The Red Planet has been getting a lot of attention recently, between India's low-cost MOM probe entering Mars's orbit, NASA's MAVEN doing the same, and the Curiosity rover reaching the most potentially fertile site yet for signs of ancient life. Elon Musk has even talked about building a city there. For most people who look out at the night sky and wonder whether we're alone, Mars holds our best hope for proving that we're not.
The famed futurist, author, and Director of the Future of Humanity Institute at Oxford University, thinks that any sign of life we find on Mars would be a bad sign, an argument he developed in a 2008 paper entitled "Where Are They?: Why I Hope The Search For Extraterrestrial Life Finds Nothing."
It would be good news if we find Mars to be completely sterile. Dead rocks and lifeless sands would lift my spirit.
Conversely, if we discovered traces of some simple extinct life form — some bacteria, some algae — it would be bad news. If we found fossils of something more advanced, perhaps something looking like the remnants of a trilobite or even the skeleton of a small mammal, it would be very bad news.
So, why the apparent negativity?
NASA/JPL-Caltech/MSSS Scientists around the world are hoping that NASA's Curiosity rover will find silicon in these rocks on Mount Sharp, an indication that this might have once been an environment for life. Nick Bostrom hopes the rover finds nothing of the kind.
Simply put, evidence of life on Mars would suggest that life in the universe is not uncommon, and that induction would lead to a troubling conclusion.
It all comes down to the question of why we haven't encountered any signs of intelligent extraterrestrial life (not to mention any extraterrestrial life whatsoever) — a quandary originally posed by physicist Enrico Fermi, and known as Fermi's Paradox. If none of the billion and billions of planets in space has developed civilizations that are advanced enough to communicate with or be detected by humans, then there must be something that prevents that from happening.
"There are planets that are billions of years older than Earth," Bostrom writes. "Any intelligent species on those planets would have had ample time to recover from repeated social or ecological collapses. Even if they failed a thousand times before they succeeded, they could still have arrived here hundreds of millions of years ago."
Bostrom reasons that there's a "Great Filter" that must exist either in our past or our future. If the hard part of becoming an interstellar civilization is the emergence of life, then the filter is in our past and humans are entering exciting new territory. But if the emergence of life is common, then the hard part could be getting through technological adolescence without destroying ourselves — in which case humanity may be in for hard times.
Another potential option is that the same life lived on Mars as does on Earth now. That would mean that life somehow originated on Mars and was transferred to Earth, or vice versa. In that case, the origination of life would still be an extremely improbable event that only happened once. It would thus still be a good candidate for the Great Filter to have come before current time.
What could have caused other intelligent alien civilizations to disappear? Bostrom points to risks we face today:
To constitute an effective Great Filter, we hypothesize a terminal global cataclysm: an existential catastrophe. An existential risk is one where an adverse outcome would annihilate Earth‐originating intelligent life or permanently and drastically curtail its potential for future development. We can identify a number of potential existential risks: nuclear war fought with stockpiles much greater than those that exist today (maybe resulting from future arms races); a genetically engineered superbug; environmental disaster; asteroid impact; wars or terrorists act committed with powerful future weapons, perhaps based on advanced forms of nanotechnology; superintelligent general artificial intelligence with destructive goals; high‐energy physics experiments; a permanent global Brave‐New‐World‐like totalitarian regime protected from revolution by new surveillance and mind control technologies. These are just some of the existential risks that have been discussed in the literature, and considering that many of these have been conceptualized only in recent decades, it is plausible to assume that there are further existential risks that we have not yet thought of.
It's in light of those scary possibilities that Bostrom hopes to find more evidence on Mars of the rareness of life on Earth.