Mars Express measurements of surface albedo changes over 2004 - 2010

The pervasive Mars dust is continually transported between the surface and the atmosphere. When on the surface, dust increases the albedo of darker underlying rocks and regolith, which modifies climate energy balance and must be quantified. Remote observation of surface albedo absolute value and albedo change is however complicated by dust itself when lifted in the atmosphere. Here we present a method to calculate and map the bolometric solar hemispherical albedo of the Martian surface using the 2004 - 2010 OMEGA imaging spectrometer dataset. This method takes into account aerosols radiative transfer, surface photometry, and instrumental issues such as registration differences between visible and near-IR detectors. Resulting albedos are on average 17% higher than previous estimates for bright surfaces while similar for dark surfaces. We observed that surface albedo changes occur mostly during the storm season due to isolated events. The main variations are observed during the 2007 global dust storm and during the following year. A wide variety of change timings are detected such as dust deposited and then cleaned over a Martian year, areas modified only during successive global dust storms, and perennial changes over decades. Both similarities and differences with previous global dust storms are observed. While an optically thin layer of bright dust is involved in most changes, this coating turns out to be sufficient to mask underlying mineralogical near-IR spectral signatures. Overall, changes result from apparently erratic events; however, a cyclic evolution emerges for some (but not all) areas over long timescales

Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia

A project of mapping ice-related landforms was undertaken to understand the role of sub-surface ice in the northern plains. This work is the first continuous regional mapping from CTX (“ConTeXt Camera”, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centred on the 170° West line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35° N and 78° N and have a positive spatial correlation with inferred ice stability based on thermal modelling, neutron spectroscopy and radar data. The degradational features into the LDM (Latitude Dependent Mantle) include pits, scallops and 100 m polygons and provide supporting evidence for sub-surface ice and volatile loss between 35-70° N in Arcadia with the mantle between 70-78° N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more wide-spread near-surface sub-surface ice, and thus was more susceptible to pitting, or that the ice was less well-buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65-70° N could indicate a relatively young age (~1Ma), however this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape

Trip durations of daily and seasonal foraging activities in Mischocyttarus nomurae (Richards) (Hymenoptera, Vespidae)

The study of foraging activity in wasps is important to understand the social organization and its evolutionary success. We examined aspects of the daily and seasonal foraging activities of Mischocyttarus nomurae Richards wasps, in terms of individual trip durationin the collection of different resources. The study was undertaken in two areas in the municipality of Rio de Contas, Bahia State, Brazil. Observations were done for 10 colonies of M. nomurae in their post-emergence phase under natural conditions, five during the rainy period and five during the dry period. The amplitudes of the activity hours were similar between the two periods. The foraging efficiency index was higher (80.56%) during the rainy period than during the dry period (74.42%), with greater percentages of returns with all foraged items (with the exception of prey captures). Temperature influenced positively and significantly the number of trips performed during the rainy period, while temperature and luminosity positively influenced the number of trips performed during the dry period. The mean duration of trips for diferente resources were greater during the dry period (with the exception of wood pulp), although those differences were not statistically significant. Wasps spent the most part of their time nectar (83.60 min), followed by prey (21.06 min), and wood Pulp (1.40 min). We observed that 52.56% of the foraging individuals of M. nomurae collected only a single resource type

Nesting Behaviour of a Neotropical Social Wasp Mischocyttarus saussurei Zikán, 1949 (Hymenoptera, Vespidae)

Mischocyttarus saussurei nests show a curious architectural pattern which could be related to colony camouflage. Since information on that species is scarce in literature, this study aimed to record ecological data on M. saussurei, as well as morphometric data on its nests. Data was collected at the Parque Estadual do Ibitipoca state park and at the municipalities of Barroso and Inconfidentes, Minas Gerais state, Southeastern Brazil. Seven colonies were located, exclusively in conserved environments. Five nests were dissected for morphometric analysis and for the assessment of the vegetal matter incorporated to comb walls. Nests showed comb cells opening towards the substrate and covered by vegetal layers, in which three families of mosses and three of liverworts could be identified. We deduct that the nests’ morphometry and the incorporation of vegetal layers to the combs are related to the camouflaging of colonies amidst their substrate

