User:Robertinventor/Debate about scientific value of Mars sample return and methods to avert low probability existential risks

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This article was created, but then was deleted again as a result of an AfD. Am keeping this original here for references and future use elsewhere in wikipedia.

There is a later version of it here: User:Robertinventor/Concerns for an early Mars sample return backup

There are several proposals for a Mars sample return mission (MSR) to bring back to Earth rock and dust samples from Mars to study. It is currently unknown whether or not life forms exist on Mars. If such life exists, a MSR could potentially transfer viable organisms resulting in a risk of back contamination — the introduction of extraterrestrial organisms into Earth's biosphere.

There is general agreement in the literature on the subject that, though the potential for large-scale negative effects appears to be very low, it is not demonstrably zero [1], and that the samples should be treated as biohazardous to the environment of Earth until shown to be safe. As a result all are agreed that these are matters of concern and need to be dealt with in any mission plans. There is a diversity of views however on how these concerns should be met.

It is agreed that a full and open public debate of the back contamination issues is needed at an international level before any sample return.[2] This is also a legal requirement..[3].


Prevailing View[edit | hide all | hide | edit source]

The prevailing view as shown in the official reports from the Space Studies Board[4] and the European Space Foundation[5][6] is as follows:

The risks of environmental disruption resulting from the inadvertent contamination of Earth with putative martian microbes are still considered to be low. But since the risk cannot be demonstrated to be zero, due care and caution must be exercised in handling any martian materials returned to Earth. [7]

The more recent ESF report has reduced the particle size limits for the containment from the previous report due to their decision that it is necessary to contain virus-type and GTA-type entities:

RECOMMENDATION 4: The ESF-ESSC Study Group concurs with the conclusions from NRC reports (1997, 2009) that large-scale effects arising from the intentional return of Mars materials to Earth are primarily those associated with replicating biological entities. However, bearing in mind new knowledge produced in recent years, the Study Group considers that, if there were Earth-like life forms on Mars, virus-type and GTA-type entities’ ability to interact with Earth organisms cannot be ruled out. Based on this, the ESF-ESSC Study Group recommends that not only self replicating free-living biological entities are considered as potentially having consequences on the Earth’s biosphere but also virus-type and GTA-type entities.

RECOMMENDATION 7: The probability that a single unsterilised particle of 0,01 µm diameter or greater is released into the Earth’s environment shall be less than 10-6[5] .

The reports concluded that a safe sample return is possible provided due caution is taken to reduce any chance of escape of particles, and provided that the sample return mission is designed to break the chain of contact with Mars for the exterior of the sample container.

The reports also recommend that a new type of Mars Sample Receiving Facility needs to be made to handle the samples on return to Earth. It has to function as a clean room as well as a biohazard containment facility. This requires a novel design challenges since the standard designs for clean rooms and biohazard containment are inconsistent with each other. Clean rooms require positive air pressure to keep contaminents out, and biohazard facilities require negative air pressure to keep biohazards in. Several preliminary designs have been drawn up for this facility.[8]

The NASA Office of Planetary Protection[9] work with mission planners to ensure compliance with NASA policy and international agreements, and has issued recommendations to deal with these issues.[10]

The current planetary protection office recommendation is that the facility should be operational at least two years prior to launch[11]. Preliminary studies have warned that it may take as many as 7 to 10 years to get it operational. [12]

The official reports stress the need for public debate at the international level due to the ethical issues involved.


Considering the global nature of the issue, consequences resulting from an unintended release could be borne by a larger set of countries than those involved in the programme. It is recommended that mechanisms dedicated to ethical and social issues of the risks and benefits raised by an MSR are set up at the international level and are open to representatives of all countries.[13]

The aim of this article is to present in detail some of the varying viewpoints on the risks and benefits of a Mars sample return, including minority views held by only one scientist or ethicist. These are all relevant to the international debate that will be required before a Mars Sample Return.

Plans to return a sample to Earth before detailed examination[edit | hide | edit source]

All concerned agree that Mars samples are of high scientific value, and are most easily studied in Earth laboratories.

NASA have no immediate plans for a MSR, but have considered proposals to return a Mars sample direct to Earth, possibly in the 2030s, in its Mars Next Generation program.[14][15]. [16]. China also has considered a plan to return a sample by 2030.[17]

Samples returned under these proposals would be examined for biosignatures on Mars first, but would not have any detailed examination such as with Scanning Electron Microscopes, DNA sequencers, or labelled culture experiments. Also they would not be tested for biohazard potential in Earth-like environments prior to return to Earth.

These plans depend on adequate containment of the samples during the return journey and in the receiving facility on Earth. The official studies have raised several concerns with this proposal and answered them with risk mitigation strategies. The prevailing view of most scientists and mission planners is that a sample return to Earth is both safe and desirable provided the recommended planetary protection precautions are taken.

There is general agreement in the published literature that we are not yet ready to receive a sample from Mars.[11]. The prevailng view is that provided planning starts early enough, we can be sufficiently ready to receive a sample by the time the mission is launched.

Criticism of these plans, and alternative proposals[edit | hide | edit source]

Some scientists in the ICAMSR, lead by Barry DiGreggorio are skeptical that adequate containment can be guaranteed when the samples are not yet understood, or are concerned about other issues such as human error breaking containment, potentially leading to back contamination [18][19][20][21] of Earth by accidentally released Martian micro-organisms.

Other scientists are critical of the science value of the mission. Jeffrey Bada has argued that it is hard to distinguish interesting from uninteresting samples for exobiology on a geological basis. The argument is that biological materials are easily degraded by surface conditions on Mars, particularly the UV radiation, and long term, by cosmic radiation. Without the ability to detect trace amounts of organics, and the ability to detect degradation of organics, he argues, there is a high chance of returning biologically uninteresting samples no more conclusive than the meteorite samples we already have from Mars.[22]

Others who advocate a vigorous "in situ" study on the Mars surface in place of a MSR, on issues of science value, include astrobiologist Dirk Schulze-Makuch, and Robert Zubrin, president of the Mars society.

Others while not criticizing a MSR as such, see greater value in "in situ" studies. Craig Venter argues that it is impossible to totally prevent contamination by Earth life during the return journey, so reducing their value for scientific research.[23]. Others argue that telerobotics provides a way to study samples on the surface of Mars without contamination issues, either way, while also eliminating problems due to loss of volatiles during the return journey to Earth. [24][25]

Alternative proposals include in situ study using rovers with new instruments, telerobotic study on the Mars surface, and return of samples to the vicinity of the ISS for study, or to the vicinity of humans in Mars orbit.

Before a sample return, the public will need to be involved in a full and open debate about the mission for both legal[26] and ethical[27] reasons. This debate will need to take account of all the views on the matter. It will also need to take account of alternative proposals.

Back contamination risks of a Mars sample return[edit | hide | edit source]

These concerns were originally raised by Carl Sagan in 1973 in his book the Cosmic Connection,[18] and Carl Woese.[19] More recently the concerns have been raised particularly by the International Committee Against Mars Sample Return, an advocacy group of scientists campaigning against an early MSR.[20].

These concerns inform both the official approach, and the scientists who are critical of it, and are of historical interest to all the parties in the debate.

