Countdown to Mars: Caltech goes to the Red Planet

On Sunday, August 5, the Mars Science Laboratory (MSL) rover, known as Curiosity, will make its dramatic descent onto Mars's surface. Once it lands, the rover will check its instruments to make sure everything's functioning properly—and then it will get right to work.

In fact, on just the second day of its Martian excursion, Curiosity is scheduled to turn on some of its key scientific instruments, taking pictures and making measurements of its immediate environment. About a week later, the rover will spin its six wheels and start exploring. Curiosity will ramp up its science mission over the following weeks, deploying its suite of instruments to scoop, drill, zap, examine, and analyze. And through it all, a couple of Caltech researchers will be among the 300 scientists working here on Earth, taking the information Curiosity sends home and trying to figure out what it all means.

Back in February, Caltech's Ken Farley and Bethany Ehlmann were named as participating scientists on the mission; each will be directing their own Martian science projects. Ehlmann, an assistant professor of planetary science and a JPL research scientist, has been analyzing rocks and minerals on Earth to help MSL's science team choose which Martian rocks to study in detail. Farley, the W. M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences, will measure the presence of noble gases in Martian rocks to determine their ages. Here are some excerpts from Kimm Fesenmaier's story about how these two scientists intend to make their mark on Mars.

Examining the capabilities of one of Curiosity's science instruments, Sample Analysis at Mars (SAM), which was designed to look for organic matter, Farley realized that it might be possible to detect the isotope helium-3 with SAM's spectrometer. Since helium-3 is produced by the bombardment of surface materials by incoming cosmic rays, measurements of the isotope can be used to determine how long rocks or other geologic features have been exposed on the surface of a planet. This could help scientists date features on Mars such as impact craters, but it could also come in handy in terms of target selection.

Imagine, for example, that the science team locates an impact site on Mars that seems to have been created within the last few million years. The rocks around that site would be ideal targets for closer study because any organic matter they contain would have been protected from cosmic rays until they were thrown out onto the surface. "The trouble is, it's easy to say that an impact happened a million years ago, but how would you ever really know?" Farley says. "The technique that I have is a way to say, 'Yes, this is, in fact, a very young surface.'"

Farley says his involvement with MSL is a major departure from his previous work, as he has not been heavily involved in the study of the geology of Mars. "Most of what I do is technique development," he says. "So it's interesting for me to see potential application of one of those techniques in another very different setting."

In contrast, space missions are Ehlmann's bread and butter. She got her first taste of rover operations while an undergraduate student working on the Mars Exploration Rovers mission. Then as a graduate student, she was a collaborator on the Mars Reconnaissance Orbiter mission and used data from multiple orbiters to locate hydrated minerals on the surface of the red planet.

For MSL, Ehlmann proposed to help improve the team's ability to select rocks from a distance for more extensive study. Curiosity is equipped with a laser and a telescope known collectively as ChemCam, mounted on its mast. From a distance of about seven meters, the laser can zap a rock to create a plasma, which can be analyzed with the ChemCam spectrometer to get a sense of the chemical elements present. The science team needs to be able to use those results and their knowledge of mineralogy to quickly decide whether to spend more time and energy on a particular target or to keep Curiosity moving.

To give them a leg up, Ehlmann is analyzing rocks from places such as Iceland as well as synthetic mixtures of minerals in the lab that are similar to the materials observed from Mars orbit at the Gale Crater landing site. The rocks can be well characterized in Earth laboratories to understand their mineralogy, the elements they are made of, and how they would appear from orbit. She is studying how they have been changed by different types of interaction with water. She plans to take the samples to Los Alamos National Laboratory, which partnered with the French national space agency to build the ChemCam, in order to test her samples with a ChemCam-like instrument.

"It's very helpful to have this beforehand understanding of what you might see or what kinds of analyses you need to run," Ehlmann says. "If you understand the processes enough that you develop quick-look algorithms for detecting different styles of alteration, it will help in the tactical timescale when you only have a few hours to come up with a plan for the rover for the next day."

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Marcus Woo
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An Earthquake in a Maze

Caltech researchers provide highest-resolution observations yet of the complex 2012 Sumatra earthquake

PASADENA, Calif.—The powerful magnitude-8.6 earthquake that shook Sumatra on April 11, 2012, was a seismic standout for many reasons, not the least of which is that it was larger than scientists thought an earthquake of its type—an intraplate strike-slip quake—could ever be. Now, as Caltech researchers report on their findings from the first high-resolution observations of the underwater temblor, they point out that the earthquake was also unusually complex—rupturing along multiple faults that lie at nearly right angles to one another, as though racing through a maze.

