[1] The HiRISE camera features a 0.5 m diameter primary mirror, 12 m effective focal length, and a focal plane system that can acquire images containing up to 28 Gb (gigabits) of data in as little as 6 seconds. HiRISE will provide detailed images (0.25 to 1.3 m/pixel) covering ∼1% of the Martian surface during the 2-year Primary Science Phase (PSP) beginning November 2006. Most images will include color data covering 20% of the potential field of view. A top priority is to acquire ∼1000 stereo pairs and apply precision geometric corrections to enable topographic measurements to better than 25 cm vertical precision. We expect to return more than 12 Tb of HiRISE data during the 2-year PSP, and use pixel binning, conversion from 14 to 8 bit values, and a lossless compression system to increase coverage. HiRISE images are acquired via 14 CCD detectors, each with 2 output channels, and with multiple choices for pixel binning and number of Time Delay and Integration lines. HiRISE will support Mars exploration by locating and characterizing past, present, and future landing sites, unsuccessful landing sites, and past and potentially future rover traverses. We will investigate cratering, volcanism, tectonism, hydrology, sedimentary processes, stratigraphy, aeolian processes, mass wasting, landscape evolution, seasonal processes, climate change, spectrophotometry, glacial and periglacial processes, polar geology, and regolith properties. An Internet Web site (HiWeb) will enable anyone in the world to suggest HiRISE targets on Mars and to easily locate, view, and download HiRISE data products.

/pdf/mars-reconnaissance-orbiter-s-high-resolution-imaging-4bjw0ks5y9.pdf

Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE)

Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the "siderikian") is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet.

https://science.sciencemag.org/content/sci/312/5772/400.full.pdf

Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data

A natural polypeptide chain can fold into a native protein in microseconds, but predicting such stable three-dimensional structure from any given amino-acid sequence and first physical principles remains a formidable computational challenge. Aiming to recruit human visual and strategic powers to the task, Seth Cooper, David Baker and colleagues turned their 'Rosetta' structure-prediction algorithm into an online multiplayer game called Foldit, in which thousands of non-scientists competed and collaborated to produce a rich set of new algorithms and search strategies for protein structure refinement. The work shows that even computationally complex scientific problems can be effectively crowd-sourced using interactive multiplayer games. Predicting the structure of a folded protein from first principles for any given amino-acid sequence remains a formidable computational challenge. To recruit human abilities to the task, these authors turned their Rosetta structure prediction algorithm into an online multiplayer game in which thousands of non-scientists competed and collaborated to produce new algorithms and search strategies for protein structure refinement. This shows that computationally complex problems can be effectively 'crowd-sourced' through interactive multiplayer games. People exert large amounts of problem-solving effort playing computer games. Simple image- and text-recognition tasks have been successfully ‘crowd-sourced’ through games1,2,3, but it is not clear if more complex scientific problems can be solved with human-directed computing. Protein structure prediction is one such problem: locating the biologically relevant native conformation of a protein is a formidable computational challenge given the very large size of the search space. Here we describe Foldit, a multiplayer online game that engages non-scientists in solving hard prediction problems. Foldit players interact with protein structures using direct manipulation tools and user-friendly versions of algorithms from the Rosetta structure prediction methodology4, while they compete and collaborate to optimize the computed energy. We show that top-ranked Foldit players excel at solving challenging structure refinement problems in which substantial backbone rearrangements are necessary to achieve the burial of hydrophobic residues. Players working collaboratively develop a rich assortment of new strategies and algorithms; unlike computational approaches, they explore not only the conformational space but also the space of possible search strategies. The integration of human visual problem-solving and strategy development capabilities with traditional computational algorithms through interactive multiplayer games is a powerful new approach to solving computationally-limited scientific problems.