Carl Woese, who first classified the Archaea, the third domain of life[28] said in an interview:

When the entire biosphere hangs in the balance, it is adventuristic to the extreme to bring Martian life here. Sure, there is a chance it would do no harm; but that is not the point. Unless you can rule out the chance that it might do harm, you should not embark on such a course.[19]

Carl Sagan wrote in his book Cosmic Connection:

...The likelihood that such pathogens exist is probably small, but we cannot take even a small risk with a billion lives.[18]

Existential risk potential for returned martian life[edit | hide | edit source]

The potential of Martian life to create a biohazard on Earth was first raised by Carl Sagan in 1973 in his book "Cosmic Connection".[18] The concern has been reviewed many times since then by experts in the field, with the same or similar conclusions. These are also the conclusions of the official NSF and ESF reports. According to these experts, it is an existential risk[29], though thought to be one of very low probability.

Sagan wrote:

Precisely because Mars is an environment of great potential biological interest, it is possible that on Mars there are pathogens, organisms which, if transported to the terrestrial environment, might do enormous biological damage - a Martian plague, the twist in the plot of H. G. Wells' War of the Worlds, but in reverse. This is an extremely grave point. On the one hand, we can argue that Martian organisms cannot cause any serious problems to terrestrial organisms, because there has been no biological contact for 4.5 billion years between Martian and terrestrial organisms. On the other hand, we can argue equally well that terrestrial organisms have evolved no defenses against potential Martian pathogens, precisely because there has been no such contact for 4.5 billion years. The chance of such an infection may be very small, but the hazards, if it occurs, are certainly very high...[18]

The microbiologist Joshua Lederberg made a similar point about the impossibility of deciding the issue of biohazard potential.

Whether a microorganism from Mars exists and could attack us is more conjectural. If so, it might be a zoonosis to beat all others.

On the one hand, how could microbes from Mars be pathogenic for hosts on Earth when so many subtle adaptations are needed for any new organisms to come into a host and cause disease? On the other hand, microorganisms make little besides proteins and carbohydrates, and the human or other mammalian immune systems typically respond to peptides or carbohydrates produced by invading pathogens. Thus, although the hypothetical parasite from Mars is not adapted to live in a host from Earth, our immune systems are not equipped to cope with totally alien parasites: a conceptual impasse.[21]

Carl Sagan's recommendation for a vigorous program of Martian exobiology[edit | hide | edit source]

Carl Sagan recommended that a "vigorous program of unmanned Martian exobiology and terrestrial epidemiology"[18] should be undertaken first, before any Mars sample return.

Because of the danger of backcontamination of Earth, I firmly believe that manned landings on Mars should be postponed until the beginning of the next century, after a vigorous program of unmanned Martian exobiology and terrestrial epidemiology.

He wrote this in the 1970s. However no such program was undertaken between Viking and Curiosity.

Curiosity is the first rover since Viking to directly search for biosignatures. This is just a beginning. Its "hand lens", though high resolution of 14.5 micrometers per pixel, can't observe endospores or other dormant states directly. A laboratory difraction limited optical microscope for study of cell life typically has a resolution of 0.2 micrometers per pixel. It can't dig far beneath the surface, and it's level of sterilization is not high enough under COSPAR guidelines to study habitats where life might occur in present day Mars.

There are other rovers planned for the future that will build on its results to continue a program of exobiology including more sensitive detection of biosignatures and signs of reproducing life on Mars.

Carl Sagan wrote in Cosmos[30]:

“ If we wish on Earth to examine samples of Martian soil for microbes, we must, of course, not sterilize the samples beforehand. The point of the expedition is to bring them back alive. But what then? Might Martian microorganisms returned to Earth pose a public health hazard? The Martians of H. G. Wells and Orson Welles, preoccupied with the suppression of Bournemouth and Jersey City, never noticed until too late that their immunological defenses were unavailing against the microbes of Earth. Is the converse possible? This is a serious and difficult issue. There may be no micromartians. If they exist, perhaps we can eat a kilogram of them with no ill effects. But we are not sure, and the stakes are high. If we wish to return unsterilized Martian samples to Earth, we must have a containment procedure that is stupefyingly reliable. There are nations that develop and stockpile bacteriological weapons. They seem to have an occasional accident, but they have not yet, so far as I know, produced global pandemics. Perhaps Martian samples can be safely returned to Earth. But I would want to be very sure before considering a returned-sample mission.”

National Research Council review of biohazard potential of returned samples=[edit | hide | edit source]

The National Research Council review was undertaken in 2009 (and previously in 1997) and published as their "Assessment of Planetary Protection Requirements for Mars Sample Return Missions".[31] They carried out a review of the entire process of Mars Sample Return. The conclusion was that the potential hazard, though likely to be low, is not demonstrably zero, and that as a result any mars sample return should be treated as a potential biohazard until proved otherwise.[1]

They reviewed the then current research on relevant subjects, to come to their conclusion.

  • Potential for habitable conditions on Mars. They concluded that research since the last report has enhanced the prospect that habitable environments were once widespread on Mars, and has improved understanding of the potential for modern habitable environments, and "enhanced the possibility that living samples could be present in samples returned from Mars".[13][32]
  • Capability of micro-organisms to survive on Mars. To assess this, they reviewed recent research in microbial ecology in Chapter 3. They noted the discovery of new extremophiles in an increasing range of habitats, including highly acidic locations, conditions of extreme cold, of ephemeral habitability, and the capability of some micro-organisms to survive in dormant states for at least 250 million years. They also noted the discovery of novel single-species ecosystems such as the one inhabited solely by the chemoautotrophic Candidatus Desulforudis audaxviator. They noted the discovery of new organisms and ecological interactions, including viruses capable of limited independent viral growth outside a host cell, under acidic hyperthermophilic conditio.[33] Their conclusion was that these researches highlighted the potential of micro-organisms adapted to live in the Martian environment.[34]
  • Biohazard potential of any martian micro-organisms. They noted that extremophiles have not yet been shown to pose significant biological risk to humans. However in chapter 5, they note that there are comparative studies of extremophiles and of human pathogens "suggesting that evolutionary distances between nonpathogenic and pathogenic organisms can be quite small in some instances." As a result they concluded that the potential risks of biological epidemics can't be reduced to zero.[35]
  • Would the sample include micro-organisms not already delivered to Earth on martian meteorites? To assess this, they estimated that around 5 meteorites a year probably impact Earth from Mars. So the transfer of sufficiently hardy life forms from Mars to Earth via meteorite seems plausible.[36] However, they concluded that the passage in a sample container could preserve lifeforms that would not survive the passage on a meteorite.[37]
  • Could martian lifeforms transferred to Earth in a meteorite have caused mass extinctions on Earth in the past? Their conclusion was that there is no evidence of this in the recent past but it could not be ruled out as a possibility in the more distant past.[37][38]

Their overall conclusion was that "the potential for large-scale negative effects on Earth's inhabitants or environment by a returned martian life form appears to be low, but is not demonstrably zero". As with previous reports, they recommended that the sample be treated as a biohazard until proved otherwise.[1]

Specific concerns detailed in the ESF Mars Sample Return backward contamination study and their risk mitigation[edit | hide | edit source]

The proposal is to build a special new type of combined clean room, and biohazard containment facility to receive the samples. The sample return mission is designed to break the chain of contact with Mars for the exterior of the sample container[5].

The concerns considered by the ESA will be raised, as presented in the study, followed by their suggested methods to mitigate them.

Concerns with integrity of the sample container[edit | hide | edit source]

The container could rupture if the parachute fails during the landing (rupture of a sample container has already occurred during the sample return of the Genesis capsule).

There is a low risk of an undetected failure to create a seal when the Mars sample is first enclosed in the container. Another risk is that "the sample magazine could be penetrated by a micrometeoroid during transit from Mars, thereby causing exterior contamination and release upon entry".[5]

Risk mitigation: Reinforced sample container[edit | hide | edit source]

The risk of rupture of the container is reduced by requiring that the capsule be capable of withstanding the shock of impact at terminal velocity.

