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Listen to part of a lecture in an astronomy class. The professor is discussing the possibility of life on Jupiter's moon Europa. Professor: For decades, scientists have speculated about life beyond Earth, and one of the most intriguing candidates in our solar system is Europa, one of Jupiter's large moons. Unlike Mars, which has a dry, barren surface, Europa is covered by a thick layer of ice. However, beneath that ice, there is strong evidence for a vast liquid ocean. How do we know this? Well, spacecraft flybys have detected a magnetic field that suggests a conductive layer, likely salty water, beneath the surface. Also, images show cracks and ridges on the ice, which indicate tidal flexing—the moon is stretched and squeezed by Jupiter's gravity, generating heat. This heat could keep the ocean liquid. So, why does this matter? On Earth, we find life in extreme environments, such as deep-sea hydrothermal vents, where sunlight never reaches. These ecosystems thrive on chemical energy. If Europa has similar conditions—liquid water, heat, and chemical nutrients—it might support microbial life. Some researchers even propose that plumes of water vapor, detected by telescopes, could be sampled by future missions to test for organic molecules. Clearly, Europa has become a priority target for astrobiology.