Monday, March 31, 2014
Center for Student Services 360 (Workshop Space)

Unleashing Collaborative Learning through Technology: A Study of Tablet-Mediated Student Learning

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Michael Gurnis Receives Geology Award

The American Association of Petroleum Geologists (AAPG) named Michael Gurnis, Caltech's John E. and Hazel S. Smits Professor of Geophysics, a 2014 recipient of the Wallace E. Pratt Memorial Award.

The award honors the authors of the best original article published in the AAPG Bulletin each year. Gurnis shares the $1,500 cash award with coauthor Sonja Spasojevic (MS '07, PhD, '11) for their 2012 article "Sea level and vertical motion of continents from dynamic earth model since the Late Cretaceous." The article was a key part in Spasojevic's 2010 Caltech doctoral thesis.

"I am very grateful to the American Association of Petroleum Geologists for the recognition of our work linking long-term sea level change to the dynamics of plate tectonics and the earth's deep interior," says Gurnis. "I would also like to acknowledge the generous support of Statoil, the Norwegian oil company, which provided the primary support for this work."

Gurnis' research at Caltech centers on local, regional, and global geological and geophysical observations to better understand the processes related to plate tectonics and deep mantle dynamics. His lab develops sophisticated computational models to study geological and geophysical properties. In addition, Gurnis is director of the Seismological Laboratory at Caltech, an internationally recognized center for the study of earthquakes, seismic monitoring, and fundamental science that underpins geophysics and seismology.

The Wallace E. Pratt Memorial Award is named in honor of a founding member and fourth president of the AAPG.

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Detection of Water Vapor in the Atmosphere of a Hot Jupiter

Caltech researchers develop a new technique to find water vapor on extrasolar planets

Although liquid water covers a majority of Earth's surface, scientists are still searching for planets outside of our solar system that contain water. Researchers at Caltech and several other institutions have used a new technique to analyze the gaseous atmospheres of such extrasolar planets and have made the first detection of water in the atmosphere of the Jupiter-mass planet orbiting the nearby star tau Boötis. With further development and more sensitive instruments, this technique could help researchers learn about how many planets with water—like Earth—exist within our galaxy.

The new results are described in the February 24 online version of The Astrophysical Journal Letters.

Scientists have previously detected water vapor on a handful of other planets, but these detections could only take place under very specific circumstances, says graduate student Alexandra Lockwood, the first author of the study. "When a planet transits—or passes in orbit in front of—its host star, we can use information from this event to detect water vapor and other atmospheric compounds," she says. "Alternatively, if the planet is sufficiently far away from its host star, we can also learn about a planet's atmosphere by imaging it."

However, significant portions of the population of extrasolar planets do not fit either of these criteria, and there was not really a way to find information about the atmospheres of these planets. Looking to resolve this problem, Lockwood and her adviser Geoffrey Blake, professor of cosmochemistry and planetary sciences and professor of chemistry, applied a novel technique for finding water in a planetary atmosphere. Other researchers had used similar approaches previously to detect carbon monoxide in tau Boötis b.

The method utilized the radial velocity (RV) technique—a technique commonly used in the visible region of the spectrum to which our eyes are sensitive—for discovering non-transiting exoplanets. Using the Doppler effect, RV detection traditionally determines the motion of a star due to the gravitational pull of a companion planet; the star moves opposite that of the orbital motion of the planet, and the stellar features shift in wavelength. A large planet or a planet closer to its host star provides a larger shift.

Lockwood, Blake, and their colleagues expanded the RV technique into the infrared to determine the orbit of tau Boötis b around its star, and added further analysis of the light shifts via spectroscopy—an analysis of the light's spectrum. Since every compound emits a different wavelength of light, this unique light signature allows the researchers to analyze molecules that make up the planet's atmosphere. Using data of tau Boötis b from the Near Infrared Echelle Spectrograph (NIRSPEC) at the W. M. Keck Observatory in Hawaii, the researchers were able to compare the molecular signature of water to the light spectrum emitted by the planet, confirming that the atmosphere did indeed include water vapor.