/pdf/predicting-protein-structures-with-a-multiplayer-online-game-3md0x4a9x0.pdf

Predicting protein structures with a multiplayer online game

Jupiter and Saturn formed in a few million years from a gas-dominated protoplanetary disk, and were susceptible to gas-driven migration of their orbits on timescales of only approximately 100,000 years. Hydrodynamic simulations show that these giant planets can undergo a two-stage, inward-then-outward, migration. The terrestrial planets finished accreting much later and their characteristics, including Mars' small mass, are best reproduced by starting from a planetesimal disk with an outer edge at about one astronomical unit from the Sun (1 AU is the Earth-Sun distance). Here we report simulations of the early Solar System that show how the inward migration of Jupiter to 1.5 AU, and its subsequent outward migration, lead to a planetesimal disk truncated at 1 AU; the terrestrial planets then form from this disk over the next 30-50 million years, with an Earth/Mars mass ratio consistent with observations. Scattering by Jupiter initially empties but then repopulates the asteroid belt, with inner-belt bodies originating between 1 and 3 AU and outer-belt bodies originating between and beyond the giant planets. This explains the significant compositional differences across the asteroid belt. The key aspect missing from previous models of terrestrial planet formation is the substantial radial migration of the giant planets, which suggests that their behaviour is more similar to that inferred for extrasolar planets than previously thought.

A low mass for Mars from Jupiter's early gas―driven migration

Results by Neukum et al. (2001) and Ivanov (2001) are combined with crater counts to estimate ages of Martian surfaces. These results are combined with studies of Martian meteorites (Nyquist et al., 2001) to establish a rough chronology of Martian history. High crater densities in some areas, together with the existence of a 4.5 Gyr rock from Mars (ALH84001), which was weathered at about 4.0 Gyr, affirm that some of the oldest surfaces involve primordial crustal materials, degraded by various processes including megaregolith formation and cementing of debris. Small craters have been lost by these processes, as shown by comparison with Phobos and with the production function, and by crater morphology distributions. Crater loss rates and survival lifetimes are estimated as a measure of average depositional/erosional rate of activity.

/pdf/cratering-chronology-and-the-evolution-of-mars-15gbue0bfh.pdf

Cratering Chronology and the Evolution of Mars

Observation of dust and debris in the near Earth environment is a field of great commercial and scientific interest, vital to maximising the operational and commercial life-cycle of satellites and reducing risk to increasing numbers of astronauts in Low Earth Orbit (LEO). To this end, monitoring and assessment of the flux of particles is of paramount importance to the space industry and wider socio-economic interests that depend upon data products/services from orbital infrastructure. We have designed a passive space dust detector to investigate the dust environment in LEO—the Orbital Dust Impact Experiment (ODIE). ODIE is designed for deployment in LEO for ∼1 year, whereupon it would be returned to Earth for analysis of impact features generated by dust particles. The design emphasises the ability to distinguish between the orbital debris (OD) relating to human space activity and the naturally occurring micrometeoroid (MM) population at millimetre to submillimetre scales. ODIE is comprised of multiple Kapton foils, which have shown great potential to effectively preserve details of the impacting particles’ size and chemistry, with residue chemistry being used to interpret an origin (OD vs. MM). LEO is a harsh environment—the highly erosive effects of atomic oxygen damage Kapton foil—requiring the use of a protective coating. Common coatings available for Kapton (e.g., Al, SiO2, etc.) are problematic for subsequent analysis and interpretation of OD vs. MM origin, being a common elemental component of MM or OD, or having X-ray emission peaks overlapping with those of elements used to distinguish MM from OD. We thus propose palladium coatings as an alternative for this application. Here we report on the performance of palladium as a protective coating for a Kapton-based passive dust detector when exposed to atomic oxygen and impact. When subjected to impact, we observe that thicker coatings suffer delamination such that a coating of <50 nm is recommended. Analysis of atomic oxygen exposed samples shows a thin 10 nm coating of palladium significantly reduces the mass loss of Kapton, while coatings of 25 nm and over perform as well as or better than other commonly used coatings.

