Will we find traces of life on Mars?
You may have heard of the Fermi paradox. The theory asks the following question: "Given the high possibility of other life in the universe, why has no one contacted us?"
If there are other civilizations out there - perhaps in more advanced stages than we are because of how long the universe has taken - why don't they do what we do and send out probes and signals and look really hard for other signs of life?
The Great Filter hypothesis says that before alien civilizations can get to the point where they can leave their solar system and begin colonizing their galaxy, something will happen to stop them, or we would see evidence of this in our own Milky Way.
Whether that happens when multicellular life evolved into animals that can use tools, or what happens to us now that prevents us from exploring the galaxy, we don't know.
What makes this interesting is that we will not know if we have passed the great filter, or if it will happen in our future.
Could it be that most life is unicellular and we pass this filter? Or will it be at some point yet to come? Are we, like other alien civilizations, about to destroy ourselves with wars or by exhausting our resources before we can get out?
Some philosophers and scientists have suggested that if we find life on Mars, for example, it will have less-than-ideal implications for who we are in terms of the great candidate.
Nick Bostrom, professor of philosophy at the University of Oxford, says he hopes we won't find extraterrestrial life.
“If we find very simple life models, we can conclude that the filter occurs sometime after that point in life,” Bostrom said in an article published in MIT Technology Review in 2008. But if we find multicellular life, that would mark the point at which the great filter could occur.”
Bostrom believes that in order to determine when a filter occurs, we must look at life on Earth for unlikely steps. He wrote: “One of the criteria is that transmission should only happen once. The ability to fly, the sense of sight, photosynthesis and limbs have evolved many times here on Earth and must therefore be excluded.”
He argued that evolutionary features that took too long even after the basic requirements were met would indicate that such an evolutionary step was unlikely, like the original emergence of life. The transition from animals to humans occurred over a relatively short period of time, in geological terms, indicating that this transition is a weak candidate for the Great Filter event.
If we find evidence of invertebrates on Mars, it would be terrible news, because it indicates that the bulk of the great candidate is still ahead, and we have to face the possibility that we will go extinct before we are technically mature enough to travel across the galaxy.
“Such a discovery would be a crushing blow,” Bostrom wrote. It will be the worst cover story ever. That's why I hope our space probes will only find lifeless rocks and sand on Mars, on Jupiter's moon Europa and anywhere else astronomers look. And we will keep hope for a great future for humanity.”
There are many other possible solutions to Fermi's paradox that are worth looking into if you enjoy this sort of thing, but if Bostrom is right, then finding evidence of advanced civilizations is good news, and finding the wrong stages of life that evolved independently In our solar system it would be the worst news we could ever receive.