This is a FAR more important qualification than any requirement for equilibrium -- in fact the equilibrium argument is superfluous. Complex life evolved freely -- wantonly -- on Earth because Earth is anything BUT a closed system. The Sun constantly beams down a torrent of energy onto the Earth's surface. Virtually all of this radiation is eventually re-radiated back into space, where it expands virtually unimpeded into an effectively infinite volume, creating all the entropy that could ever be required, and allowing the local decrease in entropy that is absolutely characteristic of every living organism. In the process of being absorbed, flowing from one point to another, and eventually being lost again, that energy does useful work on the Earth's surface, including creating energetic molecules which plants and animals alike rely on for survival. That accumulation of 'negentropy' is perfectly allowed by the laws of thermodynamics in an open system. If we were to regard the Sun, the Earth, AND all the radiation emitted by the Sun as a closed system (it isn't perfectly, but close enough) then entropy is increasing massively overall, and the fact that a little turbulence in the flow of energy has produced all the complexity of life on earth is not even a jot in the entropy balance.
The suggestion that an impact is involved is also completely unnecessary. We have known since the days of the Miller-Urey experiment that radiation alone is sufficient. All the faddish theories about "life formed in outer space" will eventually be discarded as being as untenable as they are unnecessary. The attraction of these theories is romantic, not scientific -- there are no holes in any theories demanding an extraterrestial origin of life.
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