Molecular gas species in the lunar atmosphere

There is good evidence for the existence of very small amounts of methane, ammonia and carbon dioxide in the very tenuous lunar atmosphere which consists primarily of the rare gases helium, neon and argon. All of these gases, except⁴⁰Ar, originate from solar wind particles which impinge on the lunar surface and are imbedded in the surface material. Here they may form molecules before being released into the atmosphere, or may be released directly, as is the case for rare gases. Evidence for the existence of the molecular gas species is based on the pre-dawn enhancement of the mass peaks attributable to these compounds in the data from the Apollo 17 Lunar Mass Spectrometer. Methane is the most abundant molecular gas but its concentration is exceedingly low, 1 × 10³ mol cm^?3, slightly less than³⁶Ar, whereas the solar wind flux of carbon is approximately 2000 times that of³⁶Ar. Several reasons are advanced for the very low concentration of methane in the lunar atmosphere.     

A Unifying Phase Diagram for the Dynamics of Sheared Solids and Granular Materials

We present a simple unifying model that can be used to analyze, within a single framework, different dynamic regimes of shear deformation of brittle, plastic, and granular materials. The basic dynamic regimes seen in the response of both solids and granular materials to slowly increasing loading are scale-invariant behavior with power law statistics, quasi-periodicity of system size events, and persisting long term mode switching between the former two types of response. The model provides universal analytical mean field results on the statistics of failure events in the different regimes and distributed versus localized spatial responses. The results are summarized in a phase diagram spanned by three tuning parameters: dynamic strength change (weakening, neutral or strengthening) during slip events, dissipation of stress transfer (related to the void fraction in granular materials and damaged solids), and the ratio of shear rate over healing rate controlling the regaining of cohesion following failures in brittle solids. The mean field scaling predictions agree with experimental, numerical, and observational data on deformation avalanches of solids, granular materials, and earthquake faults. The model provides additional predictions that should be tested with future observation and simulation data.     

A facies geological test of stable isotope interpretation of the Upper Permian depositional environment in West Spitsbergen

Lithofacies analysis of two transgressive sequences within the Kapp Starostin Formation (Upper Permian, West Spitsbergen), indicates considerable differences in seawater chemistry between their depositional environments. The onshore part of the sequence represented in the Vøringen and Svenskeegga Members is largely calcareous, with allochthonous and corroded siliceous materials. In contrast, in the equivalent sequence within the Hovtinden Member, silica is ubiquitous whereas carbonate materials include mainly corroded bioclasts. These differences are consistent with predictions of the oceanographic model of ‘overfed’ and ‘hungry’ oceans proposed previously on the basis of carbon and oxygen stable isotope analysis.     

Psychological factors in remote sensing: A review of some recent research

We review recent psychological research that pertains to remote sensing, with a focus on two major problem areas: The problem of eliciting and characterizing the knowledge of expert interpreters of remotely‐sensed data, and the problem of how to best utilize color in remote sensing displays. This research has immediate relevance to many remote sensing activities, but it also has broader implications. One general implication is that experimental psychology offers concepts and research methods that can be of benefit to the field of remote sensing. It is possible to discover the principles involved in the design of “good”; remote sensing displays, and the design of methods for teaching novices how to interpret remote sensing displays. A second broad implication of the psychological research is that remote sensing, as traditionally conceived, is actually just one part of a larger process of “remote perceiving.”; This idea is pursued in a second article (Hoffman, 1990), in which an attempt is made to characterize remote sensing as a unified science.     

Using δ15N in Fish Larvae as an Indicator of Watershed Sources of Anthropogenic Nitrogen: Response at Multiple Spatial Scales

There is growing interest in applying ??¹⁵N in biota as an indicator of anthropogenic nutrient inputs to coastal environments because changes in ??¹⁵N correlate to inputs of land-based nutrients. In complex coastal receiving waters, however, land-use effects on biota ??¹⁵N may be masked by local hydrologic processes, especially exchange with coastal waters of different geochemical character. We examined ??¹⁵N differences among larval fish, a novel biotic indicator, in coastal receiving waters at both among and within watershed scales. Our goal was to characterize how hydrologic processes within coastal river mouths and embayments mediate the effect of land-based N sources on larval fish ??¹⁵N. We sampled three Lake Superior river-embayment systems from watersheds that span a large population density gradient. Over all stations, mean fish ??¹⁵N ranged from 2.7??? to 10.8???. Within each system, we found a different pattern in ??¹⁵N across the river?Clake transition zone. Correlations between fish ??¹⁵N and water quality, particularly NH ₄ ⁺ and total nitrogen, were highly significant and corresponded to known differences in sewage waste water inputs. A multivariate model that included both watershed-based population density and NH ₄ ⁺ was found to provide the best fit to the ??¹⁵N data among a series of multi- and univariate candidate models. These results demonstrate that: (1) fish larvae ??¹⁵N responded at within watershed scales, and (2) within coastal receiving waters, fish larvae ??¹⁵N was related to waste water inputs at the watershed scale; however, expression at specific locations within a coastal system was strongly influenced by local hydrologic processes.