Unearthing Earth's History
Uncovering billions of years of Earth’s history with a mere speck of dust sounds like magic. And if it is, then Rajdeep Dasgupta is Rice’s resident magician. Using complex machinery to heat and pressurize rock to the thousand-degree and hundred-kilometer-deep conditions of the inner Earth, he and his research team work to uncover the secrets of our planet’s internal processes. “We do small-scale experiments to answer large-scale questions,” said Dasgupta, Rice’s Maurice Ewing Professor in Earth Systems Science.
With tiny sample sizes, his lab work has implications on extraordinarily large scales. Where we often think of the environment in terms of ongoing global warming, Dasgupta’s research explores how Earth’s environment has evolved over billions of years. Where we may view the evolution of life as a progression from apes to humans, Dasgupta traces how the planet’s formation shapes planetary habitability and the appearance of elements necessary for life.
These elements — carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur — make up many familiar gases in Earth’s atmosphere, such as carbon dioxide, methane and water vapor. Today, their existence may seem trivial, but from a scientific perspective, it remains unclear: How did they get here? What processes allowed these elements to emerge in such perfect, life-sustaining proportions? Dasgupta’s lab investigates which planetary processes, internal compositions of rocks and minerals, and thermal structures made Earth “just right for life to emerge and flourish.”
Taking this a step further, he also investigates how these processes differ between planets and how those differences resulted in some planets being habitable and others uninhabitable. “For example,” Dasgupta explained, “If you go to Mars, maybe it was habitable on the surface early on. It had liquid water and so on, and now it’s no longer. So, why is that? What type of interior processes may have influenced our planet to remain habitable, keeping the balance of life essential gases and elemental abundance at the surface, whereas Mars did not manage to maintain it?”
Dasgupta studies the environment on a similarly vast, billion-year scale. While many of us are familiar with the human contribution of greenhouse gases to the environment, it’s less widely known that these gases would naturally cycle through the atmosphere over long periods of time, even without human influence. Investigating inner planetary processes allows Dasgupta to make predictions about the fluctuations in greenhouse gas levels throughout Earth’s history.
Studying these processes without direct access to Earth’s interior is no easy task. To overcome this challenge, Dasgupta’s lab uses specialized equipment to simulate the extreme heat and pressure found deep within the planet. Their devices heat rock or other materials while subjecting them to several gigapascals of pressure. Since pressure is determined by force divided by area, and lab devices can only exert so much force, Dasgupta is limited to working with small samples to achieve the highest possible pressures.
His lab can simulate conditions ranging from 0.1 gigapascals — similar to those in crustal magma chambers — to over 15 gigapascals, found 500 kilometers beneath the surface. As Dasgupta puts it, his work is “so, so foundational and fascinating at the same time, because this is the only way to get to some material property or chemistry of planets’ interiors that we will otherwise have no access to, probably ever.” From specks of dust and a few machines, he uncovers insights that would otherwise remain undiscovered.
Dasgupta’s research focuses on the deep carbon cycle — the slow, long-term movement of carbon through Earth’s mantle and core. Carbon is transported into the planet’s interior through subduction, where tectonic plates sink into the mantle, and is later released through magma formation and volcanic eruptions. These processes drive the exchange of carbon between different reservoirs, including the oceans, atmosphere and Earth’s crust.
In 2010, Dasgupta set the foundation for a new way of thinking about the carbon cycle. Until then, geoscientists had largely examined surface-level carbon processes and deep-Earth carbon processes separately. Dasgupta turned that way of thinking around. In a synthesis paper, he brought these perspectives together, proposing a framework that connected mantle melting, subduction and outgassing to the long-term movement of carbon through the planet. His work also identified which forms of stored carbon are more or less likely to be extracted through geological processes. As Chenguang Sun, an assistant professor at UT Austin’s Jackson School of Geoscience and a former postdoc in Dasgupta’s group, put it, “Raj has done fundamental work to establish the foundation for understanding mantle melting in the presence of carbon.” This framework has since shaped geoscience research worldwide.
Dasgupta’s path to this breakthrough began years earlier, while he was a student in India. During his master’s and Ph.D. studies, he grew interested in magmatic differentiation — the process by which rock melts and resurfaces as lava. His experiments in this area led to his first insights into the role of carbon in Earth’s interior and mantle melting, and eventually drew his focus to how carbon is stored in different reservoirs. “Although I started with just one very specific aspect of the carbon cycle — carbon and mantle melting,” he said, “that led me to understand these deeper connections between many different processes and how they influence storage and exchange of carbon in various planet-scale processes.”
This seed of passion eventually led Dasgupta to Rice, where he joined the faculty in 2008 and founded his lab the following year. The rest is history. With the help of his research team, he has built a lab that produces foundational, globally influential research.
