ELI5: Why didn’t the asteroid also reduce life the first time or also create a second moon the second time? Why those specific outcomes for those specific asteroids?
To add onto Size/Difference, also time. When the moon was created; life wasn’t what it was say during the time of dinosaurs. Also imagine that we say dinosaurs, but thats a massive amount of time. There were numerous periods of near total extinction events, where populations and species bottlenecked. A meteor was only one of these events over our 4+billion life span as a planet.
First one was before the Solar system finished forming, no life, it was also the size of Mars. The Moon is a combination of matter from that object and matter thrown up from Earth. Second one was tiny by comparison and we actually are pretty sure we found the crater