The hypothesis stating that the cause of Venus's slow and retrograde rotation is by a collisional event isn't plausible according to recent studies. The planet would be obliterated if an event like this would happen. A more likely explanation is by Venus used to have a prograde rotation comparable to that of Earth's but a runaway greenhouse event formed a super thick and dense atmosphere which is enough to slow and reverse the rotation of the planet. Also, the hypothesized protoplanet that collided with Venus mentioned earlier didn't literally caused Venus's axial tilt to "flip over" but instead reversed its rotation. Moreover, the gas giants Jupiter and Saturn would be approximately three times bigger than their present sizes in their primordial days due to the high temperatures expanding their gas envelope.
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The hypothesis stating that the cause of Venus's slow and retrograde rotation is by a collisional event isn't plausible according to recent studies. The planet would be obliterated if an event like this would happen. A more likely explanation is by Venus used to have a prograde rotation comparable to that of Earth's but a runaway greenhouse event formed a super thick and dense atmosphere which is enough to slow and reverse the rotation of the planet. Also, the hypothesized protoplanet that collided with Venus mentioned earlier didn't literally caused Venus's axial tilt to "flip over" but instead reversed its rotation. Moreover, the gas giants Jupiter and Saturn would be approximately three times bigger than their present sizes in their primordial days due to the high temperatures expanding their gas envelope.