Monitorización de la oxidación del aceite de semillas de sacha inchi (Plukenetia volubilis) suplementado con extractos de vainas de tara (Caesalpinia spinosa) mediante técnicas convencionales y MIR

This work focuses on the characterization of the oxidation of the oil from sacha inchi seeds (Plukenetia volubilis) under accelerated conditions at 60 ºC for 15 days. Five samples were monitored: three supplemented with 200 ppm of non-hydrolyzed or partially hydrolyzed (for 4 and 9 hours) extracts from tara (Caesalpinia spinosa) pods, one without antioxidant and one with 200 ppm of BHT. Several conventional tech­niques (induction time, peroxide value, conjugated dienoic acid, p-anisidine value, total unsaturated fatty acids and α-linolenic acid contents) and the MIR spectroscopy coupled with chemometric tools were used and com­pared. The results revealed that whatever the antioxidant added, the oil from sacha inchi is fairly stable over time. The results also pointed out that extracts from tara pods, mainly those partially hydrolyzed, were more efficient than BHT against oil oxidation for up to 7 days. Finally, this paper shows that MIR spectroscopy pres­ents an interesting alternative technique for the monitoring of the oxidation of the oil from sacha inchi.Este trabajo se centra en la caracterización de la oxidación de aceites de sacha inchi (Plukenetia volubilis) en condiciones aceleradas a 60 ºC durante 15 días. Se monitorean cinco muestras: tres suplementadas con 200 ppm de extractos no hidrolizados o par­cialmente hidrolizados (durante 4 y 9 horas) de vainas de tara (Caesalpinia spinosa), una sin antioxidante y otra con 200 ppm de BHT. Se utilizan y comparan varias técnicas convencionales (tiempo de inducción, índice de peróxido, ácido dienoico conjugado, índice de p-anisidina, ácidos grasos insaturados totales y contenido de ácido α-linolénico) y la espectroscopía MIR junto con herramientas quimiométricas. Los resultados revelan que, cualquiera que sea el antioxidante agregado, el aceite de sacha inchi es bastante estable a lo largo del tiempo. Los resultados también seña­lan que los extractos de las vainas de tara, principalmente aquellos parcialmente hidrolizados, son más eficientes que el BHT contra la oxidación del aceite hasta los 7 días. Finalmente, el trabajo muestra que la espectroscopía MIR se presenta como una técnica alternativa interesante para el monitoreo de la oxidación del aceite de sacha inchi

Study of molecular spin-crossover complex Fe(phen)2(NCS)2 thin films

We report on the growth by evaporation under high vacuum of high-quality thin films of Fe(phen)2(NCS)2 (phen=1,10-phenanthroline) that maintain the expected electronic structure down to a thickness of 10 nm and that exhibit a temperature-driven spin transition. We have investigated the current-voltage characteristics of a device based on such films. From the space charge-limited current regime, we deduce a mobility of 6.5x10-6 cm2/V?s that is similar to the low-range mobility measured on the widely studied tris(8-hydroxyquinoline)aluminium organic semiconductor. This work paves the way for multifunctional molecular devices based on spin-crossover complexes

Spacecraft/Rover Hybrids for the Exploration of Small Solar System Bodies

This study investigated a novel mission architecture for the systematic and affordable in-situ exploration of small Solar System bodies. Specifically, a mother spacecraft would deploy over the surface of a small body one, or several, spacecraft/rover hybrids, which are small, multi-faceted enclosed robots with internal actuation and external spikes. They would be capable of 1) long excursions (by hopping), 2) short traverses to specific locations (through a sequence of controlled tumbles), and 3) high-altitude, attitude-controlled ballistic flight (akin to spacecraft flight). Their control would rely on synergistic operations with the mother spacecraft (where most of hybrids' perception and localization functionalities would be hosted), which would make the platforms minimalistic and, in turn, the entire mission architecture affordable

Spacecraft/Rover Hybrids for the Exploration of Small Solar System Bodies

This study investigated a mission architecture that allows the systematic and affordable in-situ exploration of small solar system bodies, such as asteroids, comets, and Martian moons (Figure 1). The architecture relies on the novel concept of spacecraft/rover hybrids,which are surface mobility platforms capable of achieving large surface coverage (by attitude controlled hops, akin to spacecraft flight), fine mobility (by tumbling), and coarse instrument pointing (by changing orientation relative to the ground) in the low-gravity environments(micro-g to milli-g) of small bodies. The actuation of the hybrids relies on spinning three internal flywheels. Using a combination of torques, the three flywheel motors can produce a reaction torque in any orientation without additional moving parts. This mobility concept allows all subsystems to be packaged in one sealed enclosure and enables the platforms to be minimalistic. The hybrids would be deployed from a mother spacecraft, which would act as a communication relay to Earth and would aid the in-situ assets with tasks such as localization and navigation (Figure 1). The hybrids are expected to be more capable and affordable than wheeled or legged rovers, due to their multiple modes of mobility (both hopping and tumbling), and have simpler environmental sealing and thermal management (since all components are sealed in one enclosure, assuming non-deployable science instruments). In summary, this NIAC Phase II study has significantly increased the TRL (Technology Readiness Level) of the mobility and autonomy subsystems of spacecraft/rover hybrids, and characterized system engineering aspects in the context of a reference mission to Phobos. Future studies should focus on improving the robustness of the autonomy module and further refine system engineering aspects, in view of opportunities for technology infusion