The new details provide fresh insights into the possibility of ruptures involving multiple faults occurring elsewhere—something that could be important for earthquake-hazard assessment along California's San Andreas fault, which itself is made up of many different segments and is intersected by a number of other faults at right angles.

"Our results indicate that the earthquake rupture followed an exceptionally tortuous path, breaking multiple segments of a previously unrecognized network of perpendicular faults," says Jean-Paul Ampuero, an assistant professor of seismology at Caltech and one of the authors of the report, which appears online today in Science Express. "This earthquake provided a rare opportunity to investigate the physics of such extreme events and to probe the mechanical properties of Earth's materials deep beneath the oceans."

Most mega-earthquakes occur at the boundaries between tectonic plates, as one plate sinks beneath another. The 2012 Sumatra earthquake is the largest earthquake ever documented that occurred away from such a boundary—a so-called intraplate quake. It is also the largest that has taken place on a strike-slip fault—the type of fault where the land on either side is pushing horizontally past the other.

The earthquake happened far offshore, beneath the Indian Ocean, where there are no geophysical monitoring sensors in place. Therefore, the researchers used ground-motion recordings gathered by networks of sensors in Europe and Japan, and an advanced source-imaging technique developed in Caltech's Seismological Laboratory as well as the Tectonics Observatory to piece together a picture of the earthquake's rupture process. 

Lingsen Meng, the paper's lead author and a graduate student in Ampuero's group, explains that technique by comparing it with how, when standing in a room with your eyes closed, you can often still sense when someone speaking is walking across the room. "That's because your ears measure the delays between arriving sounds," Meng says. "Our technique uses a similar idea. We measure the delays between different seismic sensors that are recording the seismic movements at set locations." Researchers can then use that information to determine the location of a rupture at different times during an earthquake. Recent developments of the method are akin to tracking multiple moving speakers in a cocktail party.

Using this technique, the researchers determined that the three-minute-long Sumatra earthquake involved at least three different fault planes, with a rupture propagating in both directions, jumping to a perpendicular fault plane, and then branching to another.

"Based on our previous understanding, you wouldn't predict that the rupture would take these bends, which were almost right angles," says Victor Tsai, an assistant professor of geophysics at Caltech and a coauthor on the new paper. 

The team also determined that the rupture reached unusual depths for this type of earthquake—diving as deep as 60 kilometers in places and delving beneath the Earth's crust into the upper mantle. This is surprising given that, at such depths, pressure and temperature increase, making the rock more ductile and less apt to fail. It has therefore been thought that if a stress were applied to such rocks, they would not react as abruptly as more brittle materials in the crust would. However, given the maze-like rupture pattern of the earthquake, the researchers believe another mechanism might be in play.

"One possible explanation for the complicated rupture is there might have been reduced friction as a result of interactions between water and the deep oceanic rocks," says Tsai. "And," he says, "if there wasn't much friction on these faults, then it's possible that they would slip this way under certain stress conditions."

Adding to the list of the quake's surprising qualities, the researchers pinpointed the rupture to a region of the seafloor where seismologists had previously considered such large earthquakes unlikely based on the geometry of identified faults. When they compared the location they had determined using source-imaging with high-resolution sonar data of the topography of the seafloor, the team found that the earthquake did not involve what they call "the usual suspect faults."

"This part of the oceanic plate has fracture zones and other structures inherited from when the seafloor formed here, over 50 million years ago," says Joann Stock, professor of geology at Caltech and another coauthor on the paper. "However, surprisingly, this earthquake just ruptured across these features, as if the older structure didn't matter at all."

Meng emphasizes that it is important to learn such details from previous earthquakes in order to improve earthquake-hazard assessment. After all, he says, "If other earthquake ruptures are able to go this deep or to connect as many fault segments as this earthquake did, they might also be very large and cause significant damage."

Along with Meng, Ampuero, Tsai, and Stock, additional Caltech coauthors on the paper, "An earthquake in a maze: compressional rupture branching during the April 11 2012 M8.6 Sumatra earthquake," are postdoctoral scholar Zacharie Duputel and graduate student Yingdi Luo. The work was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, and the Southern California Earthquake Center, which is funded by the National Science Foundation and the United States Geological Survey.

