We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Ceres’ composition has been a long-standing issue since the first ground-based observations because of its peculiar spectrum and lack of an established connection with meteorites. NASA’s Dawn mission acquired unprecedented measurements of the surface of the dwarf planet Ceres, bringing a breakthrough in the comprehension of the mineralogy of the surface. Ceres’ surface is a mixture of ultra-carbonaceous material, Mg-phyllosilicates, NH4-phyllosilicates, carbonates, organics, Fe-oxides, and volatiles, as determined by remote sensing instruments onboard Dawn: Visible and InfraRed imaging spectrometer (VIR), Gamma Ray and Neutron Detector (GRAND), and the Framing Camera (FC). The average mineralogy of Ceres reveals a possible past global aqueous alteration. Regional variations of such materials unveil possible processing acting on large scales, both endogenous and exogenous. Local areas of Ceres surface, on a spatial scale of a few kilometers, present significant spectral variations with respect to the measured average spectrum, and thus significant variation on the inferred mineralogy. Most imply recent or ongoing geological activity involving upwelling of subsurface carbonate-rich and salt-rich brines (Occator crater and Ahuna Mons), organic material (Ernutet crater), hydrated carbonates, and water ice (Oxo and Juling craters). Global aqueous alteration and recent hydrothermal activity place Ceres among the most interesting targets in astrobiology.
The early modern world was "organic" in the sense that humans got energy mostly by tapping and concentrating solar flows to grow food, and to heat their homes and to make other industrial products. Epidemic disease, famine, war, and other disasters kept human life expectancy much shorter than it is today. The "Columbian Exchange" refers to the exchange of plants, animals, and pathogens between the Americas and Afro-Eurasia following Christopher Columbus's voyage to the Americas in 1492. For Europeans who came to the Americas in the century after conquest, the "New" world appeared to be a cornucopia, stocked with nature's bounty there for the taking. The early modern period also saw the extension throughout the world of a particular kind of legal framework for human interaction with nature, built on idea of private ownership of property. States, markets, productive agriculture, and rising populations moved environmental change in America before 1492, in East and South Asia, and in Africa.
Les résultats présentés sont issus de l'analyse de 283 échantillons sédimentaires prélevés à 7 profondeurs différentes (- 5 à - 35 m) dans 10 lacs de la Franche-Comté jurassienne.La nature des particules constitutives des sédiments lacustres est examinée dans une première partie consacrée à l'analyse microparticulaire comparée du seston et des sédiments récents ainsi qu'à un bilan des valeurs du rapport C/N des apports organiques aux cuvettes lacustres.La recherche est ensuite centrée sur la dynamique de la transformation de la matière organique. En se fondant surle phénomène général de l'affinement des particules dans l'espace et dans le temps, les variations de la teneur en matière organique et du rapport C/N sont analysées en fonction de la taille des particules et de la hauteur d'eau.Des interprétations relatives au mode du fonctionnement des systèmes lacustres sont effectuées mais la complexitéde l'information contenue dans une valeur globale du rapport C/N conduit à proposer une analyse des formes de lamatière organique.
Recommend this
Email your librarian or administrator to recommend adding this to your organisation's collection.