Ceres' opposition effect observed by the Dawn framing camera

The surface reflectance of planetary regoliths may increase dramatically towards zero phase angle, a phenomenon known as the opposition effect (OE). Two physical processes that are thought to be the dominant contributors to the brightness surge are shadow hiding (SH) and coherent backscatter (CB). The occurrence of shadow hiding in planetary regoliths is self-evident, but it has proved difficult to unambiguously demonstrate CB from remote sensing observations. One prediction of CB theory is the wavelength dependence of the OE angular width. The Dawn spacecraft observed the OE on the surface of dwarf planet Ceres. We characterize the OE over the resolved surface, including the bright Cerealia Facula, and to find evidence for SH and/or CB. We analyze images of the Dawn framing camera by means of photometric modeling of the phase curve. We find that the OE of most of the investigated surface has very similar characteristics, with an enhancement factor of 1.4 and a FWHM of 3{\deg} (broad OE). A notable exception are the fresh ejecta of the Azacca crater, which display a very narrow brightness enhancement that is restricted to phase angles $< 0.5${\deg} (narrow OE); suggestively, this is in the range in which CB is thought to dominate. We do not find a wavelength dependence for the width of the broad OE, and lack the data to investigate the dependence for the narrow OE. The prediction of a wavelength-dependent CB width is rather ambiguous. The zero-phase observations allow us to determine Ceres' visible geometric albedo as $p_V = 0.094 \pm 0.005$. A comparison with other asteroids suggests that Ceres' broad OE is typical for an asteroid of its spectral type, with characteristics that are primarily linked to surface albedo. Our analysis suggests that CB may occur on the dark surface of Ceres in a highly localized fashion.Comment: Credit: Schr\"oder et al, A&A in press, 2018, reproduced with permission, \copyright ES

Tidal Response of Mars Constrained From Laboratory-Based Viscoelastic Dissipation Models and Geophysical Data

We employ laboratory-based grain-size- and temperature-sensitive rheological models to 16 describe the viscoelastic behavior of terrestrial bodies with focus on Mars. Shear modulus 17 reduction and attenuation related to viscoelastic relaxation occur as a result of diffusion- 18 and dislocation-related creep and grain-boundary processes. We consider five rheological 19 models, including extended Burgers, Andrade, Sundberg-Cooper, a power-law approxima- 20 tion, and Maxwell, and determine Martian tidal response. However, the question of which 21 model provides the most appropriate description of dissipation in planetary bodies, re- 22 mains an open issue. To examine this, crust and mantle models (density and elasticity) are 23 computed self-consistently through phase equilibrium calculations as a function of pres- 24 sure, temperature, and bulk composition, whereas core properties are based on an Fe-FeS 25 parameterisation. We assess the compatibility of the viscoelastic models by inverting the 26 available geophysical data for Mars (tidal response and mean density and moment of in- 27 ertia) for temperature, elastic, and attenuation structure. Our results show that although 28 all viscoelastic models are consistent with data, their predictions for the tidal response at 29 other periods and harmonic degrees are distinct. The results also show that Maxwell is 30 only capable of fitting data for unrealistically low viscosities. Our approach can be used 31 quantitatively to distinguish between the viscoelastic models from seismic and/or tidal ob- 32 servations that will allow for improved constraints on interior structure (e.g., with InSight). 33 Finally, the methodology presented here is generally formulated and applicable to other so- 34 lar and extra-solar system bodies where the study of tidal dissipation presents an important 35 means for determining interior structure

Dawn arrives at Ceres: Exploration of a small, volatile-rich world

On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres’ surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres’ dry exterior displays hydroxylated silicates, including ammoniated clays of endogenous origin. The possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits, lobate flows of materials, and a singular mountain that appears to be an extrusive cryovolcanic dome. On one occasion, Ceres temporarily interacted with the solar wind, producing a bow shock accelerating electrons to energies of tens of kilovolts

The varied sources of faculae-forming brines in Ceres’ Occator crater emplaced via hydrothermal brine effusion

Before acquiring highest-resolution data of Ceres, questions remained about the emplacement mechanism and source of Occator crater's bright faculae. Here we report that brine effusion emplaced the faculae in a brine-limited, impact-induced hydrothermal system. Impact-derived fracturing enabled brines to reach the surface. The central faculae, Cerealia and Pasola Facula, postdate the central pit, and were primarily sourced from an impact-induced melt chamber, with some contribution from a deeper, pre-existing brine reservoir. Vinalia Faculae, in the crater floor, were sourced from the laterally extensive deep reservoir only. Vinalia Faculae are comparatively thinner and display greater ballistic emplacement than the central faculae because the deep reservoir brines took a longer path to the surface and contained more gas than the shallower impact-induced melt chamber brines. Impact-derived fractures providing conduits, and mixing of impact-induced melt with deeper endogenic brines, could also allow oceanic material to reach the surfaces of other large icy bodies. The second extended phase of the Dawn mission provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show that the central faculae were sourced in an impact-induced melt chamber, with a contribution from the deep brine reservoir, while the Vinalia Faculae were sourced by the deep brine reservoir alone