Materials investigation and tests for the development of space compatible electrical connectors, phase 1 Final report, 1 Jun. - 30 Nov. 1970

Digital pulse optimization for space compatible electric connector

Martian Araneiforms: A Review

Araneiforms are enigmatic dendritic negative topography features native to Mars. Found across a variety of substrates and exhibiting a range of scales, morphologies, and activity level, they are hypothesized to form via insolation-induced basal sublimation of seasonal CO2 ice. With no direct Earth analog, araneiforms are an example of how our understanding of extant surface features can evolve through a multipronged approach using high resolution change-detection imaging, conceptual and numerical modeling, and analog laboratory work. This review offers a primer on the current state of knowledge of Martian araneiforms. We outline the development of their driving conceptual hypothesis and the various methodologies used to study their formation. We furthermore present open questions and identify future laboratory and modeling work and mission objectives that may address these questions. Finally, this review highlights how the study of araneiforms may be used as a proxy for local conditions and perhaps even past seasonal dynamics on Mars. We also reflect on the lessons learnt from studying them and opportunities for comparative planetology that can be harnessed in understanding unusual features on icy worlds that have no Earth analog

Active fixturing: literature review and future research directions

Fixtures are used to fixate, position and support workpieces and represent a crucial tool in manufacturing. Their performance determines the result of the whole manufacturing process of a product. There is a vast amount of research done on automatic fixture layout synthesis and optimisation and fixture design verification. Most of this work considers fixture mechanics to be static and the fixture elements to be passive. However, a new generation of fixtures has emerged that has actuated fixture elements for active control of the part–fixture system during manufacturing operations to increase the end product quality. This paper analyses the latest studies in the field of active fixture design and its relationship with flexible and reconfigurable fixturing systems. First, a brief introduction is given on the importance of research of fixturing systems. Secondly, the basics of workholding and fixture design are visited, after which the state-of-the-art in active fixturing and related concepts is presented. Fourthly, part–fixture dynamics and design strategies which take these into account are discussed. Fifthly, the control strategies used in active fixturing systems are examined. Finally, some final conclusions and prospective future research directions are presented

Possible ice-wedge polygonisation in Utopia Planitia, Mars and its latitudinal gradient of distribution

International audienceOn Earth, ice complexes are commonplace landscapes amidst the continuous permafrost of coastal or near-coastal plains in the Arctic. Formed by the freeze-thaw cycling of water, ice complex features include: hummocky (thermokarstic) terrain, inflated or deflated by the presence of absence of excess ice; thermokarst lakes (i.e. excess ice that has thawed and pooled); alases (i.e. thermokarst basins emptied of water); and, ice-wedge polygons, often characterized by raised (ice-aggraded) or lowered (ice-degraded) margins relative to the polygon centres.The origin and development of these complexes is rooted in inter-or intra-glacial pulses of temperature that engender widespread thaw, meltwater distribution and migration through the soil column (sometimes to decametres of depth), and the freeze-thaw cycling of the meltwater.The possible existence of ice-rich terrain on Mars revised by the freeze-thaw cycling of water dates back to the grainy Mariner-mission photographs of the 1960s and 1970s. However, absent of regolith samples from areas where this terrain is hypothesised, attempts to validate the ice-rich hypothesis often have ended abruptly, either with spectrometric inferences of water-equivalent hydrogen to one metre or so of depth or with “looks-like”, therefore “must-be” analogies derived of Earth-based ice-complexes.In the case of small-sized Martian polygons with low- and high-centres, the similarities of form between ice and sand-wedge polygons on Earth has equivocated the reach of ice-wedge hypotheses on Mars.Here, we show that:1) The plains' terrain of our study region in Utopia Planitia (40-50o N; 100-125o E) displays a statistically-significant and positive (linear) correlation between the ratio of low-centred to high-centred polygons (lcps vs hcps) and a poleward latitude of distribution.2) This linear correlation would be expected, in as much as ground-ice stability increases with latitude, were the shoulders of higher-latitude lcps underlain by (aggraded) ice-wedges and those of lower-latitude hcps underlain by (degraded) ice-wedges.3) The change of polygon morphology with latitude would not be expected were the lcps and hcps underlain by sand wedges, in as much as ground-ice stability is unrelated to their aggradation or degradation.4) Crater counts of the polygonised terrain indicate that it is less youthful than previous studies have suggested, perhaps by an order of magnitude. This attenuates the possible inconsistency between the more temperate boundary-conditions required by the formation of ice-wedge polygons and the current constraints of extreme aridity, low temperatures and low atmospheric pressur

