Caltech Professors Awarded 2015 Sloan Fellowships

Five Caltech faculty members have been named among the 2015 class of Sloan Research Fellows. The fellowships, awarded by the Alfred P. Sloan Foundation, honor "early-career scientists whose achievements and potential identify them as rising stars, the next generation of scientific leaders." This year, 126 young scientists were awarded fellowships in eight scientific and technical fields: chemistry, computer science, economics, mathematics, computational and evolutionary biology, neuroscience, ocean sciences, and physics. Candidates must be nominated by a department head or other senior researcher and are reviewed by a selection committee of three distinguished scientists in each field.

Viviana Gradinaru (BS' 05), an assistant professor of biology and the faculty director of the Beckman Institute Pilot Center for Optogenetics and CLARITY, received her fellowship in the area of neuroscience. The CLARITY technique, codeveloped by Gradinaru, is used to render tissues, organs, and even whole organisms transparent. Her research focuses on developing tools and methods for neuroscience as well as investigating the mechanisms underlying deep brain stimulation and its long-term effects on neuronal health, function, and behavior.

Mitchell Guttman, an assistant professor of biology, received the fellowship in the category of computational and evolutionary molecular biology. His work exploring unknown regions of the genome has led to the identification of genes that do not produce proteins, known as long noncoding RNAs (lncRNAs), which act as efficient administrators, gathering and organizing key proteins necessary for packaging genetic information and regulating gene expression. Guttman and his colleagues recently discovered that lncRNAs can shape chromosome structure to remodel the genome and pull in necessary target genes, unlike other proteins that must travel to their targets.

Gregg Hallinan, an assistant professor of astronomy, received his fellowship in the physics category. His group studies the universe at radio wavelengths, particularly examining the radio emissions produced by stars and their planets. His team recently completed construction of a new radio telescope at Caltech's Owens Valley Radio Observatory that can survey the entire sky instantaneously. This project aims to deliver the first detection of radio waves produced by the interaction of the magnetic field of an exoplanet—a planet outside our own solar system—with the stellar wind of its host star.

Heather Knutson, an assistant professor of planetary science, received the fellowship in the physics category. She studies the structure, chemistry, and atmospheric dynamics of extrasolar planets. These planets are often classified into broad categories based on their mass and radius. Knutson's research measuring exoplanet temperatures and characterizing atmospheric compositions adds detail to these classifications. She has helped develop many of the techniques that are now used to study exoplanet atmospheric dynamics.

Xinwen Zhu, an associate professor of mathematics, received the fellowship in the mathematics category. His research interests focus on geometric representation theory, in particular the geometric aspects of the Langlands program, a kind of "unified theory of mathematics" linking together many different mathematical fields of research. This research aims to provide a more intuitive visualization of prime numbers by relating the field to diverse topics such as geometry and quantum physics.

Also included among this year's class of fellows are six other Caltech alumni: Brandi Cossairt (BS '06), Jennifer A. Dionne (MS '05, PhD '09), Aaron Esser-Kahn (BS '04), Michael Kesden (PhD '05), Neal Mankad (PhD '10), and Stephanie Waterman (MS '02).

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Monday, March 2, 2015
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The Secret Life of a Snowflake

Knutson Receives AAS Award for Outstanding Research

Heather Knutson, assistant professor of planetary science at Caltech, has been awarded the Newton Lacy Pierce Prize of the American Astronomical Society (AAS). The prize, given annually to young astronomers for outstanding achievement in observational astronomical research, was awarded to Knutson for her "transformational work in the characterization of exoplanet atmospheres," according to the award citation.

"I was delighted to hear that I had won the award," she says. "It was a great way to start off the new year."

Knutson studies the structure, chemistry, and atmospheric dynamics of extrasolar planets—those outside our own solar system. In the last two decades, astronomers have identified more than 1,800 exoplanets, which come in a variety of shapes and sizes, and orbit their host stars at different distances. Learning about the atmospheres of these planets is important for determining how the worlds evolved, what kind of weather they experience, the chemistry that is taking place at their surface, and whether any of these planets should be considered potentially habitable.

