The early Earth as an analogue for exoplanetary biogeochemistry
arxiv(2024)
摘要
Planet Earth has evolved from an entirely anoxic planet with possibly a
different tectonic regime to the oxygenated world with horizontal plate
tectonics that we know today. For most of this time, Earth has been inhabited
by a purely microbial biosphere albeit with seemingly increasing complexity
over time. A rich record of this geobiological evolution over most of Earth's
history provides insights into the remote detectability of microbial life under
a variety of planetary conditions. We leverage Earth's geobiological record
with the aim of a) illustrating the current state of knowledge and key
knowledge gaps about the early Earth as a reference point in exoplanet science
research; b) compiling biotic and abiotic mechanisms that controlled the
evolution of the atmosphere over time; and c) reviewing current constraints on
the detectability of Earth's early biosphere with state-of-the-art telescope
technology. We highlight that life may have originated on a planet with a
different tectonic regime and strong hydrothermal activity, and under these
conditions, biogenic CH_4 gas was perhaps the most detectable atmospheric
biosignature. Oxygenic photosynthesis, which is responsible for essentially all
O_2 gas in the modern atmosphere, appears to have emerged concurrently with
the establishment of modern plate tectonics and the continental crust, but
O_2 accumulation to modern levels only occurred late in Earth's history,
perhaps tied to the rise of land plants. Nutrient limitation in anoxic oceans,
promoted by hydrothermal Fe = fluxes, may have limited biological productivity
and O_2 production. N_2O is an alternative biosignature that was perhaps
significant on the redox-stratified Proterozoic Earth. We conclude that the
detectability of atmospheric biosignatures on Earth was not only dependent on
biological evolution but also strongly controlled by the evolving tectonic
context.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要