Europium points to new suspect in continental mystery

Europium points to new suspect in continental mystery Study: Rare earth element implicates garnet for continents’ missing iron HOUSTON — (May 16, 2018) — Clues from some unusual Arizona rocks pointed Rice University scientists toward a discovery — a subtle chemical signature in rocks the world over — that could answer a long-standing mystery: What […]

Rice, UH team preps for massive Antarctic glacier study

A team of scientists from Rice University, the University of Houston, the University of Alabama and Lamont-Doherty Earth Observatory will participate in an ambitious $25 million study aimed at determining how quickly Antarctica’s massive Thwaites Glacier could collapse.

Thwaites Glacier (Photo by James Yungel/NASA)

The Thwaites research program, a joint undertaking of the National Science Foundation and the United Kingdom’s Natural Environment Research Council, was announced today. U.S. and U.K. officials say the International Thwaites Glacier Collaboration (ITGC) is the largest joint project undertaken by their nations in Antarctica since the mapping of the Antarctic Peninsula more than 70 years ago.

Antarctica is covered by ice up to 2 miles thick, and gravity compresses the ice and causes it to move under its own weight. Thwaites drains ice from an area of West Antarctica almost as large as the state of Washington and is one of the largest Antarctic contributors to modern sea-level rise. From satellite measurements, scientists know that Thwaites’ rate of ice loss has doubled since the 1990s. A full collapse of the glacier could add several inches to global sea levels, and ITCG includes eight projects that hope to answer key questions about how much and how quickly Thwaites is changing.

Lauren Simkins (Photo by Jeff Fitlow/Rice University)

The Thwaites Offshore Research (THOR) project is led by principal investigator Julia Wellner, assistant professor of Earth and atmospheric sciences at UH, and includes Rice co-investigators Lauren Simkins and John Anderson, both of the Department of Earth, Environmental and Planetary Sciences. Simkins is a postdoctoral research associate and Anderson is the Maurice Ewing Chair in Oceanography.

“We have an important role in understanding changes in Thwaites Glacier,” Simkins said. “The offshore geological record contains signatures of the glacier’s retreat, and a better understanding of how the glacier has behaved in the past will allow us to better interpret what is observed today and what is predicted for the future.”

Because the land beneath Thwaites is below sea level, the glacier’s “grounding line” — the place where ice, land and water meet — is beneath a thick ice shelf that extends miles into the Amundsen Sea. Inflows of warming ocean currents beneath this and other Antarctic ice shelves have caused the grounding lines of Thwaites and other West Antarctic glaciers to retreat rapidly in recent years. THOR will use a suite of marine geological and geophysical data to examine how Thwaites retreated in the past and to determine key boundary conditions that help control its retreat.

This schematic shows an ice shelf extending miles beyond the “grounding line” where an Antarctic glacier meets both land and sea. Black lines t1, t2 and t3 show where the ice sheet was grounded to the seafloor during pauses in ice retreat. Rice University marine geologists will study the past and present grounding lines of Thwaites glacier as part of a massive U.S.-U.K. research effort. (Image courtesy of L. Prothro/Rice University)

 

THOR scientists will make high-resolution geophysical surveys of the seafloor from research ships and they’ll collect sediments from the sea floor as well as a drilling rig that can melt holes through up to 5,000 feet of the floating ice shelf.

Additional co-investigators on the THOR project include the University of Alabama’s Rebecca Minzoni, Lamont-Doherty Earth Observatory’s Frank Nitsche and U.K.-based investigators Robert Larter, Alastair Graham, Claus-Dieter Hillenbrand, James Smith and Kelly Hogan.

 

Sub-sea rift spills secrets to seismic probe

Rice-led study yields first clues about internal structure of Galicia margin

The first study to spring from a Rice University-led 2013 international expedition (click to read the 2013 press release Ocean explorers want to get to the bottom of Galiciato map the sea floor off the coast of Spain has revealed details about the evolution of the fault that separates the continental and oceanic plates.

A Rice University-led seismic survey of the Galicia margin off the coast of Spain has produced new details about the passive rift that separates the oceanic and continental plates, and in particular the S-reflector, a prominent detachment fault within the transition zone. (Credit: Nur Schuba/Rice University)

A paper in Earth and Planetary Science Letters by Rice graduate student Nur Schuba describes the internal structure of a large three-dimensional section of the Galicia, a non-volcanic passive margin between Europe and the Atlantic basin that shows no signs of past volcanic activity and where the crust is remarkably thin.

That thinness made it easier to capture 3-D data for about 525 square miles of the Galicia, the first transition zone in the world so analyzed.

Sophisticated seismic reflection tools towed behind a ship and on the ocean floor enabled the researchers to model the Galicia. Though the rift is buried under several hundreds of meters of powdered rock and invisible to optical instruments, seismic tools fire sound into the formation. The sounds that bounce back tell researchers what kind of rock lies underneath and how it’s configured.

