Violaine Sautter - Academia.edu (original) (raw)
Papers by Violaine Sautter
Goldschmidt2021 abstracts, 2021
Bulletin of the AAS, 2021
Icarus, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Quantification of copper using Laser Induced Breakdown Spectroscopy (LIBS) Copper occurrence in fractures, potentially related to adsorption on Mn-oxides Copper in sedimentary units suggesting upstream hydrothermal processes that formed a Cu-deposit
Geochimica et Cosmochimica Acta, 2016
Northwest Africa 5790, the latest nakhlite find, is composed of 58 vol. % augite, 6 % olivine and... more Northwest Africa 5790, the latest nakhlite find, is composed of 58 vol. % augite, 6 % olivine and % vitrophyric intercumulus material. Its petrology is comparable to previously discovered nakhlites but with key differences: (1) Augite cores display an unusual zoning between Mg 54 and 60; (2) Olivine macrocrysts have a primary Fe-rich core composition (Mg= 35); (3) the modal proportion of mesostasis is the highest ever described in a nakhlite; (4) It is the most magnetite-rich nakhlite, together with MIL 03346, and exhibits the least anisotropic fabric. Complex primary zoning in cumulus augite indicates resorption due to complex processes such as remobilization of former cumulates in a new magma batch. Textural relationships indicate unambiguously that olivine was growing around resorbed augite, and that olivine growth was continuous while pyroxene growth resumed at a final stage. Olivine core compositions (Mg= 35) are out of equilibrium with the augite core compositions (Mg 60-63) and with the previously inferred nakhlite parental magma (Mg= 29). The presence of oscillatory zoning in olivine and augite precludes subsolidus diffusion that could have modified olivine compositions. NWA 5790 evidences at least two magma batches before eruption, with the implication that melt in equilibrium with augite cores was never in contact with olivine. Iddingsite is absent. Accordingly, the previous scenarios for nakhlite petrogenesis must be revised. The first primary parent magmas of nakhlites generated varied augite cumulates at depth (Mg# 66 to 60) as they differentiated to different extents. A subsequent more evolved magma batch entrained accumulated augite crystals to the surface where they were partly resorbed while olivine crystallized. Trace element variations indicate unambiguously that they represent consanguineous but different magma batches. The compositional differences among the various nakhlites suggest a number of successive lava flows. To account for all observations we propose a petrogenetic model for nakhlites based on several (at least three) thick flows. Although NWA5790 belongs to the very top of one flow, it should come from the lowest flow sampled, based on the lack of iddingsite.
Geophysical Research Letters, 2016
The Curiosity rover observed high Mn abundances (>25 wt % MnO) in fracture-filling materials that... more The Curiosity rover observed high Mn abundances (>25 wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day.
Lithos, 2016
Until recently, Mars was considered a basalt-covered world, but this vision is evolving thanks to... more Until recently, Mars was considered a basalt-covered world, but this vision is evolving thanks to new orbital, in situ and meteorite observations, in particular of rocks of the ancient Noachian period. In this contribution we summarise newly recognised compositional and mineralogical differences between older and more recent rocks, and explore the geodynamic implications of these new findings. For example the MSL rover has discovered abundant felsic rocks close to the landing site coming from the wall of Gale crater ranging from alkali basalt to trachyte. In addition, the recently discovered Martian regolith breccia NWA 7034 (and paired samples) contain many coarse-grained noritic-monzonitic clasts demonstrably Noachian in age, and even some clasts that plot in the mugearite field. Olivine is also conspicuously lacking in these ancient samples, in contrast to later Hesperian rocks. The alkali-suite requires low-degree melting of the Martian mantle at low pressure, whereas the later Hesperian magmatism would appear to be produced by higher mantle temperatures. Various scenarios are proposed to explain these observations, including different styles of magmatic activity (i.e. passive upwelling vs. hotspots). A second petrological suite of increasing interest involves quartzo-feldspathic materials that were first inferred from orbit, in local patches in the southern highlands and in the lower units of Valles Marineris. However, identification of felsic rocks from orbit is limited by the low detectability of feldspar in the near infrared. On the other hand, the MSL rover has described the texture, mineralogy and composition of felsic rocks in Gale crater that are granodiorite-like samples akin to terrestrial TTG (Tonalite-Trondhjemite-Granodiorite suites). These observations, and the low average density of the highlands crust, suggest the early formation of 'continental' crust on Mars, although the details of the geodynamic scenario and the importance of volatiles in their generation are aspects that require further work.