"The information we get from the spectrograph is like listening to an orchestra performance; you hear all of the music together, but if you listen carefully, you can pick out a trumpet or a violin or a cello, and you know that those instruments are present," she says. "With the telescope, you see all of the light together, but the spectrograph allows you to pick out different pieces; like this wavelength of light means that there is sodium, or this one means that there's water."

In addition to using the spectrographic technique to study the planet's atmospheric composition, the method also provides a way for researchers to analyze the mass of planets. "They're actually two separate findings, but they're both very exciting," says Lockwood. "When you're doing calculations to look for the atmospheric signature—which tells you that there's water present—you also determine the 3-D motion of the star and the planet in the system. With this information, if you also know the mass of the star, you can determine the mass of the planet," she says.

Previous RV methods for measuring a planet's mass could only determine the planet's indicative mass—an estimation of its minimum mass, which might be much less than its actual mass. This new technique provides a way to measure the true mass of a planet since both light from the star and the planet are detected, which is critical for understanding how planets and planetary systems form and evolve.

Although the technique promises to augment how planetary scientists analyze the properties of extrasolar planets, it has limitations, the researchers say. For example, the technique is presently limited to so-called "hot Jupiter" gas giant planets like tau Boötis b—those that are large and orbit very close to their host star.

"The technique is limited by the light-collecting power and wavelength range of the telescope, and even with the incredible collecting area of the Keck Observatory mirror on the high, dry summit of Mauna Kea we can basically only analyze hot planets that are orbiting bright stars, but that could be expanded in the future as telescopes and infrared spectrographs improve," Lockwood says. In the future, in addition to analyzing cooler planets and dimmer stars, the researchers plan to continue looking for and analyzing the abundance of other molecules that might be present in the atmosphere of tau Boötis b.

"While the current state of the technique cannot detect earthlike planets around stars like the Sun, with Keck it should soon be possible to study the atmospheres of the so-called 'super-Earth' planets being discovered around nearby low-mass stars, many of which do not transit," Blake says. "Future telescopes such as the James Webb Space Telescope and the Thirty Meter Telescope (TMT) will enable us to examine much cooler planets that are more distant from their host stars and where liquid water is more likely to exist."

The findings appear in the The Astrophysical Journal Letters in a paper titled "Near-IR Direct Detection of Water Vapor in tau Boötis b." Other coauthors include collaborators from Pennsylvania State University, the Naval Research Laboratory, the University of Arizona, and the Harvard-Smithsonian Center for Astrophysics. The work was funded by the National Science Foundation Graduate Research Fellowship Program, the David and Lucile Packard and Alfred P. Sloan foundations, and the Penn State Center for Exoplanets and Habitable Worlds.

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Monday, April 7, 2014
Center for Student Services 360 (Workshop Space)

Planning Session for the Fall 2014 Teaching Conference

Wednesday, April 23, 2014
Beckman Institute Auditorium

The Art of Scientific Presentations

Wednesday, April 2, 2014
Beckman Institute Auditorium

Juggling Teaching at a Community College and Research at Caltech

The First 50 Years of Planetary Science

If you ask Andy Ingersoll how Caltech has contributed to our understanding of the universe, he will tell you, "Caltech invented planetary science!" Indeed, the existence of planetary science as a scientific discipline springs largely from the vision of the late Robert P. Sharp (BS'34, MS'35), chair of Caltech's Division of Geological Sciences from 1952 to 1968, who sought a new frontier for geology. And since the field's origins just fifty years ago, Caltech has become one of the top centers of planetary science research in the world.