Among the data are the first seismic images of what geologists call the S-reflector, a prominent detachment faultwithin the continent-ocean transition zone. They believe this fault accommodated slipping along the zone in a way that helped keep the crust thin.

“The S-reflector, which has been studied since the ’70s, is a very low-angle, normal fault, which means the slip happens due to extension,” Schuba said. “What’s interesting is that because it’s at a low angle, it shouldn’t be able to slip. But it did.

“One mechanism people have postulated is called the rolling hinge,” she said. “The assumption is that an initially steep fault slipped over millions of years. Because the continental crust there is so thin, the material underneath it is hot and domed up in the middle. The initially steep fault started rolling and became almost horizontal.

“So with the help of the doming of the material coming from below and also the continuous slip, that’s how it is likely to have happened,” Schuba said.

The Galicia group — from left, Rice graduate student Nur Schuba, alumnus Ara Alexanian and graduate research assistant Mari Tesi Sanjurjo — discuss the northwest portion of the 3-D seismic volume at Rice’s Visualization Lab. (Credit: Gary Linkevich/Rice University)

 

The large data set also provided clues about interactions between the detachment fault and the serpentinized mantle, the dome of softer rock that presses upward on the fault and lowers friction during slippage. The researchers believe that led the Galicia to evolve differently, weakening faults and allowing for longer durations of activity.

The research is relevant to geologists who study land as well as sea because detachment faults are common above the water, Schuba said. “One of my advisers, (adjunct faculty member) Gary Gray, is jazzed about this because he says you can see these faults in Death Valley and Northern California, but  you can’t ever see them fully because the faults keep going underground. You can’t see how deep they go or how the fault zones change or how they’re associated with other faults.

“But a 3-D dataset is like having an MRI,” she said. “We can bisect it any way we want. It makes me happy that this was the first paper to come out of the Galicia data and the fact that we can see things no one else could see before.”

Rice University alumnus Brian Jordan, co-author of a new study on the Galicia margin based on an extensive seismic survey led by Rice, points out crustal faults that connect to the margin’s S-reflector. (Credit: Gary Linkevich/Rice University)

Co-authors of the paper are Julia Morgan and Dale Sawyer, both Rice professors of Earth, environmental and planetary sciences; Rice alumnus Brian Jordan, now of BP America; Donna Shillington, the Lamont Associate Research Professor at Columbia University; Tim Reston, a professor of geology at the University of Birmingham, England; and Jonathan Bull, a professor of geology and geophysics at the University of Southampton, England.

The National Science Foundation, the U.K. Natural Environment Research Council and the GEOMAR Helmholtz Center for Ocean Research supported the research.

Rajdeep Dasgupta receives Duncan Award

Charles Duncan Award for Outstanding Academic Achievement

Rajdeep Dasgupta, professor of Earth, environmental and planetary sciences, received the Duncan Award,  which is presented by Rice deans upon the recommendation of senior faculty. It honors tenure-track or tenured faculty members who have less than 10 years of experience.

Francis Albarède wins Nemmers Prize

Francis Albarède, Emeritus Professor at the Ecole Normale Supérieure de Lyon and Wiess visiting professor at Rice in the Department of Earth, Environmental and Planetary Sciences, is the inaugural  Nemmers Prize winner in Earth Sciences by Northwestern University.

Albarède is recognized for his “fundamental applications of geochemistry to earth sciences” to include pioneering the use of unconventional stable isotopes as markers of natural processes and exploring the use of isotopic tracers in applications as diverse as archeology, history, biology and medicine. Image: Francis Albarède.

“I would never have expected such a huge and humbling distinction. I always thought of myself as jack-of-all-trades. It looks like my colleagues actually appreciated my contribution to the development of new instruments, such as Secondary Ion Mass Spectrometers in the ’80s and most notably Multiple Collector Inductively Coupled Plasma Mass Spectrometry in the ’90s, and some long-lasting analytical protocols.”

As a regular visitor to Rice since 2008, Albarède has applied his cutting-edge mathematical models, which bridge the physics and chemistry of natural processes, to better understand the geological processes operating from within the deep earth, to the crust and beyond.  His work with Rice faculty Cin-Ty Lee and Rajdeep Dasgupta has produced work that has shifted conventional knowledge of Earths early mantle chemical behavior, as well as confirmed the status of water and other volatiles in the Moon- all based on analyses produced at Rice.

“Cin-ty’s great intuition that the lack of fractionation between zinc and iron during magma formation and ascent proved to be extremely crucial in assessing the lack of water in the Moon. Against the popular idea that the interior of the Moon may have been wet, we showed that the tenet of Apollo years, a dry Moon, was still valid.”

