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Sautter V.,IMPMC | Toplis M.J.,IRAP | Wiens R.C.,Los Alamos National Laboratory | Cousin A.,IRAP | And 21 more authors.
Nature Geoscience | Year: 2015

Understanding of the geologic evolution of Mars has been greatly improved by recent orbital, in situ and meteorite data, but insights into the earliest period of Martian magmatism (4.1 to 3.7 billion years ago) remain scarce. The landing site of NASA's Curiosity rover, Gale crater, which formed 3.61 billion years ago within older terrain, provides a window into this earliest igneous history. Along its traverse, Curiosity has discovered light-toned rocks that contrast with basaltic samples found in younger regions. Here we present geochemical data and images of 22 specimens analysed by Curiosity that demonstrate that these light-toned materials are feldspar-rich magmatic rocks. The rocks belong to two distinct geochemical types: alkaline compositions containing up to 67 wt% SiO 2 and 14 wt% total alkalis (Na 2 O + K 2 O) with fine-grained to porphyritic textures on the one hand, and coarser-grained textures consistent with quartz diorite and granodiorite on the other hand. Our analysis reveals unexpected magmatic diversity and the widespread presence of silica- and feldspar-rich materials in the vicinity of the landing site at Gale crater. Combined with the identification of feldspar-rich rocks elsewhere and the low average density of the crust in the Martian southern hemisphere, we conclude that silica-rich magmatic rocks may constitute a significant fraction of ancient Martian crust and may be analogous to the earliest continental crust on Earth. © 2015 Macmillan Publishers Limited.


Downing M.,ESO | Kolb J.,ESO | Balard P.,Laboratoire Dastrophysique Of Marseille | Dierickx B.,Caeleste | And 17 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The success of the next generation of instruments for ELT class telescopes will depend upon improving the image quality by exploiting sophisticated Adaptive Optics (AO) systems. One of the critical components of the AO systems for the E-ELT has been identified as the optical Laser/Natural Guide Star WFS detector. The combination of large format, 1760×1680 pixels to finely sample the wavefront and the spot elongation of laser guide stars, fast frame rate of 700 frames per second (fps), low read noise (< 3e-), and high QE (> 90%) makes the development of this device extremely challenging. Design studies concluded that a highly integrated Backside Illuminated CMOS Imager built on High Resistivity silicon as the most likely technology to succeed. Two generations of the CMOS Imager are being developed: a) the already designed and manufactured NGSD (Natural Guide Star Detector), a quarter-sized pioneering device of 880×840 pixels capable of meeting first light needs of the E-ELT; b) the LGSD (Laser Guide Star Detector), the larger full size device. The detailed design is presented including the approach of using massive parallelism (70,400 ADCs) to achieve the low read noise at high pixel rates of ∼3 Gpixel/s and the 88 channel LVDS 220Mbps serial interface to get the data off-chip. To enable read noise closer to the goal of 1e- to be achieved, a split wafer run has allowed the NGSD to be manufactured in the more speculative, but much lower read noise, Ultra Low Threshold Transistors in the unit cell. The NGSD has come out of production, it has been thinned to 12μm, backside processed and packaged in a custom 370pin Ceramic PGA (Pin Grid Array). First results of tests performed both at e2v and ESO are presented. © 2014 SPIE.


Downing M.,ESO | Kolb J.,ESO | Baade D.,ESO | Balard P.,Laboratoire Dastrophysique Of Marseille | And 17 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The success of the next generation of instruments for 8 to 40-m class telescopes will depend upon improving the image quality (correcting the distortion caused by atmospheric turbulence) by exploiting sophisticated Adaptive Optics (AO) systems. One of the critical components of the AO systems for the E-ELT has been identified as the Laser/Natural Guide Star (LGS/NGS) WaveFront Sensing (WFS) detector. The combination of large format, 1760×1680 pixels to finely sample (84×84 sub-apertures) the wavefront and the spot elongation of laser guide stars, fast frame rate of 700 (up to 1000) frames per second, low read noise (< 3e-), and high QE (> 90%) makes the development of such a device extremely challenging. Design studies by industry concluded that a thinned and backside-illuminated CMOS Imager as the most promising technology. This paper describes the multi-phased development plan that will ensure devices are available on-time for E-ELT first-light AO systems; the different CMOS pixel architectures studied; measured results of technology demonstrators that have validated the CMOS Imager approach; the design explaining the approach of massive parallelism (70,000 ADCs) needed to achieve low noise at high pixel rates of ∼3 Gpixel/s ; the 88 channel LVDS data interface; the restriction that stitching (required due to the 5×6cm size) posed on the design and the solutions found to overcome these limitations. Two generations of the CMOS Imager will be built: a pioneering quarter sized device of 880×840 pixels capable of meeting first light needs of the E-ELT called NGSD (Natural Guide Star Detector); followed by the full size device, the LGSD (Laser Guide Star Detector). Funding sources: OPTICON FP6 and FP7 from European Commission and ESO. © 2012 SPIE.


