A Galaxy Infected with Life?

This is an excerpt from my post on Astrobites:

Title: Could life have arrived on Earth from another planet? Is this even a falsifiable hypothesis?
Authors: Henry W. Lin and Abraham Loeb
First Author’s Institution: Harvard College
Status: Published in ApJ Letters

The origin of life on Earth might not have been in a primordial pool of organic goo, but rather, according to the panspermia hypothesis, it may have come from another planet in perhaps another solar system.  Panspermia is one of the more popular alternative theories for the origins of life on Earth, but is it really testable?  If panspermia isn’t falsifiable, if you can’t make predictions that allow the theory to be tested, it’s not science.    (“A theory that explains everything, explains nothing.” – Karl Popper.)