User talk:Robertinventor/Planetary protection - mid edit

Planetary protection is a guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth. Planetary protection reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail.

There are two types of interplanetary contamination. Forward contamination is the transfer of viable and reproducing life from Earth to another celestial body. A major goal of planetary protection is to preserve the planetary record of natural processes by preventing introduction of Earth originated life. Back contamination refers to the possibility of contamination of Earth by any extraterrestrial organisms into the Earth's biosphere, if such exist.

Origins in the Outer Space Treaty
The legal basis for Planetary Protection lies in the Outer Space Treaty (1967), particularly Article IX.

This treaty has been signed by almost all nations including the main space faring nations. For forward contamination, the phrase to be interpreted is "harmful contamination", which could have varying meanings. However, an unofficial legal review concluded that Article IX must mean that “any contamination which would result in harm to a state’s experiments or programs is to be avoided”, and this is how it has come to be interpreted.

COSPAR recommendations
The Committee on Space Research (COSPAR) translates these considerations into recommendations for avoiding interplanetary contamination. Recommendations are tailored to the type of space mission—from planetary flybys to probe landings—and celestial body explored. COSPAR categorizes the missions into 5 groups:
 * Category I: Any mission to the Sun, Mercury, other locations not of interest for studying prebiotic chemistry or the origin and evolution of life.
 * Category II: Any mission to the Earth's Moon, Venus, comets, Jupiter, Pluto/Charon, Kuiper Belt Objects, other locations of interest for studying prebiotic chemistry and the origin of life but for which there is an insignificant probability of contamination with Earth life.
 * Category III: Flyby and orbiter missions to locations with the potential to host life and for which there is a possibility of contamination by Earth life; e.g., Mars, Europa, Titan or Enceladus.
 * Category IV: Lander or probe missions to locations with the potential to host life and for which there is a possibility of contamination by Earth life; e.g., Mars, Europa, Titan or Enceladus. Missions to Mars in category IV are subclassified further:
 * Category IVa. Landers that do not search for Martian life - same as Viking pre-sterilization levels, 300,000 spores per spacecraft and 300 spores per square meter.
 * Category IVb. Landers that search for Martian life. Adds stringent extra requirements to prevent contamination of samples.
 * Category IVc. Any component that accesses a Martian Special Region (see below) must be sterilized to at least to the Viking post-sterilization biological burden levels.
 * Category V: Any earth return mission. Missions returning samples from locations with the potential to support life are considered 'Restricted Earth Return' and returned samples must be contained at levels more stringent than Biosafety level 4. Samples from locations judged unlikely to support life are considered 'Unrestricted Earth Return' and merit no constraints for planetary protection purposes.

After receiving the mission category a certain level of biological burden is allowed for the mission. In general this is expressed as a 'probability of contamination', but in the case of Mars this has been translated into a metric for the number of Bacillus spores per surface area and present in total on or within the spacecraft: 300 spores per m² free surface, but not more than 300,000 spores in total (category IVa). These amounts are ten thousand times less if the lander is in category IVc (a maximum of 30 spores total). Any sample-return vehicle must then be designed such that the sample is returned in highly reliable containers with measures in place to dispose of any parts of the vehicle which could have been contaminated before re-entry into the Earth's atmosphere.

Mars Special Regions
A Special Region is a region classified by COSPAR within which terrestrial organisms could readily propagate, or one thought to have an elevated potential for existence of Martian life forms. This is understood to apply to any region on Mars where liquid water occurs, or can occasionally occur, based on the current understanding of requirements for life.

If a hard landing risks biological contamination of a Special Region, then the whole lander system must be sterilized to COSPAR category IVc.

History
The potential problem of lunar and planetary contamination was first raised at the International Astronautical Federation VIIth Congress in Rome in 1956.

In 1958 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 lead 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. Mars and possibly Venus need to remain uncontaminated only until study by manned ships becomes possible” In 1959 planetary protection was transferred to the newly formed Committee on Space Research (COSPAR). COSPAR in 1964 issued Resolution 26 (COSPAR, 1964, p. 26), which

In 1967, most of the world's nations ratified the United Nations Outer Space Treaty. The policy of protecting pristine celestial environments is accepted with virtual unanimity, and has been incorporated into positive international law. The treaty's planetary protection provisions stipulate that nations shall "pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter."

The United Nations incorporated these provisions in its 1979 Moon Treaty governing the activities of states on the Moon and other celestial bodies, and in the Vienna Declaration of 1999. . The Moon Treaty however has not been ratified by any space faring nation to date.

Decontamination procedures
The aim of the current regulations is to keep the number of micro-organisms low enough so that the probability of contamination of Mars (and other targets) is acceptable. It is not an objective to make the probability of contamination zero.

The guidelines were originally drawn up on the basis that the aim is to keep the probability of contamination during the entire period of the historical exploration of Mars to 1 chance in 10000, a somewhat arbitrarily chosen number.

The risk of forward contamination by terrestrial micro-organisms depends on their ability to survive the voyage and on the environmental conditions they find on arrival. Measures currently in use for scientific exploration include dry-heating of satellites, sterilizing wipes and aseptic integration of components. These add a significant burden to mission designers and integration teams. The spacecraft must be sterilized before leaving Earth in order to minimize the risk of depositing Earth-originating biological material at the destination. Heat energy, administered in the form of an elevated temperature heat soak over a specific interval of time, is a well-known method for inactivating organisms. Clean room assembly and microbial reduction through heat, chemicals or radiation are the basic techniques used to accomplish microbial control when this is necessary for a mission. NASA currently has only one approved method – dry heat microbial reduction. This technique was used on the Viking Mars landers, which were built and launched in the 1970s. Advanced materials, electronics, and other heat-sensitive equipment being used on spacecraft today could be damaged by such high-temperature treatment, however. Consequently, NASA researchers are developing an alternative sterilization method, a low-temperature, vapor-phase, hydrogen peroxide-based sterilization process.

Spore counts and other methods to verify sterilization
The spore count is used as an indirect measure of the number of micro-organisms present. Typically 99% of micro-organisms by species will be non spore forming and able to survive in dormant states, and so the actual number of viable dormant micro-organisms remaining on the sterilized spacecraft is expected to be many times the number of spore forming micro-organisms.

Some studies that suggest that the spore count method has limitations as an assay method, since often surfaces with the lowest or even zero spore count have similar numbers of micro-organisms to surfaces with higher spore counts.

Two methods being considered for near-term submission to NASA for use on spacecraft are Limulus Amebocyte Lysate assay, and Adenosine Triphosphate assay.