The Nemmers Prize endowment was created in 1994 at Northwestern University by Erwin and Frederic Nemmers for economics, mathematics, musical composition, medical science, with Earth Sciences recently added in 2016. The award includes a $200,000 cash prize, and the opportunity to spend several weeks in the fall of 2018 at Northwestern to work with students and faculty on a number of scholarly activities.

“I strongly believe that geochemistry, and particularly isotope geochemistry, has the unique power of dealing with complex systems through the laws of physics. It provides a unified vision of seemingly very different processes and objects, from earth and planetary sciences to medicine and archeology using a rather coherent set of concepts and analytical tools. My ambition at Northwestern is to put together a new course demonstrating the unifying power of Geochemistry and its applications to a range of fields and a variety of objects. This course naturally can be used at Rice during my stay in 2019.”

Scientific Publications:

Lee, C. T. A., Luffi, P., Le Roux, V., Dasgupta, R., Albarède, F., and Leeman, W. P. (2010) The redox state of arc mantle using Zn/Fe systematics. Nature 468, 681-685.

Albarede, F., Albalat, E., and Lee, C.-T. A. (2015) An intrinsic volatility scale relevant to the Earth and Moon and the status of water in the Moon. Meteoritics and Planetary Sciences, 50 (4), 568-577.

Life beyond Earth: No plate tectonics, no problem

Life beyond Earth: No plate tectonics, no problem

Scientists prepare to look in unexpected places for ‘exoplanet biosignatures’

HOUSTON — (March 28, 2018) — Scientists looking for life on distant planets are making plans to search non-Earth-like planets based on discoveries within our solar system that are challenging long-standing ideas about habitable zones, plate tectonics and more.

In a new paper published online this week, Rice University geophysicist Adrian Lenardic and more than a dozen co-authors outline a path for both finding potential life signs around other stars and determining how likely it is that those signs are caused by alien life. The paper, “Exoplanet Biosignatures: Future Directions,” is available online and due to be published in Astrobiology.

Lenardic, who specializes in studying planetary dynamics, also authored an associated paper, “Volcanic-Tectonic Modes and Planetary Life Potential,” that will be published as a chapter in the upcoming “Handbook of Exoplanets” from Springer Publishing.

An artist’s impression of Ross 128 b, a temperate, rocky planet about 11 light-years from Earth that could have the necessary conditions for maintaining liquid surface water. (Photo courtesy of European Southern Observatory/M. Kornmesser)

“It used to be the thought that life could only exist in a narrow zone near a planet’s star because you need to be there to maintain liquid water,” said Lenardic, professor of Earth, environmental and planetary sciences. “Then, we send Voyager out to a moon of Jupiter and, lo and behold, it shows strong indications of a subsurface ocean. That’s because there is another energy source that did not get its proper due — tidal forces from the intense gravitational pull of Jupiter.

“This has opened up the range over our own solar system in which life can exist, and I think a lot of the gist of the forthcoming papers is that much of what we’re seeing is expanding the zone and expanding our thinking about the conditions needed for life. So, as we look for life around other stars, we should also expand our search strategies or we might miss something.”

Astronomers have cataloged more than 3,700 planets around distant stars. The 21-foot diameter mirroron the James Webb Space Telescope, which is set to launch in 2019, will be able to examine the atmospheres of rocky planets around distant stars, and astronomers are already designing future missions and instruments that will look for specific atmospheric signatures of life.

“A goal was to frame the problem,” Lenardic said of the new biosignature paper, which sprang from an exoplanet workshop that brought together a range of scientists. “The workshop team wanted to come up with a means of assigning a likelihood of life based on a given set of observations of a distant planet.”

Adrian Lenardic (Photo by Jeff Fitlow/Rice University)

He said the search for exolife is a team sport that involves biologists, astronomers, planetary scientists and others who collaborate through groups such as NASA’s Nexus for Exoplanet System Science (NExSS) project and the European Space Agency’s International Summer School in Astrobiology.

Lenardic’s contribution is to examine how the internal energy of planets, and associated volcanic-tectonic activity, influence their climate and ability to sustain life.

“When I teach planetary science, one question I actually give students is, ‘What is life? Give me a definition.’ And it’s not easy,” Lenardic said. He noted that students and working scientists have put forward a range of answers.

“But if we can agree on one thing, it’s that life needs energy,” he said. “We’ve thought about the sun as an energy source for a long time, and we’ve come to appreciate a planet’s internal energy, which comes from decay of radioactive elements within its rocky interior. Jupiter’s moons have taught us to also appreciate tidal forcing, and we’re starting to find exoplanets that have orbits that allow for significant tidal forcing.”

Lenardic said plate tectonics, much like the narrow habitable zone, is another long-held criterion for planetary habitability that is being challenged by recent findings.

Plate tectonics is the large-scale process that governs the movements of Earth’s crust.

“It is a particular surface manifestation of a planet’s internal energy, but it is not the only possible mode of volcanic and tectonic activity on a planet,” Lenardic said.