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Kimm Fesenmaier
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Geological Society of America Awards Eiler

John Eiler, Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, has been awarded the 2012 Arthur L. Day Medal by the Geological Society of America (GSA).

Arthur Louis Day established the award in 1948 for "outstanding distinction in contributing to geologic knowledge through the application of physics and chemistry to the solution of geologic problems."

Eiler will receive the medal at the GSA's annual meeting, which will be held November 4–9 in Charlotte, North Carolina.

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Allison Benter
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Caltech Scientists Find New Primitive Mineral in Meteorite

PASADENA, Calif.—In 1969, an exploding fireball tore through the sky over Mexico, scattering thousands of pieces of meteorite across the state of Chihuahua. More than 40 years later, the Allende meteorite is still serving the scientific community as a rich source of information about the early stages of our solar system's evolution. Recently, scientists from the California Institute of Technology (Caltech) discovered a new mineral embedded in the space rock—one they believe to be among the oldest minerals formed in the solar system.

Dubbed panguite, the new titanium oxide is named after Pan Gu, the giant from ancient Chinese mythology who established the world by separating yin from yang to create the earth and the sky. The mineral and the mineral name have been approved by the International Mineralogical Association's Commission on New Minerals, Nomenclature and Classification. A paper outlining the discovery and the properties of this new mineral will be published in the July issue of the journal American Mineralogist, and is available online now.

"Panguite is an especially exciting discovery since it is not only a new mineral, but also a material previously unknown to science," says Chi Ma, a senior scientist and director of the Geological and Planetary Sciences division's Analytical Facility at Caltech and corresponding author on the paper.

The Allende meteorite is the largest carbonaceous chondrite—a diverse class of primitive meteorites—ever found on our planet and is considered by many the best-studied meteorite in history. As a result of an ongoing nanomineralogy investigation of primitive meteorites—which Ma has been leading since 2007—nine new minerals, including panguite, have been found in the Allende meteorite. Some of those new finds include the minerals allendeite, hexamolybdenum, tistarite, and kangite. Nanomineralogy looks at tiny particles of minerals and the minuscule features within those minerals.

"The intensive studies of objects in this meteorite have had a tremendous influence on current thinking about processes, timing, and chemistry in the primitive solar nebula and small planetary bodies," says coauthor George Rossman, the Eleanor and John R. McMillan Professor of Mineralogy at Caltech.

Panguite was observed first under a scanning electron microscope in an ultra-refractory inclusion embedded in the meteorite. Refractory inclusions are among the first solid objects formed in our solar system, dating back to before the formation of Earth and the other planets. "Refractory" refers to the fact that these inclusions contain minerals that are stable at high temperatures and in extreme environments, which attests to their likely formation as primitive, high-temperature liquids produced by the solar nebula.

According to Ma, studies of panguite and other newly discovered refractory minerals are continuing in an effort to learn more about the conditions under which they formed and subsequently evolved. "Such investigations are essential to understand the origins of our solar system," he says.

Additional authors on the American Mineralogist paper, "Panguite, (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD," are John R. Beckett, senior research scientist at Caltech; Oliver Tschauner from the University of Nevada–Las Vegas; and Wenjun Liu from the Argonne National Laboratory. The study was supported through grants from the National Science Foundation, the U.S. Department of Energy, and NASA's Office of Space Science.  

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Katie Neith
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Notes from the Back Row: "The Isotope Time Machine"

Were dinosaurs slow and stupid, as used to be the prevailing wisdom, or nimble and smart enough to eat an attorney, as in the 1993 film Jurassic Park? The answer depends largely on whether the T. Rex in question is cold blooded, like an alligator—although gators, in a shocking lack of professional courtesy, are fully capable of chowing down on counsel—or warm blooded, like a bird. This is because creatures capable of maintaining a constant body temperature, regardless of their environment, generally also have the energy to move fast and think quickly. There's only one sure way to settle the debate, but taking the temperature of an animal that's been extinct for 150 million years poses certain obvious problems.

