Frédéric Foucher - Academia.edu (original) (raw)
Papers by Frédéric Foucher
HAL (Le Centre pour la Communication Scientifique Directe), Feb 19, 2018
HAL (Le Centre pour la Communication Scientifique Directe), May 17, 2018
HAL (Le Centre pour la Communication Scientifique Directe), Nov 21, 2017
<ul> <li><strong> Introduction</strong>&a... more <ul> <li><strong> Introduction</strong></li> </ul> <p>In order to study unaltered rocks, Mars rovers are equipped with abrasive and/or drilling devices. NASA&#8217;s Spirit and Opportunity rovers were equipped with a Rock Abrasion Tool to remove the first mm of altered material [1]. NASA&#8217;s Curiosity and Perseverance and ESA&#8217;s Rosalind Franklin ExoMars rovers are equipped with drilling device to collect samples for in situ analysis and, for Perseverance, in preparation for a future Mars Sample Return mission [2-4]. During these drilling phases, a pile of rock powder, of varying size depending on the drilling depth, forms at the surface.</p> <p>The objective of the ExoMars mission will be to search for past or extant biosignatures for which drill-cores will be collected from up to 2 meters deep; the depth at which organic matter is preserved from degrading UV and particle irradiation. The drill has a diameter of 3 cm. The cone of powder at the surface could thus represent more than 1.5 dm<sup>3</sup>, a relatively large quantity of material which will not be analysed by the instruments inside the rover but which could be observed by the CLUPI and PanCam cameras [4-6].</p> <p>Powder can be considered as a textureless material when the grain size is lower than the spatial resolution of the photograph, which is the case for rocks drilled on Mars as observed by MSL [2]. Colour is then the only measurable data; however, this apparent colour is totally dependent on ambient light and on the camera itself. In order to solve this problem, we have developed a new method called CaliPhoto, for which a reference plate is added to the camera's field of view and then image processing is used to compensate for camera characteristics and lighting conditions [7,8]. The images thus obtained can then be compared with each other or with a reference database. Here, we used a series of analogue rocks to demonstrate the ability of the method to identify volcanic rock powders on Mars.</p> <p>&#160;</p> <ul> <li><strong> Materials and methods</strong></li> </ul> <p>The majority of rocks on the surface of Mars are volcanic [9,10] thus, for this study, 23 relevant samples were selected from the Massif Central, in France, in order to cover a large range of volcanic rock types, as designated in the compositional TAS diagram (Total Alkali Silica). The samples were then crushed and each powder was placed in the centre of the CaliPhoto reference plate and photographed. The CaliPhoto image processing was then used to &#8220;calibrate&#8221; the photographs and a database was created (see Fig. 1).</p> <p><img src="" alt="" /></p> <p>Figure 1: Images of the volcanic rock samples after CaliPhoto image processing.</p> <p>&#160;</p> <p>&#160;</p> <ul> <li><strong> Results and discussion </strong></li> </ul> <p>Different tests were carried out [8]. First, each sample was photographed twice in different lighting conditions, the first image was imported into the database and the second was used to test the identification procedure. For 50% of powders, the identification is exact, i.e., the studied powder corresponds to the highest matching identification from the database, in 77% of cases, the studied powder is in the top two matches, and in 95% of cases, it is in the top three. Moreover, when the studied powder is not in the first position, the best match occurs for a rock of similar or close composition.</p> <p>The analogue rock ESA-01-E (picrobasalt), chosen by ESA for its physical and chemical similarities to known Martian rocks, was then used to test the ability of the method to evaluate the composition of a powder that is not in the database. The method successfully identified the sample as a picrobasalt.</p> <p>The rocks were crushed at 4 different grain sizes in order to evaluate the effect of grain size distribution on the method. Indeed, the apparent luminosity of powder is known to increase with decreasing grain size. For 32% of the powders the identification is exact, i.e., the studied powder corresponds to the highest matching value. Moreover, for 91% of cases, a rock with a similar or adjacent composition as defined by the TAS diagram is in the top three matches, even when the powder is not in the database.</p> <p>Finally, by coupling hand sample and powder colour vectors, the identification is exact for 68% of rocks and the studied sample is in the top three matches in 100% of cases. Moreover, when the studied sample is only in the second or third position, the difference with the best match is always lower than 1%.</p> <p>&#160;</p> <ul> <li><strong> Conclusion and…
