Venus could have lost a natural moon through tidal evolution alone, according to a modeling analysis, but the result appears only in a narrow part of the scenarios tested. The study asks whether a satellite formed around Venus could have survived to the present. In the model, the cases that both removed the satellite and substantially slowed Venus’s spin occupied only a narrow region. For last-impact conditions within the modeled regime, the authors conclude that tides alone can account for Venus’s lack of a satellite, without requiring a later catastrophic stripping event.
The survival window is narrow
To reach that conclusion, the authors integrated coupled equations for Venus’s spin and the moon’s orbit, using adaptive fourth-order Runge-Kutta steps that resolved 1% fractional changes in spin and orbital distance. The calculation stopped when a trajectory crossed the Roche limit, exceeded the critical stability radius, or reached 4.5 billion years. The tested grid covered initial Venus spin periods from 5 to 100 hours, satellite masses from 0.01 to 10 lunar masses, starting orbits from 3.5 to 25 Venus radii, eccentricities from 0 to 0.5, and tidal quality factors, QV, from 10 to 100.
Spin sets the first boundary
At the fiducial configuration, the moon’s tidal torque on Venus was about 3 million times the solar tidal torque. Under the reported constant-Q cases, a 1-lunar-mass satellite survived the full 4.5-billion-year integration when Venus’s initial spin period was 12 hours or shorter. At 15 hours, the calculation found a synchronous reversal and destruction at about 0.97 billion years.
Different tidal models give different fates
The boundary shifted when the assumed tidal response changed. The study compares a constant-Q treatment with a constant-time-lag, or CTL, treatment, two different ways of representing the body’s tidal response. For a 2-lunar-mass satellite, constant-Q predicted Roche destruction after 1.7 billion years with an 8-hour initial spin and after 33 million years with a 12-hour spin. CTL predicted survival in those cases. At 5 lunar masses, constant-Q predicted destruction within about 100 million years at all tested spin periods, while CTL found a quasi-synchronous equilibrium for initial spins of 15 hours or less.
The assumed dissipation strength mattered even within the constant-Q framework. Setting QV to 100 extended modeled lifetimes by about a factor of two and moved the survival boundary toward higher satellite masses. Setting QV to 10 compressed lifetimes and shifted destruction toward lower masses. The calculation therefore gives no single survival time or mass threshold across the tested tidal assumptions.
Fast spin brings another hazard
In the model, initial spin periods shorter than about 10 hours brought eccentricity pumping, meaning the orbit’s oval shape grew rather than settled. Low-mass satellites were predicted to be destroyed even when their initial eccentricity was only 0.01. More massive moons could despin Venus below the pumping threshold before the eccentricity grew. Taken together, these cases leave only a narrow modeled region where moon loss and substantial Venus despinning occur at the same time.
Formation is still part of the puzzle
That narrow window must also be reconciled with how a moon might form. The paper reports that giant-impact scenarios consistent with Venus’s present rotation typically produced post-impact spin periods of at least 12 hours and debris disks inside the synchronous orbit, rather than a formed moon. The authors treat those impact results as indicative rather than definitive, but they create a tension between forming a satellite and its later tidal survival.
A useful check, with important caveats
As a check on the numerical setup, the authors integrated the Earth-Moon system. The calculation reproduced the reported lunar recession rate as 3.69 centimeters per year against an observed 3.82, a match within 3%. It produced a length-of-day increase of 2.05 milliseconds per century against an observed value of about 2.3, within 11%. The benchmark supports the calculation’s ability to reproduce those reported Earth-Moon rates, while Venus’s tidal response remains model-dependent.
Important omissions limit what can be inferred. The model includes gravitational body tides from the satellite and Sun but leaves out atmospheric thermal tides. The authors project that adding atmospheric tides would shorten modeled lifetimes and narrow the survival region. The true rocky-body rheology was not selected empirically, and lifetimes near the constant-Q torque reversal are sensitive to numerical resolution. The survival window is therefore a conditional model result, not a reconstruction of Venus’s history.
An example beyond Venus
The same calculation was extended only briefly to an exoplanet example. For a Venus analog at 0.1 astronomical units around a 0.3-solar-mass M dwarf, the reported critical spin period was about 10 times shorter than Venus’s. Under the paper’s stated interpretation, that would make moon survival effectively impossible for plausible post-impact spins. The authors present this as an example, not a comprehensive quantitative survey of Venus analogs.
The broad message is conditional. Within the modeled last-impact regime, tides alone are sufficient in the calculation to explain Venus’s present lack of a satellite, without requiring catastrophic stripping, but the outcome shifts with initial spin, satellite mass, eccentricity, dissipation and rheology. The manuscript is identified as arXiv:2608.25036v2, dated 2 September 2026.
Paper data and sources
Original title: Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon
Authors: Stephen R. Kane, Franck Selsis, Jeremy Leconte, Sean N. Raymond
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-25
DOI: Not available
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