In nearly every environment on Earth, there is some form of life. Many of these environments are quite hostile to most forms of life, but some are able to make them into a perfectly suitable home. Such locations could be deep underground in mine shafts, or near vents on the ocean floor, or even inside volcanoes. These creatures are called extremophiles.
Extremophiles are responsible for the coloration in this hot spring. Image from Wikipedia
Extremophiles are of particular interest to astrobiologists because they make the possibility of life on other worlds much greater. Many that exist on Earth don’t require the same things that more typical life does, such as oxygen or substantial water. They can exist in environments of extreme pressure, or those with no pressure at all. Thus, they could possibly inhabit other worlds and places in our solar system and beyond where these typical conditions don’t exist. Possible candidates for homes of extremophiles include Mars and many moons of the jovian planets. If you want more information on the subject, you can find it here.
