Tardigrades are very sensitive to changes in oxygen tension and prolonged reduction of oxygen leads to osmoregulatory failure. Unlike other types of cryptobiosis, anoxybiosis involves the uptake of water and the animals become turgid. Revival time is directly proportional to duration of the dormant state. While in a state of cryptobiosis organisms are able to resist environmental extremes that would be instantly lethal to the animal if in the active state. In the 1920's P. G. Rahm of the University of Freidburg discovered tardigrades were able to withstand being heated for a few minutes in 151 degrees Celsius and survive being chilled for days in temperatures up to minus 200 degrees Celsius.
Water bears are also resistant to vacuums.
Specimens exposed to high vacuum and electron bombardment in a SEM for 0.5 hours were then revived and survived for a few minutes before dying. As science obtains a better understanding of biological processes we must at times re-examine previous beliefs or understandings. This is perhaps exemplified by cryptobiosis. The issue pertains to the question of whether or not tardigrades can die and come back to life. The answer is no.