Evidence of liquid water on Enceladus began to accumulate in 2005, when scientists observed plumes containing water vapor spewing from its south polar surface, with jets moving 250 kg of water vapor every second at up to into space. Soon after, in 2006 it was determined that Enceladus's plumes are the source of Saturn's E Ring. The sources of salty particles are uniformly distributed along the tiger stripes, whereas sources of "fresh" particles are closely related to the high-speed gas jets. The "salty" particles are heavier and mostly fall back to the surface, whereas the fast "fresh" particles escape to the E ring, explaining its salt-poor composition of 0.5–2% of sodium salts by mass.