Recent News on the Debate over Pluto's Planethood

Earlier this month, Eris—the distant world first discovered by Caltech's Mike Brown and colleagues back in 2005, paving the way for the eventual demotion of Pluto from planet to dwarf planet—passed fortuitously in front of a faint star in the constellation Cetus. That passage, or occultation, allowed the first direct measurement of Eris's size. And it produced a surprising result that reignited—in the media, at least—the debate over Pluto's planethood: Eris and Pluto are, within the uncertainties, essentially the same size. But since Eris is 27% more massive than Pluto, Eris is substantially denser. The two objects, once thought to be slightly differently sized twins, are in fact very different.

But does this really mean that Pluto's demotion was unjustified?

Certainly not, Brown says. Pluto was not demoted simply because it was thought to be smaller than Eris, he explains, so even though the two are now known to be essentially the same size, the logic behind keeping both of them out of the planetary club remains the same. What is different, he says, is how much more interesting this discovery makes Eris.

"When we first discovered Eris, we thought it was just a slightly larger copy of Pluto. Finding a slightly larger copy doesn't teach you much more than the original, so even though Eris was always important to the public, it never garnered that much attention from astronomers, " Brown says. "Now that we know it has a substantially different composition from Pluto, we are scrambling to figure out ways to understand how a planetary system can produce such seemingly different objects out of what is supposed to be the same material."

Read more about these new observations in Brown's blog, "Mike Brown's Planets."

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Kathy Svitil
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Caltech Receives $10 Million in Gifts to Help Launch New Terrestrial Hazard Center

Center will focus on developing innovative ways to reduce the risks and costs of natural hazards

PASADENA, Calif.-In an effort to find ways to minimize the damage caused by natural hazards, the California Institute of Technology (Caltech) has established the Terrestrial Hazard Observation and Reporting Center (THOR), funded by $6.7 million from Foster and Coco Stanback of Irvine, California, and $3.35 million from the Gordon and Betty Moore matching program.

THOR will have the unique mandate of bringing together-under one program-innovative efforts to reduce the risks and costs associated with natural hazards. The center will span two divisions at Caltech, Geological and Planetary Sciences (GPS) and Engineering and Applied Science (EAS).

The study of natural hazards and solutions is ordinarily undertaken in separate academic disciplines with little intellectual interaction. THOR will provide a new focal point that will unify these efforts and allow investigators to focus on critical societal issues.

"From the current flooding in Pakistan, to the recent earthquake in Haiti, to the constant threat of wildfires in our own backyard, we are consistently reminded of the devastating impact natural hazards can have on society," says Caltech president Jean-Lou Chameau. "Now, with the generous support of Foster and Coco Stanback, Caltech scientists and engineers will be able to study these critical issues in a unique interdisciplinary environment.  THOR will help communities around the world determine how to best prepare for, anticipate, and respond to various natural hazards, hopefully saving lives in the process." 

Natural hazards that will fall under THOR's purview include global climate change, earthquakes, tsunamis, landslides, wildfires, and extreme weather events such as droughts, among others.

By providing support for the development of techniques and physical inventions, THOR will focus on practical societal aspects of natural hazards and their public policy implications.

For instance, THOR may help guide the distribution of limited resources following a major hazard such as an earthquake or tsunami, or lead to early-warning systems.

"The interdisciplinary and interactive nature of engineering at Caltech allows us to translate scientific knowledge and discovery into applications with direct societal impact," says Ares Rosakis, the von Kármán Professor of Aeronautics, professor of mechanical engineering, and chair of the division of Engineering and Applied Science. "One of the areas of pioneering research and innovation made possible by THOR is seismo-engineering. The boundaries of seismo-engineering are fuzzy ones and lie exactly in the interface between seismology and earthquake engineering.  We are delighted to have the opportunity to explore these boundaries."

Caltech has a number of highly visible areas of expertise that already touch on natural-hazard issues, including the Seismological Laboratory, the Linde Center for Global Environmental Science, missions of the Caltech-managed Jet Propulsion Laboratory (JPL) that provide critical high-precision data on Earth's climate and environment, multiple studies supported by the Keck Institute for Space Studies (KISS) focused on future Earth-observing missions, and the Resnick Institute for Science, Energy, and Sustainability.   

"The THOR center will provide a unique platform for collaboration among scientists, students, and policymakers, empowering them with the extensive resources of Caltech and the Jet Propulsion Laboratory," says THOR donor Foster Stanback. "By linking our eyes in the sky with the many eyes on the ground, we will be far better prepared to anticipate, mitigate, and eliminate many environmental hazards."

THOR's attention and resources will be applied in several ways, including the dissemination of the results of work supported by THOR; supporting efforts to transfer ideas and technologies that show promise of practical implementation; and prioritizing, seeding, and nurturing ideas encompassing research activities, along with the invention of technologies.

"THOR will give faculty in GPS and EAS the opportunity to develop innovative new ways to help mitigate the consequences and costs of the natural hazards society faces, from climate change to earthquakes to water scarcity," says Ken Farley, the W.M. Keck Foundation Professor of Geochemistry and chair of the division of Geological and Planetary Sciences. "This very applied research is difficult to support from federal sources, so my hope is that the gift will catalyze entirely new endeavors. THOR will also allow us to bring to our educational program a new focus on the societal and policy implications and relevance of our work."

