Evidence of Ancient Lake in California's Eel River Emerges

Caltech-led team documents ecological changes that may explain the two different populations of once-related steelhead trout found today in the river

PASADENA, Calif.—A catastrophic landslide 22,500 years ago dammed the upper reaches of northern California's Eel River, forming a 30-mile-long lake—which has since disappeared—and leaving a living legacy found today in the genes of the region's steelhead trout, according to scientists at the California Institute of Technology (Caltech) and the University of Oregon.

Using remote-sensing technology known as airborne Light Detection and Ranging (LiDAR) and hand-held global positioning system (GPS) units, a three-member research team found evidence for a late Pleistocene, landslide-dammed lake–located about 60 miles southeast of Eureka, California—along the Eel River.

The river today is 200 miles long and carved into the ground from high in the California Coast Ranges to its mouth on the Pacific Ocean in Humboldt County.

The evidence for the ancient landslide—which, scientists say, blocked the river with a 400-foot wall of loose rock and debris—is detailed this week in a paper appearing online ahead of print in the Proceedings of the National Academy of Sciences. The study provides a rare glimpse into the geological and ecological history of this rapidly evolving mountainous region.

According to Benjamin H. Mackey, lead author of the study and a postdoctoral researcher at Caltech, the findings help to explain emerging evidence from other studies that show a dramatic decrease in the amount of sediment deposited from the river in the ocean just off shore at about the same time period.

Mackey and his colleagues were drawn to the Eel River, which is among the most-studied erosion systems in the world, to study large, slow-moving landslides. "While analyzing the elevation of terraces along the river, we discovered they clustered at a common elevation rather than decreasing in elevation downstream, paralleling the river profile, as would be expected for river terraces," he says. "This was the first sign of something unusual, and it clued us in to the possibility of an ancient lake."

By combining the findings from their field investigations with analysis of the topographic data provided by the LiDAR mapping, the team was able to identify a large landslide scar on the flank of a nearby peak, and detect subtle shorelines upstream of the landslide. The researchers suggest that a landslide in this area would have been capable of damming the river and creating a lake. An outcrop of finely laminated lake sediments discovered in a tributary stream provided compelling physical evidence for the lake’s existence.

An image constructed from high-resolution topography acquired via LiDAR remote sensing shows an oblique view of the reconstructed lake surface (transparent blue). The modern bed of the Eel River is the broad flat area across the center-left of the image. The inset shows sediment found upstream of the dam and indicate deposition in still water, typical of a lake environment. Charcoal within these sediments was radiocarbon dated to estimate the time of lake emplacement at 22,500 years ago.
Credit: California Institute of Technology

"Perhaps of most interest, the presence of this landslide dam also provides an explanation for the results of previous research on the genetics of steelhead trout in the Eel River," says Mackey, referring to a 1999 study by the U.S. Forest Service. In that study, researchers found a striking relationship between two types of ocean-going steelhead in the river—a genetic similarity not seen among summer-run and winter-run steelhead in other nearby rivers.

An interbreeding of the two fish, in a process known as genetic introgression, may have occurred among the fish brought together while the river was dammed, Mackey says. "The dam likely would have been impassable to the fish migrating upstream, meaning both ecotypes would have been forced to spawn and inadvertently interbreed downstream of the dam," he explains. "This period of gene flow between the two types of steelhead can explain the genetic similarity observed today."

Once the dam burst, the fish would have reoccupied their preferred spawning grounds and resumed different genetic trajectories, he adds.

"The damming of the river was a dramatic, punctuated affair that greatly altered the landscape," says coauthor Joshua J. Roering, an associate professor of geological sciences at the University of Oregon. "Although current physical evidence for the landslide dam and paleolake is subtle, its effects are recorded in the Pacific Ocean and persist in the genetic makeup of today's Eel River steelhead. It’s rare for scientists to be able to connect the dots between such diverse and widely felt phenomena."

The lake formed by the landslide, researchers theorize, covered about 12 square miles. After the dam was breached, the flow of water would have generated one of North America's largest landslide-dam outburst floods. Landslide activity and erosion have erased much of the evidence for the now-gone lake. Without the acquisition of LiDAR mapping, the lake's existence may have never been discovered, researchers say.

“This was a remarkable discovery, since large lakes in steep, rapidly uplifting mountain terrain are rare," says Michael P. Lamb, assistant professor of geology at Caltech and coauthor of the study. "Moreover, high erosion rates tend to erase evidence that past lakes ever existed. Ben was able to piece together subtle pieces of geologic evidence from landslides to shorelines to show that this lake existed, and that its presence is still felt thousands of years after its demise in local fish populations and in the marine sedimentary record."