Fortunately, John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry, has mastered the art of time travel without leaving the lab. His time machine is a mass spectrometer, a device that separates atoms of different weights in a process he likens to the workings of "a good, old-fashioned television set from the days when TV sets were the size of smart cars." Atoms of a given element that have different weights are called isotopes, and in his Watson Lecture on February 29, 2012, Eiler shows how isotope analysis can not only take a dinosaur's temperature, but perhaps tell us why they died. It's CSI: Jurassic Park.

"The Isotope Time Machine" is available for download in HD from Caltech on iTunesU. (Episode 9)

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Doug Smith
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Caltech Astronomer Mike Brown Awarded Kavli Prize in Astrophysics

PASADENA, Calif.—Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy at the California Institute of Technology (Caltech), has been named a co-winner of the 2012 Kavli Prize in Astrophysics for his efforts to understand the outer solar system—work that led to the demotion of Pluto.

Brown shares the award with David Jewitt (MS '80, PhD '83) of UCLA and Jane Luu of MIT's Lincoln Laboratory; in 1992, Jewitt and Luu discovered the first object in the Kuiper belt, a collection of more than a thousand objects beyond the orbit of Neptune. Brown, who joined Caltech's faculty in 1997, has since become a leader in the search for planet-sized objects in the Kuiper belt. According to the prize citation, the three received the prize "for discovering and characterizing the Kuiper belt and its largest members, work that led to a major advance in the understanding of the history of our planetary system."

Brown's most well-known discovery came in 2005, when he found a Kuiper-belt object, later named Eris, that is about the same size as Pluto but 27 percent more massive. That finding caused astronomers to rethink the definition of a planet, resulting in the reclassification of Pluto as a dwarf planet.

"Mike spent years acquiring a massive number of images and learning how to process them to accurately detect objects that subtly shift in the sky over successive days—without knowing whether there was anything interesting to be discovered," explains Kenneth Farley, the W.M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences. "But that dedication was rewarded by the discovery of several fascinating Kuiper-belt objects, and just as important as their discovery was Mike's effort in understanding them—where they came from, how they formed, what they are made of, and what they tell us about our solar system. It is wonderful to see Mike recognized for these contributions."

"This distinguished prize is further acknowledgment of Mike's extraordinary accomplishments and pioneering research that has literally reshaped our understanding of the solar system," adds Caltech president Jean-Lou Chameau. "He is truly a 'renaissance scientist' who approaches teaching and scientific discovery with passion and charisma. We are proud of Mike and are privileged to have him on the Caltech faculty."

"It's humbling to be included alongside previous Kavli Prize winners, from the people whose incredible designs for telescopes enable all of us to make these discoveries to the very pioneers of astrophysics," says Brown. "And it's an amazing reminder that some of the mysteries of the universe are right here in our own cosmic backyard."

The Kavli Prize, which includes a scroll, a gold medal, and $1 million, recognizes scientists in astrophysics, nanoscience, and neuroscience, and has been awarded every other year since 2008. King Harald of Norway will present the prizes to the winners at a ceremony in Oslo on September 4. Caltech's Maarten Schmidt, the Francis L. Moseley Professor of Astronomy, Emeritus, won the astrophysics prize in 2008. Past winners who are Caltech alumni include Jerry Nelson (BS '65), Roger Angel (MS '66), and Richard Scheller (PhD '80).

The Kavli Prizes were initiated by and named after Fred Kavli, founder and chairman of the Kavli Foundation, which is dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research, and supporting scientists and their work.

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Marcus Woo
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Caltech Researchers Gain Greater Insight into Earthquake Cycles

New dynamic computer model first to show full history of a fault segment

PASADENA, Calif.—For those who study earthquakes, one major challenge has been trying to understand all the physics of a fault—both during an earthquake and at times of "rest"—in order to know more about how a particular region may behave in the future. Now, researchers at the California Institute of Technology (Caltech) have developed the first computer model of an earthquake-producing fault segment that reproduces, in a single physical framework, the available observations of both the fault's seismic (fast) and aseismic (slow) behavior. 

"Our study describes a methodology to assimilate geologic, seismologic, and geodetic data surrounding a seismic fault to form a physical model of the cycle of earthquakes that has predictive power," says Sylvain Barbot, a postdoctoral scholar in geology at Caltech and lead author of the study.

A paper describing their model—the result of a Caltech Tectonics Observatory (TO) collaborative study by geologists and geophysicists from the Institute's Division of Geological and Planetary Sciences and engineers from the Division of Engineering and Applied Science—appears in the May 11 edition of the journal Science.