The center will be housed within the newly renovated Linde + Robinson Laboratory on the Caltech campus.

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Jon Weiner
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Caltech Mineral Physicists Find New Scenery at Earth's Core-Mantle Boundary

PASADENA, Calif.—Using a diamond-anvil cell to recreate the high pressures deep within the earth, researchers at the California Institute of Technology (Caltech) have found unusual properties in an iron-rich magnesium- and iron-oxide mineral that may explain the existence of several ultra-low velocity zones (ULVZs) at the core-mantle boundary. A paper about their findings was published in a recent issue of Geophysical Research Letters (GRL).

ULVZs—which were first discovered in the early 1990s by researchers at Caltech led by Donald V. Helmberger, Smits Family Professor of Geological and Planetary Sciences—are found in a patchwork distribution just above the core-mantle boundary, which is located at a depth of 2,900 kilometers. In the ULVZs, which range from a few kilometers to tens of kilometers in depth and are up to 100 kilometers across, the velocities of seismic waves slow down by up to 30 percent.

Previously, geophysicists had suggested that the ULVZs might be composed of liquid-bearing, partially melted materials; in this region of the lower mantle, the earth is solid—but plastic and flowing—rock. The idea was that if these rocks contained some liquid, seismic waves would propagate more slowly through them. And, indeed, "the area is very hot and close to the core," says Jennifer M. Jackson, assistant professor of mineral physics at Caltech and coauthor of the GRL paper. The catch, she says, "is that the temperature and composition of this region are not very well known." In addition, she says, "these ULVZs are not always associated with surface hot spots" such as the Hawaiian islands.

Instead of being patches of partially melted (i.e., liquid-bearing) rock, the ULVZs—Jackson and her colleagues believe—are composed of an entirely solid, compositionally distinctive rock type with unusual properties that cause sound waves to slow down. "What we're suggesting here is that many ULVZs—it need not be all of them—are likely to be solid, not molten," Jackson says. 

In reaching this conclusion, Jackson and her team studied the properties of iron-rich magnesium-iron oxides [(Mg, Fe)O]—similar to the mineral periclase known at the earth's surface—using specially prepared diamond-anvil cells. Within the piston-like chamber of the 4-inch-tall cell, two semiflawless natural diamonds—a quarter of a carat each—were squeezed together, sandwiching a small sample of the oxide and proportionally increasing its pressure.

After the pressurized samples were created, they were taken to the Advanced Photon Source at Argonne National Laboratory in Illinois and exposed to X-rays, causing the scattering of photons at energies related to the speed at which sound would travel through. 

Jackson and her colleagues conducted the measurements at pressures ranging from ambient pressure (at Earth's surface) up to 121 Gigapascals (GPa)—or over 17 million pounds per square inch, equivalent to about 2700 km depth. "The measurements stopped at pressures where the diamond-anvils broke," Jackson says. 

Normally, solid materials increase in stiffness under increasing pressure, causing sound waves to travel at higher and higher velocities. But in iron-rich (Mg,Fe)O, the sound velocities took a surprising and significant dip of about 10 percent at just under 28 GPa. The sound velocities in the minerals did not return to their ambient-pressure levels until pressures of 50 to 60 GPa were reached.

To their surprise, the researchers found they could compress the iron-rich mineral to very high pressures and very high densities, "and yet it is still highly compressible" Jackson says. In fact, even at 121 GPa, sound velocities in the mineral were still much lower than in other known mantle materials. "It's quite unusual to have a solid this compressible under these pressures. Compared to silicate"—the main constituent of Earth's crust—"at the same pressures, it's like squishing a pat of butter between two bricks."

Jackson and her colleagues suspect that the velocity drops in this particular mineral are related to magnetic transitions that can make iron-rich oxides more compressible than many silicates. "Silicate acts more like a very stiff spring; iron-rich oxide is like a very weak spring," she explains. With increasing pressure, "the iron-oxide goes through a series of complex magnetic transitions that couple to its sound waves"—and thus explain the unusually low velocities, even at extremely high pressures. "But," she adds, "because the mineral is so iron-rich, it is likely only to exist near the core."

While the new result does not rule out partial melting as a cause of some ULVZs, Jackson says, "iron-rich periclase certainly provides one of the most robust explanations so far."

"The composition of the boundary layer between the earth's liquid outer core and silicate mantle not only influences the current thermal and chemical evolution of the earth's interior, but may hold the key to unlocking the planet's past thermo-chemical evolution," she says. "The iron-rich periclase patches may be fossil remnants of large-scale melting events occurring billions of years ago inside the earth. Having an iron-rich oxide in contact with the earth's core would facilitate propagation of the planet's magnetic field and contribute to the dynamic coupling between the core and the mantle."

The paper, "Very low sound velocities in iron-rich (Mg,Fe)O: Implications for the core-mantle boundary," was coauthored by Caltech graduate student June K. Wicks and Wolfgang Sturhahn, formerly at Argonne National Laboratory and now at the Jet Propulsion Laboratory. The work was funded by the National Science Foundation and the U.S. Department of Energy's Office of Basic Energy Sciences.

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Kathy Svitil
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New View of Tectonic Plates

PASADENA, Calif.—Computational scientists and geophysicists at the University of Texas at Austin and the California Institute of Technology (Caltech) have developed new computer algorithms that for the first time allow for the simultaneous modeling of the earth's mantle flow, large-scale tectonic plate motions, and the behavior of individual fault zones, to produce an unprecedented view of plate tectonics and the forces that drive it.

