In Greek mythology, a young woman seduced by Zeus, who then transformed her into a heifer to protect her from his jealous wife. Also, the closest, largest moon of Jupiter. I, Marcy 4, 1979.
Bright patches are likely due to sulfur dioxide ice and gas jetted from fractures in surface.
Dark spots are pools of molten sulfur. Each image is a composite of frames taken at near-ultraviolet, violet, and yellow wavelengths. In Greek mythology, a mistress of Zeus to whom he appeared as a gentle white heifer. Zeus persuaded her to take a ride on his back, and then he carried her away across the sea. Also, the second of Jupiter's large moons.