The risks of undetected failure to create a seal when the Mars sample is first enclosed in the container, and of penetration by a micrometeoroid are reduced by use of methods to detect such leaks if they occur.[39]

Concerns with the proposed biohazard facilities[edit | hide | edit source]

First, the facility must also double as a clean room, to keep Earth micro-organisms away from the sample. This greatly adds to the complexity of the facility, and so to the risk of failure, since clean rooms and biohazard rooms have conflicting requirements (biohazard containment facilities are normally built with negative air pressure for instance, to keep organisms in, and clean rooms with positive air pressure to keep organisms out). It will be the first such facility ever to be built. [5][6]

Also, biohazard facilities are designed to contain known hazards. It's a much harder problem to contain unknown hazards. A Mars sample could contain uncultivatable archaea, or ultramicrobacteria that can pass through a 0.1 µm filter. It might even contain Martian nanobacteria if such exist. A recent concern is that it could contain virus-types and genetransfer agents as small as 0.03 µm in size, especially if Mars life and Earth life share a common ancestor at some point. It might also contain forms of life that don't exist on Earth, possibly even based on novel life chemistry, which makes it hard to set an absolute lower size. [40]

Risk mitigation: Analyze samples in Biosafety level 4 laboratories to a new design, with staff trained well in advance[edit | hide | edit source]

NASA has proposed to build a Biosafety level 4 biohazard containment facility to a new design to protect the samples from Earth contamination and simultaneously protect against biohazard release. The sample return mission itself is designed to break the chain of contact with Mars for the exterior of the sample container[5][6]

All the studies also recommend recommended that the facilities are built and staff trained well in advance of the actual mission. The current recommendation is that the facilities are completed and the staff trained at least two years before the sample is returned, and that the planning for the facility start at least a decade before sample return [41]

Concerns about human error, crime, and natural accidents[edit | hide | edit source]

Human error, or management decisions could compromise the safety precautions taken for safe sample return.

This happened several times during the Apollo era attempts at containing the lunar samples. In particular when the astronauts returned to Earth from Apollo 11, the hatch of the module was opened by divers, while it was still in the sea, permitting lunar dust to exit the module and enter the sea in breach of the previously established planetary protection protocol[42] In the NASA proposals, the potential for human error is reduced by ensuring that the receiving facility is operational and the staff trained several years before the Mars samples are brought into Earth's environment.[43][full citation needed]

Other risks include the possibility of accidents, natural disasters, or crime, leading to release of the materials, once the samples are on the Earth surface.[44][full citation needed]

Risk mitigation: Institute proper safety training and management precautions[edit | hide | edit source]

The risk of human error, or management decisions that compromise the safety precautions is reduced by training, redundancy, and making sure critical decisions are not made by tired astronauts.[5]

Concerns about latency or incubation period[edit | hide | edit source]

Carl Sagan first raised this concern:

There is also the vexing question of the latency period. If we expose terrestrial organisms to Martian pathogens, how long must we wait before we can be convinced that the pathogen-host relationship is understood? For example, the latency period for leprosy is more than a decade.[18]

The WHO Leprosy fact sheet[45] gives the incubation period of leprosy, from first infection to onset of symptoms, as up to 20 years.

In the European Space Foundation report, incubation period is listed as the first of the list of unknowns that make it impossible to use standard models for the effects of a release and its consequences [46]

  • "Incubation period
  • Transmissibility from person to person/number of secondary cases per infected individual
  • Time window of transmission
  • Case fatality rate
  • Hospitalisation of patients – hospitals can increase transmission and amplify outbreaks
  • Transmission routes (aerosol, ingestion, etc.)
  • Survival/reproduction in the environment
  • Can it infect animals/plants
  • Duration of the symptomatic phase"

Since all these factors are unknown, they concluded that "it is impossible to model the consequence of the potential release of a Mars organism".

"From a crisis management position, if the effects of the release are unusual and of rapid onset, it is most likely that the causative agent will be identified fairly quickly and actions can be taken to try to limit the spread. However, if the onset is slow and the effects are not unusual, significant spread may occur before the nature of the threat is realised.

If the Mars life form has an unknown, fundamentally different biochemistry to life forms on Earth but nonetheless is able to cause adverse consequences in the Earth’s biosphere, this must be considered to be an extreme worst case scenario. If this were to be the case, a major rethink of the applicability of current strategies for dealing with pathogens would be required. Some of the questions that could arise include:

  • Can it be assumed that the consequences are limited to one or a few species?
  • Are currently available biocides effective?
  • How can the presence of the life form(s) be detected?
  • Susceptibility of population"

Risk mitigation - detailed observations and rapid response[edit | hide | edit source]

To mitigate this risk they "recommend that potential release scenarios (including undetected release) are clearly defined and investigated, and that response strategies are developed from these.

"It is crucial that such strategies are designed to be implemented as soon as possible and at the local level and that they encompass:

  • observation of pre-defined indicators
  • rapid detection of anomalies
  • effective warning procedures
  • analysis, resistance and mitigation procedures"

Recommendations for acceptable level of risk in the advance planning documents[edit | hide | edit source]

In current advance planning for the Mars Sample Return facility on Earth it is recognised that the risks can't be reduced to zero.[5]

Consequently, risk-mitigation strategies will focus on eliminating the hazard and/or reducing the probability of a negative event. Both will lead to a risk that is considered acceptable, since achieving zero risk is not possible.[47]

One suggestion for an acceptable level of risk was recommended by the ESF-ESSC Study Group "Based on standards established and adopted at the national and international levels, the ESF-ESSC Study Group recommends that the probability of release of a potentially hazardous Mars particle shall be less than one in a million.".[5]

About Lederberg's concern of a "zoonosis to beat all others" they say: [5]

With those thoughts in mind, it may seem that the risk posed by returning a dangerous biological entity (e.g. a virus-type, microorganism, etc.) is quite low. Nevertheless, it still cannot be guaranteed to be impossible. It is believed that if such a biological entity exists, humans would be able to kill it (by the sundering of covalent bonds in a rigorous sterilisation process).

... , the overall risk posed by returning a dangerous biological entity from Mars is quite low, not even considering the reduction factor of one in a million recommended in Chapter 4.5.

Assessment of an acceptable level of risk[edit | hide | edit source]

There is much that is agreed on amongst all the parties concerned.

  • All agree on the scientific value of a MSR (provided scientifically interesting specimens can be returned to Earth)
  • All agree that the samples should be treated as biohazards until proved otherwise
  • All agree that the level of risk is probably very low
  • All those who discuss them agree that the recommendations and current NASA plans reduce the risk even further by a considerable amount.

The question at dispute is whether the combined risk is now so low it can be ignored?

To assess this, methods of legal and political decision making are required, and methods for assessing what are acceptable levels of risks on an ethical basis. The studies focus on the Precautionary Principle[48] as a way to inform the decision making process.

Precautionary principle[edit | hide | edit source]

By the Precautionary principle, a key principle in political decision making, and law:

When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.

In this context the proponent of an activity, rather than the public, should bear the burden of proof.

The process of applying the Precautionary Principle must be open, informed and democratic and must include potentially affected parties. It must also involve an examination of the full range of alternatives, including no action.[48]

Precautionary principle in the context of Mars Sample Return as assessed by the ESF-ESSC Study Group[edit | hide | edit source]

The ESF-ESSC Study Group on MSR Planetary Protection Requirements studied various versions of the Precautionary Principle in the context of Mars Sample Return.[46] This study found that the ones that were most relevant are:

  • Best Available Technology Precautionary Principle: Activities that present an uncertain potential for significant harm should be subject to best technology available requirements to minimise the risk of harm unless the proponent of the activity shows that they present no appreciable risk of harm.
  • Prohibitory Precautionary Principle: Activities that present an uncertain potential for significant harm should be prohibited unless the proponent of the activity shows that it presents no appreciable risk of harm...

