Planetary protection for a Mars sample return: Difference between revisions
Planetary protection for a Mars sample return (edit)
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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"|urlhttps://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|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
▲
* 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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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>[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"|
===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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