In the early 1960s, several Caltech faculty members were advocating deep-ocean studies of the sea floor, which would have meant acquiring a deep-ocean research vessel—or partnering with an institution that owned one. Instead, as Sharp explained in a video on the program's history, "We chose to go into space science because the bus, in a sense, was right at our back door." Indeed, NASA's Jet Propulsion Laboratory, which Caltech had founded as a rocket research facility during World War II, had claimed unmanned spaceflight as its turf by putting America's first successful satellite, Explorer 1, into orbit a mere five years earlier. "We had a greater chance for uniqueness by allying with the space program," he continued. Sharp; Bruce Murray, Caltech's first planetary science professor; and Caltech physicist Robert Leighton were key members of the science team for JPL's Mariner 4, the first spacecraft to reach Mars. The 5.2 million bits of data it returned—including 21 pictures of the Martian surface—allowed us to begin comparing Earth and its brethren firsthand. Today, planetary science has grown to encompass the study of solar systems beyond our own.

At a symposium held on Thursday, February 6, to celebrate planetary science at Caltech, a panel of speakers exemplified this expansion while illustrating the Institute's continued diversity of approaches to the field. Planetary scientists John Grotzinger and Bethany Ehlmann gave the latest updates from the rover-based exploration of Mars. Planetary scientist David Stevenson talked about the gas giants of the outer solar system, all of which have been visited by at least one JPL spacecraft. Planetary astronomer Mike Brown, who got Pluto demoted to a minor planet, spoke of the hordes of objects at the outer limits of the solar system that he expects to discover in April using a Japanese telescope on the summit of Hawaii's Mauna Kea. Physics professor Ed Stone, the project scientist for JPL's Voyager mission, described the journey of the twin spacecraft into interstellar space; while astronomer Gregg Hallinan and planetary scientist Heather Knutson outlined different approaches to finding habitable worlds circling nearby suns.

Says Stevenson, "Bob Sharp was always interested in doing something different, something new. We're now roaming Mars, finding new worlds in the outer solar system and starting to understand planets around other stars. He would be delighted with how it turned out."

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Friday, March 14, 2014
Avery Dining Hall

Workshop: Comedy as a Teaching Tool

Is Natural Gas a Solution to Mitigating Climate Change?

Methane, a key greenhouse gas, has more than doubled in volume in Earth's atmosphere since 1750. Its increase is believed to be a leading contributor to climate change. But where is the methane coming from? Research by atmospheric chemist Paul Wennberg of the California Institute of Technology (Caltech) suggests that losses of natural gas—our "cleanest" fossil fuel—into the atmosphere may be a larger source than previously recognized.

Radiation from the sun warms Earth's surface, which then radiates heat back into the atmosphere. Greenhouse gases trap some of this heat. It is this process that makes life on Earth possible for beings such as ourselves, who could not tolerate the lower temperatures Earth would have if not for its "blanket" of greenhouse gases. However, as Goldilocks would tell you, there is "too hot" as well as "too cold," and the precipitous increase in greenhouse gases since the beginning of the Industrial Revolution induces climate change, alters weather patterns, and has increased sea level. Carbon dioxide is the most prevalent greenhouse gas in Earth's atmosphere, but there are others as well, among them methane.

Those who are concerned about greenhouse gases have a very special enemy to fear in atmospheric methane. Methane has a trifecta of effects on the atmosphere. First, like other greenhouse gases, methane works directly to trap Earth's radiation in the atmosphere. Second, when methane oxidizes in Earth's atmosphere, it is broken into components that are also greenhouse gases: carbon dioxide and ozone. Third, the breakdown of methane in the atmosphere produces water vapor, which also functions as a greenhouse gas. Increased humidity, especially in the otherwise arid stratosphere where approximately 10 percent of methane is oxidized, further increases greenhouse-gas induced climate change.

