July 2018, NASA HQ
Astrobiological Announcement, Guest speaker Michael Evans-Verres
The direct audience was very small. Several senior members of JPL had spoken on fulfilling the dream of the space program, that of finding life elsewhere in the universe. Michael Evans-Verres had become the world leader in exobiology because his priors were just simply too good. Nobody knew how, but he seemed to understand the significance of any advance somehow before hearing it. On taking the podium, Michael noticed his old friend Alastor had somehow gotten in behind the press. Now that just took the cake, didn't it.
"Today I want to speak to you about evidence", Michael began. "Methanethanol and dimethyl sulphide are interesting chemicals indeed. But what they don't say is far more than what they say. What we have here is an area that accumulated a bunch of organic compounds, buried them, and left them under the surface to break down slowly enough from radition that we would find them after billions of years.
"What we want to find is a second origin of life. We want to change the prior for life's existance to one of billions of stars to two. While we would like it to be two out of eight, the evidence before us simply does not support that claim. Twenty years ago I heard a credible claim from a young-earth creationist" that last word spoken with a hint of spite, as though he knew that his audience would know what to think of their scientific knowledge "that we would find life on Mars if we looked long enough. The scenario runs something like this. Of every hundred fragments of rock ejected from Earth by collisions, about ten or so end up on Mars. Certain bacteria, fungi (particularly certain yeasts), some protists, and the water bear can survive the journey to Mars riding inside such a rock. If Mars were ever suitable for growing life, we would find ancient primitive earth life had been growing on Mars.
"It is likely that Mars was preseeded by comets and asteroids rich in proto-biological material like Earth was. Mars is barren now because its gravity is too low to hold an atmosphere of water. Ladies and Gentlemen, what we have here is quite good evidence that Mars was indeed preseeded and this seed material was eaten by some primitive life forms, quite possibly sulpher-loving archaebacteria. What we do not have here is any evidence at all of indipdendent life origin on Mars. We know life first appeared on Earth about 4.5 billion years ago, as soon as Earth was sufficiently cool. We have found Mars rocks on Earth. The probability of Earth life making it to mars is simply too good.
"The transfer of life on ejected rocks has good explaining power, for life should have gone extinct on early Earth several times from impacts that remelted the crust, but life always seemed to surive them like nothing happened.
"I say to you, I would be the first to celebrate on good evidence of Mars having its own life origin, but that task is not so easily accomplished. When you find life on Mars (and I expect you will), or any enzyme, or intact nuclear material, I shall gladly look at it and we shall see. If the principles by which that life works are utterly different from Earth life it shall be time to celebrate. If the are the same, than transfer of life from Earth to Mars or possibly transfer of life from Mars to Earth is a much more reasonable scenario. Today I expect the latter.
"But we are not alone, of that I am certain. Reach for the stars, for only then will you find what you seek."
"Thank you."