Venus: The Atmosphere,Climate, Surface,Interior and Near-Space Environment of an Earth-Like Planet

This is a review of current knowledge about Earth’s nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a summary of previous Venus observations. The scientific discussions which follow are divided into three main sections: on the surface and interior; the atmosphere and climate; and the thermosphere, exosphere and magnetosphere. These reports are intended to provide an overview for the general reader, and also an introduction to the more detailed topical surveys in the following articles in this issue, where full references to original material may be found.     

月球阿波罗盆地区域月壳结构及光谱特征

位于月球南极–艾肯(South Pole-Aitken Basin,SPA)盆地内的前酒海纪阿波罗盆地跨越了SPA盆地的瞬时穴和盆缘。SPA盆地是已确认的月球上最大最古老的撞击盆地,因此阿波罗盆地对于认识月球的内部结构和成分、区域地质作用和演化历史具有不可替代的作用。阿波罗盆地区域月壳具有很强的不对称性,靠近SPA盆缘处厚而靠近SPA盆地中心处薄,其峰环内部拥有最薄的月壳厚度。阿波罗盆地区域具有不同的光谱吸收特征。在阿波罗盆地外,靠近SPA盆缘具有更多Mg辉石吸收特征的短波吸收,而靠近SPA中心区域具有更多高Ca辉石吸收特征的长波吸收。盆地内部不同地质单元的光谱吸收特征也有差异,月海为高Ca辉石的吸收特征,峰环为Mg辉石的短波长吸收。阿波罗盆地具有最薄的月壳厚度、高程差达8 km的地层剖面、位于月球背面SPA盆地内的月海、发育充分的中央峰环,其独特性使它成为最有价值的采样点。     

Advances in Plasmaspheric Wave Research with CLUSTER and IMAGE Observations

This paper highlights significant advances in plasmaspheric wave research with Cluster and Image observations. This leap forward was made possible thanks to the new observational capabilities of these space missions. On one hand, the multipoint view of the four Cluster satellites, a unique capability, has enabled the estimation of wave characteristics impossible to derive from single spacecraft measurements. On the other hand, the Image experiments have enabled to relate large-scale plasmaspheric density structures with wave observations and provide radio soundings of the plasmasphere with unprecedented details. After a brief introduction on Cluster and Image wave instrumentation, a series of sections, each dedicated to a specific type of plasmaspheric wave, put into context the recent advances obtained by these two revolutionary missions.     

Effects of heavy particle irradiation and diet on object recognition memory in rats

On long-duration missions to other planets astronauts will be exposed to types and doses of radiation that are not experienced in low earth orbit. Previous research using a ground-based model for exposure to cosmic rays has shown that exposure to heavy particles, such as ⁵⁶Fe, disrupts spatial learning and memory measured using the Morris water maze. Maintaining rats on diets containing antioxidant phytochemicals for 2 weeks prior to irradiation ameliorated this deficit. The present experiments were designed to determine: (1) the generality of the particle-induced disruption of memory by examining the effects of exposure to ⁵⁶Fe particles on object recognition memory; and (2) whether maintaining rats on these antioxidant diets for 2 weeks prior to irradiation would also ameliorate any potential deficit. The results showed that exposure to low doses of ⁵⁶Fe particles does disrupt recognition memory and that maintaining rats on antioxidant diets containing blueberry and strawberry extract for only 2 weeks was effective in ameliorating the disruptive effects of irradiation. The results are discussed in terms of the mechanisms by which exposure to these particles may produce effects on neurocognitive performance.     

The Science Case for STEP

The Satellite Test of the Equivalence Principle (STEP) will advance experimental limits on violations of Einstein’s Equivalence Principle (EP) from their present sensitivity of 2 parts in 10¹³${10}^{13}$ to 1 part in 10¹⁸${10}^{18}$ through multiple comparison of the motions of four pairs of test masses of different compositions in an earth-orbiting drag-free satellite. Dimensional arguments suggest that violations, if they exist, should be found in this range, and they are also suggested by leading attempts at unified theories of fundamental interactions (e.g., string theory) and cosmological theories involving dynamical dark energy. Discovery of a violation would constitute the discovery of a new force of nature and provide a critical signpost toward unification. A null result would be just as profound, because it would close off any possibility of a natural-strength coupling between standard-model fields and the new light degrees of freedom that such theories generically predict (e.g., dilatons, moduli, quintessence). STEP should thus be seen as the intermediate-scale component of an integrated strategy for fundamental physics experiments that already includes particle accelerators (at the smallest scales) and supernova probes (at the largest). The former may find indirect evidence for new fields via their missing-energy signatures, and the latter may produce direct evidence through changes in cosmological equation of state—but only a gravitational experiment like STEP can go further and reveal how or whether such a field couples to the rest of the standard model. It is at once complementary to the other two kinds of tests, and a uniquely powerful probe of fundamental physics in its own right.     

