Diurnal variations in optical depth at Mars: Observations and interpretations

Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Optical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combining these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday

Factors governing water condensation in the Martian atmosphere

Modeling results are presented suggesting a diurnal condensation cycle at high altitudes at some seasons and latitudes. In a previous paper, the use of atmospheric optical depth measurements at the Viking lander site to show diurnal variability of water condensation at different seasons of the Mars year was described. Factors influencing the amount of condensation include latitude, season, atmospheric dust content and water vapor content at the observation site. A one-dimensional radiative-convective model is used herein based on the diabatic heating routines under development for the Mars General Circulation Model. The model predicts atmospheric temperature profiles at any latitude, season, time of day and dust load. From these profiles and an estimate of the water vapor, one can estimate the maximum occurring at an early morning hour (AM) and the minimum in the late afternoon (PM). Measured variations in the atmospheric optical density between AM and PM measurements were interpreted as differences in AM and PM condensation

Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone

M-stars comprise 80% of main-sequence stars, and so their planetary systems provide the best chance for finding habitable planets, i.e.: those with surface liquid water. We have modelled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M-stars) using spectrally resolved data of the Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 ?m, combined with M-stars emitting a significant fraction of their radiation at these same longer wavelengths, mean that the albedos of ice and snow on planets orbiting M-stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M-stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M-stars may be 10-30% further away from the parent star than previously thought.Comment: Final accepted by Astrobiology, 20 pages (double spaced), 3 figures include

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

Like a star chart this volume orientates the reader to the key issues and debates in Pacific and Australasian biogeography, palaeoecology and human ecology. A feature of this collection is the diversity of approaches ranging from interpretation of the biogeographic significance of plant and animal distributional patterns, pollen analysis from peats and lake sediments to discern Quaternary climate change, explanation of the patterns of faunal extinction events, the interplay of fire on landscape evolution, and models of the environmental consequences of human settlement patterns. The diversity of approaches, geographic scope and academic rigor are a fitting tribute to the enormous contributions of Geoff Hope. As made apparent in this volume, Hope pioneered multidisciplinary understanding of the history and impacts of human cultures in the Australia- Pacific region, arguably the globe’s premier model systems for understanding the consequences of human colonization on ecological systems. The distinguished scholars who have contributed to this volume also demonstrate Hope’s enduring contribution as an inspirational research leader, collaborator and mentor. Terra Australis leave no doubt that history matters, not only for land management, but more importantly, in alerting settler and indigenous societies alike to their past ecological impacts and future environmental trajectories

Coastal erosion reveals a potentially unique Oligocene and possible periglacial sequence at present-day sea level in Port Davey, remote South-West Tasmania

Cut-back of a sea-cliff at Hannant Inlet in remote South-West Tasmania has exposed Oligocene clays buried under Late Pleistocene “colluvium” from which abundant wood fragments protrude. The two units are separated by a transitional interval defined by mixed Oligocene and Pleistocene microfloras. Microfloras preserved in situ in the clay provide a link between floras in Tasmania and other Southern Hemisphere landmasses following onset of major glaciation in East Antarctica during the Eocene-Oligocene transition (c. 34 Ma). The Late Pleistocene “colluvium” preserves abundant fossil pollen of the shrub conifer genus Pherosphaera (al. Microstrobos). Assuming the parent plants had the same upper subalpine-alpine ecology as living Pherosphaera hookeriana, the microflora provides evidence for cold, wet conditions in the Port Davey lowlands during a low sea-level stand. The same data highlight the failure of Pherosphaera to regain its Pleistocene distribution during the Postglacial period. Our data are inconclusive whether Late Pleistocene conditions in Hannant Inlet were periglacial, i.e., the Oligocene sediments were turbated by freeze-thaw processes, or have been reworked by fluvial processes into the Pleistocene “colluvium”. Nevertheless, the inferred cold-climate is consistent with the former hypothesis. The sequence is sealed under cross-bedded coarse quartzite gravels of presumed Last Glacial Stage age

Supraspinal inactivation of mitochondrial superoxide dismutase is a source of peroxynitrite in the development of morphine antinociceptive tolerance.

Effective treatment of chronic pain with morphine is limited by decreases in the drug’s analgesic action with chronic administration (antinociceptive tolerance). Because opioids are mainstays of pain management, restoring their efficacy has great clinical importance. We have recently reported that formation of peroxynitrite (ONOO(−), PN) in the dorsal horn of the spinal cord plays a critical role in the development of morphine antinociceptive tolerance and have further documented that nitration and enzymatic inactivation of mitochondrial superoxide dismutase (MnSOD) at that site provides a source for this nitroxidative species. We now report for the first time that antinociceptive tolerance is also associated with the inactivation of MnSOD at supraspinal sites. Inactivation of MnSOD led to nitroxidative stress as evidenced by increased levels of products of oxidative DNA damage and activation of the nuclear factor poly (ADP-ribose) polymerase in whole brain homogenates. Co-administration of morphine with potent Mn porphyrin-based peroxynitrite scavengers, (MnTE-2-PyP(5+) and MnTnHex-2-PyP(5+)) (1) restored the enzymatic activity of MnSOD, (2) attenuated PN derived nitroxidative stress, and (3) blocked the development of morphine induced antinociceptive tolerance. The more lipophilic analogue, MnTnHex-2-PyP(5+) was able to cross the blood brain barrier at higher levels than its lipophylic counterpart MnTE-2-PyP(5+) and was about 30 fold more efficacious. Collectively, these data suggest that peroxynitrite mediated enzymatic inactivation of supraspinal MnSOD provides a source of nitroxidative stress, which in turn contributes to central sensitization associated with the development of morphine antinociceptive tolerance. These results support our general contention that PN-targeted therapeutics may have potential as adjuncts to opiates in pain management

