Venus may once have had a moon, but new simulations show that as the planet’s rotation slowed, tidal forces could have dragged the satellite inside the Roche limit and destroyed it—in some scenarios within just 30 million years.

Venus has no moon today, but that does not establish that it always travelled alone. A new modelling study asks whether an early satellite could have formed around the planet and then been lost as tides changed both the moon’s orbit and Venus’s rotation.

Stephen R. Kane, Franck Selsis, Jeremy Leconte and Sean N. Raymond explored that possibility in the 2026 preprint Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon. Their calculations coupled Venus’s changing spin to a satellite’s orbit, including tides from the moon and Sun.

This is one study, not settled consensus. It does not present observational evidence that Venus once possessed a moon. It tests whether tidal evolution could remove one without a later collision or close encounter.

A moon does not always move outward

Earth offers the familiar case. Because Earth rotates faster than the Moon travels around it, the tidal bulge raised on our planet pulls slightly ahead of the Moon. That transfers rotational energy into the lunar orbit, a process behind the Moon’s measured recession of about 3.8 centimetres a year.

The direction reverses for a satellite orbiting inside the planet’s synchronous radius, where one orbit takes less time than one planetary rotation. There the moon runs ahead of the turning planet, so the tidal torque takes energy from its orbit and the satellite spirals inward.

That boundary is not fixed. As a moon removes angular momentum from a rapidly spinning planet, the planet slows and its synchronous radius moves outward. A satellite can therefore begin by migrating away from Venus, only to be overtaken by the moving boundary and sent back toward the planet.

The calculations cover many possible beginnings

The team tested initial Venus spin periods from five to 100 hours, moon masses from one-hundredth to ten times the mass of Earth’s Moon, and different eccentricities, starting distances and assumptions about tidal dissipation. A commonly used starting orbit was five Venus radii from the planet’s centre.

For that starting distance, a 16.1-hour initial spin divided two outcomes. With a faster spin, the moon initially travelled outward. With a slower spin, it began inside the synchronous radius and moved inward. In a 24-hour case, it reached the Roche limit in roughly one million years.

Moon mass also changed the contest. A heavier satellite drives stronger outward migration, but it brakes the planet more powerfully and moves the synchronous boundary outward faster. In the authors’ formulation, outward migration scales with moon mass, while expansion of the synchronous radius scales approximately with its square.

The 30-million-year result is conditional

The rapid loss highlighted by the study starts Venus with a 12-hour rotation and gives it a moon twice the mass of ours. Under the team’s constant-Q tidal model, the synchronous radius catches the satellite and the inward-moving moon reaches the Roche limit after about 33 million years, commonly rounded to 30 million.

That number is not a general lifetime for any Venusian moon. In the same model, a two-lunar-mass satellite around an eight-hour Venus lasted about 1.7 billion years. A one-lunar-mass satellite around an initially eight- or 12-hour Venus survived the 4.5-billion-year integration.

The alternative constant-time-lag model allowed the two-lunar-mass moon in those fast-spin cases to settle into a near-synchronous state and survive. The fate therefore depends on how Venus’s interior dissipates tides at low forcing frequencies, a property with no direct measurement.

Crossing the Roche limit is not a complete ending

The Roche limit marks where the difference in a planet’s gravity across a satellite can overcome the satellite’s self-gravity. Crossing it makes disruption possible, but the calculation stops at that threshold. It does not simulate every fracture, impact or fragment that follows.

Some debris could fall onto Venus, some could briefly form a ring, and some might collide and reassemble. Those are possible aftermaths, not results demonstrated by this model. Here, destruction means that the original satellite no longer survives as one intact moon; it does not mean the material simply vanishes.

Venus gives a moon little room

Venus orbits at about 0.72 astronomical unit, so the Sun’s gravitational influence on the planet-moon pair is stronger than at Earth. Venus’s stable satellite region is correspondingly smaller, forcing a moon to remain relatively close. Tidal torques also rise very steeply at short distance, approximately with the inverse sixth power of orbital separation.

The question intersects with Venus’s peculiar present rotation. As Space Daily has previously examined, the planet now takes about 243 Earth days to rotate relative to the stars and turns retrograde. NASA’s Venus overview records a 224.7-day orbit, so one sidereal rotation lasts longer than a Venusian year.

A lost moon is not the only proposed influence on that state. Giant impacts, solid-body tides raised by the Sun and atmospheric thermal tides can all matter. The new model must satisfy two conditions at once: eliminate the satellite and slow an initially rapid Venus. It manages both only across a restricted set of starting spins and moon masses.

A plausible path, not a recovered history

Separate giant-impact simulations published in 2026 tend to leave Venus with post-impact spin periods of 12 hours or longer. That places an Earth-Moon-mass satellite near the boundary between survival and eventual loss in Kane and colleagues’ calculations, rather than decisively on either side.

No crater, chemical signature or orbiting debris has established that such a satellite formed. Future measurements of Venus’s interior could narrow the uncertainty in its tidal response, but they would not by themselves recover a missing moon’s history.

The value of the work is therefore narrower than proof of a lost satellite. It shows that a moon need not be removed by a second catastrophe. Under some reasonable, but uncertain, tidal assumptions, Venus’s own slowing rotation can reverse the moon’s migration and carry it to disruption surprisingly early in the planet’s life.