On Earth, plate tectonics plays a role in modulating climate, but the idea that plate tectonics is crucial for life is challenged by increasingly sophisticated models of planetary climates. For example, in a January study in the Journal of Geophysical Research, Lenardic and colleagues showed how water could be maintained on worlds without plate tectonics. The chapter in the upcoming “Handbook of Exoplanets” further explores this idea by considering planetary life potential under a range of tectonic modes that differ from Earth’s.

“I’m an optimist,” Lenardic said. “We’re at the first point in our history as humans where we might actually have some observations from other planets that we can use to test any of these ideas about life beyond our own. It can be easy to be Earth-centric and assume that life requires a planet like our own. But what we are seeing within our solar system is causing us to question this. One of the things I have learned from the history of exploring our own solar system is to be prepared for surprise. As we move beyond our solar system, in our search for life, that lesson is driving us to adapt our search strategies.”

Co-authors of the Astrobiology paper include lead author Sara Walker, Evgenya Shkolnik and Harrison Smith of Arizona State University; William Bains of the MIT; Leroy Cronin of the University of Glasgow; Shiladitya DasSarma of the University of Maryland School of Medicine; Sebastian Danielache of the Tokyo Institute of Technology and Sophia University in Tokyo; Shawn Domagal-Goldman of NASA’s Goddard Space Flight Center and the University of Washington’s Virtual Planetary Laboratory; Betul Kacar of Harvard, the University of Montana and the University of Arizona; Nancy Kiang of NASA’s Goddard Institute for Space Studies; Christopher Reinhard of the University of California, Riverside and Georgia Tech; William Moore of Hampton University and the National Institute of Aerospace in Hampton, Va.; and Edward Schwieterman of the Blue Marble Space Institute of Science in Seattle, the University of Washington’s Virtual Planetary Laboratory, the University of California, Riverside and the Universities Space Research Association in Columbia, Md.

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Jeff Falk
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Jade Boyd
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Life beyond Earth: No plate tectonics, no problem
Scientists prepare to look in unexpected places for ‘exoplanet biosignatures’
HOUSTON — (March 28, 2018) — Scientists looking for life on distant planets are making plans to search non-Earth-like planets based on discoveries within our solar system that are challenging long-standing ideas about habitable zones, plate tectonics and more.

In a new paper published online this week, Rice University geophysicist Adrian Lenardic and more than a dozen co-authors outline a path for both finding potential life signs around other stars and determining how likely it is that those signs are caused by alien life. The paper, “Exoplanet Biosignatures: Future Directions,” is available online and due to be published in Astrobiology.

An artist’s impression of Ross 128 b, a temperate, rocky planet about 11 light-years from EarthLong Description
An artist’s impression of Ross 128 b, a temperate, rocky planet about 11 light-years from Earth that could have the necessary conditions for maintaining liquid surface water. (Photo courtesy of European Southern Observatory/M. Kornmesser)

Lenardic, who specializes in studying planetary dynamics, also authored an associated paper, “Volcanic-Tectonic Modes and Planetary Life Potential,” that will be published as a chapter in the upcoming “Handbook of Exoplanets” from Springer Publishing.

“It used to be the thought that life could only exist in a narrow zone near a planet’s star because you need to be there to maintain liquid water,” said Lenardic, professor of Earth, environmental and planetary sciences. “Then, we send Voyager out to a moon of Jupiter and, lo and behold, it shows strong indications of a subsurface ocean. That’s because there is another energy source that did not get its proper due — tidal forces from the intense gravitational pull of Jupiter.

“This has opened up the range over our own solar system in which life can exist, and I think a lot of the gist of the forthcoming papers is that much of what we’re seeing is expanding the zone and expanding our thinking about the conditions needed for life. So, as we look for life around other stars, we should also expand our search strategies or we might miss something.”

Astronomers have cataloged more than 3,700 planets around distant stars. The 21-foot diameter mirror on the James Webb Space Telescope, which is set to launch in 2019, will be able to examine the atmospheres of rocky planets around distant stars, and astronomers are already designing future missions and instruments that will look for specific atmospheric signatures of life.

“A goal was to frame the problem,” Lenardic said of the new biosignature paper, which sprang from an exoplanet workshop that brought together a range of scientists. “The workshop team wanted to come up with a means of assigning a likelihood of life based on a given set of observations of a distant planet.”

Adrian LenardicLong Description
Adrian Lenardic (Photo by Jeff Fitlow/Rice University)

He said the search for exolife is a team sport that involves biologists, astronomers, planetary scientists and others who collaborate through groups such as NASA’s Nexus for Exoplanet System Science (NExSS) project and the European Space Agency’s International Summer School in Astrobiology.

Lenardic’s contribution is to examine how the internal energy of planets, and associated volcanic-tectonic activity, influence their climate and ability to sustain life.

