MGS TES observations of the water vapor above the seasonal and perennial ice caps during northern spring and summer

We report on new retrievals of water vapor column abundances from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data. The new retrievals are from the TES nadir data taken above the ‘cold’ surface areas in the North polar region (T_surf < 220 K, including seasonal frost and permanent ice cap) during spring and summer seasons, where retrievals were not performed initially. Retrievals are possible (with some modifications to the original algorithm) over cold surfaces overlaid by sufficiently warm atmosphere. The retrieved water vapor column abundances are compared to the column abundances observed by other spacecrafts in the Northern polar region during spring and summer and good agreement is found. We detect an annulus of water vapor growing above the edge of the retreating seasonal cap during spring. The formation of the vapor annulus is consistent with the previously proposed mechanism for water cycling in the polar region, according to which vapor released by frost sublimation during spring re-condenses on the retreating seasonal CO₂ cap. The source of the vapor in the vapor annulus, according to this model, is the water frost on the surface of the CO₂ at the retreating edge of the cap and the frost on the ground that is exposed by the retreating cap. Small contribution from regolith sources is possible too, but cannot be quantified based on the TES vapor data alone. Water vapor annulus exhibits interannual variability, which we attribute to variations in the atmospheric temperature. We propose that during spring and summer the water ice sublimation is retarded by high relative humidity of the local atmosphere, and that higher atmospheric temperatures lead to higher vapor column abundances by increasing the water holding capacity of the atmosphere. Since the atmospheric temperatures are strongly influenced by the atmospheric dust content, local dust storms may be controlling the release of vapor into the polar atmosphere. Water vapor abundances above the residual polar cap also exhibit noticeable interannual variability. In some years abundances above the cap are lower than the abundances outside of the cap, consistent with previous observations, while in the other years the abundances above the cap are higher or similar to abundances outside of the cap. We speculate that the differences may be due to weaker off-cap transport in the latter case, keeping more vapor closer to the source at the surface of the residual cap. Despite the large observed variability in water vapor column abundances in the Northern polar region during spring and summer, the latitudinal distribution of the vapor mass in the atmosphere is very similar during the summer season. If the variability in vapor abundances is caused by the variability of vapor sources across the residual cap then this would mean that they annually contribute relatively little vapor mass to significantly affect the vapor mass budget. Alternatively this may suggest that the vapor variability is caused by the variability of the polar atmospheric circulation. The new water vapor retrievals should be useful in tuning the Global Circulation Models of the martian water cycle.     

Dust aerosols above the south polar cap of Mars as seen by OMEGA

The time evolution of atmospheric dust at high southern latitudes on Mars has been determined using observations of the south seasonal cap acquired in the near infrared (1-2.65 μm) by OMEGA/Mars Express in 2005. Observations at different solar zenith angles and one EPF sequence demonstrate that the reflectance in the 2.64 μm saturated absorption band of the surface CO₂ ice is mainly due to the light scattered by aerosols above most places of the seasonal cap. We have mapped the total optical depth of dust aerosols in the near-IR above the south seasonal cap of Mars from mid-spring to early summer with a time resolution ranging from one day to one week and a spatial resolution of a few kilometers. The optical depth above the south perennial cap is determined on a longer time range covering southern spring and summer. A constant set of optical properties of dust aerosols is consistent with OMEGA observations during the analyzed period. Strong variations of the optical depth are observed over small horizontal and temporal scales, corresponding in part to moving dust clouds. The late summer peak in dust opacity observed by Opportunity in 2005 propagated to the south pole contrarily to that observed in mid spring. This may be linked to evidence for dust scavenging by water ice-rich clouds circulating at high southern latitudes at this season.     

