Abstract
Abstract In the study of planetary habitability and terrestrial atmospheric evolution, the divergence of surface conditions for Venus and Earth remains an area of active research. Among the intrinsic and external influences on the Venusian climate history are orbital changes due to giant planet migration that have both variable incident flux and tidal heating consequences. Here, we present the results of a study that explores the effect of Jupiter’s location on the orbital parameters of Venus and subsequent potential water-loss scenarios. Our dynamical simulations show that various scenarios of Jovian migration could have resulted in orbital eccentricities for Venus as high as 0.31. We quantify the implications of the increased eccentricity, including tidal energy, surface energy flux, and the variable insolation flux expected from the faint young Sun. The tidal circularization timescale calculations demonstrate that a relatively high tidal dissipation factor is required to reduce the eccentricity of Venus to the present value, which implies a high initial water inventory. We further estimate the consequences of high orbital eccentricity on water loss, and estimate that the water-loss rate may have increased by at least ∼5% compared with the circular orbit case as a result of orbital forcing. We argue that these eccentricity variations for the young Venus may have accelerated the atmospheric evolution of Venus toward the inevitable collapse of the atmosphere into a runaway greenhouse state. The presence of giant planets in exoplanetary systems may likewise increase the expected rate of Venus analogs in those systems.
Highlights
The current state of the Venusian atmosphere and the pathway through which it arrived there is an exceptionally complicated topic
Some models suggest that Venus may have had temperate surface conditions that allowed the persistence of surface liquid water until as recently as ∼0.7 Ga (Way et al 2016), depending upon assumptions regarding rotation rates and convection schemes (e.g., Leconte et al 2013; Ramirez 2018)
We explored the circularization of the Venus orbit by performing a suite of simulations considering three different scenarios within the solar system: (1) initial Venusian orbital eccentricity excited to 0.31 but with no tidal forces; (2) initial Venusian orbital eccentricity excited to 0.31 and 0.1 × k2,ÅDtÅ; and (3) initial Venusian socrebnitaarlioec(c3e)nttirdicailtydiesxsicpitaetdiontoo0f .32100a ×nd k22,0Å0D ×tÅ ki2s,ÅuDntrÅea.liTsthice but accelerates the circularization process and allows us to explore the possible timescale of circularization due to the effects of tides
Summary
The current state of the Venusian atmosphere and the pathway through which it arrived there is an exceptionally complicated topic. Some models suggest that Venus may have had temperate surface conditions that allowed the persistence of surface liquid water until as recently as ∼0.7 Ga (Way et al 2016), depending upon assumptions regarding rotation rates and convection schemes (e.g., Leconte et al 2013; Ramirez 2018). Such potential for past Venusian surface habitability has been the basis for defining the empirically derived inner edge of the “Habitable Zone”
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