“When I teach planetary science, one question I actually give students is, ‘What is life? Give me a definition.’ And it’s not easy,” Lenardic said. He noted that students and working scientists have put forward a range of answers.

“But if we can agree on one thing, it’s that life needs energy,” he said. “We’ve thought about the sun as an energy source for a long time, and we’ve come to appreciate a planet’s internal energy, which comes from decay of radioactive elements within its rocky interior. Jupiter’s moons have taught us to also appreciate tidal forcing, and we’re starting to find exoplanets that have orbits that allow for significant tidal forcing.”

Lenardic said plate tectonics, much like the narrow habitable zone, is another long-held criterion for planetary habitability that is being challenged by recent findings.

Plate tectonics is the large-scale process that governs the movements of Earth’s crust.

“It is a particular surface manifestation of a planet’s internal energy, but it is not the only possible mode of volcanic and tectonic activity on a planet,” Lenardic said.

On Earth, plate tectonics plays a role in modulating climate, but the idea that plate tectonics is crucial for life is challenged by increasingly sophisticated models of planetary climates. For example, in a January study in the Journal of Geophysical Research, Lenardic and colleagues showed how water could be maintained on worlds without plate tectonics. The chapter in the upcoming “Handbook of Exoplanets” further explores this idea by considering planetary life potential under a range of tectonic modes that differ from Earth’s.

“I’m an optimist,” Lenardic said. “We’re at the first point in our history as humans where we might actually have some observations from other planets that we can use to test any of these ideas about life beyond our own. It can be easy to be Earth-centric and assume that life requires a planet like our own. But what we are seeing within our solar system is causing us to question this. One of the things I have learned from the history of exploring our own solar system is to be prepared for surprise. As we move beyond our solar system, in our search for life, that lesson is driving us to adapt our search strategies.”

Co-authors of the Astrobiology paper include lead author Sara Walker, Evgenya Shkolnik and Harrison Smith of Arizona State University; William Bains of the MIT; Leroy Cronin of the University of Glasgow; Shiladitya DasSarma of the University of Maryland School of Medicine; Sebastian Danielache of the Tokyo Institute of Technology and Sophia University in Tokyo; Shawn Domagal-Goldman of NASA’s Goddard Space Flight Center and the University of Washington’s Virtual Planetary Laboratory; Betul Kacar of Harvard, the University of Montana and the University of Arizona; Nancy Kiang of NASA’s Goddard Institute for Space Studies; Christopher Reinhard of the University of California, Riverside and Georgia Tech; William Moore of Hampton University and the National Institute of Aerospace in Hampton, Va.; and Edward Schwieterman of the Blue Marble Space Institute of Science in Seattle, the University of Washington’s Virtual Planetary Laboratory, the University of California, Riverside and the Universities Space Research Association in Columbia, Md.

Ash from dinosaur-era volcanoes linked with shale oil, gas

Ash from dinosaur-era volcanoes linked with shale oil, gas

Shale oil, gas deposits accompany ash layers from thousands of volcanic eruptions

Nutrient-rich ash from an enormous flare-up of volcanic eruptions toward the end of the dinosaurs’ reign kicked off a chain of events that led to the formation of shale gas and oil fields from Texas to Montana.

Cin-Ty Lee (photo by J. Fitlow)

That’s the conclusion of a new study by Rice University geologists that appears this week in Nature Publishing’s online journal Scientific Reports.

“One of the things about these shale deposits is they occur in certain periods in Earth’s history, and one of those is the Cretaceous time, which is around the time of the dinosaurs,” said study lead author Cin-Ty Lee, professor and chair of Rice’s Department of Earth, Environmental and Planetary Sciences. “This was about 90 million to 100 million years ago, which is about the same time as a massive flare-up of arc volcanoes along what is today the Pacific rim of the Western United States.”

Advances in horizontal drilling and hydraulic fracturing over the past 20 years led to a U.S. energy boom in “unconventionals,” a category that includes the shale gas and “tight” oil found in shale fields like the Cretaceous Eagle Ford and Mowry and older ones like the Barnett and Bakken.

An enormous volcanic flare-up at the end of the dinosaurs’ reign kicked off a chain of events that led to the formation of the U.S. shale oil and gas fields from Texas to Montana. Rice University geologists said older shale gas fields, like the Marcellus in Pennsylvania and Ohio, may have formed from similar volcanic flare-ups hundreds of millions of years earlier. (Photo courtesy of Wikimedia Commons)

“These types of natural gas and oil are in tiny, tiny pores that range from a few millionths of a meter in diameter to a few thousandths of a meter,” Lee said. “The deposits are in narrow bands that can only be accessed with horizontal drilling, and the oil and gas are locked in these little pockets and are only available with techniques like hydraulic fracturing.”

Lee said that there have always been hints of a connection between ancient volcanic eruptions and unconventional shale hydrocarbons. During field trips out to West Texas, he and Rice students noticed hundreds of ash layers in exposed rock that dated to the Cretaceous period when much of western North America lay beneath a shallow ocean.

