Abstract
Enceladus presents an excellent opportunity to detect organic molecules that are relevant for habitability as well as bioorganic molecules that provide evidence for extraterrestrial life because Enceladus' plume is composed of material from the subsurface ocean that has a high habitability potential and significant organic content. A primary challenge is to send instruments to Enceladus that can efficiently sample organic molecules in the plume and analyze for the most relevant molecules with the necessary detection limits. To this end, we present the scientific feasibility and engineering design of the Enceladus Organic Analyzer (EOA) that uses a microfluidic capillary electrophoresis system to provide sensitive detection of a wide range of relevant organic molecules, including amines, amino acids, and carboxylic acids, with ppm plume-detection limits (100 pM limits of detection). Importantly, the design of a capture plate that effectively gathers plume ice particles at encounter velocities from 200 m/s to 5 km/s is described, and the ice particle impact is modeled to demonstrate that material will be efficiently captured without organic decomposition. While the EOA can also operate on a landed mission, the relative technical ease of a fly-by mission to Enceladus, the possibility to nondestructively capture pristine samples from deep within the Enceladus ocean, plus the high sensitivity of the EOA instrument for molecules of bioorganic relevance for life detection argue for the inclusion of EOA on Enceladus missions. Key Words: Lab-on-a-chip—Organic biomarkers—Life detection—Planetary exploration. Astrobiology 17, 902–912.
Highlights
Enceladus is an icy moon of Saturn with surface features that range in age from old cratered terrains that formed 4.2–4.6 Ga (Porco et al, 2006; Kirchoff and Schenk, 2009) to the south polar terrain (SPT) dominated by prominent tiger stripe troughs that may be younger than 0.5 Ma (Porco et al, 2006)
We present the scientific feasibility and engineering design of the Enceladus Organic Analyzer (EOA) that uses a microfluidic capillary electrophoresis system to provide sensitive detection of a wide range of relevant organic molecules, including amines, amino acids, and carboxylic acids, with ppm plume-detection limits (100 pM limits of detection)
We have presented the concept as well as a practical design for the EOA that can gather ice particles from an Enceladus plume and sensitively analyze for organic molecules, especially organic amines and amino acids that are indicative of habitability and potentially life
Summary
Enceladus is an icy moon of Saturn with surface features that range in age from old cratered terrains that formed 4.2–4.6 Ga (Porco et al, 2006; Kirchoff and Schenk, 2009) to the south polar terrain (SPT) dominated by prominent tiger stripe troughs that may be younger than 0.5 Ma (Porco et al, 2006). In 2006, Cassini confirmed this suspicion by revealing dozens of distinct, narrow geysers erupting thousands of kilometers into space from four warm fractures in the moon’s SPT (Porco et al, 2006, 2014; Spahn et al, 2006; Postberg et al, 2011; Mitchell et al, 2015) This plume has a vapor component that is predominantly water with percent levels of CO2, N2 or CO (m/z = 28), and CH4, with trace ammonia and larger light organics such as propane (Waite et al, 2006, 2009). The sensitive, quantitative, compositional, and chiral analysis of amino acids can provide significant information about the multiple processes that have shaped Enceladus, whether they are abiotic or biotic. The purpose of this article is to present the EOA instrument concept and proof-of-principle laboratory studies, to present the detailed design and engineering development that have been done toward a flyable instrument, and to present modeling studies establishing the feasibility of successfully capturing and analyzing organic molecules from the Enceladus plume in a fly-by mission profile
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