The Penetration of Solar Radiation into Carbon Dioxide Ice

Icy surfaces behave differently to rocky or regolith‐covered surfaces in response to irradiation. A key factor is the ability of visible light to penetrate partially into the subsurface. This results in the Solid‐State Greenhouse Effect (SSGE), as ices can be transparent or translucent to visible and shorter wavelengths, whilst opaque in the infrared. This can lead to significant differences in shallow sub‐surface temperature profiles when compared to rocky surfaces. Of particular significance for modelling the SSGE is the e‐folding scale, otherwise known as the absorption scale length, or penetration depth, of the ice. Whilst there have been measurements for water ice and snow, pure and with mixtures, to date there have been no such measurements published for carbon dioxide ice. After an extensive series of measurements we are able to constrain the e‐folding scale of CO2 ice for the cumulative wavelength range 300 nm to 1100 nm, which is a vital parameter in heat transfer models for the Martian surface, enabling us to better understand surface‐atmosphere interactions at Mars’ polar caps

Characterization and mapping of surface physical properties of Mars from CRISM multi-angular data: application to Gusev Crater and Meridiani Planum

The analysis of the surface texture from the particle (grain size, shape and internal structure) to its organization (surface roughness) provides information on the geological processes. CRISM multi-angular observations (varied emission angles) allow to characterize the surface scattering behavior which depends on the composition but also the material physical properties (e.g., grain size, shape, internal structure, the surface roughness). After an atmospheric correction by the Multi-angle Approach for Retrieval of the Surface Reflectance from CRISM Observations, the surface reflectances at different geometries are analyzed by inverting the Hapke photometric model depending on the single scattering albedo, the 2-term phase function, the macroscopic roughness and the 2-term opposition effects. Surface photometric maps are created to observe the spatial variations of surface scattering properties as a function of geological units at the CRISM spatial resolution (200m/pixel). An application at the Mars Exploration Rover (MER) landing sites located at Gusev Crater and Meridiani Planum where orbital and in situ observations are available, is presented. Complementary orbital observations (e.g. CRISM spectra, THermal EMission Imaging System, High Resolution Imaging Science Experiment images) are used for interpreting the estimated Hapke photometric parameters in terms of physical properties. The in situ observations are used as ground truth to validate the interpretations. Varied scattering properties are observed inside a CRISM observation (5x10km) suggesting that the surfaces are controlled by local geological processes (e.g. volcanic resurfacing, aeolian and impact processes) rather than regional or global. Consistent results with the in situ observations are observed thus validating the approach and the use of photometry for the characterization of Martian surface physical properties

La fin du Moyen Âge, un moment charnière pour l’histoire des femmes ? Les embarras de la périodisation

Amiens. Échevinage du 19 janvier 1511. La corporation des sayeteurs-drapiers procède au renouvellement de ses ordonnances. Alors que les femmes constituent une part essentielle des effectifs d’une industrie décrite comme « le principal vivre du commun populaire d’icelle ville », les autorités prennent à cette occasion une décision pour le moins étonnante : 23. Item, que doresenavant une femme lyée de mary ne puist estre apprentisse dudict mestier soubz qui que ce soit ; aultrement ledict mest..

Lucie Laumonier, Solitudes et solidarités en ville. Montpellier, mi XIIIe-fin XVe siècle

Chercheure à l’université du Minnesota et docteure en histoire des universités de Montpellier III et de Sherbrooke (Canada), Lucie Laumonier a publié en 2015, aux éditions Brepols, un ouvrage intitulé Solitudes et solidarités en ville. Montpellier, mi XIIIe-fin XVe siècles. Ce travail, résultat d’une thèse réalisée sous la direction de Geneviève Dumas et Daniel Le Blévec, consiste en un examen détaillé de ceux et celles qui, échappant aux solidarités familiales, vivent seuls à la fin du Moyen..

