Best Practices in - PowerPoint Presentation

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Best Practices in Organic Contamination Control

Mark A. Sephton1, Susan McKenna-Lawlor2, John R. Brucato3 Earth/Science/Engineering, Imperial College London Space Technology Ireland, Ltd. Maynooth, Ireland Astrophysical Observatory Arcetri, Fierenze, Italy

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The recent shift in astrobiological exploration from Mars to the icy moons of the outer solar system necessitates reconsideration of our planetary protection protocols.  There are significant differences between Mars and the Icy Moons. The former is dry and organic matter-poor while the latter are potentially wet and organic matter-rich.  In these circumstances, contamination at Mars can be expected to comprise local events whereas contamination of subsurface oceans on Icy Moons can potentially become global. INTRODUCTIONSlide3

Based on: background studies by our team of the similarities and differences between Mars and the Icy Moons; the unique individual characteristics of these environments; and differences between their respective habitabilities Current best practices in organic contamination control developed for the exploration of Mars and the Icy Moons are presented. In the light of research and development programs presently opening up A need within the community to construct a Roadmap for planetary protection is also outlined.OUTLINESlide4

False positives are generated when a signal is detected that can be confused with signals from biological materials. On Mars, organic compounds are likely to be scarce and the major challenge is their detection. Non-biological organic compounds can originate from meteoric or cometary material or through synthesis in hydrothermal systems. These organic carbon species can thereafter be transformed via chemical processes which are not very well understood. How different are the possibilities of false positives on Mars and the Icy Moons? Slide5

The radiation environment of Mars can promote the survival of small organic compounds, but with low abundances.On Icy Moons, organic compounds are likely to be plentiful and the major challenge lies in diagnosing their source. Polymerization of simple organic compounds is favoured under Icy Moon conditions where high radiation environments may produce amino acids and their oligomers, polymers or macromolecules. On Mars, the low abundances of organic compounds can lead to false positives from terrestrial contamination. On Icy Moons, the detection of polymers and macromolecules can lead to false positives when abiopolymers are confused with biopolymers. False Positives contd.Slide6

Spacecraft that fly by or enter orbit around Mars are subject to planetary protection requirements designed to control contamination and to reduce the risk that the spacecraft, or its boosters, will impact the planet. Spacecraft are assembled in clean rooms rated at Class 100,000 or better (i.e., less than one particle in the size range 1 mm to 0.001 µm for every 100,000 cubic feet of air) and it is ensured that the probability of impact by the launch vehicle and the flyby spacecraft does not exceed 10-4and 10-2 respectively. Standard planetary protection strategies currently used for MarsSlide7

Standard planetary protection strategies contd.The lifetime of an orbiter must be such that it remains in orbit for a period in excess of 20 years from launch and the probability of impact for the next 30 years must be no higher than 0.05.If the lifetime requirements cannot be met, then the surface microbial bioburden must meet the Viking pre-sterilisation limit. Following bioassay, such spacecraft must be protected against recontamination.Slide8

Spacecraft that land on Mars but are not equipped with life-detection experiments are subject to planetary protection requirements designed to control the lander’s bioburden and to prevent accidental impact by hardware not intended to land. The total probability of any accidental impacts by any hardware other than the lander must be no more than 10-4.  Bioburden control involves assembly in a Class 100,000, or better, clean room, periodic microbiological assays, and maintenance of hardware cleanliness. Bioburden reduction to the Viking pre-sterilisation level is required. Standard planetary protection strategies for Mars Slide9

The mission team is also required to provide inventory, documentary, and archive samples of organic compounds used in the construction of the lander and associated hardware that might accidentally impact the planet.  Finally, the locations of landing sites and impact points must be determined as accurately as possible, and the condition of the hardware at each site must be estimated to assist in determining the potential spread of organic compounds.Standard planetary protection strategies for Mars contd.Slide10

The Planetary Protection Categories defined by the Committee on Space Research (COSPAR) differentiate between space missions according to their type flyby, orbiter, lander, sample return while also reflecting the degree to which the environs of a spacecraft might influence the processes of local chemical evolution and/or the origin of life. Planetary protection strategies for Icy MoonsSlide11

 COSPAR’s Panel on Planetary Protection provided an extended, but simplified, version of a procedure that had previously been recommended by the National Council for Research, namely to divide for analysis the icy bodies of the outer solar system into three groups namely:  (1) A large group of objects, including small icy bodies, which were judged to have only a ‘remote’ chance of contamination by spacecraft missions of all types.(2) A group consisting of Ganymede, Titan, Triton, Pluto/Charon and those Kuiper belt objects with diameters greater than one half that of Pluto that were also thought to pose a ‘remote’ concern for contamination, provided that the implementers of a specific spacecraft mission could demonstrate consistency with COSPAR’s 10-4 criterion.Standard planetary protection strategies for Icy Moons contd.Slide12

