Planetary protection
Encyclopedia
Planetary protection is the term used to describe a guiding principle in design of an interplanetary mission
that aims to prevent biological contamination of both the target celestial body
and the Earth. This principle arises from the scientific need to preserve planetary conditions for future biological and organic constituent exploration – especially exobiology/astrobiology
. The incorporation of geoethical issues in planetary and space research and astrobiology widens the classical concept of Planetary protection, considering, besides the organics-bearing perspective, the abiotic nature and all features of the planetary bodies and their planetary geodiversity. It also aims to protect the Earth and its biosphere from potential extraterrestrial
sources of contamination in the event of a sample return mission. The need for planetary protection measures is strongest for missions designed to return a sample of another planet or celestial body to the earth.
The Committee on Space Research
categorizes the missions into 5 groups:
This classification can change due to new scientific knowledge.
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 3E5 spores in total (category IVa). The amount should be ten thousand times less if area of special protection should be visited.
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.
The discovery of extremophiles on Earth surviving temperatures that we previously thought to be lethal to all life demonstrate how difficult it can be to prevent biological contamination. It is widely claimed that a common bacterium, Streptococcus mitis
, was found to have accidentally contaminated the Surveyor 3
camera prior to launch and survived dormant in this harsh environment for two and a half years. However, this claim is no longer taken seriously by NASA (see Myth of Streptococcus mitis on the moon).
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. However, there is consensus that this is required to prohibit the possible microbial contamination of other planets.
Interplanetary mission
An interplanetary mission is a voyage or trip through space involving more than one planet. This is an important distinction because it requires significantly more ΔV than do missions within a single planetary system....
that aims to prevent biological contamination of both the target celestial body
Celestial Body
Celestial Body is a Croatian film directed by Lukas Nola. It was released in 2000....
and the Earth. This principle arises from the scientific need to preserve planetary conditions for future biological and organic constituent exploration – especially exobiology/astrobiology
Astrobiology
Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry,...
. The incorporation of geoethical issues in planetary and space research and astrobiology widens the classical concept of Planetary protection, considering, besides the organics-bearing perspective, the abiotic nature and all features of the planetary bodies and their planetary geodiversity. It also aims to protect the Earth and its biosphere from potential extraterrestrial
Extraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...
sources of contamination in the event of a sample return mission. The need for planetary protection measures is strongest for missions designed to return a sample of another planet or celestial body to the earth.
Process
The spacecraft must be sterilized before leaving Earth in order to minimize the risk of depositing Earth-originating biological material at the destination. The return vehicle must then be designed such that the sample is returned in highly reliable "bio-container" with measures in place to dispose of any parts of the vehicle which could have been contaminated before re-entry into the Earth's biosphere.The Committee on Space Research
COSPAR
The Committee on Space Research was established by the International Council for Science in 1958.Among COSPAR's objectives are the promotion of scientific research in space on an international level, with emphasis on the free exchange of results, information, and opinions, and providing a forum,...
categorizes the missions into 5 groups:
- Category I: Any mission to the SunSunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, MercuryMercury (planet)Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, other locations not of interest for studying prebiotic chemistry or the origin and evolution of life. - Category II: Any mission to the Earth's MoonMoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, VenusVenusVenus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, cometCometA comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s, JupiterJupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, PlutoPlutoPluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
/CharonCharon (moon)Charon is the largest satellite of the dwarf planet Pluto. It was discovered in 1978 at the United States Naval Observatory Flagstaff Station. Following the 2005 discovery of two other natural satellites of Pluto , Charon may also be referred to as Pluto I...
, 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., MarsMarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
, EuropaEuropa (moon)Europa Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and...
, TitanTitan (moon)Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
or EnceladusEnceladus (moon)Enceladus is the sixth-largest of the moons of Saturn. It was discovered in 1789 by William Herschel. Until the two Voyager spacecraft passed near it in the early 1980s very little was known about this small moon besides the identification of water ice on its surface...
. - 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., MarsMarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
, EuropaEuropa (moon)Europa Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and...
, TitanTitan (moon)Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
or EnceladusEnceladus (moon)Enceladus is the sixth-largest of the moons of Saturn. It was discovered in 1789 by William Herschel. Until the two Voyager spacecraft passed near it in the early 1980s very little was known about this small moon besides the identification of water ice on its surface...
. - 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.
This classification can change due to new scientific knowledge.
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
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...
spores per surface area and present in total on or within the spacecraft: 300 spores per m² free surface, but not more than 3E5 spores in total (category IVa). The amount should be ten thousand times less if area of special protection should be visited.
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.
The discovery of extremophiles on Earth surviving temperatures that we previously thought to be lethal to all life demonstrate how difficult it can be to prevent biological contamination. It is widely claimed that a common bacterium, Streptococcus mitis
Streptococcus mitis
Streptococcus mitis is a mesophilic alpha-hemolytic species of Streptococcus that inhabits the human mouth. It is a Gram positive, coccus, facultative anaerobe and catalase negative. It can cause endocarditis...
, was found to have accidentally contaminated the Surveyor 3
Surveyor 3
Surveyor 3 was the third lander of the American unmanned Surveyor program sent to explore the surface of the Moon. Launched on April 17, 1967, Surveyor 3 landed on April 20, 1967 at the Mare Cognitum portion of the Oceanus Procellarum...
camera prior to launch and survived dormant in this harsh environment for two and a half years. However, this claim is no longer taken seriously by NASA (see Myth of Streptococcus mitis on the moon).
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. However, there is consensus that this is required to prohibit the possible microbial contamination of other planets.
See also
- Forward-contaminationForward-contaminationForward-contamination is the contamination of other worlds with Terrestrial microbes. The risk of forward-contamination is twofold: that human beings may accidentally seed a previously sterile world, thus creating "extraterrestrials" that are really of terrestrial origin ; or that an...
- Back-contaminationBack-contaminationBack-contamination is the informal but widely employed name for the hypothetical introduction of microbial extraterrestrial organisms into Earth's biosphere. It is assumed that any such contact will be disruptive or at least have consequences over which human beings will have little control...
- Cassie ConleyCassie ConleyCatharine Anastasia Conley is NASA's Planetary Protection Officer.-Education:Conley received her Ph.D. in Plant Biology from Cornell University in 1994, and obtained a postdoctoral fellow position at The Scripps Research Institute studying proteins involved in muscle contraction...
, current NASANASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Planetary Protection Officer
General references
External links
- No bugs please, this is a clean planet! (ESA article)
- COSPAR planetary protection policy, July 2008 (COSPARCOSPARThe Committee on Space Research was established by the International Council for Science in 1958.Among COSPAR's objectives are the promotion of scientific research in space on an international level, with emphasis on the free exchange of results, information, and opinions, and providing a forum,...
article) - International Committee Against Mars Sample Return (ICAMSR website)
- NASA Planetary Protection Website
- JPL Develops High-Speed Test to Improve Pathogen Decontamination at JPL.
- Geoethics in Planetary and Space Exploration