Where in the universe is life possible?

Where in the universe is life possible?

Earth is the only known example of an inhabited world. Life on Earth is based largely on the existence of liquid water Scientists used to believe that there could only be liquid water on planets that orbited within a very narrow band around their star This was because heat from the star would need to be great enough to melt ice, but not hot enough to evaporate all surface water Within our solar system, only Earth fulfils these conditions, although in the distant past Mars might have met them as well.

However, we now believe that on one of Jupiter's moons there is an ocean lying beneath a thick layer of ice. The ice is melted by the tidal energy of the huge planet close by, and might be able to harbour life. This discovery means that the area around a star in which a populated world could exist has expanded considerably. Of course, we must not exclude the possibility that quite different life forms exist that can get by without water.