Report of the Science Community Workshop on the proposed First Sample Depot for the Mars Sample Return Campaign     

Prepared by the MSR Campaign Science Group  A. D. Czaja  M.-P. Zorzano  the rest of the MCSG team  with Chairs  G. Kminek  M. A. Meyer  Members  D. W. Beaty  E. Sefton-Nash  B. L. Carrier  F. Thiessen  T. Haltigin  A. Bouvier  N. Dauphas  K. L. French  L. J. Hallis  R. L. Harris  E. Hauber  L. E. Rodriguez  S. P. Schwenzer  A. Steele  K. T. Tait  M. T. Thorpe  T. Usui  J. Vanhomwegen  M. A. Velbel  S. Edwin  K. A. Farley  D. P. Glavin  A. D. Harrington  L. E. Hays  A. Hutzler  M. Wadhwa 《Meteoritics & planetary science》2023,58(6):885-896

The Mars 2020/Mars Sample Return (MSR) Sample Depot Science Community Workshop was held on September 28 and 30, 2022, to assess the Scientifically-Return Worthy (SRW) value of the full collection of samples acquired by the rover Perseverance at Jezero Crater, and of a proposed subset of samples to be left as a First Depot at a location within Jezero Crater called Three Forks. The primary outcome of the workshop was that the community is in consensus on the following statement: The proposed set of ten sample tubes that includes seven rock samples, one regolith sample, one atmospheric sample, and one witness tube constitutes a SRW collection that: (1) represents the diversity of the explored region around the landing site, (2) covers partially or fully, in a balanced way, all of the International MSR Objectives and Samples Team scientific objectives that are applicable to Jezero Crater, and (3) the analyses of samples in this First Depot on Earth would be of fundamental importance, providing a substantial improvement in our understanding of Mars. At the conclusion of the meeting, there was overall community support for forming the First Depot as described at the workshop and placing it at the Three Forks site. The community also recognized that the diversity of the Rover Cache (the sample collection that remains on the rover after placing the First Depot) will significantly improve with the samples that are planned to be obtained in the future by the Perseverance rover and that the Rover Cache is the primary target for MSR to return to Earth.  相似文献   

Implications of management strategies and vegetation change in the Mount St. Helens blast zone     

Luke J. Marzen  Zoltan Szantoi  Lisa M.B. Harrington  John A. Harrington Jr 《国际地球制图》2013,28(5):359-376

The 1980 eruptions of Mount St. Helens provided an excellent opportunity for scientists to investigate the recovery of vegetation communities following a major geologic disturbance. An important and often overlooked aspect in these studies is the human factor in recovery processes, and specifically, the different management approaches taken towards re-establishment of vegetation on lands under the control of various owners. This study examines vegetation changes throughout the 1980 blast zone using a time series of Landsat-derived Normalized Difference Vegetation Index (NDVI) images and change detection methods to assess the changes over 25 years, from 1980 to 2005, as a function of human management combined with ecological factors. This long-term tracking of change indicates that differences in the speed of vegetation re-establishment and consequent rates of change substantially reflect human involvement and varying management strategies.  相似文献   

TEMPORAL STATISTICS: AN APPLICATION IN SNOWFALL CLIMATOLOGY     

John A. Harrington Jr.  Randall S. Cerveny 《自然地理学》2013,34(4):337-353

A method is introduced for the analysis of temporal distributions of climatic data based on a comparison of a variable's frequency distribution in the time dimension to a standard bell-shaped curve through time. The following statistics are defined using mean monthly snowfall data: the temporal mean, which is the average time for accumulation of 50% of the annual snowfall total; the temporal standard deviation, which characterizes the mean annual spread of snowfall accumulation about the mean; temporal skewness, which characterizes the symmetry of the annual snowfall distribution; temporal kurtosis, which measures the peakedness of the annual distribution; and temporal correlation, which quantifies the degree of association between two temporal distributions. Analysis of snowfall data demonstrates the utility of temporal statistics for quantifying temporal and geographic variations in a climatic variable's seasonal distribution. [Key words: snowfall, climatology, temporal statistics.]  相似文献   

Groundwater Quality Impacts from a Full‐Scale Integrated Constructed Wetland     

Mawuli Dzakpasu  Miklas Scholz  Rory Harrington  Valerie McCarthy  Siobhán Jordan 《Ground Water Monitoring & Remediation》2014,34(3):51-64

