With the recognition of an increasing potential for discovery of extraterrestrial life, a diverse set of researchers have noted a need to examine the foundational ethical principles that should frame our collective space activities as we explore outer space. A COSPAR Workshop on Ethical Considerations for Planetary Protection in Space Exploration was convened at Princeton University on June 8-10, 2010, to examine whether planetary protection measures and practices should be extended to protect planetary environments within an ethical framework that goes beyond "science protection" per se. The workshop had been in development prior to a 2006 NRC report on preventing the forward contamination of Mars, although it responded directly to one of the recommendations of that report and to several peer-reviewed papers as well. The workshop focused on the implications and responsibilities engendered when exploring outer space while avoiding harmful impacts on planetary bodies. Over 3 days, workshop participants developed a set of recommendations addressing the need for a revised policy framework to address "harmful contamination" beyond biological contamination, noting that it is important to maintain the current COSPAR planetary protection policy for scientific exploration and activities. The attendees agreed that there is need for further study of the ethical considerations used on Earth and the examination of management options and governmental mechanisms useful for establishing an environmental stewardship framework that incorporates both scientific input and enforcement. Scientists need to undertake public dialogue to communicate widely about these future policy deliberations and to ensure public involvement in decision making. A number of incremental steps have been taken since the workshop to implement some of these recommendations.

ed policies to be drafted (Tennen, 2004 ). Planetary protection is an international endeavor to preserve the capability to study planets and moons of astrobiological interest as they exist in their natural state. The contamination with Earth organisms and organic molecules that could be misinterpreted as biosignatures would compromise life detection missions (forward contamination). Moreover, Earth's biosphere needs to be protected from potential harmful extraterrestrial matter carried by a spacecraft returning from an interplanetary mission (backward contamination). Maintaining and promulgating the COSPAR planetary protection policy and the associated requirements at an international level are under the mandate of COSPAR. In the past, COSPAR's Planetary Protection Policy was mainly focused on planets close to the Sun, in particular Mars, and on their protection from biological contamination. Although the requirements for Mars and the guidelines as to how these may be implemented are based on decades of experience, the necessary measures to study chemical evolution and the potential origin of life in the outer bodies of the Solar System, particularly at Europa and Enceladus, are less developed. Current guidelines are based on conservative estimates of poorly known parameters (Kminek et al. , 2017 ) and given the increased number of planned missions to ever more distant planetary bodies, an updated policy and easier to implement requirements are needed. To date, the COSPAR Planetary Protection Policy has identified five categories of planetary protection requirements depending on the type of mission, the target body, and the types of scientific investigations involved. For category I missions, no planetary protection measures are necessary, but for category II to V missions, the planetary protection requirements become increasingly stringent depending on the scientific focus of a particular mission and on the astrobiological relevance of their individual mission targ

The search for both extant and extinct life within our Solar System and beyond has been a primary motivation for space exploration since its inception. Mars has long been a focal point for exploration, and it continues to be, while the moons of the gas giants, Jupiter and Saturn, are increasingly seen as possible habitats. To ensure safe and sustainable scientific exploration of these bodies, the COSPAR Policy on Planetary Protection aims at ensuring adherence to the 1967 Outer Space Treaty. Although not legally binding, the guidelines set forth by the Policy are globally supported, with implementation instructions provided. The primary goal of the Committee on Space Research (COSPAR) Panel on Planetary Protection is to safeguard against the harmful effects of both forward and backward contamination. It focuses on the biological exchange that may occur during Solar System exploration, which could negatively affect the study of chemical evolution as well as the origin of life. The Policy is regularly reviewed and revised to incorporate the latest scientific discoveries, alongside the rapidly advancing requirements of space exploration. The Panel's work addresses the specific needs of each space mission, while ensuring the application of relevant expertise to promote the sustainable exploration of the Solar System. This article is part of the theme issue 'Planetary Protection for sustainable space exploration'.