Over these past few weeks, we’ve all been stunned by the beautiful images returned by the Perseverance rover on Mars. One of that mission’s main purposes is to find traces of past life on the Red Planet, and the rover has already started traveling around Jezero Crater in pursuit of that goal.
For me as an astrobiologist, no discovery would be more exciting. Yet there are other ways of looking at it. In a 2007 essay, Nick Bostrom, Director of Oxford University’s Future of Humanity Institute, wrote that while the discovery of life on Mars would be of tremendous scientific significance, it would be really bad news for the future of the human species.
A re-evaluation of Bostrom’s argument seems timely now that we’re actually getting closer to determining if life ever existed on Mars. Why would a “yes” answer freak out Bostrom? As often happens when considering the possibility of extraterrestrial life, it comes back to the Fermi Paradox—also called the Great Silence. Despite our best research efforts, we have not found any firm signs of intelligent alien life, even though there are myriads of planets out there, many of them likely habitable. A huge number of these must have formed well before our own Solar System, so if the evolution of technically advanced alien species is not incredibly hard, shouldn’t there be evidence of advanced aliens all around us? But there is not.
That means there must be a “Great Filter”—a kind of evolutionary hurdle that prevents most, or maybe all, life forms from becoming a “cosmic” species. And this Great Filter must be very effective. In Bostrom’s words: “There are billions of potential germination points of life, and you end up with a sum total of zero alien civilizations that developed technology to the point where they become manifest to us Earthly observers.”
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