Hear directly from four of our graduate students as they talk a little about what drives their research curiosity and how they're working to investigate a wide range of probing questions about the natural world.
Seismology has undergone great changes since the beginning of the digital era in the 1970s, revolutionizing the way we collect seismic data. While our capacity to characterize and map earthquakes all over the globe is highly-improved, we are still facing fundamental, unanswered questions. Among them figures one of primary importance for society: can we predict earthquakes? Although many seismologists have resigned themselves to think that earthquakes are by nature unpredictable, the ongoing progress in seismic instrumentation is driving new methods for studying the Earth.
Addressing the question of earthquake prediction is not trivial; it involves developments in both theory and data analysis. My research with Robert van der Hilst and Michel Campillo leverages the massive amount of data with automatic processing to detect earthquakes and create catalogs that store information about their locations and timings. This work is at the interface of seismology and data science: on one hand, we need to have a clear understanding of the physics of seismic wave propagation to design algorithms that make sense, and on the other hand, we need to know how to extract the information we are looking for when it is hidden in a large volume of data.
Another part of my research goes one step further: after detecting and locating many earthquakes, it becomes possible to study the mechanism responsible for the radiation of seismic waves recorded by the seismometers. I mostly focus on comparing the behavior of small earthquakes with large ones, and also between small earthquake groups. The goal of such a study is to validate or contradict the paradigm that all earthquakes are self-similar—an oversimplification of reality that might prevent us from capturing the nature(s) of earthquakes.
Prior to the detection of the first exoplanet two decades ago, our ideas about how planets form were largely based on the example of a single planetary system: our own. The subsequent discovery of hundreds more planetary systems has challenged these theories, revealing the incredible diversity of planets that nature produces. At the same time, new spacecraft missions in our solar system have allowed us to begin to probe the earliest days of its formation with a precision currently impossible for systems farther away. I am interested in combining these exquisite observations of our solar system with the rapidly-expanding exoplanetary census to better understand how planets form, why some systems look so different from our own, and how common the formation of Earth-like planets may be.
With Hilke Schlichting, I am working to understand a class of planets known as super-Earths. These worlds, which are larger than the Earth, are incredibly abundant in our galaxy, yet they have no solar system analog. Some super-Earths appear to be mostly rocky, but others have significant atmospheres of hydrogen and helium. We are investigating whether collisions between planets can boil off their atmospheres, potentially explaining this diversity.
In collaboration with Benjamin Weiss, I am also exploring the formation of our own solar system with data from the European Space Agency’s Rosetta mission to the surface of comet 67P/Churyumov-Gerasimenko. Comets like 67P are thought to be planetesimals—the early building blocks of planets leftover from the formation of our solar system 4.5 billion years ago. Specifically, we’re working to understand what magnetic measurements of comet 67P’s surface may reveal about the magnetic environment in the early solar system and the mechanism of planetesimal accretion.
One of the fascinating things that drew me to the Earth sciences was the fact that the climate of our planet may have experienced completely different states at various points in its history. We know, for example, that during a large part of Earth’s past (millions to billions of years ago), the climate was much warmer than today, with little to no ice at the poles. By contrast, there is also growing evidence that the planet was subject to intense periods of glaciation, termed “Snowball Earth,” during which ice sheets could have reached all the way down to the equator. One could say it is fortunate that the modern climate lies comfortably between these “Hothouse” and “Icehouse” extremes!
For my research, I use a range of climate models to investigate what conditions could lead to an abrupt shift from a warm climate state to a much colder one. In particular, I am interested in the possibility that very large volcanic eruptions could have expelled enough gases and particles into the atmosphere to block sunlight from reaching the surface and cause extreme cooling at the Earth’s surface. The latest known record of these mega-eruptions originates from the Toba event (75,000 years ago), which likely cooled the planet by up to 10°C for several decades. My results show that if enough of these eruptions occurred over a timescale of several hundred years, the climate could perhaps tip into a long-term glacial state.
What I love about this research is that we are examining very fundamental properties of the climate, with questions like: How sensitive it is to abrupt perturbations? How does it behave near tipping points? How do the oceans act as a buffer against change? The answers are crucial to understanding Earth’s past and future climate, and may help us infer important properties of planets beyond our own.
Earth’s smallest organisms—microbes—have reshaped the planet’s chemical and physical systems over billions of years. My research focuses on the tandem evolution of microbes and their environment. But understanding how and when microorganisms altered global geochemistry is tricky. Microbial fossils are sparse, especially on deep timescales. The Fournier Lab turns to the other logbook of early life: the genomic record, which stores powerful information about the past within the DNA of modern organisms.
I’m studying the evolution of microbial nitrogen cycling, trying to determine when and which microbes evolved proteins used to morph nitrogen from one form into another—for example, turning toxic cyanide into ammonia, or converting energy-rich compounds into the abundant nitrogen gas in Earth’s atmosphere. Genes that encode such abilities have been refined and exchanged in microbes for millions of years. As microbes adapt and diverge over time, these functional genes accumulate changes. By analyzing the differences among genes in diverse microorganisms, we can craft a better picture of how and when different biochemical capacities developed.
While the genomic record is powerful, it’s often cryptic and incomplete, just like the geological fossil record. Our lab uses advanced computational tools to enhance the depth and accuracy of information extracted from genetic sequences—and we refine these results in the context of established understanding of how DNA changes, as well as concrete geological data from fossils and biomarker sources.
I think often of the two engraved inscriptions outside the U.S. National Archives: “Study the Past/ What is Past is Prologue.” Insights into life’s early days could illuminate how modern environmental systems evolved. And they could also provide details about how they operate today—and where they’re headed next.
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