The survival of some microorganisms exposed to outer space has been studied using both simulated facilities and low Earth orbit exposures. Bacteria were some of the first organisms investigated, when in 1960 a Russian satellite carried Escherichia coli, Staphylococcus, and Enterobacter aerogenes into orbit.^[1] Many kinds of microorganisms have been selected for exposure experiments since, as listed in the table below.

Experiments of the adaption of microbes in space have yielded unpredictable results. While sometimes the microorganism may weaken, they can also increase in their disease-causing potency.^[1]

It is possible to classify these microorganisms into two groups, the human-borne and the extremophiles. Studying the human-borne microorganisms is significant for human welfare and future crewed missions in space, whilst the extremophiles are vital for studying the physiological requirements of survival in space.^[2] NASA has pointed out that normal adults have ten times as many microbial cells as human cells in their bodies.^[3] They are also nearly everywhere in the environment and, although normally invisible, can form slimy biofilms.^[3]

Extremophiles have adapted to live in some of the most extreme environments on Earth. This includes hypersaline lakes, arid regions, deep sea, acidic sites, cold and dry polar regions and permafrost.^[4] The existence of extremophiles has led to the speculation that microorganisms could survive the harsh conditions of extraterrestrial environments and be used as model organisms to understand the fate of biological systems in these environments. The focus of many experiments has been to investigate the possible survival of organisms inside rocks (lithopanspermia),^[2] or their survival on Mars for understanding the likelihood of past or present life on that planet.^[2] Because of their ubiquity and resistance to spacecraft decontamination, bacterial spores are considered likely potential forward contaminants on robotic missions to Mars. Measuring the resistance of such organisms to space conditions can be applied to develop adequate decontamination procedures.^[5]

Research and testing of microorganisms in outer space could eventually be applied for directed panspermia or terraforming.

Table

  indicates testing conditions

Organism	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions	References
Bacteria & bacterial spores
Actinomyces erythreus					[6]
Aeromonas proteolytica					[7]
Anabaena cylindrica (akinetes)					[8]
Azotobacter chroococcum					[9]
Azotobacter vinelandii					[10]
Bacillus cereus					[11]
Bacillus megaterium					[12]
Bacillus mycoides					[13]
Bacillus pumilus					[13][14]
Bacillus subtilis					[15][16][17][18][19]
Bacillus thuringiensis					[7]
Carnobacterium					[20]
Chroococcidiopsis					[21][22][23][24]
Clostridium botulinum					[12]
Clostridium butyricum					[25][26]
Clostridium celatum					[26]
Clostridium mangenotii					[26]
Clostridium roseum					[26]
Deinococcus aerius					[27]
Deinococcus aetherius					[28]
Deinococcus geothermalis					[29]
Deinococcus radiodurans					[30][31][32][33][34]
Enterobacter aerogenes					[35]
Escherichia coli					[12][26][36][37]
Gloeocapsa					[24]
Gloeocapsopsis pleurocapsoides					[38]
Haloarcula-G					[39]
Hydrogenomonas eutropha					[36]
Klebsiella pneumoniae					[12]
Kocuria rosea					[40]
Lactobacillus plantarum					[41]
Leptolyngbya					[38]
Luteococcus japonicus					[42]
Micrococcus luteus					[42]
Nostoc commune					[24][43]
Nostoc microscopicum					[38]
Photobacterium					[42]
Pseudomonas aeruginosa					[3][41]
Pseudomonas fluorescens					[41]
Rhodococcus erythropolis					[44]
Rhodospirillum rubrum					[10]
Salmonella enterica					[45]
Serratia marcescens					[11]
Serratia plymuthica					[46]
Staphylococcus aureus					[25][41]
Streptococcus mutans					[47]
Streptomyces albus					[41]
Streptomyces coelicolor					[47]
Synechococcus (halite)					[39][48][49]
Synechocystis					[50]
Symploca					[38]
Tolypothrix byssoidea					[38]
Archaea	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
Halobacterium noricense					[51][52]
Halobacterium salinarum					[47]
Halococcus dombrowskii					[51]
Halorubrum chaoviatoris					[49][53]
Methanosarcina sp. SA-21/16					[54]
Methanobacterium MC-20					[54]
Methanosarcina barkeri					[54]
Fungi and algae	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
Aspergillus niger					[42]
Aspergillus oryzae					[30][42]
Aspergillus terreus					[55]
Aspergillus versicolor					[56]
Chaetomium globosum					[7]
Cladosporium herbarum					[57]
Cryomyces antarcticus					[58][59]
Cryomyces minteri					[58]
Euglena gracilis					[60][61][62][63]
Mucor plumbeus					[42]
Nannochloropsis oculata					[64][65][66]
Penicillium roqueforti					[15]
Rhodotorula mucilaginosa					[42]
Sordaria fimicola					[67]
Trebouxia					[68]
Trichoderma koningii					[53]
Trichoderma longibrachiatum					[69]
Trichophyton terrestre					[7]
Ulocladium atrum					[18]
Lichens	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
Aspicilia fruticulosa					[70]
Buellia frigida					[71]
Circinaria gyrosa					[68][72]
Rhizocarpon geographicum					[68][73]
Rosenvingiella					[24]
Xanthoria elegans					[74][75][76][77][78]
Xanthoria parietina					[75]
Bacteriophage / virus	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
T7 phage					[7]
Canine hepatitis					[79]
Influenza PR8					[79]
Tobacco mosaic virus					[47][79]
Vaccinia virus					[79]
Yeast	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
Rhodotorula rubra					[7]
Saccharomyces cerevisiae					[7]
Saccharomyces ellipsoides					[36]
Zygosaccharomyces bailii					[36]
Animals	Low Earth orbit	Impact event and planetary ejection	Atmospheric reentry	Simulated conditions
Caenorhabditis elegans (nematode)					[80][81]
Hypsibius dujardini (tardigrade)					[82][83]
Milnesium tardigradum (tardigrade)					[84][85][86]
Richtersius coronifer (tardigrade)					[84][87]
Mniobia russeola (rotifer)					[87]