"It's an exciting time for exoplanets," Knutson says. "We now know that the majority of planetary systems look quite different than our own familiar solar system."

When a planet is discovered, measurements of its mass and radius allow it to be classified into a broad category, such as "hot Jupiters," gas giant planets closely orbiting their stars, or "super-Earths," planets larger than Earth but smaller than Neptune. Knutson has added detail to these general classifications through her measurements of exoplanet temperatures and characterizations of atmospheric compositions.

Knutson has helped develop many of the techniques that are now used to study atmospheric dynamics on these exoplanets. As visiting an exoplanet is out of the question, she draws conclusions by observing the eclipse created when the planet passes in front of its host star, called a transit. By measuring the depth of this eclipse at different wavelengths, astronomers can determine the composition of the planet's atmosphere.

Knutson found that information about a planet and its atmosphere could also be revealed by taking spectra at a seemingly odd point in an exoplanet's orbit: when it is not in front of but behind—and eclipsed by—its star, an event known as a secondary eclipse.

"Secondary eclipses tell us about the atmospheric composition and how the planet's temperature changes with height in the atmosphere," Knutson says. "In theory, we can detect clouds via reflected light during secondary eclipse, but usually we see them first when they scatter or block the starlight passing through the planet's atmosphere during the transit."

Using this technique, Knutson has sampled and analyzed a diverse range of exoplanets including the Neptune-sized GJ 436b. Spectra from the planet were featureless, indicating either a high cloud layer or a dense hydrogen-poor atmosphere of mostly heavy molecules like water vapor, carbon monoxide, and carbon dioxide. Knutson and her team have also constructed the first "map" of temperature distributions across an exoplanet.

Before joining the Caltech faculty in 2011, Knutson earned her PhD from Harvard and was a Miller Fellow at UC Berkeley. In 2012, she was awarded the Annie J. Cannon Award in Astronomy by the AAS. She is one of the founding members of Caltech's Center for Planetary Astronomy.

Knutson will accept the Pierce Prize at the 227th annual meeting of the AAS, which will be held in Kissimmee, Florida, in January 2016.

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Friday, February 13, 2015
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Backpocket Barnburner: A Lightning Quick Overview of Educational Theory

Batygin Named to Forbes's "30 Under 30" List

Among the many descriptors assigned to Caltech scientists, "rock star" is not the most common.

But when Konstantin Batygin (MS '10, PhD '12), an assistant professor of planetary science at Caltech, was recently included in Forbes's "30 Under 30" list in the science category, the editors used just those words, describing Batygin as "the next physics rock star." And indeed, in addition to having already published 21 papers as first author, the 28-year-old planetary scientist is a lead singer in a band called The Seventh Season.

The Forbes list, now in its third year, spotlights 30 "game changers, movers, and makers" under 30 years old, in 20 different categories ranging from venture capital to music.

When he is not playing gigs with his band or flying remote-controlled planes—a favorite pastime he picked up during graduate school—Batygin researches the evolution of planetary orbits, from their chaotic beginnings to the eventual end of their parent solar systems. By studying the dynamical structure of our own planetary system, Batygin and his team are developing a theoretical understanding of the origins and long-term evolution of other such systems throughout the galaxy.

Batygin also studies the interiors of exoplanets. Many of the exoplanets that have been discovered reside in close proximity to their host stars and so are bathed in intense stellar radiation. This can cause their atmospheres to become electrically conductive. Batygin studies how the interaction between an exoplanet's magnetic field and its electrically charged atmosphere can induce electrical currents that heat the planet's interior and perturb atmospheric circulation patterns.

"I am deeply humbled by this recognition," says Batygin. "More than anything, this is a tribute to the outstanding mentorship that I have received over the years from my advisers, particularly during my time here at Caltech as a graduate student."

Batygin is not Caltech's first talented young researcher to be recognized on the "30 Under 30" list. Assistant Professor of Biology Mitchell Guttman has appeared on the list twice, in 2013 and 2014; Assistant Research Professor Elaine Hsiao was named to the list in 2013; and two Caltech alumni and a graduate students also made the list in 2012.