A paper describing the whole-earth model and its underlying algorithms will be published in the August 27 issue of the journal Science and also featured on the cover.

The work "illustrates the interplay between making important advances in science and pushing the envelope of computational science," says Michael Gurnis, the John E. and Hazel S. Smits Professor of Geophysics, director of the Caltech Seismological Laboratory, and a coauthor of the Science paper.

To create the new model, computational scientists at Texas's Institute for Computational Engineering and Sciences (ICES)—a team that included Omar Ghattas, the John A. and Katherine G. Jackson Chair in Computational Geosciences and professor of geological sciences and mechanical engineering, and research associates Georg Stadler and Carsten Burstedde—pushed the envelope of a computational technique known as Adaptive Mesh Refinement (AMR).

Partial differential equations such as those describing mantle flow are solved by subdividing the region of interest (such as the mantle) into a computational grid. Ordinarily, the resolution is kept the same throughout the grid. However, many problems feature small-scale dynamics that are found only in limited regions. "AMR methods adaptively create finer resolution only where it's needed," explains Ghattas. "This leads to huge reductions in the number of grid points, making possible simulations that were previously out of reach.”

"The complexity of managing adaptivity among thousands of processors, however, has meant that current AMR algorithms have not scaled well on modern petascale supercomputers," he adds. Petascale computers are capable of one million billion operations per second. To overcome this long-standing problem, the group developed new algorithms that, Burstedde says, "allows for adaptivity in a way that scales to the hundreds of thousands of processor cores of the largest supercomputers available today." 

With the new algorithms, the scientists were able to simulate global mantle flow and how it manifests as plate tectonics and the motion of individual faults. According to Stadler, the AMR algorithms reduced the size of the simulations by a factor of 5,000, permitting them to fit on fewer than 10,000 processors and run overnight on the Ranger supercomputer at the National Science Foundation (NSF)-supported Texas Advanced Computing Center.  

A key to the model was the incorporation of data on a multitude of scales. "Many natural processes display a multitude of phenomena on a wide range of scales, from small to large," Gurnis explains. For example, at the largest scale—that of the whole earth—the movement of the surface tectonic plates is a manifestation of a giant heat engine, driven by the convection of the mantle below. The boundaries between the plates, however, are composed of many hundreds to thousands of individual faults, which together constitute active fault zones. "The individual fault zones play a critical role in how the whole planet works," he says, "and if you can't simulate the fault zones, you can't simulate plate movement"—and, in turn, you can't simulate the dynamics of the whole planet.

In the new model, the researchers were able to resolve the largest fault zones, creating a mesh with a resolution of about one kilometer near the plate boundaries. Included in the simulation were seismological data as well as data pertaining to the temperature of the rocks, their density, and their viscosity—or how strong or weak the rocks are, which affects how easily they deform. That deformation is nonlinear—with simple changes producing unexpected and complex effects.

"Normally, when you hit a baseball with a bat, the properties of the bat don't change—it won't turn to Silly Putty. In the earth, the properties do change, which creates an exciting computational problem," says Gurnis. "If the system is too nonlinear, the earth becomes too mushy; if it's not nonlinear enough, plates won't move. We need to hit the 'sweet spot.'"

After crunching through the data for 100,000 hours of processing time per run, the model returned an estimate of the motion of both large tectonic plates and smaller microplates—including their speed and direction. The results were remarkably close to observed plate movements.

In fact, the investigators discovered that anomalous rapid motion of microplates emerged from the global simulations. "In the western Pacific," Gurnis says, "we have some of the most rapid tectonic motions seen anywhere on Earth, in a process called 'trench rollback.' For the first time, we found that these small-scale tectonic motions emerged from the global models, opening a new frontier in geophysics."

One surprising result from the model relates to the energy released from plates in earthquake zones. "It had been thought that the majority of energy associated with plate tectonics is released when plates bend, but it turns out that's much less important than previously thought," Gurnis says. "Instead, we found that much of the energy dissipation occurs in the earth's deep interior. We never saw this when we looked on smaller scales."

The paper, "The Dynamics of Plate Tectonics and Mantle Flow: From Local to Global Scales," was also coauthored by Lucas C. Wilcox of the University of Texas at Austin and Laura Alisic of Caltech. The work was supported by the NSF, the Department of Energy's Office of Science, and—at the Caltech Tectonics Observatory—by the Gordon and Betty Moore Foundation. 

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Kathy Svitil
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NRC Recommends Three Astronomy/Astrophysics Projects with Potential Major Caltech Roles

PASADENA, Calif.—In an announcement August 13 at the National Academies in Washington, D.C., the National Research Council (NRC) recommended three space- and ground-based astronomy and astrophysics projects with potential major roles for researchers at the California Institute of Technology (Caltech): CCAT, a submillimeter telescope to be erected in the Chilean Andes, which will help unravel the cosmic origins of stars, planets, and galaxies; the Laser Interferometer Space Antenna (LISA), designed to detect gravitational waves, ripples in the fabric of space and time formed by the most violent events in the universe; and the development of a Giant Segmented Mirrored Telescope (GSMT)—the Thirty Meter Telescope (TMT) being one of two such telescopes under development—which will yield the clearest and deepest view of the universe.

