Covering the first five decades of the exploration of Mars, this atlas is the most detailed visual reference available. It brings together, for the first time, a wealth of information from diverse ...sources, featuring annotated maps, photographs, tables and detailed descriptions of every Mars mission in chronological order, from the dawn of the space age to Mars Express. Special attention is given to landing site selection, including reference to some missions that were planned but never flew. Phobos and Deimos, the tiny moons of Mars, are covered in a separate section. Contemporary maps reveal our improving knowledge of the planet's surface through the latter half of the twentieth century. Written in non-technical language, this atlas is a unique resource for anyone interested in planetary sciences, the history of space exploration and cartography, while the detailed bibliography and chart data are especially useful for academic researchers and students.
The Zhurong landing was the biggest test yet of China's deep-space exploration capabilities. Within days, the rover could start to make geological discoveries.
CO oxidation promoted by a subnano Pt.sub.4 cluster deposited on the anatase a-TiO.sub.2(101) surface has been investigated by means of DFT + U calculations. The focus of the study is on the role of ...supported Pt.sub.4 in favoring the formation of an oxygen vacancy at interface sites between Pt.sub.4 and the TiO.sub.2 surface, a key step in CO oxidation reactions according to a Mars-van Krevelen mechanism. The motivation is to compare this reaction mechanism with other processes described in the literature for Pt clusters on anatase TiO.sub.2 where the reaction involves O.sub.2 dissociation at the surface of the metal particle or its activation at the metal/oxide interface. A significant decrease in the energetic cost to remove a lattice oxygen is observed at the interface sites between Pt.sub.4 and TiO.sub.2, compared to regular sites. This favors the CO oxidation processes by a direct interaction of the CO molecule with a lattice oxygen, with formation of CO.sub.2 and an oxygen vacancy. The processes is slightly endothermic, and occurs with barriers comparable, or even lower, than found for the case of Au nanoparticles supported on the same a-TiO.sub.2 (101) surface. The next step consists in the re-oxidation of the support. The calculations show that the O.sub.2 molecule adsorbs strongly on the reduced catalyst, dissociates with one O atom that recreates the stoichiometric surface, and the other that remains adsorbed on the surface, ready to react with a second CO molecule. Graphical
Mars methane detection and variability at Gale crater Webster, Christopher R.; Mahaffy, Paul R.; Atreya, Sushil K. ...
Science (American Association for the Advancement of Science),
01/2015, Letnik:
347, Številka:
6220
Journal Article
Recenzirano
Odprti dostop
Reports of plumes or patches of methane in the martian atmosphere that vary over monthly time scales have defied explanation to date. From in situ measurements made over a 20-month period by the ...tunable laser spectrometer of the Sample Analysis at Mars instrument suite on Curiosity at Gale crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 parts per billion by volume (ppbv) at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period (where 1 sol is a martian day), we observed elevated levels of methane of 7.2 ± 2.1 ppbv (95% CI), implying that Mars is episodically producing methane from an additional unknown source.
Mars spacecraft encounter numerous g-loads that occur along the launch or landing vectors (called axial vectors) or along lateral off-axes vectors. The goal of this research was to determine if there ...was a threshold for dislodging spores under brute-force dynamic shock compressional impacts (i.e., henceforth called shock-impacts) or long-term vibrationally induced g-loads that might simulate spacecraft launches or landings profiles. Results indicated that spores of Bacillus subtilis 168 and B. atrophaeus ATCC 9372 were dislodged from ChemFilm-coated aluminum coupons during shock impact events of 60 g’s or higher. In contrast, the threshold for dislodging B. pumilus SAFR-032 spores was approx. 80 g’s. Vibrational g-loading was conducted at approx. 12–15 g’s (z-axis) and 77 Hz. All three Bacillus spp. exhibited very modest spore dislodgement at 1, 4, or 8 min of induced vibrational g-loads. However, the numbers of spores released depended on the Earth’s g-vector relative to the bacterial monolayers. When the experimental hardware was placed in an ‘Up’ orientation (defined as the spores sat on the upper surface of the coupons and the coupons pointed up and away from Earth’s g-vector), zero to only a few spores were dislodged. When the experimental hardware was inverted and the coupon surfaces were in a ‘Down’ orientation, the number of spores released increased by 20–30 times. Overall, the results of both assays suggest that spores on spacecraft surfaces will not likely be dislodged during nominal launch and landing scenarios, with the exception of jettisoned hardware (e.g., heat shields or backshells) during landing that might hit the Martian terrain at high g’s. However, off-nominal landings hitting the Martian surface at >60 g’s are likely to release low numbers of spores into the atmosphere and regolith.
Con el incremento de las misiones de exploración espacial y por tanto el incremento resultante en la cantidad de rovers desplegados, su eficiencia de desplazamiento se enfrenta a nuevos retos. La ...interacción rueda-suelo juega un papel importante en el movimiento de estos rovers. Nuestra investigación está dirigida al estudio de esta interacción en los primeros instantes de la trayectoria. Los trabajos reportados hasta la actualidad, se enfocan en desplazamientos de largas distancias (aprox. 20-30 cm). Sin embargo, los autores creen que los primeros instantes son cruciales en el futuro desempeño del movimiento. En este trabajo, usando un dispositivo que permite múltiples y precisas repeticiones de un experimento de rodadura a gravedades controladas, se realiza una caracterización del movimiento de la rueda sobre suelo arenoso a la gravedad de Marte. Nuestro estudio revela que la gravedad influye en la eficiencia de rodadura. En los experimentos realizados a medida que disminuye la gravedad, la eficiencia del movimiento de la rueda empeora. With the increase of planetary exploration missions and thereby the resultant increase of extraterrestrial rovers deployed, their mobility performance meets new challenges. Wheel-soil interaction plays an important role in the movement of these rovers. Our research addresses the study of this interactions in the first moments of the trajectory. The investigations reported so far, focus on long-distance motion (approx. 20-30 cm). However, the authors believe that the firsts interactions are crucial for the future performance of the motion. Here, by means of a device that allows multiple and precise repetitions of a wheel rolling experiment at controlled gravities, we characterize the movement of a wheel on sandy soil, in the gravity of Mars. Our study reveals that gravity influences the performance of the wheel, under these conditions. The experiments show that, as the gravity decreases, the rolling efficiency also decreases. PACS: Image analysis (análisis de imágenes), 87.57.N-; Movement and locomotion (movimiento y locomoción), 87.85.gj; Motion sensors (sensores de movimiento), 07.07.Df; Mars (Marte), 96.30.Ge
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