They continue:

...It is not possible to demonstrate that the return of a Mars sample presents no appreciable risk of harm. Therefore, if applied, the Prohibitory Precautionary Principle approach would simply lead to the cancellation of the MSR mission

They therefore argue that the Best Available Technology Precautionary Principle should be used instead.

The definition of Precautionary Principle and the associated conditions presented above align perfectly with the potential risks posed by a Mars sample and the ESF-ESSC Study Group recommends that the Best Available Technology Precautionary Principle is applied when considering the potential release of unsterilised Mars particles.

In this context a required level of risk needs to be determined to assess the technology used. They recommend a one in a million chance of release of a particle from Mars as an acceptable level of risk. Their reasoning is that the chance that the particle is hazardous is already low, and then by making the chance of release as low as one in a million, the combined risk is low enough to be acceptable.

Legal process of approval for Mars sample return[edit | hide | edit source]

Race published a study of the legal processes required for approval.[26] His conclusions were:

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. This process is likely to take up to several years to complete.

The full range of worst accident scenarios, impact, and project alternatives would be played out in the public arena. Other agencies such as the Environment Protection Agency, Occupational Health and Safety Administration, etc, may also get involved in the decision making process. The laws on quarantine will also need to be clarified as applied to this situation.

Then apart from those domestic legal hurdles, there are numerous international regulations and treaties to be negotiated in the case of a Mars Sample Return, especially those relating to environmental protection and health. So the public of necessity has a significant role to play in the development of the policies governing Mars Sample Return.

Legal liability in case of damages[edit | hide | edit source]

In the event of a release of the contents of the MSR capsule during return to Earth then the state responsible has unlimited liability in respect to any damages caused.

Under the Liability Convention (United Nations, 1971), the launching State is liable for “damages caused by the space object”. If a sample has detrimental consequences on Earth, it may be considered that the State having launched the spacecraft is liable under this convention (absolute liability without any ceiling either in amount or in time; Liability Convention Article 1 – loss of life, personal injury or impairment; or loss of or damage to property of States or of persons, natural or juridical, or property of international intergovernmental organisations)..[3]

If the damages occur as a result of release after the capsule has returned to an Earth laboratory, the situation is less clear. The unlimited damage clause may still apply, or they might instead be responsible for an illegal act under general international law in violation of Article IX of the Outer Space Treaty, which doesn't have the same provisions of unlimited liability.

Requirement for public debate[edit | hide | edit source]

In addition to the legal requirement, it's been argued that there is a moral requirement for full and open public debate of the issues. The theologan Richard Randolph (in 2009) examined this in detail from a Christian perspective and came up with some recommendations, which are of general interest.[27]

...The risk of back contamination is not zero. There is always some risk. In this case, the problem of risk - even extremely low risk - is exacerbated because the consequences of back contamination could be quite severe. Without being overly dramatic, the consequences might well include the extinction of species and the destruction of whole ecosystems. Humans could also be threatened with death or a significant decrease in life prospects

In this situation, what is an ethically acceptable level of risk, even if it is quite low? This is not a technical question for scientists and engineers. Rather it is a moral question concerning accepting risk. Currently, the vast majority of the people exposed to this risk do not have a voice or vote in the decision to accept it. Most of the literature on back contamination is framed as a discourse amongst experts in planetary protection. Yet, as I've already argued, space exploration is inescapably a social endeavor done on behalf of the human race. Astronauts and all the supporting engineers and scientists work as representatives of all human persons....

He then puts forward four criteria to ensure a full and open public debate. To summarize (he goes into more detail) the criteria are:

  1. The best practises of planetary protection must be followed.
  2. There should be opportunities for open comment from those concerned about back contamination. These comments should be taken seriously and NASA should publicly respond to those concerns.
  3. A committee should review the measures, and this committee should include experts in ecology, biology, chemistry, risk analysis and ethics. The ethicists should represent a diversity of philosophical and religious perspectives.
  4. The entire process should be transparent to the interested public.

Researchers who advocate no action[edit | hide | edit source]

This section is included for completeness as required for the precautionary principle. However, there don't currently seem to be any notable advocates of this approach.

Researchers who advocate that a sample return to Earth should not e attempted until thoroughly studied first[edit | hide | edit source]

A small minority of researchers are of the view that a sample return to Earth should not be attempted until the martian life and biohazard potential of the sample is thoroughly understood.

Historically, Carl Sagan[18] and Carl Woese[19] took this position.

In the present day, then Barry DiGregorio[42] and Gilbert Levin[49] are the main advocates. It is the stated view of the ICAMSR advocacy group lead by Barry DiGregorio, which includes some other members, who haven't published papers or been quoted in news stories on the subject.[50]

Researchers who cite greater planetary protection issues as a motivation for in situ studes on Mars first[edit | hide | edit source]

This section is for researchers who, though not critical of the prevailing MSR plans, present planterary protection advantages as points in favour of alternate approaches.

Craig Venter presents this as an advantage of his DNA sequencer on Mars approach. The telerobotics experts who advocate in situ studies by telepresence and telerobotics first, also do so partly because of the advantages of this approach for planetary protection.[24]

The science potential of an early Mars sample return[edit | hide | edit source]

To inform the debate on the MSR it is necessary to review the science potential, the motivation for the mission.

To quote from the ESF report [51]

"Through the study of a sample, researchers could make great progress in understanding the history of Mars, its volatiles and climate, its geological and geophysical history, and gain new insights into astrobiology. A Mars sample return has also been deemed an essential precursor to any human exploration missions to Mars

Although some questions may be answered through in situ studies carried out by robotics on the Mars surface, returning a sample to Earth is desirable for several reasons:

  • Many experiments and their sample preparations will be too complex for an in situ robotic mission
  • Returning a sample allows for flexibility in dealing with the unknown and unexpected discoveries via new protocols, experiments and measurements
  • There are major limitations with regard to size and weight of instrumentation that can be flown
  • There is a significant communication delay to Mars, which impedes the ability to deal with emergencies
  • There is a much greater diversity in available instruments and an almost unlimited range of analytical techniques that can be applied on Earth
  • The ability to repeat experiments in multiple laboratories and confirm key results is available on Earth
  • Participation of entire analytical community is possible
  • There is the potential to propagate organisms if they are discovered

In addition to the above points, returning a Mars sample will bring enormous public excitement and engagement to space-related activities, along with pride and prestige to this accomplishment of mankind."

See also Mars_sample_return#Scientific_value scientific value for the Mars sample return mission.

Issues with the science potential of an early MSR[edit | hide | edit source]

This is for issues with the pure science potential, ignoring back contamination issues.

Issues to do with selection of samples of biological interest on mainly geological basis[edit | hide | edit source]

Jeffrey Bada argues that we do not yet know enough to intelligently select samples for return. He is an advocate of a "Follow the Nitrogen strategy for in situ exploration".

He recommends that a MSR should be delayed until unambiguous biomarkers are identified in prospective Mars samples.[22]

In this White Paper we argue that it is not yet time to start down the MSR path. We have by no means

exhausted our quiver of tools, and we do not yet know enough to intelligently select samples for return. In the best possible scenario, advanced instrumentation will identify biomarkers and define for us the nature of the sample to be returned. In the worst scenario, we will mortgage the exploration program to return an arbitrary sample that proves to be as ambiguous with respect to the search for life as ALH84001.

