Planetary protection for a Mars sample return: Difference between revisions
Planetary protection for a Mars sample return (edit)
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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}}
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{{bq|Release due to failure of containment or of the spacecraft surface sterilisation▼
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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.
• A break-up of the container during atmospheric▼
• Damage to the vehicle due to heavy impact with▼
• Escape of material during transport or from the▼
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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.
laboratory.}}</ref> considers several possible failure modes with the sample container.▼
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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