NanoSIMS technique has been used to constrain diffusion profiles in small (
Icarus, 2015
One of the main advantages of ChemCam's LIBS (Laser-Induced Breakdown Spectroscopy) instrument on... more One of the main advantages of ChemCam's LIBS (Laser-Induced Breakdown Spectroscopy) instrument onboard the Curiosity rover is its potential to detect light elements such as hydrogen at fine scales, which has never been achieved on Mars. Hydrogen lines are detected in most of the data obtained within the first 320 sols of the mission at Gale crater, Mars. This work is a description of the hydrogen signal and its variability in the ChemCam LIBS spectra; it discusses the challenges of qualitative and quantitative analysis. Data acquisition and processing steps are investigated and optimized for the detection of hydrogen on Mars. Subtraction of an appropriate dark spectrum and the deconvolution of the superimposed emission of carbon from the low-pressure CO 2-dominated atmosphere are particularly important. Because the intensities of hydrogen are also affected by matrix effects, the hydrogen signal was investigated within groups of targets sharing common chemical features and similar matrices. The different groups cover a variety of rock and soil compositions encountered along the traverse (calcium sulfate veins, mafic soils, felsic, Mg-rich and Fe-rich rocks) including data from both drill holes and their tailings. Almost all these targets were found to be hydrated to variable extents. Soils have systematically higher hydrogen signals than rocks and pebbles, probably as a result of their alteration. The results from rocks suggest that various alteration processes leading to their hydration have taken place, which is consistent with the fluvial lacustrine context, the diagenetic features, and the mineralogy observed by Curiosity in Yellowknife Bay.
Science, 2013
clicking here. colleagues, clients, or customers by , you can order high-quality copies for your ... more clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles
Les zonations minerales sont extremement rares dans les assemblages du manteau superieur lithosph... more Les zonations minerales sont extremement rares dans les assemblages du manteau superieur lithospherique. Il s'agit en effet de domaine de haute-temperature ou la diffusion est efficace. Le clinopyroxene, un des constituants essentiels des eclogites, peut cependant montrer des gradients de concentration important des elements Al-Si-Mg. Ceci a ete observe dans un xenolithe d'eclogite issu du pipe kimberlitique de Roberts Victor en Afrique du Sud ainsi que dans un lit de Websterite a grenat dans des ecailles de peridotites alpines (Freychinede Pyrenees francaise). Dans les deux cas ces heterogeneites de composition dans le clinopyroxene sont associees a des exsolutions de grenat et refletent un refroidissement isobare a partir de temperatures initialement elevees (1400-1300°C). Des experiences de diffusion effectuees en laboratoire sur la paire dioside - molecule de Tschermak ont montre que l'interdiffusion des elements Al-Si etait tres lente. Il a fallu en effet mettre en ...
