Planetary protection for a Mars sample return



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.

The NRC and ESF studies concluded that, though the potential for large-scale negative effects appears to be very low, it is not demonstrably zero, and that the samples should be treated as biohazardous to the environment of Earth until shown to be safe.

Most participants are agreed that a MSR should be carried out eventually. There is however considerable diversity of views on the details of how a MSR should be conducted, both for reasons of contamination and science value. This is the subject of this article.

The NRC and ESF findings on risks of environmental disruption are accepted by most participants in this debate (with the notable exception of Robert Zubrin ). As a result, it is agreed by most researchers that a full and open public debate of the back contamination issues is needed at an international level. This is also a legal requirement.

Plans to return a sample to Earth before detailed examination
A Mars Sample Return (MSR) to the Earth surface has been considered many times since the first proposal in 1979, due to the high science value expected for carefully selected samples from Mars examined with the full range of facilities we have available on Earth.

NASA's Mars 2020 rover will cache samples which they hope to return direct to Earth in the 2020s, possibly as soon as 2026.

There have been many previous plans by NASA in the Mars Next Generation program. China also has considered a plan to return a sample by 2030.

Samples returned under these proposals would be examined for biosignatures on Mars first, but the proposals suggested so far for a MSR to Earth do not include any plans for detailed examination on the Mars surface, such as with Scanning Electron Microscopes, DNA sequencers, or labelled culture experiments. Also the plans proposed so far do not include tests for biohazard potential in Earth-like environments prior to return to Earth. All these tests would instead be carried out on Earth after the sample return mission.

As a result, these plans depend on adequate containment of the samples during the return journey and in the receiving facility on Earth until the tests can be completed on Earth.

View presented in the NRC and ESF study group reports and Planetary Protection Office summaries
The view in the reports from the National Research Council and the European Space Foundation,  as well as the Planetary Protection office is as follows:

To deal with these issues, the NASA Office of Planetary Protection recommends construction of a special a Mars Receiving Facility. They recommend that the facility should be operational at least two years prior to launch, with various estimates on the time taken to build the facility and bring it to operational readiness. Preliminary studies have warned that it may take as many as 7 to 10 years to get it operational.

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

The aim of this article is to present in detail some of the varying viewpoints on the back contamination risks and the science 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.

Concerns and issues raised
First a brief overview of the issues.


 * Some researchers   are mainly concerned about issues of back contamination of Earth by accidentally released Martian micro-organisms.
 * Others are concerned about the high cost of a MSR on the basis that it will be some time before we know enough about Mars to select suitable samples to examine on Earth, and until then, run a high risk of returning bioligically uninteresting samples.
 * Others are concerned that any samples would be contaminated by Earth life during the return journey, so reducing their value for scientific research.

These issues of back contamination of Earth, selection of interesting samples on Mars, and sample contamination by Earth micro-organisms, are also raised in the official reports as well. It is generally agreed by almost all researchers that these are issues that need to be addressed in any plans for a MSR.

Back contamination concerns for a Mars sample return
These concerns were originally raised by Carl Sagan in 1973 in his book the Cosmic Connection, and Carl Woese., and later by Lederberg

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

Carl Sagan wrote in his book Cosmic Connection:

These concerns centre on the biohazard potential of martian lifeforms

Biohazard potential of martian life
The potential of Martian life to create a biohazard on Earth was first raised by Carl Sagan in 1973 in his book "Cosmic Connection". The concern has been reviewed many times since then with the same or similar conclusions.

Sagan wrote:

The microbiologist Joshua Lederberg made a similar point

These early concerns have been repeated in the detailed assessments by later study groups.

National Research Council review of biohazard potential of returned samples
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". They confirm the earlier concerns as still a matter that needs attention.

This report is the basis for the later 2010 ESF report which is in agreement with its conclusions about the biohazard potential of any mars sample return.

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".


 * 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 noted the discovery of new organisms and ecological interactions. They also noted the discovery of novel single-species ecosystems such as the one inhabited solely by the chemoautotrophic Candidatus Desulforudis audaxviator. Their conclusion was that these researches highlighted the potential of micro-organisms adapted to live in the Martian environment.


 * 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.


