On the Habitability and Future Exploration of Ocean Worlds

Life cannot emerge on a planet or moon without the appropriate electrochemical disequilibria and the minerals that mediate energy-dissipative processes. Here, it is argued that four minerals, olivine ([Mg>Fe]2SiO4), bridgmanite ([Mg,Fe]SiO3), serpentine ([Mg,Fe,]2-3Si2O5[OH)]4), and pyrrhotite (Fe(1−x)S), are an essential requirement in planetary bodies to produce such disequilibria and, thereby, life. Yet only two minerals, fougerite ([Fe2+6xFe3+6(x−1)O12H2(7−3x)]2+·[(CO2−)·3H2O]2−) and mackinawite (Fe[Ni]S), are vital—comprising precipitate membranes—as initial “free energy” conductors and converters of such disequilibria, i.e., as the initiators of a CO2-reducing metabolism. The fact that wet and rocky bodies in the solar system much smaller than Earth or Venus do not reach the internal pressure (≥23 GPa) requirements in their mantles sufficient for producing bridgmanite and, therefore, are too reduced to stabilize and emit CO2—the staple of life—may explain the apparent absence or negligible concentrations of that gas on these bodies, and thereby serves as a constraint in the search for extraterrestrial life. The astrobiological challenge then is to search for worlds that (i) are large enough to generate internal pressures such as to produce bridgmanite or (ii) boast electron acceptors, including imported CO2, from extraterrestrial sources in their hydrospheres.

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“…(4) Oxidants on moons such as Europa may be generated qualitatively by relatively local high energy radiation [ 250 , 251 , 252 ];…”

Section: Caveats and Limitationsmentioning

confidence: 99%

Six ‘Must-Have’ Minerals for Life’s Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite

Russell

Ponce

2020

Life

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“…The NASA/ESA/ASI Cassini-Huygens mission (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) has done much to advance our understanding of the Saturn system in general and Titan and Enceladus in particular, and has shown these satellites of Saturn to be two favourable locations in the Solar System in our quest for a better understanding of the evolution of the Solar System and its habitable potential. Both Saturnian moons possess energy sources, liquid habitats, nutrients (organic compounds), and transport cycles of liquid moving nutrients and waste, all necessary ingredients for habitability [46,92]. Titan is the only active extraterrestrial alkanological system in the Solar System (analogous to the Earth's hydrological system), including an organically rich atmosphere, hydrocarbon lakes and seas on the surface and a liquid water subsurface ocean.…”

Section: Overviewmentioning

confidence: 99%

Exploration of Enceladus and Titan: investigating ocean worlds’ evolution and habitability in the Saturn system

et al. 2021

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We present a White Paper with a science theme concept of ocean world evolution and habitability proposed in response to ESA’s Voyage 2050 Call with a focus on Titan and Enceladus in the Saturn system. Ocean worlds in the outer Solar System that possess subsurface liquid water oceans are considered to be prime targets for extra-terrestrial life and offer windows into Solar System evolution and habitability. The Cassini-Huygens mission to the Saturn system (2004–2017) revealed Titan with its organic-rich evolving world with terrestrial features and Enceladus with its active aqueous environment to be ideal candidates to investigate ocean world evolution and habitability. Additionally, this White Paper presents a baseline for a multiple flyby mission with a focused payload as an example of how ocean world evolution and habitability in the Saturn system could be investigated building on the heritage of the Cassini-Huygens mission and complementing the recently selected NASA Dragonfly mission.

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“…The exploration of Europa presents an important target for both astrobiology and comparative oceanography, i.e., the opportunity to study liquid-water oceans as a planetary process (Hand & German 2018;Hand et al 2020). Europa's icy shell also offers the opportunity to study tectonics and geologic cycles across a range of mechanisms (e.g., Earth's cooling versus Europa's tidal dissipation) and compositions (silicate in the case of the Earth versus ice in the case of Europa;McKinnon 1998;Nimmo & Gaidos 2002;Doggett et al 2009;Kattenhorn & Hurford 2009;Kattenhorn & Prockter 2014).…”

Section: Introductionmentioning

confidence: 99%

“…If Clipper reveals that Europa is habitable, then clearly an in-situ investigation with a lander is the next step. But even if the Clipper mission were to reveal that Europa was not habitable, Europa's ice-shell geology, geophysics, and oceanography are in and of themselves worthy of in-situ investigation (National Research Council 1999, 2003bHand et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Science Goals and Mission Architecture of the Europa Lander Mission Concept

et al. 2022

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Europa is a premier target for advancing both planetary science and astrobiology, as well as for opening a new window into the burgeoning field of comparative oceanography. The potentially habitable subsurface ocean of Europa may harbor life, and the globally young and comparatively thin ice shell of Europa may contain biosignatures that are readily accessible to a surface lander. Europa’s icy shell also offers the opportunity to study tectonics and geologic cycles across a range of mechanisms and compositions. Here we detail the goals and mission architecture of the Europa Lander mission concept, as developed from 2015 through 2020. The science was developed by the 2016 Europa Lander Science Definition Team (SDT), and the mission architecture was developed by the preproject engineering team, in close collaboration with the SDT. In 2017 and 2018, the mission concept passed its mission concept review and delta-mission concept review, respectively. Since that time, the preproject has been advancing the technologies, and developing the hardware and software, needed to retire risks associated with technology, science, cost, and schedule.

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On the Habitability and Future Exploration of Ocean Worlds

Cited by 56 publications

References 139 publications

Six ‘Must-Have’ Minerals for Life’s Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite

Six ‘Must-Have’ Minerals for Life’s Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite

Exploration of Enceladus and Titan: investigating ocean worlds’ evolution and habitability in the Saturn system

Science Goals and Mission Architecture of the Europa Lander Mission Concept

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