The recommendations were the result of the Astro2010 a decadal survey, in which a panel of experts was convened by the NRC to look at the coming decade and prioritize research activities in astronomy and astrophysics, as well as activities at the interface of these disciplines with physics.

"It is particularly gratifying to see that Caltech faculty are prepared to play leading roles in three of the major projects identified by the Astro2010 study," says Tom Soifer, professor of physics, director of the Spitzer Science Center, and chair of the Division of Physics, Mathematics and Astronomy at Caltech. "Many of the important discoveries in the coming decades will be based on CCAT, TMT, and LISA, and our deep involvement in these projects will ensure that Caltech remains a vibrant, exciting center for astrophysics."

CCAT

CCAT was recommended for an immediate start. CCAT is a collaboration between Caltech and the Jet Propulsion Laboratory (JPL), managed by Caltech for NASA; Cornell University; the University of Colorado; and consortia in both Germany and Canada. It will be a 25-meter telescope located on a mountain site in Chile at an elevation of 18,500 feet above sea level. Taking advantage of recent advances in detector technology, CCAT will employ cameras and spectrometers to survey the sky at millimeter and submillimeter wavelengths, providing an unprecedented combination of sensitivity and resolution across a wide field of view. CCAT will reveal young galaxies, stars, and solar systems enshrouded in clouds of dust that make these objects very faint or invisible at other wavelengths.

"We are making rapid progress on all fronts—in detectors, instruments, and new facilities—and this is leading to important scientific discoveries," says Jonas Zmuidzinas, Merle Kingsley Professor of Physics at Caltech, director of the Microdevices Laboratory at JPL, and a CCAT project scientist. "With CCAT, we will gain real insight into the evolution of stars and galaxies."

According to Riccardo Giovanelli, CCAT director and professor of astronomy at Cornell University, "CCAT will allow us to explore the process of formation of galaxies, which saw its heyday about a billion years after the Big Bang, some 13 billion years ago; to peek into the interior of the dusty molecular clouds within which stars and planets form; and to survey the pristine chunks of material left intact for billions of years on the outskirts of our solar system." 

CCAT is a natural complement to the international Atacama Large Millimeter Array (ALMA) project now under construction in Chile, which will provide detailed, high-resolution images of individual objects over narrow fields of view. This complementarity provides a strong impetus to begin construction of CCAT as soon as possible. Indeed, as Nobel Laureate and CCAT Design Review Committee Chair Robert W. Wilson noted, "CCAT is very timely and cannot wait."

This sentiment was echoed in the Decadal Review Committee's report, which stated that "CCAT is called out to progress promptly to the next step in its development because of its strong science case, its importance to ALMA, and its readiness." The Committee recommended federal support for 33 percent of the construction cost for CCAT, as well as support in the operations phase.

LISA

The decadal survey recommended LISA as one of NASA's next major space missions, to start in 2016 in collaboration with the European Space Agency (ESA). In the U.S. the LISA project is managed by the NASA Goddard Space Flight Center and includes significant participation by JPL, which is managed by Caltech for NASA.

LISA is designed to be complementary to the ground-based observatories (such as the Laser Interferometer Gravitational Wave Observatory, or LIGO) that currently are actively searching for signs of gravitational waves, which carry with them information about their origins and about the nature of gravity that cannot be obtained using conventional astronomical tools.

The LISA instrument will consist of three spacecraft in a triangular configuration with 5-million-kilometer arms moving in an Earth-like orbit around the sun. Gravitational waves from sources throughout the universe will produce slight oscillations in the arm lengths (changes as small as about 10 picometers, or 10 million millionths of a meter). LISA will capture these motions using laser links to monitor the displacements of gold–platinum test masses floating inside the spacecraft. It is slated for launch in the early 2020s. The instrument will observe gravitational waves in a lower frequency band (0.1 milliHertz to 1 Hertz) than that detectable by LIGO and other ground-based instruments and will sense ripples coming simultaneously from tens of thousands of sources in every direction.

The survey recommended LISA because of the expectation that observations of gravitational waves in space will answer key scientific questions about the astrophysics of the cosmic dawn and the physics of the universe.

"We are very pleased with the NRC's recognition of LISA's revolutionary research opportunities in astrophysics and fundamental physics and we are looking forward to unveiling a new window on the universe by observing thousands of gravitational wave sources," says Tom Prince, professor of physics at Caltech, senior research scientist at the Jet Propulsion Laboratory (JPL), and the U.S. chair of the LISA International Science Team.

GSMT

The decadal survey rated the development of a Giant Segmented Mirrored Telescope as a high priority. The TMT is one of two such telescopes under development by consortia with major involvement by private and public entities in the U.S., including Caltech.

Building on the success of the twin Keck telescopes, the core technology of TMT will be a 30-meter segmented primary mirror. This will give TMT nine times the collecting area of today's largest optical telescopes and three-times-sharper images. The TMT has begun full-scale polishing of the 1.4-meter mirror blanks that will make up the primary mirror. TMT also has developed many of the essential prototype components for the telescope, including key adaptive optics technologies and the support and control elements for the 492 mirror segments.

The TMT project is an international partnership among Caltech, the University of California, and the Association of Canadian Universities for Research in Astronomy, joined by the National Astronomical Observatory of Japan, the National Astronomical Observatories of the Chinese Academy of Sciences, and the Department of Science and Technology of India.