The National Center for Airborne Laser Mapping provided the LiDAR data used in the project. Funding for the study, "Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish," was provided by the National Science Foundation and the Keck Institute for Space Studies at Caltech. 

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Wet and Mild: Caltech Researchers Take the Temperature of Mars's Past

PASADENA, Calif.—Researchers at the California Institute of Technology (Caltech) have directly determined the surface temperature of early Mars for the first time, providing evidence that's consistent with a warmer and wetter Martian past.

By analyzing carbonate minerals in a four-billion-year-old meteorite that originated near the surface of Mars, the scientists determined that the minerals formed at about 18 degrees Celsius (64 degrees Fahrenheit). "The thing that's really cool is that 18 degrees is not particularly cold nor particularly hot," says Woody Fischer, assistant professor of geobiology and coauthor of the paper, published online in the Proceedings of the National Academy of Sciences (PNAS) on October 3. "It's kind of a remarkable result."

Knowing the temperature of Mars is crucial to understanding the planet's history—its past climate and whether it once had liquid water. The Mars rovers and orbiting spacecraft have found ancient deltas, rivers, lakebeds, and mineral deposits, suggesting that water did indeed flow. Because Mars now has an average temperature of -63 degrees Celsius, the existence of liquid water in the past means that the climate was much warmer then. But what's been lacking is data that directly points to such a history. "There are all these ideas that have been developed about a warmer, wetter early Mars," Fischer says. "But there's precious little data that actually bears on it." That is, until now.

The finding is just one data point—but it's the first and only one to date. "It's proof that early in the history of Mars, at least one place on the planet was capable of keeping an Earthlike climate for at least a few hours to a few days," says John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry, and a coauthor of the paper. The first author is Itay Halevy, a former postdoctoral scholar who's now at the Weizmann Institute of Science in Israel.

To make their measurement, the researchers analyzed one of the oldest known rocks in the world: ALH84001, a Martian meteorite discovered in 1984 in the Allan Hills of Antarctica. The meteorite likely started out tens of meters below the Martian surface and was blown off when another meteorite struck the area, blasting the piece of Mars toward Earth. The potato-shaped rock made headlines in 1996 when scientists discovered tiny globules in it that looked like fossilized bacteria. But the claim that it was extraterrestrial life didn't hold up upon closer scrutiny. The origin of the globules, which contain carbonate minerals, remained a mystery.

"It's been devilishly difficult to work out the process that generated the carbonate minerals in the first place," Eiler says. But there have been countless hypotheses, he adds, and they all depend on the temperature in which the carbonates formed. Some scientists say the minerals formed when carbonate-rich magma cooled and crystallized. Others have suggested that the carbonates grew from chemical reactions in hydrothermal processes. Another idea is that the carbonates precipitated out of saline solutions. The temperatures required for all these processes range from above 700 degrees Celsius in the first case to below freezing in the last. "All of these ideas have merit," Eiler says.

Finding the temperature through independent means would therefore help narrow down just how the carbonate might have been formed. The researchers turned to clumped-isotope thermometry, a technique developed by Eiler and his colleagues that has been used for a variety of applications, including measuring the body temperatures of dinosaurs and determining Earth's climate history.

In this case, the team measured concentrations of the rare isotopes oxygen-18 and carbon-13 contained in the carbonate samples. Carbonate is made out of carbon and oxygen, and as it forms, the two rare isotopes may bond to each other—clumping together, as Eiler calls it. The lower the temperature, the more the isotopes tend to clump. As a result, determining the amount of clumping allows for a direct measurement of temperature.

The temperature the researchers measured—18 ± 4 degrees Celsius—rules out many carbonate-formation hypotheses. "A lot of ideas that were out there are gone," Eiler says. For one, the mild temperature means that the carbonate must have formed in liquid water. "You can't grow carbonate minerals at 18 degrees other than from an aqueous solution," he explains. The new data also suggests a scenario in which the minerals formed from water that filled the tiny cracks and pores inside rock just below the surface. As the water evaporated, the rock outgassed carbon dioxide, and the solutes in the water became more concentrated. The minerals then combined with dissolved carbonate ions to produce carbonate minerals, which were left behind as the water continued to evaporate.

Could this wet and warm environment have been a habitat for life? Most likely not, the researchers say. These conditions wouldn't have existed long enough for life to grow or evolve—it would have taken only hours to days for the water to dry up. Still, these results are proof that an Earthlike environment once existed in at least one particular spot on Mars for a short time, the researchers say. What that implies for the global geology of Mars—whether this rock is representative of Martian history or is just an isolated artifact—is an open question.

