As Ganymede passes behind the gas giant, light from the planet bounces off the moon, carrying with it clues about the chemicals that make up the haze above the Jovian clouds.

• 更深处被认为存在一个液体铁芯，为太阳系中卫星周围唯一磁场提供动力。木卫三每7天环绕木星一周，它的轨道倾斜几乎与地球正面相对。