Present-day Mars' seismicity predicted from 3-D thermal evolution models of interior dynamics

©2018. American Geophysical UnionThe Interior Exploration using Seismic Investigations, Geodesy and Heat Transport mission, to be launched in 2018, will perform a comprehensive geophysical investigation of Mars in situ. The Seismic Experiment for Interior Structure package aims to detect global and regional seismic events and in turn offer constraints on core size, crustal thickness, and core, mantle, and crustal composition. In this study, we estimate the present‐day amount and distribution of seismicity using 3‐D numerical thermal evolution models of Mars, taking into account contributions from convective stresses as well as from stresses associated with cooling and planetary contraction. Defining the seismogenic lithosphere by an isotherm and assuming two end‐member cases of 573 K and the 1073 K, we determine the seismogenic lithosphere thickness. Assuming a seismic efficiency between 0.025 and 1, this thickness is used to estimate the total annual seismic moment budget, and our models show values between 5.7 × 1016 and 3.9 × 1019 Nm

SAND DEPOSIT MAPPING AND AEOLIAN MORPHOLOGIES AS CLUES FOR IDENTIFYING ORIGINS OF DARK SAND IN AEOLIS DORSA, MARS

Dark sand deposits occur at all latitudes on the Martian surface. Sand sources in some regions have been inferred via paleo-wind indicator analyses, sand and source mineralogy comparisons, and climate modeling. However, all known sources are sedimentary, leaving outstanding the question of primary igneous origin(s) of these dark sand deposits. One hypothesis addressing this question is that volcaniclastic deposits are a primary origin of Martian sand. Terrestrial analogs of volcaniclastic units sourcing sand support this hypothesis. However, sand generation has yet to be observed or inferred from any such Martian deposit. This thesis tests this hypothesis via a case study in Aeolis Dorsa, Mars, a locality where sand overlies bedrock consisting of a hypothesized volcaniclastic deposit, the Medusae Fossae Formation (MFF). In addition to the MFF, additional potential external sand sources exist: Elysium Mons, the Cerberus Plains lavas, and the Southern Highlands.To identify likely sand source(s) in Aeolis Dorsa, sand deposits were mapped to address geospatial sand distribution, scour mark orientations were mapped and analyzed to reveal dominant paleo-wind directions, and instances of apparent erosion of bedrock to dark sediment were recorded. Hierarchical clustering analysis of sand distribution revealed preferential sand deposition on the peripheries of the MFF and in the southern depression (where bedrock may be remnant southern highlands material). Hierarchical cluster analysis of scour mark distribution revealed spatial groups of scour marks with consistent paleo-wind directions within groups. Such paleo-wind directions provide no evidence for long-distance sand transport from potential external source regions, but instead provide support for paleo-winds controlled by local topography. Apparent erosion of bedrock to dark sediments occurs in both the MFF (in ~20 localities) and in the southern depression (in over 100 localities), suggesting that both the MFF and bedrock in the southern depression have the potential to generate dark sand. The implication that the MFF has the potential to produce dark sand raises two important possibilities: first, that elsewhere along the Martian equator the MFF may have produced dark sand, and second, that other friable layered deposits (of which the MFF is one) may also serve as sources of Martian sand

Large-scale volcanism on the terrestrial planets

Evidence for mafic volcanism has been found on each planet in the inner Solar System. Lava flows on these planets range in size from 10s to 1000s of kilometers in extent. I investigated large-scale lava flows on Mercury, Earth, and Mars throughout the chapters in this dissertation. Each of these lava flows provides an avenue to study the emplacement and evolution of lava on various planets and under differing conditions, the factors that affect their overall extent, and potential source areas. Chapter One investigates large-scale lava flows in the Cerberus region on Mars, specifically to understand their emplacement history, material properties, and possible magma sources. Mapping and crater counting are used to investigate these flows. The derived absolute age estimates suggest an anomalous trend of decreasing ages with increasing distance from the flow source. Through pi-group scaling, changes to the material properties of the lavas during emplacement are identified as the cause for this decreasing age trend and are attributed to increased strength, and decreased porosity, of the lava. These newly derived absolute age estimates are also used to infer the source of the magma feeding these young and extensive lava flows originated below the Cerberus region. Chapter Two focuses on long and areally extensive lava flows on Earth and Mars, in order to determine the effect of viscosity on the emplacement of 1000+ km flows. In particular, low viscosity lavas are expected to generate such large lava flows. The terrestrial and martian lava flows are interpreted to have been emplaced rapidly, with their final extents limited by the total erupted volume of lava. Through computer modeling, simulations are performed to determine the viscosity values responsible for the observed lava flow extents. The results of this work support low bulk viscosities that correspond to a basaltic composition produce the best reproductions of the martian flows. Chapter Three investigates volcanism on Mercury, which hosts broad smooth plains in three locales, which have varying interpretations for their emplacement, though volcanic processes are favored. The smooth plains units located in the annulus surrounding the Caloris impact basin contain intermingled high-reflectance red and low-reflectance blue plains. Mapping, crater counting, and spectral analyses are used to suggest the emplacement mechanism for these smooth plains. The results of this work support a volcanic origin, though impact related processes cannot be discounted

