The fact we can even consider the notion of colonizing Mars can only mean we as yet have no idea the many coincidental and very specific conditions necessary for the spontaneous generation of biology.
As one example (of hundreds...thousands?), before space exploration we did not know to what degree the specific conditions of earth's gravity effect physiological regulation. Now we minimally know weightlessness dysregulates physiology to pathological levels. To what degree varying levels of gravity dysregulate physiology we are fuzzy on.
What are some other conditions that would have to be met before the spontaneous generation of biology can occur?
The exact conditions of the relationship of "feed star" to "dependent planet" that have to be met for biology to occur.
The exact conditions of dependent planet atmosphere?
The percent of dependent planet surface that would have to be water?
We could go on thinking of other conditions that would have to be met before the spontaneous generation of biology could occur.
But let's think of two other things first:
1) In spite of all of our technological sophistication we are as yet unaware of a single example of another planet with biology.
2) What other conditions are we as yet completely unaware of that would have to be met for the spontaneous generation of biology?
It's as if we truly do not know where we are, even though we are living there. Already.
Can we take better care of the biology (including us) on this planet?
Or are nature's balancing forces working through us, already, and we are basically unaware of it?
In that sense (hubris vs mortality), we are not in control of our destiny to the extent we like to think we are, if we are first not in control of Earth's biological condition.
Can we even control our own biological condition? Why is the wealthiest county in history the least healthy?
Can we live with that? Do we have a choice?