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Kathy Svitil
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Caltech, Canadian Space Agency Awarded NASA Project to Develop Spectrometer Headed to Mars

Instrument will look for evidence of life and volcanic activity on Mars; will fly aboard ExoMars Trace Gas Orbiter in 2016

PASADENA, Calif.—The California Institute of Technology (Caltech) and the Canadian Space Agency (CSA) announced today that they will be partnering on the development of the Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS) instrument to be flown aboard the ExoMars Trace Gas Orbiter when it launches in 2016.

The project will be funded by a grant from NASA, with additional support coming from the CSA.

NASA participation in the ExoMars Trace Gas Orbiter is managed by the Jet Propulsion Laboratory, a division of Caltech, in partnership with the European Space Agency.

"The ExoMars investigation is designed to study the composition of Mars's atmosphere, with a focus on biogenically or volcanically derived trace gases," says Paul Wennberg, the R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering at Caltech and director of the Ronald and Maxine Linde Center for Global Environmental Science. Wennberg is the principal investigator on the MATMOS team.

The ExoMars Orbiter's circular path around Mars will point the MATMOS telescope at the center of the sun as the spacecraft goes into orbital sunrise and sunset. During these periods, as the sun sets and rises through the atmosphere, MATMOS will take spectra of the sunlight, recording the absorption of numerous gases. The sun's long path length through the Martian atmosphere will allow MATMOS to measure the trace gases with very high sensitivity, notes Wennberg.

"If you take the spectra fast," says Geoffrey Toon, senior research scientist at JPL and a visiting associate in planetary sciences at Caltech, "you can measure the gas abundance at many different heights above the planet —70 measurements as the sun rises, and 70 as it sets."

Among the gases of interest to the team are those "diagnostic of active geological and biogenic activity," says Wennberg—gases like methane, as well as carbon, sulfur, and nitrogen-containing molecules, sulfur dioxide, and hydrogen sulfide.

MATMOS will be so exquisitely sensitive, says Wennberg, that it will be able to measure the concentrations of these gases down to parts per trillion.

"We did a calculation which shows that the microbial community found in three cows' bellies would produce an amount of methane that, in the Mars atmosphere, would be observable by MATMOS," says Mark Allen, principal scientist at JPL and a visiting associate in planetary sciences at Caltech.

MATMOS is based on the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment, developed by JPL, and the Atmospheric Chemistry Experiment–Fourier Transform Spectrometer (ACE–FTS), pioneered by University of Waterloo and the Canadian Space Agency. The ATMOS instrument has flown four times on the Space Shuttle since 1985. ACE–FTS was launched in 2003 and is still operational.

"MATMOS is an excellent instrument and an opportunity for a great partnership," says CSA Senior Planetary Scientist Victoria Hipkin, co-principal investigator on the MATMOS project. "We have taken the optical systems of one of Canada's flagship satellite instruments (Scisat ACE–FTS) and combined it with state-of-the-art data processing from the US (JPL's ATMOS and MrkIV). Our team—with US and Canadian leadership and Canadian, US, French, and UK members—is looking forward to providing fundamental data about this fascinating planet."

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Lori Oliwenstein
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Caltech Team Finds Evidence of Water in Moon Minerals

PASADENA, Calif.-That dry, dusty moon overhead? Seems it isn't quite as dry as it's long been thought to be. Although you won't find oceans, lakes, or even a shallow puddle on its surface, a team of geologists at the California Institute of Technology (Caltech), working with colleagues at the University of Tennessee, has found structurally bound hydroxyl groups (i.e., water) in a mineral in a lunar rock returned to Earth by the Apollo program.

Their findings are detailed in this week's issue of the journal Nature.

"The moon, which has generally been thought to be devoid of hydrous materials, has water," says John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, and a coauthor on the paper.

"The fact that we were able to quantitatively measure significant amounts of water in a lunar mineral is truly surprising," adds lead author Jeremy Boyce, a visitor in geochemistry at Caltech, and a research scientist at the University of California, Los Angeles.

The team found the water in a calcium phosphate mineral, apatite, within a basalt collected from the moon's surface by the Apollo 14 astronauts.

To be precise, they didn't find "water"-the molecule H2O. Rather, they found hydrogen in the form of a hydroxyl anion, OH-, bound in the apatite mineral lattice.

"Hydroxide is a close chemical relative of water," explains coauthor George Rossman, Caltech's Eleanor and John R. McMillan Professor of Mineralogy. "If you heat up the apatite, the hydroxyl ions will 'decompose' and come out as water."

The lunar basalt sample in which the hydrogen was found had been collected by the Apollo 14 moon mission in 1971; the idea to focus the search for water on this particular sample was promoted by Larry Taylor, a professor at the University of Tennessee in Knoxville, who sent the samples to the Caltech scientists last year.

"The moon has been considered to be bone dry ever since the return of the first Apollo rocks," Taylor notes. However, there are lunar volcanic deposits interpreted as having been erupted by expanding vapor. Although carbon dioxide and sulfur gases have generally been thought to dominate the expanding vapor, recent evidence from the study of the these deposits has suggested that water could also play a role in powering lunar volcanic eruptions.  The discovery of hydroxyl in apatite from lunar volcanic rocks is consistent with this suggestion.