The research described in the PNAS paper, "Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment," was supported by a Texaco Postdoctoral Fellowship, NASA, and the National Science Foundation.

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Caltech Named World's Top University in New Times Higher Education Global Ranking

PASADENA, Calif.—The California Institute of Technology (Caltech) has been rated the world's number one university in the 2011–2012 Times Higher Education global ranking of the top 200 universities, displacing Harvard University from the top spot for the first time in the survey's eight-year history.

Caltech was number two in the 2010–2011 ranking; Harvard and Stanford University share the second spot in the 2011–2012 survey, while the University of Oxford and Princeton University round out the top five.

"It's gratifying to be recognized for the work we do here and the impact it has—both on our students and on the global community," says Caltech president Jean-Lou Chameau. "Today's announcement reinforces Caltech's legacy of innovation, and our unwavering dedication to giving our extraordinary people the environment and resources with which to pursue their best ideas. It's also truly gratifying to see three California schools—including my alma mater, Stanford—in the top ten."

Thirteen performance indicators representing research (worth 30% of a school's overall ranking score), teaching (30%), citations (30%), international outlook (which includes the total numbers of international students and faculty and the ratio of scholarly papers with international collaborators; 7.5%), and industry income (a measure of innovation; 2.5%) are included in the data. Among the measures included are a reputation survey of 17,500 academics; institutional, industry, and faculty research income; and an analysis of 50 million scholarly papers to determine the average number of citations per scholarly paper, a measure of research impact.

"We know that innovation is the driver of the global economy, and is especially important during times of economic volatility," says Kent Kresa, chairman of the Caltech Board of Trustees. "I am pleased that Caltech is being recognized for its leadership and impact; this just confirms what many of us have known for a long time about this extraordinary place."

"Caltech has been one of California's best-kept secrets for a long time," says Caltech trustee Narendra Gupta. "But I think the secret is out!"

Times Higher Education, which compiled the listing using data supplied by Thomson Reuters, reports that this year's methodology was refined to ensure that universities with particular strength in the arts, humanities, and social sciences are placed on a more equal footing with those with a specialty in science subjects. Caltech—described in a Times Higher Education press release as "much younger, smaller, and specialised" than Harvard—was nevertheless ranked the highest based on their metrics.

According to Phil Baty, editor of the Times Higher Education World University Rankings, "the differences at the top of the university rankings are miniscule, but Caltech just pips Harvard with marginally better scores for 'research—volume, income, and reputation,' research influence, and the income it attracts from industry. With differentials so slight, a simple factor plays a decisive role in determining rank order: money."

"Harvard reported funding increases similar in proportion to other institutions, whereas Caltech reported a steep rise (16%) in research funding and an increase in total institutional income," Baty says.

Data for the Times Higher Education's World University Rankings was provided by Thomson Reuters from its Global Institutional Profiles Project (http://science.thomsonreuters.com/globalprofilesproject/), an ongoing, multistage process to collect and validate factual data about academic institutional performance across a variety of aspects and multiple disciplines.

For a full list of the world's top 200 schools and all of the performance indicators, go to http://www.timeshighereducation.co.uk/world-university-rankings/.

# # # 

The California Institute of Technology (Caltech) is a small, private university in Pasadena that conducts instruction and research in science and engineering, with a student body of about 900 undergraduates and 1,200 graduate students. Recognized for its outstanding faculty, including several Nobel laureates, and such renowned off-campus facilities as the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the Palomar Observatory, Caltech is one of the world's preeminent research centers.

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Caltech Geobiologist Receives Presidential Early Career Award

PASADENA, Calif.—Victoria Orphan, professor of geobiology at the California Institute of Technology (Caltech), is one of 94 winners of a Presidential Early Career Award for Scientists and Engineers (PECASE), the highest honor bestowed by the U.S. government on scientists and engineers beginning their independent careers.

Orphan, one of 13 Department of Energy (DOE) researchers in the 2011 class, was commended for "developing new techniques to study interactions between microbes, relevant for understanding the role of methane in the biosphere, which is of urgent importance for addressing the global carbon cycle and climate change; and for emerging leadership in the microbiology research community," according to the DOE.

"It is inspiring to see the innovative work being done by these scientists and engineers as they ramp up their careers—careers that I know will be not only personally rewarding but also invaluable to the nation," said President Obama in a statement issued September 26, announcing the awards.

The awards, established by President Clinton in 1996, are coordinated by the Office of Science and Technology Policy within the Executive Office of the President. Awardees are selected for their pursuit of innovative research at the frontiers of science and technology and their commitment to community service as demonstrated through scientific leadership, public education, or community outreach.

