LIFE: Life Investigation For EnceladusA Sample Return Mission Concept in Search for Evidence of Life

Tsou, P.; Brownlee, D. E.; McKay, Christopher P.; Anbar, Ariel D.; Yano, Hajime; Altwegg, Kathrin; Beegle, L. W.; Dissly, R.; Strange, Nathan; Kanik, I.

doi:10.1089/ast.2011.0813

Cited by 58 publications

(57 citation statements)

References 40 publications

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“…An increase in the reliability of the analysis model is required; this can be achieved through comparison and validation with experiments (e.g., in an expansion tube or an arc-heated wind tunnel). 7 3.68 Table 6 Grid sensitivity for the HVRC without a rigid flare between present and fine grids Present Fine Error, % Number of grids 150 × 202 250 × 395 --Heat flux, W∕m 2 1.86 × 10 7 1.98 × 10 7 6.34 Table 7 Grid sensitivity for the HVRC with a rigid flare between present and fine grids Present Fine Error, % Number of grids 100 × 362 200 × 703 --Heat flux, W∕m 2 9.19 × 10 6 9.42 × 10 6 2.41 a) HVRC without the rigid flare at an altitude of 58 km b) HVRC with the rigid flare at an altitude of 64 km Fig. 19 Comparison of translational and electron temperatures for HVRCs using present and fine grids as grid sensitivity.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, a new mission for Jupiter Trojan-asteroid exploration with a solar sail was proposed by JAXA [5,6]. Moreover, sample-return missions from outer planets and their moons in the solar system have been proposed [7]. Johnston et al [8] numerically investigated the aerodynamicheating environment around a reentry vehicle with a velocity of 16-22 km∕s in the Earth reentry phase.…”

Section: Introductionmentioning

confidence: 99%

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Aerodynamic-Heating Analysis of Sample-Return Capsule in Future Trojan-Asteroid Exploration

Takahashi

Yamada

2018

Journal of Thermophysics and Heat Transfer

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In sample-return missions, the reentry velocity of a sample-return capsule is expected to be approximately 15 km∕s; however, the reentry velocity of the Hayabusa sample-return capsule was 11.8 km∕s. Strong aerodynamic heating caused by a high velocity can damage the capsule during reentry. To overcome this, two designs of highvelocity reentry capsules were proposed. In one design, a rigid flare was attached to decrease the ballistic coefficient by increasing the front projected area. In the other design, the conventional Hayabusa sample-return capsule was used with no modifications. In this study, the aerodynamic heating of the high-velocity reentry capsules and the Hayabusa sample-return capsule was analyzed using numerical simulations. Plasma flow in the shock layer at the front of the capsules and expansion flow in the wake region around the capsules were investigated. The profiles of convective and radiative heat fluxes on the surfaces of these capsules were predicted. The heat fluxes at the stagnation points predicted by the present numerical simulation were in good agreement with that of the empirical models. At the strongest aerodynamic-heating altitude, the total heat fluxes at the rear of the high-velocity reentry capsules and the Hayabusa sample-return capsule were approximately 2% of those in front of the capsules. Nomenclature A = area, m 2 a = model parameter B = blackbody function, W∕m 3 B C = ballistic coefficient C = mass fraction C d = drag coefficient D = effective diffusion coefficient, m 2 ∕s f = function h = enthalpy, J∕kg I = radiation intensity, W∕m 3 Kn GLL = gradient-length-local Knudsen number k = Boltzmann constant, J∕K M = molar mass, kg∕mol m = mass, kg N A = Avogadro constant, mol −1 n = normal direction coordinate, m q = heat flux, W∕m 2 R N = nose radius, m s = one-dimensional coordinate, m T = temperature, K u, V = velocity, m∕s γ = catalytic coefficient θ = angle, rad κ = absorption coefficient, m −1 λ = mean free path, m ρ = density, kg∕m 3 Ω = solid angle, sr Subscripts ele, e = electron i = chemical species rot, R = rotation stag = stagnation trs, T = translation vib, V = vibration w = wall λ = wavelength ∞ = freestream Superscripts conv = convection rad = radiation

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aerodynamic-Heating Analysis of Sample-Return Capsule in Future Trojan-Asteroid Exploration

