A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

Ultraviolet radiation on the surface of Mars and the Beagle 2 UV sensor

In this paper a simple radiative transfer model for the transmission of UV to the surface of Mars is presented for the wavelength range 190–410 nm. The model accounts for the variable presence of dust aerosols in the martian atmosphere and its effects upon direct and diffuse irradiance. A range of situations is presented, including variations in orbital position, latitude, time of day, dust loading and ozone presence. High dust loading is seen to have an inverting effect on direct/diffuse transmission ratios, with a significant amount of illumination still being provided even at high optical depths typical of dust storms. Diffuse transmission is also observed as the primary component close to sunrise and sunset as expected. An ozone absorption feature is seen for high-latitude northern winter cases, offering limited shielding centred around 250 nm in the biologically damaging region of the UV spectrum. The use of the model is then discussed in the role of designing and developing the Beagle 2 UV sensor, an instrument to measure the surface UV flux between 200 and 400 nm and set to land on the surface of Mars in 2003. The model is used to determine flux levels and spectral regions of particular interest, leading to a detailed instrument design and specification

Faunal use of bluegum (Eucalyptus globulus) plantations in southwestern Australia

We examined the faunal use of Eucalyptus globulus plantations in southern Western Australia, and compared use of remnant vegetation, agricultural land and plantations in different positions relative to large tracts of remnant vegetation. In general, faunal use of plantations is less than in comparison with adjacent remnant vegetation, but more than in open pasture. For all faunal groups there were almost twice as many species recorded in the native vegetation than in any site in the plantations or on agricultural land and they were in greater abundance. Faunal use of plantation edges and interiors did not show consistent patterns. Generally, edges next to remnants were most frequently used, but individual species showed a wide range of patterns of use across the various habitat types studied. More species of bird identified as being “at risk” were found in plantation edges than in interiors. Adjacency to remnant vegetation increased plantation use by some species, but the overall differences between isolated plantations and those adjacent to remnant vegetation were relatively small. We conclude that plantations provide some value in terms of habitat for some species, including some of conservation concern, but that this value is limited by the lack of habitat complexity in the intensively-managed plantations

Intrinsic passive stiffness of 2 constructs of varus proximal femoral osteotomy: External fixator or blade plate

Background: Despite the published clinical evidence of the implementation of external fixation of proximal femoral osteotomies, there is lack of specific laboratory justification. Methods: Two groups of 5 adult composite femur constructs of varus proximal femoral osteotomy were tested under incremental and cyclical loading of up to 600N along the mechanical axis. Five were fixed with a blade plate and another 5 with a monolateral external fixator. Load versus displacement curves were produced, and passive stiffness of all constructs was calculated. The described loading regime aimed to simulate the initial postoperative state and provide data for the assessment of vertical intrinsic passive stiffness in partial weight-bearing conditions. Results: Although the blade plate constructs showed higher average stiffness, this was not statistically significant [F(1,8) = 1.712, P = 0.23]. No construct failed. No failure or plastic deformation was observed under the described loading regime. Conclusions: Vertical intrinsic passive stiffness in partial weight- bearing conditions during the initial postoperative period can be considered satisfactory subsequent to unilateral external fixation of a varus intertrochanteric osteotomy. Clinical Relevance: The results support the hypothesis that external fixation is a biomechanically sound alternative to internal fixation of varus intertrochanteric osteotomies, in selected patients. Copyright © 2010 by Lippincott Williams & Wilkins

Age-of-acquisition Effects in Novel Picture Naming: a Laboratory Analogue

Age-of-acquisition (AoA) effects are such that early-acquired items are more quickly recognized and produced than later acquired items. In this laboratory analogue, participants were trained to name a group of Greeble pictures with a novel nonsense name. We manipulated order of acquisition of the stimuli: Half of the stimuli were presented from the onset of training (early acquired) whilst the other half were introduced later in the training schedule (late acquired). At test, when early and late stimuli had equal cumulative frequency, early stimuli were named significantly faster than late items. In a second test, it was also found that visual duration thresholds were significantly smaller for the early items when participants were asked to name the critical items. These findings support the notion that order-of-acquisition effects can be manifest over a short time span in the laboratory, and that the effect of order of acquisition is distinct from mere frequency of exposure. The findings are consistent with the idea that AoA effects occurring over a large temporal scale may be a special case of more general order-of-acquisition effects, and both may be a general property of learning mechanisms