Bear in mind that the absence of proof is not a form of proof. Just because you cannot imagine a particular event or occurrence happening does not mean that it could not have happened. There was a time, not so long ago, that the world's leading thinkers could not image that the earth revolved around the sun.
Which is really quite irrelevant. It is true that SOMETIMES a lack of proof does and doesnt prove something. Your example illustrates both. Previously, a lack of information didnt prove or disprove the revolution of the planets. Yet some hundreds of years later, with the further information we obtained, proof was indeed shown. Now, once we were able to view the planets from an "outer space" point of view, if no evidence were obtained to show the planets circling around the sun, one would rightly conclude that they dont. (this is assuming the hypothetical that in this particular scenario, the planets in fact DONT revolve around the sun.)
Also, dont conclude that because you dont KNOW something exists, that others must not also. Columbus had discovered American, but upon returning, many if not most, didnt believe he had. Yet Columbus at a point in time, KNEW for a fact he had reached land going west. There are some of us who have experienced God in a way that there is no other explanation.
And regarding the idea that life on earth came from another planet,, your proof? And even if it were true, that only moves the problem from one place to another, it doesnt solve the problem that the single cell is simply wayyyyyy tooo complicated to have evolved on its own, much less to have created DNA so that it could replicate itself. Self replication is in fact contrary to survival of the fittest. A self replicating species would fall prey to a non self replicating species.
For example, if two completing species of humans evolved at the same time (unlikely, but I will use it as an obvious example of how it works, and this example would be plugged into some earlier time frame of the supposed evolution of life) and one was self replicating, via having women get pregnant, and the other was only males. Lets say the two groups each had four people. Now, since men are bigger and stronger than women, when the two groups would clash, the non replicating species would overpower and eliminate the self replicating species.
Self replicating always detracts from an INDIVIDUALS ability to survive. Self replicating only helps a group, a species to survive. Survival of the fittest applies only to individuals, since it is a non thinking, non planning theory. In order for an event or ability to promote something in the future, another generation, it must have been planned. Just as many animals dont gather any food or water for droughts, because their conception of the future is limited or completely nil. Only those animals that are pre programmed by God can do that, what atheists call instincts, like birds flying south for the winter, they have no idea why they do it, its just an automatic activity they do, just like the salmon who swim upstream), and species that are intelligent enough can do it also. Planning ahead requires intellligence, either by an outside entity that programs it into the brain, or by the entity itself. Either way, DNA had to be a plan of an intelligent creature.