One of the keys to the success of Tardigrades is the presence of a cellular sugar called Trehalose which preserves the membranes that form their bodies. Furthermore, when Tardigrades dry up, they become "tuns", little capsules that are easily transported and dispersed over the earth via the wind, the oceans, or in an animals gut. Moreover, they can go without oxygen for a time and withstand temperatures ranging from well above waters boiling point to nearly absolute zero. Have been known to survive one degree above zero for several minutes. In addition, due to Encystment, Tardigrades can also survive as high as 5,000 grays or 500,000 rads of ionizing radiation. Humans can suffer massive damages if they are exposed to even 1,000-2,000 rads.