Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev crater

Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation.     

Nutrients in Carex exserta sod and gravel in Sequoia National Park, California

Nutrients in soil covered by Carex exserta sod and in adjacent unvegetated gravel areas were compared at Siberian Outpost, Sequoia National Park, California. The comparisons were part of a study to learn if Carex exserta meadow can be reestablished and if herbaceous cover on gravel areas can be increased. Grazing capacity and aesthetic appeal of denuded areas would be improved by better vegetative cover. The sod had higher concentrations of calcium, copper, iron, magnesium, manganese, nitrogen, potassium, and zinc than did the gravel areas. And it had a higher soil pH and percent organic matter. Sod and gravel did not differ in concentrations of phosphorus and sulfur. The differences were as might be expected between climax and badly deteriorated (or early seral) situations, and the results suggest that fertilization may be a useful treatment.         

Relationship of western juniper stem conducting tissue and basal circumference to leaf area and biomass

The ability to measure leaf area and biomass on a plant community basis has many important ecological applications. These include quantification of gas exchange, use of water resources on the site, nutrient pools, and construction of models simulating production and resource allocation. To test a nondestructive technique for estimating leaf area and leaf biomass of western juniper ( Juniperus occidentalis Hook.), sapwood area and basal circumference were evaluated as predictors of total leaf biomass and leaf area. Nineteen trees, ranging in size from 9.0 to 263 cm in circumference, were destructively sampled. The entire leaf biomass was harvested and measured, and regression equations were developed. Both sapwood area and basal circumference significantly (P < .01) correlated with projected leaf area and leaf biomass (r values = 0.98).     

Which neurological abnormalities and neuropsychological impairments share the same substrate in psychosis?

Approximately 60% of subjects with schizophrenia present minor neurological signs (neurological soft signs, NSS), which include abnormalities in sensory and motor performance indicative of a non-specific cerebral dysfunction. These are also present in healthy individuals and relatives of patients with psychosis, at significantly lower rates. The excess of NSS in psychosis may be a potential endophenotype for this disorder, and reflect the same neurodevelopmental brain dysfunction that also underlies the cognitive deficits consistently reported in psychosis. To establish whether neurological and cognitive dysfunction meet the essential criterion required for a refined endophenotype for psychosis, the association with the illness, we explored evidence that certain neurological and cognitive deficits co-occur in affected individuals. This evidence suggests that signs of motor dysfunctions may be specific to patients with psychosis, in whom they are associated with dysfunction in cognitive tasks requiring motor skills. Thus, they may form a promising candidate endophenotype for psychosis.     

First episode psychosis with extrapyramidal signs prior to antipsychotic drug treatment

Extrapyramidal movement disorders are common in chronic schizophrenia, and may be an intrinsic feature of the illness as well as related to antipsychotic drug treatment. Similar dysfunctions at illness onset may have implications for outcome, and for under- standing the mechanisms of illness. The objectives were to examine the clinical correlates of pre-treatment movement disorders at first episode of psychosis, and determine associations with neuropsychological function and striatal structure. Never medicated subjects were recruited from consecutive admissions to Early Psychosis Programs with defined catchment areas in Hong Kong, China, and Halifax, Canada. Standardized clinical, neuropsychological and brain imaging assessments were carried out at baseline and following acute and long term treatment with typical or atypical antipsychotic drugs. At the Hong Kong site, we studied 84 subjects with first episode psychosis (n = 10 with EPS). At the Halifax site, we studied 40 subjects with first episode psychosis (n = 17 with EPS), and 23 healthy comparison subjects. Subjects with movement disorders prior to treatment (EPS+) had higher total PANSS scores at baseline (mean elevation 19.9% Hong Kong, P = 0.016; 14.7% Halifax, P = 0.049). In subjects treated with atypical antipsychotics (all Halifax), EPS+ status at baseline predicted more movement disorders at long term follow up (P = 0.0005). In both cohorts, EPS+ subjects had poorer acute symptomatic treatment response assessed with the PANSS (Hong Kong P = 0.005; Halifax P = 0.017). Neuropsychological impairment related to executive dysfunction appeared greater in a small sam- ple of EPS+ subjects (Hong Kong, effect size 0.26-0.27, P < 0.05). Caudate volumes were 4.5% larger in EPS+ compared with EPS-subjects (Halifax P = 0.042), and correlations between striatal volumes and age were different in the EPS+ group. In conclu- sion, pre-treatment EPS is present in a substantial minority of subjects with first episode psychosis, appears to persist at long term follow up, and is associated with poorer response of symptoms to treatment. Selective impairment of executive function and stria- tal enlargement provides evidence of abnormalities of brain function and structure associated with this aspect of early psychosis.     

A low mass for Mars from Jupiter's early gas-driven migration

Jupiter and Saturn formed in a few million years (ref. 1) from a gas-dominated protoplanetary disk, and were susceptible to gas-driven migration of their orbits on timescales of only ～100,000 years (ref. 2). Hydrodynamic simulations show that these giant planets can undergo a two-stage, inward-then-outward, migration. The terrestrial planets finished accreting much later, and their characteristics, including Mars' small mass, are best reproduced by starting from a planetesimal disk with an outer edge at about one astronomical unit from the Sun (1 au is the Earth-Sun distance). Here we report simulations of the early Solar System that show how the inward migration of Jupiter to 1.5 au, and its subsequent outward migration, lead to a planetesimal disk truncated at 1 au; the terrestrial planets then form from this disk over the next 30-50 million years, with an Earth/Mars mass ratio consistent with observations. Scattering by Jupiter initially empties but then repopulates the asteroid belt, with inner-belt bodies originating between 1 and 3 au and outer-belt bodies originating between and beyond the giant planets. This explains the significant compositional differences across the asteroid belt. The key aspect missing from previous models of terrestrial planet formation is the substantial radial migration of the giant planets, which suggests that their behaviour is more similar to that inferred for extrasolar planets than previously thought.