Low Cost Enceladus Sample Return Mission Concept P. Tsou 1, D. E. Brownlee 2, C. P. McKay 3, A. Anbar 4, H. Yano 5, Nathan Strange 7, Richard Dissly 6, and I. Kanik 7 1 Sample Exploration Systems (Peter.Tsou@gmail.com) 2 University of Washington 3 Ames Research Center 4 Arizona State University LCPM-10 Pasadena, CA June 18-20, 2013 5 Japan Aerospace Exploration Agency 6 Ball Aerospace & Technologies Corp. 7 Jet Propulsion Laboratory, California Institute of Technology Image: NASA/JPL-Caltech/SSI
Enceladus Saturnian Moon with water vapor geysers erupting from Tiger Stripes on its South pole Plumes are very likely fed by a liquid subsurface saltwater ocean with a significant and persistent heat source Cassini INMS measurements of the plume have found simple organic compounds 2 Image: NASA/JPL-Caltech/SSI
The Plumes Cassini has provided strong evidence that Enceladus has an ocean with an energy source, nutrients, and organic molecules. From everything we know, Enceladus should be habitable. We want to know if it is inhabited, and if not, why not. Either way, sample return is essential. Lucky for us, Enceladus is already ejecting samples into space. We just have to go get them. 3 Image: NASA/JPL-Caltech/SSI
The value of a sample Determining the presence or absence of life requires multiple analyses that are too complex to fly, and the optimal analytical sequence to follow depends on what you learn at each step of the sequence The exact same logic holds for studying any potential pre-biotic chemistry of Enceladus Regardless of any biological content of the sample, this would be the first sample from the Outer Solar System and would provide invaluable clues to the origin and evolution of the Solar System 4
Aerogel Sample Collection The Stardust heritage aerogel collection mechanism could be augmented for Enceladus sample return by: Reducing the initial shock energy by reducing aerogel entry density (e.g. with Japanese Tanpopo aerogel) Carrying a volatiles trapping and sealing deposition collector to seal the samples at capture (e.g. the metal sealing technology that will be employed on Hayabusa-2) Strong particle 5 Weak particle
Spacecraft Concept Graphic: Raul Polit Casillas Spacecraft 3 m HGA used to shield main body of spacecraft from plume particles ASRG power source 800 kg dry mass, 3 km/s ΔV Hibernation during interplanetary cruise Dual-use science and engineering instruments such as a navigation camera and radiometric tracking Design also compatible with in situ instruments such as dust counter and mass spectrometer View From Ram Direction 6 Plume Particles
Mission Description 15 year mission, launching in early 2020s 8.5 years to Saturn (Venus & Earth flybys) multiple trajectory options exist 2 years in Saturn orbit multiple Enceladus flybys sample collection from multiple jets possible 4.5 year Earth return trajectory Earth entry capsule for sample return Sample curation and analysis 7 3. Earth Flyby Mar. 2023 Example 2021 VEEGA trajectory to Saturn 4. Earth Flyby June 2026 1. Launch Nov. 2021 2. Venus Flyby Apr. 2022 5. Saturn Arrival May 2030
Saturn Orbit Phase Titan gravity-assists used to set up favorable geometry for Enceladus sample collection 8 Trajectory: Brent Buffington
Planetary Protection Developing a method to avoid inadvertent backward contamination is a huge challenge Our current strategy is to tune the sample impact velocity such that large molecules would survive, but structures such as bacteria or viruses would not Additional layers of safety would be achieved through trajectory biasing and entry system reliability Non-destructive return of extraterrestrial life forms would likely require multi-mission investments to develop new planetary protection technologies 9
Low Cost Approach Sample return is the most cost effective means for detection or non-detection of life in the plume material Tightly focused on astrobiology and plume composition science objectives Important science such as studying the interior of Enceladus, the plume mechanism, etc. is left for other missions. Low spacecraft dry mass Low spacecraft power design New spacecraft design, but built from existing components and subsystem designs Hibernation during long periods of spacecraft inactivity 10
Concluding Remarks Detection of life from Enceladus would change the world Conclusive non-detection of life in the Enceladus ocean would be almost as significant The best way to get either of the above results in a single mission requires a sample return Elements critical to making this possible include: High priority in Decadal Survey RPS power systems High Performance TPS International collaboration 11