 * Would the sample include micro-organisms not already delivered to Earth on martian meteorites? To assess this, they estimated that several meteorites a year probably impact Earth from Mars. So the transfer of sufficiently hardy life forms from Mars to Earth via meteorite seems plausible. However, they observed that meteorites in current collections spent from 350,000 to 16 million years in space, and though theoretical models show that shorter transition periods are possible, concluded that the much shorter transit time of a sample return protected in a container could preserve lifeforms that would not survive the passage on a meteorite.


 * 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.

Their overall conclusion was:

As with previous reports, the latest 2009 study recommended that the sample be treated as a biohazard until proved otherwise.

ESF update on biohazard risks of MSR
The ESF report accepts the general conclusions of the NRC report, but went beyond them in several areas. In particular they made a more detailed assessment of size limits of micro-organisms. Before this study, the accepted size limits were 0.25 µm, derived from a 1999 workshop.

The 2010 ESF study observed that the Mars sample could contain uncultivatable archaea, or ultramicrobacteria. It might contain Martian nanobacteria 0.1 µm 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 based on novel life chemistry, which makes it hard to set an absolute lower size.

For the nanobacteria, they accepted recent research that show these 0.1 µm sized cell like objects are mineral deposits, so ruled them out. They discussed ultramicrobacteria and concluded that the smallest free-living self-replicating microorganisms observed are in the range of 0.12–0.2 µm.

They considered viruses, i.e. bacteriophages and viruses of archaea. These they considered unlikely to be of concern if released from containment on their own, separately from their putative martian micro-organism host, because they require specific host adaptations to infect Terrestrial micro-organisms.

They then studied GTAs, which cause cross species transfer of DNA in some species of archaea and bacteria. Here they are referring to research reported in Nature and Science in 2010 (after the NRC report). In one striking experiment the researchers left GTAs (conferring antibiotic resistance) and marine bacteria overnight in natural conditions and found that by the next day up to 47% of the bacteria had incoroproated the genetic material from the GTAs :

As a result of reviewing this research, the ESF study group concluded that the risk from virus type and GTA type entities is lower than for self replicating entities and "almost negligible" but still can't be demonstrated to be zero and should be taken account of in their minimum size recommendations.

As a result, they recommended a minimum size of 0.01 µm on the basis that this is nearly half the size of the smallest GTAs known and less than a tenth of the size of the smallest currently known free-living self-replicating microorganisms.

In the case where 0.01 µm can't be achieved at a reasonable cost, and in view of the almost negligible risks from GTAs, they give 0.05 µm as a maximum permitted minimum size. This size was chosen as less than half that of the smallest currently known micro-organisms - so unlikely to contain a free-living microorganism. They recommend that such an increase of the minimum size requirement requires independent review by a panel of experts.

However, in 3.7 Perspectives for the future, they added a caution that it is likely that minimum size limits for viruses and GTAs or free living organisms will reduce further in the future. They thought it unlikely that such a large reduction in size limits will happen again as happened after the 1999 report, though that possibility also can't be completely ruled out. . They recommended that the size limits should be continually reviewed depending on the latest research.

Risk Mitigation for back contamination
NASA has addressed back contamination concerns with a proposal to build a special biohazard containment facility to receive the samples, and with a sample return mission designed to break the chain of contact with Mars for the exterior of the sample container

In the European Science Foundation study, these risks were studied in more detail and recommendations made to reduce them to levels considered acceptable.

Concerns with integrity of the sample container
The 2010 ESF report considers several possible failure modes with the sample container.


 * 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".


 * If any part of the capsule exterior can be contaminated by Mars materials this provides a possibility of contamination of Earth.


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

Risk mitigation for sample container

 * Risk of rupture: This risk is reduced by requiring that the capsule is capable of withstanding the shock of impact at terminal velocity.


 * Risk of leaks or micrometeorite penetration: These risks are reduced by using multiple seals and use of methods to detect such leaks if they occur.


 * Risk of exterior contamination This risk is managed by a mission design that ensures that no surface that is exposed to the Mars environment is exposed to Earth. One way of doing this is to send another spacecraft to retrieve the container which receives it within the vacuum of space into a larger sealed container that has never been exposed to Mars and then is sealed and returned to Earth.


 * Human error: This risk is reduced by training, redundancy, and making sure critical decisions are not made by tired astronauts.