The idea of looking for water in lunar apatite isn't new, Boyce notes. "Charles B. Sclar and Jon F. Bauer, geoscientists at Lehigh University, first noted that something was missing from the results of chemical analyses of apatite in 1975," he says. "Now, 35 years later, we have quantitative measurements-and it turns out, they were right. The missing piece was OH."

The Caltech team analyzed the lunar apatite for hydrogen, sulfur, and chlorine using an ion microprobe, which is capable of analyzing mineral grains with sizes much smaller than the width of a human hair. This instrument fires a focused beam of high-energy ions at the sample surface, sputtering away target atoms that are collected and then analyzed in a mass spectrometer. Ion microprobe measurements demonstrated that in terms of its hydrogen, sulfur, and chlorine contents, the lunar apatite in this sample is indistinguishable from apatites from terrestrial volcanic rocks. 

"We realized that the moon and the earth were able to make the same kind of apatite, relatively rich in hydrogen, sulfur and chlorine," Boyce says.

Does that mean the moon is as awash in water as our planet? Almost certainly not, say the scientists. In fact, the amount of water the moon must contain to be capable of generating hydroxyl-rich apatite remains an open question. After all, it's hard to scale up the amount of water found in the apatite-1600 parts per million or 0.16 percent by weight-to determine just how much water there is on the lunar landscape. The apatite that was studied is not abundant, and is formed by processes that tend to concentrate hydrogen to much higher levels than are present in its host rocks or the moon as a whole.

"There's more water on the moon than people suspected," says Eiler, "but there's still likely orders of magnitude less than there is on the earth."

Nonetheless, the finding is significant for what it implies about our moon's composition and its history. "These findings tell us that the geological processes on the moon are capable of creating at least one hydrous mineral," Eiler says. "Recent spectroscopic observations of the moon showed that hydrogen is present on its surface, maybe even as water ice.  But that could be a thin veneer, possibly hydrogen brought to the moon's surface by comets or solar wind. Our findings show that hydrogen is also part of the rock record of the moon, and has been since early in its history."

Beyond that, Eiler continues, "it's all a great big question mark. We don't know whether these were igneous processes,"-in which rocks are formed by solidification of molten lava-"or metamorphic"-in which minerals re-crystallize or change in change in chemistry without melting. "They're both on the table as possible players."

In addition to Boyce, Eiler, Rossman, and Taylor, other authors on the Nature paper, "Lunar apatite with terrestrial volatile abundances," include Research Assistant Professor Yang Liu from the University of Tennessee in Knoxville; Edward Stolper, Caltech's William E. Leonhard Professor of Geology, and Yunbin Guan, manager of Caltech's ion microprobe laboratory. 

Their work was funded by grants from NASA's Cosmochemistry Program, the National Science Foundation, and the Gordon and Betty Moore Foundation.

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Lori Oliwenstein
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Caltech Scientists Measure Changing Lake Depths on Titan

PASADENA, Calif.—On Earth, lake levels rise and fall with the seasons and with longer-term climate changes, as precipitation, evaporation, and runoff add and remove liquid. Now, for the first time, scientists have found compelling evidence for similar lake-level changes on Saturn's largest moon, Titan—the only other place in the solar system seen to have a hydrological cycle with standing liquid on the surface.

Using data gathered by NASA's Cassini spacecraft over a span of four years, the researchers—led by graduate student Alexander G. Hayes of the California Institute of Technology (Caltech) and Oded Aharonson, associate professor of planetary science at Caltech—have obtained two separate lines of evidence showing roughly a 1 meter per year drop in the levels of lakes in Titan's southern hemisphere. The decrease is the result of the seasonal evaporation of liquid methane from the lakes—which, because of Titan's frigid temperatures (roughly minus 300 degrees Fahrenheit at the poles), are composed largely of liquid methane, ethane, and propane.

"It's really exciting because, on this distant object, we're able to see this meter-scale drop in lake depth," says Hayes. "We didn't know Cassini would even be able to see these things."

One of the lakes—Ontario Lacus (named after Earth's Lake Ontario, which is of comparable size) —is the southern hemisphere's largest lake, and was the first lake to be observed on the moon. In a paper submitted to the journal Icarus, Hayes, Aharonson, and their colleagues report that the shoreline of Ontario Lacus receded by about 10 kilometers (6 miles) from June 2005 to July 2009, a period of time that represents mid-summer to fall in Titan's southern hemisphere. (One Titan year lasts 29.5 Earth years.)

Ontario Lacus and other southern-hemisphere lakes were analyzed using Synthetic Aperture Radar (SAR) image data from the Cassini spacecraft. In radar data, smooth features—such as lakes—appear as dark areas, while rougher features—such as mountain belts—appear bright. The intensity of the radar backscatter provides information about the composition and roughness of surface features. In addition to the SAR data, radar altimetry—which measures the time it takes for microwave signals bouncing off a surface to arrive back at the spacecraft—was collected across a transect of Ontario Lacus in December 2008.

"The combination of SAR and altimetry measurements across the transect gave information about the absorptive properties of the liquid, and argues that the liquids are relatively pure hydrocarbons made up of methane and ethane and not a gunky tar," Aharonson says.

"The liquid is not highly attenuating," explains Hayes, "which means it is fairly clear to radar energy—that is, transparent, like liquid natural gas." Because of this, radar can see through the liquid in Titan's lakes to a depth of several meters. "Then the radar hits the floor, and bounces back," he says. "Or, if the lake is deeper than a few meters, the radar is completely absorbed, producing a 'black' signature."

