When did the idea of life on Europa put forward?

The idea of life on Europa, one of Jupiter's moons, gained significant attention in the 1970s following the Voyager spacecraft missions. These missions revealed that Europa has a smooth, icy surface, which suggested the possibility of a subsurface ocean beneath the ice. The concept was further popularized in the late 1990s and early 2000s as more evidence emerged, including the detection of a magnetic field around Europa, indicating the presence of a salty ocean that could potentially harbor life.