One of these trips happened in 2014 while Lee and Rice colleagues also were studying how a flare-up of Cretaceous-era arc volcanoesalong the U.S. Pacific rim had impacted Earth’s climate through enhanced volcanic production of carbon dioxide.

“We had seen ash layers before, but at this site we could see there were a lot of them, and that got us thinking,” Lee said. Lee, graduate student Hehe Jiang and Rice undergraduates Elli Ronay, Jackson Stiles and Matthew Neal decided to investigate the ash beds in collaboration with Daniel Minisini, a colleague at Shell Oil who had been doing extensive work on quantifying the exact number of ash beds.

The eruption of Alaska’s Pavlof Volcano as seen from the International Space Station May 18, 2013. The volcano’s ash cloud rose to 20,000 feet and extended over hundreds of miles of the northern Pacific Ocean. (Photo courtesy of NASA/ISS Crew Earth Observations experiment and Image Science and Analysis Laboratory, Johnson Space Center)

“It’s almost continuous,” Lee said. “There’s an ash layer at least every 10,000 years.”

Lee said the team determined that ash had come from hundreds of eruptions that spanned some 10 million years. The layers had been transported several hundred miles east of their volcanic source in California. The ash was deposited on the seafloor after being blown through plumes that rose miles into the atmosphere and drifted over the ocean. Lee and students analyzed samples of the ash beds in the geochemical facilities at Rice.

“Their chemical composition didn’t look anything like it would have when they left the volcano,” he said. “Most of the original phosphorus, iron and silica were missing.”

That brought to mind the oceanic “dead zones” that often form today near the mouths of rivers. Overfertilization of farms pumps large volumes of phosphorus down these rivers. When that hits the ocean, phytoplankton gobble up the nutrients and multiply so quickly they draw all the available oxygen from the water, leaving a “dead” region void of fish and other organisms.

Lee suspected the Cretaceous ash plumes might have caused a similar effect. To nail down whether the ash could have supplied enough nutrients, Lee and his team used trace elements like zirconium and titanium to match ash layers to their volcanic sources. By comparing rock samples from those sources with the depleted ash, the team was able to calculate how much phosphorus, iron and silica were missing.

Oxygen-depleted “dead zones” often form in the northern Gulf of Mexico due to nutrient-rich runoff from the Mississippi and Atchafalaya rivers, which are seen here as tan and greenish-brown plumes visible from the International Space Station in 2012. Nutrient-rich volcanic ash may have fed similar dead zones that produced shale oil and gas fields from Texas to Montana. (Photo courtesy of NASA/GSFC/Aqua MODIS)

“Normally, you don’t get any deposition of organic matter at the bottom of the water column because other living things will eat it before it sinks to the bottom,” Lee said. “We found the amount of phosphorus entering the ocean from this volcanic ash was about 10 times more than all the phosphorus entering all the world’s oceans today. That would have been enough to feed an oxygen-depleted dead zone where carbon could be exported all the way down to the sediment.”

The combination of the ashfall and oceanic dead zone concentrated enough carbon to form hydrocarbons.

“To generate a hydrocarbon deposit of economic value, you have to concentrate it,” Lee said. “In this case, it got concentrated because the ashes drove that biological productivity, and that’s where the organic carbon got funneled in.”

Lee said shale gas and tight oil deposits are not found in the ash layers but appear to be associated with them. Because the layers are so thin, they don’t show up on seismic scans that energy companies use to look for unconventionals. The discovery that hundreds of closely spaced ash layers could be a tell-tale sign of unconventionals might allow industry geologists to look for bulk properties of ash layers that would show up on scans, Lee said.

“There also are implications for the nature of marine environments,” he said. “Today, phosphorus is also a limiting nutrient for the oceans, but the input of the phosphorus and iron into the ocean from these volcanoes has major paleoenvironmental and ecological consequences.”

While the published study looked specifically at the Cretaceous and North America, Lee said arc volcano flare-ups at other times and locations on Earth may also be responsible for other hydrocarbon-rich shale deposits.

“I suspect they could,” he said. “The Vaca Muerta field in Argentina is the same age and was behind the same arc as what we were studying. The rock record gets more incomplete as you go further back in time, but in terms of other U.S. shales, the Marcellus in Pennsylvania was laid down more than 400 million years ago in the Ordovician, and it’s also associated with ashes.”

The research was funded by the National Science Foundation, the Guggenheim Foundation and the Geological Society of America.

After the fire, charcoal goes against the grain, with the flow

After the fire, charcoal goes against the grain, with the flow

Rice U. wildfire study: Soil charcoal became more concentrated over time

When a forest fire decimated more than 3,000 acres of Rice University-owned timberland in 2011, biogeochemist Carrie Masiello saw a silver lining in the blackened trees.

