S. Le Mouélic
University of Nantes
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Featured researches published by S. Le Mouélic.
Science | 2013
Rebecca M. E. Williams; John P. Grotzinger; William E. Dietrich; S. Gupta; Dawn Y. Sumner; Roger C. Wiens; Nicolas Mangold; M. C. Malin; Kenneth S. Edgett; Sylvestre Maurice; O. Forni; O. Gasnault; A. M. Ollila; H. Newsom; Gilles Dromart; Marisa C. Palucis; R. A. Yingst; R. B. Anderson; K. E. Herkenhoff; S. Le Mouélic; W. Goetz; M. B. Madsen; A. Koefoed; J. K. Jensen; John C. Bridges; S. P. Schwenzer; Kevin W. Lewis; K. Stack; David M. Rubin; L. C. Kah
Going to Mars The Mars Science Laboratory spacecraft containing the Curiosity rover, was launched from Earth in November 2011 and arrived at Gale crater on Mars in August 2012. Zeitlin et al. (p. 1080) report measurements of the energetic particle radiation environment inside the spacecraft during its cruise to Mars, confirming the hazard likely to be posed by this radiation to astronauts on a future potential trip to Mars. Williams et al. (p. 1068, see the Perspective by Jerolmack) report the detection of sedimentary conglomerates (pebbles mixed with sand and turned to rock) at Gale crater. The rounding of the rocks suggests abrasion of the pebbles as they were transported by flowing water several kilometers or more from their source. Observations from the Curiosity rover of rounded pebbles in sedimentary rocks confirm ancient water flows on Mars. [Also see Perspective by Jerolmack] Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.
Science | 2014
Scott M. McLennan; R. B. Anderson; James F. Bell; John C. Bridges; F. Calef; John Campbell; B. C. Clark; S. M. Clegg; P. G. Conrad; A. Cousin; D. J. Des Marais; Gilles Dromart; M. D. Dyar; Lauren A. Edgar; Bethany L. Ehlmann; Claude Fabre; O. Forni; O. Gasnault; R. Gellert; S. Gordon; A. Grant; John P. Grotzinger; S. Gupta; K. E. Herkenhoff; J. A. Hurowitz; Penelope L. King; S. Le Mouélic; L. A. Leshin; R. Leveille; Kevin W. Lewis
Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine–rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
Science | 2013
P.-Y. Meslin; O. Gasnault; Olivier Forni; S. Schröder; A. Cousin; G. Berger; S. M. Clegg; J. Lasue; S. Maurice; Violaine Sautter; S. Le Mouélic; Roger C. Wiens; C. Fabre; W. Goetz; David L. Bish; Nicolas Mangold; Bethany L. Ehlmann; N. Lanza; A.-M. Harri; R. B. Anderson; E. B. Rampe; Timothy H. McConnochie; P. Pinet; Diana L. Blaney; R. Leveille; D. Archer; B. L. Barraclough; Steve Bender; D. Blake; Jennifer G. Blank
The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of widespread martian soils and is similar in composition to the martian dust. It possesses a ubiquitous hydrogen signature in ChemCam spectra, corresponding to the hydration of the amorphous phases found in the soil by the CheMin instrument. This hydration likely accounts for an important fraction of the global hydration of the surface seen by previous orbital measurements. ChemCam analyses did not reveal any significant exchange of water vapor between the regolith and the atmosphere. These observations provide constraints on the nature of the amorphous phases and their hydration.
Journal of Geophysical Research | 2014
M. Nachon; Samuel Michael Clegg; N. Mangold; Susanne Schröder; L. C. Kah; Gilles Dromart; A. M. Ollila; Jeffrey R. Johnson; D. Z. Oehler; John C. Bridges; S. Le Mouélic; O. Forni; Roger C. Wiens; R. B. Anderson; Diana L. Blaney; James F. Bell; B. C. Clark; A. Cousin; M. D. Dyar; Bethany L. Ehlmann; C. Fabre; O. Gasnault; John P. Grotzinger; J. Lasue; E. Lewin; R. Leveille; Scott M. McLennan; Sylvestre Maurice; P.-Y. Meslin; W. Rapin
The Curiosity rover has analyzed abundant light-toned fracture-fill material within the Yellowknife Bay sedimentary deposits. The ChemCam instrument, coupled with Mastcam and ChemCam/Remote Micro Imager images, was able to demonstrate that these fracture fills consist of calcium sulfate veins, many of which appear to be hydrated at a level expected for gypsum and bassanite. Anhydrite is locally present and is found in a location characterized by a nodular texture. An intricate assemblage of veins crosses the sediments, which were likely formed by precipitation from fluids circulating through fractures. The presence of veins throughout the entire similar to 5 m thick Yellowknife Bay sediments suggests that this process occurred well after sedimentation and cementation/lithification of those sediments. The sulfur-rich fluids may have originated in previously precipitated sulfate-rich layers, either before the deposition of the Sheepbed mudstones or from unrelated units such as the sulfates at the base of Mount Sharp. The occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively nonacidic conditions.