Once the liquid's optical properties were known, the researchers could use the radar data to "see" the lakebed underneath the liquid—at least, down to the depth where the signal is completely attenuated. "How far offshore you can see is determined by the local slope of the lakebed, or bathymetry," says Hayes. "This gave us the ability to take changes in radar signals and convert them to depths," and thus to calculate the slope of the lakebed around the entire lake.

"We were able to determine the bathymetry of the lake out to a depth of about 8 meters," he says. The lake is shallowest and most gently sloped along its southern edge, in areas where sediment is accumulating. Along its eastern shore, the slope of the lake is somewhat steeper. "This is what we are calling the 'beachhead,'" Hayes says. The slope is very steep along the lake's northern boundary, where it butts up against a range of mountains.

"The slope changes we see are consistent with the geology around the lake," Hayes says. The bathymetry measurements and their geologic correlations are discussed in a separate paper by Hayes, Aharonson, and colleagues, which has been accepted for publication in the Journal of Geophysical Research (JGR).

The researchers compared lake images obtained four years apart, and found that Ontario had shrunk. "The extent to which the lake has receded is related to the slope—i.e., where the lake is shallow, the liquid will have receded more," Hayes says. "This allows us to deduce the vertical height by which the lake depth has dropped, which is about 1 meter per year."

The researchers also analyzed the evaporation of methane from nearby lakes by comparing the radar signatures of these lakes as measured in December 2007 with data obtained in May 2009. Over that period, the "apparent darkness" of the lakes—indicating the presence of a radar-attenuating liquid—either decreased or disappeared entirely, which means that their liquid levels had been reduced. The researchers were able to calculate the drop in lake depth, "and we got the same result: 1 meter per year of liquid loss," Aharonson says.

Lakes in Titan's northern hemisphere—which is now entering spring—have also been covered multiple times by radar instruments, but so far no analogous changes have been conclusively detected.

That doesn't mean the changes haven't occurred, however. "We would expect it will happen, but we don't know how it would manifest in the data if the lakes in the north are significantly deeper. We'll continue to look for this effect with future radar images, to disentangle the seasonal variations from longer-term climate variations we previously have proposed." Aharonson says.

The work described in the two papers—"Transient Surface Liquid in Titan's Polar Regions from Cassini," which was submitted to Icarus, and "Bathymetry and Absorptivity of Titan's Ontario Lacus," which was accepted by JGR—was supported by the Cassini Project and NASA's Graduate Student Researchers Program, and was carried out in collaboration with members of the Cassini RADAR Science Team. The Cassini mission is managed by the Jet Propulsion Laboratory in Pasadena, California.

Writer: 
Kathy Svitil
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Caltech Geologist Investigates Canyon Carved in Just Three Days in Texas Flood

Study of how canyon formed offers insight into ancient flood events on Earth and Mars

PASADENA, Calif.—In the summer of 2002, a week of heavy rains in Central Texas caused Canyon Lake—the reservoir of the Canyon Dam—to flood over its spillway and down the Guadalupe River Valley in a planned diversion to save the dam from catastrophic failure. The flood, which continued for six weeks, stripped the valley of mesquite, oak trees, and soil; destroyed a bridge; and plucked meter-wide boulders from the ground. And, in a remarkable demonstration of the power of raging waters, the flood excavated a 2.2-kilometer-long, 7-meter-deep canyon in the bedrock.

According to a new analysis of the flood and its aftermath—performed by Michael Lamb, assistant professor of geology at the California Institute of Technology (Caltech), and Mark Fonstad of Texas State University—the canyon formed in just three days. 

A paper about the research appears in the June 20 advance online edition of the journal Nature Geoscience

Our traditional view of deep river canyons, such as the Grand Canyon, is that they are carved slowly, as the regular flow and occasionally moderate rushing of rivers erodes rock over periods of millions of years. 

Such is not always the case, however. "We know that some big canyons have been cut by large catastrophic flood events during Earth's history," Lamb says.

Streamlined islands sculpted by the flood and large boulders transported by the flood.
Credit: Michael Lamb/Caltech

Unfortunately, these catastrophic megafloods—which also may have chiseled out spectacular canyons on Mars—generally leave few telltale signs to distinguish them from slower events. "There are very few modern examples of megafloods," Lamb says, "and these events are not normally witnessed, so the process by which such erosion happens is not well understood." Nevertheless, he adds, "the evidence that is left behind, like boulders and streamlined sediment islands, suggests the presence of fast water"—although it reveals nothing about the time frame over which the water flowed.

This is why the Canyon Lake flood is so significant. "Here, we know that all of the erosion occurred during the flood," Lamb says. "Flood waters flowed for several weeks, but the highest discharge—during which the bulk of the erosion took place—was over a period of just three days." 

Boulders transported by the 2002 Canyon Lake flood.
Credit: Michael Lamb/Caltech

Lamb and Fonstad reached this conclusion using aerial photographs of the region taken both before and after the flood, along with field measurements of the topography of the region and measurements of the flood discharge. Then they applied an empirical model of the sediment-carrying capacity of the flood—that is, the amount of soil, rocks, boulders, and other debris carried by the flood to produce the canyon.

