Tuesday, October 7, 2014
Center for Student Services 360 (Workshop Space) – Center for Student Services

Thirty Meter Telescope Groundbreaking and Blessing

Tuesday, October 7, 2014
Center for Student Services 360 (Workshop Space) – Center for Student Services

Caltech Peer Tutor Training

Wednesday, September 24, 2014

A chance to meet Pasadena Unified School District Leadership

Textbook Theory Behind Volcanoes May Be Wrong

In the typical textbook picture, volcanoes, such as those that are forming the Hawaiian islands, erupt when magma gushes out as narrow jets from deep inside Earth. But that picture is wrong, according to a new study from researchers at Caltech and the University of Miami in Florida.

New seismology data are now confirming that such narrow jets don't actually exist, says Don Anderson, the Eleanor and John R. McMillian Professor of Geophysics, Emeritus, at Caltech. In fact, he adds, basic physics doesn't support the presence of these jets, called mantle plumes, and the new results corroborate those fundamental ideas.

"Mantle plumes have never had a sound physical or logical basis," Anderson says. "They are akin to Rudyard Kipling's 'Just So Stories' about how giraffes got their long necks."

Anderson and James Natland, a professor emeritus of marine geology and geophysics at the University of Miami, describe their analysis online in the September 8 issue of the Proceedings of the National Academy of Sciences.

According to current mantle-plume theory, Anderson explains, heat from Earth's core somehow generates narrow jets of hot magma that gush through the mantle and to the surface. The jets act as pipes that transfer heat from the core, and how exactly they're created isn't clear, he says. But they have been assumed to exist, originating near where the Earth's core meets the mantle, almost 3,000 kilometers underground—nearly halfway to the planet's center. The jets are theorized to be no more than about 300 kilometers wide, and when they reach the surface, they produce hot spots.  

While the top of the mantle is a sort of fluid sludge, the uppermost layer is rigid rock, broken up into plates that float on the magma-bearing layers. Magma from the mantle beneath the plates bursts through the plate to create volcanoes. As the plates drift across the hot spots, a chain of volcanoes forms—such as the island chains of Hawaii and Samoa.

"Much of solid-Earth science for the past 20 years—and large amounts of money—have been spent looking for elusive narrow mantle plumes that wind their way upward through the mantle," Anderson says.

To look for the hypothetical plumes, researchers analyze global seismic activity. Everything from big quakes to tiny tremors sends seismic waves echoing through Earth's interior. The type of material that the waves pass through influences the properties of those waves, such as their speeds. By measuring those waves using hundreds of seismic stations installed on the surface, near places such as Hawaii, Iceland, and Yellowstone National Park, researchers can deduce whether there are narrow mantle plumes or whether volcanoes are simply created from magma that's absorbed in the sponge-like shallower mantle.

No one has been able to detect the predicted narrow plumes, although the evidence has not been conclusive. The jets could have simply been too thin to be seen, Anderson says. Very broad features beneath the surface have been interpreted as plumes or super-plumes, but, still, they're far too wide to be considered narrow jets.

But now, thanks in part to more seismic stations spaced closer together and improved theory, analysis of the planet's seismology is good enough to confirm that there are no narrow mantle plumes, Anderson and Natland say. Instead, data reveal that there are large, slow, upward-moving chunks of mantle a thousand kilometers wide.

In the mantle-plume theory, Anderson explains, the heat that is transferred upward via jets is balanced by the slower downward motion of cooled, broad, uniform chunks of mantle. The behavior is similar to that of a lava lamp, in which blobs of wax are heated from below and then rise before cooling and falling. But a fundamental problem with this picture is that lava lamps require electricity, he says, and that is an outside energy source that an isolated planet like Earth does not have.  