&lt;p&gt;Our understanding of habitable early Earth environments is limited by th... more &lt;p&gt;Our understanding of habitable early Earth environments is limited by the preservation potential of Archean rock deposits. Sedimentary intervals within the relatively homogeneous volcanic sequences of the Barberton Greenstone Belt (BGB), South Africa and Swaziland, and the eastern Pilbara Craton (PC) in Western Australia provide the best windows into interpreting variability in early Earth environments due to their low strain and low metamorphic grade. These deposits host Earth's oldest, most convincing, evidence of life (~3.3-3.5 Ga), and contribute to a better understanding of both the setting and the origin of life (OoL) and the search for life on other planets, such as Mars.&lt;/p&gt;&lt;p&gt;The 3481 &amp;#177; 2 Ma Dresser Formation, PC contains one of these preservation windows. Previous outcrop studies indicate changes in dominant volcanism composition (mafic to felsic), transitions from subaqueous to subaerial sedimentary facies, and large regional tectonic events that promoted circulation of hydrothermal fluids and secondary alteration. Here we present detailed lithologic and mineralogic details of this early Earth surface deposit, obtained from a recent drilling campaign.&lt;/p&gt;&lt;p&gt;Three fresh drillcores obtained through the lower chert member of the Dresser Formation (~15 m thickness) were drilled at ~75 m below the weathered surface via HQ diamond drilling. Core sites were selected to provide a 3D perspective of geologic variability. Results show a high degree of complex lithology consisting of repeating bedded black carbonaceous cherts (TOC of up to 0.16 wt %), jaspilitic cherts, bedded carbonates, volcanogenic sandstones, beds of sulfidized stromatolites, edgewise conglomerates, laminated siliceous deposits that are texturally similar to hot spring sinter and directly overlie putative feeder veins, and &amp;#160;thin spherulitic beds with petrographic similarities (spherical shapes, quenched features, radial crystal splays, and off-centered vesicles) to younger impact spherule beds. In addition, veins of carbonate, chert, barite and sulfides were identified throughout much of the lower chert member. Lithologic variability occurs on scales of millimetres-decimetres vertically, and from metres to decametres laterally, while mapping of regional scale (kms) stratigraphic sections indicate repetition of specific lithologic successions identified in the cores.&lt;/p&gt;&lt;p&gt;The marked heterogeneity and variability both across stratigraphy and along strike contrasts sharply with marine settings, which are relatively homogeneous and consistent over 10&amp;#8217;s-100&amp;#8217;s of kilometres laterally, and across tens of metres vertically. Younger geologic systems that show similar depositional associations and sharp lateral facies changes include geothermal environments. The presence of sulfidized stromatolites, bedded black cherts, and hot spring deposit indicate that there were a diverse range of habitats (both marine and terrestrial) that hosted life. If spherulitic beds are impactor in origin, they would represent the oldest evidence of a bolide impact in the geologic record. The Dresser Formation provides insights into complex, dynamic, early Earth environments that host apparently already diverse microbial communities adapted to a range of habitats.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;
HAL (Le Centre pour la Communication Scientifique Directe), Apr 24, 2017
International audienc
HAL (Le Centre pour la Communication Scientifique Directe), Jan 12, 2018
International audienc
HAL (Le Centre pour la Communication Scientifique Directe), Feb 17, 2017
Journal of Raman Spectroscopy, 2021
