Deep thought at Rice
Geochemist Rajdeep Dasgupta wins prestigious F.W. Clarke Medal

BY MIKE WILLIAMS
Rice News staff

It may not be realistic to think of space as the final frontier. Rajdeep Dasgupta believes that to be in the opposite direction.

“It’s easier to send a spacecraft to Mars than to drill 100 or 200 kilometers deep inside the planet,” said Dasgupta, a Rice University assistant professor of Earth science. “The interior of the planet is in some ways harder to access than the far reaches of the galaxy.”

	RAJDEEP DASGUPTA

Dasgupta’s eagerness to take on just such a challenge has earned him this year’s F.W. Clarke Medal, an honor given since 1972 to an “early career scientist for a single outstanding contribution to geochemistry or cosmochemistry, published either as a single paper or a series of papers on a single topic.”

The Geochemical Society will present the award to Dasgupta at its annual conference in Prague in August.

Dasgupta, who joined Rice in 2008, is the second in the department to win the prestigious honor in recent years. His colleague, Cin-Ty Lee, earned the honor in 2009. The award is named after Frank Wigglesworth Clarke, considered the father of geochemistry for having determined the composition of Earth’s crust.

Dasgupta is looking deep beneath that crust for evidence of carbon and hydrogen and how those basic elements are exchanged between the planet’s interior and the atmosphere.

“The basic question is, How much of carbon or hydrogen — or any other fluid species that we see abundantly on the surface of the planet — is present in the interior?” he said. “And what kind of feedback exists between the rock reservoirs in the interior and the surface environment?”

Dasgupta has studied long-term planetary cycles that see carbon, in particular, expelled from the interior through volcanic activity, reabsorbed by the crust and eventually sent back to the mantle. “The thing of interest is how the long-term cyclicity of these volatile species modulated the planet,” he said. “How do we store carbon and hydrogen in the interior of the planet?”

Lately, Dasgupta has been going deep for answers.

“It turns out that the amount of carbon we are dealing with on the surface is actually a small fraction of the total planetary budget,” he said. “We probably have way more carbon in the core and the mantle combined — several factors more — than what we have on the surface.

“So the questions become, what’s the timescale of exchange within those interior reserves and the surface and how do the rock and mineral properties in the interior influence such exchange? It would be tremendously problematic if the interior budget is so much bigger and within, let’s say, 1,000 years or 10,000 years, some of that was quickly released to the atmosphere, as if you were popping the cap of a champagne bottle.”

Researchers can’t dig 100 kilometers into the Earth. “But this field we call experimental petrology, or high-pressure mineral physics, gives us that ability,” he said. “We create conditions that are extreme and relevant many kilometers inside the planet, because we can’t send a robot or rover down there.”

The primary gears in Dasgupta’s lab are a couple of hydraulic presses that simulate the pressures rocks and minerals experience up to 100 kilometers deep. In a way, it’s a time machine that speeds up the process of how rocks respond to such pressures and what happens to the elements, including carbon, inside.

Later this year, through the Packard Fellowship for Science and Engineering he earned last year, Dasgupta will add a multi-anvil press to his lab. It will allow him to simulate conditions as deep as 1,000 kilometers. He also hopes to add a Raman spectroscope to his arsenal of analytical tools.

“The main thing for me at Rice is to keep building the list of topics on deep Earth processes we’re working on, and building the group of students who will solve many of the fundamental questions in natural sciences of our time. I’m only doing a fraction of it.

“The Clarke Medal is a nice recognition,” Dasgupta said. “Awards are transient — they don’t change anything about the research, really. We’ll keep doing what we do. But I hope it’s motivational for young students and postdoctoral researchers in my group and in my department to see that if you work hard and are passionate about your research, there are accolades from the community along the way.”