Issues due to novelty of the proposed Biohazard facilities
This describes the issues, see the risk mitigation section for the solutions proposed for these issues.

The facility must also double as a clean room, to keep Earth micro-organisms away from the sample. As a result, 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. [NEEDS CITE - NOT IN ESF REPORT]

The ESF report says that biohazard facilities are designed to contain known hazards. The new facility must contain unknown hazards as well and knowledge about Mars biology (if any) will have a steep development curve..

Other risks mentioned in these studies, and by the Planetary Protection Office include the possibility of human error, accidents, natural disasters, security breach, actions by terrorist or 'activist' groups or crime, leading to release of the materials, once the samples are on the Earth surface.

Target probabilities for proposed biohazard facilities
The space studies board study recognised that the risks of release of hazardous particles from a MSR receiving facility can't be reduced to zero. So it is necessary to set a target probability of release that you aim to achieve.

One suggestion for an acceptable level of risk was recommended by the ESF-ESSC Study Group

Risk mitigation for the MSR receiving facilities
To deal with the issues of unknown possibly very small forms of life in the sample, the ESF referred to their discussion of size limits (above) and concluded (Recommendation 7) that if possible, the facilities should be designed so that probability should be less than one in a million that a single unsterilised particle of 0.01 µm diameter or greater, if possible, and if that's not possible, that

To deal with issues of the novelty of the facilities and of human error, the studies recommended that the receiving facility is operational and the staff trained several years before the Mars samples are brought into Earth's environment. The 2008 report of the IMARS working group report detailed a total of twelve years from initial planning to lander launch. Three architectural firms were approached who provided preliminary plans, the FLAD, IDC and LAS plans, the last of these, the LAS has a fully robotic work force to handle the samples.

They were not asked to consider human factors and so do not report on ways to mitigate these, except to suggest that care must be taken to minimize human interaction with the sample.

Concerns about incubation period
Carl Sagan first raised this concern:

The WHO Leprosy fact sheet 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

Risk mitigation for incubation period
The ESF report cite incubation period as one of the risk factors that make it "impossible to model the consequence of the potential release of a Mars organism".

They observe that if the onset is slow and the effects are not unusual, significant spread may occur before the nature of the threat is realised.

They recommend that potential release scenarios (including undetected release) are clearly defined and investigated, and response strategies developed for them.

They considered it critical that such containment strategies are implemented as soon as possible at the local level, and that they should include rapid detection of anomalies, effective warning procedures, and analysis, resistance and mitigation procedures.

Dissenting views of the ICAMSR on back contamination risks of a MSR
The International Committee Against Mars Sample Return (ICAMSR) is an advocacy group of scientists campaigning against plans for a fast MSR direct to Earth.

They take the stance that a sample return to the Earth surface should not be carried out at this stage, and that the samples need to be certified as "biosphere safe" in space or in-situ before they are transferred to the Earth’s surface. They cite as their main inspiration, Carl Sagan, who advocated considerable caution before samples are returned to Earth.

The ICAMSR are especially concerned, as was Carl Sagan, that a significant component of risk in biohazard release is the risk of human error, which has happened several times during the Apollo era attempts at containing the lunar samples. In particular they cite the example of an incident during the recovery of the Apollo 11 astronauts at sea. The hatch of the module was opened by divers, while the module was still in the sea, permitting lunar dust and any airborne micro-organisms to exit the module and enter the sea, in breach of the previously established planetary protection protocol for this landing.

Views of the 2002 COMPLEX study of lessons to be learnt from the Apollo quarantine
The 2002 COMPLEX study reviewed the experience of the Apollo missions and came to the conclusion that handling of samples was successful even though the quarantine was a failure. They point out that a MSR would not have this human quarantine element.

Should a vigorous program of Martian exobiology be carried out first?
Carl Sagan recommended that a "vigorous program of unmanned Martian exobiology and terrestrial epidemiology" should be undertaken first, before any Mars sample return.

Michael Meyer, of the NASA exobiology department pointed out that Curiosity " is the first astrobiology mission since Viking in 1976". It is the first mission since Viking to directly search for biosignatures.

Curiosity is limited in its capabilities for exobiology, and s is only a first step in the exobiology research phase. 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.