International audienceMicro-Raman spectrometers are used in various domains, from archaeology to ... more International audienceMicro-Raman spectrometers are used in various domains, from archaeology to space exploration. These systems use microscope objectives to focus the laser onto the sample to be analysed. Although this method drastically increases the spatial resolution down to a few hundreds of nanometres, it is also commonly admitted that this focused laser beam may heat and alter the studied material. The setting of the laser power is thus a universal problem for any micro-Raman spectroscopy user who has to find a compromise between the Raman signal intensity and the risk of thermal alteration. This parameter is not easy to set based on bibliographic references because, depending on the architecture of the system used, on the laser wavelength and on the sample, damage may occur at very different laser power levels. Here, we describe the different parameters that influence thermal increase induced by the laser and propose easy to make experiments to measure them. A series of experiments is then carried out to study the thermal alteration of various materials when exposed to a laser beam focused with the different microscope objectives of a micro-Raman system. It is shown that, except for very thin samples or powdered materials, the relevant parameters to consider are the laser power at the sample surface and the duration of exposure to the laser beam, whatever the objective used. We also demonstrate that the risk of sample alteration is almost non-existent for thick transparent materials. Interestingly, it is shown that, for semi-transparent materials, alteration may occur at lower laser power for low magnification objectives than for high magnification objectives. These results are explained by the high aperture angle of microscope objectives which induces high dispersion of the laser within the sample
1913. [4] Murchie, S.L. et al. (2007) JGR 112, E05S03. [5] Morgan, F. et al. (2009) CRISM Data Us... more 1913. [4] Murchie, S.L. et al. (2007) JGR 112, E05S03. [5] Morgan, F. et al. (2009) CRISM Data User’s Workshop, LPSC. [6] Catling D.C. et al. (2005) Icarus, 181, 26-51. [7] Gendrin A. et al. (2005) Science, 307, 1587-1591. Determination of the first level image processing of the Chemcam RMI Instrument for the Mars Science Laboratory (MSL) Rover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
Earth and Space Science, 2016
The SPectral Imager (SPIM) facility is a laboratory VIS-IR spectrometer developed to support spac... more The SPectral Imager (SPIM) facility is a laboratory VIS-IR spectrometer developed to support spaceborne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the Dawn NASA mission and to support the 2018 ExoMars mission in the spectral investigation of Martian subsurface. Specifically, for this mission, a selection of relevant Mars analogue materials has been characterized and stored in the International Space Analogue Rockstore (ISAR), hosted in Orléans, France. In this investigation, two volcanic rock samples from the ISAR collection were analyzed. These two samples were chosen because of their similarity in mineralogical composition and age with Martian basalts and volcanic sands. Moreover, volcanic sands are particularly interesting because they can contain fossils of primitive life forms. The analysis of data collected by SPIM resulted in good agreement with the mineralogical phases detected in these two samples by mineralogical and petrographical techniques, demonstrating the effectiveness of the high spatial and spectral resolution of SPIM for identifying and for mapping different mineralogical species on cut rock and mineral samples.
Journal of Raman Spectroscopy, 2015
Demonstrating the biogenicity of carbonaceous microfossils can be relatively difficult because of... more Demonstrating the biogenicity of carbonaceous microfossils can be relatively difficult because of their small size and simple shape, and to the degradation of the associated organic molecules with time. For Precambrian fossils, it generally requires the use of several techniques to study the shape and the composition of the structure itself, as well as its mineral environment. The ability to identify both organic matter and minerals using Raman spectroscopy makes it a key technique in the field of micropaleontology. Raman instruments are also being developed for the upcoming missions to Mars, ExoMars and Mars 2020, both dedicated to the search for past or present traces of life. However, demonstrating the biotic origin of carbonaceous matter in geological materials using this technique is controversial. Here, we show that Raman mapping instead of single spot analysis can detect variations in the composition of carbonaceous matter associated with fossilized microbes in the 800-Ma-old microfossils from the Draken Formation, Svalbard. This discovery is of great interest because it permits assessment of the biotic origin of a fossilized carbonaceous structure. Raman mapping could thus be of crucial importance in the near future for detecting potential fossilized microbial remains in Martian rocks.
