Preservation of Impact Evidence in the Sedimentary Record: Erosion of the Vredefort and Sudbury Craters as a Guide to Identifying Hadean Impacts

University Of Puerto Rico Mayaguez, Mayaguez PR

Investigators

Abstract

Little is known about how the young Earth transitioned from a planetary inferno at 4.5 billion years ago to a water-covered, life-supporting world by 3.8 billion years ago. This project involves the study large impact craters in South Africa and Canada to understand how evidence of giant, continental-scale meteorite impacts is preserved in the geologic record after the craters erode. This study will provide insights into planetary evolution, including the earliest stages of Earth history that ultimately led to the development of environments capable of supporting life. Prevailing geologic models suggest that the Hadean Earth was an utterly alien world compared to today. It is envisioned as a fiery planet covered in oceans of hot magma and subject to intense meteorite bombardments that created hostile surface environments. In contrast, isotopic evidence from ancient zircon (ZrSiO4) crystals up to 4.2 billion years old suggests that the Earth may have been much cooler, enough to allow liquid water to stabilize and provide habitats for the rise of life. Preserved materials from this time period are rare; direct evidence of early meteorite impacts is preserved on the Moon, but has not been found on Earth. This project seeks to establish new techniques for recognizing how to identify evidence of large impact craters long after they are eroded and reduced to sediments. To accomplish this, deformed minerals in sediments from the partially eroded Vredefort (South Africa) and Sudbury (Canada) impact craters will be studied. The results will be applied to the search for impact evidence from the Hadean Earth. The results of this project will also provide insight during analysis of materials from future sample return missions to both the Moon and Mars, where early planetary crusts are preserved.