Carl Sagan wrote in Cosmos:

Probability assessment issues
The ESF study found that it is generally agreed that the probability that any martian micro-organism is biohazardous is low. However as no life forms outside of Earth have yet been studied or characterized, it is impossible to do a standard probability assessment.

This is covered in 4.2 Approaching the unknown and considering consequences in the ESF report, under unknown unknowns:

They concluded that risk assessment has to be carried out by combining knowledge of Earth life with knowledge of Martian geology. They found that it is possible to establish the risk as low, as a consensus of the beliefs of the experts in the field as represented by their experience."

Risk assessment survey of microbiologists
In 1998, the ecologist Margaret Race of the SETI Institute with Donald MacGregor of Decision Research carried out a survey of microbiologists attending a special five-session colloquium titled “Prospecting for Extraterrestrial Microorganisms and the Origin of Life: An Exercise in Astrobiology”. This survey showed a wide diversity of views amongst microbiologists, when asked for opinions on, for instance, whether there is life on Mars, and whether it could pose a threat to Earth. To assist editors in verifying accuracy of the paraphrase

This survey shows the diversity of views amongst microbiologists with a special interest in astrobiology, and so may help as background for the ESF comments about uncertainty of probability assessments.

Caution, the respondents views were based on 1998 technology and science in a rapidly developing field. So is based on the biohazard containment capabilities, in situ analysis capabilities, and understanding of exobiology of the time. It is more useful as a way of indicating possibilities of a diversity of views, than as a direct indication of present day views amongst astrobiologists.


 * Asked if they thought there is life on Mars, 40.3% agreed and 32.3% said “don’t know".
 * Asked whether life on Mars could pose a biological threat to Earth, 42.8% said “don’t know.”, 34.4% disageed, and 22.9% agreed.
 * Asked about our ability to predict with reasonable certainty how life elsewhere would impact our environment, 71.2% disagreed and 10.4% said "I don't know".
 * Asked about various quarantine proposals, approximately half of respondents said that the (then) current proposed methods of quarantine of the samples are either moderately or highly adequate. About a third said “don’t know,”
 * Asked if materials returned to Earth from Mars should be considered hazardous until proven otherwise, all agreed except for 1.5% saying “don’t know,”
 * Asked about the potential for in situ experiments done on the Martian surface to sufficiently determine the safety of Mars samples; 58.2% disagreed, and 21.9% said "Don’t know.”

The authors caution however

Precautionary Principle, Legal situation and need for international public debate
By the Precautionary principle, as described in the Wingspread conference., a key principle in political decision making, and law:

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

They continue:

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

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.

They consider it important to educate the public on the nature of the risk and to monitor and react to public perception of risk of MSR.

Legal liability in case of damages
The ESF report considered this and came to the conclusion that 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.

They also examined the case where the damages occur as a result of release after the capsule has returned to an Earth laboratory. They concluded that in this case 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.

Legal process of approval for Mars sample return
Margaret Race has examined in detail the legal process of approval for a MSR. She found that under the National Environmental Policy Act (NEPA) (which did not exist in the Apollo era) a formal environment impact statement is likely to be required, and public hearings during which all the issues would be aired openly. This process is likely to take up to several years to complete.

During this process, she found, 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. She concluded that the public of necessity has a significant role to play in the development of the policies governing Mars Sample Return.

Requirement for public debate
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.

The last case of "Humans could also be threatened with death or a significant decrease in life prospects" brings this into the region of existential risks.

He argued that this makes it not a technical problem for scientists to study but an ethical problem requiring extensive public debate at the international level.

He puts forward four criteria to ensure a full and open public debate.


 * 1) Follow best practises of planetary protection (already being done).
 * 2) Opportunities should be avaliable for open comment from those concerned about back contamination. These should be taken seriously and NASA should publicly respond to them.
 * 3) A committee should review the measures, including experts in ecology, biology, chemistry, risk analysis and ethics. Ethicists should represent a diversity of philosophical and religious perspectives.
 * 4) The entire process must be transparent to the interested public.

Potential value of Mars sample return for science
The science potential is the main motivation for the mission, and so needs to be considered in any assessment of MSR plans.

The ESF report highlights the value of a MSR for understanding history of Mars, its geology, volatiles and climate, and for insights into exobiology. They also state that it is an essential preliminary for human explorations to Mars.

