When humans search for meaning beyond our planet, We seek for life, Not God. Being alive is assumed, But without it there is no capacity to search for any purpose, Let alone God. Meaning is derived from value - that which has value forms the basis for all purposeful actions. Life is the only requirement without which no purpose can exist, And therefore valuing life is the only universal purpose for living beings.
No one has any real answers. Blind faith in an archaic assumption is pretty worthless, But we all have our particular hobbies don't we?
I propose that the evolution of matter is a continuous loop or chain of events and organic life is an essential link in that chain of events. Maybe we assist in the creation of a God like device which is essential to the regeneration of matter at the final point of universal collapse.
Of course everything could just be pure chance. Who knows?
If one did not believe in a God, one would not feel the necessity to follow any divine code. Therefore, one would be defining his/her own purpose as long as he lives, but that purpose would not be able to extend past death as does the purpose of life in a believer of some sort of God. One would not need to fulfill anything other than his own goal, rather than a universal meaning. This "it is what you make of it" sort of attitude does not strike me to sufficiently cover an overall umbrella term for purpose of life.