content 23-May-2019 22:32:18

Patrick Pinet

Biography & lecture abstracts

Partrick Pinet
Patrick Pinet was born in Fes, Morocco (1957). He studied theoretical physics at the Univ. of Pau (France) and geophysical engineering at the Institut de Physique du Globe de Strasbourg (IPGS) as well as astronomy; he earned his PhD in Planetary Geophysics in 1985 (Impact cratering and the rheology of the Moon) from Univ. of Toulouse (France), and he then entered the Centre National de la Recherche Scientifique (CNRS). He has 25 years of experience in the field of planetary surfaces studies related to telescopic, spaceborne and airborne remote sensing observations, with a major emphasis on high spatial resolution imaging spectroscopy of the Moon and Mars in the visible and near-infrared domains. He has developed new methodologies for hyperspectral image processing analysis, with applied aspects in the field of terrestrial geology and environmental studies. He has participated to the Clementine mission, has been co-investigator on the imaging experiment onboard the SMART-1 mission (ESA) and the HRSC camera and OMEGA imaging spectrometer onboard Mars Express (ESA), still in operation around Mars since 2003. His main scientific interests are photometry and reflectance spectroscopy, planetary geology and surface mineralogy, impact cratering processes, planetary geomorphology and geodynamics. He has co-authored more than 75 peer-reviewed papers in international journals and books and 200 studies presented at conferences. From 1994 until 2003, he has been director of the Planetary and Terrestrial Geophysics Department, Observatoire Midi-Pyrénées, a laboratory involved in space techniques and geodesy, planetary sciences, seismology, mantle convection, tectonics and quantitative geomorphology. From 1991 until 1999, he was adjunct-Secretary General of the International Union of Geodesy and Geophysics (IUGG). He is currently adjunct-director of the Institut de Recherches en Astrophysique et Planétologie (IRAP), Midi-Pyrenees Observatory. In recognition of his scientific achievements in the field of exploration of the physical and compositional properties of the Moon and terrestrial planets, IAU named the asteroid 2000 NB 14 as 18111 Pinet (2005). Patrick' s main hobbies are skiing, mountain-hiking, travelling and discovering foreign languages.

Lecture Mineralogy-1: Principles of spectroscopy
Reflectance spectroscopy in the 0.4-3 micron spectral domain is particularly adapted to remote-sensing planetary exploration given the number of mechanisms that cause absorptions in this wavelength region. These mechanisms involve electronic transitions within and between atoms (crystal field, metal-metal intervalence charge transfer, oxygen-metal charge transfer) as well as electronic transitions in molecular orbitals and vibrational transitions in molecules and crystals. Theoretical models from the solid state physics are used to interpret these spectra. However, laboratory measurements are absolutely needed for the controlled interpretation of remotely acquired spectra and very comprehensive laboratory databases have been generated along the years to do so. Beyond the detection of the presence of minerals, another aspect which is mandatory for approaching a quantitative characterisation of the mineralogy, addressing the composition and abundance of the minerals, especially in the case of complex mixtures, relies on progress recently made in the field of non-linear deconvolution of complex spectra. As an example, a powerful technique called Modified Gaussian Model (MGM) permits under some conditions to deconvolve overlapping absorptions of mafic mineral spectra into their fundamental absorption components, each Gaussian function used, directly accounting for an electronic transition.

Lecture Mineralogy-2: Mineralogy and Mars evolution
Relying on the fundamental principles and methodologies addressed earlier, it is now possible to model simple and complex mafic mineralogies including binary and ternary mixtures, for a large range of grain sizes. Accordingly, we will describe the progressive deciphering of the martian mineralogy as it is currently understood. Among many observations based on orbital hyperspectral coverages and in situ spectrophotometric measurements carried out at the Mars Exploration Rovers (Spirit and Opportunity) landing sites (Gusev crater and Meridiani), detailed analysis of reflectance spectra of mafic silicates, serpentines, sulfates, phyllosilicates (clay minerals) and carbonates appear extremely promising for studying the geological evolution of Mars. As an example, the occurrence of serpentine-bearing rocks on Mars restricted to the Noachian period is a strong indication in favour of the existence of early hydrothermal alteration of ultramafic rocks. This has obvious implications about the past and present environmental formation conditions and thus for search for traces of extinct life on Mars.

Lecture Mineralogy-3: Planetary regolith
This lecture will address the optical characterisation of the planetary regolith surface properties from theoretical, experimental and orbital spectrophotometry, with a special emphasis toward a multiscale understanding of the optical properties and their implications for the martian surface. Once the fundamental principles of radiative transfer modeling will have been introduced and reviewed, we will explore some applications to Mars. Given the huge amount of knowledge gained from the different spectroscopic surveys performed from orbit with the fleet of recent missions to Mars (e.g., Mars Global Surveyor, Mars Express, Mars Reconnaissance Orbiter, etc) and from the various in-situ measurements at the MER landing sites, we will focus on the Gusev crater to demonstrate how efficient the combination of remote sensing techniques can be for the purpose of characterising the physical surface properties of the martian regolith, with the propagation of the in-situ knowledge to large expanses of Mars only monitored from space. Aware of the intrinsic complexity associated with the spectrophotometric signal returned by the martian surface, which is influenced by both the surface and atmospheric contributions, we will then turn our attention towards the notion of surface changes and their possible detection.

Lecture Mineralogy-4: Optical properties and surface changes on Mars
Historically, the terminology 'variable features' on the surface of Mars was used to define albedo patterns on Mars that appeared, disappeared, or changed shape as a function of time, as seen on Mariner-9 images. They are attributed to the interaction of the atmosphere with the surface and are considered to represent erosion, deposition, and/or repositioning of sand and dust by the wind. Variable features associated with topographic landforms, such as craters, are called wind streaks and are thought to represent the prevailing wind direction at the time of their formation. However, the detection of albedo features is sensitive to many variables, including the imaging system on the spacecraft, the illumination and viewing geometry and the spectral range through which the image is acquired. As recently demonstrated, the optical instruments onboard Mars Express (ESA) and MRO (Mars Reconnaissance Orbiter from NASA) have allowed observations revealing the complexity associated with the colour observations produced under different geometry and illumination conditions, arising from the interplay between shade, shadow and the presence of a scattering atmosphere. This calls for a more advanced strategy than what has been undertaken so far for detecting and monitoring systematically martian variable features. This strategy would be based on the analysis of multi-angular observations repeated through time under close geometry and illumination conditions. This should be the "reference" case for disentangling surface changes through time (i.e., true variable features) from optical changes induced by the surface properties (e.g., subpixel roughness) and/or complex photometric effects related to the presence of a mixed granular rocky surface layer.

Last Update: 04 November 2011

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