H layering in the top meter of Mars

We explore the capability of a method of mapping the depth distribution of a hydrogen-rich layer in the top meter of Mars from the neutron currents measured by the Mars Odyssey Neutron Spectrometer. Assuming the soil can be modeled by two layers of known composition having different hydrogen contents, simulations allow an inversion of the neutron data into knowledge of depth and hydrogen content of the lower layer. The determination of these variables is sensitive to the hypothesis of chemical composition of the soil. We quantify this contribution to the uncertainty in the method first in terms of individual chemical elements and then in terms of macroscopic absorption cross sections. To minimize this source of error, an average composition was inferred from Mars Exploration Rover data. Possible compositions having a wide range of macroscopic absorption cross sections were used to evaluate the uncertainty associated with our calculations. We finally compare our results to ice table depth estimates predicted by two published theoretical models at locations where the composition is relatively well known. The fit is excellent in the southern high latitudes but questionable in the northern high latitudes. Possible explanations of these differences include the high geographical variations of the neutron currents relative to the spatial width of the response function of the instrument and the overly simple model we, of necessity, used for surface layering.     

Earth analog for high-latitude landforms and recent flows on Mars: Icy debris fans in the Wrangell Volcanic Field, Alaska

New Mars Reconnaissance Orbiter HiRise and CRISM imagery of polar layered terrain of Mars reveals striking similarities to icy debris fans along the base of steep escarpments in Alaska formed in high-latitude periglacial environments. Process and morphologic observations of a deglaciating site in the Wrangell Mountains reveal a complex suite of supraglacial processes involved in the construction of icy debris fans. Snow, ice, and sediment are delivered to the fans from degradation of an upper-level icecap. Alaskan icy debris fans were studied during an 8-day reconnaissance mission in July 2006. We directly observed 289 major depositional events dominated by dry snow/ice avalanches, but also including icy debris flows, rockfalls, small jokulhlaups, and glacial calving. Small fans with larger catchments receive episodic icy debris flows triggered by outburst flows that mobilize rockfall sediment temporarily stored in catchments above the fan apex. Large fans with smaller catchments have better linkage to the upper icecap, providing a direct pathway for frequent large avalanches. The large, avalanche-dominated fans thicken rapidly from an overabundance of snow/ice supply to the point where they become hybrid fan-glaciers. Surficial geology evolves rapidly in this high-latitude environment through both depositional events and solar-driven albedo changes that occur daily. Ground penetrating radar surveys show that subsurface sedimentary architecture and fan evolution is similar to the active surface processes and deposits observed on the fans. Direct field observations of active geomorphic processes provide unique insights on the pace and nature of high-latitude landscape evolution during climate changes on both planets.     

The effect of ground ice on the Martian seasonal CO2 cycle

The mostly carbon dioxide (CO₂) atmosphere of Mars condenses and sublimes in the polar regions, giving rise to the familiar waxing and waning of its polar caps. The signature of this seasonal CO₂ cycle has been detected in surface pressure measurements from the Viking and Pathfinder landers. The amount of CO₂ that condenses during fall and winter is controlled by the net polar energy loss, which is dominated by emitted infrared radiation from the cap itself. However, models of the CO₂ cycle match the surface pressure data only if the emitted radiation is artificially suppressed suggesting that they are missing a heat source. Here we show that the missing heat source is the conducted energy coming from soil that contains water ice very close to the surface. The presence of ice significantly increases the thermal conductivity of the ground such that more of the solar energy absorbed at the surface during summer is conducted downward into the ground where it is stored and released back to the surface during fall and winter thereby retarding the CO₂ condensation rate. The reduction in the condensation rate is very sensitive to the depth of the soil/ice interface, which our models suggest is about 8 cm in the Northern Hemisphere and 11 cm in the Southern Hemisphere. This is consistent with the detection of significant amounts of polar ground ice by the Mars Odyssey Gamma Ray Spectrometer and provides an independent means for assessing how close to the surface the ice must be. Our results also provide an accurate determination of the global annual mean size of the atmosphere and cap CO₂ reservoirs, which are, respectively, 6.1 and 0.9 hPa. They also indicate that general circulation models will need to account for the effect of ground ice in their simulations of the seasonal CO₂ cycle.     