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Saturday, January 24, 2015
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The personal side of science

Wednesday, February 4, 2015
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Meet the Outreach Guys: James & Julius

Grotzinger Steps Down as Curiosity’s Project Scientist

Caltech geologist John Grotzinger, who was recently named chair of the Division of Geological and Planetary Sciences, has stepped down as project scientist for NASA's Mars Rover Curiosity. He is succeeded by Ashwin Vasavada (PhD '98) of JPL.

Grotzinger, the Fletcher Jones Professor of Geology at Caltech, has served as project scientist for Curiosity's mission, the Mars Science Laboratory (MSL), since 2007. Prior to that, he had been actively involved as a member of the science team for both the Mars Exploration rovers and the Mars Reconnaissance Orbiter.

Since Curiosity's suspenseful landing on Mars in August 2012—dubbed the "Seven Minutes of Terror"—its team of scientists has discovered an ancient alluvial fan and lake system that filled in a 3.6 billion year-old impact crater the size of the Los Angeles basin. The science team also determined that the chemistry of this geologic system would have supported microbial chemolithotrophy—the usage of inorganic compounds as a source of energy—if life had ever evolved on Mars.

"I have considered it a privilege to help guide the MSL mission for almost eight years," remarks Grotzinger. "We accomplished the principal goal of the mission—to find an ancient habitable environment—and I will now enjoy spending more time working on the mission data as a science team member."

Grotzinger's successor, Vasavada, had been deputy project scientist for MSL for the last 10 years. He has also worked on the science teams for NASA's Lunar Reconnaissance Orbiter and for the Cassini mission to Saturn. He earned his doctorate in planetary science from Caltech's Division of Geological and Planetary Sciences.

"Ashwin Vasavada is a great choice as the next project scientist," says Grotzinger. "He has a very strong technical background, an intimate understanding of the science instruments and rover flight systems, and brings real passion for the exploration of Mars."

For more about this transition, read JPL's release.

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Wednesday, February 18, 2015
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HALF TIME: A Mid-Quarter Meetup for TAs

Remembering Don L. Anderson


Don L. Anderson, the Eleanor and John R. McMillan Professor of Geophysics, Emeritus, passed away on December 2, 2014. He was 81 years old.

Anderson's work helped advance our understanding of the composition, structure, and dynamics of the earth and of earth-like planets. He was a pioneer in the use of seismic anisotropy—variations in the velocities of seismic waves as they move at different angles through materials—to study the earth's interior. This allowed him and others to learn more about the boundaries of the planet's mantle.

"Caltech has lost a towering figure in geophysics with the passing of Don Anderson," says Michael Gurnis, the John E. and Hazel S. Smits Professor of Geophysics. "Don left an indelible mark not just on the Seismological Laboratory but on the field of global seismology and whole-earth geophysics. He was an unusual scientist who often advocated unpopular theories and concepts. Perhaps more than anyone else, DLA—as he was fondly known in the Seismo Lab—knew how uncertain many of our observations and theories were, especially those of the earth's deep interior. By advocating the unpopular, Don challenged our ideas and forced us to make the observations needed to resolve our understanding of earthquakes and the deep earth."

In 1981, Anderson developed, with Adam Dziewonski of Harvard University, the Preliminary Reference Earth Model (PREM), a one-dimensional model representing the average properties of the earth, including seismic velocities, attenuation, and density, as a function of planetary radius. PREM continues to be the most widely used standard model of the earth. Anderson, a former president (1988–1990) of the American Geophysical Union, is the author of the book, Theory of the Earth, a 1989 reference on the origin, composition, and evolution of Earth's interior. In 2007, Anderson published New Theory of the Earth, a completely updated version.

Born in Frederick, Maryland, on March 5, 1933, the son of a schoolteacher and an electrician, Anderson received his BS in geology and geophysics from Rensselaer Polytechnic University in 1955. He worked for Chevron Oil Company from 1955 to 1956, the Air Force Cambridge Research Center from 1956 to 1958, and the Arctic Institute of North America from 1958 to 1960.