The new measurements suggest that what is really happening is just the opposite: Instead of narrow jets, there are broad upwellings, which are balanced by narrow channels of sinking material called slabs. What is driving this motion is not heat from the core, but cooling at Earth's surface. In fact, Anderson says, the behavior is the regular mantle convection first proposed more than a century ago by Lord Kelvin. When material in the planet's crust cools, it sinks, displacing material deeper in the mantle and forcing it upward.

"What's new is incredibly simple: upwellings in the mantle are thousands of kilometers across," Anderson says. The formation of volcanoes then follows from plate tectonics—the theory of how Earth's plates move and behave. Magma, which is less dense than the surrounding mantle, rises until it reaches the bottom of the plates or fissures that run through them. Stresses in the plates, cracks, and other tectonic forces can squeeze the magma out, like how water is squeezed out of a sponge. That magma then erupts out of the surface as volcanoes. The magma comes from within the upper 200 kilometers of the mantle and not thousands of kilometers deep, as the mantle-plume theory suggests.

"This is a simple demonstration that volcanoes are the result of normal broad-scale convection and plate tectonics," Anderson says. He calls this theory "top-down tectonics," based on Kelvin's initial principles of mantle convection. In this picture, the engine behind Earth's interior processes is not heat from the core but cooling at the planet's surface. This cooling and plate tectonics drives mantle convection, the cooling of the core, and Earth's magnetic field. Volcanoes and cracks in the plate are simply side effects.

The results also have an important consequence for rock compositions—notably the ratios of certain isotopes, Natland says. According to the mantle-plume idea, the measured compositions derive from the mixing of material from reservoirs separated by thousands of kilometers in the upper and lower mantle. But if there are no mantle plumes, then all of that mixing must have happened within the upwellings and nearby mantle in Earth's top 1,000 kilometers.

The paper is titled "Mantle updrafts and mechanisms of oceanic volcanism."

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Seeing Protein Synthesis in the Field

Caltech researchers have developed a novel way to visualize proteins generated by microorganisms in their natural environment—including the murky waters of Caltech's lily pond, as in this image created by Professor of Geobiology Victoria Orphan and her colleagues. The method could give scientists insights to how uncultured microbes (organisms that may not easily be grown in the lab) react and adapt to environmental stimuli over space and time.

The visualization technique, dubbed BONCAT (for "bioorthogonal non-canonical amino-acid tagging"), was developed by David Tirrell, Caltech's Ross McCollum–William H. Corcoran Professor and professor of chemistry and chemical engineering. BONCAT uses "non-canonical" amino acids—synthetic molecules that do not normally occur in proteins found in nature and that carry particular chemical tags that can attach (or "click") onto a fluorescent dye. When these artificial amino acids are incubated with environmental samples, like lily-pond water, they are taken up by microorganisms and incorporated into newly formed proteins. Adding the fluorescent dye to the mix allows these proteins to be visualized within the cell.

For example, in the image, the entire microbial community in the pond water is stained blue with a DNA dye; freshwater gammaproteobacteria are labeled with a fluorescently tagged short-chain ribosomal RNA probe, in red; and newly created proteins are dyed green by BONCAT. The cells colored green and orange in the composite image, then, show those bacteria—gammaproteobacteria and other rod-shaped cells—that are actively making proteins.

"You could apply BONCAT to almost any type of sample," Orphan says. "When you have an environmental sample, you don't know which microorganisms are active. So, assume you're interested in looking at organisms that respond to methane. You could take a sample, provide methane, add the synthetic amino acid, and ask which cells over time showed activity—made new proteins—in the presence of methane relative to samples without methane. Then you can start to sort those organisms out, and possibly use this to determine protein turnover times. These questions are not typically tractable with uncultured organisms in the environment." Orphan's lab is also now using BONCAT on samples of deep-sea sediment in which mixed groups of bacteria and archaea catalyze the anaerobic oxidation of methane.

