NON-DIRECTED PANSPERMIA
Personally I prefer the idea of non-directed panspermia. In this theory life exists throughout the cosmos and has always existed. In interstellar space, the life forms would have to be hardened microbes or spores, possibly attached to material ejected from stellar systems.
On rare occasions an interstellar microbe gets accreted onto a planet or object that has the right properties for sustaining life. Then via the wonders of evolution: Life in all its glory and diversity.
The hardiness of microbes and spores to survive long periods in space, at very high temperatures and at very low temperatures, and at a huge range of pressures, has been fairly well established and the testing has only begun. Some bacteria actually thrive in moderately radioactive environments!
With non-directed panspermia we totally avoid the need to create complex life forms from scratch using inorganic matter. In this theory there never was a time when life was not present in the cosmos. It has always existed and can move around, albeit on astronomical time scales. This assumes the Universe is eternal and our little observable universe is a blip in the proverbial ocean.