A NASA spacecraft embarked on a mission on Monday to explore Jupiter’s intriguing moon. Europa, in hopes of uncovering whether its vast hidden ocean might offer clues to the existence of life. Europa Clipper will take 5 1/2 years to reach Jupiter, where it will enter orbit around the gas giant and conduct dozens of flybys of Europa, braving intense radiation. Scientists are confident that a deep global ocean lies beneath Europa’s icy shell. With water often considered a key to life, Europa is regarded as one of the most promising places in the search for extraterrestrial life.