Mike Brown's "Living Textbook"

Feynman Teaching Award winner Mike Brown ventures into new fields of instruction: the Massive Open Online Course, or MOOC, and the "flipped" classroom, which inverts the traditional arrangement of listening to lectures in class and doing assignments at home.

Mike Brown, the Richard and Barbara Rosenberg Professor and Professor of Planetary Astronomy, is teaching a nine-week course to 20 Caltech undergraduates—and some 2,000 Internet users. Geology/Astronomy 11c, "Introduction to Earth and Planetary Sciences: Planetary Sciences," is also available on line at Coursera.org as "The Science of the Solar System."

"It's pretty amazing," says Brown. In one sitting, I teach more students than I would in my entire career at Caltech."

The course's videos are grouped into four multiweek units that cover the history of water on Mars, the interiors of the giant planets, the formation of the solar system as recorded in the rubble of small bodies left behind, and the search for life beyond Earth. Every lecture demonstrates how planetary science draws on techniques from an assortment of disciplines to attack a problem. For example, he describes how in 1966 Caltech physics professor Robert Leighton (BS '41, MS '44, PhD '47) and planetary science professor Bruce Murray used basic physics to conclude that Mars's polar caps could not be ordinary ice, as had generally been assumed, but must instead be dry ice—frozen carbon dioxide. The unit as a whole traces the history of both the planet and our quest to understand it, from our first telescopic observations to our current fleet of spacecraft. The lectures are sprinkled with personal asides, such as the fact that the very first front-page color photograph to run in Brown's hometown newspaper was of the rusty, rock-strewn desert of Mars's Chryse Planitia, beamed back from the Viking One lander on July 21, 1976.

The for-credit version taken by Caltech undergraduates is a "flipped" class. Students watch the lectures on their own time, and the instructional sessions are devoted to personal interactions with one another and with Brown. After he fields questions on the week's lectures, the students break up into small groups. For the Mars unit, each group was provided the location of one of the backup landing sites selected for Curiosity, the Mars Science Laboratory rover, and told to write a report on the site's geologic history based on the wealth of data and images available online. The reports were to pay special attention to the times and forms in which water might have been present at the sites. Each group then had to make the case for its site as the best choice in a presentation to the entire class.

"The goal is to have them synthesize the individual things they learned from the lectures and apply it to spots that we didn't necessarily talk about," Brown says. "I told them to organize their thinking by just looking at the lectures' titles. There's photogeology, where you compare pictures to landforms on Earth to see what's going on. There are outflow channels, dendritic channels, valley networks. There's the altimetry, which tells you about slopes and drainages. You can look at the gamma-ray data to see if there's subsurface water. And the infrared spectroscopy tells you about the mineralogy, which tells you whether water was present when that rock was laid down. You can apply almost everything that was in the lectures to each of these sites."

After the groups have split up, Brown works the room, listening to the students' discussions and occasionally asking a question. As one group begins pooling what they've gleaned from their individual readings about their site, a student says he doesn't see any evidence for what one paper claims to be an ancient shoreline. Brown remarks, "Just because a paper's been published doesn't mean it's right. How do you decide if a conclusion is credible?" Another student replies, "By how often it's cited?" "That's a good way," Brown agrees. "And it's very easy to do that these days. When I was a student, we had to haul out all these big, thick books. Of course, if all the citations say, 'This is the most idiotic thing I've ever read,' that would be bad." As the period proceeds, the discussion gets more detailed, and Brown's questions become more penetrating. "I'm going to disagree with everything you say to be sure you have the evidence for it," he explains to them. "If I don't ask these questions, NASA will."

This is the second year that Brown has flipped this class. "I'm still learning how it works," he says. When he created the course last year, he recalls, "I spent a lot of time recording. It was a full-time job from January to mid-May, which is crazy for a nine-week class. But the promise was that it all pays off in the subsequent years. Some parts didn't work so well, so I've had to change them, and some parts change because there are always new things happening in space. This time around, I got to put in all the stuff about landing on a comet [i.e., the European Space Agency's Rosetta mission, which landed a probe on comet 67P/Churyumov-Gerasimenko last November], which is super cool, and next year I'll get to do the Pluto flyby stuff [NASA's New Horizons mission, set to flyby the dwarf planet on July 14 of this year]. I think of it as a living textbook."