Methane Seepage on Mars: Where to Look and Why

Methane on Mars is a topic of special interest because of its potential association with microbial life. The variable detections of methane by the Curiosity rover, orbiters, and terrestrial telescopes, coupled with methane's short lifetime in the martian atmosphere, may imply an active gas source in the planet's subsurface, with migration and surface emission processes similar to those known on Earth as “gas seepage.” Here, we review the variety of subsurface processes that could result in methane seepage on Mars. Such methane could originate from abiotic chemical reactions, thermogenic alteration of abiotic or biotic organic matter, and ancient or extant microbial metabolism. These processes can occur over a wide range of temperatures, in both sedimentary and igneous rocks, and together they enhance the possibility that significant amounts of methane could have formed on early Mars. Methane seepage to the surface would occur preferentially along faults and fractures, through focused macro-seeps and/or diffuse microseepage exhalations. Our work highlights the types of features on Mars that could be associated with methane release, including mud-volcano-like mounds in Acidalia or Utopia; proposed ancient springs in Gusev Crater, Arabia Terra, and Valles Marineris; and rims of large impact craters. These could have been locations of past macro-seeps and may still emit methane today. Microseepage could occur through faults along the dichotomy or fractures such as those at Nili Fossae, Cerberus Fossae, the Argyre impact, and those produced in serpentinized rocks. Martian microseepage would be extremely difficult to detect remotely yet could constitute a significant gas source. We emphasize that the most definitive detection of methane seepage from different release candidates would be best provided by measurements performed in the ground or at the ground-atmosphere interface by landers or rovers and that the technology for such detection is currently available

High-Power Laser Systems for Driving and Probing High Energy Density Physics Experiments

This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.Open Acces

Studies of Glacial and Periglacial Environments on Mars

This thesis presents the development and application of a grid-based mapping approach that provides an efficient solution to the problems of mapping small landforms over large areas. The approach allows the cataloguing of landform classes, of multiple sizes, efficiently in a single pass. The speed at which the data could be recorded allowed for the first continuous, full resolution mapping of decametre-scale landforms in CTX images on hemispherical-scale maps. The discrete, tabular nature of grid mapping opens up the possibility of citizen science meaning the grid mapping approach could have considerable future use and impact. The main scientific goal of this thesis was to determine the distribution and origins of ice-related landforms in the northern plains, and provide insight as to whether these landforms are related to distinct geological or geomorphological units. To accomplish this, I used the grid mapping approach to explore a large tract covering the Arcadia Planitia region of the northern plains of Mars. In addition, I was able to compare these results to two other sister studies performed in the Utopia and Acidalia Planitia regions of Mars. To explore possible sources of ice I performed a detailed study of the Rahway Vallis system. This found an assemblage of terraces, channels and sinuous ridges in Rahway Vallis that are topographically and morphologically consistent with either a draining lake, or a melting, once liquid, ice-body, and is indicative of a flow of volatiles into the northern plains and large scale shifts in ground ice stability. Overall, this thesis demonstrates the dominant effects of the deposition and sublimation of the Latitude Dependent Mantle in shaping recent landscapes on the northern plains of Mars. There was little evidence for thaw-related landforms, and evidence for a fluvial origin for ice in the near surface is circumstantial, or has been erased or covered