Journal of Geophysical Research: Planets
The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. T... more The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. This study of the Bagnold dunes focuses on the ChemCam chemical results and also presents findings on the grain size distributions based on the ChemCam Remote Micro-Imager and Mars Hand Lens Imager images. These active dunes are composed of grains that are mostly <250 μm. Their composition is overall similar to that of the aeolian deposits analyzed all along the traverse ("Aeolis Palus soils"). Nevertheless, the dunes contain less volatiles (Cl, H, and S) than the Aeolis Palus soils, which appear to be due to a lower content of volatile-rich fine-grained particles (<100 μm) or a lower content of volatile-rich amorphous component, possibly as a result of (1) a lower level of chemical alteration, (2) the removal of an alteration rind at the surface of the grains during transport, (3) a lower degree of interaction with volcanic gases/aerosols, or (4) physical sorting that removed the smallest and most altered grains. Analyses of the >150 μm grain-size dump piles have shown that coarser grains (150-250 μm) are enriched in the mafic elements Fe and Mn, suggesting a larger content in olivine compared to smaller grains (<150 μm) of the Bagnold dunes. Moreover, the chemistry of soils analyzed in the vicinity of the dunes indicates that they are similar to the dune material. All these observations suggest that the olivine content determined by X-ray diffraction of the <150 μm grain-size sample should be considered as a lower limit for the Bagnold dunes. Plain Language Summary The Curiosity rover, which is exploring the Gale Crater on Mars, has been investigating a dune field. This is the first time an active and extensive dune field is explored by a rover on Mars, and therefore, Curiosity used all the instruments on board in order to better understand how the dunes can form and with what processes and also to assess their chemistry. This in situ investigation was a great opportunity to compare with orbital data. Our work is focusing on chemical data from the ChemCam instrument, as well as on grain size distributions from the image analyses of two cameras. We show that, overall, the dunes are similar in chemistry to the soils analyzed along the traverse, but they are depleted in H, Cl, and S, suggesting that they contain less fine-grained particles or less amorphous component (which is known to be enriched in such elements). This could be due to several processes that we try to investigate. Also, we show that the coarser grains of the dunes (150-250 μm) are enriched in Fe and Mn, probably due to an enrichment in olivine.
Science, 1991
REFERENCES AND NOTES 1. See, for example, DR Nelson, in Statistical Mechan-ics ofMembranes and In... more REFERENCES AND NOTES 1. See, for example, DR Nelson, in Statistical Mechan-ics ofMembranes and Intefaces, DR Nelson, T. Piran, S. Weinberg, Eds. (World Scientific, Singa-pore, 1989); FF Abraham and DR Nelson, Science 249, 393 (1990). 2. AM Polyakov, Gauge Fields and ...
The surface of Mars has long been considered a relatively oxidizing environment, an idea supporte... more The surface of Mars has long been considered a relatively oxidizing environment, an idea supported by the abundance of ferric iron phases observed there. However, compared to iron, manganese is sensitive only to high redox potential oxidants, and when concentrated in rocks, it provides a more specific redox indicator of aqueous environments. Observations from the ChemCam instrument on the Curiosity rover indicate abundances of manganese in and on some rock targets that are 1–2 orders of magnitude higher than previously observed on Mars, suggesting the presence of an as-yet unidentified manganese-rich phase. These results show that the Martian surface has at some point in time hosted much more highly oxidizing conditions than has previously been recognized. 1.
Metal-saturated sulfide assemblages in NWA 2737: Evidence for
Astrobiology
Mars was habitable in its early history, but the consensus is that it is quite inhospitable today... more Mars was habitable in its early history, but the consensus is that it is quite inhospitable today, in particular because its modern climate cannot support stable liquid water at the surface. Here, we report the presence of magmatic Fe/Mg clay minerals within the mesostasis of the martian meteorite NWA 5790, an unaltered 1.3 Ga nakhlite archetypal of the martian crust. These magmatic clay minerals exhibit a vesicular texture that forms a network of microcavities or pockets, which could serve as microreactors and allow molecular crowding, a necessary step for the emergence of life. Because their formation does not depend on climate, such niches for emerging life may have been generated on Mars at many periods throughout its history, regardless of the stability or availability of liquid water at the surface.
The Curiosity rover traverse in Gale crater has explored a large series of sedimentary deposits i... more The Curiosity rover traverse in Gale crater has explored a large series of sedimentary deposits in an ancient lake on Mars. Over the nine kilometers of traverse a recurrent observation has been southward-dipping sedimentary strata, from Shaler at the edge of Yellowknife Bay to the striated units near the Kimberley. Within the sedimentary strata cm- to decimeter- size hollow spheroidal objects and some apparent cylindrical objects have been observed. These features have not been seen by previous landed missions. The first of these were observed on sol 122 in the Gillespie Lake member at Yellowknife Bay. Additional hollow features were observed in the Point Lake outcrop in the same area. More recently a spherical and apparently hollow object, Winnipesaukee, was observed by ChemCam and Mastcam on sol 653. Here we describe the settings, morphology, and associated compositions, and we discuss possible origins of these objects.