It took some 45 minutes to record one 15-minute lecture, of which there are about 90. Editing each segment took another two hours. "That was a surprise," Brown says. "At first, I was doing them all myself, but I very quickly cried uncle and sent them over to Leslie [Maxfield (BS '95), Caltech's director of Academic Media Technologies (AMT)]. They did a much better job. This year, with the re-recordings, there's not as much to do, so I'm doing them all myself."

Brown records all the videos in his office using the built-in camera on his computer monitor. In the middle of the room, a portable green-screen backdrop on long-term loan from AMT hangs from borrowed light stands. Hanging next to the screen is the lone blue shirt that Brown wears for continuity. He's perpetually clean-shaven now for the same reason, and he gets the same haircut, on schedule, every eight weeks. "My wife is thrilled," he says. "I used to say, 'Oh, yeah. My hair is 10 feet long; I should get a haircut.' Now she says, 'You're getting another haircut already?'"

Caltech students get nine units of credit for completing the course; people from the outside world get a certificate of completion "good for printing out and hanging on your wall," Brown says. "And as totally meaningless as these certificates are, people are very motivated by them. They're enjoying the class, they're trying to learn, and they want that certificate. I'm very excited about this class because it's the best outreach tool I've ever found, in a very interesting niche where we don't normally do outreach. This is intense—2,000 people spending nine weeks doing three or four hours a week of planetary science. That's crazy. And they were an engaged, dedicated group by the end. They feel a big sense of allegiance to all aspects of it: to me, to Caltech, and I think to Coursera as well. It's a pretty great tool."

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Douglas Smith
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Using Radar Satellites to Study Icelandic Volcanoes and Glaciers

On August 16 of last year, Mark Simons, a professor of geophysics at Caltech, landed in Reykjavik with 15 students and two other faculty members to begin leading a tour of the volcanic, tectonic, and glaciological highlights of Iceland. That same day, a swarm of earthquakes began shaking the island nation—seismicity that was related to one of Iceland's many volcanoes, Bárðarbunga caldera, which lies beneath Vatnajökull ice cap.

As the trip proceeded, it became clear to scientists studying the event that magma beneath the caldera was feeding a dyke, a vertical sheet of magma slicing through the crust in a northeasterly direction. On August 29, as the Caltech group departed Iceland, the dike triggered an eruption in a lava field called Holuhraun, about 40 kilometers (roughly 25 miles) from the caldera just beyond the northern limit of the ice cap.

Although the timing of the volcanic activity necessitated some shuffling of the trip's activities, such as canceling planned overnight visits near what was soon to become the eruption zone, it was also scientifically fortuitous. Simons is one of the leaders of a Caltech/JPL project known as the Advanced Rapid Imaging and Analysis (ARIA) program, which aims to use a growing constellation of international imaging radar satellites that will improve situational awareness, and thus response, following natural disasters. Under the ARIA umbrella, Caltech and JPL/NASA had already formed a collaboration with the Italian Space Agency (ASI) to use its COSMO-SkyMed (CSK) constellation (consisting of four orbiting X-Band radar satellites) following such events.

Through the ASI/ARIA collaboration, the managers of CSK agreed to target the activity at Bárðarbunga for imaging using a technique called interferometric synthetic aperture radar (InSAR). As two CSK satellites flew over, separated by just one day, they bounced signals off the ground to create images of the surface of the glacier above the caldera. By comparing those two images in what is called an interferogram, the scientists could see how the glacier surface had moved during that intervening day. By the evening of August 28, Simons was able to pull up that first interferogram on his cell phone. It showed that the ice above the caldera was subsiding at a rate of 50 centimeters (more than a foot and a half) a day—a clear indication that the magma chamber below Bárðarbunga caldera was deflating.

The next morning, before his return flight to the United States, Simons took the data to researchers at the University of Iceland who were tracking Bárðarbunga's activity.

"At that point, there had been no recognition that the caldera was collapsing. Naturally, they were focused on the dyke and all the earthquakes to the north," says Simons. "Our goal was just to let them know about the activity at the caldera because we were really worried about the possibility of triggering a subglacial melt event that would generate a catastrophic flood."

