Testing the hypothesis, 'planetary protection is expensive' from the European Space Agency perspective

Investments in planetary protection (PP) are to ensure that space hardware does not carry harmful contamination in the solar system (forward PP), or to safeguard Earth's biosphere (backward PP) from potentially harmful extraterrestrial material. The implementation of PP in projects has at times been perceived as a cost driver. Here, we examine the cost of PP in European Space Agency (ESA) missions. From an evaluation made since ESA's first deep-space exploration in 1985, we have found that for forward PP: (i) for missions to target bodies with little relevance for PP (category I-II), supplementary investments or manpower is not required; (ii) for missions orbiting bodies relevant for PP (category III-orbiters to Mars and Icy Worlds), the effort to maintain those targets pristine has been estimated to be less than 1% of total mission cost; (iii) for landing missions (category IV) to Mars, the estimated cost is up to approximately 5% of total mission cost. For backward PP, the nature of restricted Earth-returned sample endeavours (category V-r), with the potential release of unwanted material from space, requires that safety must be an essential part of the mission, so by some measure the whole mission is a PP endeavour, and not an 'additional cost' per se. This article is part of the theme issue 'Planetary Protection for sustainable space exploration'.