/pdf/palladium-coated-kapton-for-use-on-dust-detectors-in-low-2jn5cxw9.pdf

Palladium-coated kapton for use on dust detectors in low earth orbit: Performance under hypervelocity impact and atomic oxygen exposure

Introduction: Newly discovered nakhlite NWA 10659 is a pair with NWA 10153 [1]. We have studied NWA 10659, comparing to the other nine nakhlites including its meteorite pair [1-5] to characterise the origin of the nakhlite hydrothermal system. Methods: We used SEM-EDX to image polished sections and mineral analyses, and FEG-STEM analysis of FIB extractions to investigate the presence of any crystalline clay material. Oxygen isotope measurements were performed in duplicate by laser fluorination [6] on a ~100 mg powdered sample washed in EATG. Results: Similar to its pair, NWA 10659 consists of compositionally zoned tabular pyroxenes (~65%), up to 1.5 mm in length, and larger grains of Fo22-37 olivine (~5%). There is also an interstitial mesostasis (~30%) consisting of orthoclase feldspar and albite, plus phosphate grains and Ti-rich magnetite. NWA 10659 also contains an Fe-rich clay in fracture veins within the olivine and mesostasis. The clay (Fig. 1a) is similar to the poorly crystalline gel present in other nakhlites [2,4]. The average wt% composition in the olivine fractures is SiO2 57.1, Al2O3 0.0, FeO 38.3, MgO 3.2, CaO 1.5 (Mg# =14; Fe/Si wt =0.9), and in the mesostasis SiO2 57.3, Al2O3 3.8, FeO 32.0, MgO 2.9, CaO 3.1, K2O 0.9 (Mg# =13; Fe/Si wt =1.1). This is consistent with the alteration in NWA 10153: SiO2 53.4, Al2O3 2.0, FeO 39.9, MgO 2.5, CaO 1.2, Na2O 0.5, K2O 0.5 (Mg# =10; Fe/Si wt =1.2), normalized 100 wt% anhydrous [5]. No carbonates or salts have been observed in NWA 10659, distinguishing it from Lafayette, Governador Valadares and Nakhla [2]. The O-isotopic composition of NWA 10659 is: δO 2.99‰; δO 5.14‰; ΔO 0.32‰. NWA 10659 appears to be distinct from the O-isotopic composition of its pair NWA 10153, which has δO 2.713‰; δO 4.663‰; ΔO 0.251‰ [1]. The greater δO may be a reflection of high martian clay abundance in NWA 10659.

Nwa 10659: a clay-rich nakhlite pair of nwa 10153

Stardust Track 121 terminal grains contain Fe-oxide. These are consistent with the presence of hydrothermal alteration on the Comet Wild 2 parent body.

Iron Oxide Grains in Stardust Track 121 Grains as Evidence of Comet Wild 2 Hydrothermal Alteration