Why sample the Caltech lily pond? Roland Hatzenpichler, a postdoctoral scholar in Orphan's lab, explains: "When I started applying BONCAT on environmental samples, I wanted to try this new approach on samples that are both interesting from a microbiological standpoint, as well as easily accessible. Samples from the lily pond fit those criteria." Hatzenpichler is lead author of a study describing BONCAT that appeared as the cover story of the August issue of the journal Environmental Microbiology.

The work is supported by the Gordon and Betty Moore Foundation Marine Microbiology Initiative.

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Measuring Earthquake Shaking with the Community Seismic Network

In 2011, the Community Seismic Network (CSN) began taking data from small, inexpensive accelerometers in the greater Pasadena area. Able to measure both weak and strong ground movement along three axes, these accelerometers promise to provide very high-resolution data of shaking produced by seismic activity in the region. "We have quite a large deployment of these accelerometers, about 400 sensors now, in people's homes but also in schools and businesses, and in some high-rise buildings downtown," says Julian Bunn, principal computational scientist for Caltech's Center for Advanced Computing Research. "We run client software on each sensor that sends data up into Google's cloud. From there we can analyze the data from all these sensors."

The CSN is the brainchild of Professor of Geophysics Rob Clayton, Professor of Engineering Seismology Tom Heaton, and Simon Ramo Professor of Computer Science, Emeritus, K. Mani Chandy, and a collaboration among Caltech's seismology, earthquake engineering, and computer science departments. It has successfully detected the many earthquakes that have occurred since its establishment. In addition, the CSN currently assists in damage assessment by generating maps of peak ground acceleration before accurate measurements of the earthquake epicenter or magnitude are known.

However, the CSN could provide further assistance in damage assessment if it were also able to produce an immediate estimation of the magnitude. "Right now we only detect an event," says Bunn. "We don't estimate the magnitude." This is where Caltech junior Kevin Li comes in. Li has been spending his 10-week Summer Undergraduate Research Fellowship (SURF) trying to develop a machine-learning system that can accurately estimate the magnitude of an earthquake within seconds of its detection.

Of course, the USGS already accurately measures earthquake magnitudes, but it does so by means of highly sophisticated—and expensive—seismometers that are located several miles apart from one another. Post-quake "ShakeMaps" are then constructed by extrapolating from this data to estimate shaking between seismometer stations. The problem, as recent quakes in California have shown, is that shaking can vary widely even from block to block—as can damage and potential injuries. The CSN proposes to capture this variation and provide an important resource for first responders during major earthquakes, pinpointing areas likely to have the most damage. Should this pilot study prove fruitful, says Bunn, it could "provide better hazard mitigation in parts of the world where they can't afford these very expensive installations."

"Seismic networks like the USGS use really fine sensors," explains Li. "However, the CSN sensors sacrifice fine measurement precision for low-cost efficiency. The sensors record particularly noisy data, far noisier than what the USGS system is used to. As a result, we cannot just adopt the algorithms from USGS. We need to develop our own system."

So far, says Li, the work is going well. "I'm currently still in week nine of my 10 weeks, but I have a system that seems like it can give a magnitude estimate that is within 1 unit of magnitude. For instance, if the estimation is 5.4, then the real magnitude should be somewhere between 4.4 and 6.4. If we can get to better precision than that, even better."

Li notes that his system has so far only been evaluated using USGS magnitudes for previous seismic events over the past two years. "I have yet to test it on a new event. Perhaps I can test it on the data from the recent earthquake in Napa once Caltech has finished processing it."

CSN is supported by funding from the Gordon and Betty Moore Foundation.

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Measuring Earthquake Shaking
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GPS Names a New Division Chair

John Grotzinger, the Fletcher Jones Professor of Geology, has been named the new chair of the Division of Geological and Planetary Sciences (GPS). With his selection formally approved by the Board of Trustees earlier this year, Grotzinger took the helm of the division on September 1. He will replace current division chair Ken Farley, the W. M. Keck Foundation Professor of Geochemistry.

