An essay: Do you think it is probable or improbable that life exist in other planets? People fascination with creatures from outer space has made them vividly present in the modern popular culture. Although it is unlikely that intelligent extraterrestrials with advanced technologies visit us, there could be simpler forms of life out there. In fact, there exist some spatial programs aimed at searching signals of life in other planets. So, we may ask ourselves: Is extraterrestrial life probable or would this search be in vain? We have no proves of the existence of extraterrestrial life so far. Living organisms, as we know them, require very concrete environmental conditions. So, it seems unlikely that they may exist in other planets. Besides, the spontaneous appearance of life, or abiogenesis, is much more improbable: to our knowledge, life appeared only once on earth, under a completely different environment that the one that we have now. Whatever the improbability of this, one may argue that the universe is immense. We do not even know the amount of planets that may be suitable to hosting life. If life appeared and survived on Earth, why couldn’t it exist on other planets? In addition, there could be others forms of life not carbon based that we do not even imagine. In conclusion, there are many reasons to think that the existence of life in other planets is unlikely; however, there are also reasons to believe that life outside the earth is possible. As the universe is so wide that we do not even know its boundaries yet, I am inclined to think that there may be many planets hosting life.