As much carbon dioxide came out of the Earth's interior, mostly in volcanic eruptions, as is in Venus' atmosphere now. Our oceans remove carbon dioxide from the atmosphere and put it into limestone and other carbon-bearing rocks. The thick atmosphere of carbon dioxide is the reason why we have no direct images of the surface of Venus, other than the few snapshots sent back by the Russion space probes before they melted. The Magellan orbitor, which systematically mapped Venus from September 1992 to October 1994 really reveal Venus' true nature. Cratering One important clue to the age of a planetary surface is the numbers, size, and condition of the impact craters it bears.
Impact events are more or less random in space and time when viewed over the lifetime of a body.
The older the surface, the more craters it should have. We cannot put an absolute number on an age until we actually date the rock . By going to the planet and getting a sample. The impact craters on Venus were surprising to scientists. Craters appeared to be scattered randomly over the surface.