Luckily, that flood never happened, but the researchers at the University of Iceland did ramp up observations of the caldera with radar altimetry flights and installed a continuous GPS station on the ice overlying the center of the caldera.

Last December, Icelandic researchers published a paper in Nature about the Bárðarbunga event, largely focusing on the dyke and eruption. Now, completing the picture, Simons and his colleagues have developed a model to describe the collapsing caldera and the earthquakes produced by that action. The new findings appear in the journal Geophysical Journal International.

"Over a span of two months, there were more than 50 magnitude-5 earthquakes in this area. But they didn't look like regular faulting—like shearing a crack," says Simons. "Instead, the earthquakes looked like they resulted from movement inward along a vertical axis and horizontally outward in a radial direction—like an aluminum can when it's being crushed."

To try to determine what was actually generating the unusual earthquakes, Bryan Riel, a graduate student in Simons's group and lead author on the paper, used the original one-day interferogram of the Bárðarbunga area along with four others collected by CSK in September and October. Most of those one-day pairs spanned at least one of the earthquakes, but in a couple of cases, they did not. That allowed Riel to isolate the effect of the earthquakes and determine that most of the subsidence of the ice was due to what is called aseismic activity—the kind that does not produce big earthquakes. Thus, Riel was able to show that the earthquakes were not the primary cause of the surface deformation inferred from the satellite radar data.

"What we know for sure is that the magma chamber was deflating as the magma was feeding the dyke going northward," says Riel. "We have come up with two different models to explain what was actually generating the earthquakes."

In the first scenario, because the magma chamber deflated, pressure from the overlying rock and ice caused the caldera to collapse, producing the unusual earthquakes. This mechanism has been observed in cases of collapsing mines (e.g., the Crandall Canyon Mine in Utah).

The second model hypothesizes that there is a ring fault arcing around a significant portion of the caldera. As the magma chamber deflated, the large block of rock above it dropped but periodically got stuck on portions of the ring fault. As the block became unstuck, it caused rapid slip on the curved fault, producing the unusual earthquakes.

"Because we had access to these satellite images as well as GPS data, we have been able to produce two potential interpretations for the collapse of a caldera—a rare event that occurs maybe once every 50 to 100 years," says Simons. "To be able to see this documented as it's happening is truly phenomenal."

Additional authors on the paper, "The collapse of Bárðarbunga caldera, Iceland," are Hiroo Kanamori, John E. and Hazel S. Smits Professor of Geophysics, Emeritus, at Caltech; Pietro Milillo of the University of Basilicata in Potenza, Italy; Paul Lundgren of JPL; and Sergey Samsonov of the Canada Centre for Mapping and Earth Observation. The work was supported by a NASA Earth and Space Science Fellowship and by the Caltech/JPL President's and Director's Fund.

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Using Radar Satellites to Study Volcanoes
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Tuesday, May 26, 2015 to Friday, May 29, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

CTLO Presents Ed Talk Week 2015

Ditch Day? It’s Today, Frosh!

Today we celebrate Ditch Day, one of Caltech's oldest traditions. During this annual spring rite—the timing of which is kept secret until the last minute—seniors ditch their classes and vanish from campus. Before they go, however, they leave behind complex, carefully planned out puzzles and challenges—known as "stacks"—designed to occupy the underclassmen and prevent them from wreaking havoc on the seniors' unoccupied rooms.

Follow the action on Caltech's Facebook, Twitter, and Instagram pages as the undergraduates tackle the puzzles left for them to solve around campus. Join the conversation by sharing your favorite Ditch Day memories and using #CaltechDitchDay in your tweets and postings.

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Monday, May 18, 2015
Brown Gymnasium – Scott Brown Gymnasium

Jupiter’s Grand Attack

Caltech, JPL Team Captures Movement on Nepal Earthquake Fault Rupture

Using a combination of satellite radar imaging data, GPS data measured in and near Nepal, and seismic observations from instruments around the world, Caltech and JPL scientists have constructed a preliminary picture of what happened below Earth's surface during the recent 7.8-magnitude Gorkha earthquake in Nepal.

