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Venus; Atmosphere; Coupled evolution; Feedback cycles; Volatile exchanges
Abstract:
This work reviews the long-term evolution of the atmosphere of Venus, and modulation of
its composition by interior/exterior cycling. The formation and evolution of Venus’s atmo-
sphere, leading to contemporary surface conditions, remain hotly debated topics, and in-
volve questions that tie into many disciplines. We explore these various inter-related mech-
anisms which shaped the evolution of the atmosphere, starting with the volatile sources and
sinks. Going from the deep interior to the top of the atmosphere, we describe volcanic out-
gassing, surface-atmosphere interactions, and atmosphere escape. Furthermore, we address
more complex aspects of the history of Venus, including the role of Late Accretion im-
pacts, how magnetic field generation is tied into long-term evolution, and the implications
of geochemical and geodynamical feedback cycles for atmospheric evolution. We highlight
plausible end-member evolutionary pathways that Venus could have followed, from accre-
tion to its present-day state, based on modeling and observations. In a first scenario, the
planet was desiccated by atmospheric escape during the magma ocean phase. In a second
scenario, Venus could have harbored surface liquid water for long periods of time, until its
temperate climate was destabilized and it entered a runaway greenhouse phase. In a third
scenario, Venus’s inefficient outgassing could have kept water inside the planet, where hy-
drogen was trapped in the core and the mantle was oxidized. We discuss existing evidence
and future observations/missions required to refine our understanding of the planet’s history
and of the complex feedback cycles between the interior, surface, and atmosphere that have
been operating in the past, present or future of Venus.
