The UCSD development is important because it now provides a window into some of these processes extending millions or billions of years into the Earth’s past. With the exception of the isotopic signatures of gases trapped in ice cores for the past 200,000 years, scientists have had little knowledge of how major components in the Earth’s ancient atmosphere-such as sulfur, carbon, and oxygen-cycled through the oceans and terrestrial rocks. 'And these signatures get transferred from ozone and other atmospheric oxidants to sulfate during the oxidation of reduced sulfur gases, such as those emitted by marine microorganisms or from volcanic eruptions.' 'We believe that ultimately these anomalous signatures come from the Earth’s atmosphere,' says Bao. The scientists knew the anomalous isotope signatures were terrestrial because they were recorded in sulfate (SO42-) minerals that had been deposited in volcanic ash beds 20 million years ago or, in the case of Namibian gypsum deposits, associated with sulfur-producing marine organisms that emitted dimethyl sulfide into the atmosphere during the past 10 million years. The study was financed by the National Aeronautics and Space Administration and the National Science Foundation. Campbell and Charles Chi-Woo Lee Klaus Heine of the University of Regensburg in Germany and David B. Also contributing to the discovery and analysis were UCSD chemists Thiemens, James Farquhar, Douglas A. 'Once we figure out the fundamental sulfur-oxidation processes occurring in the atmosphere, it will provide a good way to understand ancient atmospheric processes.'īao initially discovered the 'anomalous' signatures-something odd about variations of the three stable isotopes of oxygen-in gypsum deposits from the Namibian desert and in volcanic ash deposits in Nebraska and South Dakota. 'It opens up this whole new area for geochemists to look at things like ancient atmospheric deposits,' says Huiming Bao, a geochemist at UCSD and the first author of the paper. Thiemens, a professor of chemistry and dean of UCSD’s Division of Physical Sciences who headed the research effort. 'It will enable us to understand more about the history of the Earth and possibly climate on time scales that were out of reach before,' says Mark H. It will now give earth scientists and atmospheric chemists an important new probe to answer questions about the composition of Earth’s early atmosphere, the atmospheric processes of ancient volcanic eruptions, past ocean circulation patterns and early biological productivity.

Its discovery in terrestrial rocks in a form that showed it could be produced on Earth not only alters ideas among planetary scientists about the source of this anomaly. But the inability before now to detect this anomaly in terrestrial solids had forced scientists to conclude that it was unique to extraterrestrial sources and an exclusive byproduct of nucleosynthesis in stars.

Such signatures had been detected before in gases on Earth. The surprising finding, detailed in the July 13 issue of Nature, concludes a decade-long search in terrestrial rocks and sediments for this 'anomalous' oxygen-isotope signature.

Cplot so42 ucsd