Planetary protection for a Mars sample return: Difference between revisions
Planetary protection for a Mars sample return (edit)
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They divide it into 3 categories
{{bq|* Large-scale negative pathogenic effects in humans;<br>* Destructive impacts on Earth's ecological systems or environments; and<br>* Toxic and other effects attributable to microbes, their cellular structures, or extracellular products.}}[http://www.nap.edu/openbook.php?record_id=12576&page=45 (page 45)]
{{bq|▼
They conclude that the last one is unlikely. But for the other two
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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 degradation|environmental disruption]] are accepted by most participants in this debate (with the notable exception of Robert Zubrin<ref name=zubrin>Robert Zubrin "Contamination From Mars: No Threat", [http://www.planetary.org/explore/the-planetary-report/ The Planetary Report] July/Aug. 2000, P.4–5</ref><ref name=zubrin-interview>[http://astronomy.nmsu.edu/cwc/Teaching/SpaceCol/sts497i/Zubrin/transcript.txt transcription of a tele-conference interview with ROBERT ZUBRIN] conducted on March 30, 2001 by the class members of STS497 I, "Space Colonization"; Instructor: Dr. Chris Churchill</ref>). 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.<!--(NASA and ESF surveys both say this as well as other sources e.g.) --><ref name=esf2012_PP-debate>{{cite report |title=Mars Sample Return backward contamination - strategic advice |publisher= European Science Foundation |year=2012 |chapter=5: "The Potential for Large-Scale Effects"|url=
Considering the global nature of the issue, consequences resulting from an unintended release
could be borne by a larger set of countries than
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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.''}}</ref> This is also a legal requirement.<ref name=esf2010_RALOS>[
==Plans to return a sample to Earth before detailed examination==
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The view in the reports from the National Research Council<ref name=nrc2009>
{{cite report |title=Assessment of Planetary Protection Requirements for Mars Sample Return Missions |publisher=National Research Council |year=2009 |chapter=2: "The Potential for Past or Present Habitable Environments on Mars" | url=http://www.nap.edu/openbook.php?record_id=12576&page=22}}</ref> and the European Space Foundation,<ref name=esf2012_PP>[
{{cite report |title=Mars Sample Return: Issues and Recommendations (Planetary Protection Office Summary) |publisher=Planetary Protection Office |year=1997|url=http://planetaryprotection.nasa.gov/summary/msr|quote=''The potential for large-scale effects, either through pathogenesis or [[Environmental degradation|ecological disruption]], is extremely small. Thus, the risks associated with inadvertent introduction of exogenous microbes into the terrestrial environment are judged to be low. However, any assessment of the potential for harmful effects involves many uncertainties, and the risk is not zero. ... The SSB task group strongly endorses NASA’s Exobiological Strategy for Mars Exploration (NASA, 1995). 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.''}}</ref> is as follows:
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=== 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 <ref name=esf2010_3size>[
The 2010 ESF study observed that the Mars sample could contain [[Archaea#Species|uncultivatable archaea]], or [[ultramicrobacteria]]. It might contain Martian [[Nanobacterium|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.<ref name=esf2010_LAWKI>[http://science.nasa.gov/media/medialibrary/2013/01/17/ESF_Mars_Sample_Return_backward_contamination_study.pdf European Science Foundation - Mars Sample Return backward contamination - strategic advice] - (see Life as we know it and size limits) - February 23, 2010</ref> 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.
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==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<ref name=esf2010_PP>[
In the European Science Foundation study, these risks were studied in more detail and recommendations made to reduce them to levels considered acceptable.
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=== Concerns with integrity of the sample container ===
The 2010 ESF report<ref name=esf2012_PP-capsule-breach>{{cite report |title=Mars Sample Return backward contamination - strategic advice |publisher= European Science Foundation |year=2012 |chapter=4.7 Potential verification methods"|url=https://science.nasa.gov/science-pink/s3fs-public/atoms/files/ESF_Mars_Sample_Return_backward_contamination_study.pdf}}
The 2010 ESF report<ref name=esf2010_PP/> considers several possible failure modes with the sample container.▼
▲{{bq|
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4.7 Potential verification methods
Verification of sterility of the surfaces of spacecraft elements that come into contact with the Earth’s biosphere, either upon return from the Mars surface or due to re-contact at some later date, is difficult. Sensory indications are often not reliable enough to be consistent with the 10-6 requirement. Because of this, only indirect methods of verification might be used. These include exclusion of potential particles from the spacecraft surfaces in the first place, sterilisation of the surfaces at some point prior to re-entry into the Earth’s biosphere by direct or indirect means such as re-entry heating, and ensuring that surfaces are not contaminated after sterilisation via leakage. Initial sealing of the Mars sample can be assured to a high level of reliability via the use of a proven container concept along with a sealing concept that has been shown to be reliable to first order with a sensory back up system, utilising outgassing for example. Although sensory systems are limited, as previously mentioned, the combined low risk of failing to create a seal in the first place and the additional conditional probability of detection using leak detection sensors, should be able to provide the required level of assurance that the sample is encased within the magazine consistent with the risk of release requirement. However, it is possible that the sample magazine could be penetrated by a micrometeoroid during transit from Mars, thereby causing exterior contamination and release upon entry. While sensory systems that detect leakage might be limited in risk protection, potential sensory systems that would detect any penetration of the Earth Return Vehicle to a high level of reliability should be feasible. Upon return to Earth, the sample would still have to be transported from the landing site to the curation facility. While the Study Group was not tasked with considering human factors, it has to be highlighted that the use of human handling in this process and the transport itself entails the risk of human error and the potential for accidental release. For this reason, care must be taken to minimise human interaction with the sample and to provide adequate protection via transport containment to guard against an accident during transport to the curation facility.