They consider that in situ robotic missions will not be able to analyse the samples with the necessary levels of detail. They also point out that any returned samples can be reanalysed many times over using any of the extensive facilities available on Earth.

They also point out its value for engagement of the public with space related activiites, and excitement for the public.

See also the section: scientific value for the Mars sample return mission.

Timing concerns for a Mars sample return
There are many potential issues concerning the timing of a Mars sample return. Some questions that need to be considered before return of samples to Earth are:


 * Should a Mars receiving facility be constructed first?
 * Should samples be examined for biosignatures and geological context on Mars first?
 * Should samples be examined for signs of life first with advanced tools such as Scanning Electron Microscopes, DNA sequencers, or labelled culture experiments on Mars?
 * Should they be tested for their biohazard potential in Earth like environments on Mars or in orbit (around Mars, the Earth or the Moon), before return to Earth?

Most researchers are agreed on the first two points but there are dissenting views on the remaining two.

Mainstream view - a MSR can be undertaken at an early stage, but needs additional precautions
Many scientists accept that a Mars Sample Return can be done with an acceptably low probability of an adverse outcome, provided that the recommendations of the study groups are carried out. On this view, then the Mars receiving facility needs to be up and running two years before the return. However there is no need for detailed examination of the samples before return. A record of the geological context of each sample is essential. Some biosignature testing is recommended to help select interesting samples.

ICAMSR Charter - certified safe in situ or in space first
The ICAMSR have as their main goal, that samples are certified safe in situ or in space first before they are returned to Earth.

Recommendation of continued in situ study first - white paper for decadal review
This is a white paper submitted for the decadal review by eight authors from the NASA Jet Propulsion Laboratory, the Scripps Institution of Oceanography, SETI Institute, NASA Ames Research Center and the University of California Berkeley.

These authors argue that we do not yet know enough to intelligently select samples for return. They recommend a "Follow the Nitrogen strategy for in situ exploration".

They recommend that a MSR should be delayed until unambiguous biomarkers are identified in prospective Mars samples. They argue that there is a risk that samples returned at our current level of understanding may in the worst case be "as ambiguous with respect to the search for life as ALH84001."

For return of biologically interesting samples, they require ability to identify, in situ:


 * Biomarkers and unequivocal biosignatures stable over geological timescales. Examples: ability to detect chirality, and primary amine distribution.
 * Samples suitable for preserving life, and of preserving organics without significant degradation over geological time periods. Examples: sulfates, haliites, clays and the polar layered deposits
 * Nitrogenous organic compounds
 * Minute trace amounts of organics

They also recommend:
 * Any extraction methods used must preserve the target organic molecules with low degradation
 * Drilling must be carried out to the greatest depth possible, to allow for greatest chance of success for detecting organics and biosignatures.

Paige 's view
Paige raises similar concerns. He refers to a 1996 study requested by Michael Meyer of NASA’s Exobiological Program Office. This divided Mars exploration into five phases including:


 * Phase 1. Global Reconnaissance, focusing on past and present role of water, and identification of sites for detailed study.
 * Phase 2. In-Situ Exploration of Promising Sites, focusing on geologic, mineralogic, elemental, and isotopic characteristics, abundance and distribution of volatile species and organic molecules.
 * Phase 3. Deployment of exobiologically-focused experiments, and search for biomarkers of formerly living organisms, and extant life.
 * Phase 4. Robotic Return of Martian Samples to Earth, to improve characterization of organic compounds, and verify any evidence for biomarkers and extant life discovered in Phase 3.
 * Phase 5. Human exploration for detailed scientific characterizations of sites of unusual biologic interest, or inaccessible to robotic exploration.

Paige reasons that Mars exploration is still in phases 1 and 2, and that we need to complete phase 3 before going on to phase 4.

Suggested near future methods for selection of samples of biological interest
Some of the decadal review white paper, and Paige's 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.

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.

Issues to do with contamination of a returned sample by terrestrial DNA (Craig Venter)
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. Craig Venter's view is that this is best done in situ on Mars.

His motivation for this 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 any experiments to test for presence of martian DNA on the sample.