ABSTRACT RESUME: Avec l'avènement des sources synchrotrons de 3 ième génération et le dév... more ABSTRACT RESUME: Avec l'avènement des sources synchrotrons de 3 ième génération et le développement d'optiques focalisantes performantes, il est maintenant possible d'obtenir des faisceaux microniques (voire nanométriques !) et de cartographier à cette échelle en 2 et 3 dimensions les matériaux polycristallins massifs ou en couches minces. Cette technique d'imagerie structurale permet donc d'obtenir à une échelle très fine (typiquement entre 0,1 et 1 micron) des informations quantitatives sur les orientations cristallographiques et les macro et micro déformations intra granulaires, données indispensables et précieuses pour les études des propriétés mécaniques des matériaux mono ou polycristallins. Cette communication présente un exemple d'application dans le domaine des matériaux revêtus et plus particulièrement, dans le cas de décollements de couches minces sous contraintes de compression.
Le Centre pour la Communication Scientifique Directe - HAL - Paris Observatory, Oct 11, 2021
Science Advances
Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, a... more Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, among other instruments, Raman spectrometers. However, there are many unknowns about the stability of Raman-detectable biomolecules in the martian environment, clouding the interpretation of the results. To quantify Raman-detectable biomolecule stability, we exposed seven biomolecules for 469 days to a simulated martian environment outside the International Space Station. Ultraviolet radiation (UVR) strongly changed the Raman spectra signals, but only minor change was observed when samples were shielded from UVR. These findings provide support for Mars mission operations searching for biosignatures in the subsurface. This experiment demonstrates the detectability of biomolecules by Raman spectroscopy in Mars regolith analogs after space exposure and lays the groundwork for a consolidated space-proven database of spectroscopy biosignatures in targeted environments.
Atelier Expérimentation et Instrumentation (AEI), Jul 9, 2019
International audienc
Atelier Expérimentation et Instrumentation (AEI), Jul 9, 2019
International audienc
Le Centre pour la Communication Scientifique Directe - HAL - Diderot, Jul 1, 2017
HAL (Le Centre pour la Communication Scientifique Directe), Feb 19, 2018
HAL (Le Centre pour la Communication Scientifique Directe), May 17, 2018
HAL (Le Centre pour la Communication Scientifique Directe), Nov 21, 2017
<ul> <li><strong> Introduction</strong>&a... more <ul> <li><strong> Introduction</strong></li> </ul> <p>In order to study unaltered rocks, Mars rovers are equipped with abrasive and/or drilling devices. NASA&#8217;s Spirit and Opportunity rovers were equipped with a Rock Abrasion Tool to remove the first mm of altered material [1]. NASA&#8217;s Curiosity and Perseverance and ESA&#8217;s Rosalind Franklin ExoMars rovers are equipped with drilling device to collect samples for in situ analysis and, for Perseverance, in preparation for a future Mars Sample Return mission [2-4]. During these drilling phases, a pile of rock powder, of varying size depending on the drilling depth, forms at the surface.</p> <p>The objective of the ExoMars mission will be to search for past or extant biosignatures for which drill-cores will be collected from up to 2 meters deep; the depth at which organic matter is preserved from degrading UV and particle irradiation. The drill has a diameter of 3 cm. The cone of powder at the surface could thus represent more than 1.5 dm<sup>3</sup>, a relatively large quantity of material which will not be analysed by the instruments inside the rover but which could be observed by the CLUPI and PanCam cameras [4-6].</p> <p>Powder can be considered as a textureless material when the grain size is lower than the spatial resolution of the photograph, which is the case for rocks drilled on Mars as observed by MSL [2]. Colour is then the only measurable data; however, this apparent colour is totally dependent on ambient light and on the camera itself. In order to solve this problem, we have developed a new method called CaliPhoto, for which a reference plate is added to the camera's field of view and then image processing is used to compensate for camera characteristics and lighting conditions [7,8]. The images thus obtained can then be compared with each other or with a reference database. Here, we used a series of analogue rocks to demonstrate the ability of the method to identify volcanic rock powders on Mars.