I was reading lots on the planets and the atmosphere around them. We have detected creatures in the icy lakes and in very hot areas. I was wondering can there be life on other planets. They may not be aliens but some sort of creatures living on other planets. And if so yes, how could they live on other planets?
The most likely kind of 'aliens' are indeed bacteria and other small micro-organisms similar to the ones that we have found in extreme environments on Earth, such as frozen lakes, hot springs and thermal vents. There are long term plans to send a mission to Jupiter's moon Europa to search for just this kind of life. We know that Europa has a liquid ocean beneath it's icy surface, and the geological activity induced by the tides from Jupiter may well result in thermal vents very similar to those found on the ocean floor near mid-ocean ridges on Earth.
Pretty much everywhere we look on Earth we find life that has adapted to living there, and we can see places elsewhere in the solar system that look like they may have environments similar to ones we have found life in on Earth. Sending missions to these places and finding out whether they also have life will tell us a lot about how common life is in the universe, and how life evolved on Earth. Missions like that are very complicated, and expensive, however, partly as we need to make sure that they don't accidentally take any Earth life with them. It would be rather annoying to have sent a mission millions of kilometres only to detect bacteria that have hitch-hiked from Earth!