The concept of integrated constructed wetlands (ICW) promotes in‐situ soils to construct and line wetland cells. The integrity of soil material, however, may provide a potential pathway for contaminants to flow into the underlying groundwater. This study assessed the extent of groundwater quality deterioration due to the establishment of a full‐scale ICW system treating domestic wastewater in Ireland. The ICW is located at Glaslough in Co. Monaghan, Ireland. It consists of two sedimentation ponds and a sequence of five shallow vegetated wetland cells. The ICW cells were lined with 500‐mm thick local subsoil material, which comprised a mixture of alluvium, organic soils, tills, and gravel. Groundwater samples and head data were collected from eight piezometers, which were installed around the ICW cells. The groundwater and wetland water samples were analysed for water quality parameters such as bulk organic matter, nutrients, and pathogens. Overall, the quality of groundwater underlying the ICW system recorded some contamination with bulk organic matter and some inorganic nutrients. Significantly higher contaminant concentrations were recorded in monitoring wells upgradient and near to the distal wetland cells than downgradient ones, which were near to the proximal cells. For the downgradient piezometers, concentrations seldomly exceeded the natural background levels. Detailed analyses through the application of chemometrics models indicated that the source of contamination was largely of geogenic origin. Findings suggest that ICW systems pose a minimal risk to the groundwater quality; the greatest risk was associated with the distal wetland cells.  相似文献   

Tracking Groundwater Discharge to a Large River using Tracers and Geophysics   总被引：1，自引：0，他引：1  

Glenn A. Harrington  W. Payton Gardner  Tim J. Munday 《Ground water》2014,52(6):837-852

Few studies have investigated large reaches of rivers in which multiple sources of groundwater are responsible for maintaining baseflow. This paper builds upon previous work undertaken along the Fitzroy River, one of the largest perennial river systems in north‐western Australia. Synoptic regional‐scale sampling of both river water and groundwater for a suite of environmental tracers (⁴He, ⁸⁷Sr/⁸⁶Sr, ²²²Rn and major ions), and subsequent modeling of tracer behavior in the river, has enabled definition and quantification of groundwater input from at least three different sources. We show unambiguous evidence of both shallow “local” groundwater, possibly recharged to alluvial aquifers beneath the adjacent floodplain during recent high‐flow events, and old “regional” groundwater introduced via artesian flow from deep confined aquifers. We also invoke hyporheic exchange and either bank return flow or parafluvial flow to account for background ²²²Rn activities and anomalous chloride trends along river reaches where there is no evidence of the local or regional groundwater inputs. Vertical conductivity sections acquired through an airborne electromagnetic (AEM) survey provide insights to the architecture of the aquifers associated with these sources and general groundwater quality characteristics. These data indicate fresh groundwater from about 300 m below ground preferentially discharging to the river, at locations consistent with those inferred from tracer data. The results demonstrate how sampling rivers for multiple environmental tracers of different types—including stable and radioactive isotopes, dissolved gases and major ions—can significantly improve conceptualization of groundwater—surface water interaction processes, particularly when coupled with geophysical techniques in complex hydrogeological settings.  相似文献   

Potential climate change effects on warm-season livestock production in the Great Plains   总被引：1，自引：0，他引：1  

Terry L. Mader  Katrina L. Frank  John A. Harrington Jr.  G. Leroy Hahn  John A. Nienaber 《Climatic change》2009,97(3-4):529-541

Projected production responses were derived for confined swine and beef and for milk-producing dairy cattle based on climate change projections in daily ambient temperature. Milk production from dairy cattle and the number of days to grow swine and beef cattle were simulated. Values were obtained for three central United States transects and three climate scenarios which were based on projected mean daily ambient temperatures associated with a baseline, doubling, and tripling of atmospheric greenhouse gas (CO₂) levels for the period June 1 to October 31. For swine, a slight northwest to southeast gradient is evident. Transect 1 (west side) shows no losses under the doubling scenario and losses up to 22.4% under the tripling scenario. Transect 3 (east side) displays losses of over 70% under the tripling scenario. For beef, positive benefits were simulated in Transect 1 with increasing temperatures, although a northwest to southeast gradient was also evident. For dairy, no positive benefits in milk production were found due to climate effects. Projected production declines ranged from 1% to 7.2%, depending on location. However, ranges in predicted differences were less than those simulated for beef and swine. These simulations suggest regional differences in animal production due to climate change will be apparent. For small changes in climate conditions, animals will likely be able to adapt, while larger changes in climate conditions will likely dictate that management strategies be implemented. Exploration of the effects of climate changes on livestock should allow producers to adjust management strategies to reduce potential impact and economic losses due to environmental changes.  相似文献   

Behaviour of a hydrodynamic finite element model     

R.A. Harrington  N. Kouwen  G.J. Farquhar 《Advances in water resources》1978,1(6):331-335