"Previous research has mostly either concentrated on the dynamic rupture that produces ground shaking or on the long periods between earthquakes, which are characterized by slow tectonic loading and associated slow motions—but not on both at the same time," explains study coauthor Nadia Lapusta, professor of mechanical engineering and geophysics at Caltech. Her research group developed the numerical methods used in making the new model. "In our study, we model the entire history of an earthquake-producing fault and the interaction between the fast and slow deformation phases."

Using previous observations and laboratory findings, the team—which also included coauthor Jean-Philippe Avouac, director of the TO—modeled an active region of the San Andreas Fault called the Parkfield segment. Located in central California, Parkfield produces magnitude-6 earthquakes every 20 years on average. They successfully created a series of earthquakes (ranging from magnitude 2 to 6) within the computer model, producing fault slip before, during, and after the earthquakes that closely matched the behavior observed in the past fifty years. 

"Our model explains some aspects of the seismic cycle at Parkfield that had eluded us, such as what causes changes in the amount of time between significant earthquakes and the jump in location where earthquakes nucleate, or begin," says Barbot.

The paper also demonstrates that a physical model of fault-slip evolution, based on laboratory experiments that measure how rock materials deform in the fault core, can explain many aspects of the earthquake cycle—and does so on a range of time scales. "Earthquake science is on the verge of building models that are based on the actual response of the rock materials as measured in the lab—models that can be tailored to reproduce a broad range of available observations for a given region," says Lapusta. "This implies we are getting closer to understanding the physical laws that govern how earthquakes nucleate, propagate, and arrest."

She says that they may be able to use models much like the one described in the Science paper to forecast the range of potential earthquakes on a fault segment, which could be used to further assess seismic hazard and improve building designs. 

Avouac agrees. "Currently, seismic hazard studies rely on what is known about past earthquakes," he says. "However, the relatively short recorded history may not be representative of all possibilities, especially rare extreme events. This gap can be filled with physical models that can be continuously improved as we learn more about earthquakes and laws that govern them."

"As computational resources and methods improve, dynamic simulations of even more realistic earthquake scenarios, with full account for dynamic interactions among faults, will be possible," adds Barbot. 

The Science study, "Under the Hood of the Earthquake Machine; Toward Predictive Modeling of the Seismic Cycle," was funded by grants from the Gordon and Betty Moore Foundation, the National Science Foundation, and the Southern California Earthquake Center.

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Katie Neith
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Technology Developed at the Institute Measures Martian Sand Movement

Dune migration rates appear to be similar to those on Earth

PASADENA, Calif.—Last year, images from NASA's Mars Reconnaissance Orbiter captured sand dunes and ripples moving across the surface of Mars—observations that challenged previously held beliefs that there was not a lot of movement on the red planet's surface. Now, technology developed by a team at the California Institute of Technology (Caltech) has allowed scientists to measure these activities for the very first time.

The new method for data processing is outlined in an advance online publication of the journal Nature.

"For many years, researchers have debated whether or not the sand dunes we see on Mars are fossil features related to past climate, since it was believed that the current atmosphere is too thin to produce winds that could move sand," says Jean-Philippe Avouac, the Earle C. Anthony professor of geology at Caltech, who initiated the study. "Our new data shows that wind activity is indeed a major agent of evolution of the landscape on Mars. This is important because it tells us something about the current state of Mars and how the planet is working today, geologically."

Using the COSI-corr software (for Co-registration of Optically Sensed Images and Correlation), which was invented at Caltech, a team of researchers gathered high-resolution imagery from Mars to look at a specific field of sand dunes called Nili Patera. The images came from the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter.

The team focused on precise, subpixel measurements of movement between pairs of images. On the dunes at Nili Patera, the software automatically measured changes in the position of sand ripples from one image to another over a 105-day period, resulting in the surprising findings that the ripples are moving fast—some upwards of 4.5 meters during that time—which contributes to the total motion of the sand dunes.

"This is the first time that we have full, quantitative measurement of an entire dune field on a planetary surface, as opposed to the localized manual measurements that were done before," explains Francois Ayoub, a coauthor of the paper and a scientist engineer in Avouac's lab. "Using this technique, you could monitor other dune fields, or you could also follow a particular area over a longer time frame to see the seasonal or annual evolution of the sand dunes. This is a huge step in terms of the data that you can obtain from the surface of Mars."