</p> <p>&#160;</p> <ul> <li><strong> Materials and methods</strong></li> </ul> <p>The majority of rocks on the surface of Mars are volcanic [9,10] thus, for this study, 23 relevant samples were selected from the Massif Central, in France, in order to cover a large range of volcanic rock types, as designated in the compositional TAS diagram (Total Alkali Silica). The samples were then crushed and each powder was placed in the centre of the CaliPhoto reference plate and photographed. The CaliPhoto image processing was then used to &#8220;calibrate&#8221; the photographs and a database was created (see Fig. 1).</p> <p><img src="" alt="" /></p> <p>Figure 1: Images of the volcanic rock samples after CaliPhoto image processing.</p> <p>&#160;</p> <p>&#160;</p> <ul> <li><strong> Results and discussion </strong></li> </ul> <p>Different tests were carried out [8]. First, each sample was photographed twice in different lighting conditions, the first image was imported into the database and the second was used to test the identification procedure. For 50% of powders, the identification is exact, i.e., the studied powder corresponds to the highest matching identification from the database, in 77% of cases, the studied powder is in the top two matches, and in 95% of cases, it is in the top three. Moreover, when the studied powder is not in the first position, the best match occurs for a rock of similar or close composition.</p> <p>The analogue rock ESA-01-E (picrobasalt), chosen by ESA for its physical and chemical similarities to known Martian rocks, was then used to test the ability of the method to evaluate the composition of a powder that is not in the database. The method successfully identified the sample as a picrobasalt.</p> <p>The rocks were crushed at 4 different grain sizes in order to evaluate the effect of grain size distribution on the method. Indeed, the apparent luminosity of powder is known to increase with decreasing grain size. For 32% of the powders the identification is exact, i.e., the studied powder corresponds to the highest matching value. Moreover, for 91% of cases, a rock with a similar or adjacent composition as defined by the TAS diagram is in the top three matches, even when the powder is not in the database.</p> <p>Finally, by coupling hand sample and powder colour vectors, the identification is exact for 68% of rocks and the studied sample is in the top three matches in 100% of cases. Moreover, when the studied sample is only in the second or third position, the difference with the best match is always lower than 1%.</p> <p>&#160;</p> <ul> <li><strong> Conclusion and…
&lt;p&gt;Our understanding of habitable early Earth environments is limited by th... more &lt;p&gt;Our understanding of habitable early Earth environments is limited by the preservation potential of Archean rock deposits. Sedimentary intervals within the relatively homogeneous volcanic sequences of the Barberton Greenstone Belt (BGB), South Africa and Swaziland, and the eastern Pilbara Craton (PC) in Western Australia provide the best windows into interpreting variability in early Earth environments due to their low strain and low metamorphic grade. These deposits host Earth's oldest, most convincing, evidence of life (~3.3-3.5 Ga), and contribute to a better understanding of both the setting and the origin of life (OoL) and the search for life on other planets, such as Mars.&lt;/p&gt;&lt;p&gt;The 3481 &amp;#177; 2 Ma Dresser Formation, PC contains one of these preservation windows. Previous outcrop studies indicate changes in dominant volcanism composition (mafic to felsic), transitions from subaqueous to subaerial sedimentary facies, and large regional tectonic events that promoted circulation of hydrothermal fluids and secondary alteration. Here we present detailed lithologic and mineralogic details of this early Earth surface deposit, obtained from a recent drilling campaign.&lt;/p&gt;&lt;p&gt;Three fresh drillcores obtained through the lower chert member of the Dresser Formation (~15 m thickness) were drilled at ~75 m below the weathered surface via HQ diamond drilling. Core sites were selected to provide a 3D perspective of geologic variability. Results show a high degree of complex lithology consisting of repeating bedded black carbonaceous cherts (TOC of up to 0.16 wt %), jaspilitic cherts, bedded carbonates, volcanogenic sandstones, beds of sulfidized stromatolites, edgewise conglomerates, laminated siliceous deposits that are texturally similar to hot spring sinter and directly overlie putative feeder veins, and &amp;#160;thin spherulitic beds with petrographic similarities (spherical shapes, quenched features, radial crystal splays, and off-centered vesicles) to younger impact spherule beds. In addition, veins of carbonate, chert, barite and sulfides were identified throughout much of the lower chert member. Lithologic variability occurs on scales of millimetres-decimetres vertically, and from metres to decametres laterally, while mapping of regional scale (kms) stratigraphic sections indicate repetition of specific lithologic successions identified in the cores.