...We argue here that when in situ methods have definitively identified biomarkers, or when all reasonable in situ technologies have been exhausted, it will be time for MSR. We are not yet at that crossroad.

...Over the last decade the development of the Urey instrument for organic and oxidant detection on Mars has succeeded in addressing many of the aspects of primary concern for effective detection of biosignatures on Mars

For return of biologically interesting samples, he requires ability to identify, in situ:

  • Biomarkers and unequivocal biosignatures capable of distinguishing between biogenic and abiotic products, and stable over geological timescales. He mentions particularly the ability to detect chirality, and primary amine distribution as examples.
  • Samples suitable for preserving life, such as sulfates, haliites, clays and the polar layerd deposits, and with potential for preservation of organics without significant degradation over geological time periods.
  • Nitrogenous organic compounds
  • Trace amounts of organics

He also recommends:

  • Any extraction methods used must preserve the target organic molecules with low degradation
  • Drilling to the greatest depth possible to allow for greatest chance of success for detecting organics and biosignatures.

Some of these concerns (but not all) have been addressed by the Final report of the MSR End-to End International Science Analysis Group in 2011. They stress the importance of observations to understand the geological context, They also plan to include the ESA Pasteur payload (developed for ExoMars) which includes some life detection instruments. It will for instance able for instance to detect many specific molecules likely to be associated with past or present life, with its Life Marker Chip.[52][53][54].

The focus of this report was on missions they considered practical, so, unlike Jeffrey Bada's suggestion, they don't require deep drilling, and don't require the MSR to be delayed until unambiguous biosignatures are found.

"Finally, for the purposes of this study, the vision of the MSR Campaign was constrained by what was considered to be practical ... Thus, objectives that might require high latitudes, high elevations, deep (>2 m) drilling, and large sample masses, for example, were given lower priority. The intent was not to provide a prioritized list in the abstract, but one that could be used to guide a sample return campaign in the context of our current knowledge and expectations of future engineering and fiscal resources." [53]

Issue of contamination of a returned sample by terrestrial DNA[edit | hide | edit source]

Craig Venter (famous for sequencing the human genome) is in process of developing a miniaturized gene sequencer small enough to fit on a rover to Mars. His motivation is that current gene sequencers are now so sensitive, that if a single micro-organism from Earth landed on the sample returned from Mars, it would ruin the experiment to test for presence of martian DNA on the sample.

Craig Venter's view is that this is best done in situ on Mars.[23]

This is another concern mentioned in the 2011 review of the Space Studies Board,[55] however, they believe it can be surmounted by suitable decontamination procedures.

It is possible that traces of life on Mars may be very rare and heterogeneously distributed, and the concentration of organics in the soil may be very low. Thus, it is essential to avoid biological contamination as well as organic contamination of Mars and of the collected samples.

Advocacy of an early Mars sample return[edit | hide | edit source]

In a 2011 survey of the community of active planetary scientists working on Mars[56] :

The Mars community, in their inputs to the decadal survey, was emphatic in their view that a sample return mission is the logical next step in Mars exploration. Mars science has reached a level of sophistication that fundamental advances in addressing the important questions above will only come from analysis of returned samples.

In the summary of the final report of the Mars Program Planning Group in September 2012, two main pathways were presented with the group favouring the pathway leading to sample return as soon as possible.[57]

Pathways A1 and A2:

Commence Sample Return using exising data

  • Search for signs of past life with samples collected from a site identified using exising data and returned to Earth for analysis
  • This is most directly responsive to the NRC Decadal Survey recommendations
  • Collect scientifically selected samples from a site which has been determined to have astrobiological significance
  • Timing of returned samples paced solely by available funds, not further science discoveries

In pathways A1 and A2, then sample return is carried out immediately with no more science data.

Pathway A3

Multiple site Investigation to Optimize Search for Past Life

  • Search for signs of past life through in situ observations and ultimately analysis of carefully selected samples returned to Earth
  • Sample Return commences only after in situ measurements and sampling of multiple sites and Science Community decision process as to which to return to Earth
  • The emphasis of this pathway is searching for samples capable of preserving evidence of past life

Alternatives to an early return of Mars samples to the Earth's surface[edit | hide | edit source]

The precautionary principle requires full debate of all the possible alternative actions including no action[48]. In the case of MSR there are many suggested alternatives to an early mission.

There are proposals to study the sample extensively on the surface of Mars. There are also proposals to return the sample to quarantine facilities in Mars orbit or to Earth orbit. Also return to quarantine facilities can be done straight away, or only after a thorough in situ study on the surface of Mars.

With all these approaches, Mars sample return would be expected eventually once it is possible to show with confidence that the chance of biohazard from the Mars sample is low enough to no longer be a matter of concern.

Vigorous study of the Mars surface before a sample return[edit | hide | edit source]

There are instruments under development for future Mars missions that will enable preliminary study of samples with greater sensitivity than any instruments currently in use on the rovers.

  • NASA Marshall Space Flight Center is leading a research effort to develop a Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) for future lunar and martian missions.[58]
  • Jonathan Rothberg, and J. Craig Venter, are separately developing solutions for sequencing alien DNA directly on the Martian surface itself.[59][60] Venter additionally sees his proposal as a way to return Martian DNA to Earth while bypassign most of the back contamination issues, “We can rebuild the Martians in a P-4 spacesuit lab instead of having them land in the ocean.” [23]
  • Levin is working on updated versions of the Labeled release instrument flown on Viking. For instance versions that rely on detecting chirality. This is of special interest because it can enable detection of life even if it is not based on standard life chemistry.[61]
  • The Urey Mars Organic and Oxidant Detector instrument for detection of biosignatures due to be flown on Exomars in 2013. It is designed with much higher levels of sensitivity for biosignatures than any previous instruments[22][62][63]

These proposed new instruments under development have the advantage over Mars sample return that you can analyse rocks in situ on Mars, and then choose new targets on the surface of Mars based on your findings. This approach could also involve study of the samples on the Mars surface via telepresence from Mars orbit, permitting rapid exploration and use of human cognition to take advantage of chance discoveries and feedback from the results obtained so far.[25]

These proposed instruments would permit studies with a reasonable chance of detecting current life on Mars either through direct observation, or through activity that suggests life processes. If life signs are discovered, MSR would then be undertaken with extreme caution, after biohazard testing in situ on Mars first to the fullest extent possible.

Issues with in situ study as a way to reduce contamination risks[edit | hide | edit source]

The Office of Planetary Protection have said that an in situ study, though useful, is not likely to significantly reduce uncertainty to the extent that planetary protection measures could be relaxed.

Uncertainties with regard to the possibility of extant martian life can be reduced through a program of research and exploration that might include data acquisition from orbital platforms, robotic exploration of the surface of Mars, the study of martian meteorites, the study of Mars-like or other extreme environments on Earth... Such an exploration program, while likely to greatly enhance our understanding of Mars and its potential for harboring life, nonetheless is not likely to significantly reduce uncertainty as to whether any particular returned sample might include a viable exogenous biological entity-at least not to the extent that planetary protection measures could be relaxed.

Vigorous study of the Mars surface instead of a sample return[edit | hide | edit source]

This view was given in an interview of astrobiologist Dirk Schulze-Makuch for [64]

"I disagree with the high priority on sample return," said astrobiologist Dirk Schulze-Makuch of Washington State University in Pullman.

