trail expedition will be analyzed to determine their age, composition and magnetic properties.

The information will be pieced together like a puzzle to create a story of the eruption history of the Louisville volcanoes.

It will then be compared to that of the Hawaiian volcanoes to determine whether hotspots are on the move.

The IODP is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring and monitoring the subseafloor.

Ground-based lasers vie with satellites to map Earth’s magnetic field

To measure the Earth's magnetic field, an orange laser beam is directed at a layer of sodium 90 kilometers above the Earth. The beam is pulsed at a rate determined by the local magnetic field in order to excite spin polarization of the sodium atoms. The fluorescent emission from the sodium, which depends on the spin polarization, is detected by a ground-based telescope and analyzed to determine the strength of the magnetic field. -  Dmitry Budker lab/UC Berkeley
To measure the Earth’s magnetic field, an orange laser beam is directed at a layer of sodium 90 kilometers above the Earth. The beam is pulsed at a rate determined by the local magnetic field in order to excite spin polarization of the sodium atoms. The fluorescent emission from the sodium, which depends on the spin polarization, is detected by a ground-based telescope and analyzed to determine the strength of the magnetic field. – Dmitry Budker lab/UC Berkeley

Mapping the Earth’s magnetic field – to find oil, track storms or probe the planet’s interior – typically requires expensive satellites.

University of California, Berkeley, physicists have now come up with a much cheaper way to measure the Earth’s magnetic field using only a ground-based laser.

The method involves exciting sodium atoms in a layer 90 kilometers above the surface and measuring the light they give off.

“Normally, the laser makes the sodium atom fluoresce,” said Dmitry Budker, UC Berkeley professor of physics. “But if you modulate the laser light, when the modulation frequency matches the spin precession of the sodium atoms, the brightness of the spot changes.”

Because the local magnetic field determines the frequency at which the atoms precess, this allows someone with a ground-based laser to map the magnetic field anywhere on Earth.

Budker and three current and former members of his laboratory, as well as colleagues with the European Southern Observatory (ESO), lay out their technique in a paper appearing online this week in the journal Proceedings of the National Academy of Sciences.

Various satellites, ranging from the Geostationary Operational Environmental Satellites, or GOES, to an upcoming European mission called SWARM, carry instruments to measure the Earth’s magnetic field, providing data to companies searching for oil or minerals, climatologists tracking currents in the atmosphere and oceans, geophysicists studying the planet’s interior and scientists tracking space weather.

Ground-based measurements, however, can avoid several problems associated with satellites, Budker said. Because these spacecraft are moving at high speed, it’s not always possible to tell whether a fluctuation in the magnetic field strength is real or a result of the spacecraft having moved to a new location. Also, metal and electronic instruments aboard the craft can affect magnetic field measurements.

“A ground-based remote sensing system allows you to measure when and where you want and avoids problems of spatial and temporal dependence caused by satellite movement,” he said. “Initially, this is going to be competitive with the best satellite measurements, but it could be improved drastically.”

Laser guide stars

The idea was sparked by a discussion Budker had with a colleague about of the lasers used by many modern telescopes to remove the twinkle from stars caused by atmospheric disturbance. That technique, called laser guide star adaptive optics, employs lasers to excite sodium atoms deposited in the upper atmosphere by meteorites. Once excited, the atoms fluoresce, emitting light that mimics a real star. Telescopes with such a laser guide star, including the Very Large Telescope in Chile and the Keck telescopes in Hawaii, adjust their “rubber mirrors” to cancel the laser guide star’s jiggle, and thus remove the jiggle for all nearby stars.

It is well known that these sodium atoms are affected by the Earth’s magnetic field. Budker, who specializes in extremely precise magnetic-field measurements, realized that you could easily determine the local magnetic field by exciting the atoms with a pulsed or modulated laser of the type used in guide stars. The method is based on the fact that the electron spin of each sodium atom precesses like a top in the presence of a magnetic field. Hitting the atom with light pulses at just the right frequency will cause the electrons to flip, affecting the way the atoms interact with light.

“It suddenly struck me that what we do in my lab with atomic magnetometers we can do with atoms freely floating in the sky,” he said.

Budker’s former post-doctoral fellow James Higbienow an assistant professor of physics and astronomy at Bucknell University – conducted laboratory measurements and computer simulations confirming that the effects of a modulated laser could be detected from the ground by a small telescope. He was assisted by Simon M. Rochester, who received his Ph.D. in physics from UC Berkeley last year, and current post-doctoral fellow Brian Patton.

Portable laser magnetometers

In practice, a 20- to 50-watt laser small enough to load on a truck or be attuned to the orange sodium line (589 nanometer wavelength) would shine polarized light into the 10 kilometer-thick sodium layer in the mesosphere, which is about 90 kilometers overhead. The frequency with which the laser light is modulated or pulsed would be shifted slightly around this wavelength to stimulate a spin flip.

The decrease or increase in brightness when the modulation is tuned to a “sweet spot” determined by the magnitude of the magnetic field could be as much as 10 percent of the typical fluorescence, Budker said. The spot itself would be too faint to see with the naked eye, but the brightness change could easily be measured by a small telescope.

“This is such a simple idea, I thought somebody must have thought of it before,” Budker said.

He was right. William Happer, a physicist who pioneered spin-polarized spectroscopy and the sodium laser guide stars, had thought of the idea, but had never published it.

“I was very, very happy to hear that, because I felt there may be a flaw in the idea, or that it had already been published,” Budker said.