Grotzinger, who had previously served as both a visiting associate professor at Caltech in 1996 and a Moore Distinguished Scholar in 2004, joined the faculty and the division in 2005. His research is focused on the early environmental evolution of both Earth and Mars. By working to understand the chemical and physical conditions of the early oceans and atmosphere on our planet, Grotzinger's group has been able to determine the influence of those conditions on microbial evolution and the emergence of animals. He also works as the project scientist of the Mars Science Laboratory mission, whose Curiosity rover has been exploring the Red Planet since 2012, gaining insights into how water was involved in the early history of Mars and what its potential role might have been in supporting microbial habitability, had life ever originated there.

"I'm thrilled John Grotzinger has been selected as the new GPS chair—he's a uniquely broad-based scientist who's brought his keen geological insight to bear on solving problems in fields that span nearly the entire breadth of GPS, from geobiology to planetary science, geophysics and geochemistry," says Michael Gurnis, John E. and Hazel S. Smits Professor of Geophysics and director of the Seismological Laboratory, who was the chair of the search committee. "Combined with his enormous experience leading MSL, I can see that John will be a superb chair of the Division of Geological and Planetary Sciences.

As chair, Grotzinger says he wants to help the faculty and students in GPS to achieve their goals in research and education. "I look forward to supporting the unique excellence that distinguishes our division from its peers at other universities, and I will especially enjoy interacting with the students—and the outstanding young faculty members we've hired over the past few years," Grotzinger says.

"GPS excels at crossing traditional barriers, and I am curious to see how we might continue to catalyze new research opportunities," he adds. "So in addition to maintaining the existing excellence of our programs, I also want to find ways to develop the future by fostering creative interactions and finding new mechanisms to support this emerging research."

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Wednesday, September 10, 2014
Avery Dining Hall – Avery House

RESCHEDULED to Sept 24th: A chance to meet Pasadena Unified School District Leadership

Checking the First Data from OCO-2

On July 2, NASA successfully launched its first satellite dedicated to measuring carbon dioxide in Earth's atmosphere. The Orbiting Carbon Observatory-2 (OCO-2) mission—operated by NASA's Jet Propulsion Laboratory—will soon provide atmospheric carbon dioxide measurements from thousands of points all over the planet. Last week, the satellite reached its proper orbit—meaning that it is now beginning to return its first data to Earth.

Data from the satellite will be used to help researchers understand the anthropogenic and natural sources of CO2, and how changing levels of the greenhouse gas may affect Earth's climate. But before OCO-2 provides scientists with such a global picture of the carbon cycle—where carbon is being produced and absorbed on Earth—researchers have to convert raw satellite data into a CO2 reading and then, just as importantly, make sure that the reading is accurate. A team of Caltech researchers is playing an instrumental role in this effort.

As it orbits, OCO-2 provides data about levels of atmospheric CO2 by measuring the sunlight that reflects off Earth, below. "OCO-2 measures something that is related to the CO2 measurement we want but it's not directly what we want. So from the reflected light, we have to extract the information about CO2," says Yuk Yung, the Smits Family Professor of Planetary Science.

The process begins with the satellite's instrument, a set of high-resolution spectrometers that measure the intensity of sunlight at different wavelengths, or colors, after it has passed twice through the atmosphere—once from the sun to the surface, and then back from the surface to space. As the satellite orbits, systematically slicing over sections of Earth's atmosphere, it will collect millions of these measurements.

"OCO-2 will provide the measurements of this light at different wavelengths in millions of what we call spectra, but spectra aren't what we really want—what we really want is to know how much carbon dioxide is in the atmosphere," Yung says. "But to get the CO2 information from the spectra, we have to do what's called data retrieval—and that's one of my jobs."