&lt;/p&gt;&lt;p&gt;The marked heterogeneity and variability both across stratigraphy and along strike contrasts sharply with marine settings, which are relatively homogeneous and consistent over 10&amp;#8217;s-100&amp;#8217;s of kilometres laterally, and across tens of metres vertically. Younger geologic systems that show similar depositional associations and sharp lateral facies changes include geothermal environments. The presence of sulfidized stromatolites, bedded black cherts, and hot spring deposit indicate that there were a diverse range of habitats (both marine and terrestrial) that hosted life. If spherulitic beds are impactor in origin, they would represent the oldest evidence of a bolide impact in the geologic record. The Dresser Formation provides insights into complex, dynamic, early Earth environments that host apparently already diverse microbial communities adapted to a range of habitats.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;
HAL (Le Centre pour la Communication Scientifique Directe), Apr 24, 2017
International audienc
HAL (Le Centre pour la Communication Scientifique Directe), Jan 12, 2018
International audienc
HAL (Le Centre pour la Communication Scientifique Directe), Feb 17, 2017
Journal of Raman Spectroscopy, 2021
International audienceMicro-Raman spectrometers are used in various domains, from archaeology to ... more International audienceMicro-Raman spectrometers are used in various domains, from archaeology to space exploration. These systems use microscope objectives to focus the laser onto the sample to be analysed. Although this method drastically increases the spatial resolution down to a few hundreds of nanometres, it is also commonly admitted that this focused laser beam may heat and alter the studied material. The setting of the laser power is thus a universal problem for any micro-Raman spectroscopy user who has to find a compromise between the Raman signal intensity and the risk of thermal alteration. This parameter is not easy to set based on bibliographic references because, depending on the architecture of the system used, on the laser wavelength and on the sample, damage may occur at very different laser power levels. Here, we describe the different parameters that influence thermal increase induced by the laser and propose easy to make experiments to measure them. A series of experiments is then carried out to study the thermal alteration of various materials when exposed to a laser beam focused with the different microscope objectives of a micro-Raman system. It is shown that, except for very thin samples or powdered materials, the relevant parameters to consider are the laser power at the sample surface and the duration of exposure to the laser beam, whatever the objective used. We also demonstrate that the risk of sample alteration is almost non-existent for thick transparent materials. Interestingly, it is shown that, for semi-transparent materials, alteration may occur at lower laser power for low magnification objectives than for high magnification objectives. These results are explained by the high aperture angle of microscope objectives which induces high dispersion of the laser within the sample
1913. [4] Murchie, S.L. et al. (2007) JGR 112, E05S03. [5] Morgan, F. et al. (2009) CRISM Data Us... more 1913. [4] Murchie, S.L. et al. (2007) JGR 112, E05S03. [5] Morgan, F. et al. (2009) CRISM Data User’s Workshop, LPSC. [6] Catling D.C. et al. (2005) Icarus, 181, 26-51. [7] Gendrin A. et al. (2005) Science, 307, 1587-1591. Determination of the first level image processing of the Chemcam RMI Instrument for the Mars Science Laboratory (MSL) Rover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
Earth and Space Science, 2016
The SPectral Imager (SPIM) facility is a laboratory VIS-IR spectrometer developed to support spac... more The SPectral Imager (SPIM) facility is a laboratory VIS-IR spectrometer developed to support spaceborne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the Dawn NASA mission and to support the 2018 ExoMars mission in the spectral investigation of Martian subsurface. Specifically, for this mission, a selection of relevant Mars analogue materials has been characterized and stored in the International Space Analogue Rockstore (ISAR), hosted in Orléans, France. In this investigation, two volcanic rock samples from the ISAR collection were analyzed. These two samples were chosen because of their similarity in mineralogical composition and age with Martian basalts and volcanic sands. Moreover, volcanic sands are particularly interesting because they can contain fossils of primitive life forms. The analysis of data collected by SPIM resulted in good agreement with the mineralogical phases detected in these two samples by mineralogical and petrographical techniques, demonstrating the effectiveness of the high spatial and spectral resolution of SPIM for identifying and for mapping different mineralogical species on cut rock and mineral samples.
