Many scientists believe that the chemical processes that gave rise to life must have needed hundreds of millions of years to develop the essential enzymes, proteins and genetic codes for life to begin. Since there was too little time to complete the job on Earth, it is likely that life originated elsewhere, drifting through space to Earth in the form of spores or by some other means. This is known as the “panspermia” theory.
If it happened then it might happen now. Perhaps it is happening all the time.