What does Europa Smell Like?
Abstract
Understanding the organic and dissolved gas composition of Europa's ocean is key to assessing its habitability and searching for potential biosignatures. However, we currently know nothing about these aspects of the composition of Europa, which makes it difficult to define expectations for the upcoming Europa Clipper mission and a future Europa Lander mission. Our team has been making models of the volatile composition of the ocean and possible ocean-derived plumes. The primary purpose of these models is to assist mission planning and testing of instruments. Nevertheless, this exercise is also scientifically useful as it forces us to identify source materials and geochemical processes that could influence the composition, and attempt to constrain their effects.
A number of different scenarios are being studied, but for the sake of brevity, only the most developed one is described here. This model assumes a moderately oxidized ocean with volatiles dominated by ΣCO2 and N2, consistent with the NIMS-determined distribution of CO2 on Europa's surface (Hansen and McCord, 2008, GRL), but not requiring a more oxidized sulfate-rich ocean. We consider analogies to Earth, Enceladus, or carbonaceous chondrites to constrain the concentrations of ΣCO2, N2, and noble gases. The concentrations of CH4 and ΣNH3 are assumed to be controlled by kinetically inhibited synthesis from ΣCO2 and N2, respectively. It is envisioned that these processes would also produce minor higher hydrocarbons following a logarithmic distribution. If there are hydrothermal systems on Europa, then buffering mineral assemblages may determine the concentration of H2, which may in turn control the abundances of partially oxidized organic species, such as ethanol and acetone, via metastable equilibria. We find that Europa's putative plumes could be rich in N2, unlike at Enceladus. Also, the ratios of organic compounds in unbroken carbon-skeleton families could serve as indicators of hydrothermal conditions that establish disequilibria in the ocean, enabling possible life. Ongoing work seeks to extend the model to N-bearing and heavier organics (>100 u), as well as to more thoroughly characterize the parameter space of ocean and plume compositions.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P53B..08G
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHERE;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6221 Europa;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6282 Enceladus;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS