It is a truism that where life exists it will expand to use every resource available. Three and a half billion years later, back on Earth, life had left the oceans, evolved to exploit all the resources of the planet, and had been merrily going about doing so until the Earth had little more to give. Luckily, that life had also evolved into a form that no longer required a random collision to leave the surface of its planet. That life looked up and thought, “We could go out there. We should probably go out there.” So that life returned to Mars in machines of its own design, set up shop mining the frozen ancient water from whence it had originated, and began to build an existence for itself on this now strange and desolate planet of its birth.
Flirting with panspermia in Water: Generation Mars, Book Three. Available now at https://www.amazon.com/Water-Generation-Mars-Book-Three/dp/1733731067