The COSPAR planetary protection policy for missions to Icy Worlds: A review of history, current scientific knowledge, and future directions

P T Doran; A Hayes; O Grasset; A Coustenis; O Prieto-Ballesteros; N Hedman; O Al Shehhi; E Ammannito; M Fujimoto; F Groen; J E Moores; C Mustin; K Olsson-Francis; J Peng; K Praveenkumar; P Rettberg; S Sinibaldi; V Ilyin; F Raulin; Y Suzuki; K Xu; L G Whyte; M Zaitsev; J Buffo; G Kminek; B Schmidt

doi:10.1016/j.lssr.2024.02.002

The COSPAR planetary protection policy for missions to Icy Worlds: A review of history, current scientific knowledge, and future directions

Life Sci Space Res (Amst). 2024 May:41:86-99. doi: 10.1016/j.lssr.2024.02.002. Epub 2024 Feb 8.

Authors

P T Doran¹, A Hayes², O Grasset³, A Coustenis⁴, O Prieto-Ballesteros⁵, N Hedman⁶, O Al Shehhi⁷, E Ammannito⁸, M Fujimoto⁹, F Groen¹⁰, J E Moores¹¹, C Mustin¹², K Olsson-Francis¹³, J Peng¹⁴, K Praveenkumar¹⁵, P Rettberg¹⁶, S Sinibaldi¹⁷, V Ilyin¹⁸, F Raulin¹⁹, Y Suzuki²⁰, K Xu²¹, L G Whyte²², M Zaitsev²³, J Buffo²⁴, G Kminek¹⁷, B Schmidt²

Affiliations

¹ Department of Geology and Geophysics, Louisiana State, Baton Rouge, LA, USA. Electronic address: pdoran@lsu.edu.
² Cornell University, Ithaca, NY, 14853-6801, USA.
³ Nantes Université, Nantes, France.
⁴ LESIA, Paris Observatory, PSL University, CNRS, Paris University, 92195, Meudon Cedex, France.
⁵ Centro de Astrobiología (CAB), CSIC-INTA, 28850, Torrejón de Ardoz, Madrid, Spain.
⁶ Committee, Policy and Legal Affairs Section, Office for Outer Space Affairs, United Nations Office at Vienna, Austria.
⁷ UAE Space Agency, Abu Dhabi, UAE.
⁸ Italian Space Agency (ASI), Rome, Italy.
⁹ Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Kanagawa, Japan.
¹⁰ Office of Safety and Mission Assurance, NASA Headquarters, Washington, DC, 20546, USA.
¹¹ York University, Toronto, Canada.
¹² Centre National des Etudes Spatiales (CNES), France.
¹³ AstrobiologyOU, Faculty of Science, Technology, Engineering and Mathematics, The Open University, Milton Keynes, UK.
¹⁴ China National Space Administration, Beijing, China.
¹⁵ Indian Space Research Organisation, Bengaluru, India.
¹⁶ German Aerospace Center (DLR), Institute of Aerospace Medicine, Radiation Biology Department, Research Group Astrobiology, 51147, Cologne, Germany.
¹⁷ European Space Agency, ESA-ESTEC, Noordwijk, the Netherlands.
¹⁸ Institute for Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.
¹⁹ Univ Paris Est Créteil and Université Paris Cité, CNRS, LISA, F-94010, Créteil, France.
²⁰ Department of Earth and Planetary Science, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
²¹ Laboratory of Space Microbiology, Shenzhou Space Biotechnology Group, Chinese Academy of Space Technology, Beijing, China.
²² Department of Natural Resource Sciences, McGill University, Montreal, Canada.
²³ Planetary Physics Department, Space Research Inst. of Russian Acad. of Sciences, Moscow, Russia.
²⁴ Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.

PMID: 38670657
DOI: 10.1016/j.lssr.2024.02.002

Abstract

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.

Keywords: Backward contamination; Forward contamination; Icy Worlds; Planetary protection.

Publication types

Review
Historical Article

MeSH terms

Exobiology*
Extraterrestrial Environment*
History, 20th Century
Planets*
Solar System
Space Flight
Spacecraft