"Our in-situ [on-the-spot] capabilities are so much better nowadays than, let's say during Viking lander (1970s) times," Schulze-Makuch said. "We could address with an in-situ mission whether microbial life is present on Mars."

Sample return missions are so much more costly, Schulze-Makuch said, "and the only thing that would be advantageous, in my view, is to get an absolute age scale via radioactive dating of Martian rocks," Schulze-Makuch said, "but from an astrobiological viewpoint, [an] in-situ mission would be better and cheaper."

Another advocate of vigorous study on the surface in place of a MSR is Robert Zubrin, president of the Mars Society. He is of the opinion that the same objectives are better met using a vigorous program of robotic exploration using many rovers on the same model as Curiosity. In a panel session at the International Mars Society Convention in Pasadena on August 3 2012 he is reported as saying:[65]

I believe the program has become overfocused on sample return,” Zubrin said. While he supported robotic exploration for Mars as a step towards human missions, he worried that trying to land on Mars, collect samples, place them into a rocket that launches them into Mars orbit for later retrieval and return to Earth may be too complex. “I think that extrapolating the robotic program to sample return is taking it beyond when it beneficially trades off against human exploration,” he said.

“I do not see how sample return, as such, is vital for human exploration, and I think that saying that it is actually creates an obstacle to human exploration,” Zubrin said. Zubrin instead supports an “aggressive” program of rover missions, based on the highly-successful MERs. “Here we have a very successful system, why don’t we churn these things out, start sending two of them every two years to Mars, different locations with different instruments, conducing different kinds of investigations, make them into a workhorse,” he said. Doing so, he said, could reduce the cost of each mission to $200–400 million, far less than the estimated $2.5 billion cost of Curiosity.

Then, writing an article himself in Space News in Dec. 3, 2012, he wrote[66]:

It is certainly possible to propose alternative robotic mission sets consisting of assortments of orbiters, rovers, aircraft, surface networks, etc., that might produce a greater science return than the Mars sample return mission, much sooner, especially in view of the fact that human explorers could return hundreds of times the amount of samples, selected far more wisely, from thousands of times the candidate rocks, than a sample return mission.

Study via telepresence from Mars orbit, followed by return of the sample to Mars orbit[edit | hide | edit source]

The use of telerobotics and telepresence on Mars was one of the subjects of the Exploration Telerobotics Symposium|[67] of researchers in telerobotics in industry and academia hosted at the NASA Goddard Space Flight Center in 2012. Their findings list many benefits of telepresence exploration of Mars.[68]

They strongly recommended use of telerobotics in any proposed future mission to Mars orbit. They also recommended that sample return be made to Mars orbit rather than to Earth: [24]

* "If a human mission to Mars orbit were decided for national reasons, it would be an unfortunate mistake not to include low-latency control of robots on the surface.

  • Most of the telerobotic technology exists for this mission, although its TRL needs to be advanced and validated for flight.


  • The ability for the on-orbit crew to control multiple robotic assets on the surface is imperative, or to take over control of one of them from Earth operators when interesting or time-critical situations arise."[24]

The report goes into the advantages of telerobotics for exploration of Mars in detail. Some of the main points raised are::[24]

* Astronauts have near real-time control of the robots at the exploration sites, including controlling robots in several different locations simultaneously, and can respond immediately to discoveries.

  • Prevents contamination both ways
  • Humans may be severely constrained in current EVA suits, and telerobitic explorers can be designed with human level mobility "like a field scientist" as well as superhuman abilities.
  • Return of the sample to orbit permits analysis without delay, to detect volatiles that may be lost during a voyage home.

On the mobility benefits of telerobotics they write:[24]

"High-capability telerobotic surrogates can be more challenging. Although robotic sensor systems are vastly more capable than corresponding human senses and do not limit our cognition, mobility and dexterity are more difficult. However, terrestrial telerobotics (surgery, undersea oil & gas, mining) have a high degree of mobility and dexterity. Technology investment will surely increase capability"

On the value for sample return to orbit:[24]

"In the case of samples of biological significance, very rapid encapsulation and recovery of the sample materials at the spacecraft in orbit are required and this is enabled by this approach."[25]

Several types of suitable orbits for such a mission were discussed:[24]

"For Mars, aerostationary orbits offer advantages for long-duration operation at multiple sites. Molnya-type orbits offer extended-duration connections. Operations from Phobos and Deimos orbits have been proposed as sites that offer extra radiation shielding, although suffer from very limited surface contact times and can be in difficult-to-reach orbits."

There have many previous proposals for human missions to Mars orbit to study the planet via telepresence and telerobotics, such as Zubrin's double Athena flyby, the Herro mission, and others, see Exploration of the surface from orbit, via telerobotics and telepresence

Return to the ISS or Earth orbital laboratory first[edit | hide | edit source]

Gilbert Levin recommends a 10 step sequence for returning Martian samples to Earth[49] This involves a series of tests for the micro-organisms in situ on Mars, including tests for biohazard potential to whatever extent is possible on Mars, before returning them to the ISS. Once in the ISS they need to be examined in secure biohazard facilities by volunteer scientists who are willing to give up their lives in the remote chance that a hazard is found that is of danger to life on Earth. Finally, if they pass all the tests, they can be returned to secure biohazard labs on Earth for further testing. Once on Earth then laboratories should be provided for researchers all in the same location, rather than send the samples to researchers in other locations for testing.

Issues with the use of quarantine periods in space to contain any biohazard[edit | hide | edit source]

Many of these proposals recommend a quarantine period in a human occupied spacecraft in space first before the sample is returned to Earth. A 1997 study by the National Research Council found some issues which would need to be addressed if this is an essential feature of the back contamination containment protocol.

First, the study raised the issue that it would be hard to know for sure if any detected anomaly was the result of contamination. How, they say, could sufficient certainty be achieved to justify destroying the returning spacecraft and its crew?[69]

Carl Sagan wrote about the same issue in his book The Cosmic Connection: An Extraterrestrial Perspective[70]

The one clear lesson that emerged from our experience in attempting to isolate Apollo-returned lunar samples is that mission controllers are unwilling to risk the certain discomfort of an astronaut – never mind his death – against the remote possibility of a global pandemic.

In the case of the Lunar quarantine, then the guiding principles used by NASA at the time of Apollo did permit breach of quarantine in the case of danger to human life:[71]

2. The preservation of human life should take precedence over the maintenance of quarantine.

So the issue here is whether it is politically or humanly feasible to have a policy that puts preservation of quarantine at a higher priority than preservation of the life of individual astronauts. If not then the human quarantine approach does not give a total guarantee of containment of any issues found.

Another issue raised in the 1997 study is that infection might not be the only biohazard to contain, since a returning organism could cause long term changes in our environment that does not turn up during a quarantine period with humans.[69]

Historical background[edit | hide | edit source]

The idea of a Mars Sample Receiving laboratory was first studied in 1978. The idea then was for an orbiting quarantine facility called Anteus to receive the samples.[72]

References[edit | hide | edit source]

  1. "Assessment of Planetary Protection Requirements for Mars Sample Return Missions", National Research Council, 2009, chapter 5, "The Potential for Large-Scale Effects". "Thus, a key question posed to the committe is whether a putative martian organism or organisms, inadvertently released from containment, could produce large-scale negative pathogenic effects in humans or have a destructive impact on Earth's ecological system or environments." (page 45) They divide it into 3 categories
    • Large-scale negative pathogenic effects in humans;
    • Destructive impacts on Earth's ecological systems or environments; and
    • Toxic and other effects attributable to microbes, their cellular structures, or extracellular products.

