Dr. John Valley and a team of scientists from a NASA Astrobiology Institute funded project at the University of Wisconsin-Madison using two different age-determining techniques have shown that a tiny zircon crystal found on a sheep ranch in western Australia is the oldest known piece of our planet, dating to 4.4 billion years ago. In a recent paper published in the journal Nature Geoscience, Valley and his team said the discovery indicates that Earth's crust formed relatively soon after the planet coalesced, leaving the zircon as one of the tiny surviving remnants. The results of their work shows that the Earth was not as harsh as scientists had previously thought.
Dr. John W. Valley - John Valley is the Charles R. Van Hise Professor at the University of Wisconsin-Madison's Department of Geoscience. He is also an investigator for the NASA Astrobiology Institute's (NAI) Wisconsin Astrobiology Research Consortium (WARC) where he is tasked with determining the surface conditions of the ancient Earth (up to 4.4. b.y. ago) through studies of the oldest terrestrial zircons using light stable isotopes such as Li and O; determining the genesis and biogenicity of proposed Archean microfossils and host cherts through O, C, S, and Si isotope studies; developing new insights into the fine-scale isotopic variability of ancient samples using the new Wisc-SIMS ion microprobe facility. His research interests span many fields in Earth Science. One interest concerns the igneous and metamorphic evolution of the crust during orogenesis with emphasis on the role of magmas, fluids, and thermobarometry. Another relates to sediments, diagenesis, and the rock record of past climate.