Interplanetary contamination
So, back contamination would be prevented mainly by containment, and breaking the chain of contact between the planet of origin and Earth.
Some extremophiles may be able to survive space travel to another planet, and foreign life could possibly be introduced by spacecraft from Earth.
The majority of the species isolated are not well understood or characterized and cannot be cultured in labs, and are known only from DNA fragments obtained with swabs.
[9] Additionally, evolutionary processes on Earth might have developed biological pathways different from extraterrestrial organisms, and so may be able to outcompete it.
[10][11][12][13] Enceladus and Europa show the best evidence for current habitats, mainly due to the possibility of their hosting liquid water and organic compounds.
Certain lichens from the arctic permafrost are able to photosynthesize and grow in the absence of any liquid water, simply by using the humidity from the atmosphere.
[29] Laboratory simulations show that whenever multiple lethal factors are combined, the survival rates plummet quickly.
Research published in July 2017 shows that when irradiated with a simulated Martian UV flux, perchlorates become even more lethal to bacteria (bactericide effect).
[31][32] It was also found that abraded silicates (quartz and basalt) lead to the formation of toxic reactive oxygen species.
"[34] This research demonstrates that the present-day surface is more uninhabitable than previously thought,[31][35] and reinforces the notion to inspect at least a few meters into the ground to ensure the levels of radiation would be relatively low.
Measured data indicates that these geysers are made primarily of salt rich particles with an 'ocean-like' composition, which is thought to originate from a subsurface ocean of liquid saltwater, rather than from the moon's icy surface.
Models of how Europa is affected by tidal heating require a subsurface layer of liquid water in order to accurately reproduce the linear fracturing of the surface.
[39] Observations from the Hubble Space Telescope in December 2012 appear to show an ice plume spouting from Europa's surface,[40] which would immensely strengthen the case for a liquid subsurface ocean.
[42] Forward contamination is prevented by sterilizing space probes sent to sensitive areas of the Solar System.
Difficulties in the sterilization of Ranger probes sent to the Moon are the primary reasons for NASA's change to a target-by-target basis in assessing the likelihood forward contamination.
[8] The Apollo 11 missions incited public concern about the possibility of microbes on the Moon,[46] creating fears about a plague being brought to Earth when the astronauts returned.
[48] The Moon has been suggested as a testbed for new technology to protect sites in the Solar System, and astronauts, from forward and back contamination.
Currently, the Moon has no contamination restrictions because it is considered to be "not of interest" for prebiotic chemistry and origins of life.
Analysis of the contamination left by the Apollo program astronauts could also yield useful ground truth for planetary protection models.
[49][50] One of the most reliable ways to reduce the risk of forward and back contamination during visits to extraterrestrial bodies is to use only robotic spacecraft.
The possibility of new human pathogens, or environmental disruption due to back contamination, is considered to be of extremely low probability but cannot yet be ruled out.
The findings were that with present-day technology, Martian samples can be safely returned to Earth provided the right precautions are taken.
Solutions suggested include a triple walled containment facility, and extensive robotic handling of the samples.
[58] She found that under the National Environmental Policy Act (NEPA) (which did not exist in the Apollo era), a formal environment impact statement is likely to be required, and public hearings during which all the issues would be aired openly.
During this process, she found, the full range of worst accident scenarios, impact, and project alternatives would be played out in the public arena.
Apart from those domestic legal hurdles, there would be numerous international regulations and treaties to be negotiated in the case of a Mars sample-return, especially those relating to environmental protection and health.
Race concluded that the public of necessity has a significant role to play in the development of the policies governing Mars sample-return.
Past life is likely to be degraded by cosmic radiation over geological time periods if exposed in the top few meters of the Mars surface.
[84][86] Similar methods could be used to directly explore other biologically sensitive moons such as Europa, Titan, or Enceladus, once human presence in the vicinity becomes possible.
In August 2019, scientists reported that a capsule containing tardigrades (a resilient microbial animal) in a cryptobiotic state may have survived for a while on the Moon after the April 2019 crash landing of Beresheet, a failed Israeli lunar lander.
