Obliquity Variability of a Potentially Habitable Early Venus

Barnes, Jason W.; Quarles, Billy; Lissauer, Jack J.; Chambers, John E.; Hedman, M. M.

doi:10.1089/ast.2015.1427

Cited by 20 publications

(30 citation statements)

References 32 publications

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“…New work by Barnes et al . [] has shown that if Venus started with its current obliquity near 180°, it is likely to have remained so throughout its existence. How it would have obtained its initial ~180° obliquity is still debated.…”

Section: Introductionmentioning

confidence: 99%

“…Other work has shown that approaching a tidally locked or nearly tidally locked state like that of modern Venus may be a natural consequence of planetary tidal-bulge/Sun interaction (R. Barnes, Tidal Locking of Habitable Exoplanets, submitted to Celestial Mechanics and Dynamical Astronomy, 2016), with important climate implications [Yang et al, 2014]. New work by Barnes et al [2016] has shown that if Venus started with its current obliquity near 180°, it is likely to have remained so throughout its existence. How it would have obtained its initial~180°obliquity is still debated.…”

Section: Introductionmentioning

confidence: 99%

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Was Venus the first habitable world of our solar system?

Way

Genio

Kiang

et al. 2016

Geophysical Research Letters

277

276

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Present‐day Venus is an inhospitable place with surface temperatures approaching 750 K and an atmosphere 90 times as thick as Earth's. Billions of years ago the picture may have been very different. We have created a suite of 3‐D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 Gya, present‐day Venus orbital parameters, an ocean volume consistent with current theory, and an atmospheric composition estimated for early Venus. Using these parameters we find that such a world could have had moderate temperatures if Venus had a prograde rotation period slower than ~16 Earth days, despite an incident solar flux 46–70% higher than Earth receives. At its current rotation period, Venus's climate could have remained habitable until at least 0.715 Gya. These results demonstrate the role rotation and topography play in understanding the climatic history of Venus‐like exoplanets discovered in the present epoch.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Was Venus the first habitable world of our solar system?

Way

Genio

Kiang

et al. 2016

Geophysical Research Letters

277

276

View full text Add to dashboard Cite

show abstract

“…Later, Lissauer et al (2012) explored the obliquity variations of a moonless Earth and found in agreement, that the retrograde-rotating Earths were generally more obliquity stable. Barnes et al (2016) then explored the case of an early Venus and again reported similar results, with the exception of a long-term pronounced variability for some retrograde rotators. Quarles et al (2019) found that depending on the mutual inclination and orbital precession of the bodies, retrograde rotators in the α Centauri AB binary-star system would likely be especially obliquity stable.…”

Section: Introductionmentioning

confidence: 68%

Retrograde-rotating Exoplanets Experience Obliquity Excitations in an Eccentricity-enabled Resonance

et al. 2020

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Previous studies have shown that planets that rotate retrograde (backwards with respect to their orbital motion) generally experience less severe obliquity variations than those that rotate prograde (the same direction as their orbital motion). Here we examine retrograde-rotating planets on eccentric orbits and find a previously unknown secular spin-orbit resonance that can drive significant obliquity variations. This resonance occurs when the frequency of the planet's rotation axis precession becomes commensurate with an orbital eigenfrequency of the planetary system. The planet's eccentricity enables a participating orbital frequency through an interaction in which the apsidal precession of the planet's orbit causes a cyclic nutation of the planet's orbital angular momentum vector. The resulting orbital frequency follows the relationship f = 2˙ −Ω, where˙ andΩ are the rates of the planet's changing longitude of periapsis and ascending node, respectively. We test this mechanism by simulating cases of a simple Earth-Jupiter system, and confirm the predicted resonance. Over the course of 100 Myr, the test Earths with rotation axis precession rates near the predicted resonant frequency experienced pronounced obliquity variations of order 10 • -30 • . These variations can be significant, and suggest that while retrograde rotation is a stabilizing influence most of the time, retrograde rotators can experience large obliquity variations if they are on eccentric orbits and enter this spin-orbit resonance.

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“…For the Earth, the obliquity is stabilized by the Earth's moon Li & Batygin 2014), without which the obliquity variations would likely have been much more extreme . Additional simulations for a retrograde-rotating Venus by Barnes et al (2016) indicate that obliquity variations may have been as low as ±7…”

Section: Implications For Habitabilitymentioning

confidence: 99%

Obliquity and Eccentricity Constraints for Terrestrial Exoplanets

Kane

Torres

2017

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Exoplanet discoveries over recent years have shown that terrestrial planets are exceptionally common. Many of these planets are in compact systems that result in complex orbital dynamics. A key step toward determining the surface conditions of these planets is understanding the latitudinally dependent flux incident at the top of the atmosphere as a function of orbital phase. The two main properties of a planet that influence the time-dependent nature of the flux are the obliquity and orbital eccentricity of the planet. We derive the criterion for which the flux variation due to obliquity is equivalent to the flux variation due to orbital eccentricity. This equivalence is computed for both the maximum and average flux scenarios, the latter of which includes the effects of the diurnal cycle. We apply these calculations to four known multi-planet systems (GJ 163, K2-3, Kepler-186, and Proxima Centauri), where we constrain the eccentricity of terrestrial planets using orbital dynamics considerations and model the effect of obliquity on incident flux. We discuss the implications of these simulations on climate models for terrestrial planets and outline detectable signatures of planetary obliquity.

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Obliquity Variability of a Potentially Habitable Early Venus

Cited by 20 publications

References 32 publications

Was Venus the first habitable world of our solar system?

Was Venus the first habitable world of our solar system?

Retrograde-rotating Exoplanets Experience Obliquity Excitations in an Eccentricity-enabled Resonance

Obliquity and Eccentricity Constraints for Terrestrial Exoplanets

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