Carbon is one of the essential building blocks of life on Earth, and it—along with hydrogen, nitrogen and oxygen—is one of the key elements researchers look for when they search for habitable planets and work to understand how—and why—those planets are formed. But much of the Earth’s core is opaque to humans, who have never accessed it directly, muddling much of our understanding of the planet’s composition. Now, researchers from Florida State University (FSU) and Rice University have applied supercomputing power to provide a more accurate estimate of the carbon contained in the Earth’s outer core.
“Understanding the composition of the Earth’s core is one of the key problems in the solid-earth sciences,” said Mainak Mookherjee, co-author of the paper describing the research and an associate professor of geology at FSU, in an interview with Kimberly Mann Bruch of the San Diego Supercomputer Center (SDSC) and Bill Wellock of FSU. “We know the planet’s core is largely iron, but the density of iron is greater than that of the core. There must be lighter elements in the core that reduce its density. Carbon is one consideration, and we are providing better constraints as to how much might be there.”
To estimate the composition of the Earth’s outer core, this new research took the previously known characteristics of sound waves traveling through the planet and compared that data with data generated from simulations of the same experiment under various different planetary compositions using first-principles molecular dynamics (FPMD).
FPMD, however, has a high computational cost for experiments like this—and for that, the researchers turned to three supercomputers, both accessed through allocations from the Extreme Science and Engineering Discovery Environment (XSEDE). The systems were SDSC’s Expanse supercomputer (2.48 Linpack petaflops); the Bridges-2 system at the Pittsburgh Supercomputing Center; and the Stampede2 system at the Texas Advanced Computing Center (10.7 Linpack petaflops).
The result: an estimate of anywhere between 5.5 and 36.8 quintillion metric tons of carbon—or between 0.3 and 2.0 percent of the Earth’s outer core by weight. “Though the percentage of carbon of the Earth’s outer core is low, it’s still an enormous amount because the area is so large,” said Suraj Bajgain, lead author of the paper and a postdoctoral researcher in earth sciences at FSU.
“Our work would not be feasible without using the computing allocations from XSEDE,” Bajgain added. “In the next steps for our studies, we will use Expanse to explore the effect of multiple light elements—not just carbon—to refine our work.”