The team's observations and models of the April 25, 2015 earthquake, produced through the Advanced Rapid Imaging and Analysis (ARIA) project—a collaboration between Caltech and JPL—include preliminary estimates of the slippage of the fault beneath Earth's surface that resulted in the deaths of thousands of people. In addition, the ARIA scientists have provided first responders and key officials in Nepal with information and maps that show block-by-block building devastation as well as measurements of ground movement at individual locations around the country.

"As the number of orbiting imaging radar and optical satellites that form the international constellation increases, the expected amount of time it takes to acquire an image of an impacted area will decrease, allowing for products such as those we have made for Nepal to become more commonly and rapidly available," says Mark Simons, professor of geophysics at Caltech and a member of the ARIA team. "I fully expect that within five years, this kind of information will be available within hours of a big disaster, ultimately resulting in an ability to save more lives after a disaster and to make assessment and response more efficient in both developed and developing nations."

Over the last five years, Simons and his colleagues in Caltech's Seismological Laboratory and at JPL have been developing the approaches, infrastructure, and technology to rapidly and automatically use satellite-based observations to measure the movement of Earth's surface associated with earthquakes, volcanoes, landslides and other geophysical processes.  

"ARIA is ultimately aimed at providing tools and data—for use by groups ranging from first responders, to government agencies, and individual scientists—that can help improve situational awareness, response, and recovery after many natural disasters," Simons says. "The same products also provide key observational constraints on our physical understanding of the underlying processes such as the basic physics controlling seismogenic behavior of major faults."

ARIA is funded through a combination of support from JPL, Caltech, and NASA.

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Caltech, JPL Team Get Clearer Picture of Nepal Earthquake
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Tuesday, May 19, 2015
Guggenheim 101 (Lees-Kubota Lecture Hall) – Guggenheim Aeronautical Laboratory

Science in a Small World - Short Talks

Tuesday, May 19, 2015
Dabney Hall, Garden of the Associates – The Garden of the Associates

Science in a Small World - Poster Session #2

Tuesday, May 19, 2015
Dabney Hall, Garden of the Associates – The Garden of the Associates

Science in a Small World - Poster Session #1

Tracking Photosynthesis from Space

Watching plants perform photosynthesis from space sounds like a futuristic proposal, but a new application of data from NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite may enable scientists to do just that. The new technique, which allows researchers to analyze plant productivity from far above Earth, will provide a clearer picture of the global carbon cycle and may one day help researchers determine the best regional farming practices and even spot early signs of drought.

When plants are alive and healthy, they engage in photosynthesis, absorbing sunlight and carbon dioxide to produce food for the plant, and generating oxygen as a by-product. But photosynthesis does more than keep plants alive. On a global scale, the process takes up some of the man-made emissions of atmospheric carbon dioxide—a greenhouse gas that traps the sun's heat down on Earth—meaning that plants also have an important role in mitigating climate change.

To perform photosynthesis, the chlorophyll in leaves absorbs sunlight—most of which is used to create food for the plants or is lost as heat. However, a small fraction of that absorbed light is reemitted as near-infrared light. We cannot see in the near-infrared portion of the spectrum with the naked eye, but if we could, this reemitted light would make the plants appear to glow—a property called solar induced fluorescence (SIF). Because this reemitted light is only produced when the chlorophyll in plants is also absorbing sunlight for photosynthesis, SIF can be used as a way to determine a plant's photosynthetic activity and productivity.

"The intensity of the SIF appears to be very correlated with the total productivity of the plant," says JPL scientist Christian Frankenberg, who is lead for the SIF product and will join the Caltech faculty in September as an associate professor of environmental science and engineering in the Division of Geological and Planetary Sciences.

Usually, when researchers try to estimate photosynthetic activity from satellites, they utilize a measure called the greenness index, which uses reflections in the near-infrared spectrum of light to determine the amount of chlorophyll in the plant. However, this is not a direct measurement of plant productivity; a plant that contains chlorophyll is not necessarily undergoing photosynthesis. "For example," Frankenberg says, "evergreen trees are green in the winter even when they are dormant."

