The tardigrade Milnesium tardigradum demonstrated its ability to survive the vacuum and ultraviolet radiation of space in the TARDIS experiment on the 2007 FOTON-M3 mission.
When dried, terrestrial tardigrades draw in their legs and go into a cryptobiotic 'tun' state. They quickly revive when re-wetted.[1]
Tardigrades are small arthropods able to tolerate extreme environments. Many live in tufts of moss, such as on rooftops, where they get repeatedly dried out and rewetted. Others live in the Arctic or atop mountains, where they are exposed to cold. When dried, they go into a cryptobiotic 'tun' state in which metabolism is suspended.[2][3] They have been described as the toughest animals on Earth.[3]
Proposals
In 1964, R.M. May and colleagues proposed that the tardigrade Macrobiotus areolatus would be a suitable model organism for space experiments because of its exceptional radiation tolerance.[3][4]
In 2001, R. Bertolani and colleagues proposed tardigrades as a model for a study of animal survival in space.[3][5] As terrestrial experiments on tardigrades proceeded, knowledge of their survival abilities grew, enabling K.I. Jönsson in 2007,[6] and then other researchers such as Daiki Horikawa in 2008[7] and Roberto Guidetti in 2012,[8] to present evidence that they would resist desiccation, radiation, heat, and cold, suiting them for astrobiology studies.[3]
In 2008, F. Ono and colleagues suggested that tardigrades might be able to survive a journey through space on a meteorite, enabling panspermia, the transfer of life from one planet to another.[9]
Missions
BIOPAN on FOTON-M3, 2007
The 2007 FOTON-M3 mission carrying the BIOPAN astrobiology payload (illustrated) exposed tardigrades to vacuum, solar ultraviolet, or both, showing their ability to survive in the space environment.
Tardigrades have survived exposure to space. In 2007, dehydrated tardigrades were taken into low Earth orbit on the FOTON-M3 mission carrying the BIOPAN astrobiology payload. For 10 days, in the "Tardigrade Resistance to Space Effects" (TARSE) experiment, groups of Paramacrobiotus richtersi tardigrades, some of them previously dehydrated, some of them not, were exposed to the hard vacuum of space, or vacuum and solar ultraviolet radiation.[10] Back on Earth, more than 68% of the subjects protected from solar ultraviolet radiation were reanimated within 30 minutes following rehydration; although subsequent mortality was high, many produced viable embryos.[3][10]
In contrast, in the "Tardigrades in Space" (TARDIS) experiment, hydrated samples exposed to the combined effect of vacuum and full solar ultraviolet radiation had significantly reduced survival, with only three subjects of Milnesium tardigradum surviving.[10] The space vacuum did not much affect egg-laying in either Richtersius coronifer or M. tardigradum, whereas UV radiation did reduce egg-laying in M. tardigradum.[3][11]
The third FOTON-M3 experiment, "Rotifers, Tardigrades and Radiation" (RoTaRad) focused mainly on radiation survival.[3]
LIFE prototype on STS-134, 2011
In 2011, Angela Maria Rizzo and colleagues sent tardigrades on board the International Space Station Endeavour along with extremophiles on STS-134, in the "Tardigrades in Space" (TARDIKISS) experiment.[3][12] They concluded that microgravity and cosmic radiation "did not significantly affect survival of tardigrades in flight" and that tardigrades were useful in space research,[13][14] with implications for astrobiology, where they should be suitable model organisms.[15][8][16]
Model of the Beresheet Moon lander which crashed, probably destroying its tardigrade payload[17]
In 2019, a capsule containing tardigrades in a cryptobiotic state was on board the Israeli lunar landerBeresheet which crashed on the Moon. They were described as unlikely to have survived the impact because the shock pressure of the crash would have been well above the 1.14 GPa that they have been measured as surviving.[17][23] Despite tardigrades' ability to survive in space, tardigrades on Mars would still need food.[24] The possibility that tardigrades survived the crash attracted concern about contamination of the Moon with biological material.[25] However, they are unlikely to become rehydrated because of the lack of liquid water on the Moon.[26]
^May, R.M.; Maria, M.; Guimard, J. (1964). "Actions différentielles des rayons x et ultraviolets sur le tardigrade Macrobiotus areolatus, a l'état et desséché" [Differential effects of X-rays and ultraviolet on the tardigrade Macrobiotus areolatus, in active and dried states]. Bulletin Biologique France Belgique (in French) (98): 349–367.
^Bertolani, R.; Rebecchi, L.; Jönsson, K.I.; Borsari, S.; Guidetti, R.; Altiero, T. (2001). Monti, R.; Bonifazi, C. (Eds.), La Scienza e la Tecnologia Spaziale sulla Stazione Internazionale (ISS) (eds.). "Tardigrades as a model for experiences of animal survival in the space". MSSU—Micro Space Station Util (2). Special Issue ASI National Workshop, Turin, 2001: 211–212.{{cite journal}}: CS1 maint: multiple names: editors list (link)
^ abGuidetti, Roberto; Rizzo, Angela Maria; Altiero, Tiziana; Rebecchi, Lorena (2012). "What can we learn from the toughest animals of the Earth? Water bears (tardigrades) as multicellular model organisms in order to perform scientific preparations for lunar exploration". Planetary and Space Science. 74 (1): 97–102. doi:10.1016/j.pss.2012.05.021.
^Ono, F.; Saigusa, M.; Uozumi, T.; Matsushima, Y.; Ikeda, H.; Saini, N.L.; Yamashita, M. (2008). "Effect of high hydrostatic pressure on to life of the tiny animal tardigrade". Journal of Physics and Chemistry of Solids. 69 (9): 2297–2300. doi:10.1016/j.jpcs.2008.04.019.
^Gabriel, Willow N.; McNuff, Robert; Patel, Sapna K.; Gregory, T. Ryan; Jeck, William R.; Jones, Corbin D.; Goldstein, Bob (2007). "The tardigrade Hypsibius dujardini, a new model for studying the evolution of development". Developmental Biology. 312 (2): 545–559. doi:10.1016/j.ydbio.2007.09.055. PMID17996863.
