Below is a comment I wrote on
The problem with panspermia is that if life on Earth came from some other location in outer space, where did it come before that and so on with no end. Water, the universally copious life inducing solvent is factually known to have that effect so its location in a Goldilocks zone is necessary for organic compounds to animate in it no matter their provenance. Planet Earth, being a huge receptacle of water, is placed exactly where life sprung up in our Solar system even if this was added to in substance by relatively small extraterrestrial bodies like comets.
No matter where Earth life's original seed came from, the most important factor in it propagating itself is by virtue of a Goldilocks zone.