    (page 45)

    They conclude that the last one is unlikely. But for the other two

    The committee found that the potential for large-scale negative effects on Earth's inhabitants or environment by a returned martian life form appears to be low, but is not demonstrably zero.

    (page 48)
  2. "5: "The Potential for Large-Scale Effects"". Mars Sample Return backward contamination - strategic advice (PDF) (Report). European Science Foundation. 2012. RECOMMENDATION 10: Considering the global nature of the issue, consequences resulting from an unintended release could be borne by a larger set of countries than those involved in the programme. It is recommended that mechanisms dedicated to ethical and social issues of the risks and benefits raised by an MSR are set up at the international level and are open to representatives of all countries.  line feed character in |quote= at position 22 (help)
  3. 3.03.1 Mars Sample Return backward contamination – Strategic advice and requirements see 7.2: Responsibility and liability of States
  4. "2: "The Potential for Past or Present Habitable Environments on Mars"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. 
  5. European Science Foundation - Mars Sample Return backward contamination - strategic advice July, 2012, ISBN 978-2-918428-67-1 - see Back Planetary Protection section. (for more details of the document see abstract )
  6. Jeremy Hsu Keeping Mars Contained Astrobiology Magazine, 12/03/09
  7. Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. 
  8. Jeremy Hsu Moon to Mars, 12/03/09
  9. NASA Office of Planetary Protection
  10. Mars Sample Return: Issues and Recommendations Task Group on Issues in Sample Return. National Academies Press, Washington, DC (1997)
  11. 11.011.1 Mars Sample Return: Issues and Recommendations Summary for: Task Group on Issues in Sample Return. National Academies Press, Washington, DC (1997
  12. "7: "Sample-Receiving Facility and Program Oversight"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 59. It has been estimated that the planning, design, site selection, environmental reviews, approvals, construction, commissioning, and pre-testing of a proposed SRF will occur 7 to 10 years before actual operations begin.17,18,19 In addition, 5 to 6 years will likely be required for refinement and maturation of SRF-associated technologies for safely containing and handling samples to avoid contamination and to further develop and refine biohazard-test protocols. Many of the capabilities and technologies will either be entirely new or will be required to meet the unusual challenges of integration into an overall (end-to-end) Mars sample return program.  Unknown parameter | ignored (help)
  13. 13.013.1 "2: "The Potential for Past or Present Habitable Environments on Mars"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 28. The present committee found that the knowledge gained from both orbital and landed missions conducted over the past decade, combined with findings from studies of martian meteorites, has enhanced the prospect that habitable environments were once widespread over the surface of Mars. In addition, the potential for modern habitable environments, both as transient surface environments asnd as stable habitats in the deep subsurface, is much better understood. This understanding has, in turn, enhanced the possibility that living entities could be present in samples returned from Mars. Therefore the committee concurs with and expands on the 1997 recommendation that no uncontained martian materials should be returned to Earth unless sterilized. 
  14. Dwayne Brown, Sarah DeWitt NASA Announces Robust Multi-Year Mars Program; New Rover to Close Out Decade of New Missions
  15. Wall, Mike (September 27, 2012). "Bringing Pieces of Mars to Earth: How NASA Will Do It (note, proposed mission only)". Retrieved September 28, 2012. 
  16. Wall, Mike (September 27, 2012). "Bringing Pieces of Mars to Earth: How NASA Will Do It (note, proposed mission only)". Retrieved September 28, 2012. 
  17. [China to collect samples from Mars by 2030 Mars Daily, Oct 10, 2012
  18. Carl Sagan,The Cosmic Connection - an Extraterrestrial Perspective (1973) ISBN 0521783038
  19. Barry E. DiGregorio The dilemma of Mars sample return August 2001 Vol. 31, No. 8, pp 18–27. - for the quote from Carl Woese see his reference 54
  20. 20.020.1 International Committee Against Mars Sample Return.
  21. 21.021.1 Joshua Lederberg Parasites Face a Perpetual Dilemma Volume 65, Number 2, 1999 / American Society for Microbiology News 77.
  23. Genome Hunters Go After Martian DNA Antonio Regalado, Biomedicine News, MIT Technology Review, October 18, 2012
  24. Space Exploration Enabled by Telepresence: Combining Science and Human Exploration - Extended Version Findings and Observations from: “Exploration Telerobotics Symposium” May 2-3, 2012 NASA Goddard Space Flight Center]
  25. LOW-LATENCY TELEROBOTICS FROM MARS ORBIT: THE CASE FOR SYNERGY BETWEEN SCIENCE AND HUMAN EXPLORATION, Concepts and Approaches for Mars Exploration , First Exploration Telerobotics Symposium (2012)
  26. 26.026.1 M. S. Race Planetary Protection, Legal Ambiguity, and the Decision Making Process for Mars Sample Return Adv. Space Res. vol 18 no 1/2 pp (1/2)345-(1/2)350 1996
  27. 27.027.1 Exploring the Origin, Extent, and Future of Life: Philosophical, Ethical and Theological Perspectives Chapter 10, A Christian Perspective, Cambridge University Press, 3 Sep 2009
  28. Carl Woese The Birth of the Archaea: a Personal Retrospective
  29. Cambridge project | The Cambridge Project for Existential Risk
  30. Carl SaganCosmos Random House Publishing Group, 6 Jul 2011
  31. Assessment of Planetary Protection Requirements for Mars Sample Return Missions, National Research Council, 2009
  32. "5: The Potential for Large-Scale Effects"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 45. While the existence of habitable conditions provides no guarantee that life ever originated on Mars, the possibility has increased that a martian life form, whether active, dormant, or fossil, could be included in a sample returned from Mars. 
  33. "Assessment of Planetary Protection Requirements for Mars Sample Return Missions", National Research Council, 2009, chapter 3, "Advances in Microbial Ecology".
  34. "4: "The Potential for Finding Biosignatures in Returned Martian Samples"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 41. Geobiological studies of both modern and ancient Mars-relevant environments on Earth have highlighted the potential for samples returned from Mars to contain viable microorganism or their fossilized remains, while supporting the development of new approachs for in situ and laboratory detection of biosignatures in a variety of geological materials. 
  35. "5: The Potential for Large-Scale Effects"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 46. As reviewed in Chapter 3, extreme environments on Earth have not yet yielded any examples of life forms that are pathogenic in humans. However, it is worth noting in this context that interesting evolutionary connections between alpha proteobacteria and human pathogens have recently been demonstrated for natural hydrothermal environments on Earth, suggesting that evolutionary distances between nonpathogenic and pathogenic organisms may be quite small in some instances. It follows that, since the potential risks of pathogenesis cannot be reduced to zero, a conservative approach to planetary protection will be essential, with rigorous requirements for sample containment and testing protocols. 
  36. "5: "The Potential for Large-Scale Effects"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 47. If the 1:100 ratio is accepted as being representative, then of the roughly 500 meteorites that fall on Earth every year, perhaps five are from Mars. 
  37. 37.037.1 "5: "The Potential for Large-Scale Effects"". Assessment of Planetary Protection Requirements for Mars Sample Return Missions (Report). National Research Council. 2009. p. 47. Transit to Earth may present the greatest hazard to the survival of any microbial hitchhikers. Cosmic-ray-exposure ages of the meteorites in current collections indicate transit times of 350,000 to 16 million years. However theoretical modeling suggests that about 1 percent of the materials ejected from Mars are captured by Earth within 16,000 years and that 0.01 percent reach Earth within 100 years. Thus, survival of organisms in meteorites, where they are largely protected from radiation, appears plausible. If microorganisms could be shown to survive conditions of ejection and subsequent entry and impact, there would be little reason to doubt that natural interplanetary transfer of organisms is possible and has, n all likelihood, already occurred.