Application of the Mars Organic Analyzer to nucleobase and amine biomarker detection

The Mars Organic Analyzer (MOA), a portable microfabricated capillary electrophoresis instrument being developed for planetary exploration, is used to analyze a wide variety of fluorescamine-labeled amine-containing biomarker compounds, including amino acids, mono and diaminoalkanes, amino sugars, nucleobases, and nucleobase degradation products. The nucleobases cytosine and adenine, which contain an exocyclic primary amine, were effectively labeled, separated, and detected at concentrations <500 nM. To test the general applicability of the MOA for biomarker detection, amino acids and mono- and diamines were extracted from bacterial cells using both hydrolysis and sublimation followed by analysis. The extrapolated limit of detection provided by the valine biomarker was approximately 4 x 10(3) cells per sample. Products of an NH(4)CN polymerization that simulate a prebiotic synthesis were also successfully isolated via sublimation and analyzed. Adenine and alanine/serine were detected with no additional sample cleanup at 120 +/- 13 microM and 4.1 +/- 1 microM, respectively, corresponding to a reaction yield of 0.04% and 0.0003%, respectively. This study demonstrates that the MOA provides sensitive detection and analysis of low levels of a wide variety of amine-containing organic compounds from both biological and abiotic sources.     

Impact of Jason-2/T2L2 Ultra-Stable-Oscillator Frequency Model on DORIS stations coordinates and Earth Orientation Parameters

Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) is a tracking technique based on a one-way ground to space Doppler link. For Low Earth Orbit (LEO) satellites, DORIS shows a robust capability in terms of data coverage and availability, due to a wide and well-distributed ground network, where data are made available by the International Doris Service (IDS). However, systematic errors remain in the DORIS data, such as instabilities of the on-board clock due to radiation encountered in space, which limit the accurate determination of station positions.The DORIS on-board clock frequency stability is degraded by the increased radiation found in the region of the South Atlantic Anomaly (SAA) and has been shown to degrade station position estimation. This paper introduces a new model correction to the DORIS data for the frequency of the Jason-2 Ultra Stable Oscillator (USO), derived from the Time Transfer by Laser Link (T2L2) experiment (Belli and Exertier, 2018). We show that a multi-satellite DORIS solution including this T2L2-corrected data applied to the frequency modelling for The DORIS data, improves the estimation of station coordinates. We show the tie residuals with respect to collocated GPS stations are improved by several millimeters. We also demonstrate that the 117-day (Jason-2) draconitic signal in the geophysical parameters is reduced, implying that the origin of this signal is not just solar radiation pressure mis-modeling, but also radiation-induced clock perturbations on the Jason-2 DORIS Ultra-Stable-Oscillator (USO). Finally we demonstrate through comparisons with the International Earth Rotations and Reference Systems Service (IERS) C04 series for Earth Orientation Parameters (EOP), that the estimation of EOP is improved in both a Jason-2 DORIS-only and a multi-satellite DORIS solution for EOP.     

The Student Dust Counter on the New Horizons Mission

The Student Dust Counter (SDC) experiment of the New Horizons Mission is an impact dust detector to map the spatial and size distribution of dust along the trajectory of the spacecraft across the solar system. The sensors are thin, permanently polarized polyvinylidene fluoride (PVDF) plastic films that generate an electrical signal when dust particles penetrate their surface. SDC is capable of detecting particles with masses m>10^?12 g, and it has a total sensitive surface area of about 0.1 m², pointing most of the time close to the ram direction of the spacecraft. SDC is part of the Education and Public Outreach (EPO) effort of this mission. The instrument was designed, built, tested, integrated, and now is operated by students.     

Interactivity in map learning: The effect of cognitive load

The hypothesis that active learning is beneficial relative to passive observation was assessed in the context of spatial knowledge derived from maps. Active and passive participants studied a map either while performing a simultaneous spatial tapping task (high cognitive load) or in the absence of this task (low cognitive load). Active participants controlled how the map was learned, with passive participants observing map learning without exercising control. Spatial recall was assessed in two tests, directional judgements and map drawing. Map drawing and directional judgments showed a similar pattern of results, with performance detrimentally affected by a high load for active participants, but not for passive participants. The results indicate that activity and cognitive load interact, suggesting that active learning can be detrimental to spatial learning in cognitively demanding tasks.     

Planned Products of the Mars Structure Service for the InSight Mission to Mars

Space Science Reviews - The InSight lander will deliver geophysical instruments to Mars in 2018, including seismometers installed directly on the surface (Seismic Experiment for Interior Structure,...