Dasgupta has built on his framework in myriad ways, integrating new perspectives and data. His research operates in two key ways: It either generates predictions about planetary processes or works with existing findings to better explain natural phenomena.
The first, predictive approach is crucial when direct observation is impossible. Given that much of his work focuses on Earth’s deep interior, direct sampling is a challenge. “It’s much more difficult to drill into our own planet and study samples directly than it is to send a spacecraft to a faraway planet,” Dasgupta explained. Instead, he relies on experimental data to infer what lies beneath.
For example, while we cannot directly probe the mantle or core to determine their exact elemental composition, Dasgupta’s work helps predict them. As we know, our planet consists of distinct layers — a metallic core and silicate outer layers — but it wasn’t always this way. During Earth’s formation, metals and silicates were intermixed until heat and pressure drove denser, molten metals to the center, creating the layered structure we see today. Dasgupta’s lab studies how elements like carbon and nitrogen behave in molten metals and silicates under extreme conditions. By understanding these processes, he can model how elements were distributed between Earth’s core and mantle during planetary formation.
Dasgupta’s research has implications beyond Earth. While his earlier work focused on carbon cycling, a more recent project asks a deeper question: How did that carbon get here in the first place? Over the past decade, he has examined the processes that initially introduced carbon into Earth’s interior. By applying these findings to other rocky bodies, his group explores how planetary conditions might influence carbon distribution elsewhere. “If you go to Mars, the moon or Mercury,” Dasgupta said, “we think about how the variables are potentially different and how they may have influenced the establishment of carbon and other essential elements.” In doing so, their findings from specks of dust can be extended to planets across the universe.
The second research approach — where experiments refine our understanding of existing natural samples — also plays a critical role in Dasgupta’s work. “Using the experiments alone, we will not be saying something interesting,” Dasgupta noted. “We say something very interesting by comparing our experimental results with natural data or natural observations.”
A prime example is his lab’s study of iron meteorites, which originate from planetesimals — the ancestors of today’s planets. Over time, many planetesimals broke apart, with fragments landing on Earth as meteorites. Since only pieces remain, their full composition is difficult to reconstruct. To fill in the gaps, Dasgupta’s team has conducted experiments exploring how elements distribute as molten iron cools and solidifies, uncovering the processes planetesimals would have undergone as they formed. This “marriage” of existing natural data and experimental results allows the team to infer the original composition of these ancient planetesimals. The same process can be applied to better understand the evolution of planets, including Mars.
Applying laboratory findings to real-world systems is one of Dasgupta’s greatest challenges. It is not enough to observe certain properties in the lab: The real test is determining their broader significance. “My scientific community will always ask for more,” he said. “How do we apply these properties to say something meaningful or potentially path-breaking about one of the natural systems we are trying to understand?”
One example is determining Earth’s carbon budget, a problem his lab has worked on for over a decade. Despite years of work, there is neither a clear-cut answer nor consensus in the geoscience community. “It’s still not fully agreed upon,” Dasgupta said. “It depends on who you ask.” His work is a reminder that science is an ongoing process, always evolving as new data emerges.
During his time at Rice, Dasgupta has set milestones for the School of Natural Sciences, pioneering deep-carbon-cycle research and mentoring the next generation of scientists. But his greatest source of pride is what often remains hidden: the people he works with and the creativity, collaboration and warmth fostered in his lab. Over the past 15 years, he has mentored a diverse group of students who have not only shaped their own careers but have also challenged and inspired him. “I have been a part of their careers and their educational experiences, and they have allowed me to be a part of their journey,” he reflected. “The cases where we have made the most progress are where they have challenged me. I have learned so much from them.”
Dasgupta’s dedication to building a supportive research community has left a lasting impression. Sun, who worked with him from 2016-2020, recalled weekly lab meetings where students could openly discuss science in a welcoming environment. “Raj nurtured a very friendly, collaborative environment,” Sun said. “It was a unique experience that I haven’t seen in many other places.” He looks back on his time at Rice fondly, crediting Dasgupta as a pivotal mentor in his geoscience career.
Ultimately, Dasgupta is most proud of the legacy he has built through his students. “Many of them are now leading researchers in our field,” he said. “That gives me the greatest satisfaction.” After a pause, he added, “You know, they are my legacy.”
Dasgupta’s ability to produce groundbreaking research while fostering a strong lab community underscores his belief that “science doesn’t get done without people.” Though he remains an active researcher, his legacy is already clear — not only in his scientific contributions but in the culture of mentorship and curiosity he has cultivated. His work continues to shape the future of geochemistry, inspiring new generations to explore the unknown and embrace the thrill of scientific discovery.
— Sasha Miller ’28
This work was made possible with support from the Fondren Fellows program.