Laboratory capture, isolation and analysis of microparticles in aerogel: Preparation for the return of Stardust

We present observations from the laboratory capture of particles in aerogel. The paper focuses on a possible extraction technique and the bulk mineral characterization of the captured material using non-destructive analytical techniques

Distinctive impact craters are formed by organic rich cometary dust grains

Introduction: Preliminary Examination (PE) of the Stardust cometary collector revealed many tracks in the silica aerogel and impact craters on aluminium (Al) foil, from which Wild 2 dust particle fluence and size distribution were determined. Laboratory light gas gun (LGG) shots provided impactor size calibrations. Analogue impacts of diverse mineral compositions and aggregate particles aided interpretation of dust composition and structure. We now describe our recent impact experiments on foil by organic materials, which reveal distinctive crater surface textures, and even preserved residue

Microcraters in aluminum foils exposed by Stardust

We will present preliminary results on the nature and size frequency distribution of microcraters that formed in aluminum foils during the flyby of comet Wild 2 by the Stardust spacecraft

Affordances and limitations of electronic storybooks for young children's emergent literacy

AbstractStories presented on phones, tablets and e-readers now offer an alternative to print books. The fundamental challenge has become to specify when and for whom the manner in which children retain information from stories has been changed by electronic storybooks, for better and for worse. We review the effects of digitized presentations of narratives that include oral text as well as multimedia information sources (e.g., animations and other visual and sound effects, background music, hotspots, games, dictionaries) on children's emergent literacy. Research on preschool and kindergarten children has revealed both positive and negative effects of electronic stories conditional upon whether materials are consistent with the way that the human information processing system works. Adding certain information to electronic storybooks can facilitate multimedia learning, especially in children at-risk for language or reading difficulty. Animated pictures, sometimes enriched with music and sound, that match the simultaneously presented story text, can help integrate nonverbal information and language and thus promote storage of those in memory. On the other hand, stories enhanced with hypermedia interactive features like games and “hotspots” may lead to poor performance on tests of vocabulary and story comprehension. Using those features necessitates task switching, and like multitasking in general, seems to cause cognitive overload. However, in accordance with differential susceptibility theory, well-designed technology-enhanced books may be particularly suited to improve learning conditions for vulnerable children and turn putative risk groups into successful learners. This new line of research may have far-reaching consequences for the use of technology-enhanced materials in education

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Modelling radially symmetric impact craters with Zernike polynomials

Crater morphology in a ductile target can reveal some properties of the impacting particle. Simple measurements alone, such as the crater depth and diameter are limited in potential because the complete morphology is not considered. Detailed shape measurements, made by comparing stereo Scanning Electron Micrographs, can be reduced to a parameter set based on an orthogonal expansion over a circular domain, allowing quantitative comparisons between craters that consider the complete morphology. Most high-velocity impact craters are circular (have a circular rim), enabling us to make a model using only the radially symmetric terms from the orthogonal functions set. Shape parameters can be plotted on a feature space diagram, where similar shaped craters form clusters which can be analysed statistically. The method has been applied to laboratory impacts using a two-stage light-gas gun to fire mineral grains at an aluminium alloy target and glass beads over the velocity range 1–6 kms−1. The minerals kamacite and enstatite can be distinguished from crater morphology by this method and we have shown that the shape of impact craters change over the velocity range 1–6 kms−1 as well as simply the depth to diameter ratio

MULPEX: A compact multi-layered polymer foil collector for micrometeoroids and orbital debris

Detailed studies of preserved hypervelocity impact residues on spacecraft multi-layer insulation foils have yielded important information about the flux of small particles from different sources in low-Earth orbit (LEO). We have extended our earlier research on impacts occurring in LEO to design and testing of a compact capture device. MUlti-Layer Polymer EXperiment (MULPEX) is simple, cheap to build, lightweight, of no power demand, easy to deploy, and optimised for the efficient collection of impact residue for analysis on return to Earth. The capture medium is a stack of very thin (8 and 40 mu m) polyimide foils, supported on polytetrafluoroethylene sheet frames, surrounded by a protective aluminium casing. The uppermost foil has a very thin metallic coating for thermal protection and resistance to atomic oxygen and ultra-violet exposure. The casing provides a simple detachable interface for deployment on the spacecraft, facing into the desired direction for particle collection. On return to the laboratory, the stacked foils are separated for examination in a variable pressure scanning electron microscope, without need for surface coating. Analysis of impact residue is performed using energy dispersive X-ray spectrometers. Our laboratory experiments, utilising buck-shot firings of analogues to micrometeoroids (35-38 mu m olivine) and space debris (4 mu m alumina and 1 mm stainless steel) in a light gas gun, have shown that impact residue is abundant within the foil layers, and preserves a record of the impacting particle, whether of micrometer or millimetre dimensions. Penetrations of the top foil are easily recognised, and act as a proxy for dimensions of the penetrating particle. Impact may cause disruption and melting, but some residue retains sufficient crystallographic structure to show clear Raman lines, diagnostic of the original mineral. (c) 2005 Published by Elsevier Ltd on behalf of COSPAR

The chemistry of micrometeoroid and space debris remnants captured on Hubble Space Telescope solar cells

Prior to the retrieval in 1993 from low Earth orbit (LEO), the "—V2" Solar Array wing of the Hubble Space Telescope was exposed to hypervelocity impacts (micrometre to millimetre scale) from both micrometeoroids and space debris. The initial survey of the damage (100–3500μm diameter sized craters) identified that micrometeoroid remnants dominated the flux in the 100–1000μm size regime, with debris dominating>1000μm. These residues were composed of remnants of silicate minerals, calcite, metal sulfides and metals that often appeared as complex poly-mineralic melts within melt pits. A further survey of 10–100μm diameter craters identified that the most common chemistry was space debris with the crossover from meteoroids to debris being at around 30μm DCO. Residues include remnants of specialised steels and paint fragments but the dominant type is aluminium and aluminium oxide, which are almost certainly remnants of solid rocket motor operations. It is found that the relative contribution of debris as a function of size, agrees remarkably with a prediction derived using flux data from Long Duration Exposure Facility and a meteoroid model