    ...It should be noted that martian materials transported to Earth via a sample return mission will spend a relatively short time (less than a year) in space - all the while protected in containers. (Note that researchers have yet to discover compelling evidence of life in any meteorite, martian or otherwise.) Thus the potential hazards posed for Earth by viable organisms surviving in samples is significantly greater with a Mars sample return than if the same organisms were brought to Earth via impact-mediated ejection from Mars.
      line feed character in |quote= at position 772 (help) Cite error: Invalid <ref> tag; name "nrc2009_5p48" defined multiple times with different content
  38. Benton C. Clark Martian meteorites do not eliminate the need for back contamination precautions on sample return missionsAdvances in Space Research Volume 30, Issue 6, 2002, Pages 1593–1600
  39. Planning considerations for a Mars Sample Return Mission
  40. European Science Foundation - Mars Sample Return backward contamination - strategic advice - (see Life as we know it and size limits, describes all the concerns mentioned in the paraphrase) - February 23, 2010
  41. [ Mars Sample Return Receiving Facility]
  42. 42.042.1 Barry E. DiGregorio The dilemma of Mars sample return August 2001 Vol. 31, No. 8, pp 18–27..
  43. Mars Sample Return: Issues and Recommendations(1997) Commission on Physical Sciences, Mathematics, and Applications (CPSMA) Space Studies Board (SSB) (page 31)
  44. NASA MSR Draft Test Protocol
  45. Leprosy Fact Sheet World Health Organization
  46. 46.046.1 European Science Foundation - Mars Sample Return backward contamination - strategic advice - (see 5.3 Direct consequences for human health) - July, 2012 Cite error: Invalid <ref> tag; name "esf2012_PP-precautionary" defined multiple times with different content
  47. Assessment of Planetary Protection Requirements for Mars Sample Return Missions (2009) Space Studies Board
  48. Wingspread Conference on the Precautionary Principle Wingspread, headquarters of Johnson Foundation, January 26, 1998
  49. 49.049.1 Safe methods for MSR
  50. ICAMSR list of advisors
  51. European Science Foundation - Mars Sample Return backward contamination - strategic advice July, 2012, ISBN 978-2-918428-67-1 - see 2. From remote exploration to returning samples. (for more details of the document see abstract )
  52. Life Marker Chip Robot Space Explorers, Open Universityy
  53. 53.053.1 Planning for Mars Returned Sample Science: Final report of the MSR End-to End International Science Analysis Group
  54. Cranfield Health Detecting life on mars and the life marker chip: Antibody assays for detecting organic molecules in Liquid extracts of martian samples Phd thesis, Supervisor: Professor David C. Cullen, January 2012
  55. [ Planning for Mars Returned Sample Science: Final report of the MSR End-toEnd International Science Analysis Group] Nov. 22, 2011
  56. Vision and Voyages for Planetary Science in the Decade 2013-2022
  57. Summary of the Final Report Mars Program Planning Group, 25 September 2012 MPPG
  58. Gaskin, J.A.; Jerman, G.; Gregory, D.; Sampson, A.R., Miniature Variable Pressure Scanning Electron Microscope for in-situ imaging & chemical analysis Aerospace Conference, 2012 IEEE , vol., no., pp.1,10, 3–10 March 2012 doi: 10.1109/AERO.2012.6187064
  59. Mars Sample Return Mission? Naaah… Just Beam Back Martian DNA
  60. Biomedicine News Genome Hunters Go After Martian DNA
  61. A. D. Anbar1 and G. V. Levin A CHIRAL LABELED RELEASE INSTRUMENT FOR IN SITU DETECTION OF EXTANT LIFE., Concepts and Approaches for Mars Exploration (2012)
  62. Andrew D. Aubrey,1 John H. Chalmers, Jeffrey L. Bada, Frank J. Grunthaner, Xenia Amashukeli, Peter Willis, Alison M. Skelley, Richard A. Mathies, Richard C. Quinn, Aaron P. Zent, Pascale Ehrenfreund, Ron Amundson, Daniel P. Glavin, Oliver Botta, Laurence Barron,1 Diana L. Blaney, Benton C. Clark,11 Max Coleman, Beda A. Hofmann,12 Jean-Luc Josset,1 Petra Rettberg, Sally Ride, François Robert, Mark A. Sephton, and Albert Yen1 The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration ASTROBIOLOGY Volume 8, Number 3, 2008
  63. J.L. Bada ·P. Ehrenfreund ·F. Grunthaner ·D. Blaney ·M. Coleman · A. Farrington ·A. Yen ·R. Mathies·R. Amudson ·R. Quinn ·A. Zent·S. Ride · L. Barron ·O. Botta ·B. Clark ·D. Glavin ·B. Hofmann · J.L. Josset·P. Rettberg · F. Robert ·M. Sephton Urey: Mars Organic and Oxidant Detector Space Sci Rev (2008) 135: 269–279
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  65. Jeff Foust A curious future for Mars exploration, Monday, August 13, 2012
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  67. Exploration Telerobotics Symposium website
  68. Space Exploration Enabled by Telepresence: Combining Science and Human Exploration - Executive Summary Based on Findings from: “Exploration Telerobotics Symposium” May 2-3, 2012 NASA Goddard Space Flight Center]
  69. 69.069.1 The Human Exploration of Space, By Committee on Human Exploration, National Research Council, 1997

    Using the return flight as an incubation period and the crew as guinea pigs (as has been suggested) is not a solution to back contamination on human missions. Would the whole mission be risked if an unanticipated contamination occurred? How would the cause of the infection be known with enough certainty to justify destroying the returning spacecraft before it entered Earth's atmosphere? The whole spacecraft, not only the astronauts, would be contaminated. In addition infection might not be the only risk. A returning organism could possibly cause some long-term changes in our environment, perhaps remaining undetected for a while. Although such an event may be judged to have a very low probability, a convincing case that prudence has been exercised will have to be made to the public. (Page 30)

  70. Carl Sagan,The Cosmic Connection - an Extraterrestrial Perspective (1973) ISBN 0521783038

    It is no use arguing that samples can be brought back safely to Earth, or to a base on the Moon, and thereby not be exposed to Earth. The lunar base will be shuttling passengers back and forth to Earth; so will a large Earth orbital station. The one clear lesson that emerged from our experience in attempting to isolate Apollo-returned lunar samples is that mission controllers are unwilling to risk the certain discomfort of an astronaut – never mind his death – against the remote possibility of a global pandemic. When Apollo 11, the first successful manned lunar lander, returned to Earth – it was a spaceworthy, but not a very seaworthy, vessel – the agreed-upon quarantine protocol was immediately breached. It was adjudged better to open the Apollo 11 hatch to the air of the Pacific Ocean and, for all we then knew, expose the Earth to lunar pathogens, than to risk three seasick astronauts. So little concern was paid to quarantine that the aircraft-carrier crane scheduled to lift the command module unopened out of the Pacific was discovered at the last moment to be unsafe. Exit from Apollo 11 was required in the open sea.

  71. Richard S. Johnston John A. Mason Bennie C. Wooley, Ph.D.[*] Gary W. McCollum Bernard J. Mieszkuc BIOMEDICAL RESULTS OF APOLLO, SECTION V, CHAPTER 1, THE LUNAR QUARANTINE PROGRAM Lyndon B. Johnson Space Center
  72. DAVID S. F. PORTREE Antaeus Orbiting Quarantine Facility (1978) 7th July, 2012