Picture from European Space Agency
As of now scientists believe there are three requirements for a planet to develop and sustain life. Liquid water, the appropriate chemical elements, and an energy source. Europa has more than enough water, as it is believed that below the roughly 15 miles of solid ice, lies twice as much water as in Earth’s ocean, even though Europa is a fraction of Earth’s size.
As of now the most likely way to get more information about possible life at Europa is to sample water from water vapor fumes shooting through the ice. We would have to send a spacecraft to Europa with capabilities of finding and sampling these fumes.
Europa is currently the best chance of finding life outside of Earth, and it is important to explore this possibility as it would significantly alter how we view the development of life in the universe. If life has developed on two separate bodies in the solar system, life may no longer be viewed as a freak of nature, but as a result of the right combination and not wholly uncommon features in nature.
Source – Europa : Ocean Moon
Johann's Astronomy Blog 