"I am deeply honored to have been selected as a PECASE awardee and grateful for the support by DOE's Biological and Environmental Research program," says Orphan, whose work spans the fields of environmental microbiology, ecology, and biogeochemistry, focusing primarily on the microbial cycling of methane. Her research—much of which is done using both manned and robotic submersibles to study areas of methane release in the deep sea—attempts to elucidate the metabolic links between microorganisms and their resulting impact on the cycling of carbon and nutrients in the environment.

Orphan received her PhD in biology in 2001 from UC Santa Barbara and was a National Research Council Postdoctoral Fellow at the NASA Ames Research Center before joining the Division of Geological and Planetary Science in 2004.

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Out-of-this-world researchers join GPS faculty

Growing up on an army base on Kwajalein, a part of the Marshall Islands, Heather Knutson was dazzled at an early age by the starry night sky from her clear vantage point in the South Pacific. Her parents, however, convinced her that a career in astronomy was not very practical, so instead she explored physics and engineering as a teenager. Now, just seven years after receiving a bachelor's in physics from Johns Hopkins, Knutson is one of the most recent faculty recruits to Caltech's Division of Geological and Planetary Sciences. And as an assistant professor of planetary science, she's proving that space study can be practical after all.

"I spent two years during my undergrad studies working at the Space Telescope Science Institute, which, incidentally, is next to the physics building at Johns Hopkins," says Knutson. "It was there that I realized that it might actually be possible to pursue a career in astronomy. Obviously I'm not in an astronomy department now, but since the objects I study are planets, I guess you could call me a planetary astronomer. I never planned to end up where I did, but I'm very glad that I have."  

After earning her BS, Knutson went on to receive both a master's and doctoral degree in astronomy from Harvard. Prior to joining Caltech, she was a Miller Fellow at UC Berkeley for two years. Her research is focused on characterizing the properties of the planets that orbit stars other than our sun, including the temperatures, compositions, and atmospheric circulation patterns of these extra solar planets (or exoplanets)—all of which she tries to identify using observations of eclipsing systems.

"We have this giant, diverse, weird sample of planets—none of which match anything that we've seen before in our own solar system," says Knutson. "If we can learn something about the properties of these planets, then we can potentially learn a lot about planets in general—how they form, how they evolve, what's typical, what isn't, et cetera."

Exoplanets are too far away to be seen from Earth, and therefore are studied through measurements taken when the orbiting planet passes in front of or behind its parent star, which is visible. For example, as the planet passes in front of the star, it blocks part of the star's light in an event known as a transit. The amount of light the planet blocks indicates the radius of the planet relative to that of the star, she explains.

"I use telescopes to observe these objects and Caltech has wonderful resources," says Knutson, who also studies weather on exoplanets. "The great thing about being here is that there are not only top-notch telescopes that you can get time on, but there are actually telescopes that you can drive to."

Knutson isn't the only new faculty member in GPS who spends her time looking into space. Bethany Ehlmann, assistant professor of planetary sciences who joined Caltech in August following a Marie Curie Fellowship at the Institut d'Astrophysique Spatiale (Institute of Space & Astrophysics) in France, has her sights set on a planet that robots, and potentially humans, can actually visit: Mars.

"My primary skills are in remote sensing and analysis of satellite images, using data both from other planets and acquired around Earth. It's a skill set I like to deploy for a wide variety of problems," she says. "Most recently, I've been working on understanding environmental conditions early in Mars's history, via detection of minerals like clays, carbonates, and sulfates."

Ehlmann's interest in Mars and remote sensing began when she was an undergraduate at Washington University, where planetary scientist Ray Arvidson, who also runs an undergrad program in environmental studies, served as her mentor. During her time as a student and after graduating, she spent nine months at NASA's Jet Propulsion Laboratory, working science operations for the Mars Exploration Rovers.

"I was working on day-to-day mission operations immediately after they landed. After that experience, I was more or less hooked on planetary science," says Ehlmann, who went on to spend two years at the University of Oxford as a Rhodes Scholar and then earn a PhD as a National Science Foundation fellow in the Geological Sciences department at Brown University.

Back on the West Coast, her research focus at Caltech will be three-fold, Ehlmann says. She plans to continue looking into the early history of Mars and its changing environmental processes though time, and will also work to improve remote sensing techniques, particularly for remote compositional analysis, or remotely detecting the minerals that make up planetary surfaces. In addition, she hopes to add to the understanding of physical and chemical weathering processes on Earth and other planets.

"I was one of those students who, on college applications, would check ecology, astronomy, geology, environmental policy, international relations. What I like about space exploration is that it actually involves a little piece of each of those," she says. "And certainly the science I do on the Earth side has policy implications for understanding environmental change."