His service with the Air Force took him to Greenland, where his job was to determine how thick the ice had to be to support aircraft that were in trouble. "The Air Force wanted their pilots to land disabled planes on the sea ice, but the conventional wisdom at the time was that they would break through the ice and the crew would freeze to death," Anderson recalled in a 2001 oral history. Anderson and his colleagues found that, in fact, aircraft can land very easily on ice that is not very thick: "Even if the ice won't support the plane while it's sitting there, it will allow a plane to taxi long enough for the pilots to get out and then the plane can sink through the ice, or the wheels can poke through the ice. Our job was to study ice strength, and whether you could determine how strong it was before you landed so you would know where to land." The project continued after Anderson entered graduate school at Caltech, where he earned a master's degree in geophysics in 1959 and a doctorate in geophysics in 1962 under the supervision of Frank Press.

Upon his graduation from Caltech, Anderson was hired as a research fellow; he became an assistant professor in 1963, an associate professor in 1964, and a professor in 1968. From 1967 to 1989, Anderson was director of Caltech's Seismological Laboratory.

"Those who were fortunate enough to be at the Seismo Lab with Don since the 1960s have greatly benefited from the interaction with him, and his influence will have long-lasting effects on our work for years to come," says Hiroo Kanamori, the John E. and Hazel S. Smits Professor of Geophysics, Emeritus. "As many of the Seismo Lab alumni would testify, we all benefited tremendously from the Seismo Lab coffee break discussions where Don was always at the center. Occasionally, he forcefully presented his idea, but more often he was a good listener too. Then, we later received notes and reprints on the subjects discussed, and if we were really interested in the subject, we would pursue it in depth and eventually write an interesting paper. Many of my papers grew out of the coffee break discussions."

"Don was a inspiring geoscientist who motivated his students and many younger colleagues to think deeply, broadly, and creatively about the Earth and other planets," says Thomas Jordan (PhD '72), a former student of Anderson's who is now the William M. Keck Foundation Chair in Geological Sciences and professor of Earth sciences at the University of Southern California.

Provost Edward Stolper, the William E. Leonhard Professor of Geology and the Carl and Shirley Larson Provostial Chair, agreed, saying "Don had a significant impact on my career—both as a supportive, probing, and intellectually challenging colleague, and as a friend.

"As a graduate student at Harvard, I heard Don lecture about the possibility of there being a CAI-like zone around the earth's core and about the composition of the moon. CAI's are calcium-aluminum inclusions in chondritic meteorites and represent the very earliest solid materials formed in the solar system. I was energized by what Don had said and knew at that point I wanted to be at Caltech," says Stolper.

Anderson was the Eleanor and John R. McMillan Professor from 1989 until his retirement in 2002.

"Don had a tremendous influence on the development of geophysics and global seismology in the United States," says Gurnis, the current director of Caltech's Seismological Laboratory. "One of DLA's unwavering passions since the 1960s was to map the earth's deep interior associated with surface processes. He was instrumental in founding the NSF-funded IRIS—Incorporated Research Institutions for Seismology—and the development of what became known as the GSN—the Global Seismic Network—in the 1980s. Through these major U.S. programs, we were able to map out the nature of the forces associated with plate tectonics and volcanism."

Anderson continued to work and publish until his death. His most recent work on volcanism was showcased at the fall meeting of the American Geophysical Union in San Francisco in December 2014.

A fellow of the American Academy of Arts and Sciences and a member of the National Academy of Sciences and the American Philosophical Society, Anderson was also the recipient of the Emil Wiechert Medal of the German Geophysical Society, the Arthur L. Day Medal of the Geological Society of America, the Gold Medal of the Royal Astronomical Society, the William Bowie Medal of the American Geophysical Union, and the Crafoord Prize of the Royal Swedish Academy of Sciences.

In 1998, Anderson was awarded the National Medal of Science and was cited for his "immeasurable influence on the advancement of earth sciences over the past three decades nationally and internationally."

Anderson is survived by his wife, Nancy; daughter, Lynn Rodriguez; son, Lee Anderson; and four granddaughters.

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