A mathematical model for assessing the probability of contaminating Europa

DiNicola, Michael; McCoy, Kelli; Everline, Chester J.; Reinholtz, Kirk; Post, Ethan

doi:10.1109/aero.2018.8396517

Cited by 7 publications

(4 citation statements)

References 3 publications

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“…Rather than treating all microbial species as potential contaminants of extraterrestrial ocean worlds, it might be possible to target contamination controls on just those microbes that are found in analog Earth environments that are most like the landing sites on icy ocean worlds, and to survey spacecraft assembly rooms for those organisms (Shtarkman et al, 2013;Abreu et al, 2016). In this way, information about the abundances of specific microbes with known environmental tolerances could increase our ability to implement a probabilistic approach to planetary protection for missions to the outer planets and their icy moons (DiNicola et al, 2018).…”

Section: How Can Work At Analog Environments Inform Planetary Protect...mentioning

confidence: 99%

Research in Analog Environments to Enable Studies of Ocean Worlds

Arrigo¹

2022

Oceanog

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Analog environments on Earth enable scientists to answer research questions about extraterrestrial ocean worlds that would be otherwise inaccessible. Because of their relative ease of sampling and close proximity to research facilities, utilization of analog environments allows scientists to undertake many investigations for the cost of a single planetary mission. In addition to direct in situ sampling, modeling approaches can be useful as can cost-effective tools both for determining whether a moon or planet is a suitable Earth analog and for designing strategies to sample extraterrestrial analog environments. Reconfigured Earth system models can help determine if conditions on other ocean worlds are suitable to support life. Finally, space exploration has made the protection of Earth’s environment and other solar system bodies from harmful contamination a high priority at both the national and international levels. Because NASA’s planetary exploration priorities emphasize robotic exploration, the US National Academies recently recommended that studies, workshops, and brainstorming sessions organized by NASA and other space agencies need to include a sufficiently broad range of microbiologists to ensure planetary protection. This will require the development and implementation of mechanisms for creating partnerships between Earth scientists and planetary scientists to test planetary protection solutions at field analog sites.

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Section: How Can Work At Analog Environments Inform Planetary Protect...mentioning

confidence: 99%

Research in Analog Environments to Enable Studies of Ocean Worlds

Arrigo¹

2022

Oceanog

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“…Denote by E 1 (u) the event that an offnominal event leading to contact with the ocean world occurs as a result of a failure at time u as in (2a), and denote its probability density function by f 1 (u). The probability of each of these events can be assessed for a given mission by way of reliability analysis and assessment of the mission design (DiNicola et al 2018;McCoy et al 2020). Since these events are mutually exclusive, the probability that some off-nominal event leading to contact with the ocean world occurs over the course of the mission is…”

Section: Ormentioning

confidence: 99%

“…1 This study describes in detail a critical component of the planetary protection strategy for the Europa Clipper mission, which is planned to launch in 2024 and make several dozen flybys of Europa (Howell & Pappalardo 2020). To conservatively demonstrate compliance with planetary protection requirements (DiNicola et al 2018;McCoy et al 2020), Europa Clipper utilized this notion of geologic resurfacing.…”

Section: Introductionmentioning

confidence: 99%

Resurfacing: An Approach to Planetary Protection for Geologically Active Ocean Worlds

DiNicola¹,

Howell²,

McCoy³

et al. 2022

Planet. Sci. J.

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The putative and potential ocean worlds of our solar system span the asteroid belt to the Kuiper Belt, containing within their icy shells past or present global saltwater oceans. Among these worlds, those bearing signs of present-day geologic activity are key targets in the search for past or extant life in the solar system. As the icy surfaces of these bodies are modified by geologic processes, landforms are erased and replaced through what is called “resurfacing.” To avoid contaminating sites for robotic spacecraft exploration, planetary protection requirements obligate missions to these ocean worlds to demonstrate a less than 10−4 probability of introducing a viable terrestrial microorganism into a liquid water body. To constrain the probability of subsurface contamination, we investigate the interaction with geologic resurfacing on an active ocean world. Through the example of Europa, we show how the surface age can be used to constrain the resurfacing rate, a critical parameter to estimate the probability that nonsterile spacecraft material present on the surface is geologically incorporated into the subsurface, and extend this example to mission scenarios at Ganymede and Enceladus. This approach was critical to demonstrating compliance with planetary protection requirements for the Europa Clipper mission, reducing its probability of contamination by two to five orders of magnitude. We also show how a Europa lander mission might be brought close to complying with planetary protection requirements, that a Ganymede impactor could easily comply, and that the situation of Enceladus, while more complex, can greatly benefit from this approach.

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“…In order to protect the scienti c integrity of both mission architectures, planetary protection protocols (PP) have been (Perseverance and EC spacecraft; e.g., [12,13,14,15] and will be developed to (i) minimize prelaunch bioburdens on critical subsystems that will directly handle samples, (ii) sterilize and place behind biobarriers criticality-1 subsystems that must be free of terrestrial contamination prior to deployment on surface terrains, (iii) streamline collection and caching activities to prevent recontamination of presterilized components, (iv) select unique materials for speci c surfaces to compliment mitigation of recontamination, and (v) develop quantitative models to predict the inactivation of adhered bioburdens during interplanetary ight. Regarding the latter PP component, three quantitative models for microbial survival in interplanetary space have been developed [16,17,18].…”

Section: Introductionmentioning

confidence: 99%

Synergistic Interactions among Vacuum, Solar Heating, and UV Irradiation Enhance the Lethality of Interplanetary Space

Schuerger

2023

Preprint

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A Planetary Atmospheric Chamber (PAC) was used to create simulations of interplanetary conditions to test spore survival of three Bacillus spp. exposed to interacting conditions of high-vacuum (VAC), simulated solar heating (HEAT), and simulated solar ultraviolet illumination (UV). Synergism was observed among the experimental factors against all three Bacillus spp. tested that suggests increased lethality of HEAT and UV when concomitantly exposed to VAC. The most aggressive biocidal effects were observed for assays with VAC + HEAT + UV conditions run simultaneously over short time-steps. Results were used to predict the accumulation of extremely rapid Sterility Assurance Levels (SALs; def., ‒12 logs of bioburden reduction) measured in a few 10s of min for interplanetary spacecraft. Furthermore, results were extrapolated to predict that approx. 1 x 104 SAL exposures might be accumulated for external surfaces on the Europa Clipper spacecraft during a 3.5 year residence time between Venus (0.7 AU) and Mars (1.5 AU) during a series of Venus-Earth-Earth gravity assists (VEEGA trajectory) to Jovian space. The results are applicable to external spacecraft surfaces exposed to direct solar illumination during transits though the inner Solar System. [Submitted to Scientific Reports for peer review on 08-12-23.]

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A mathematical model for assessing the probability of contaminating Europa

Cited by 7 publications

References 3 publications

Research in Analog Environments to Enable Studies of Ocean Worlds

Research in Analog Environments to Enable Studies of Ocean Worlds

Resurfacing: An Approach to Planetary Protection for Geologically Active Ocean Worlds

Synergistic Interactions among Vacuum, Solar Heating, and UV Irradiation Enhance the Lethality of Interplanetary Space

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