A finite element model which solves the vertically integrated momentum and continuity equations is described. Linear triangular elements are used to describe the geometry and parameter variations. The Galerkin method of weighted residuals is employed to cast the equations in a form amenable to numerical solution. The model is based on a fully implicit formulation using finite differences for the temporal derivatives.Means of evaluating the non-linear terms of the governing equations are described, and model results are presented for a frictionless tidal channel. The example is chosen such that the non-linearities have a large influence on the solution, and as a result the linearization scheme significantly affects the model's behaviour.Suppression of the non-linear instabilities generated by the convective terms in the momentum equations is examined for the case of flow around a 180° bend. Both the imposition of artificially high roughness coefficients and the use of an effective eddy viscosity are examined in terms of their ability to damp the oscillations which arise for this example.Finally, model results are presented for a case study involving determination of remedial measures to improve flow conditions at a river outfall in Southern Ontario.  相似文献   

Beef feedlots in southwestern Kansas: local change, perceptions, and the global change context     

Lisa M. B. Harrington  Max Lu 《Global Environmental Change》2002,12(4)

Cattle feedlots, some of which have a capacity of tens of thousands of head, have become a major driving force in the local economy and changing landscape of southwestern Kansas. The feedlot industry also is one of the region's most important sources of carbon-equivalent greenhouse gases. Changes to the beef industry are described, and the perceptions and attitudes of feedlot operators regarding climatic change issues and industrial change are analyzed based on a 1998 survey. The results indicate that a majority of feedlot respondents believe ‘global warming’ is mostly an unproven theory, and efforts to mitigate it are unwarranted.  相似文献   

Synergistic effects of diuron and sedimentation on photosynthesis and survival of crustose coralline algae     

Harrington L  Fabricius K  Eaglesham G  Negri A 《Marine pollution bulletin》2005,51(1-4):415-427

Effects of short-term exposure to sedimentation and diuron, separately and in combination, on the photophysiology and survival of crustose coralline algae (CCA) were examined in controlled time-course experiments, using pulse-amplitude modulation (PAM) chlorophyll fluorometry. These experiments indicated that the effects of sediments and diuron, when applied in isolation, were often reversible, with recovery time dependent upon sediment type and diuron concentration. Exposure to fine (<63 microm grain size), nutrient-rich estuarine sediments reduced effective quantum yields (Delta F/F(m')) of photosystem II in CCA species more than exposure to the same amount of fine (<63 microm grain size) calcareous sediments. Significant inhibition of photosynthesis (Delta F/F(m')) was also observed at diuron concentrations > or =2.9 microg L(-1). Fine estuarine sediments in combination with 0.79 microg L(-1) dissolved diuron, caused yields (Delta F/F(m')) to drop by 60% compared with controls after 24 h. The combined exposure to sediments and diuron also retarded recovery, thus Delta F/F(m') values were still only 60% of the controls after 9 days recovery in clean seawater. Mortality of CCA was observed in some fragments treated with combinations of sediment and diuron. Our results suggest that sediment deposition and exposure to diuron can negatively affect the photosynthetic activity of CCA, with sedimentation stress being significantly enhanced by the presence of trace concentrations of diuron.  相似文献   

Structure of Saturn's Mesosphere from the 28 Sgr Occultations     

W.B. Hubbard  C.C. Porco  D.M. Hunten  G.H. Rieke  M.J. Rieke  D.W. McCarthy  V. Haemmerle  J. Haller  B. McLeod  L.A. Lebofsky  R. Marcialis  J.B. Holberg  R. Landau  L. Carrasco  J. Elias  M.W. Buie  E.W. Dunham  S.E. Persson  T. Boroson  S. West  R.G. French  J. Harrington  J.L. Elliot  W.J. Forrest  J.L. Pipher  R.J. Stover  A. Brahic  I. Grenier 《Icarus》1997,130(2):404-425

We analyze an extensive data set of immersion and emersion lightcurves of the occultation of 28 Sgr by Saturn's atmosphere on 3 July 1989. The data give profiles of number density as a function of altitude at a variety of latitudes, at pressures ranging from about 0.5 to about 20 μbar. The atmosphere is essentially isothermal in this range, with a temperature close to 140 K for an assumed mean molecular weight of 2.135. Owing to favorable ring geometry, an accurate radial scale is available for all observations, and we confirm the substantial equatorial bulge produced by zonal winds of ∼450 m/s first observed in the Voyager radio-occultation experiments. The fact that the bulge is still present at microbar pressures suggests that the equatorial winds persist to high altitudes. According to our radial scale, the 2.4-μbar level, which corresponds to half-flux in the stellar occultations, is at an equatorial radius of 60,960 km. This radial scale is in good agreement with the Voyager radio-occultation data at mbar pressures and allows smooth interpolation of the isothermal structure between the stellar-occultation and radio-occultation regions. We do not have such a smooth interpolation between our data and Voyager ultraviolet occultation data, unless we discard the lowest 200 km of Voyager ultraviolet data. When this is done, we obtain a complete atmospheric model from an equatorial radius of 61,500 km down to an equatorial radius of 60,500 km. This model gives excellent agreement between all 28 Sgr, Voyager, and Pioneer 11 data.  相似文献