"What mammalian species would be most suited to live on a teraformed Mars. Primarily as a source of protein for humans"
-
A Multi-Proxy Search for Atmospheric Oxygen in the 2.9 Ga Pongola Supergroup, Southern Africa
PI: Ono, Shuhei
The evolution of oxygenic photosynthesis impacted the early Earth’s atmosphere and climate, and left us geochemical signatures in the rock records. We will test our hypothesis that biological oxygenic photosynthesis emerged as early as ~2.9 Ga and is responsible for triggering the 2.9 Ga glaciations by destabilizing a methane-rich greenhouse atmosphere. We will focus on the rocks of the ~2.9 Ga Pongola Supergroup in Southern Africa because they are minimally altered and contain the oldest known record of glaciations, stromatolites with diverse morphologies, and a series of banded iron formations and carbonaceous shales. Previous research by us and others reported relatively small signatures of sulfur-mass-independent fractionation (S-MIF) and distinct negative cerium anomalies from the rocks between 2.76 and 2.92 Ga, pointing to an early oxygenation at this age.
Our principle tool is high precision analysis of all four sulfur isotopes ( 32 S, 33 S, 34 S and 36 S) of sulfide minerals. The S-MIF in Archean rocks is a direct proxy for atmospheric chemistry that is particularly sensitive to the atmospheric oxygen as low as a few ppm levels. We will compare not only the magnitude of S-MIF signatures (Δ33S) but also the relationship among δ34S, Δ33S, and δ36S values in the stratigraphic interval containing glacial records to test if S-MIF records a change in atmospheric chemistry before and after the glacial events. Cerium anomaly in carbonates and banded iron formations, if present, will provide a supporting evidence for water column oxygen. Small-scale (mm- to cm) analysis of multiple-sulfur isotope system, in combination with carbon isotope ratios of organic carbon, will provide new insights about the evolution of early microbial sulfur metabolisms.
The fund requested will support one graduate student at EAPS-MIT. The proposed research is designed to contribute to the research emphasis of the Exobiology Program: early evolution of life and the biosphere.
