First question: how do you know it is not possible for life to pop up on its own? Do you have THE definitive definition of what constitutes "life," of what it actually is, that allows you to make that claim? Can you point to the absolute delimiter between what is alive and what is not, in every case?Its not possible for life to "Pop up on it's own" and we have no proof of life on other planets. Just this one.
Second question: how many other planets have you been to? Just how many planets do you think are in this one (Milky Way) galaxy alone, among its 100 billion stars -- not to mention how many billions of galaxies there are. And since we cannot reach even a miniscule percentage of all of those planets in all of the known universe, how safe do you feel in supposing there's probably no life anywhere but here?