Geologists from the University of Heidelberg studied very old and rare samples of the mineral zircon,
Zircon mineral grains are formedfrom magma (molten rock), in a very hot and initially hostile environment. However, millions of years ago, the heated remains of organisms turned into carbon dioxide and methane gases. And then —were deposited as graphite in the mineral zircon at approximately 700 °C.
"The distinctive isotopic signature of biogenic carbonleaves behind a kind of fingerprint of earlier life forms,” explains Dr. Manfred Vogt from the Institute of Earth Sciences at Heidelberg University, lead author of the study.
Taking measurements requires a lot of effort,researchers emphasize. In zircon crystals, it is necessary to identify intact graphite inclusions, some of which are only a few micrometers in size (one millionth of a meter, or a hundred times thinner than a human hair). To eliminate carbon contamination from the environment, scientists are using non-destructive Raman microspectroscopy to study encapsulated inclusions in zircons. The zircons are then bombarded with an ion beam to expose the graphite inclusions. Their carbon isotope composition can then be analyzed.
The results of the study were published in the journal Geochimica et Cosmochimica Acta.
Zircons are among the oldestminerals on Earth, some of them are older than four billion years. “They can tell us about more than 96% of the Earth’s history,” the scientists conclude.
Read more:
A red halo flared up over Italy. Now its nature has been explained
Named a way to reduce appetite without surgery
Chia seed experiment confirms Alan Turing's famous mathematical model
On the cover: an open graphite inclusion in zircon after ion bombardment, image obtained using a scanning electron microscope
Image Credit & Copyright: Winfried Schwartz, Heidelberg University Institute for Geosciences