Journal of Raman Spectroscopy, 2015
Demonstrating the biogenicity of carbonaceous microfossils can be relatively difficult because of... more Demonstrating the biogenicity of carbonaceous microfossils can be relatively difficult because of their small size and simple shape, and to the degradation of the associated organic molecules with time. For Precambrian fossils, it generally requires the use of several techniques to study the shape and the composition of the structure itself, as well as its mineral environment. The ability to identify both organic matter and minerals using Raman spectroscopy makes it a key technique in the field of micropaleontology. Raman instruments are also being developed for the upcoming missions to Mars, ExoMars and Mars 2020, both dedicated to the search for past or present traces of life. However, demonstrating the biotic origin of carbonaceous matter in geological materials using this technique is controversial. Here, we show that Raman mapping instead of single spot analysis can detect variations in the composition of carbonaceous matter associated with fossilized microbes in the 800-Ma-old microfossils from the Draken Formation, Svalbard. This discovery is of great interest because it permits assessment of the biotic origin of a fossilized carbonaceous structure. Raman mapping could thus be of crucial importance in the near future for detecting potential fossilized microbial remains in Martian rocks.
ABSTRACT RESUME: Avec l'avènement des sources synchrotrons de 3 ième génération et le dév... more ABSTRACT RESUME: Avec l'avènement des sources synchrotrons de 3 ième génération et le développement d'optiques focalisantes performantes, il est maintenant possible d'obtenir des faisceaux microniques (voire nanométriques !) et de cartographier à cette échelle en 2 et 3 dimensions les matériaux polycristallins massifs ou en couches minces. Cette technique d'imagerie structurale permet donc d'obtenir à une échelle très fine (typiquement entre 0,1 et 1 micron) des informations quantitatives sur les orientations cristallographiques et les macro et micro déformations intra granulaires, données indispensables et précieuses pour les études des propriétés mécaniques des matériaux mono ou polycristallins. Cette communication présente un exemple d'application dans le domaine des matériaux revêtus et plus particulièrement, dans le cas de décollements de couches minces sous contraintes de compression.
Le Centre pour la Communication Scientifique Directe - HAL - Paris Observatory, Oct 11, 2021
Science Advances
Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, a... more Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, among other instruments, Raman spectrometers. However, there are many unknowns about the stability of Raman-detectable biomolecules in the martian environment, clouding the interpretation of the results. To quantify Raman-detectable biomolecule stability, we exposed seven biomolecules for 469 days to a simulated martian environment outside the International Space Station. Ultraviolet radiation (UVR) strongly changed the Raman spectra signals, but only minor change was observed when samples were shielded from UVR. These findings provide support for Mars mission operations searching for biosignatures in the subsurface. This experiment demonstrates the detectability of biomolecules by Raman spectroscopy in Mars regolith analogs after space exposure and lays the groundwork for a consolidated space-proven database of spectroscopy biosignatures in targeted environments.
Atelier Expérimentation et Instrumentation (AEI), Jul 9, 2019
International audienc
Atelier Expérimentation et Instrumentation (AEI), Jul 9, 2019
International audienc
Le Centre pour la Communication Scientifique Directe - HAL - Diderot, Jul 1, 2017