He adds, "When a plant starts to undergo stress situations, like in California during a summer day when it's getting very hot and dry, the plants still have chlorophyll"—chlorophyll that would still appear to be active in the greenness index—"but they usually close the tiny pores in their leaves to reduce water loss, and that time of stress is also when SIF is reduced. So photosynthesis is being very strongly reduced at the same time that the fluorescence signal is also getting weaker, albeit at a smaller rate."

The Caltech and JPL team, as well as colleagues from NASA Goddard, discovered that they could measure SIF from orbit using spectrometers—standard instruments that can detect light intensity—that are already on board satellites like Japan's Greenhouse Gases Observing Satellite (GOSAT) and NASA's OCO-2.

In 2014, using this new technique with data from GOSAT and the European Global Ozone Monitoring Experiment–2 satellite, the researchers scoured the globe for the most productive plants and determined that the U.S. "Corn Belt"—the farming region stretching from Ohio to Nebraska—is the most photosynthetically active place on the planet. Although it stands to reason that a cornfield during growing season would be actively undergoing photosynthesis, the high-resolution measurements from a satellite enabled global comparison to other plant-heavy regions—such as tropical rainforests.

"Before, when people used the greenness index to represent active photosynthesis, they had trouble determining the productivity of very dense plant areas, such as forests or cornfields. With enough green plant material in the field of view, these greenness indexes can saturate; they reach a maximum value they can't exceed," Frankenberg says. Because of the sensitivity of the SIF measurements, researchers can now compare the true productivity of fields from different regions without this saturation—information that could potentially be used to compare the efficiency of farming practices around the world.

Now that OCO-2 is online and producing data, Frankenberg says that it is capable of achieving higher resolution than the preliminary experiments with GOSAT. Therefore, OCO-2 will be able to provide an even clearer picture of plant productivity worldwide. However, to get more specific information about how plants influence the global carbon cycle, an evenly distributed ground-based network of spectrometers will be needed. Such a network—located down among the plants rather than miles above—will provide more information about regional uptake of carbon dioxide via photosynthesis and the mechanistic link between SIF and actual carbon exchange.

One existing network, called FLUXNET, uses ground-based towers to measure the exchange of carbon dioxide, or carbon flux, between the land and the atmosphere from towers at more than 600 locations worldwide. However, the towers only measure the exchange of carbon dioxide and are unable to directly observe the activities of the biosphere that drive this exchange.

The new ground-based measurements will ideally take place at existing FLUXNET sites, but they will be performed with a small set of high-resolution spectrometers—similar to the kind that OCO-2 uses—to allow the researchers to use the same measurement principles they developed for space. The revamped ground network was initially proposed in a 2012 workshop at the Keck Institute for Space Studies and is expected to go online sometime in the next two years.

In the future, a clear picture of global plant productivity could influence a range of decisions relevant to farmers, commodity traders, and policymakers. "Right now, the SIF data we can gather from space is too coarse of a picture to be really helpful for these conversations, but, in principle, with the satellite and ground-based measurements you could track the fluorescence in fields at different times of day," he says. This hourly tracking would not only allow researchers to detect the productivity of the plants, but it could also spot the first signs of plant stress—a factor that impacts crop prices and food security around the world.

"The measurements of SIF from OCO-2 greatly extend the science of this mission", says Paul Wennberg, R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering, director of the Ronald and Maxine Linde Center for Global Environmental Science, and a member of the OCO-2 science team. "OCO-2 was designed to map carbon dioxide, and scientists plan to use these measurements to determine the underlying sources and sinks of this important gas. The new SIF measurements will allow us to diagnose the efficiency of the plants—a key component of the sinks of carbon dioxide."

By using OCO-2 to diagnose plant activity around the globe, this new research could also contribute to understanding the variability in crop primary productivity and also, eventually, the development of technologies that can improve crop efficiency—a goal that could greatly benefit humankind, Frankenberg says.

This project is funded by the Keck Institute for Space Studies and JPL. Wennberg is also an executive officer for the Environmental Science and Engineering (ESE) program. ESE is a joint program of the Division of Engineering and Applied Science, the division of Chemistry and Chemical Engineering, and the Division of Geological and Planetary Sciences.

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