Journal of Geophysical Research | 2014
Violaine Sautter; C. Fabre; O. Forni; Michael J. Toplis; A. Cousin; A. M. Ollila; P.-Y. Meslin; Sylvestre Maurice; Roger C. Wiens; David Baratoux; Nicolas Mangold; S. Le Mouélic; O. Gasnault; Gilles Berger; J. Lasue; R. A. Anderson; E. Lewin; Mariek E. Schmidt; D. Dyar; Bethany L. Ehlmann; John C. Bridges; B. C. Clark; P. C. Pinet
Textural and compositional analyses using Chemistry Camera (ChemCam) remote microimager and laser-induced breakdown spectroscopy (LIBS) have been performed on five float rocks and coarse gravels along the first 100 m of the Curiosity traverse at Bradbury Rise. ChemCam, the first LIBS instrument sent to another planet, offers the opportunity to assess mineralogic diversity at grain-size scales (~ 100 µm) and, from this, lithologic diversity. Depth profiling indicates that targets are relatively free of surface coatings. One type of igneous rock is volcanic and includes both aphanitic (Coronation) and porphyritic (Mara) samples. The porphyritic sample shows dark grains that are likely pyroxene megacrysts in a fine-grained mesostasis containing andesine needles. Both types have magnesium-poor basaltic compositions and in this respect are similar to the evolved Jake Matijevic rock analyzed further along the Curiosity traverse both with Alpha-Particle X-ray Spectrometer and ChemCam instruments. The second rock type encountered is a coarse-grained intrusive rock (Thor Lake) showing equigranular texture with millimeter size crystals of feldspars and Fe-Ti oxides. Such a rock is not unique at Gale as the surrounding coarse gravels (such as Beaulieu) and the conglomerate Link are dominated by feldspathic (andesine-bytownite) clasts. Finally, alkali feldspar compositions associated with a silica polymorph have been analyzed in fractured filling material of Preble rock and in Stark, a putative pumice or an impact melt. These observations document magmatic diversity at Gale and describe the first fragments of feldspar-rich lithologies (possibly an anorthosite) that may be ancient crust transported from the crater rim and now forming float rocks, coarse gravel, or conglomerate clasts.
Journal of Geophysical Research | 2014
Diana L. Blaney; Roger C. Wiens; Sylvestre Maurice; S. M. Clegg; Ryan Anderson; L. C. Kah; S. Le Mouélic; A. M. Ollila; Nathan T. Bridges; R. L. Tokar; Gilles Berger; John C. Bridges; A. Cousin; B. C. Clark; M. D. Dyar; Penelope L. King; N. Lanza; N. Mangold; P.-Y. Meslin; H. Newsom; S. Schröder; Steven J. Rowland; Jeffrey R. Johnson; Lauren A. Edgar; O. Gasnault; O. Forni; Mariek E. Schmidt; W. Goetz; Kathryn M. Stack; Dawn Y. Sumner
A suite of eight rocks analyzed by the Curiosity Rover while it was stopped at the Rocknest sand ripple shows the greatest chemical divergence of any potentially sedimentary rocks analyzed in the early part of the mission. Relative to average Martian soil and to the stratigraphically lower units encountered as part of the Yellowknife Bay formation, these rocks are significantly depleted in MgO, with a mean of 1.3 wt %, and high in Fe, averaging over 20 wt % FeO_T, with values between 15 and 26 wt % FeO_T. The variable iron and low magnesium and rock texture make it unlikely that these are igneous rocks. Rock surface textures range from rough to smooth, can be pitted or grooved, and show various degrees of wind erosion. Some rocks display poorly defined layering while others seem to show possible fractures. Narrow vertical voids are present in Rocknest 3, one of the rocks showing the strongest layering. Rocks in the vicinity of Rocknest may have undergone some diagenesis similar to other rocks in the Yellowknife Bay Formation as indicated by the presence of soluble calcium phases. The most reasonable scenario is that fine-grained sediments, potentially a mixture of feldspar-rich rocks from Bradbury Rise and normal Martian soil, were lithified together by an iron-rich cement.