Fully one-third of the increase in radiative forcing (the ability of the atmosphere to retain radiation from the sun) since 1750 is estimated to be due to the presence and effects of methane. Because of the many potential sources of atmospheric methane, from landfills to wetlands to petroleum processing, it can be difficult to quantify which sources are making the greatest contribution. But according to Paul Wennberg, Caltech's R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering, and his colleagues, it is possible that a significant source of methane, at least in the Los Angeles basin, is fugitive emissions—leaks—from the natural-gas supply line.

"This was a surprise," Wennberg explains of the results of his research on methane in the Los Angeles atmosphere. In an initial study conducted in 2008, Wennberg's team analyzed measurements from the troposphere, the lowest portion of Earth's atmosphere, via an airplane flying less than a mile above the ground over the Los Angeles basin.

In analyzing chemical signatures of the preliminary samples, Wennberg's team made an intriguing discovery: the signatures bore a striking similarity to the chemical profile of natural gas. Normally, the methane from fossil fuel sources is accompanied by ethane gas—which is the second most common component of natural gas—while biogenic sources of methane (such as livestock and wastewater) are not. Indeed, the researchers found that the ratio of methane and ethane in the L.A. air samples was characteristic of the samples of natural gas provided by the Southern California Gas Company, which is the leading supplier of natural gas to the region.

Wennberg hesitates to pinpoint natural-gas leaks as the sole source of the L.A. methane, however. "Even though it looks like the methane/ethane could come from fugitive natural-gas emissions, it's certainly not all coming from this source," he says. "We're still drilling for oil in L.A., and that yields natural gas that includes ethane too."

The Southern California Gas Company reports very low losses in the delivery of natural gas (approximately 0.1 percent), and yet atmospheric data suggest that the source of methane from either the natural-gas infrastructure or petroleum production is closer to 2 percent of the total gas delivered to the basin. One possible way to reconcile these vastly different estimates is that significant losses of natural gas may occur after consumer metering in the homes, offices, and industrial plants that purchase natural gas. This loss of fuel is small enough to have no immediate negative impact on household users, but cumulatively it could be a major player in the concentration of methane in the atmosphere.

The findings of Wennberg and his colleagues have led to a more comprehensive study of greenhouse gases in urban settings, the Megacities Carbon Project, based at JPL. The goal of the project, which is focusing initially on ground-based measurements in Los Angeles and Paris, is to quantify greenhouse gases in the megacities of the world. Such cities—places like Hong Kong, Berlin, Jakarta, Johannesburg, Seoul, São Paulo, and Tokyo—are responsible for up to 75 percent of global carbon emissions, despite representing only 3 percent of the world's landmass. Documenting the types and sources of greenhouse gases in megacities will provide valuable baseline measurements that can be used in efforts to reduce greenhouse gas emissions.

If the findings of the Megacities Carbon Project are consistent with Wennberg's study of methane in Los Angeles, natural gas may be less of a panacea in the search for a "green" fuel. Natural gas has a cleaner emissions profile and a higher efficiency than coal (that is, it produces more power per molecule of carbon dioxide), but, as far as climate change goes, methods of extraction and distribution are key. "You have to dig it up, put it in the pipe, and burn it without losing more than a few percent," Wennberg says. "Otherwise, it's not nearly as helpful as you would think."

Wennberg's research was published in an article titled "On the Sources of Methane to the Los Angeles Atmosphere" in Environmental Science & Technology. Data for this study were provided by the Southern California Gas Company, NASA, NOAA, and the California Air Resources Board. The research was funded by NASA, the California Energy Commission's Public Interest Environmental Research program, the California Air Resources Board, and the U.S. Department of Energy.

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Cynthia Eller
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Caltech's "Secrets" to Success

Everyone who really knows Caltech understands that it is unique among universities around the world. But just what makes Caltech so special? We've asked that question before, and the numbers don't tell the full story. So, is it our focus? Our culture? Our people?

The UK's Times Higher Education magazine recently tackled the topic, asking more specifically, "How does a tiny institution create such an outsized impact?" Caltech faculty share their perspectives in the cover story of the magazine's latest issue.

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