POSSIBLE ICE-WEDGE POLYGONS IN UTOPIA PLANITIA, MARS, AND THEIR POLEWARD LATITUDINAL GRADIENT

International audienceIntroduction: Here, we describe and evaluate: a) the presence and distribution in Utopia Planitia (UP), Mars (40-50 o N, 110-124 o E), of small-sized polygons , (10-25 m in diameter), with low centres (lcps) or high centres (hcps) relative to their margins; b) the spatial , perhaps periglacial, association of these polygons and thermokarst-like depressions or basins; and, c) statistical data that support the hypothesis that ice-wedges underlie lcp/hcp margins. LCPs/HCPs on Earth: Geographically-expansive complexes of ice-wedge polygons (be they lcps or hcps), thermokarst, thermokarst lakes and alases, i.e. thermokarst depressions of basins absent of water, are commonplace in the Tuktoyaktuk Coastlands (TC) of northern Canada and the Yamal peninsula (YP) of eastern Russia [1-4]. In these and similar arctic-regions sur-face/near-surface water is abundant, freeze-thaw cycling is ubiquitous and the permafrost is ice-rich to depth [1-4, Fig. 1]. Ice-rich permafrost comprises excess ice: "the volume of ice in the ground which exceeds the total pore-volume that the ground would have under natural unfro-zen-conditions" [5]. Ice lenses, veins, wedges or larger masses of consolidated ice are typical examples of excess ice [5]. Thermokarst comprises excess ice. This makes it particularly sensitive to volumetric inflation as ice ag-grades, when mean temperatures remain stable or fall, or volumetric deflation as ice degrades, when mean temperatures rise and meltwater is evacuated by drainage or evaporation from the thaw zone. Fig. 1. Near-surface ice and ice wedges at Peninsula Point, SW of Tuktoyaktuk: (a-c) recessional terraces resulting from thermal destabilisation of coastline. (d) Surface depressions above degrading ice-wedges; massive-ice exposures cen-tre/centre left. Image credit, R. Soare. Spatially-associated assemblages of lcps and hcps also are geological markers of climate change. Stable or falling mean-temperatures engender ice-wedge aggrad-ation and the uplift of polygon margins. Rising mean-temperatures induce ice-wedge degradation and the collapse of uplifted margins, giving these polygons a distinctly high-centred appearance [1-7]. Sand or soil-sand admixtures also are associated with polygon-margin fills and may generate individual fields of lcps and hcps [e.g 7]. The closely-set spatial association of lcps and hcps in wet periglacial-landscapes on Earth, however, often is indicative of ice-wedge polygons, albeit in disparate phases of evolution. Fig. 2. Possible thermokarst/polygon complex in UP. LCPs adjacent to scarp on left side of image (black arrow); HCPs above and to the right (white arrow) (HiRISE ESP_026094_2250; 44.657 o N, 111.415 o E). North is up. Image credit, NASA/JPL/Univ. of Arizona. LCPs/HCPs in UP: The presence of lcps/hcps at the mid-latitudes of both Martian hemispheres, as well as the spatial and possibly periglacial-association of these polygons with alas-like landforms (Fig. 2), are noted in the literature [e.g. 8-12]. On the other hand, questions concerning the range, density or sparcity of lcp and/or hcp distribution in UP (Figs. 3-4) have not been explored fully. Fig. 3. Dense distribution of lcps near crater central-peak (HiRISE ESP_011523_2235; 42.953 o N, 115.670 o E). North is up. Image credit, NASA/JPL/ University of Arizona. One of the keynotes of our study is evaluating the ratio of lcp/hcp distribution by latitude. If a statistical analysis of this distribution shows that the presence of 50 m 100 m 50 m 2121.pdf 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132

Glacial deposits, remnants, and landscapes on Amazonian Mars:Using setting, structure, and stratigraphy to understand ice evolution and climate history

Significant amounts of ice are located on the surface and in the subsurface of Mars. These polar and non-polar deposits are primarily water ice but, at the poles, carbon dioxide (CO2) ice exists on the surface where it exchanges seasonally with the atmosphere, while buried CO2 ice deposits have also been found. Analogous to Earth, Martian glacial ice deposits, as well as glacial remnants and landscapes from past glaciations, record how volatiles and components in the atmosphere, surface, and subsurface have interacted over time. Surface and subsurface expressions of past glaciations and deglaciations are critical to our understanding of the past climate on Mars, which is one of the highest priority goals in Mars science.Mars’ ice and climate record is constrained by the glacial record that extends over the last ~1 billion years of the Amazonian Period. Imagery, elevation models, radar, and spectral data have revealed aspects of the setting and structure of glacial deposits, glacial remnants, and geomorphological signatures of receded glaciers. The stratigraphy of these landforms has the capacity to provide the most highly resolved record available of past climate conditions on Mars. We discuss three key questions, leading with: what history of the Late Amazonian Epoch climate is recorded in the Polar Layered Deposits? Then, what sequence of glaciation and deglaciation developed non-polar glacial remnants? Related to interpreting glacial landscapes, we discuss: how widespread were past warm-based conditions among extant Amazonian-aged buried glaciers? Addressing these questions is necessary as part of continued efforts to advance our understanding of ice and climate histories on Mars