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Release due to failure of containment or of the spacecraft surface sterilisation
For there to be a risk, as opposed to a hazard, there must exist an event that would initiate an exposure of the environment to the components of the Mars sample. In principle, there are four main ways for an environmental exposure to be initiated from the accidental/deliberate release a Mars sample into the Earth’s biosphere:
• A break-up of the container during atmospheric entry (due to a design fault or sabotage),
• An unsuccessful full sterilisation of the Earth Entry Capsule, potentially having Mars particles attached to its outside surfaces,
• Damage to the vehicle due to heavy impact with the Earth,
• Escape of material during transport or from the laboratory.
In the first and (possibly) second cases, there is potential for contamination over a quite wide area (especially if the capsule breaks up at high altitude). However, the sample will be small (the quantity of unsterilised particles even smaller) and therefore deposition per unit area will be very low.
In the two latter cases, the release would be a point source. Based on failure of containment of pathogenic material in the past, it is reasonable to assume that the most likely cause of a release would be due to human error or a deliberate human act following the introduction of the material into the laboratory.
▲
* The container could rupture if the parachute fails during the landing (rupture of a sample container has already occurred during the [[Sample_return_mission#Current|sample return of the Genesis capsule]]).
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* Also human error, or management decisions could compromise the safety precautions taken for safe sample return.
====Risk mitigation for sample container ====
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This describes the issues, see the risk mitigation section for the solutions proposed for these issues.
The
The ESF report
{{bq|Unless future Mars landers and/or rovers discover living organisms on Mars and gather significant information before a Mars sample is returned, knowledge about Mars biology (if any) will have a very steep development curve with an MSR: the sample will land overnight and the scientific investigations will have no or only limited preliminary steps. This differs significantly from, for example, the incremental development of synthetic biology that becomes increasingly complex, building upon past experience and experiments.}}
▲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.<ref name=esf2012_PP-crime-etc>{{cite report |title=A Draft Test Protocol for Detecting possible biohazards in martian samples returned to Earth|publisher=NASA |year=2002 |quote="
==== Target probabilities for proposed biohazard facilities ====
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{{bq|The release of a single unsterilised particle larger than 0.05 µm is not acceptable under any circumstance<ref name=esf2010_LAWKI/>}}
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.<ref name=imars>[https://web.archive.org/web/20130124081409/http://mepag.nasa.gov/reports/iMARS_FinalReport.pdf Preliminary Planning for an International Mars Sample Return Mission] Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group, June 1, 2008</ref> 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.<ref>Jeremy Hsu [http://www.astrobio.net/exclusive/3329/keeping-mars-contained Keeping Mars Contained] Astrobiology Magazine 12/03/09</ref><ref>Beaty DW, Allen CC, Bass DS, Buxbaum KL, Campbell JK, Lindstrom DJ, Miller SL, Papanastassiou DA. [http://www.ncbi.nlm.nih.gov/pubmed/19845446?report=abstract Planning considerations for a Mars Sample Receiving Facility: summary and interpretation of three design studies.] Astrobiology. 2009 Oct;9(8):745-58. doi: 10.1089/ast.2009.0339.</ref><ref>[http://www.nap.edu/openbook.php?record_id=5563&page=31 Mars Sample Return: Issues and Recommendations](1997)] Task Group on Issues in Sample Return, National Research Council (page 31)</ref>
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.<ref name=esf2012_PP-human-factors>{{cite report |title=Mars Sample Return backward contamination - strategic advice |publisher= European Science Foundation |year=2012 |chapter=4.7 Potential verification methods"|url=
===Concerns about incubation period===
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The WHO Leprosy fact sheet<ref>[http://www.who.int/mediacentre/factsheets/fs101/en/ Leprosy Fact Sheet] World Health Organization</ref> 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 <ref name=esf2012_PP-precautionary>[
====Risk mitigation for incubation period====
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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.<ref name=esf2012_PP-being-prepared>{{cite report |title=Mars Sample Return backward contamination - strategic advice |publisher= European Science Foundation |year=2012 |chapter=5: "The Potential for Large-Scale Effects - 5.4 Being prepared"|url=
===Dissenting views of the ICAMSR on back contamination risks of a MSR===
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===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.<ref name=esf2010_PP_PP>[
in the context of MSR) - February 23, 2010</ref> This study found that the ones that were most relevant are:
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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.
{{bq|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).<ref name=esf2010_RALOS>[
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.
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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.<ref name=esf2012_PP-advanntages>[
To quote from the ESF report
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