Given the vastness of the universe and the number of planets that exist, it is considered very likely that there are other inhabited planets in the universe.

There are a number of factors that suggest the possibility of extraterrestrial life. One of the most important is the sheer number of planets in the universe. Recent estimates suggest that there may be as many as 100 billion planets in our own Milky Way galaxy alone. And with the discovery of exoplanets (planets orbiting stars other than our Sun) becoming more and more common, it seems likely that many of these planets are in the habitable zone - the region around a star where the temperature is just right for liquid water to exist, which is considered one of the key requirements for life as we know it.

Furthermore, we have already found evidence of the building blocks of life (such as amino acids) in space, suggesting that the ingredients necessary for life are common throughout the universe. In addition, we know that life on Earth has survived in a variety of extreme conditions, suggesting that life may be able to exist in a wide range of environments.

So while we have not yet found definitive evidence of extraterrestrial life, the possibility of its existence is considered very likely by many scientists.