The data retrieval method that Yung and his colleagues designed for OCO-2 compares the light spectra collected by the satellite to a model of how light spectra would look—based on the laws of physics and knowledge of how efficiently CO2 absorbs sunlight. This knowledge, in turn, is derived from laboratory measurements made by Caltech professor of chemical physics Mitchio Okumura and his colleagues at JPL and the National Institute of Standards and Technology.

"To make scientifically meaningful measurements, OCO-2 has to detect CO2 with better than 0.3 percent precision, and that has meant going back to the lab and measuring the spectral properties with extraordinarily high precision," Okumura says. From this retrieval, the researchers determine the amount of CO2 in the atmosphere above each of OCO-2's sampling points.

However, when OCO-2 sends its first CO2 measurements back to Earth for analysis, they'll still have to go through one more check, says Paul Wennberg, the R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering.

"Although the OCO-2 retrieval will calculate the amount of carbon dioxide above the point where the spectrometers pointed, we know that these initial numbers will be wrong until the data are calibrated," Wennberg says. Wennberg and his team provide this calibration with their Total Carbon Column Observing Network (TCCON), a ground-based network of instruments that measure atmospheric CO2 from approximately 20 locations around the world.

TCCON and OCO-2 provide the same type of CO2 measurement—what is called a column average of CO2. This measurement provides the average abundance of CO2 in a column from the ground all the way up through Earth's atmosphere.

About once per day, the OCO-2 instrument will be commanded to point at one of TCCON's stations continuously as it passes overhead. By comparing the Earth-based and space-based measurements, researchers will evaluate the data that they receive from the satellite and improve the retrieval method.

The complete, high-quality information OCO-2 provides about global CO2 levels will be important for researchers and policymakers to determine how human activity influences the carbon cycle—and how these activities contribute to our changing planet.

"A lot of the very first satellites were developed to study astronomy and planets far away. But there has been a shift. Our changing climate means that we now have a big need to study Earth," and the information OCO-2 provides about our atmosphere will be an important part of filling that need, says Yung.

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The Birth and Death of Our Solar System: An Interview with Konstantin Batygin

Konstantin Batygin recently joined the Caltech faculty as assistant professor of planetary science, following graduate school at Caltech (PhD '12) and a postdoc at the Harvard-Smithsonian Center for Astrophysics. Batygin was born in Moscow, attended elementary and middle school outside Tokyo, and moved to San Jose while in high school. He chose UC Santa Cruz for college to be near the beach and to continue playing with the band he had formed in high school. He decided to major in astrophysics the day before classes started his freshman year.

It's a decision Batygin has never regretted. Early in his undergraduate career, a mentor started Batygin thinking about the fate of our solar system. From there, one question led to another and another, and now Batygin works on everything from the evolution of our solar system to the weather on exoplanets.

Batygin recently spoke about the string of synchronicities that brought him to planetary astrophysics and to Caltech.

How did you find your way into astrophysics and planetary science?

I applied to UC Santa Cruz as an engineering major. On registration day, I had to go pick up a piece of paper from some office, and there was a guy there. I don't know if he was a student or what. But he said to me, "Yo dawg, what's your major?" I told him it was engineering. And he said, "You should do astrophysics. It's dope." As I left the office, I thought, "Wow, astrophysics does sound totally dope." So I went to the physics department and changed my major.

When did you develop an interest in planetary science?

Planetary science wasn't in my plan. I wanted to do high-energy astrophysics. But then at a department party I met Greg Laughlin, a planetary scientist at UC Santa Cruz. He's a very creative guy and an expert in chaos theory. He suggested that we might try to figure out what the long-term fate of our solar system would be. I thought to myself, "Surely someone like Newton must have solved that problem already." But I was wrong about that. As soon as we started working on this stuff, I just fell in love with it. It's a very counterintuitive situation. You tend to think that the motion of the planets is like clockwork, where things keep going around in an orderly fashion. You only need one physics law—gravity—to predict the basic motions of the planets. But it's actually a very complicated problem.

In what way?

