Panspermia is the idea that life could have emerged on an alien planet, and then could have travelled through space to Earth, where it flourished and evolved into all the life we see today. So you, your family and your cat could all be aliens.
In the first post I looked at the idea that this alien life could have been simple bacteria, and could have travelled to Earth early in its history either in spores or in asteroids or comets. This is very much the ‘traditional view’ of panspermia.
In this post I’ll look at some alternative forms of panspermia, such as the idea that intelligent aliens may have deliberately seeded Earth with life.
Astrobioloblog 