The Tri-County wildfire in September 2011 destroyed more than 18,000 acres of forest, including a Rice University-owned tract in Waller County, Texas. (Photo courtesy of C. Masiello/Rice University)

Masiello is an expert on how carbon behaves in soil, and she noticed a vexing problem in both the scientific literature and findings from her lab: Charcoal is abundant in soil, particularly in fertile regions like Europe’s breadbasket and America’s Corn Belt, but while it’s clear that most soil charcoal came from wildfires, it wasn’t at all clear why it stayed there so long or how it got into the soil after a fire.

In a newly published study in the Journal of Geophysical Research, Masiello and colleagues, including current and former graduate students Lacey Pyle and Kate Magee, analyzed soil samples collected after the fire and found that charcoal behaved very differently from other forms of soil carbon as the land rebounded from the fire.

“We looked at all forms of carbon in the soil, both immediately after the fire and over a two-year period, and we found that it became more evenly distributed over time, which is a sign that the land was returning to its baseline state,” Masiello said. “Charcoal behaves exactly the opposite. It’s distribution became more patchy over time, and we think that’s because it’s buoyant and gets moved by water and concentrated in low places on the landscape.”

Carrie Masiello (left) and Lacey Pyle. (Photo by Jeff Fitlow/Rice University)

Masiello said it was not a surprise that charcoal was buoyant. In fact, the research team had specifically chosen flat research sites because previous studies had shown that soil carbon tended to migrate downhill over time. The surprise was the extent to which charcoal from the fire had become concentrated, even in the absence of notable topographic relief.

“It was redistributed on the landscape pretty effectively,” said Pyle ’09, the lead author of the study. “Rather than staying where it was initially deposited, it had a tendency to move horizontally across the landscape. The total contents of charcoal in our study sites didn’t change that drastically over the time period, but where we were finding it changed quite a bit.”

Charcoal’s benefits as a soil amendment are fourfold: It reduces atmospheric carbon dioxide and pollution, improves crop productivity, allows agriculture in areas with marginal soils and makes soil more resilient to both drought and flooding.

Rice University graduate student Lacey Pyle uses a magnifying glass and tweezers to find charcoal in dozens of soil samples. (Photo by Jeff Fitlow/Rice University)

In 2008, Masiello and study co-author William Hockaday, then at Rice and presently at Baylor University, began seriously studying soil charcoal after winning a $10,000 prize in the city of Houston’s “Recycle Ike” contest in the wake of Hurricane Ike. The storm left 5.6 million cubic yards of fallen trees, broken branches and dead greenery in Houston, and Rice’s team took first place in the contest with their plan to convert the wood into biomass charcoal, or “biochar,” for use as a CO2-trapping soil amendment.

In subsequent studies, Masiello’s lab has explored biochar’s productionmicrobial impactshydrological characteristics and pollution-reducing effects.

“More carbon in soil is good, and as we think about ways to stabilize and increase soil carbon inventory, charcoal is an obvious option,” Masiello said.

To get the most benefit from biochar, Masiello said, scientists and land managers need to better understand the fate and transport of soil charcoal, and studying naturally occurring soil charcoal is a great way to gain that understanding.

When added to soil, charcoal can reduce nutrient pollution, lower atmospheric carbon dioxide, improve crop productivity and make soil more resilient to both drought and flooding. (Image courtesy of Ghasideh Pourhashem)

“We know that lots of carbon in soil is old,” she said, adding that the ages of soil charcoal measured with radiocarbon dating “suggest that it’s hard to decompose. But when we bring it into the lab, it turns out it’s not that hard to decompose.”

The findings from the wildfire study offer a new clue as to how naturally occurring charcoal can remain stable for long periods of time, Masiello said.

“It’s possible that the mobility of charcoal on the landscape and it’s tendency to become concentrated in low-lying spots could make it more likely the charcoal from wildfires becomes buried and incorporated deep in soils and that these deposits act as a kind of charcoal reservoir that releases charcoal into the soil over long time spans.”

The research was funded by Rice University and Chevron. Additional co-authors include postdoctoral research associate Morgan Gallagher.

Heavy nitrogen molecules reveal planetary-scale tug-of-war

Rice, UCLA, Michigan State, UNM find unusual enrichment in 15N15N molecules

Nature whispers its stories in a faint molecular language, and Rice University scientist Laurence Yeung and colleagues can finally tell one of those stories this week, thanks to a one-of-a-kind instrument that allowed them to hear what the atmosphere is saying with rare nitrogen molecules.

Yeung and colleagues at Rice, UCLA, Michigan State University and the University of New Mexico counted rare molecules in the atmosphere that contain only heavy isotopes of nitrogen and discovered a planetary-scale tug-of-war between life, the deep Earth and the upper atmosphere that is expressed in atmospheric nitrogen.

The research was published online this week in the journal Science Advances.