Journal of Geophysical Research | 2016
L. Le Deit; N. Mangold; O. Forni; A. Cousin; J. Lasue; Susanne Schröder; Roger C. Wiens; Dawn Y. Sumner; C. Fabre; Kathryn M. Stack; R. B. Anderson; Diana L. Blaney; S. M. Clegg; Gilles Dromart; Martin R. Fisk; O. Gasnault; John P. Grotzinger; Sanjeev Gupta; N. Lanza; S. Le Mouélic; S. Maurice; Scott M. McLennan; P.-Y. Meslin; M. Nachon; H. Newsom; V. Payré; W. Rapin; Melissa S. Rice; Violaine Sautter; Allan H. Treiman
Key Points: • Mean K2O abundance in sedimentary rocks >5 times higher than that of the average Martian crust • Presence of alkali feldspars and K-phyllosilicates in basaltic sedimentary rocks along the traverse • The K-bearing minerals likely have a detrital origin
Journal of Geophysical Research | 2015
N. Mangold; O. Forni; Gilles Dromart; Kathryn M. Stack; Roger C. Wiens; O. Gasnault; Dawn Y. Sumner; M. Nachon; P.-Y. Meslin; R. B. Anderson; B. Barraclough; James F. Bell; Gilles Berger; Diana L. Blaney; John C. Bridges; F. Calef; B. C. Clark; S. M. Clegg; A. Cousin; Lauren A. Edgar; Kenneth S. Edgett; Bethany L. Ehlmann; C. Fabre; Martin R. Fisk; John P. Grotzinger; Sanjeev Gupta; K. E. Herkenhoff; Joel A. Hurowitz; Jeffrey R. Johnson; L. C. Kah
The Yellowknife Bay formation represents a similar to 5m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the Curiosity rover in Gale crater, Mars. Previous works have mainly focused on the mudstones that were drilled by the rover at two locations. The present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures. Results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column. Though the chemistry of the sediments does not vary much in the lower part of the stratigraphy, the variations in alkali elements indicate variations in the source material and/or physical sorting, as shown by the identification of alkali feldspars. The sandstones contain similar relative proportions of hydrogen to the mudstones below, suggesting the presence of hydrous minerals that may have contributed to their cementation. Slight variations in magnesium correlate with changes in textures suggesting that diagenesis through cementation and dissolution modified the initial rock composition and texture simultaneously. The upper part of the stratigraphy (similar to 1m thick) displays rocks with different compositions suggesting a strong change in the depositional system. The presence of float rocks with similar compositions found along the rover traverse suggests that some of these outcrops extend further away in the nearby hummocky plains.
Journal of Geophysical Research | 2014
Nathan T. Bridges; F. Calef; Bernard Hallet; K. E. Herkenhoff; N. Lanza; S. Le Mouélic; Claire E. Newman; Diana L. Blaney; M.A. de Pablo; G. A. Kocurek; Yves Langevin; Kevin W. Lewis; N. Mangold; Sylvestre Maurice; P.-Y. Meslin; P. C. Pinet; Nilton De Oliveira Renno; Melissa S. Rice; M. E. Richardson; Violaine Sautter; Ronald S. Sletten; Roger C. Wiens; R. A. Yingst
Ventifacts, rocks abraded by wind-borne particles, are found in Gale Crater, Mars. In the eastward drive from “Bradbury Landing” to “Rocknest,” they account for about half of the float and outcrop seen by Curiositys cameras. Many are faceted and exhibit abrasion textures found at a range of scales, from submillimeter lineations to centimeter-scale facets, scallops, flutes, and grooves. The drive path geometry in the first 100 sols of the mission emphasized the identification of abrasion facets and textures formed by westerly flow. This upwind direction is inconsistent with predictions based on models and the orientation of regional dunes, suggesting that these ventifact features formed from very rare high-speed winds. The absence of active sand and evidence for deflation in the area indicates that most of the ventifacts are fossil features experiencing little abrasion today.
Journal of Geophysical Research | 2014
Raymond E. Arvidson; Paolo Bellutta; F. Calef; A. A. Fraeman; James B. Garvin; O. Gasnault; J. A. Grant; John P. Grotzinger; Victoria E. Hamilton; M. Heverly; K. A. Iagnemma; Jeffrey R. Johnson; N. Lanza; S. Le Mouélic; N. Mangold; D. W. Ming; M. Mehta; Richard V. Morris; H. Newsom; Nilton De Oliveira Renno; David M. Rubin; Juergen Schieber; Ronald S. Sletten; Nathan Stein; F. Thuillier; Ashwin R. Vasavada; J. Vizcaino; Roger C. Wiens
Physical properties of terrains encountered by the Curiosity rover during the first 360 sols of operations have been inferred from analysis of the scour zones produced by Sky Crane Landing System engine plumes, wheel touch down dynamics, pits produced by Chemical Camera (ChemCam) laser shots, rover wheel traverses over rocks, the extent of sinkage into soils, and the magnitude and sign of rover-based slippage during drives. Results have been integrated with morphologic, mineralogic, and thermophysical properties derived from orbital data, and Curiosity-based measurements, to understand the nature and origin of physical properties of traversed terrains. The hummocky plains (HP) landing site and traverse locations consist of moderately to well-consolidated bedrock of alluvial origin variably covered by slightly cohesive, hard-packed basaltic sand and dust, with both embedded and surface-strewn rock clasts. Rock clasts have been added through local bedrock weathering and impact ejecta emplacement and form a pavement-like surface in which only small clasts (<5 to 10 cm wide) have been pressed into the soil during wheel passages. The bedded fractured (BF) unit, site of Curiositys first drilling activity, exposes several alluvial-lacustrine bedrock units with little to no soil cover and varying degrees of lithification. Small wheel sinkage values (<1 cm) for both HP and BF surfaces demonstrate that compaction resistance countering driven-wheel thrust has been minimal and that rover slippage while traversing across horizontal surfaces or going uphill, and skid going downhill, have been dominated by terrain tilts and wheel-surface material shear modulus values.