THE SEARCH FOR OIL: FACTORS INFLUENCING US INVESTMENT IN FOREIGN PETROLEUM EXPLORATION AND DEVELOPMENT*

Determinants of foreign exploration and development spending by US oil companies are examined with multiple regression analysis. Since major US oil companies earn higher profits abroad, I test the role of profit rate surrogates and cash flow in a petroleum investment model. A high income tax rate is shown to discourage foreign oil investment, a finding that should be recognized by foreign governments. Institutional factors also appear to limit the flow of investment funds out of the United States, despite attractive foreign profit rates.     

Who’s afraid of red, yellow and green?: Redlining in Rotterdam

Redlining research is common practice in the US but not in other countries. Does this imply redlining does not take place elsewhere? This paper presents evidence from Rotterdam, the second largest city of the Netherlands, showing that in the 1990s it was impossible to get a home mortgage in large parts of the city. However, after Rotterdam joined the National Mortgage Guarantee (an institutional control measure) in 2000, hardly any evidence of redlining was found. This paper not only shows that redlining takes place outside of the US context, but also that a (discursive) treatment based on case study research has the possibility to gain a fuller understanding of redlining practices than a statistical/correlation analysis of mortgage data. Interviews with key actors are instrumental to unravelling how, why and when those in power make their decisions: agents are structured by the existing system while, at the same time, some of these agents have the power to re-produce as well as re-structure (transform) the system. One of the geographical outcomes of the agency-structure interaction is that credit is “redirected away from poorer to richer (and therefore “safer”) groups” as part of a strategy of risk avoidance [Leyshon and Thrift, 1997]. Thus redlining, like any other form of financial exclusion, deepens and accentuates prevailing levels of uneven development by creating geographical variations in access to the financial system [Dymski and Veitch, 1992].     

Bank branch closures in New Zealand: the application of a spatial interaction model

Banking is going through a revolution that is radically altering the way banks work and the way customers use them. It is a revolution driven by global competition and enabled by technology. Unlike the back-room developments of previous decades, contemporary restructuring is directly affecting the network of bank branches and opportunities customers have to interact with them. Today virtually all retailing banks are seeking ways of reducing their extensive and costly network of branches and experimenting with alternative means of interacting with customers. Many of the difficulties of deciding what branches to close relate to predicting the impact of such closures on remaining parts of the bank’s network. The aim of this paper is to illustrate the application of a GIS-based spatial interaction model designed to help banks make that decision. Applied in the New Zealand context, it draws attention to some of the opportunities, as well as difficulties, a spatial interaction model creates in assessing the consequences of closing branches, both for the bank itself and for the wider community.     

钢柱脚混凝土承台锚固性能弹塑性有限元分析

在试验研究基础上,采用ANSYS有限元分析程序,对钢柱脚混凝土承台在单向加载下的性能作了弹塑性分析,研究了其在竖向抗拔荷载作用下的开裂、变形及破坏的全过程,并在此基础上,建立了简化的抗拔承载力计算的桁架模型,计算结果与试验结果符合较好。     

青岛市海洋能源产业补贴法律问题研究

海洋能源产业补贴是政府或相关机构基于能源供给侧要求以及可持续发展的目标而对海洋能源生产活动中的企业或个人提供的财产性资助。财政补贴顺应了国家能源供给侧改革的要求以及可持续发展的目标。文章从海洋能源产业补贴的基础问题入手,结合青岛市海洋能源产业补贴的实践现状对其存在问题进行体系化分析。在厘清宏观层面的法律体系不完善与微观层面的制度缺位的基础上,探究青岛市海洋能源产业补贴制度的完善路径。从央地立法互动、增强法律规范间的协调性、完善海洋能源补贴专门性立法的层面,优化青岛海洋能源产业补贴的整体法律布局。从海洋能源创新科研补贴制度、海上发电产业税收优惠制度、海洋能源制造业转型升级补贴制度、海洋能源产业应急保障补贴制度层面,实现青岛市海洋能源产业补贴具体制度的构建。以期推动我国海洋能源产业补贴制度的法治化建设。