The Earth has existed for billions of years, and life arose only once. We know that because the DNA of all living creatures, from humans to yeast, is related. For all we know, Earth is the only abode of life in the universe.
Life has existed for hundreds of millions of years, and intelligence life appeared only once. Vision came into existence by means of several different evolutionary paths, but intelligence exists only in creatures with brains. Even if some kind of life exists elsewhere in the universe, Earth may be host to the only intelligent life.
The whole saga of human life may be a brief and unimportant episode in the history of the universe, and human civilization a minor and short-lived part of that.
But that’s not the only possibility. It is possible that the history of human life and civilization on Earth may be the prelude to the spread of life through the universe, a story that would continue for billions of years.
Recent discoveries show hundreds of planets around stars within observation distance. We don’t know how to get to those planets, but we do know how to get to planets within our Solar System, which would be a first step.
The billionaire American entrepreneur Elon Musk, the lesser known Dutch promoter Bas Lansdorp and others have announced their intentions of establishing a human colony on Mars. They want to be real-life versions of science fiction writer Robert A. Heinlein’s David Delos Harriman character in The Man Who Sold the Moon. Like Harriman, they seek profits only as a means of sending humanity to the planets and stars.
I am torn between the grandeur of this enterprise and the seemingly hard practical facts. Establishing a permanent human colony on Mars would be infinitely more difficult than, for example, establishing a self-sustaining colony in Antarctica or the Gobi Desert or a domed city at the bottom of the ocean.
Would people go? Many say they would. Could they sustain themselves in an environment so much more unforgiving than anything on Earth? Would there be an economic payback? Would people on Earth commit to supporting them indefinitely?
I don’t know enough to answer these questions, but my gut feeling is “no”. But then again, I agree with Arthur C. Clarke, another science fiction writer, who said that the only way to know the limits of the possible is to venture a little bit into the impossible.