The analysis revealed that the rate of the canyon erosion was so rapid that it was limited only by the amount of sediment the floodwaters could carry. This is in contrast to models normally applied to rivers where the erosion is limited by the rate at which the underlying rock breaks and is abraded. 

The researchers argue that the rate of erosion was rapid because the flood was able to pop out and cart away massive boulders (a process called "plucking")—producing several 10- to 12-meter-high waterfalls that propagated upstream toward the dam, along with channels and terraces. The flood was able to pluck these boulders because the bedrock below the soil surface of the valley was already fractured and broken. 

The abrasion of rock by sediment-loaded waters—while less significant in terms of the overall formation of the canyon—produced other features, like sculpted walls, plunge pools at the bases of the waterfalls, and teardrop-shaped sediment islands. The sediment islands are particularly significant, Lamb says, because "these are features we see on Earth and on Mars in areas where we think large flow events have occurred. It's nice that here we're seeing some of the same features that we've interpreted elsewhere as evidence of large flow events."

The results, Lamb says, offer useful insight into ancient megafloods, both on Earth and on Mars, and the deep canyons they left behind. "We're trying to build models of erosion rates so we can go to places like Mars and make quantitative reconstructions of how much water was there, how long it lasted, and how quickly it moved," Lamb says. In addition, he says, "this is one of a few places where models for canyon formation can be tested because we know the flood conditions under which this canyon formed."

Writer: 
Kathy Svitil
Writer: 

Edwin S. Munger, 88

Noted Caltech geographer was an expert on Africa, ethnic relations

PASADENA, Calif.-Edwin S. Munger, professor of geography, emeritus, at the California Institute of Technology (Caltech), passed away peacefully June 15 at his home in Pasadena, California. He was 88 years old.

Munger was a renowned specialist on Africa, particularly race and ethnic relations. He made dozens of trips to the continent, visited every country on it, and lived there for a decade.

Born in La Grange, Illinois, Munger received his BS, MS, and PhD degrees from the University of Chicago. He was a visiting lecturer at Caltech throughout the 1950s before becoming professor of geography in 1961. He became professor emeritus in 1988.

Munger took his first trip to Africa in 1947-financed by his Army poker winnings-and his second in 1949 as the first Fulbright Fellow to Africa, attending Makerere University, Kampala, Uganda. He was an Institute of Current World Affairs (ICWA) fellow in Africa from 1950 to 1954, and from 1955 to 1961 was an American Universities Field Staff member, during which time he lived a year each in Ghana, Nigeria, Kenya, and South Africa, while at the same time serving on the faculty of the University of Chicago.

He was an evaluator for the Peace Corps in Uganda (1966) and Botswana (1967) and chairman of the U.S. State Department Evaluation Team in South Africa (1971).

Munger once said, "One of the joys of being a geographer is that the world is my oyster, world travel my most stimulating teacher."

His passion for the region led to his founding of the African Studies Association and the U.S.-South African Leader Program, and later, he served as a board member of the South African Institute of Race Relations. For 14 years he served as president of the L.S.B. Leakey Foundation, working to increase scientific knowledge and public understanding of human origins and evolution. He was also instrumental in launching the foundation's Baldwin Fellowships, which have helped more than 40 Africans obtain advanced degrees in archaeology. In 1985, Munger founded the Cape of Good Hope Foundation to help mostly black universities in southern Africa, and subsequently sent more than $3 million dollars worth of books to help those institutions. He edited the Munger Africana Library Notes (1969-1982) and amassed a library of over 60,000 volumes on sub-Saharan Africa, the largest private collection in the United States, and a unique cultural resource.

He was president of the Pasadena Playhouse (1966) and one of the founders of Caltech's Friends of Beckman Auditorium.

A respected teacher, Munger in 1976 received the top teaching prize given by Caltech's student body and in 1980 was made an honorary member of the Caltech Alumni Association. He continued to be a presence on the Caltech campus by joining notable faculty members at the campus faculty club-the Athenaeum-"round table," a lunchtime gathering of scientific leaders from various disciplines who meet to socialize and hold discussions of the highest order.

In 1993 he received the Alumni Citation Award for public service from the University of Chicago, and in 2002 he was the recipient of the Gandhi-King-Ikeda award from Morehouse College for his years of dedication to improving race relations. 

Later in life, he developed an interest in collecting chess sets and at one point had amassed more than 400 ethnic chess sets from the more than 250 countries and islands he had visited.

A prolific author, Munger produced numerous titles, including 1965's Bechuanaland: Pan-African Outpost or Bantu Homeland?, 1967's Afrikaner and African Nationalism, 1983's Touched by Africa, and 1996's Cultures, Chess & Art, A Collector's Odyssey Across Seven Continents, Volume 1: Sub-Saharan Africa, which he followed with volumes 2 and 3.

Munger leaves behind his wife of 40 years, Ann Boyer Munger, daughter Betsy Owens from his first marriage with the late Elizabeth Nelson Munger, nephews Christopher and Roger, and nieces Jennifer, Trudie, and Sarah.

A memorial service will be held at 4:00 p.m. on Thursday, June 24th at the Athenaeum, 551 S. Hill Avenue, Pasadena. In lieu of flowers, the family requests donations in his memory be made to Friends of Beckman Auditorium, Caltech, Pasadena, CA 91125 or to the Institute of Current World Affairs, 4545 42nd St. NW, Suite 311, Washington, D.C. 20016-4623.

Writer: 
Jon Weiner
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