Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon
Abstract
Venus possesses no natural satellite, raising the question of whether a formed moon could have survived. We explore the tidal evolution of a Venus-moon system, coupling Venus’s spin to the satellite’s orbit under tides from the moon and Sun. We survey spin period ( P 0 = 5–100 hr), moon mass ( M m = 0.01–10 M Moon ), eccentricity, quality factor, and initial semimajor axis under both constant- Q and constant time lag models. Survival depends on competition between outward migration (∝ M m ) and synchronous radius expansion ( ∝ M m 2 ): for circular orbits around a rapidly spinning Venus ( P 0 ≲ 12 hr), a lunar-mass satellite survives the age of the solar system in both models. For P 0 ≲ 10 hr, eccentricity pumping can destabilize low-mass satellites, while for P 0 ≳ 15 hr or M m ≳ 2 M Moon , the synchronous radius overtakes the orbit and drives Roche destruction within ∼0.03–1.7 Gyr in the constant- Q model. The constant time lag model instead permits quasi-synchronous survival for massive moons at fast spin. Explaining Venus’s present state requires satisfying two constraints simultaneously: loss of the satellite and despinning of an initially rapid rotator. Both are met only within a restricted region of parameter space, favoring moderate postimpact spin periods and lunar-to-super-lunar masses. Giant impact simulations predict spin periods ≳12 hr for Venus’s present rotation, placing a lunar-mass satellite at the survival boundary. For last-impact conditions within this region, the present absence of a Venusian satellite arises through tidal evolution alone; a subsequent catastrophic stripping event, while capable of removing a moon, is not required.
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BibTeX
@article{kane2026tidal,
title = {{Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon}},
author = {Stephen Kane and Franck Selsis and Jérémy Leconte and Sean N. Raymond},
journal = {The Astrophysical Journal},
year = {2026},
month = sep,
doi = {10.3847/1538-4357/ae9d6c},
eprint = {2608.25036},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05760817v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon
AU - Stephen Kane
AU - Franck Selsis
AU - Jérémy Leconte
AU - Sean N. Raymond
PY - 2026
DA - 2026/09/14
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae9d6c
UR - https://hal.science/hal-05760817v1
AB - Venus possesses no natural satellite, raising the question of whether a formed moon could have survived. We explore the tidal evolution of a Venus-moon system, coupling Venus’s spin to the satellite’s orbit under tides from the moon and Sun. We survey spin period ( P 0 = 5–100 hr), moon mass ( M m = 0.01–10 M Moon ), eccentricity, quality factor, and initial semimajor axis under both constant- Q and constant time lag models. Survival depends on competition between outward migration (∝ M m ) and synchronous radius expansion ( ∝ M m 2 ): for circular orbits around a rapidly spinning Venus ( P 0 ≲ 12 hr), a lunar-mass satellite survives the age of the solar system in both models. For P 0 ≲ 10 hr, eccentricity pumping can destabilize low-mass satellites, while for P 0 ≳ 15 hr or M m ≳ 2 M Moon , the synchronous radius overtakes the orbit and drives Roche destruction within ∼0.03–1.7 Gyr in the constant- Q model. The constant time lag model instead permits quasi-synchronous survival for massive moons at fast spin. Explaining Venus’s present state requires satisfying two constraints simultaneously: loss of the satellite and despinning of an initially rapid rotator. Both are met only within a restricted region of parameter space, favoring moderate postimpact spin periods and lunar-to-super-lunar masses. Giant impact simulations predict spin periods ≳12 hr for Venus’s present rotation, placing a lunar-mass satellite at the survival boundary. For last-impact conditions within this region, the present absence of a Venusian satellite arises through tidal evolution alone; a subsequent catastrophic stripping event, while capable of removing a moon, is not required.
SN - 0004-637X
SN - 1538-4357
ER -