Sautter V.,IMPMC | Toplis M.J.,IRAP | Beck P.,Institute Of Planetologie Et Dastrophysique | Mangold N.,LPG Nantes | And 16 more authors.
Lithos | Year: 2016

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. © 2016 Elsevier B.V.


Patru F.,Osservatorio Astrofisico di Arcetri | Patru F.,European Southern Observatory | Antichi J.,Osservatorio Astrofisico di Arcetri | Rabou P.,Institute Of Planetologie Et Dastrophysique | And 6 more authors.
3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes | Year: 2013

Discretized Aperture Mapping (DAM) appears as an original filtering technique easy to play with existing adaptive optics (AO) systems. In its essential DAM operates as an optical passive filter removing part of the phase residuals in the wavefront without introducing any difficult-to-align component in the Fourier conjugate of the entrance pupil plane. DAM reveals as a new interferometric technique combined with spatial filtering allowing direct imaging over a narrow field of view (FOV). In fact, the entrance pupil of a single telescope is divided into many sub-pupils so that the residual phase in each sub-pupil is filtered up to the DAM cut-off frequency. DAM enables to smooth the small scale wavefront defects which correspond to high spatial frequencies in the pupil plane and to low angular frequencies in the image plane. Close to the AO Nyquist frequency, such pupil plane spatial frequencies are not well measured by the wavefront sensor (WFS) due to aliasing. Once bigger than the AO Nyquist frequency, they are no more measured by the WFS due to the fitting limit responsible for the narrow AO FOV. The corresponding image plane angular frequencies are not transmitted by DAM and are useless to image small FOVs, as stated by interferometry. That is why AO and DAM are complementary assuming that the DAM cut-off frequency is equal to the AO Nyquist frequency. Here we describe the imaging capabilities when DAMis placed downstream an AO system, over a convenient pupil which precedes the scientific detector. We show firstly that the imaging properties are preserved on a narrow FOV allowing direct imaging throughout interferometry. Then we show how the residual pupil plane spatial frequencies bigger than the AO Nyquist one are filtered out, as well as the residual halo in the image is dimmed.


Patru F.,Osservatorio Astrofisico di Arcetri | Antichi J.,Osservatorio Astrofisico di Arcetri | Mawet D.,European Southern Observatory | Jolissaint L.,Haute Ecole dIngenierie et de Gestion du Canton de Vaud | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Discretized Aperture Mapping (DAM) appears as an original filtering technique easy to play with existing adaptive optics (AO) systems. In its essential DAM operates as an optical passive filter removing part of the phase residuals in the wavefront without introducing any difficult-to-align component in the Fourier conjugate of the entrance pupil plane. DAM reveals as a new interferometric technique combined with spatial filtering allowing direct imaging over a narrow field of view (FOV). In fact, the entrance pupil of a single telescope is divided into many sub-pupils so that the residual phase in each sub-pupil is filtered up to the DAM cut-off frequency. DAM enables to smooth the small scale wavefront defects which correspond to high spatial frequencies in the pupil plane and to low angular frequencies in the image plane. Close to the AO Nyquist frequency, such pupil plane spatial frequencies are not well measured by the wavefront sensor (WFS) due to aliasing. Once bigger than the AO Nyquist frequency, they are no more measured by the WFS due to the fitting limit responsible for the narrow AO FOV. The corresponding image plane angular frequencies are not transmitted by DAM and are useless to image small FOVs, as stated by interferometry. That is why AO and DAM are complementary assuming that the DAM cut-off frequency is equal to the AO Nyquist frequency. Here we describe the imaging capabilities when DAM is placed downstream an AO system, over a convenient pupil which precedes the scientific detector. We show firstly that the imaging properties are preserved on a narrow FOV allowing direct imaging throughout interferometry. Then we show how the residual pupil plane spatial frequencies bigger than the AO Nyquist one are filtered out, as well as the residual halo in the image is dimmed. © 2014 SPIE.