Ehlmann is also excited to be back at JPL, where her journey in space exploration began. She will have a joint appointment at the lab, which is managed by Caltech for NASA.

"Caltech is a great institution to be a part of, with excellent students and fellow faculty, as well as wonderful resources like JPL," she says. "I'll spend some of my time working on current missions, and perhaps with some of the scientists and engineers to develop instruments to propose for future opportunities in solar system exploration."

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A Wave of New Earth-Science Faculty Joins GPS Division

Recent hires focus on ocean-related research

For Andrew Thompson, assistant professor of environmental science and engineering who joined the Caltech Division of Geological and Planetary Sciences in August, growing up in Rhode Island gave him a natural affinity for the ocean. However it wasn't until the summer before his senior year in college that he realized that he could put his fascination for the sea to good use.

"As a kid, I enjoyed math and physics, but thought oceanography was just about studying fish," says Thompson. While attending a summer program at Woods Hole Oceanographic Institution before his last undergrad year as an engineering student, however, he discovered that wasn't the case. "I learned there that I could do ocean science from a fluid-dynamics standpoint," he says, "and I fell in love with it."

After earning a BA in engineering sciences from Dartmouth, Thompson went on to receive an MPhil in fluid flow from the University of Cambridge and a PhD in physical oceanography from the Scripps Institution of Oceanography at UC San Diego. Thompson then returned to the UK for postdoctoral research stints at the University of East Anglia and the University of Cambridge. Before coming to Caltech, he spent a year as an advanced research fellow at the Natural Environment Research Council's British Antarctic Survey.

Throughout his studies, he never forgot the project at Woods Hole that first inspired him. 

"We looked at the transport of harmful algal blooms that had formed in the Gulf of Maine, which can be a serious economic and public-health problem," remembers Thompson. "The research I do now is actually very similar to that, but working in different regions of the ocean, primarily in the Southern Ocean around Antarctica."

Although Caltech doesn't have a long history of oceanography research, the Institute is striving to look very closely at climate from a holistic viewpoint at the Ronald and Maxine Linde Center for Global Environmental Science, where Thompson will have his lab among other scientists from a broad selection of disciplines. His physical ocean research focuses on eddies in the ocean, which are similar to atmospheric storms except that they happen in the water. They are important for mixing the ocean and transporting heat, chemicals, and biological elements. 

"I'm excited to be part of the Linde + Robinson Laboratory, which will bring people together from a wide range of backgrounds," says Thompson. "I think there will be a really good opportunity to broaden the work I've done and look at some of the implications on a larger scale."

While Thompson studies the way sea storms move things around, Victor Tsai, assistant professor of geophysics, is busy measuring the seismic noise produced by the movements of the ocean—partly from the crashing of waves onto the shore.

"My major focus right now is looking at sources of seismic energy other than earthquakes, and one of the biggest sources is ocean waves," he says. The waves create a noticeable seismic signal that can be recorded at seismic stations on the coast and inland. Analyzing this seismic noise helps researchers understand what makes up Earth's crust by tracking how fast the waves travel and how quickly they lose energy as they move through the earth.

Tsai also studies the effect that sea ice has on the seismic noise of ocean waves, which can give clues into how fast the ice is melting. His innovative research incorporates input from numerous fields, including seismology, geomechanics, glaciology, oceanography, and mathematical geophysics.

For Tsai, the new faculty appointment at Caltech is a bit of a homecoming. He earned a BS in geophysics here in 2004. Although he began his undergrad studies as a physics major, his first research project quickly showed Tsai that physics wasn't for him. He switched to geophysics, and his undergrad advisor was renowned seismologist Hiroo Kanamori, who influenced him to take a different look at the field.

"He had a research project for me that looked at atmospheric wave couplings with the solid earth," says Tsai. "That was my first geophysics project, and it was a bit unusual, since most people in the field aren’t looking at anything related to the atmosphere. I really enjoyed it, so I started to look for nontraditional geophysical problems to work on."

After Caltech, Tsai went on to earn an MA and PhD in Earth and planetary sciences at Harvard University. His postdoctoral work included a two-year Mendenhall Postdoctoral Fellowship at the Geological Hazards Science Center of the USGS in Colorado. In addition to seismic noise, Tsai, a member of Caltech's Seismo Lab, studies a wide variety of solid-earth topics, from the role of fluids in fault zones and understanding glacial earthquakes, to mechanical modeling of seismic events and improving current imaging techniques. He thinks the synergistic nature of the faculty here will help support and nourish his unique research interests.