Part of it is pretty easy. For the numerical simulations involved, any reasonably astute graduate student could do the work. The more difficult part of the problem is trying to explain what we find in the numerical simulations. For example, the simulations reveal that if you wait long enough, Mercury will leave the solar system. It will become unstable, its orbit will become unbound, and it will take off.

Really? Even though it's the closest planet to the sun, it just flies off rather than falling into the sun?

Yes. It's called chaotic diffusion. This happens over a multibillion-year timescale. Planetary orbits are a little bit like weather. We can't predict the weather for longer than three days. But we can generally expect that the weather is not going to change by thousands of degrees; it's going to be in some bounded range. Planetary orbits are like that. They vary, but they mostly hang out in a well-defined region of phase space. Occasionally, though, they leave that phase space and transition into a different shape. This is why Mercury takes off at some point in the future. It's a beautiful problem. You've got eight members of the system—planets—whose masses are low. But over long time spans, they exchange angular momentum in a deterministic yet unpredictable manner. If you wait long enough, at one point Mercury bites off more angular momentum deficit than it can chew and leaves the solar system.

Why did you choose Caltech for graduate school?

First I got an email from Mike Brown [Caltech's Richard and Barbara Rosenberg Professor and professor of planetary astronomy], saying congratulations, I had been admitted to Caltech. I thought, "Well, this is a funny coincidence, another Mike Brown." Then I realized, "Wait, this is the Mike Brown!" So I came to campus, just for a day, but I immediately knew this was where I would come for graduate school. I have never felt quite as at home as I do at Caltech. That's been true from the first moment.

Why do you think you had such an instant affinity for Caltech?

Southern California is pretty awesome, so there's that. But I think Caltech has a unique aura, and I think that has to do with quality. It is the pursuit of quality rather than quantity, so to speak. And that's basically why we do science.

Had you completed your work on the long-term fate of our solar system before you came to Caltech for grad school?

Yes, but I've actually gone back and revisited that problem. We've tried to put ourselves in a time before computers were around, and ask what we learn about orbits in our solar system if we don't assume that everything works like a clock, to ask if we can get at the numerically obtained results with perturbation theory. We're hoping to proceed entirely analytically, getting to the underlying physical structure of dynamic instability.

Newton was working with an assumption of clockwork motion?

No, when Newton came out with his law, he himself didn't believe that the solar system would be stable. He believed that gravity would gradually unravel it, and that God would have to come in and reset it. The idea of perfect determinism was introduced later by Laplace, among others. We're seeing the same instability, but looking at secular solutions to the problem of what happens to the solar system over time.

What are you working on now?

In effect I'm continuing all the projects that I've started up until now. When I came to Caltech as a grad student I was pretty comfortable with working on the dynamics of the solar system. But then Dave Stevenson [the Marvin L. Goldberger Professor of Planetary Science] shattered my world by opening up a whole set of other interesting problems in planetary science. And Mike Brown and I worked on the solar system, but we examined the beginning rather than the end. The early evolution of the solar system is also very wild and chaos-dominated. I also ended up working on the interiors of exoplanets and the formation of the Kuiper belt, and at Harvard I worked on the evolution of protoplanetary disks and the weather on exoplanets.

Do you observe the planets directly, or do you use other people's observations?

No, I don't observe. I should not be allowed near a telescope. I have great respect for observers, but it doesn't come naturally for me. You have to be really focused. I don't have observing capabilities.

Have you found a band to play with since you got back from your postdoc in the Boston area?

Yes, my band, the Seventh Season, keeps remaking itself. You can find our music on iTunes. Once in a while we get a check from iTunes for $20 or so. We're working on two new albums now. They're untitled. We're open to suggestions.

And do you still like the beach?

I haven't been surfing yet, but we went to the beach last weekend. My daughter loved the water. It was a scandal when I tried to take her out after an hour in the ocean.

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Cynthia Eller
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The Birth and Death of Our Solar System
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