Goldschmidt2021 abstracts, 2021
Bulletin of the AAS, 2021
Icarus, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Quantification of copper using Laser Induced Breakdown Spectroscopy (LIBS) Copper occurrence in fractures, potentially related to adsorption on Mn-oxides Copper in sedimentary units suggesting upstream hydrothermal processes that formed a Cu-deposit
Geochimica et Cosmochimica Acta, 2016
Northwest Africa 5790, the latest nakhlite find, is composed of 58 vol. % augite, 6 % olivine and... more Northwest Africa 5790, the latest nakhlite find, is composed of 58 vol. % augite, 6 % olivine and % vitrophyric intercumulus material. Its petrology is comparable to previously discovered nakhlites but with key differences: (1) Augite cores display an unusual zoning between Mg 54 and 60; (2) Olivine macrocrysts have a primary Fe-rich core composition (Mg= 35); (3) the modal proportion of mesostasis is the highest ever described in a nakhlite; (4) It is the most magnetite-rich nakhlite, together with MIL 03346, and exhibits the least anisotropic fabric. Complex primary zoning in cumulus augite indicates resorption due to complex processes such as remobilization of former cumulates in a new magma batch. Textural relationships indicate unambiguously that olivine was growing around resorbed augite, and that olivine growth was continuous while pyroxene growth resumed at a final stage. Olivine core compositions (Mg= 35) are out of equilibrium with the augite core compositions (Mg 60-63) and with the previously inferred nakhlite parental magma (Mg= 29). The presence of oscillatory zoning in olivine and augite precludes subsolidus diffusion that could have modified olivine compositions. NWA 5790 evidences at least two magma batches before eruption, with the implication that melt in equilibrium with augite cores was never in contact with olivine. Iddingsite is absent. Accordingly, the previous scenarios for nakhlite petrogenesis must be revised. The first primary parent magmas of nakhlites generated varied augite cumulates at depth (Mg# 66 to 60) as they differentiated to different extents. A subsequent more evolved magma batch entrained accumulated augite crystals to the surface where they were partly resorbed while olivine crystallized. Trace element variations indicate unambiguously that they represent consanguineous but different magma batches. The compositional differences among the various nakhlites suggest a number of successive lava flows. To account for all observations we propose a petrogenetic model for nakhlites based on several (at least three) thick flows. Although NWA5790 belongs to the very top of one flow, it should come from the lowest flow sampled, based on the lack of iddingsite.
Geophysical Research Letters, 2016
The Curiosity rover observed high Mn abundances (>25 wt % MnO) in fracture-filling materials that... more The Curiosity rover observed high Mn abundances (>25 wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day.
Lithos, 2016
Until recently, Mars was considered a basalt-covered world, but this vision is evolving thanks to... more Until recently, Mars was considered a basalt-covered world, but this vision is evolving thanks to new orbital, in situ and meteorite observations, in particular of rocks of the ancient Noachian period. In this contribution we summarise newly recognised compositional and mineralogical differences between older and more recent rocks, and explore the geodynamic implications of these new findings. For example the MSL rover has discovered abundant felsic rocks close to the landing site coming from the wall of Gale crater ranging from alkali basalt to trachyte. In addition, the recently discovered Martian regolith breccia NWA 7034 (and paired samples) contain many coarse-grained noritic-monzonitic clasts demonstrably Noachian in age, and even some clasts that plot in the mugearite field. Olivine is also conspicuously lacking in these ancient samples, in contrast to later Hesperian rocks. The alkali-suite requires low-degree melting of the Martian mantle at low pressure, whereas the later Hesperian magmatism would appear to be produced by higher mantle temperatures. Various scenarios are proposed to explain these observations, including different styles of magmatic activity (i.e. passive upwelling vs. hotspots). A second petrological suite of increasing interest involves quartzo-feldspathic materials that were first inferred from orbit, in local patches in the southern highlands and in the lower units of Valles Marineris. However, identification of felsic rocks from orbit is limited by the low detectability of feldspar in the near infrared. On the other hand, the MSL rover has described the texture, mineralogy and composition of felsic rocks in Gale crater that are granodiorite-like samples akin to terrestrial TTG (Tonalite-Trondhjemite-Granodiorite suites). These observations, and the low average density of the highlands crust, suggest the early formation of 'continental' crust on Mars, although the details of the geodynamic scenario and the importance of volatiles in their generation are aspects that require further work.
