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
The evidence for abundant liquid water on early Mars despite the faint young Sun is a long‐standing problem in planetary research. Here we present new ab initio spectroscopic and line‐by‐line climate ...calculations of the warming potential of reduced atmospheres on early Mars. We show that the strength of both CO2–H2 and CO2–CH4 collision‐induced absorption (CIA) has previously been significantly underestimated. Contrary to previous expectations, methane could have acted as a powerful greenhouse gas on early Mars due to CO2–CH4 CIA in the critical 250–500 cm−1 spectral window region. In atmospheres of 0.5 bar CO2 or more, percent levels of H2 or CH4 raise annual mean surface temperatures by tens of degrees, with temperatures reaching 273 K for pressures of 1.25–2 bars and 2–10% of H2 and CH4. Methane and hydrogen produced following aqueous alteration of Mars' crust could have combined with volcanically outgassed CO2 to form transient atmospheres of this composition 4.5–3.5 Ga. Our results also suggest that inhabited exoplanets could retain surface liquid water at significant distances from their host stars.
Key Points
New ab initio and line‐by‐line calculations show that warming by H2 in CO2 atmospheres is far stronger than previously believed
Contrary to previous research, we show that methane could also have been an effective greenhouse gas on early Mars
Reducing atmospheres could have been produced transiently by a combination of aqueous alteration of Mars' crust and volcanic CO2 outgassing
We develop an absolute flux density scale for centimeter-wavelength astronomy by combining accurate flux density ratios determined by the Very Large Array between the planet Mars and a set of ...potential calibrators with the Rudy thermophysical emission model of Mars, adjusted to the absolute scale established by the Wilkinson Microwave Anisotropy Probe. The radio sources 3C123, 3C196, 3C286, and 3C295 are found to be varying at a level of less than ~5% per century at all frequencies between 1 and 50 GHz, and hence are suitable as flux density standards. We present polynomial expressions for their spectral flux densities, valid from 1 to 50 GHz, with absolute accuracy estimated at 1%-3% depending on frequency. Of the four sources, 3C286 is the most compact and has the flattest spectral index, making it the most suitable object on which to establish the spectral flux density scale. The sources 3C48, 3C138, 3C147, NGC 7027, NGC 6542, and MWC 349 show significant variability on various timescales. Polynomial coefficients for the spectral flux density are developed for 3C48, 3C138, and 3C147 for each of the 17 observation dates, spanning 1983-2012. The planets Venus, Uranus, and Neptune are included in our observations, and we derive their brightness temperatures over the same frequency range.
We report on the in‐flight performance of the Solar Wind Ion Analyzer (SWIA) and observations of the Mars‐solar wind interaction made during the Mars Atmosphere and Volatile EvolutioN (MAVEN) prime ...mission and a portion of its extended mission, covering 0.85 Martian years. We describe the data products returned by SWIA and discuss the proper handling of measurements made with different mechanical attenuator states and telemetry modes, and the effects of penetrating and scattered backgrounds, limited phase space coverage, and multi‐ion populations on SWIA observations. SWIA directly measures solar wind protons and alpha particles upstream from Mars. SWIA also provides proxy measurements of solar wind and neutral densities based on products of charge exchange between the solar wind and the hydrogen corona. Together, upstream and proxy observations provide a complete record of the solar wind experienced by Mars, enabling organization of the structure, dynamics, and ion escape from the magnetosphere. We observe an interaction that varies with season and solar wind conditions. Solar wind dynamic pressure, Mach number, and extreme ultraviolet flux all affect the bow shock location. We confirm the occurrence of order‐of‐magnitude seasonal variations of the hydrogen corona. We find that solar wind Alfvén waves, which provide an additional energy input to Mars, vary over the mission. At most times, only weak mass loading occurs upstream from the bow shock. However, during periods with near‐radial interplanetary magnetic fields, structures consistent with Short Large Amplitude Magnetic Structures and their wakes form upstream, dramatically reconfiguring the Martian bow shock and magnetosphere.
Key Points
SWIA provides direct and proxy measurements of solar wind input to Mars
The Mars‐solar wind interaction varies with solar wind conditions and season
Mars only perturbs the upstream medium weakly, except during radial IMF
ABSTRACT We report on the discovery and validation of Kepler-452b, a transiting planet identified by a search through the 4 years of data collected by NASA's Kepler Mission. This possibly rocky ...planet orbits its G2 host star every days, the longest orbital period for a small ( ) transiting exoplanet to date. The likelihood that this planet has a rocky composition lies between 49% and 62%. The star has an effective temperature of 5757 85 K and a of 4.32 0.09. At a mean orbital separation of AU, this small planet is well within the optimistic habitable zone of its star (recent Venus/early Mars), experiencing only 10% more flux than Earth receives from the Sun today, and slightly outside the conservative habitable zone (runaway greenhouse/maximum greenhouse). The star is slightly larger and older than the Sun, with a present radius of and an estimated age of ∼6 Gyr. Thus, Kepler-452b has likely always been in the habitable zone and should remain there for another ∼3 Gyr.
The case for biotech on Mars Nangle, Shannon N; Wolfson, Mikhail Y; Hartsough, Lucas ...
Nature biotechnology,
04/2020, Letnik:
38, Številka:
4
Journal Article
Recenzirano
The stepwise application of biotechnology will be instrumental to addressing four key challenges of Martian settlement.
We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment ...indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean Vienna standard mean ocean water (VSMOW). Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.
Sand-grain-sized computers, self-healing materials and constellations of craft would reboot our reach, explain Igor Levchenko, Michael Keidar and colleagues.
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