Space Studies Board recommendations to avoid biological contamination of the returned sample
The Space Studies Board raise similar concern but believe biological contamination of the returned sample can be avoided by suitable decontamination procedures. This is from the 2011 review of the Space Studies Board, 





Robert Zubrin's view that back contamination risk has no scientific validity
Robert Zubrin, president of the Mars society, presented this view in a published article and in interview. This is a transcript of an interview with him on March 30, 2001. First he refers to research that shows that the interior of a meteorite from Mars can remain below 40C throughout it's journey to Earth, and so is not sterilized, and then continues.

His current view however is that no MSR is needed at all before human colonization, see

NRC conclusions on relevance of martian meteorites to back contamination risks
This is considered in the NRC report. They observe that a sample return is returned directly from Mars over a short time period, with no impact shock and protected in a capsule. They observe that though meteorites from Mars reach Earth every year, they are ejected from Mars only rarely in the larger impacts (large impacts are needed to achieve escape velocity).

Taking into account theoretical models, and measurements of aging of meteorites through cosmic radiation, they conclude that when there is a large impact on Mars, most of the debris takes a time period of between hundreds of thousands and millions of years to reach Earth, and during that time period much of any dormant life is sterilized by cosmic radiation. A small fraction, 0.01% is expected to reach Earth in less than a century, and some of the material is only lightly shocked. So transfer of life from Mars to Earth does seem possible but likely to happen rarely, and more common in the early solar system.

They considered reports of micro-organisms with radiation resistance adaptations that have been suggested as possible candidates for micro-organisms that have come from Mars originally, and conclude:

Alternatives to an early return of Mars samples to the Earth's surface
Several suggestions have been made to deal with the scientific, or biohazard, concerns about an early sample return to Earth.

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, either before or after study on the surface.

With most of these approaches, Mars sample return would be expected eventually. The timing depends on the approach. For instance with the Bada and Paige suggestions, sample return would occur once samples are found with clear evidence of present or past life, or evidence of biosignatures in the present or past. With the telerobotics approach, sample return is done to Earth after preliminary study in orbit around Mars. With Zubrin's approach, sample return is done at a much later stage after human colonization of Mars. With Levin's approach, sample return is done after a series of biohazard testing experiments have been completed in situ on Mars, and in orbit.

Extensive study of the samples first on the Mars surface


We have seen that several authors recommended in situ survey first and and Paige predicted that new instruments under development will make it possible to analyse rocks in situ on Mars, permitting a flexible approach where rovers can make new choices of targets of potential biological interest on the surface of Mars based on findings for the samples encountered earlier in the mission.

This is list of a few of the instruments under development for future Mars missions that permit or will permit 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.


 * Jonathan Rothberg, and J. Craig Venter, are separately developing solutions for sequencing alien DNA directly on the Martian surface itself.


 * 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.


 * The Urey Mars Organic and Oxidant Detector instrument for detection of biosignatures due to be flown on ExoMars in 2018. It is designed with much higher levels of sensitivity for biosignatures than any previous instruments

Vigorous study of the Mars surface instead of a sample return
Dirk Schulze-Makuch and Robert Zubrin have both taken this view, that a vigorous continuing study of the Mars surface would be more beneficial than a MSR at the current stage of exploration of Mars, though for rather different reasons.

Dirk Schulze-Makuch's view that from an atrobiological standpoint, in-situ research is better and cheaper than MSR
This view was given in an interview for space.com of astrobiologist Dirk Schulze-Makuch

He (along with other researchers) has published his own proposal for a mission called BOLD to send many penetrator probes to Mars to sample it sub surface and seek signs of life

Robert Zubrin's view that there is no need for a MSR before human colonization of Mars
Another advocate of vigorous study on the surface in place of a MSR at the current stage of exploration of Mars is Robert Zubrin, president of the Mars Society. He sees value in scientific study of Mars before a human colonization, but is of the opinion that the same objectives are better met using a vigorous program of robotic exploration.