"I really enjoy the way that people interact at Caltech," says Tsai. "Everyone shares ideas and are open to collaboration." 

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Astronomers Find Ice and Possibly Methane on Snow White, a Distant Dwarf Planet

PASADENA, Calif.—Astronomers at the California Institute of Technology (Caltech) have discovered that the dwarf planet 2007 OR10—nicknamed Snow White—is an icy world, with about half its surface covered in water ice that once flowed from ancient, slush-spewing volcanoes. The new findings also suggest that the red-tinged dwarf planet may be covered in a thin layer of methane, the remnants of an atmosphere that's slowly being lost into space.

"You get to see this nice picture of what once was an active little world with water volcanoes and an atmosphere, and it's now just frozen, dead, with an atmosphere that's slowly slipping away," says Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, who is the lead author on a paper to be published in the Astrophysical Journal Letters describing the findings. The paper is now in press.

Snow White—which was discovered in 2007 as part of the PhD thesis of Brown's former graduate student Meg Schwamb—orbits the sun at the edge of the solar system and is about half the size of Pluto, making it the fifth largest dwarf planet. At the time, Brown had guessed incorrectly that it was an icy body that had broken off from another dwarf planet named Haumea; he nicknamed it Snow White for its presumed white color.

Soon, however, follow-up observations revealed that Snow White is actually one of the reddest objects in the solar system. A few other dwarf planets at the edge of the solar system are also red. These distant dwarf planets are themselves part of a larger group of icy bodies called Kuiper Belt Objects (KBOs). As far as the researchers could tell, Snow White, though relatively large, was unremarkable—just one out of more than 400 potential dwarf planets that are among hundreds of thousands of KBOs.

"With all of the dwarf planets that are this big, there's something interesting about them—they always tell us something," Brown says. "This one frustrated us for years because we didn't know what it was telling us." At that time, the Near Infrared Camera (NIRC) at the Keck Observatory—which Caltech professor of physics Tom Soifer and chief instrument scientist Keith Matthews helped design in the 1990s—was the best instrument astronomers had to study KBOs, according to Brown. But NIRC had just been retired, so no one could observe 2007 OR10 in detail. "It kind of languished," he says.

Meanwhile, Adam Burgasser, a former graduate student of Brown's and now a professor at UC San Diego, was helping to design a new instrument called the Folded-port Infrared Echellette (FIRE). Last fall, Brown, Burgasser, and postdoctoral scholar Wesley Fraser used this instrument with the 6.5-meter Magellan Baade Telescope in Chile to take a closer look at 2007 OR10.

As expected, Snow White was red. But to their surprise, the spectrum revealed that the surface was covered in water ice. "That was a big shock," Brown says. "Water ice is not red." Although ice is common in the outer solar system, it's almost always white.

There is, however, one other dwarf planet that's both red and covered with water ice: Quaoar, which Brown helped discover in 2002. Slightly smaller than Snow White, Quaoar is still big enough to have had an atmosphere and a surface covered with volcanoes that spewed an icy slush, which then froze solid as it flowed over the surface.

But because Quaoar isn't as big as dwarf planets like Pluto or Eris, it could not hold onto volatile compounds like methane, carbon monoxide, or nitrogen as long. A couple of billion years after Quaoar formed, it began to lose its atmosphere to space; now, all that remains is some methane. Over time, exposure to the radiation from space turned that methane—which consists of a carbon atom bonded to four hydrogen atoms—into long hydrocarbon chains, which look red. Like the frost that covers a lawn on a cold morning, the irradiated methane sits on Quaoar's icy surface, giving it a rosy hue.

The spectrum of 2007 OR10 looks similar to Quaoar's, suggesting that what happened on Quaoar also happened on 2007 OR10. "That combination—red and water—says to me, 'methane,'" Brown explains. "We're basically looking at the last gasp of Snow White. For four and a half billion years, Snow White has been sitting out there, slowly losing its atmosphere, and now there's just a little bit left."

Although Snow White's spectrum clearly shows the presence of water ice, Brown says, the evidence for methane is not yet definitive. To find out, the astronomers will have to use a big telescope like the one at the Keck Observatory. If it turns out that Snow White does indeed have methane, it will join Quaoar as one of only two dwarf planets that straddle the border between the handful of objects large enough to hold onto volatile compounds, and the smaller bodies that make up the vast majority of KBOs.

Another task, Brown says, is to give the dwarf planet an official name, since "Snow White" was just a nickname he and his colleagues used. Besides, the moniker no longer makes sense for describing this very red object. Before the discovery of water ice and the possibility of methane, "2007 OR10" might have sufficed for the astronomy community, since it didn't seem noteworthy enough to warrant an official name. "We didn't know Snow White was interesting," Brown says. "Now we know it's worth studying."

