Interplanetary contamination

• 1. Defining Contamination Types

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  Forward contamination describes the transfer of life from Earth to another celestial body. Back contamination covers the introduction of extraterrestrial organisms into Earth's biosphere. It also includes infection of humans and human habitats in space by extraterrestrial organisms if such organisms exist. The main focus remains on microbial life and potentially invasive species. Non-biological forms of contamination have also been considered, including sensitive deposits like lunar polar ice. In the case of back contamination, multicellular life is thought unlikely but has not been ruled out. Forward contamination by multicellular life becomes a consideration only for crewed missions to Mars.

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• 2. Potential Habitats And Survival

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  Enceladus shows geysers made primarily of salt-rich particles with an ocean-like composition. Heat scans indicate temperatures reaching negative 93 degrees Celsius around fissures where these geysers originate. Europa possesses indirect evidence for its subsurface ocean through tidal heating models. Observations by the Galileo spacecraft strengthened the case for liquid water deep within Europa. Some bacterial spores from Earth were transported on Mars spacecraft. Spores of Bacillus pumilus SAFR-032 survived exposure to vacuum and cosmic radiation when sheltered against solar UV rays. About 50 percent or more of those subjected to other space conditions survived. Certain lichens from arctic permafrost can photosynthesize without liquid water using atmospheric humidity. They are highly tolerant of UV radiation using melanin and specialized chemicals. Research published in July 2017 showed perchlorates become even more lethal to bacteria under simulated Martian UV flux. The surface of Mars is now considered more uninhabitable than previously thought due to toxic reactive oxygen species formed by abraded silicates.

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• 3. Sterilization Protocols And Policies

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  NASA made sterilization policies official with Management Manual NMI-4-4-1 on the 9th of September 1963. Prior to this manual, all outgoing spacecraft required the same sterilization requirements regardless of target. Difficulties in sterilizing Ranger probes sent to the Moon drove NASA to change to a target-by-target basis. Destinations like Mercury need no precautions at all while others such as the Moon require documentation but nothing more. Missions to Mars require sterilization of rovers sent there. Back contamination would be prevented by containment or quarantine since Apollo regulations have been rescinded. New regulations for sample returns remain undeveloped. Forward contamination prevention relies primarily on sterilizing spacecraft before launch. Sample return missions aim to bring extraterrestrial samples back to Earth where sterilization would make them less interesting scientifically. Containment breaks the chain of contact between the planet of origin and Earth. Quarantine procedures apply to materials and anyone who comes into contact with them.

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• 4. Crewed Mission Risks And Ethics

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  Human explorers may be potential carriers back to Earth of microorganisms acquired on Mars if such microorganisms exist. Humans are typically host to one hundred trillion microorganisms across ten thousand species in the human microbiome. These cannot be removed while preserving human life. Containment seems the only option yet effective containment appears difficult to achieve with present-day technology. Adequate containment during hard landings remains a major challenge. The Apollo 13 mission included an anti-bacterial filter in the Lunar Module cabin relief valve from that point onward. This filter prevented contaminants from the cabin being released into the lunar environment during depressurization prior to EVA. Public concern about microbes on the Moon incited thousands of letters to NASA after Apollo 11. Astronauts could transmit Martian biological entities or disease to fellow astronauts upon returning to Earth. A contaminated vehicle returned to Earth could also serve as a source of contamination. Water supply contamination by Earth microorganisms shed by humans in stools, skin, and breath affects long-term colonization plans.

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• 5. Sample Return Containment Strategies

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  NASA proposed building a biohazard containment facility tentatively known as the Mars Sample Return Receiving Facility. This future facility must be rated biohazard level four. Existing BSL-4 facilities deal primarily with well-known organisms but this new facility requires careful pre-planning for unforeseen issues. It should filter particles of 0.01 micrometers or larger since release of any particle 0.05 micrometers or larger is unacceptable under any circumstance. Gene transfer agents are virus-like particles produced by some microorganisms that package random segments of DNA capable of horizontal gene transfer. In one experiment reported in 2010 researchers found up to 47 percent of bacteria incorporated genetic material from GTAs overnight. Ultramicrobacteria discovered as small as 0.2 micrometers across further justify strict size limits. The facility must double as a cleanroom to preserve scientific value while containing unknown biohazards. Compartmentalization solutions include triple-walled containment facilities and extensive robotic handling of samples. The facility would take seven to ten years from design to completion plus two additional years for staff training.

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• 6. Legal Frameworks And Public Debate

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  Margaret Race examined the legal process of approval for a Mars sample return mission in detail. Under the National Environmental Policy Act, which did not exist during the Apollo era, a formal environmental impact statement is likely required. Public hearings will air all issues openly over several years. Worst accident scenarios and project alternatives play out in the public arena. Other agencies such as the Environment Protection Agency might also get involved in decision-making processes. Laws on quarantine need clarification since Apollo regulations were rescinded. NASA delayed announcement of its quarantine regulations until the day Apollo was launched bypassing public debate requirements. This approach would likely not be tolerated today. Presidential directive NSC-25 applies requiring review of large-scale alleged effects on the environment through long processes leading eventually to presidential approval. Numerous international regulations and treaties require negotiation regarding environmental protection and health. The public has a significant role to play in developing policies governing future sample returns.

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• 7. In Situ Detection Technologies

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  NASA Marshall Space Flight Center leads research to develop a Miniaturized Variable Pressure Scanning Electron Microscope for lunar and Martian missions. Several teams including Jonathan Rothberg and J. Craig Venter are separately developing solutions for sequencing alien DNA directly on the Martian surface itself. Levin works on updated versions of the Labeled Release instrument flown on Viking that rely on detecting chirality. The Urey Mars Organic and Oxidant Detector instrument was designed with much higher levels of sensitivity than any previous instruments. It was due to fly on ExoMars in 2018 before being descoped. Telerobotic approaches permit direct study of samples on the Mars surface via telepresence from orbit. Astronauts have near real-time control of robots and can respond immediately to discoveries. Telepresence prevents contamination both ways while offering mobility benefits. Return of the sample to orbit permits analysis without delay to detect volatiles lost during voyage home. Similar methods could explore other biologically sensitive moons such as Europa, Titan, or Enceladus once human presence becomes possible.

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