Abstract
Ancient Venus and Earth may have been similar in crucial ways for the development of life, such as liquid water oceans, land-ocean interfaces, favorable chemical ingredients, and energy pathways. If life ever developed on, or was transported to, early Venus from elsewhere, it might have thrived, expanded, and then survived the changes that have led to an inhospitable surface on Venus today. The Venus cloud layer may provide a refugium for extant life that persisted from an earlier more habitable surface environment. We introduce the Venus Life Equation (VLE)-a theory and evidence-based approach to calculate the probability of extant life on Venus, L, using three primary factors of life: Origination, Robustness, and Continuity, or L = O · R · C. We evaluate each of these factors using our current understanding of Earth and Venus environmental conditions from the Archean to the present. We find that the probability of origination of life on Venus would be similar to that of Earth, and argue that the other factors should be nonzero, comparable with other promising astrobiological targets in the solar system. The VLE also identifies poorly understood aspects of Venus that can be addressed by direct observations with future exploration missions.
Highlights
We introduce the Venus Life Equation (VLE)—a theory and evidence-based approach to calculate the probability of extant life on Venus, L, using three primary factors of life: Origination, Robustness, and Continuity, or L = O
We find that the probability of origination of life on Venus would be similar to that of Earth, and argue that the other factors should be nonzero, comparable with other promising astrobiological targets in the solar system
One of the biggest motivators for exploring the solar system beyond Earth is to determine whether extant life currently exists, or now-extinct life once existed, on worlds beyond ours
Summary
One of the biggest motivators for exploring the solar system beyond Earth is to determine whether extant life currently exists, or now-extinct life once existed, on worlds beyond ours. This article approaches the question of extant life on Venus in a similar manner to the strategy of the Drake Equation established for estimating probabilities of extraterrestrial intelligent life (Drake, 1965; Burchell, 2006). We approach the question of whether life exists currently ‘‘on’’ Venus (we include the planet’s atmosphere in this definition) as an exercise in informal probability—seeking the qualitative likelihood (i.e., not the statistical likelihood function) of the answer being nonzero. The fundamental goal of the Venus Life Equation (VLE) is to provide a scaffolding for estimating the chance of extant life based on factors that can be constrained or quantified through observation, experiment, and data-based modeling.
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