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

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

The Emirates Mars Mission

International audienceThe Emirates Mars Mission (EMM) was launched to Mars in the summer of 2020, and is the first interplanetary spacecraft mission undertaken by the United Arab Emirates (UAE). The mission has multiple programmatic and scientific objectives, including the return of scientifically useful information about Mars. Three science instruments on the mission's Hope Probe will make global remote sensing measurements of the Martian atmosphere from a large low-inclination orbit that will advance our understanding of atmospheric variability on daily and seasonal timescales, as well as vertical atmospheric transport and escape. The mission was conceived and developed rapidly starting in 2014, and had aggressive schedule and cost constraints that drove the design and implementation of a new spacecraft bus. A team of Emirati and American engineers worked across two continents to complete a fully functional and tested spacecraft and bring it to the launchpad in the middle of a global pandemic. EMM is being operated from the UAE and the United States (U.S.), and will make its data freely available

A New Era For Planetary Protection: The Probabilistic Approach

The primary aims of planetary protection are to ensure that: 1) scientific investigations of possible extra-terrestrial life forms, precursors, and remnants are not jeopardised during planetary space missions; 2) Earth is protected from the potential hazard posed by extra-terrestrial matter carried by spacecraft returning from an interplanetary mission. The concept of planetary protection has received increased attention over recent years due to the emergence of new spacefaring countries and the growing involvement of commercial actors. The international standards for planetary protection have been developed through consultation with the scientific community and the space agencies by the Committee on Space Research's Panel on Planetary Protection, which provides guidance for compliance with the Outer Space Treaty of 1967. To date, there are five categories of requirements, which are defined based on the mission's target, type, and scientific rationale. The categories outline the recommended measures to be applied to a mission. As the mission target increases in relevance to habitability and/or the origins of life, the stringency in hardware cleanliness requirements increases. Initial guidelines were guided by a probabilistic approach. This approach uses mathematical models to calculate the probability of the initial microbial contamination from a spacecraft contaminating a target body. Post-Viking, bioburden limits/ spore counts were introduced to the policy for target bodies like Mars, as it was concluded that Mars was less hospitable than initially believed. Yet, the probabilistic approach is still applied to Category III and IV (e.g., Europa Clipper) and Category V (e.g., Mars sample return) missions. This approach could benefit more complex missions where there is a need for a more advanced approach to planetary protection. For this to be reliable, further scientific knowledge is required, e.g., our understanding of cleanroom contaminants and the biocidal impact of the mission environment, and the mathematical models need to be constrained. Ongoing research by space agencies and the scientific community is working towards addressing these knowledge gaps. The COSPAR Panel on Planetary Protection will continue to review this approach as a plausible alternative to bioburden limits to enable the next generation of missions