Planetary protection
The potential problem of lunar and planetary contamination was first raised at the International Astronautical Federation VIIth Congress in Rome in 1956.
[4] In 1958[5] the U.S. National Academy of Sciences (NAS) passed a resolution stating, “The National Academy of Sciences of the United States of America urges that scientists plan lunar and planetary studies with great care and deep concern so that initial operations do not compromise and make impossible forever after critical scientific experiments.” This led to creation of the ad hoc Committee on Contamination by Extraterrestrial Exploration (CETEX), which met for a year and recommended that interplanetary spacecraft be sterilized, and stated, “The need for sterilization is only temporary.
NASA policy states explicitly that “the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized”.
[12] The Committee on Space Research (COSPAR) meets every two years, in a gathering of 2000 to 3000 scientists,[13] and one of its tasks is to develop recommendations for avoiding interplanetary contamination.
Other procedures required, depending on the mission, may include trajectory biasing, the use of clean rooms during spacecraft assembly and testing, bioload reduction, partial sterilization of the hardware having direct contact with the target body, a bioshield for that hardware, and, in rare cases, complete sterilization of the entire spacecraft.
Since sterilization of the returned samples would destroy much of their science value, current proposals involve containment and quarantine procedures.
If a hard landing risks biological contamination of a special region, then the whole lander system must be sterilized to COSPAR category IVc.
The 2009 COSPAR Workshop on Planetary Protection for Outer Planet Satellites and Small Solar System Bodies covered this in some detail.
This workshop also gave more precise definitions for some of the categories:[23][24] “not of direct interest for understanding the process of chemical evolution or the origin of life.” [25]… where there is only a remote chance that contamination carried by a spacecraft could jeopardize future exploration”.
In this case we define “remote chance” as “the absence of niches (places where terrestrial microorganisms could proliferate) and/or a very low likelihood of transfer to those places.” [23][25]Provisionally, they assigned these objects to Category II.
However, they state that more research is needed, because there is a remote possibility that the tidal interactions of Pluto and Charon could maintain some water reservoir below the surface.
"[25]In the category V for sample return the conclusions so far are:[25] The aim of the current regulations is to keep the number of microorganisms low enough so that the probability of contamination of Mars (and other targets) is acceptable.
[19] This figure is obtained typically by multiplying together the number of microorganisms on the spacecraft, the probability of growth on the target body, and a series of bioload reduction factors.
For example, the thickness of the surface ice of Europa is unknown, and may be thin in places, which can give rise to a high level of uncertainty in the equation.
We call this concept the natural contamination standard.Another approach for Europa is the use of binary decision trees which is favoured by the Committee on Planetary Protection Standards for Icy Bodies in the Outer Solar System under the auspices of the Space Studies Board.
The Apollo era quarantine procedures are of interest as the only attempt to date of a return to Earth of a sample that, at the time, was thought to have a remote possibility of including extraterrestrial life.
[46] For all spacecraft missions requiring decontamination, the starting point is clean room assembly in US federal standard class 100 cleanrooms.
Sensitive electronics such as the core box of the rover including the computer, are sealed and vented through high-efficiency filters to keep any microbes inside.
Problems encountered include nanoscale features only a few atoms thick, plastic packaging, and conductive epoxy attachment methods.
[53][54][55][56] For example, in a recent study, microbes from swabs of the Curiosity rover were subjected to desiccation, UV exposure, cold and pH extremes.
Alberto G. Fairén and Dirk Schulze-Makuch published an article in Nature recommending that planetary protection measures need to be scaled down.
[68][69][70] Earth receives a steady stream of meteorites from Mars, but they come from relatively few original impactors, and transfer was more likely in the early Solar System.
The NRC concluded that though transfer is possible, the evidence from meteorite exchange does not eliminate the need for back contamination protection methods.
Impactors of 10 km across or larger can send debris to Mars through the Earth's atmosphere but these occur rarely, and were more common in the early Solar System.
Recommendations of the workshop include: Recommendation 3 COSPAR should add a separate and parallel policy to provide guidance on requirements/best practices for protection of non-living/nonlife-related aspects of Outer Space and celestial bodiesSome ideas proposed include protected special regions, or "Planetary Parks"[81] to keep regions of the Solar System pristine for future scientific investigation, and also for ethical reasons.
In the 2010 workshop one of the recommendations for future consideration was to extend the period for contamination prevention to the maximum viable lifetime of dormant microorganisms introduced to the planet.
"[84]In July 2018, the National Academies of Sciences, Engineering, and Medicine issued a Review and Assessment of Planetary Protection Policy Development Processes.
[89][90] Gros argues that the extended timescales of interstellar missions imply that planetary and exoplanetary protection have different ethical groundings.
[91] "This protocol was defined in concert with Viking, the first mission to face the most stringent planetary protection requirements; its implementation remains the gold standard today.
"A policy review of the Outer Space Treaty concluded that, while Article IX "imposed international obligations on all state parties to protect and preserve the environmental integrity of outer space and celestial bodies such as Mars," there is no definition as to what constitutes harmful contamination, nor does the treaty specify under what circumstances it would be necessary to "adopt appropriate measures" or which measures would in fact be "appropriate" An earlier legal review, however, argued that "if the assumption is made that the parties to the treaty were not merely being verbose" and "harmful contamination" is not simply redundant, "harmful" should be interpreted as "harmful to the interests of other states," and since "states have an interest in protecting their ongoing space programs," Article IX must mean that "any contamination which would result in harm to a state’s experiments or programs is to be avoided" Current NASA policy states that the goal of NASA’s forward contamination planetary protection policy is the protection of scientific investigations, declaring explicitly that "the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized""The best that I hear now is that the techniques of isolation we used wouldn’t be adequate for a sample coming back from Mars, so somebody else has a big job on their hands."