The team also found that the dunes at Nili Patera appear to move similarly to those found on Earth in Victoria Valley, Antarctica. This implies that the rates of landscape modification due to wind are similar on the two planets. Interestingly enough, getting these measurements was much easier on Mars—the researchers could not quantify dune ripple migration rates on Earth using the same technique because that would require satellite imagery of our planet at a resolution that makes it classified information.

"These new measurements provide keys to interpreting the landscape and the stratigraphic record that you see exhumed when you look at the imagery—we see sediments and wonder what they mean in terms of the past geologic history," says Avouac. "The fact that you can describe the current activity of surface systems will help us understand Mars's past geological record, which is a reason that this is important."

Next, the team will focus on learning more about how the sand is actually moving on the surface of Mars.

"We would like to use this new data to tie our observations to the physics of sand transport, which are not well understood," says Sebastien Leprince, a coauthor of the study and a senior research scientist on Avouac's team. "By learning more about how the sand moves around, we may also learn more about the atmosphere on Mars."

The group also plans to use the HiRISE images paired with COSI-Corr to explore other regions of Mars and monitor for surface motion. For example, there are parts of the planet that may have glaciers covered with dust, and other places where fault lines can be seen and could be tracked for displacement.

"We are going to visit other areas on Mars to get a better view of what kind of activity there is on the planet today—geologically speaking, of course," says Avouac, who points out that while they are not looking for life on Mars, their technique is detailed enough that it would detect very small changes on the surface.

The Nature study, "Earth-like Sand Fluxes on Mars," was funded by grants from the Keck Institute for Space Studies at Caltech, NASA's Mars Data Analysis Program, and the Jet Propulsion Laboratory's Director's Research and Development Fund. Additional authors on the study are Antoine Lucas, a postdoctoral scholar in planetary science at Caltech, Nathan T. Bridges from Johns Hopkins University, and Sarah Mattson from the University of Arizona. An exclusive license to Caltech's COSI-Corr technology was recently awarded to Imagin'Labs Corporation (www.imaginlabs.com).

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Katie Neith
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Caltech's Kanamori Named Foreign Associate of National Academy of Sciences

PASADENA, Calif.—Hiroo Kanamori, the John E. and Hazel S. Smits Professor of Geophysics, Emeritus, at the California Institute of Technology (Caltech), has been elected one of 21 new foreign associates of the National Academy of Sciences. Eighty-four new members were also announced during the 149th annual meeting of the academy in Washington, D.C. 

Foreign associates are nonvoting members of the academy who have citizenship outside the United States. Membership in the National Academy of Sciences is considered one of the most important distinctions that a scientist can achieve.

Kanamori is a leading authority on the physics of earthquakes and is known for developing a moment-magnitude scale for determining the magnitude of large earthquakes based on the amount of energy they release. He is particularly interested in the application of seismology to hazard mitigation as well as the study of tsunamis and the implementation of early-warning systems.

Kanamori earned his undergraduate and graduate degrees at the University of Tokyo (BS '59, MS '61, PhD '64) before coming to Caltech as a postdoctoral researcher in 1965. After stints at MIT and the University of Tokyo, he returned to Caltech as a full professor in 1972 and became the Smits Professor of Geophysics in 1989. He served as the director of Caltech's Seismological Laboratory from 1990 until 1998 and became the Smits Professor of Geophysics, Emeritus, in 2005.

Among other distinctions, Kanamori was made a member of the American Academy of Arts and Sciences in 1987, was given the Walter H. Bucher Medal by the American Geophysical Union in 1996, was honored by the Japanese government with the Cultural Merit Award in 2006, and was selected for the Kyoto Prize by the Inamori Foundation in 2007.

Kanamori's election brings the total number of living Caltech faculty members who belong to the National Academy of Sciences to 71. Four of those, including Kanamori, are foreign associates. In addition, three current members of the Caltech Board of Trustees are academy members.

The National Academy of Sciences is dedicated to the "furtherance of science and technology and to their use for the public good," according to its mission statement. Established by a 1863 act of Congress that was signed by President Lincoln, the academy provides scientific advice to the government "whenever called upon" by any government department.

There are now 2,152 active members and 430 foreign associates of the National Academy of Sciences. 