NanoSIMS technique has been used to constrain diffusion profiles in small (
Icarus, 2015
One of the main advantages of ChemCam's LIBS (Laser-Induced Breakdown Spectroscopy) instrument on... more One of the main advantages of ChemCam's LIBS (Laser-Induced Breakdown Spectroscopy) instrument onboard the Curiosity rover is its potential to detect light elements such as hydrogen at fine scales, which has never been achieved on Mars. Hydrogen lines are detected in most of the data obtained within the first 320 sols of the mission at Gale crater, Mars. This work is a description of the hydrogen signal and its variability in the ChemCam LIBS spectra; it discusses the challenges of qualitative and quantitative analysis. Data acquisition and processing steps are investigated and optimized for the detection of hydrogen on Mars. Subtraction of an appropriate dark spectrum and the deconvolution of the superimposed emission of carbon from the low-pressure CO 2-dominated atmosphere are particularly important. Because the intensities of hydrogen are also affected by matrix effects, the hydrogen signal was investigated within groups of targets sharing common chemical features and similar matrices. The different groups cover a variety of rock and soil compositions encountered along the traverse (calcium sulfate veins, mafic soils, felsic, Mg-rich and Fe-rich rocks) including data from both drill holes and their tailings. Almost all these targets were found to be hydrated to variable extents. Soils have systematically higher hydrogen signals than rocks and pebbles, probably as a result of their alteration. The results from rocks suggest that various alteration processes leading to their hydration have taken place, which is consistent with the fluvial lacustrine context, the diagenetic features, and the mineralogy observed by Curiosity in Yellowknife Bay.
Science, 2013
clicking here. colleagues, clients, or customers by , you can order high-quality copies for your ... more clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles
Les zonations minerales sont extremement rares dans les assemblages du manteau superieur lithosph... more Les zonations minerales sont extremement rares dans les assemblages du manteau superieur lithospherique. Il s'agit en effet de domaine de haute-temperature ou la diffusion est efficace. Le clinopyroxene, un des constituants essentiels des eclogites, peut cependant montrer des gradients de concentration important des elements Al-Si-Mg. Ceci a ete observe dans un xenolithe d'eclogite issu du pipe kimberlitique de Roberts Victor en Afrique du Sud ainsi que dans un lit de Websterite a grenat dans des ecailles de peridotites alpines (Freychinede Pyrenees francaise). Dans les deux cas ces heterogeneites de composition dans le clinopyroxene sont associees a des exsolutions de grenat et refletent un refroidissement isobare a partir de temperatures initialement elevees (1400-1300°C). Des experiences de diffusion effectuees en laboratoire sur la paire dioside - molecule de Tschermak ont montre que l'interdiffusion des elements Al-Si etait tres lente. Il a fallu en effet mettre en ...
