The COSPAR planetary protection policy for missions to Icy Worlds: A review of history, current scientific knowledge, and future directions
Open accessAbstract
Recent discoveries related to the habitability and astrobiological relevance of the outer Solar System have expanded our understanding of where and how life may have originated. As a result, the Icy Worlds of the outer Solar System have become among the highest priority targets for future spacecraft missions dedicated to astrobiology-focused and/or direct life detection objectives. This, in turn, has led to a renewed interest in planetary protection concerns and policies for the exploration of these worlds and has been a topic of discussion within the COSPAR (Committee on Space Research) Panel on Planetary Protection. This paper summarizes the results of those discussions, reviewing the current knowledge and the history of planetary protection considerations for Icy Worlds as well as suggesting ways forward. Based on those discussions, we therefore suggest to 1) Establish a new definition for Icy Worlds for Planetary Protection that captures the outer Solar System moons and dwarf planets like Pluto, but excludes more primitive bodies such as comets, centaurs, and asteroids: Icy Worlds in our Solar System are defined as all bodies with an outermost layer that is believed to be greater than 50% water ice by volume and have enough mass to assume a nearly round shape. 2) Establish indices for the lower limits of Earth life with regards to water activity (LLAw) and temperature (LLT) and apply them into all areas of the COSPAR Planetary Protection Policy. These values are currently set at 0.5 and -28°C and were originally established for defining Mars Special Regions; 3) Establish LLT as a parameter to assign categorization for Icy Worlds missions. The suggested categorization will have a 1000-year period of biological exploration, to be applied to all Icy Worlds and not just Europa and Enceladus as is currently the case. 4) Have all missions consider the possibility of impact. Transient thermal anomalies caused by impact would be acceptable so long as there is less than 10−4 probability of a single microbe reaching deeper environments where temperature is >LLT in the period of biological exploration. 5) Restructure or remove Category II* from the policy as it becomes largely redundant with this new approach, 6) Establish that any sample return from an Icy World should be Category V restricted Earth return.
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Many other bodies have been confirmed to be rich in water ice resources, including the Jovian satellites Europa, Ganymede, and Callisto, as well as the Saturnian satellites Enceladus and Titan.
“Many other bodies have also been confirmed to be rich in water ice resources, including the Jovian satellites Europa, Ganymede, and Callisto, as well as the Saturnian satellites Enceladus and Titan. 88”
From Energy system and resource utilization in space: A state-of-the-art review (2024) · cites this paper as [88]
Section 3, “Icy world definition and background,” lists Europa, Ganymede, Callisto, Enceladus, and Titan as Icy Worlds with icy crusts. Table 1 refers to a greater-than-50% water-ice criterion for an Icy World. These passages support describing the moons as water-ice-rich, but do not establish confirmed quantities of water ice available as resources. (LLM, conf=0.82)
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References 88 · Cited by 11
Research works printed but not linked: 18
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- Authors
- Doran, P. T., Hayes, A., Grasset, O., Coustenis, A., Prieto-Ballesteros, O., Hedman, N., Al Shehhi, O., Ammannito, E., Fujimoto, M., Groen, F., Moores, J. E., Mustin, C., Olsson-Francis, K., Peng, J., Praveenkumar, K., Rettberg, P., Sinibaldi, S., Ilyin, V., Raulin, F., Suzuki, Y., Xu, K., Whyte, L. G., Zaitsev, M., Buffo, J., Kminek, G., & Schmidt, B.
- Affiliations
- Louisiana State University (US)
- Cornell University (US)
- Nantes Université (FR)
- Centre National de la Recherche Scientifique (FR)
- United Nations Office for Outer Space Affairs (AT)
- Agenzia Spaziale Italiana (IT)
- Japan Aerospace Exploration Agency (JP)
- National Aeronautics and Space Administration (US)
- York University (CA)
- Centre National d'Études Spatiales (FR)
- China National Space Administration (CN)
- Indian Space Research Organisation (IN)
- Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (DE)
- European Space Agency (FR)
- Russian Academy of Sciences (RU)
- The University of Tokyo (JP)
- China Academy of Space Technology (CN)
- McGill University (CA)
- Dartmouth College (US)
- Corresponding author
- Doran, P.T.
- ORCID
- Venue
- Life Sciences in Space Research
- Publisher
- Elsevier BV
- Published
- 2024-05
- Volume
- 41
- Pages
- 86-99
- ISSN
- 2214-5524 (ISSN-L)
- OpenAlex
- W4391656891
- Cited by
- 11
- References
- 88
- Citations by year
- 2026: 6 · 2025: 4 · 2024: 1
- FWCI
- 2.07
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Life Sciences in Space Research (publishedVersion, other-oa)
- PubMed (publishedVersion)
- elib (German Aerospace Center) (acceptedVersion)
- Open Research Online (The Open University) (acceptedVersion)
- HAL (submittedVersion, cc-by)
- Civil War Book Review (submittedVersion)
- Funders
- Louisiana State University
- Centre National d’Etudes Spatiales
- Agencia Estatal de Investigación (AEI//10.13039/501100011033/, 501100011033, 10.13039/501100011033, 13039, .13039/501100011033, 10.13039, PID2019)
- Research England
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Space Science and Extraterrestrial Life
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Planetary Science and Exploration
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
- Keywords
- planetary protection, icy worlds, Europa, Enceladus, Pluto, astrobiology, habitability, water activity, impact risk, sample return, microbial contamination
- MeSH terms
- Extraterrestrial Environment, Space Flight, Solar System, Planets, Spacecraft, Exobiology, History, 20th Century
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