V. Sautter, M.J. Toplis, R.C. Wiens, A. Cousin, C. Fabre, O. Gasnault, S. Maurice, O. Forni, E.M. Stolper, J. Lasue, A. Ollila, M. Fisk, N. Mangold, P.-Y. Meslin, P. Beck, P. Pinet, L Le Deit, W. Rapin, J.C. Bridges, D. Dyar, J.J. Wray, D. Vaniman, S. Le Mouélic, H. Newson. IMPMC, Muséum d’Histoire Naturelle, Paris, France, IRAP, Toulouse, France, Los Alamos National Laboratory, Los Alamos, NM, USA, G2E, Nancy, France, Caltech, Pasadena, CA, USA, Chevron Energy Technology Company, Houston, TX, USA, College of Earth, Ocean, and Atmospheric Sciences, OR, USA, LPG, Nantes, France, Institut de Planétologie et d’Astrophysique, Grenoble, France, Space Research Centre, Dept. of Physics and Astronomy, University of Leicester, UK, Mount Holyoke College, South Hadley, MA, USA, Georgia Institute of Technology, Atlanta, GA, USA, Planetary Science Institute, Tucson, AZ, USA, Institute of Meteoritics, Albuquerque, NM, USA.[violaine.sautter@mnhn.fr] Introduction: Fifty three igneous float rocks were identified along the Curiosity’s traverse at Gale crater , between sol 13 and 800 [1, 2, 3]. Textural and compositional analyses using MastCam, ChemCam Remote Micro Imager (RMI) and Laser Induced Breakdown Spectroscopy (LIBS) with a ∼300-500μm laser spot allow recognition of mafic and felsic igneous targets including 24 feldspar-rich rocks (over 95 locations totaling 2850 laser shots). At Bradbury rise (sol 13 to 45), located at a distal portion of the alluvial fan derived from Peace Vallis, a fluvial channel cutting through the northern rim of Gale crater, 3 light-toned rocks were initially observed (Blanchet, Stark and Thor Lake) [1]. Since the rover left the fluviolacustrine deposit of Yellow Knife Bay on sol 326, 21 additional feldspar-rich rocks were recognized within Hummocky plains and Rugged units. Methodology: Grain size, shape and distribution were first assessed using MastCam (0.22 and 0.074 mrad/pixel) and RMI cameras (0.0196 mrad/pixel). The smallest visible grains with RMI (assuming a 2 pixels limit resolution) corresponds to 94 μm at 2.4m, 141μm at 3.6m. Moreover, ChemCam LIBS offers the first opportunity to assess mineralogical diversity at grain-scales and, from this, lithological diversity. Independent component analyses (ICA) allow spectral classification of spectra and assessement of lateral heterogeneity between different points within a raster on a given rock. Key element ratios (Al/Si, (Fe+Mg)/Si) and oxide concentrations are derived from the spectra using univariate analysis [4], a method that quantifies the peak areas of well-chosen LIBS lines that are related to concentration thanks to calibration curves using on-board calibration targets (CCCTs: 3 basaltic glasses 1 felsic macusanite glass and 4 ceramics [4,5]). Whole rock estimates are obtained by averaging large rasters (> 9 points) on finegrained homogenous targets. For heterogeneous targets such as phenocrysts in fine-grained mesostasis, whole rock compositions are calculated using modal proportions of felsic and mafic phases and their respective molecular compositions. Rock morphology and texture: Felsic rocks are mainly float faceted by wind erosion. Some targets form 810 cm clasts in polymict conglomerates (Fig.1a) associated with the Peace Vallis alluvial fan system. From morphology, color, grain size, and patina, 3 different classes of rocks have been identified (Fig.1). Porphyritic rocks (9 targets: group 2 in [2]) are defined by light-toned, euhedral white crystals 1-20 mm in length (48 to 65% of the rock volume) set in a dark gray mesostasis (Fig.1a). Light-toned coarse granular rocks (9 targets: group 5 in [2]) are dominated by leucocratic minerals (≈ 80% of the rock volume, Fig.1b). Pearly coarse crystals (>5mm) are locally intergrown with finer (1mm) rectangular translucent gray grains in a graphic texture. Aphyric leucocratic rocks (6 targets: group 3 in [2]) do not have visible grains (less than 100 μm at 2.5 meters, Fig.1c). Sometimes they have shiny scoriaceous surfaces. Porphyritic targets (group 2) and aphanitic to glassy rocks (group 3) are effusive whilst group 5 has granoblastic textures corresponding to intrusive rocks. Vesiculated rocks of group 3 could be pumice of molten rocks resulting from impact.

John Bridges

Papers

Palladium-coated kapton for use on dust detectors in low earth orbit: Performance under hypervelocity impact and atomic oxygen exposure

Nwa 10659: a clay-rich nakhlite pair of nwa 10153

Iron Oxide Grains in Stardust Track 121 Grains as Evidence of Comet Wild 2 Hydrothermal Alteration

Granodiorite and an Alkaline Suite Analysed by ChemCam at Gale Crater

The Colour and Stereo Surface Imaging System (CaSSIS) for ESA's Trace Gas Orbiter.