To learn more, visit www.mikebrownsplanets.com. The research described in the Astrophysical Journal Letters paper, "The surface composition of large Kuiper Belt Object 2007 OR10," was supported by the NASA Planetary Astronomy program.

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New Data Shows El Mayor—Cucapah Earthquake Was Simple on Surface, Complicated at Depth

PASADENA, Calif.— Like scars that remain on the skin long after a wound has healed, earthquake fault lines can be traced on Earth's surface long after their initial rupture. Typically, this line of intersection between the area where the fault slips and the ground is more complicated at the surface than at depth. But a new study of the April 4, 2010, El Mayor–Cucapah earthquake in Mexico reveals a reversal of this trend. While the fault involved in the event appeared to be superficially straight, the fault zone is warped and complicated at depth.

The study—led by researchers at the California Institute of Technology (Caltech) and documenting findings from the magnitude 7.2 event, which was centered in the Baja California state of Mexico—is available online in the journal Nature Geoscience.

The El Mayor–Cucapah earthquake happened along a system of faults that run from Southern California into Mexico, cutting through the Cucapah mountain range and across the Colorado River delta. This system of faults forms a portion of the plate boundary between the Pacific Plate and the North American Plate. Two main segments of the fault tilt downward steeply from the surface at opposing angles: the northwestern half angles downward beneath the Mexicali Valley, whereas the southeastern half angles away from the valley.

In a standard model, transform plate boundary structures—where two plates slide past one another—tend to be vertically oriented, which allows for lateral side-by-side shear fault motion. In the case of this quake, however, lead author Shengji Wei, a postdoctoral scholar in geophysics, and colleagues showed that the 120-kilometer-long rupture involved angled, non-vertical faults and that the event was initiated on a connecting extension fault between the two segments.

"Although the surface trace is nearly linear, we found that the event, which started with a smaller quake, happened mainly on two faults with opposite dipping directions," says Wei.

In fact, the seismic rupture traveled through a relatively complicated set of preexisting faults that are dipping in various directions. "It was really surprising to see a straight fault trace that cuts through the Colorado delta and the rugged topography of the Sierra Cucapah as a result of this event," says Jean-Philippe Avouac, director of Caltech's Tectonics Observatory and principal investigator on the study.   

The team used interferometric synthetic aperture radar (InSAR) and optical images gathered from satellites, global positioning system (GPS) data, and seismological data to study the rupture process. By combining the GPS data and remote sensing techniques—which provide measurements of surface displacement—and seismological techniques to study the ground vibrations generated by the temblor, the researchers were able to produce an extremely well-resolved model of the earthquake.

The model describes the geometry of the faults that broke during the quake and the time evolution of the rupture. It shows that once the earthquake began with an extensional deep break that pulled the two segments apart, it spread bilaterally to the northwest and the southeast. As the rupture spread northwestward, it continued to break erratically through the faults below the Cucapah mountain range. Simultaneously, the rupture spread towards the southeast, breaking a fault that had been covered over by a blanket of sediments that forms the Colorado River delta.

"High-resolution satellite radar images allowed us to locate a previously unmapped fault—the Indiviso Fault—beneath the Colorado River Delta that had been buried by river sediments since its last earthquake," says NASA's Jet Propulsion Laboratory (JPL) geophysicist Eric Fielding, who was a coauthor of the study. "This fault moved up to 16 feet, or 5 meters, in the April 4, 2010, earthquake."

Wei says that since the new analysis indicates the responsible fault is more segmented deep down than its straight surface trace suggests, the evolution and extent of this earthquake's rupture could not have been accurately anticipated from the surface geology alone. Anticipating the characteristics of an earthquake that would likely happen on a young fault system (like the event in the study) is a challenge, since the geologic structures involved in the new fault system are not clear enough.

According to Avouac, the data can also be used to illustrate the process by which the plate boundary—which separates the Pacific Plate from North America— evolves and starts connecting the Gulf of California to the Elsinore fault in Southern California.

"We may have to wait for a couple of million years to clearly see the active fault zone in the topography, as we can now see further north in Central California, for example," Avouac says. "Earthquakes with magnitude 7.5 and lower are probably typical of this kind of younger fault zone, while fault zones with a longer geological history and simpler fault geometries are more prone to produce larger ruptures."

This is important information, since damage estimates from the earthquake, which mostly affected agribusinesses, topped $440 million in the Mexicali Valley of Baja California and $90 million in the Imperial Valley of California.