  (3) A group/pair consisting of Europa and Enceladus that were believed to have a ‘significant’ chance of contamination by spacecraft missions. The ‘significant’ chance of contamination referred to in (3) requires the implementation of significant measures (including bioburden reduction) during flybys, as well as for orbiter and lander missions to Europa and Enceladus, aimed overall at reducing the probability of inadvertent contamination of bodies of water beneath the surfaces of these objects to < 1 x 10-4 per mission. Standard planetary protection strategies for Icy Moons contd.Slide13

 The approach adopted by COSPAR for determining compliance with its 10-4standard for missions targeted to Europa (and Enceladus), and to a lesser extent for mission to Ganymede (including also Titan, Triton, Pluto/Charonn and large Kuiper belt objects), involves the multiplication of conservatively estimated, but as yet poorly known, parameters. Standard planetary protection strategies for Icy Moons contd. Slide14

For Europa, the following items are (at a minimum) included in the calculation.Bioburden at launch,Cruise survival for contaminating organisms,Organism survival in the radiation environment adjacent to Europa, Probability of landing on Europa,The mechanisms and timescales of transport to the subsurface of EuropaOrganism survival and proliferation before, during and after subsurface transfer.This particular approach also leaves open the possibility to include additional parameters in the calculation.

Standard planetary protection strategies for Icy Moons contd.Slide15

 The Task Group on the Forward Contamination of Europa concluded that current cleaning and sterilization techniques are satisfactory to meet the needs of future space missions to Europa. These techniques include Viking-derived procedures such as cleaning surfaces with isopropyl alcohol and/or sporicides and sterilization by dry heating, as well as more modern processes such as sterilization by hydrogen peroxide, assuming that final sterilization is accomplished via exposure of the spacecraft to Europa’s radiation environment.Existing planetary protection techniques useful for Icy MoonsSlide16

All components of the probe instrumentation must be decontaminated for chemical and biological reduction using both physical and chemical treatments, depending on the material properties and size of the component part. In brief, physical methods should include: (a) dry heat up to 250 °C, for bulky heat-resistant parts; (b) steam (121 °C) for heat and water-resistant components; (c) hermicidal UV radiation (260 nm) for all UV-resistant and un-shadowed parts. Planetary protection techniques useful for Icy Moons contd.Slide17

Chemical disinfectants include:(a) detergent alkaline mixture “Extran”; (b) alcohol mixture “Bacillol”; (c) hydrogen peroxide (5%); (d) hypochlorous acid, for stainless steel parts), (e) ozone. For each component, at least two decontamination methods should be applied.All components of the probe instrumentation must be decontaminated for chemical and biological reduction using both physical and chemical treatments depending on the material properties and size of the component part. Planetary protection techniques useful for Icy Moons contd.Slide18

Heat kills many microbes (6 hours at 125oC reduces numbers by an order of magnitude). Electronic components utilized onboard a mission to the Icy Moons should thus be suitably qualified to withstand laboratory tests aimed at reducing the overall bioburden and an approved parts list should be maintained by the agencies in this regard.Planetary protection techniques useful for Icy Moons contd.Slide19

Owing to the great distances of the Icy Moons from the Sun, nuclear power sources may be adopted. Current planetary protection rules concerning nuclear power sources on celestial bodies are unclear. It can be assumed however that there will be no desire to introduce radioactive material under the ice and strict limits are likely to be imposed on the chances of radioactive material coming in contact with the ocean present on an icy moon.It is likely that planetary protection requirements will in future require careful consideration in this regard. What new planetary protection techniques need to be developed for the Icy Moons?Slide20

The potential global connectivity of subsurface oceans mean that microbial contamination could spread across the whole moon. It has thus been recommended by the NRC that current spore-based culturing techniques used to determine the bioload on a spacecraft should be supplemented by screening tests for specific types of extremophiles, such as radiation-resistant organisms. It was in addition suggested that modern molecular methods, such as those based on the polymerase chain reaction (PCR), may prove to be more rapid and more sensitive for detecting and identifying biological contamination than NASA’s existing culturing protocols for planetary protection.What new planetary protection techniques need to be developed for Icy Moons? contd.Slide21

Traditionally, research and technology development for planetary protection purposes has focused on advancing capabilities within the framework of individual missions or on a program level.Against this background, Frick et al., 2014 pointed out the potential advantages of defining and implementing a planetary protection ROADMAP (to include increasing the level of strategic direction and facilitating compliance by advancing technologies and methods; while centralizing a more comprehensive knowledge capture and management structure).Strategic Research and Technology Development RoadmapSlide22

The time-horizon and multidisciplinary nature of current planetary research avenues can best be accommodated by developing an over-arching program that integrates capability-driven developments with mission-driven implementation efforts (Frick et al., 2014). Such a program will need additional resources beyond those currently allocated within the agencies to planetary protection activities (in terms of staff, personnel and funding streams).Roadmap Development Contd.Slide23

A strategic roadmap for planetary protection can ultimately provide a forum for strategic planning and facilities compliance, while acting as an overall knowledge management framework.It is foreseen overall that, if adequately supported, it would help to enable the next phase of solar system exploration, including: the search for life; sample return missions and human exploration while, in addition, safeguarding scientific results and the Earth’s biosphere.Roadmap Development Contd.Slide24