Recent exploration of the solar system has revealed previously unknown extraterrestrial environments on which life could conceivably survive and even thrive. Simultaneously, the understanding of the astonishing diversity of habitable environments on our own planet has increased dramatically; we are beginning to recognize the vast array of living systems able to convert nearly any energetically favorable chemistry locally available into novel forms of metabolism and respiration. Taken together, this breadth of discovery has inspired a new generation of global research designed to seek and understand extraterrestrial habitability.
As exploration begins to hone in on the differences between "prebiotic," "habitable," and "inhabited," strong practices in planetary protection will be critical to guaranteeing the quality of returned science and returning samples safely to Earth. At the same time, the desire to understand the origin and fate of organic molecules in prebiotic systems leads to the need for strong practices in contamination control to protect the integrity of sampling sites. These practices can be daunting in complexity because they dovetail with instrument and spacecraft design, as well as assembly, test, and launch procedures.
The recent era of Mars exploration has already motivated a number of recent advances in planetary protection. Microbiologists have infused modern molecular techniques in planetary protection research. We now have a body of knowledge on the microbial ecology of the spacecraft assembly facility, as well as that of extreme environments previously seen as hostile to life. Similarly, the new generation of in situ scientific instruments has led to novel contamination transport models to demonstrate low risk of contamination of scientific experiments.
This document reassesses planetary protection and organic contamination control technologies, which were evaluated in 2005, and provides updates based on new science results, technology development, and programmatic priorities. The study integrates information gathered from interviews of a number of National Aeronautics and Space Administration (NASA) and European Space Agency (ESA) scientists, systems engineers, planetary protection engineers, and consultants, as well as relevant documents, and focuses on the technologies and practices relevant to the current project mission set as presented in the 2011 Planetary Science Decadal Survey.
The Mars Exploration Program's recommendation to build on the successful "Follow the Water" campaign with a new "Seeking Signs of Life" program will likely require meeting increasingly stringent planetary protection requirements.
Missions following this new approach include the Trace Gas Orbiter (TGO) and the potential Mars Sample Return (MSR) campaign. While TGO does not require novel planetary protection technologies, the MSR missions, which would cache Mars samples for eventual return to Earth, would require new technology to meet the requirements of sample transportation, biohazard assessment, and time-critical scientific assessment of the samples under both stringent cleanliness conditions and highly reliable bio-containment. Other solar system exploration over the next two decades, including potential missions to Europa and Ganymede, Titan/Enceladus, and comet surfaces, require that planetary protection and contamination control be considered in both the design of the spacecraft and mission.
Although planetary protection and contamination control requirements are derived from different sources, they share the same general approach and many of the same analytical tools, and benefit from similar education and training programs.
One important difference, however, is that planetary protection technologies and procedures have to undergo exacting verification and validation processes in order to comply with international and NASA regulations. The approach to both fields includes contaminant reduction and assessment, recontamination prevention, modeling to support quantitative risk assessments, and development of long-term curation infrastructure. This report highlights the similarities and the need for both communities to work together. Since the last assessment in 2005, many planetary protection technologies have matured, particularly in microbial reduction and validation. There have also been significant improvements in bio-burden detection and assessment, bio-diversity studies, contaminant transport, and isolation techniques. Education and training in this field of research has also increased.
Recommendations stemming from the current assessment include the following improvements over the already impressive progress in planetary protection and contamination control technologies since 2005.
The elements of contamination control and planetary protection that are critical to mission planning, science, and hardware design must be a fundamental part of the systems engineering and must be addressed at the earliest stages of the mission to ensure proper flow-down of requirements and cost-effective mission planning. An adequate approved materials/parts list that can accommodate both contamination control and planetary protection considerations should be developed. Integrated modeling tools should be developed to aid systems engineers and designers for future work, particularly in the form of risk assessments for forward- and back-contamination. Also, planetary protection implementers should define and engage systems engineering approaches to determine traceable requirements that can be flowed down within projects early in the process. Cost estimating tools should be developed.
A streamlined approval process should be developed, as well as instruction on the newly available forward-planetary protection techniques. Plans for MSR technology development related for assured containment must be carefully coordinated with concept studies and formulation efforts.
The effect of non-uniform molecular contamination on micron and submicron particle contamination levels should be determined.
Education and Training
Solicitations for early instrument technology development should include requirements for planetary protection. Education and training should be offered to all interested proposers at a level commensurate with the proposed efforts. In some cases, proposers might be advised to take the excellent planetary protection class offered by the NASA Planetary Protection Office (PPO). In other cases, ensuring the proposer is sufficiently educated with respect to the system implications of planetary protection and contamination control may be adequate. All proposals should be required to delineate their approach to planetary protection and contamination control if applicable.
NASA should support the creation of a living document detailing experiences with contamination control and curation for previous missions, to help present and future missions avoid costly mistakes. This document could be constructed around a wiki, permitting information to be collected from the widest possible range of persons. In addition, it could be included in the NASA Lessons Learned program. The timing of this recommendation is critical since the generation of Apollo scientists and technicians is quickly disappearing.