Scientists have developed a theory as to what is causing the mysterious water plumes discovered on the Saturn moon Enceladus. Every time the moon twirls around Saturn, a period of 1.37 days, gravitational forces stretch and compress the icy crust on the moon's surface. The resulting heat and pressure works on fissures known as "tiger stripes", liquefying enough water to create the jets visible in various Cassini pictures of the moon. While it does indicate there is liquid water somewhere on the moon, it most likely is very deep, on the order of several miles. This considerably complicates any attempt to sample or explore this potential source of extra-terrestrial liquid water.