Mendillo M.,Boston University | Narvaez C.,Boston University | Lawler G.,Boston University | Kofman W.,Institute Of Planetologie Et Dastrophysique | And 4 more authors.
Geophysical Research Letters | Year: 2015

The total electron content (TEC) of a planetary ionosphere is dominated by plasma near and above the height of maximum electron density (Nmax). The ratio TEC/Nmax represents the thickness (τ) of a TEC slab of uniform density (Nmax). For a photochemical ionosphere, τ relates to the scale height (H=kT/mg) of the ionized neutral gas as τ∼4×H. Derived temperatures refer to ∼160km in thermosphere height - below the asymptotic temperature of the exosphere. The MARSIS instrument on Mars Express has produced data sets of TEC and Nmax. We used them to form τ patterns versus solar zenith angle and solar cycle phase. For daytime (SZA<90°) conditions, <τ>day∼50km, decreasing rapidly for solar zenith angle (SZA)>90° to<τ>night∼25km. These correspond to Tn values of 250°K and 125°K. Using Mars Global Surveyor data, τ patterns show a mild dependence upon the solar EUV flux proxy F10.7, with ΔTn(°K)∼0.3° per unit change in F10.7 at Mars. Key Points The ratio TEC/Nmax of a planetary ionosphere represents the slab thickness Slab thickness relates to the neutral atmosphere's scale height and temperature Mars' ionosphere has a nighttime slab thickness of 25 km that doubles in daytime ©2015. American Geophysical Union. All Rights Reserved.


Downing M.,ESO | Kolb J.,ESO | Dierickx B.,Caeleste | Defernez A.,Caeleste | And 10 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

The success of the next generation of instruments for ELT class telescopes will depend upon improving the image quality by exploiting sophisticated Adaptive Optics (AO) systems. One of the critical components of the AO systems for the European Extremely Large Telescope (E-ELT) has been identified as the Large Visible Laser/Natural Guide Star AO Wavefront Sensing (WFS) detector. The combination of large format, 1600x1600 pixels to finely sample the wavefront and the spot elongation of laser guide stars (LGS), fast frame rate of 700 frames per second (fps), low read noise (3e-), and high QE ( 90%) makes the development of this device extremely challenging. Results of design studies concluded that a highly integrated Backside Illuminated CMOS Imager built on High Resistivity silicon as the most suitable technology. Two generations of the CMOS Imager are planned: A) a smaller â€pioneering' device of 800x800 pixels capable of meeting first light needs of the E-ELT. The NGSD, the topic of this paper, is the first iteration of this device; b) the larger full sized device called LGSD. The NGSD has come out of production, it has been thinned to 12μm, backside processed and packaged in a custom 370pin Ceramic PGA (Pin Grid Array). Results of comprehensive tests performed both at e2v and ESO are presented that validate the choice of CMOS Imager as the correct technology for the E-ELT Large Visible WFS Detector. These results along with plans for a second iteration to improve two issues of hot pixels and cross-Talk are presented. © 2016 SPIE.


Mendillo M.,Boston University | Narvaez C.,Boston University | Withers P.,Boston University | Matta M.,Boston University | And 2 more authors.
Planetary and Space Science | Year: 2013

Abstract The Mars Express (MEX) mission includes a multi-purpose radio instrument called the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). When used in its ionospheric-penetrating subsurface sounder (SS) radar mode, a by-product of the MARSIS observations is the ray-path-integral of electron densities, called the total electron content (TEC). We have used the initial TEC database of approximately 1.2 million TEC values spanning the period June 2005 to September 2007 to study the basic characteristics of TEC morphology and variability. We find quantitative agreement between the TEC values measured and those computed from model simulations of global diurnal behavior. With the basic photo-chemistry of the martian ionosphere a well understood process, it is the departures from average conditions that need specification and modeling. Here we use MARSIS TEC to do this quantitatively. We explore the specification of variability using different ways to define it: standard deviations from sample averages versus departures from control curves. For global studies, we computed the standard deviation (σ in %) of mean values of TEC (in TECU of 1015 e -/m2) sorted by latitude, longitude, solar zenith angle (SZA), local time, season, and locations with/without strong crustal magnetic fields (50 nT at 150 km). For daytime conditions (SZA<75), the global average 〈TEC⌠is ~6 TECU with σ=~20%, while for nighttime (SZA>105) 〈TECâŒ; is ~0.3 TECU with σ=~75%. Daytime variability is enhanced in the latitude region 0-30 S, a pattern that needs validation by later observations before its source can be identified. Nighttime variability is noticeably larger in regions of strong crustal magnetic fields (B) - an effect noted by previous authors. For regional studies, high resolution latitude patterns of variability in the southern hemisphere - within the longitude sector 150-210 of strong crustal-B values - were computed as percentage changes with respect to zonally-averaged patterns outside the region of interest. We present evidence for the first time of B-fields affecting the variability of the daytime ionosphere by small amounts (~±5%). Under nighttime conditions, the B-field associated variability is ~±20%. The results also reveal an anti-correlation between daytime and nighttime variability ordered by the inclination angle (I) of the B-fields. TEC variability is greater as I approaches vertical at night, but higher during the day (by smaller amounts) where I approaches horizontal patterns. © 2013 Elsevier Ltd.

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