Testing peat humification analysis in an Australian context: identifying wet shifts in regional climate over the past 4000 years

Peat humification analysis is presented as a robust palaeoclimatic proxy, suitable for use on mid–late Holocene peat sequences situated in the Southern Hemisphere. The proxy is shown to permit the identification of wet and dry shifts in a peat sequence from the humid tropics of north-eastern Australia. A significant correlation is found between the humification record and other proxies indicative of past climate conditions such as pollen, δ13C, C/N and macrocharcoal. Sixteen wet shifts detected in the humification record for Bromfield Swamp occur at the following dates (with 2σ range): 3830 (3920–3740), 3560 (3640–3480), 3490 (3560–3420), 3380 (3450–3300), 3120 (3250–2970), 2950 (3100–2790), 2560 (2710–2450), 2430 (2600–2260), 2120 (2330–1910), 1750 (1980–1520), 1430 (1660–1200), 1170 (1390–960), 1010 (1220–820), 620 (770–500), 300 (400–200) and 100 (200–10) cal. yr BP. Eleven dry shifts are also identified in the record at 4220 (4330–4110), 3670 (3750–3590), 3330 (3420–3220), 3020 (3170–2870), 2350 (2530–2160), 2020 (2230–1800), 1730 (1980–1510), 1290 (1510–1070), 700 (870–560), 400 (470–300) and 260 (360–150) cal yr BP. Blechnum and Poaceae are identified by pollen analysis to be the dominant plants of the swamp surface over the past 4000 years. The ratio of these two plant taxa in the pollen record correlates well with identified wet and dry shifts. It is suggested that a ratio ≤1 possibly indicates dry conditions, a ratio of >1–3 indicates wet or dry conditions, and a ratio >3 implies wet conditions. Large macrocharcoal peaks are recorded during the initiation phase of the peat sequence at approximately 4090 cal. yr BP, and at 3700–3620 cal. yr BP, both of these time periods being coincident with dry phases. Isolated minor macrocharcoal peaks at ca. 2860, 2820, 2620, 2560, 2130, 1930, 1740 and 200 cal. yr BP are found to coincide with periods of average effective precipitation (based on the humification proxy) and so may reflect fire on the swamp surface, transport and re-deposition down-slope of old charcoal after a high rainfall event, or burning in the landscape by indigenous people

Ecological Consequences of a Millennium of Introduced Dogs on Madagascar

Introduced predators currently threaten endemic animals on Madagascar through predation, facilitation of human-led hunts, competition, and disease transmission, but the antiquity and past consequences of these introductions are poorly known. We use directly radiocarbon dated bones of introduced dogs (Canis familiaris) to test whether dogs could have aided human-led hunts of the island’s extinct megafauna. We compare carbon and nitrogen isotope data from the bone collagen of dogs and endemic “fosa” (Cryptoprocta spp.) in central and southwestern Madagascar to test for competition between introduced and endemic predators. The distinct isotopic niches of dogs and fosa suggest that any past antagonistic relationship between these predators did not follow from predation or competition for shared prey. Radiocarbon dates confirm that dogs have been present on Madagascar for over a millennium and suggest that they at least briefly co-occurred with the island’s extinct megafauna, which included giant lemurs, elephant birds, and pygmy hippopotamuses. Today, dogs share a mutualism with pastoralists who also occasionally hunt endemic vertebrates, and similar behavior is reflected in deposits at several Malagasy paleontological sites that contain dog and livestock bones along with butchered bones of extinct megafauna and extant lemurs. Dogs on Madagascar have had a wide range of diets during the past millennium, but relatively high stable carbon isotope values suggest few individuals relied primarily on forest bushmeat. Our newly generated data suggest that dogs were part of a suite of animal introductions beginning over a millennium ago that coincided with widespread landscape transformation and megafaunal extinction.Introduction Materials and Methods - Specimen and Site Selection - 14C and Stable Isotope Analyses - Data Analysis Results - Chronological Data - Stable Isotope Data Discussio

The Geology of Inferno Chasm, Idaho: a Terrestrial Analog for Lunar Rilles?

Lunar sinuous rilles are thought to have formed by thermal erosion, mechanical erosion, construction, or a combination of these processes via emplacement by lava tubes or lava channels. The investigation of Hadley Rille by Apollo 15 provided the first field observations of a rille, but remote sensing observations remain our primary method for studying these features. Terrestrial volcanic features with similar morphologies to lunar rilles can provide insight into their formation on the Moon

The Exomars Climate Sounder (EMCS) Investigation

The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA. EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind