In the long term cycles of the solar system, gravity can play funny tricks. Earth and Venus are, or should I say were, in stable resonant orbits, meeting every 1.6 earth years and 2.6 Venus years, with five meetings every eight earth years and thirteen Venus years.
I say were, because I write from the future, after the collapse of Venus.
Gravity plays funny tricks. Sol is a third generation star. The first generation were just hydrogen for about five billion years after the Big Bang. In the second generation, as hydrogen fused to helium, every time that three helium atoms banged together near simultaneously they formed a carbon atom. By the time of the supernova explosions at the end of the second stellar generation, stars had made heavy elements up to uranium.
After the dust cloud coalesced to form our solar system, the gas giant planets were closer to the sun, and Neptune was inside the orbit of Uranus. Jupiter and Saturn drifted into a 1-2 resonance about four billion years ago. This set the solar system barycentre ringing like a bell for two million years until Neptune was expelled to its current distant orbit in 2:3 resonance with lowly Pluto.
The Neptune expulsion caused the late heavy bombardment that put the face on the man in the moon, 3.9 billion years ago, as Neptune drifted through the thick debris of the early dust clouds of the solar system, slinging and hurling everything to clear the orbit.
Venus is an unstable planet. It heats up like a pressure cooker due to its radioactive rocks, but has no plate tectonics so the surface entirely melts and reforms.
The collapse of Venus turned the former planet into a ring of asteroids around the Sun, like the rings of Saturn. How it happened no one really knows. But one day, telescopic observation saw the planet fall apart, and within weeks the mass of Venus was smoothly spread around the whole path of its orbit.
These events proved near cataclysmic for the earth. Due to rapid action, the threatening Nibirus of Venus were all shepherded into a stable orbit. Almost all that is. The former stable pattern of five conjunctions every eight years between Earth and Venus was a foundation for the gravity topology of the inner planets. Luckily the collapse of Venus did not sling earth out to the outer darkness, to wail and gnash our teeth out in the cold depths of space past Pluto. Earth remained in the just right Goldilocks Zone, with not too much and not too little solar radiation for liquid surface water.
Managing the threat of thunderbolts from Venus was the main problem. Several got through, and smashed regions. Defence of the earth required system engineering. Space travel got serious. Instead of rockets, mile high trebuchets were placed at the equator to sling payloads to a ring around the earth at the geostationary orbit. From this space ring, the war was waged against the giant fizzing asteroid meteors from the deconstructed Venus.
The only way to stop the tribulation of further natural attacks was to braid the Venus ring with shepherd moons. Nine of the biggest moon chunks from the former sister planet could serve as wardens for the rest of the unruly rock fragments. The theory was that the space rocks of Venus could form into three braided orbital paths, each shepherded by three moons.
Necessity is the mother of invention, and the awesome ability to move moon size planetoids and calculate a stable orbital path were the children of necessity.
Venus used to be known by the ancients as Lucifer, in its incarnation as the morning star rising slowly before falling suddenly to the Sun. Venus was now caged, and the dragon would be held in prison for one thousand years. The difficult factor, worsening the ring management after a millennium of success, was comets. Each comet that passed through the orbit of Venus was a logistics nightmare, recalibrating the orbital paths of the shepherd moons to keep the debris contained. Over the centuries, it seems each comet introduced a new small chaotic factor, and as these build up, the stability of the original mathematical calculations grew more incapable of halting resonant harmonic patterns. The comets at the end of the millennium finally broke Venus from its prison, but only for a short time.
Note: I doubt that even an asteroid the size of the moon would cause problems for the earth if it hit Venus. Venus is not going to disintegrate. However, it is an interesting thought experiment, which prompted me to sketch this science fiction story. Robert Tulip