Liquid water is the main factor for life.
A major evidence that liquid water existed on Europa may be seen on this pictures. As you see this flat area in the middle must be younger that the sorounding area. A evidence for flooding with water is that the former line structure within the flat area is slightly visible. Possible water outlets could be these two knobs. Perhaps the meteorite impact caused a major disturbance in the ice surface, which caused two openings in the shield down to the liquid underground.