Yes. If you mean bacteria on other planets. No. If you mean a supreme being (God) who "created the universe and everything in it".

Do I believe in it? That's a deceptively simple question which leads to a complex answer. Firstly my answers don't come as an atheist more as a science enthusiast. As an atheist I have only the simplest of definitions i.e. lack of belief in god(s). There is little more to it. What follows are my personal opinions which aren't anything to do with my atheism. Do I believe in ET life in one form or another? Possibly. I have no evidence either way. Despite repeated attempts to quantify the likelihood of ET life we are simply blind on this question. We can't begin to estimate the chances. For all we know the probability of life emerging in one in a quintillion or it could be one in two. We simply do not know. We see a great many stars and are starting to discover planets are fairly common as well but we still cannot estimate how many will have life. It is often said that due to the abundance of planets the probability is high but this is fatally flawed. We do not have any idea of how likely it is for life to emerge and as such cannot make any such statement. It is like trying to predict how many plane crashes will occur this year from the number of flights with no data on the number of crashes in previous years. Incredibly risky statistics. On the other hand gut instinct says I find it difficult to believe that we are somehow unique in this regard. There has been a steady process of displacing the uniqueness of Earth. We were not so long ago the centre of the universe, we are now relegated to a small planet around a fairly insignificant star in galaxy amongst billions. Is our latest geocentricism that of life bearing? However the long and short is we just don't know. Despite my argument against geocentricism I could be wrong and the Earth is unique. I doubt it but it is purely a gut instinct. So I don't believe there is ET life but I think it is certainly possible and have a gut instinct it is likely and maybe even common. But I do not really believe there is as I have no evidence yet. Once I have evidence I will change my position from gut instincts to well founded 'beliefs'. As for ET life visiting us - no. Almost certainly no. There is a remote, very remote possibility but it again there is no evidence and a good number of reasons to think this is incredibly unlikely. Again I stress, none of this has anything to do with my opinion on religion which I hope is clear from the answer I have given.

Atheism does not address the question of E.T.'s. Different people have different views on whether they can visit us. The problem with that possibility is that if you work from our current understanding of physics, then no, they are limited by the speed of light. However that has come into question lately as a result of quantum physics problems which seem to contradict it; like entanglement, which is a form of communication that is instantaneous. If they can visit us, then it is likely that they have done so. If for no other reason than curiosity.

I answer from the general point of view. The possibility of e.t. existing is far more than we can imagine. with our limited knowledge and just a small eye in the sky our vision is limited but as we go along, we may come across a lot of things which we will not be able to understand. So we need to keep our mind open for all possibilities.

Atheist isn't a proper noun and shouldn't be capitalized mid-sentence. Its plural is atheists. Not trying to be a grammar Nazi--just trying to help. Atheists don't believe in god(s). It's the only thing we have in common. Some atheists may believe in extraterrestrial life and some may not. There is no evidence for extraterrestrial life so it seems logical to withhold judgment for all of us atheist and theist alike. I think it logical to argue for the probability of alien life given the vastness of the universe, but I don't have any evidence and so I do withhold judgment.

atheism has nothing to do with extraterrestrial life. It's like asking do christians believe in the designated hitter.

They will believe if you could produce scientific proof as to the existence of extraterrestrial life. Not just Atheist, all of us will believe if a proof if produced.

I believe it's possible, even if it's some kind of little bug, or bacteria

There is no evidence yet for extra-terrestrial life. Hence I neither believe (because there is no evidence) not disbelieve (because the amount of the universe we have actually been able to explore is negligible). Given that we know that billions of galaxies each consisting of billions of stars exist, my guess (but not belief) would be that somewhere out there there are other life forms. But whether we will ever contact them I really cannot say;.

There are various ideas of God and various kind of Atheism. Also, there are various ideas about extraterrestrial life and various point of views concerning it. Among all those various views, there are certainly some atheists who believe in extraterrestrial life and some who don't. People who don't believe in things as long as they are not proven will be atheists and won't believe in extraterrestrial life, for the same reason.

If we find proof :)

Some do, some don't. Atheism and the existence of ET's are totally unrelated. Personally, I'm inclined to think that there is life out there somewhere; I think that it is very self-centred to think that we are the only sentient species in the universe. I don't believe they visit Earth though.

Some do, some don't. You'd have to ask the atheists individually.

Do Christians eat breakfast?! ;-)