...Now, fast forward to more recent times on Venus. We've begun to understand the story of its surface evolution largely due to the Magellan mission in the 1990s. The biggest surprise of Magellan was that the surface seems like it's all the same age. That's what I'm calling the second great transition. Something changed on Venus 600 or 700 million years ago to make the surface all the same age. If you use the word catastrophic it rubs some people the wrong way, but something dramatic happened on Venus which wiped out almost all signs of an older surface. The...