Takahashi

Yamada

2018

Journal of Thermophysics and Heat Transfer

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“…This is an important issue to consider as we move forward in assessing the habitability of Enceladus (Shapiro & Schulze-Makuch, 2009;McKay et al, 2014). Ultimately, empirical observation will settle the life question, as the plume provides a very convenient means of searching for molecular and isotopic evidence of life (e.g., methane, acetate; McKay et al, 2008;Postberg et al, 2008;Waite et al, 2009), and possibly even frozen organisms (Tsou et al, 2012). Whatever the outcome, further exploration of Enceladus is likely to transform our understanding of the biological potential of icy worlds in the outer Solar System, and provide a more informed perspective on our place in a possible living Universe.…”

Section: Metabolic Strategies Of Putative Lifementioning

confidence: 99%

The pH of Enceladus’ ocean

Glein

Baross

Waite

2015

Geochimica et Cosmochimica Acta

234

204

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Saturn's icy moon, Enceladus, is a geologically active waterworld. The prevailing paradigm is that there is a subsurface ocean that erupts to the surface, which leads to the formation of a plume of vapor and ice above the south pole. The chemical composition of the ocean is just beginning to be understood, but is of profound geochemical and astrobiological interest. Here, we address the most fundamental question about the ocean's chemistry by determining its pH, using a thermodynamic model of carbonate speciation. Observational data from the Cassini spacecraft are used to obtain a chemical model of ocean water on Enceladus, the first such model for another planet/moon that is based on empirical evidence. The abundance of CO2 in the plume gas, as measured by the Ion and Neutral Mass Spectrometer onboard Cassini, is essential to elucidating the pH. The geochemical model indicates that Enceladus' ocean is a Na-Cl-CO3 solution with an alkaline pH of ~11-12. The dominance of aqueous NaCl is a geochemical feature that Enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean. The high pH implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations in ocean water owing to buffering by clays and carbonates on the ocean floor. In addition, carboxyl groups in dissolved organic species (such as possible biomolecules) would be negatively charged, whereas amino groups would exist predominately in the neutral form. Knowledge of the pH dramatically improves our understanding of geochemical processes in Enceladus' ocean. In particular, the high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models, although degassing of CO2 from the ocean may also play a 3 role depending on the efficiency of mixing processes in the ocean. Serpentinization inevitably leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus' plume.Serpentinization and H2 generation should have occurred on Enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if Enceladus' rocky core has been completely altered by past hydrothermal activity. The presence of native H2 in the plume would provide strong evidence for contemporary aqueous alteration. The high pH also suggests that the delivery of oxidants from the surface to the ocean has been sporadic, and the rocky core did not experience partial melting and igneous differentiation. On the other hand, the deduced pH is completely compatible with life as we know it; indeed, life on Earth may have begun under similar conditions, and terrestrial serpentinites support thriving microbial communities that are centered on H2 that is provided by water-rock reactions. T...

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“…The type 2 mission is similar to another sample return mission for Enceladus Tk_9 (LIFE: Life Investigating For Enceladus) independently proposed by others 21) . Table 1 summarizes the comparison of these three types of mission to Enceladus.…”

Section: Trajectorymentioning

confidence: 73%

Exploration of Enceladus^|^apos; Water-Rich Plumes toward Understanding of Chemistry and Biology of the Interior Ocean

Sekine

Takano

Yano

et al. 2014

AEROSPACE TECHNOLOGY JAPAN

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Enceladus is the only icy satellite known to exhibits on-going geological activity of water-rich plumes derived from the interior ocean. Here, we propose a sample return and in-situ measurement mission for Enceladus' plume materials. Depending on the cost, mission duration, and propulsion system, we propose three types of missions to Enceladus; type 1: free-return trajectory, type 2: trajectory orbiting Saturn, and type 3: trajectory orbiting Enceladus. Type 2 and 3 are preferable to type 1 in order to achieve lower encountering velocity to the plumes (> 4 km/s and 0.2 km/s for type 2 and 3, respectively) and, thus, to collect multiple and intact samples. High resolution mass spectroscopy of the gas components will provide essential information to understand the physical and chemical conditions of both the interior ocean and the solar nebula. Furthermore, detailed onboard and onshore analyses of returned samples could provide geochemical, preboplogical, and, potentially, biological context in the interior ocean of Enceladus.

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LIFE: Life Investigation For EnceladusA Sample Return Mission Concept in Search for Evidence of Life

Cited by 58 publications

References 40 publications

Aerodynamic-Heating Analysis of Sample-Return Capsule in Future Trojan-Asteroid Exploration

Aerodynamic-Heating Analysis of Sample-Return Capsule in Future Trojan-Asteroid Exploration

The pH of Enceladus’ ocean

Exploration of Enceladus^|^apos; Water-Rich Plumes toward Understanding of Chemistry and Biology of the Interior Ocean

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