Dark spots and cold jets in the polar regions of Mars: new clues from a thermal model of surface CO ice

International audienceObservations of the Martian CO ice cap in late winter and spring have revealed exotic phenomena. Unusual dark spots, fans and blotches form as the south-polar seasonal CO ice cap retreats. The formation mechanisms of these features are not clearly understood. Theoretical models suggest that photons could penetrate deep into the CO ice down to the regolith, leading to basal sublimation and gas and dust ejection. We have developed a detailed thermal model able to simulate the temporal evolution of the regolith-CO ice layer-atmosphere column. It takes into account heat conduction, radiative transfer within the ice and the atmosphere, and latent heat exchange when there is a phase transition. We found that a specific algorithm, fully coupling these 3 components, was needed to properly predict ice sublimation below the surface. Our model allows us to determine under what conditions basal sublimation is possible and thus when and where it can occur on Mars. Our results show that basal sublimation is possible if we consider large pathlengths and very little dust content within the ice. Moreover, the model can explain how dark spots can appear very early after the end of the polar night at high latitudes. We also evaluate the importance of the different parameters in our simulations. Contrary to what was suggested by theoretical models, the role of seasonal thermal waves is found to be limited. Solar radiation alone can initiate basal sublimation, which therefore only depends on the CO ice properties. Three main modes were identified: one where condensation/sublimation only occurs at the surface (in the case of small grains and/or high dust content), one where basal sublimation is possible (large pathlengths and very little dust content) and an intermediate mode where sublimation within the ice may occur. We suggest that these different modes could be keys to understanding many processes that occur at the surface of Mars, like the anticryptic area behavior or the recent reported activity in gullies

Recherche de la paix intérieure et réclusion féminine : l’exemple d’Amiens à la fin du Moyen Âge

La recherche de la paix intérieure est souvent associée à des formes et des conditions de vie austères où les individus en quête d’une foi profonde abandonnent le siècle pour vivre entièrement dans un cadre religieux, collectif ou individuel. Si la réclusion figure comme une de ces voies spirituelles, elle comporte toutefois une originalité : l’enfermement du pénitent solitaire au sein d’un espace réduit et confiné – que l’on nomme selon les sources reclusoir, renclusage ou recluserie – ne se..

Rupturas y continuidades en las condiciones de vida en la Argentina: un análisis a partir del gasto de consumo de los hogares entre 1996 y 2013

En los últimos años han ocurrido cambios en una importante cantidad de países de América Latina que se observan, entre otras cosas, en la modificación de los patrones de acumulación, el crecimiento económico y la disminución de la desigualdad. El resultado de estas transformaciones se ha evidenciado no sólo en el comportamiento de la distribución del ingreso sino también -y de manera significativa- en las pautas de consumo de los hogares. Estas constituyen, desde nuestra perspectiva, un indicador clave para analizar la evolución de las condiciones de vida de la población por su capacidad de reflejar el impacto redistributivo en diversos aspectos de la realidad social, económica y cultural. A partir de esta concepción, el presente trabajo se propone estudiar los gastos de consumo de los hogares en la Argentina utilizando como fuente las mediciones de la Encuesta Nacional de Gastos de los Hogares realizadas por el Instituto Nacional de Estadística y Censos entre los años 1996 y 2013Facultad de Humanidades y Ciencias de la Educació

Material ejection by the cold jets and temperature evolution of the south seasonal polar cap of Mars from THEMIS/CRISM observations and implications for surface properties

As the seasonal CO_2 ice polar caps of Mars retreat during spring, dark spots appear on the ice in some specific regions. These features are thought to result from basal sublimation of the transparent CO_2 ice followed by ejection of regolith-type material, which then covers the ice. We have used Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) reflectance data, Thermal Emission Imaging System (THEMIS) visible images, and THEMIS-derived temperature retrievals along with a thermal numerical model to constrain the physical and compositional characteristics of the seasonal cap for several areas exhibiting dark spots at both high spatial and temporal resolutions. Data analysis suggests an active period of material ejection (before solar longitude (Ls) 200), accumulation around the ejection points, and spreading of part of the ejected material over the whole area, followed by a period where no significant amount of material is ejected, followed by complete defrosting (≈ Ls 245). Dark material thickness on top of the CO_2 ice is estimated to range from a few hundreds of microns to a few millimeters in the warmest spots, based on numerical modeling combined with the observed temperature evolution. The nature of the venting process and the amount of material that is moved lead to the conclusion that it could have an important impact on the surface physical properties

Faire communauté : éléments bibliographiques

Généralités « Communes and community », dans The Oxford Dictionary of Middle Ages, dir. Robert E. Bjork, Oxford, Oxford University Press, 2010, 4 vol., t. II, p. 428. Michaud-Quantin, Pierre, Universitas : expressions du mouvement communautaire dans le Moyen Âge latin, Paris, Vrin, 1970. Vivre en société au Moyen Âge. Occident chrétien vie–xve siècle, dir. Claude Carozzi, Daniel Le Blevec et Huguette Taviani-Carozzi, Aix-en-Provence, Publications de l’Université de Provence, 2008. Individu, ..