It's likely that they're not much more developed than bacteria. On the other hand, Europa's aliens might actually exist, and with a few experiments and some simple discussion, you can bring this idea to life for your child. Some scientists think this points to the existence of a massive ocean beneath Europa's icy surface. This idea isn't completely new, however. But the scientific community largely dismissed Hoagland's theory as unscientific.
Scientists believe Jupiter's intense gravitational pull generates heat in Europa's core.
The moon's distance from Jupiter varies as it orbits the planet, and scientists think that this produces a push-pull motion, creating tides within Europa that generate heat. By melting ice at the moon's surface in certain localized areas, this heat may be literally changing the face of Europa. The presence of heat and water on Europa would fulfill two of the requirements for life as we know it. In the past scientists also believed that life could not exist without sunlight. But recent discoveries in the Juan de Fuca ridge system off the coast of Washington state have proven that primitive life forms can exist without sun exposure, supported only by heat generated from deep underwater volcanoes.