Mars Sample Receiving Facility and sample containment

MSR pages: MSR facility - Legal Issues - science value - Dissenting views on back contamination risks



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.

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.

Because of these concerns, there are proposals to build a Mars Sample Receiving Facility. This needs to be of a novel design, as it has to function both as a clean room and as a biohazard laboratory . It also has to contain possibly novel unknown lifeforms.

The view of NASA, the ESA and the Office of Planetary Protection is that these risks can be contained and that a sample return can be carried out safely provided the correct precautions are taken. The reports stress the need for these precautions. The ESF report, for instance, recommends that release of a Martian particle under 0.05 microns is unacceptable under any circumstances.

This page covers the results of studies by NASA and the ESA which examine the need for such a facility, and the risks that need to be mitigated. It also looks into issues of sample containment during return from Mars.

Note that Some exobiologists believe that more in situ observation is needed first for practical reasons and reasons of cost benefit. There are also minority view dissenters who disagree with the proposed plans. Zubrin considers them to be too cautious and the ICAMSR consider that stronger precautions are required.

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 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. 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 Science 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 the results of the official NASA studies on the back contamination risks and the science benefits of a Mars sample return and the methods for risk mitigation.

The views of the ICAMSR (advocates against Mars sample return to Earth) and of Zubrin (advocate of the view that back contamination is not a legitimate scientific concern) will be left for separate discussion in another article.

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 - historical background
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 - historical background
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.

The ESF report also points out that biohazard facilities are designed to contain known hazards. The new facility must contain unknown hazards as well. It's a much harder problem to contain unknown hazards, especially with the diversity of life forms now known to be potentially hazardous such as GTAs and ultramicrobacteria (as described above).

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 Science 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.

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.

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
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.

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.


 * 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



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.

Page history
The old version is currently still available at [] along with its page history.