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Kimm Fesenmaier
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Caltech Researchers Use Stalagmites to Study Past Climate Change

PASADENA, Calif.—There is an old trick for remembering the difference between stalactites and stalagmites in a cave: Stalactites hold tight to the ceiling while stalagmites might one day grow to reach the ceiling. Now, it seems, stalagmites might also fill a hole in our understanding of Earth's climate system and how that system is likely to respond to the rapid increase in atmospheric carbon dioxide since preindustrial times.

Many existing historical climate records are biased to the high latitudes— coming from polar ice cores and North Atlantic deep ocean sediments. Yet a main driver of climate variability today is El Niño, which is a completely tropical phenomenon. All of this begs the question: How do we study such tropical climate influences? The answer: stalagmites.

"Stalagmites are the ice cores of the tropics," says Jess Adkins, professor of geochemistry and global environmental science at the California Institute of Technology (Caltech). He and geochemist Kim Cobb of the Georgia Institute of Technology led a team that collected samples from stalagmites in caves in northern Borneo and measured their levels of oxygen isotopes to reconstruct a history of the tropical West Pacific's climate over four glacial cycles during the late Pleistocene era (from 570,000 to 210,000 years ago).

The results appear in the May 3 issue of Science Express. The lead author of the paper, Nele Meckler, completed most of the work as a postdoctoral scholar at Caltech and is now at the Geological Institute of ETH Zürich.

Throughout Earth's history, global climate has shifted between periods of glacial cooling that led to ice ages, and interglacial periods of relative warmth, such as the present. Past studies from high latitudes have indicated that about 430,000 years ago—at a point known as the Mid-Brunhes Event (MBE)—peak temperatures and levels of atmospheric carbon dioxide in interglacial cycles were suddenly bumped up by about a third. But no one has known whether this was also the case closer to the equator.

 

By studying the records from tropical stalagmites, Adkins and his team found no evidence of such a bump. Instead, precipitation levels remained the same across the glacial cycles, indicating that the tropics did not experience a major shift in peak interglacial conditions following the MBE. "The stalagmite records have glacial cycles in them, but the warm times—the interglacials—don't change in the same way as they do at high latitudes," Adkins says. "We don't know what that tells us yet, but this is the first time the difference has been recorded."

At the same time, some changes did appear in the climate records from both the high latitudes and the tropics. The researchers found that extreme drying in the tropics coincided with abrupt climate changes in the North Atlantic, at the tail end of glacial periods. It is thought that these rapid climate changes, known as Heinrich events, are triggered by large ice sheets suddenly plunging into the ocean.

"In the tropics, we see these events as very sharp periods of drying in the stalagmite record," Adkins says. "We think that these droughts indicate that the tropics experienced a more El Niño–like climate at those times, causing them to dry out." During El Niño events, warm waters from the tropics, near Borneo, shift toward the center of the Pacific Ocean, often delivering heavier rainfall than usual to the western United States while leaving Indonesia and its neighbors extremely dry and prone to forest fires. 

The fact that the tropics responded to Heinrich events, but not to the shift that affected the high latitudes following the MBE, suggests that the climate system has two modes of responding to significant changes. "It makes you wonder if maybe the climate system cares about what sort of hammer you hit it with," Adkins says. "If you nudge the system consistently over long timescales, the tropics seem to be able to continue independently of the high latitudes. But if you suddenly whack the climate system with a big hammer, the impact spreads out and shows up in the tropics."

This work raises questions about the future in light of recent increases in atmospheric carbon dioxide: Is this increase more like a constant push? Or is it a whack with a big hammer? A case could be made for either one of these scenarios, says Adkins, but he adds that it would be easiest to argue that the forcing is more like a sudden whack, since the amount of carbon dioxide in the atmosphere has increased at such an unprecedented rate.

In addition to Adkins, Cobb, and Meckler, other coauthors on the paper, "Interglacial hydroclimate in the tropical West Pacific through the late Pleistocene," are Matthew Clarkson of the University of Edinburgh and Harald Sodemann of ETH Zürich. Cobb is also a former postdoctoral scholar in Adkins's group and has been collaborating on this project since her time at Caltech. The work was supported by the National Science Foundation, the Swiss National Science Foundation, the German Research Foundation, and by an Edinburgh University Principal's Career Development PhD Scholarship.

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Kimm Fesenmaier
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