While Budker’s lab continues its studies of how spin-polarized sodium atoms emit and absorb light, Budker’s co-authors Ronald Holzl√∂hner and Domenico Bonaccini Calia of the ESO in Garching, Germany, are building a 20-watt modulated laser for the Very Large Array in Chile that can be used to test the theory.

EARTH: Oil and water help US win World War II

The U.S. had two key strategic advantages over the Axis in World War II: oil and water. Although other factors played major roles in the U.S. and its allies winning the war, these two natural resources played a much larger role than recognized.

World War II was the first highly mechanized war. In the March feature “How Oil and Water Helped the U.S. Win World War II,” EARTH magazine explores how the abundance of domestic US oil and water in the South and Pacific Northwest drove not only tanks and planes, but also industrial production and technological innovation. That energy allowed the U.S. to supply its military and its allies with aircraft, armored vehicles and tanks and other heavy equipment – as well as the atomic bomb – that eventually overpowered Germany and Japan.

Read more of this historical analysis in the March issue, as well as other stories on topics such as how remote sensing helps aid agencies prepare for famine before it strikes and who should be paying for cleanup after wildfires and landslides strike, and follow along as a former NASA special investigator details a decade-plus of tracking moon rock thefts.

Study finds massive flux of gas, in addition to liquid oil, at BP well blowout in Gulf

A new University of Georgia study that is the first to examine comprehensively the magnitude of hydrocarbon gases released during the Deepwater Horizon Gulf of Mexico oil discharge has found that up to 500,000 tons of gaseous hydrocarbons were emitted into the deep ocean. The authors conclude that such a large gas discharge-which generated concentrations 75,000 times the norm-could result in small-scale zones of “extensive and persistent depletion of oxygen” as microbial processes degrade the gaseous hydrocarbons.

The study, led by UGA Professor of Marine Sciences Samantha Joye, appears in the early online edition of the journal Nature Geoscience. Her co-authors are Ian MacDonald of Florida State University, Ira Leifer of the University of California-Santa Barbara and Vernon Asper of the University of Southern Mississippi.

The Macondo Well blowout discharged not only liquid oil, but also hydrocarbon gases, such as methane and pentane, which were deposited in the water column. Gases are normally not quantified for oil spills, but the researchers note that in this instance, documenting the amount of hydrocarbon gases released by the blowout is critical to understanding the discharge’s true extent, the fate of the released hydrocarbons, and potential impacts on the deep oceanic systems. The researchers explained that the 1,480-meter depth of the blowout (nearly one mile) is highly significant because deep sea processes (high pressure, low temperature) entrapped the released gaseous hydrocarbons in a deep (1,000-1,300m) layer of the water column. In the supplementary online materials, the researchers provide high-definition photographic evidence of the oil and ice-like gas hydrate flakes in the plume waters.

Joye said the methane and other gases likely will remain deep in the water column and be consumed by microbes in a process known as oxidation, which en masse can lead to low-oxygen waters.

“We’re not talking about extensive hypoxic areas offshore in the Gulf of Mexico,” Joye explained. “But the microbial oxidation of the methane and other alkanes will remove oxygen from the system for quite a while because the time-scale for the replenishment of oxygen at that depth is many decades.”

Leifer added that some of the larger gaseous hydrocarbons documented, such as pentane, have significant health implications for humans and potentially for marine life.

The study concludes that separating the gas-induced oxygen depletion from that due to liquid hydrocarbons is difficult, absent further research, because all hydrocarbons contribute to oxygen depletion. Therefore, documenting the total mass of hydrocarbons discharged is critical for understanding the long-term implications for the Gulf’s microbial communities, food chain and overall system.

Joye’s team examined samples from 70 sites around the leaking wellhead during a research cruise aboard the R/V Walton Smith during late May and early June of 2010. They combined their data with estimates of the volume of oil released to arrive at a figure that allows scientists to quantify, for the first time, the gas discharge in terms of equivalent barrels of oil. They calculated a gas discharge that’s the equivalent of either 1.6 to 1.9 or 2.2 to 3.1 million barrels of oil, depending on the method used. Although the estimate reflects the uncertainty still surrounding the discharge, even the lowest magnitude represents a significant increase in the total hydrocarbon discharge.

“These calculations increase the accepted government estimates by about one third,” MacDonald said.

The ever-shifting small-scale currents in the Gulf likely have dissipated the plumes and the low oxygen zones associated with them, Joye said, making them difficult if not impossible to find at this point in time. Although gliders are a new platform being used, scientists typically search for subsurface features by dropping instruments from research vessels, a process that’s analogous to looking for a feature on the Earth’s surface by randomly dropping instruments from a height of 1,500 meters (about 5,000 feet) in the atmosphere.

“It’s like searching for a needle in the haystack,” Joye said. “We may never know what happened to all of that gas.”

Joye cautioned against assuming that microbes will rapidly consume the gases released from the well. Undoubtedly, the methane is a feast for them, Joye said, but she also noted that the microbes need nutrients, such as nitrogen, copper and iron. These nutrients are in scarce supply in the Gulf’s deep waters, Joye said, and once they are depleted the microbes will cease to grow-regardless of how much methane is available.

“This study highlights the value of knowledge gained from deep sea hydrate seepage research but also how poorly deep sea processes are understood, such as the role methane hydrates played in forming the deep methane plumes documented by this study,” Leifer said. “Deepwater Horizon underscored how ill-prepared the nation is to respond to future accidents. As a nation, we need to hear this deep sea Sputnik wake-up call.”