Journal of Geophysical Research: Planets
The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. T... more The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. This study of the Bagnold dunes focuses on the ChemCam chemical results and also presents findings on the grain size distributions based on the ChemCam Remote Micro-Imager and Mars Hand Lens Imager images. These active dunes are composed of grains that are mostly <250 μm. Their composition is overall similar to that of the aeolian deposits analyzed all along the traverse ("Aeolis Palus soils"). Nevertheless, the dunes contain less volatiles (Cl, H, and S) than the Aeolis Palus soils, which appear to be due to a lower content of volatile-rich fine-grained particles (<100 μm) or a lower content of volatile-rich amorphous component, possibly as a result of (1) a lower level of chemical alteration, (2) the removal of an alteration rind at the surface of the grains during transport, (3) a lower degree of interaction with volcanic gases/aerosols, or (4) physical sorting that removed the smallest and most altered grains. Analyses of the >150 μm grain-size dump piles have shown that coarser grains (150-250 μm) are enriched in the mafic elements Fe and Mn, suggesting a larger content in olivine compared to smaller grains (<150 μm) of the Bagnold dunes. Moreover, the chemistry of soils analyzed in the vicinity of the dunes indicates that they are similar to the dune material. All these observations suggest that the olivine content determined by X-ray diffraction of the <150 μm grain-size sample should be considered as a lower limit for the Bagnold dunes. Plain Language Summary The Curiosity rover, which is exploring the Gale Crater on Mars, has been investigating a dune field. This is the first time an active and extensive dune field is explored by a rover on Mars, and therefore, Curiosity used all the instruments on board in order to better understand how the dunes can form and with what processes and also to assess their chemistry. This in situ investigation was a great opportunity to compare with orbital data. Our work is focusing on chemical data from the ChemCam instrument, as well as on grain size distributions from the image analyses of two cameras. We show that, overall, the dunes are similar in chemistry to the soils analyzed along the traverse, but they are depleted in H, Cl, and S, suggesting that they contain less fine-grained particles or less amorphous component (which is known to be enriched in such elements). This could be due to several processes that we try to investigate. Also, we show that the coarser grains of the dunes (150-250 μm) are enriched in Fe and Mn, probably due to an enrichment in olivine.
Science, 1991
REFERENCES AND NOTES 1. See, for example, DR Nelson, in Statistical Mechan-ics ofMembranes and In... more REFERENCES AND NOTES 1. See, for example, DR Nelson, in Statistical Mechan-ics ofMembranes and Intefaces, DR Nelson, T. Piran, S. Weinberg, Eds. (World Scientific, Singa-pore, 1989); FF Abraham and DR Nelson, Science 249, 393 (1990). 2. AM Polyakov, Gauge Fields and ...
The surface of Mars has long been considered a relatively oxidizing environment, an idea supporte... more The surface of Mars has long been considered a relatively oxidizing environment, an idea supported by the abundance of ferric iron phases observed there. However, compared to iron, manganese is sensitive only to high redox potential oxidants, and when concentrated in rocks, it provides a more specific redox indicator of aqueous environments. Observations from the ChemCam instrument on the Curiosity rover indicate abundances of manganese in and on some rock targets that are 1–2 orders of magnitude higher than previously observed on Mars, suggesting the presence of an as-yet unidentified manganese-rich phase. These results show that the Martian surface has at some point in time hosted much more highly oxidizing conditions than has previously been recognized. 1.
Metal-saturated sulfide assemblages in NWA 2737: Evidence for
Astrobiology
Mars was habitable in its early history, but the consensus is that it is quite inhospitable today... more Mars was habitable in its early history, but the consensus is that it is quite inhospitable today, in particular because its modern climate cannot support stable liquid water at the surface. Here, we report the presence of magmatic Fe/Mg clay minerals within the mesostasis of the martian meteorite NWA 5790, an unaltered 1.3 Ga nakhlite archetypal of the martian crust. These magmatic clay minerals exhibit a vesicular texture that forms a network of microcavities or pockets, which could serve as microreactors and allow molecular crowding, a necessary step for the emergence of life. Because their formation does not depend on climate, such niches for emerging life may have been generated on Mars at many periods throughout its history, regardless of the stability or availability of liquid water at the surface.
The Curiosity rover traverse in Gale crater has explored a large series of sedimentary deposits i... more The Curiosity rover traverse in Gale crater has explored a large series of sedimentary deposits in an ancient lake on Mars. Over the nine kilometers of traverse a recurrent observation has been southward-dipping sedimentary strata, from Shaler at the edge of Yellowknife Bay to the striated units near the Kimberley. Within the sedimentary strata cm- to decimeter- size hollow spheroidal objects and some apparent cylindrical objects have been observed. These features have not been seen by previous landed missions. The first of these were observed on sol 122 in the Gillespie Lake member at Yellowknife Bay. Additional hollow features were observed in the Point Lake outcrop in the same area. More recently a spherical and apparently hollow object, Winnipesaukee, was observed by ChemCam and Mastcam on sol 653. Here we describe the settings, morphology, and associated compositions, and we discuss possible origins of these objects.