“We didn’t believe it at first,” said Yeung, the lead author of the study and an assistant professor of Earth, environmental and planetary sciences at Rice. “We spent about a year just convincing ourselves that the measurements were accurate.”

The story revolves around nitrogen, a key element of life that makes up more than three-quarters of Earth’s atmosphere. Compared with other key elements of life like oxygen, hydrogen and carbon, nitrogen is very stable. Two atoms of it form N2 molecules that are estimated to hang around in the atmosphere for about 10 million years before being broken apart and reformed. And the vast majority of nitrogen has an atomic mass of 14. Only about 0.4 percent are nitrogen-15, an isotope that contains one extra neutron. Because nitrogen-15 is already rare, N2 molecules that contain two nitrogen-15s — which chemists refer to as 15N15N — are the rarest of all N2 molecules.

The new study shows that 15N15N is 20 times more enriched in Earth’s atmosphere than can be accounted for by processes happening near Earth’s surface.

Rice Assistant Professor Laurence Yeung. Photo by Jeff Fitlow

 

“We think the 15N15N enrichment fundamentally comes from chemistry in the upper atmosphere, at altitudes close to the orbit of the International Space Station,” Yeung said. “The tug-of-war comes from life pulling in the other direction, and we can see chemical evidence of that.”

Co-author Edward Young, professor of Earth, planetary and space sciences at UCLA, said, “The enrichment of 15N15N in Earth’s atmosphere reflects a balance between the nitrogen chemistry that occurs in the atmosphere, at the surface due to life and within the planet itself. It’s a signature unique to Earth, but it also gives us a clue about what signatures of other planets might look like, especially if they are capable of supporting life as we know it.”

The chemical processes that produce molecules like N2 can change the odds that “isotope clumps” like 15N15N will be formed. In previous work, Yeung, Young and colleagues used isotope clumps in oxygen to identify tell-tale signatures of photosynthesis in plants and ozone chemistry in the atmosphere. The nitrogen study began four years ago when Yeung, then a postdoctoral researcher at UCLA, learned about a first-of-its-kind mass spectrometer that was being installed in Young’s lab.

The amount of nitrogen molecules in Earth’s atmosphere that contain only heavy isotopes result from a balance between nitrogen chemistry that occurs in the atmosphere, at the surface due to life and within the planet itself. (Photo courtesy of ISS Expedition 7 Crew, EOL, NASA)

“At that time, no one had a way to reliably quantify 15N15N,” said Yeung, who joined Rice’s faculty in 2015. “It has an atomic mass of 30, the same as nitric oxide. The signal from nitric oxide usually overwhelms the signal from 15N15N in mass spectrometers.”

The difference in mass between nitric oxide and 15N15N is about two one-thousandths the mass of a neutron. When Yeung learned that the new machine in Young’s lab could discern this slight difference, he applied for grant funding from the National Science Foundation (NSF) to explore exactly how much 15N15N was in Earth’s atmosphere.

“Biological processes are hundreds to a thousand times faster at cycling nitrogen through the atmosphere than are geologic processes,” Yeung said. “If it’s all business as usual, one would expect that the atmosphere would reflect these biological cycles.”

To find out if this was the case, co-authors Joshua Haslun and Nathaniel Ostrom at Michigan State University conducted experiments on N2-consuming and N2-producing bacteria to determine their 15N15N signatures.

These experiments suggested that one should see a bit more 15N15N in air than random pairings of nitrogen-14 and nitrogen-15 would produce — an enrichment of about 1 part per 1,000, Yeung said.

Researchers from Rice University and UCLA simulated high-energy chemistry in the upper atmosphere to reproduce enriched levels of 15N15N, molecules that contain only heavy isotopes of nitrogen. (Photo by Laurence Yeung/Rice University)

“There was a bit of enrichment in the biological experiments, but not nearly enough to account for what we’d found in the atmosphere,” Yeung said. “In fact, it meant that the process causing the atmospheric 15N15N enrichment has to fight against this biological signature. They are locked in a tug-of-war.”

The team eventually found that zapping mixtures of air with electricity, which simulates the chemistry of the upper atmosphere, could produce enriched levels of 15N15N like they measured in air samples. Mixtures of pure nitrogen gas produced very little enrichment, but mixtures approximating the mix of gases in Earth’s atmosphere could produce a signal even higher than what was observed in air.

“So far we’ve tested natural air samples from ground level and from altitudes of 32 kilometers, as well as dissolved air from shallow ocean water samples,” he said. “We’ve found the same enrichment in all of them. We can see the tug-of-war everywhere.”

Co-authors include Huanting Hu of Rice, Shuning Li, formerly of Rice and UCLA and now with Peking University in Beijing, Issaku Kohl and Edwin Schauble of UCLA and Tobias Fischer of the University of New Mexico.

The research was supported by the NSF, the Deep Carbon Observatory and the Department of Energy’s Great Lakes Bioenergy Research Center.