Planetary Protection Considerations For Dragonfly At Titan

[Phil. Trans. R. Soc. A] Titan is an object of great interest in studying the chemical origins of life, but it is intensely cold and cannot support ‘life as we know it’: it is therefore designated a Planetary Protection Category II* target.

Titan is thought to have an internal water ocean, but it is isolated beneath an approximately 100 km thick ice crust. Herein, the particulars of the Dragonfly rotorcraft lander mission and the Titan environment are reviewed, demonstrating that inoculation of the ocean with viable terrestrial biota by the mission is a very low-probability event (much less than 10-4), thereby consistent with a mission designation of Category II. This article is part of the theme issue ‘Planetary Protection for sustainable space exploration’.

Dragonfly interplanetary trajectory as defined at mission design and navigation subsystem critical design review. Future design work may refine dates and values, but the PP implications are unlikely to change significantly from the analyses presented here. — Phil. Trans. R. Soc. A

Dragonfly [1–4] is the fourth mission in NASA’s New Frontiers programme. A rotorcraft lander will visit multiple sites on Saturn’s moon Titan to study prebiotic chemical processes and document the habitability of a carbon-rich ocean world in the outer Solar System, where the key ingredients for life have been available on the surface. Further details are given in §4.

One step in the implementation of a planetary mission is the assignment of a planetary protection (PP) category to ensure compliance with national policy and international agreements.

Specifically, NASA mission requirements, documented in NPR 8715.24 (‘Planetary Protection Provisions for Robotic Extraterrestrial Missions’, 24 September 2021) and NASA-STD-8719.27 (‘Implementing Planetary Protection Requirements for Space Flight’, 30 August 2022), require the demonstration that the current implementation of the Dragonfly mission to Titan would have a probability of less than 10–4 of a biological inoculation event into a potentially habitable extraterrestrial environment.

The present paper provides an analysis supporting this position. We first review the PP framework and the aspects of the Titan environment that bear on habitability. We then discuss the Dragonfly mission and the probability of various end states of the mission hardware elements, the thermodynamic conditions associated with them and any terrestrial biota on them. Finally, we discuss transport processes that could move material from hardware sites to elsewhere on Titan.

Hardware end states and estimated subsequent disposition (assuming successful delivery to the Saturnian system). For details on probability rationales, see table 2 and appendix C. — Phil. Trans. R. Soc. A

• Planetary protection considerations for Dragonfly at Titan, Phil. Trans. R. Soc. A via PubMed
• Planetary protection considerations for Dragonfly at Titan, Phil. Trans. R. Soc. A (open access)

Astrobiology,