Planetary Protection and Mars Sample Return

Mars sample return (MSR) mission planning requires a high level of planetary protection in order to break the chain of contact between Mars and the terrestrial biosphere. As a focus of MSR is the search for life, it is also imperative that a minimal amount of terrestrial contamination is taken to Mars on the mission. For these reasons, spacecraft cleaning of up to Viking levels will be needed, adding to the cost and complexity of the mission. Experience gained in Mars missions in the USA and Europe including and after Viking will be used. New technologies such as sample sealing in Mars orbit are also required. The recent identification of special regions on Mars where liquid water may have been present within the recent geological past has led to a revision of planetary protection constraints for missions such as MSR which might wish to visit them. Approximately 500g (five to eight samples) are envisaged in the first MSR within the 2020s. This requires a sample receiving facility to assess the threat to the terrestrial biosphere prior to analyses of the samples by the wider scientific community. This will be operated at biohazard level 4 — the highest level. Long-term curation of returned samples has planetary protection constraints but also challenges in maintaining the pristine nature of the samples as far as possible as they are moved from the oxidizing, reactive Mars surface to Earth.