The paper, "Superficial simplicity of the 2010 El Mayor–Cucapah earthquake of Baja California in Mexico," appeared as an advanced online publication on July 31 in the journal Nature Geoscience. Sebastien Leprince, Anthony Sladen, Don Helmberger, Egill Hauksson, Risheng Chu, and Mark Simons, all from the Division of Geological and Planetary Sciences at Caltech; Kenneth Hudnut, geophysicist at the United States Geological Survey (USGS) in Pasadena; Thomas Herring, professor of geophysics at MIT; and Richard Briggs, research geologist at USGS in Golden, Colorado, also contributed to the study, which was funded by the National Science Foundation, USGS, the Gordon and Betty Moore Foundation, NASA and the Southern California Earthquake Center.

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Stolper Elected to Great Britain's Royal Society

PASADENA, Calif.—Edward M. Stolper, provost of the California Institute of Technology (Caltech) and William E. Leonard Professor of Geology, has been named a Foreign Member of Great Britain's Royal Society. He is one of eight scientists elected in 2011. Stolper's election brings to six the number of foreign members of the Royal Society currently on the Caltech faculty.

Membership in the Royal Society is bestowed each year on a small number of the world's scientists. The oldest scientific academy in existence, the Royal Society was established in 1660 under the patronage of King Charles II for the purpose of "improving natural knowledge," and helped usher in the age of modern science. Today, the Society seeks to promote science leaders who champion innovation for the benefit of humanity and the planet.

The Society cited Stolper for his "experimental and theoretical work on melting and igneous processes on the Earth, Mars, and asteroids." The citation noted Stolper's development of the so-called sandwich method for determining the phase equilibria that control melting in the mantles of Earth and other planets and his development of the first quantitative model of water speciation in glasses and silicate melts, which showed that H2O dissolves in magmas as both hydroxyl groups and as molecular water. The Society's announcement also recognized Stolper as the first to propose that a small but distinctive group of igneous meteorites (the "SNC" group, which comprises the shergottite, nakhlite, and chassignite meteorites) come from the planet Mars; the first to show that certain dense silicate minerals can float relative to coexisting silicate liquids at high pressures due to the very high compressibilities of magmas, a finding with implications for the differentiation of large silicate planets; and the first to demonstrate a linear relationship between the extent of melting in Earth's mantle and water content through studies of magmas that have erupted in the Mariana trough and in other subduction zone environments. 

In addition, Stolper was recently elected a foreign member of the Academia Europaea ("The Academy of Europe"), a pan-European academy of humanities, letters, and sciences founded in 1988 to promote learning, education, and research. Members are drawn from the physical sciences and technology, biological sciences and medicine, mathematics, the letters and humanities, social and cognitive sciences, economics, and the law.

A member of Caltech's faculty since 1979, Stolper was named the William E. Leonhard Professor of Geology in 1990. He served as chair of the Division of Geological and Planetary Sciences from 1994 to 2004. He was interim provost in 2004, and in 2007 he was named provost, the chief academic officer of the Institute.

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Genesis samples reveal new clues about sun's chemical makeup

Ever since a crash landing on Earth grounded NASA's Genesis mission in 2004, scientists have been gathering, cleaning, and analyzing solar wind particles collected by the spacecraft. Now, two new studies published in Science reveal that Earth's chemistry is less like the sun's than previously thought.

Because the sun, moon, planets, and meteorites in our solar system started from the same cloud of dust and gases, a long-held assumption has been that these objects share the same chemistry. However, data obtained from samples of material ejected from the outer portion of the sun, which Genesis collected over a two-year time period, show differences in isotopic content of both oxygen and nitrogen when compared to the Earth's atmosphere. Isotopes are variants of a particular element that differ and are identified by their number of neutrons.

One study found that the percentage of oxygen-16—the most prevalent kind of oxygen isotope in the solar system—was slightly higher in solar wind samples than it is in air on Earth and the other terrestrial planets. The second study examined nitrogen isotopes and found that although both the sun and Jupiter appear to have slightly more nitrogen-14 than Earth, they have 40 percent less N-15. These variations offer insight into how our solar system evolved.

"The sun houses more than 99 percent of the material currently in our solar system, so it's a good idea to get to know it better," said Don Burnett, professor of nuclear geochemistry, emeritus, at Caltech, and Genesis Principal Investigator. "While it was more challenging than expected, we have answered some important questions, and like all successful missions, generated plenty more."

Burnett says that the Genesis team will continue to mine the salvaged spacecraft for usable samples. To learn more about Genesis and keep up-to-date on new research findings from the mission, visit www.nasa.gov/mission_pages/genesis/main/index.html.

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