He suggests an initial exploration stage with many rovers on the same model as Curiosity. As additional motivation for his approach, he suggests that humans post colonization of Mars can do far better sample return missions than a robotic mission can do now.: To assist editors in verification of paraphrase of Zubrin's views from: A curious future for Mars exploration

Then, writing an article himself in Space News in Dec. 3, 2012, he says as additional motivation for his approach, that humans post colonization of Mars can do far better sample return missions than a robotic mission can do now: from: Mars the Hard Way Space News, Dec. 3, 2012

Study In Situ followed by Return to the ISS or Earth orbital laboratory first
Gilbert Levin is motivated by concerns for back contamination of Mars, following the inspiration of Carl Sagan. For this reason, he recommends a 10 step sequence for returning Martian samples to Earth

His suggestion starts with a series of tests for micro-organisms in situ on Mars, including tests for biohazard potential to whatever extent is possible on Mars. They are then returned 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 (similarly to the ESF / NRC proposals). Once the samples are returned to Earth he recommends that laboratories should be provided for researchers all in the same location, rather than to send the samples to researchers in other locations for testing.

Issues with the use of quarantine periods in space to contain any biohazard
A 1997 study by the National Research Council found some issues with the use of humans in quarantine which would need to be addressed with any proposal that involves human quarantine, such as Levin's. 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?

In the case of NASA's Lunar quarantine at the time of Apollo 11, one of the guiding principles permitted breach of quarantine in the case of danger to human life:

Indeed in practise containment was breached for a lesser reason than preservation of life; it was breached in order to prevent seasickness of the Apollo 11 astronauts during the sea landing. As Carl Sagan wrote about this incident:

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 it is unclear how much extra protection quarantine provides.

Another issue raised with this approach 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. There is also the issue of the latency period, that the astronauts may not show any signs of infection until after return from Earth.

The NRC study concluded that as a result of these issues, the human quarantine approach does not give guarantee of containment of any issues found.

Jeffrey Kargel in "Mars - A Warmer, Wetter Planet" considers an alternative possibility to death of the astronauts when he discusses the possibility of an indefinite quarantine in the case that an issue is found during the quarantine period. He has doubts about the workability of an indefinite quarantine on the Moon, and feels that a quarantine on a space station can't remain isolated indefinitely due to it's low orbit and need to resupply, and suggests that "the most effective and practical lifetime quarantine would be on Mars".

Study via telepresence from Mars orbit, followed by return of the sample to Mars orbit


During the “Exploration	Telerobotics	Symposium" in 2012 experts on telerobotics from industry, NASA and academics met to discuss telerobotics, and its applications to space exploration. Amongst other issues, particular attention was given to Mars missions and a Mars sample return.

They came to the conclusion that telerobotic approaches could permit direct 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.

They found that telepresence exploration of Mars has many advantages. The astronauts have near real-time control of the robots, and can respond immediately to discoveries. It also prevents contamination both ways and has mobility benefits as well.

Return of the sample to orbit has the advantage that it permits analysis of the sample without delay, to detect volatiles that may be lost during a voyage home. This was the conclusion of a meeting of researchers at the NASA	Goddard	Space	Flight	Center in 2012.

For more about exploration of Mars via telepresence, see Exploration of the surface from orbit, via telerobotics and telepresence

Advocacy of early Mars sample return
Some researchers and mission planners have put forward strong advocacy for an early Mars sample return. In particular this was one of the main conclusions of the 2011 decadal survey, an extensive survey of the community of active planetary scientists carried out every ten years in the USA.

The 2011 survey strongly advocated a Mars Sample Return program as the top flagship mission, to be carried out in several stages (with the mission to Europa proposal second).

In this survey, it was descoped due to cost considerations but the science value was considered high.

In favour of the value of sample return they cite results from previous sample returns and their analogues (e.g., of meteorites, the Moon, cometary dust, and the solar wind) and point out that the Martian meteorites known are from a limited range of rock types, so that carefully selected samples returned from Mars can greatly increase our understanding of the planet. To assist editors with verification

Some quotes from the survey report follow to show how highly the mission was valued in the survey:

These views were later summarizes as:

In the summary of the final report of the Mars Program Planning Group in September 2012, two main possibilities were considered:


 * Search for signs of past life with samples collected from a site identified using exising data and returned to Earth for analysis (pathways A1 and A2)


 * 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 (pathway A3)

They comment that the first option (their pathways A1 or A2) is most directly responsive to the NRC Decadal Survey recommendations.



Historical background
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.

Other proposals were explored in the 1980s, including direct entry of sample container to Earth's atmosphere, recovery by the space shuttle, recovery to space station, recovery to a dedicated Antaeus space station, and several intermediate proposals.