Dr. Anjeanette Roberts: Did Life on Earth Originate from Microorganisms That Came from Mars
So, there is a theory called panspermia that life was delivered to Earth from somewhere out in space, interstellar space. I would say that it's impossible that it was a living organism that was delivered to Earth. What is more likely is that different amino acids, which are building blocks for proteins, and different things like nucleic acid, which are building blocks for DNA and RNA, that these can actually be formed in interstellar space and it is quite possible that many of these might have been delivered to Earth. But then you just have molecules in a variety of different forms. Even one amino acid can have multiple forms of that amino acid. Life is comprised of something that is only one type, form of amino acid and only 20 amino acids out of many different amino acids that could possibly be delivered to Earth. So, it is very difficult to construct a narrative for these compounds even if they were delivered to Earth from interstellar space, that they would be able to be sequestered and assembled in such a way that they are actually bearing information, which is necessary to even get to sort of a precursor to what we see inside the simplest cell. So, it is really a hurdle that, I think, is so high, it is impossible to cross and to believe this that life was delivered from space.