If panspermia does happen in the universe, I bet that it happens with the sheltering of asteroids and meteors.  Life develops on low-gravity planets with turbulent atmosphere -&gt; some cells get into space -&gt; get caught by comets and other objects -&gt; slowly propagate within comet -&gt; comet has an unstable orbit that sends it to another system, where it has an encounter with a habitable planet.<p>An icey comet could provide radiation protection and it could accidentally go through a gravity assist to increase it&#x27;s speed.<p>I suppose that the best evidence we could collect to prove or disprove panspermia is to see if it&#x27;s happened between planets&#x2F;moons&#x2F;objects within our own solar system.