Wednesday, September 10, 2014
Avery Dining Hall

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.

Writer: 
Cynthia Eller
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The Birth and Death of Our Solar System
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Looking Forward to 2020 . . . on Mars

A Q&A With Project Scientist Ken Farley

While the Curiosity rover continues to interrogate Gale Crater on Mars, planning is well under way for its successor—another rover that is currently referred to as Mars 2020. The new robotic explorer, scheduled to launch in 2020, will use much of the same technology (even some of the spare parts Curiosity left behind on Earth) to get to the Red Planet. Once there, it will pursue a new set of scientific objectives including the careful collection and storage (referred to as "caching") of compelling samples that might one day be returned to Earth by a future mission. Today, NASA announced the selection of seven scientific instruments that Mars 2020 will carry with it to Mars.

Ken Farley, Caltech's W.M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences, is serving as project scientist for Mars 2020. We recently sat down with him to talk about the mission and his new role.

 

Congratulations on being selected project scientist for this exciting mission. For those of us who do not know exactly what a project scientist does, can you give us a little overview of the job?

Sure. Conveniently, NASA has a definition, which says that the project scientist is responsible for the overall scientific success of the mission. That's a pretty concise explanation, but it encompasses a lot. My main duty thus far has been helping to define the science needs for equipment that we are going to send to Mars. So while we haven't actually done any science yet, we have had to make a lot of design decisions that are related to the science.

The easiest place to illustrate this is in the discussion of what is necessary, from the science point of view, in terms of the samples that we will cache. We have to consider things like how much mass we need to bring back, what kind of magnetic fields and temperatures the samples are going to be exposed to, and how much contamination of different chemical constituents we can allow. Every one of those questions drives a design decision in how you build the drilling system and the caching system. And if you get those wrong, there's nothing you can do. So there's a lot of thought that has to be put into that, and I convey a lot of that information to the engineers.

Now that we have a science team, I will be helping to facilitate all of its investigations and helping the members to work as a team. MSL [the Mars Science Laboratory, Curiosity's mission] is demonstrating how you have to operate when you have a complex tool (a rover) and a bunch of sensors, and every day you have to figure out what you're going to do to further science. The team has to pull together, pool all of its information, and come up with a plan, so an important part of my job will be figuring out how to manage the team dynamics to keep everybody moving forward and not fragmenting.

 

What aspects of the job were particularly appealing to you?

One of the parts of being a division chair that I have really enjoyed is being engaged with something that's bigger than my own research. And there's definitely a lot of that on 2020. It's a huge undertaking. There are not many science projects of this scale to be associated closely with, so this just seemed like a really good opportunity.

The kinds of questions that 2020 is going after—they're really big questions. You could never answer them on your own. The key objective is about life—is there or was there ever life on Mars, and more broadly what does its presence or absence mean about the frequency and evolution of life within the universe? There's no way you could answer these questions on Earth. The simple reason for that is that Mars is covered by rocks that are of the era in which, at least on our planet, we believe life was evolving. There are almost no rocks left of that age on the earth, and the ones that are left have been really badly beaten up. So Mars is a place where you really stand a chance of answering these questions in a way that you probably can't anywhere else.

It's not the kind of science I'm usually associated with, but the mission is trying to address truly profound scientific questions.

 

As you said, space has not been the focus of your research for most of your career. Can you talk a bit about how a terrestrial geochemist like yourself wound up in this role on a Mars mission?

Several years ago, I participated in a workshop about quantifying martian stratigraphy, which was hosted by the Keck Institute for Space Studies [KISS]. One of the topics that was discussed was geochronology—the dating of rocks and other materials—on other planetary bodies, like Mars. This is important for establishing the history of a planet and is particularly challenging because it requires such exacting measurements. After interacting with some people who are now my JPL collaborators at the workshop, it seemed like we might be able to do something special that would help solve this problem. And we got support from KISS to do a follow-on study.

As I was getting deeper and deeper into thinking about how we could do this on Mars, John Grotzinger (the Fletcher Jones Professor of Geology at Caltech and project scientist for MSL) was conducting the landing-site workshops for MSL. He would say things like, "Oh, it would be really great if we could date this." And we'd agree. Then there was a call for participating scientists on MSL. I had no background whatsoever in this, but I knew there was a mass spectrometer on Curiosity. That's one of the analytical instruments we need to make these dating measurements because it allows us to determine the relative abundances of various isotopes in a sample. Since those isotopes are produced at known rates, their abundances tell us something about the age of the sample. So I wrote a proposal basically saying let's see if we can make Curiosity's mass spectrometer work for this purpose. And it did.

 

What do you think led to your selection as project scientist?

Although I don't have a long track record in studying Mars, this mission is possibly the first step in bringing samples back to Earth. In order to do that, you have to answer a lot of questions related to geochemistry, which is my specialty. The geochemistry community is not ordinarily thinking about rocks coming back from Mars. I happen to have enough crossover between what I know about Mars from the work I just described and my background from working in geochemistry labs, especially those working with the type of very small samples we might get back from Mars, to be a good fit.

 

Given Curiosity's success on Mars, why is it important and exciting for us to be sending another rover to the Red Planet?

One thing to realize is that the surface of Mars is more or less equivalent in size to the entire continental surface area of the earth, and we've been to just a few points. It's naturally tempting to look at the few places we have been on Mars and draw grand conclusions from them, but you could imagine if you landed in the middle of the Sahara Desert and studied the earth, you would come up with different answers than if you landed in the Amazon, for example. So that's part of it.

But the big thing that distinguishes Mars 2020 is the fact that we are preparing this cache, which is the first step in a process that will hopefully bring samples back to Earth some day. It's very clear that from the science community's point of view, this is a critical motivation for this mission.

 

How has the experience been working on the mission thus far?

I enjoy it very much. It's extremely different to go from a lab group of two or three people to a project that, at the end of the day, is going to have spent $1.5 billion over the next seven or eight years. It's a completely different scale of operation.

I find it really fascinating to see how everything works. I've spent my entire career among scientists. Suddenly transitioning and working with engineers is interesting because their approach and style is completely different. But they're all extremely good at what they do.

It's a lot of fun to work with these people and to face completely new and unexpected challenges. You never know what new thing is going to pop up.

Writer: 
Kimm Fesenmaier
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Friday, October 10, 2014
Center for Student Services 360 (Workshop Space)

Course Ombudsperson Training

Wednesday, April 1, 2015
Center for Student Services 360 (Workshop Space)

Head TA Network

Wednesday, January 7, 2015
Center for Student Services 360 (Workshop Space)

Head TA Network

Thursday, September 25, 2014
Moore 139

Head TA Network

Friday, April 3, 2015
Center for Student Services 360 (Workshop Space)

TA Training

Wednesday, November 5, 2014
Center for Student Services 360 (Workshop Space)

HALF TIME: A Mid-Quarter Meetup for TAs

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