These two geochemists have one of the largest publishing networks in science
A ‘power couple’ in Earth and environmental sciences.
26 June 2020
Image of Larry Edwards by Layne Kennedy
Geochemists Larry Edwards and Hai Cheng want to reconstruct the last half a million years on Earth in more detail than ever before.
After a chance meeting at a lab party almost three decades ago, the pair have developed some of the most powerful dating techniques in their field.
While conventional radiocarbon dating can reach back 40,000 years, Edwards and Cheng’s approach to uranium-thorium dating can reconstruct the past 600,000 years.
Their improvements to uranium-thorium dating, which estimates the age of a rock based on how much uranium and thorium it contains, have enabled researchers to track the rise and fall of ancient civilizations, the forming and melting of ice sheets, and abrupt fluctuations in Earth’s climate.
“We see ourselves as the timekeepers of the last chapter of Earth’s history,” says Edwards.
A lasting impact
Edwards’ big-picture thinking and Cheng’s highly technical skillset set the pair up for early success.
As a graduate student at the California Institute of Technology in Pasadena during the late 1980s, Edwards developed new methods of measuring the rare isotopes, uranium and thorium, using mass spectrometry, a highly sensitive technique for determining the mass of atoms and molecules.
While this approach greatly increased the accuracy of uranium-thorium dating, Edwards wanted to use the next generation of mass spectrometers to make further improvements to his technique, such as increasing its time range and reducing the size of rock samples required.
In the 1990s, in his fledgling lab at the University of Minnesota, Edwards wanted a collaborator who could turn his ambitious ideas into viable research projects. Hai Cheng, who had been studying isotope geochemistry and mass spectrometry at Macquarie University in Sydney, Australia, had the practical skills needed to improve the accuracy of his technique.
So when Cheng showed up at a lab party in 1993 after moving to Minnesota to be with his family, Edwards “pretty much hired him on the spot.”
“He’s incredibly capable on all fronts,” says Edwards.
In 2019 alone, they co-authored 14 Earth and environmental sciences papers in Nature Index journals, which is more than any other research pair in their field.
Below is Edwards and Cheng’s co-authorship network in 2019 for Earth and environmental sciences papers published in Nature Index journals.
Zoom in and hover the mouse over the lines to view the number of co-publications between authors, as shown by link strength: