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  • 1.
    Binzel, R.P.
    et al.
    Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA; Chercheur Associé, IMCCE-Observatoire de Paris, France.
    DeMeo, F.E.
    Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
    Bus, S.J
    Univ. Hawaii.
    Tokunaga, A.
    Univ. Hawaii.
    Burbine, T.H.
    Mount Holyoke College.
    Lantz, C.
    Institut d'Astrophysique Spatiale, CNRS/Université Paris Saclay, France.
    Polishook, D.
    Weizmann Institute.
    Morbidelli, A.
    Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lagrange, France.
    Birlan, M.
    IMCCE, Paris Observatory and Astronomical Institute of Romanian Academy, Bucharest, Romania.
    Vernazza, P.
    LAM–CNRS/AMU, Marseille, France.
    Burt, B.J
    Lowell Observatory.
    Moskovitz, N.
    Lowell Observatory.
    Slivan, S.M.
    Wellesley College.
    Thomas, C.A
    Northern Arizona University.
    Rivkin, A.S.
    Johns Hopkins University Applied Physics Laboratory.
    Hicks, M.D.
    Jet Propulsion Laboratory.
    Dunn, T.
    Colby College.
    Reddy, V.
    Univ. Arizona.
    Sanchez, J.A.
    Planetary Science Institute.
    Granvik, Mikael
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Univ. Helsinki.
    Kohout, T.
    Univ. Helsinki.
    Compositional Distributions and Evolutionary Processes for the Near-Earth Object Population: Results from the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS)2019In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 324, p. 41-76Article in journal (Refereed)
    Abstract [en]

    Advancing technology in near-infrared instrumentation and dedicated planetary telescope facilities have enabled nearly two decades of reconnoitering the spectral properties for near-Earth objects (NEOs). We report measured spectral properties for more than 1000 NEOs, representing >5 percent of the currently discovered population. Thermal flux detected below 2.5 microns allows us to make albedo estimates for nearly 50 objects, including two comets. Additional spectral data are reported for more than 350 Mars-crossing asteroids. Most of these measurements were achieved through a collaboration between researchers at the Massachusetts Institute of Technology and the University of Hawaii, with full cooperation of the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We call this project the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS; myth-neos). While MITHNEOS has continuously released all spectral data for immediate use by the scientific community, our objectives for this paper are to: (1) detail the methods and limits of the survey data, (2) formally present a compilation of results including their taxonomic classification within a single internally consistent framework, (3) perform a preliminary analysis on the overall population characteristics with a concentration toward deducing key physical processes and identifying their source region for escaping the main belt. Augmenting our newly published measurements are the previously published results from the broad NEO community, including many results graciously shared by colleagues prior to formal publication. With this collective data set, we find the near-Earth population matches the diversity of the main-belt, with all main-belt taxonomic classes represented in our sample. Potentially hazardous asteroids (PHAs) as well as the subset of mission accessible asteroids (ΔV≤ 7 km/s) both appear to be a representative mix of the overall NEO population, consistent with strong dynamical mixing for the population that interacts most closely with Earth. Mars crossers, however, are less diverse and appear to more closely match the inner belt population from where they have more recently diffused. The fractional distributions of major taxonomic classes (60% S, 20% C, 20% other) appear remarkably constant over two orders of magnitude in size (10 km to 100 m), which is eight orders of magnitude in mass, though we note unaccounted bias effects enter into our statistics below about 500m. Given the range of surface ages, including possible refreshment by planetary encounters, we are able to identify a very specific space weathering vector tracing the transition from Q- to Sq- to S-types that follows the natural dispersion for asteroid spectra mapped into principal component space. We also are able to interpret a shock darkening vector that may account for some objects having featureless spectra. Space weathering effects for C-types are complex; these results are described separately by Lantz, Binzel, DeMeo. (2018, Icarus 302, 10-17). Independent correlation of dynamical models with taxonomic classes map the escape zones for NEOs to main-belt regions consistent with well established heliocentric compositional gradients. We push beyond taxonomy to interpret our visible plus near-infrared spectra in terms of the olivine and pyroxene mineralogy consistent with the H, L, and LL classes of ordinary chondrites meteorites. Correlating meteorite interpretations with dynamical escape region models shows a preference for LL chondrites to arrive from the ν6 resonance and H chondrites to have a preferential signature from the mid-belt region (3:1 resonance). L chondrites show some preference toward the outer belt, but not at a significant level. We define a Space Weathering Parameter as a continuous variable and find evidence for step-wise changes in space weathering properties across different planet crossing zones in the inner solar system. Overall we hypothesize the relative roles of planetary encounters, YORP spin-up, and thermal cycling across the inner solar system.

  • 2.
    Carlsson, Ella
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fedorov, A.
    Centre d’Etude Spatiale des Rayonnements, Toulouse.
    Barabash, S.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Dierker, C.
    Technical University of Braunschweig.
    Mass composition of the escaping plasma at Mars2006In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 182, no 2, p. 320-328Article in journal (Refereed)
    Abstract [en]

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.

  • 3.
    Cordoba-Jabonero, Carmen
    et al.
    Instituto Nacional de Técnica Aeroespacial, Área de Investigación e Instrumentación Atmosférica.
    Zorzano, María Paz
    Centro de Astrobiología, CSIC-INTA.
    Selsis, Franck
    Centro de Astrobiología, CSIC-INTA.
    Patel, Manish R.
    Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes .
    Cockell, Charles Seaton
    British Antarctic Survey, High Cross, Madingley Road, Cambridge .
    Radiative habitable zones in martian polar environments2005In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 175, no 2, p. 360-371Article in journal (Refereed)
    Abstract [en]

    The biologically damaging solar ultraviolet (UV) radiation (quantified by the DNA-weighted dose) reaches the martian surface in extremely high levels. Searching for potentially habitable UV-protected environments on Mars, we considered the polar ice caps that consist of a seasonally varying CO2 ice cover and a permanent H2O ice layer. It was found that, though the CO2 ice is insufficient by itself to screen the UV radiation, at ∼1 m depth within the perennial H2O ice the DNA-weighted dose is reduced to terrestrial levels. This depth depends strongly on the optical properties of the H2O ice layers (for instance snow-like layers). The Earth-like DNA-weighted dose and Photosynthetically Active Radiation (PAR) requirements were used to define the upper and lower limits of the northern and southern polar Radiative Habitable Zone (RHZ) for which a temporal and spatial mapping was performed. Based on these studies we conclude that photosynthetic life might be possible within the ice layers of the polar regions. The thickness varies along each martian polar spring and summer between ∼1.5 and 2.4 m for H2O ice-like layers, and a few centimeters for snow-like covers. These martian Earth-like radiative habitable environments may be primary targets for future martian astrobiological missions. Special attention should be paid to planetary protection, since the polar RHZ may also be subject to terrestrial contamination by probes.

  • 4.
    Cousin, A.
    et al.
    Los Alamos National Laboratory.
    Meslin, P.Y.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Rapin, W.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Mangold, N.
    Laboratoire Planétologie et Géodynamique, LPGNantes, CNRS UMR 6112, Université de Nantes.
    Fabre, C.
    Université de Lorraine, Nancy.
    Gasnault, O.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Forni, O.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Tokar, R.
    Planetary Science Institute, Tucson.
    Ollila, A.
    University of New Mexico, Albuquerque.
    Schröder, S.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Lasue, J.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Maurice, S.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Sautter, V.
    Museum National d’Histoire Naturelle, Paris.
    Newsom, H.
    University of New Mexico, Albuquerque.
    Vaniman, D.
    Planetary Science Institute, Tucson.
    Mouélic, S. Le
    Laboratoire Planétologie et Géodynamique, LPGNantes, CNRS UMR 6112, Université de Nantes.
    Dyar, D.
    Mount Holyoke College, South Hadley.
    Berger, G.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Blaney, D.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Nachon, M.
    Laboratoire Planétologie et Géodynamique, LPGNantes, CNRS UMR 6112, Université de Nantes.
    Dromart, G.
    Laboratoire de Géologie de Lyon.
    Lanza, N.
    Los Alamos National Laboratory.
    Clark, B.
    Space Science Institute, Boulder, Colorado.
    Clegg, S.
    Los Alamos National Laboratory.
    Delapp, D.
    Los Alamos National Laboratory.
    Compositions of coarse and fine particles in martian soils at gale: A window into the production of soils2015In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, p. 22-42Article in journal (Refereed)
    Abstract [en]

    The ChemCam instrument onboard the Curiosity rover provides for the first time an opportunity to study martian soils at a sub-millimeter resolution. In this work, we analyzed 24 soil targets probed by ChemCam during the first 250 sols on Mars. Using the depth profile capability of the ChemCam LIBS (Laser-Induced Breakdown Spectroscopy) technique, we found that 45% of the soils contained coarse grains (>500 μm). Three distinct clusters have been detected: Cluster 1 shows a low SiO2 content; Cluster 2 corresponds to coarse grains with a felsic composition, whereas Cluster 3 presents a typical basaltic composition. Coarse grains from Cluster 2 have been mostly observed exposed in the vicinity of the landing site, whereas coarse grains from Clusters 1 and 3 have been detected mostly buried, and were found all along the rover traverse. The possible origin of these coarse grains was investigated. Felsic (Cluster 2) coarse grains have the same origin as the felsic rocks encountered near the landing site, whereas the origin of the coarse grains from Clusters 1 and 3 seems to be more global. Fine-grained soils (particle size < laser beam diameter which is between 300 and 500 μm) show a homogeneous composition all along the traverse, different from the composition of the rocks encountered at Gale. Although they contain a certain amount of hydrated amorphous component depleted in SiO2, possibly present as a surface coating, their overall chemical homogeneity and their close-to-basaltic composition suggest limited, or isochemical alteration, and a limited interaction with liquid water. Fine particles and coarse grains from Cluster 1 have a similar composition, and the former could derive from weathering of the latter. Overall martian soils have a bulk composition between that of fine particles and coarse grains. This work shows that the ChemCam instrument provides a means to study the variability of soil composition at a scale not achievable by bulk chemical analyses.

  • 5.
    Fonseca, Ricardo
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC).
    Martín-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Planetary Boundary Layer and Circulation Dynamics at Gale Crater, Mars2018In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 302, p. 537-559Article in journal (Refereed)
    Abstract [en]

    The Mars implementation of the Planet Weather Research and Forecasting (PlanetWRF) model, MarsWRF, is used here to simulate the atmospheric conditions at Gale Crater for different seasons during a period coincident with the Curiosity rover operations. The model is first evaluated with the existing single-point observations from the Rover Environmental Monitoring Station (REMS), and is then used to provide a larger scale interpretation of these unique measurements as well as to give complementary information where there are gaps in the measurements.

    The variability of the planetary boundary layer depth may be a driver of the changes in the local dust and trace gas content within the crater. Our results show that the average time when the PBL height is deeper than the crater rim increases and decreases with the same rate and pattern as Curiosity's observations of the line-of-sight of dust within the crater and that the season when maximal (minimal) mixing is produced is Ls 225°-315° (Ls 90°-110°). Thus the diurnal and seasonal variability of the PBL depth seems to be the driver of the changes in the local dust content within the crater. A comparison with the available methane measurements suggests that changes in the PBL depth may also be one of the factors that accounts for the observed variability, with the model results pointing towards a local source to the north of the MSL site.

    The interaction between regional and local flows at Gale crater is also investigated assuming that the meridional wind, the dynamically important component of the horizontal wind at Gale, anomalies with respect to the daily mean can be approximated by a sinusoidal function as they typically oscillate between positive (south to north) and negative (north to south) values that correspond to upslope/downslope or downslope/upslope regimes along the crater rim and Mount Sharp slopes and the dichotomy boundary. The smallest magnitudes are found in the northern crater floor in a region that comprises Bradbury Landing, in particular at Ls 90° when they are less than 1 m s−1, indicating very little lateral mixing with outside air. The largest amplitudes occur in the south-western portions of the crater where they can exceed 20 m s−1. Should the slope flows along the crater rims interact with the dichotomy boundary flow, which is more likely at Ls 270° and very unlikely at Ls 90°, they are likely to interact constructively for a few hours from late evening to nighttime (∼17-23 LMST) and from pre-dawn early morning (∼5-11 LMST) hours at the norther crater rim and destructively at night (∼22-23 LMST) and in the morning (∼10-11 LMST) at the southern crater rim.

    We conclude that a better understanding of the PBL and circulation dynamics has important implications for the variability of the concentration of dust, non-condensable and trace gases at the bottom of other craters on Mars as mixing with outside air can be achieved vertically, through changes in the PBL depth, and laterally, by the transport of air into and out of the crater.

  • 6.
    Granvik, Mikael
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Department of Physics, University of Helsinki.
    Brown, Peter
    Department of Physics and Astronomy, University of Western Ontario.
    Identification of meteorite source regions in the solar system2018In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 311, p. 271-287Article in journal (Refereed)
    Abstract [en]

    Over the past decade there has been a large increase in the number of automated camera networks that monitor the sky for fireballs. One of the goals of these networks is to provide the necessary information for linking meteorites to their pre-impact, heliocentric orbits and ultimately to their source regions in the solar system. We re-compute heliocentric orbits for the 25 meteorite falls published to date from original data sources. Using these orbits, we constrain their most likely escape routes from the main asteroid belt and the cometary region by utilizing a state-of-the-art orbit model of the near-Earth-object population, which includes a size-dependence in delivery efficiency. While we find that our general results for escape routes are comparable to previous work, the role of trajectory measurement uncertainty in escape-route identification is explored for the first time. Moreover, our improved size-dependent delivery model substantially changes likely escape routes for several meteorite falls, most notably Tagish Lake which seems unlikely to have originated in the outer main belt as previously suggested. We find that reducing the uncertainty of fireball velocity measurements below  ∼ 0.1 km/s does not lead to reduced uncertainties in the identification of their escape routes from the asteroid belt and, further, their ultimate source regions. This analysis suggests that camera networks should be optimized for the largest possible number of meteorite recoveries with measured speed precisions of order 0.1 km/s.

  • 7.
    Heldmann, Jennifer L.
    et al.
    NASA Ames Research Center.
    Carlsson, Ella
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Swedish Institute of Space Physics, Kiruna, Sweden.
    Johansson, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mellon, Michael T.
    University of Colorado.
    Toon, Owen B.
    University of Colorado.
    Observations of martian gullies and constraints on potential formation mechanisms: Part 2. The northern hemisphere2007In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 188, no 2, p. 324-344Article in journal (Refereed)
    Abstract [en]

    The formation process(es) responsible for creating the observed geologically recent gully features on Mars has remained the subject of intense debate since their discovery. We present new data and analysis of northern hemisphere gullies from Mars Global Surveyor data which is used to test the various proposed mechanisms of gully formation. We located 137 Mars Orbiter Camera (MOC) images in the northern hemisphere that contain clear evidence of gully landforms and analyzed these images in combination with Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) data to provide quantitative measurements of numerous gully characteristics. Parameters we measured include apparent source depth and distribution, vertical and horizontal dimensions, slopes, orientations, and present-day characteristics that affect local ground temperatures. Northern hemisphere gullies are clustered in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia. These gullies form in craters (84%), knobby terrain (4%), valleys (3%), other/unknown terrains (9%) and are found on all slope orientations although the majority of gullies are equator-facing. Most gullies (63%) are associated with competent rock strata, 26% are not associated with strata, and 11% are ambiguous. Assuming thermal conductivities derived from TES measurements as well as modeled surface temperatures, we find that 95% of the gully alcove bases with adequate data coverage lie at depths where subsurface temperatures are greater than 273 K and 5% of the alcove bases lie within the solid water regime. The average alcove length is 470 m and the average channel length is 690 m. Based on a comparison of measured gully features with predictions from the various models of gully formation, we find that models involving carbon dioxide, melting ground ice in the upper few meters of the soil, dry landslide, and surface snowmelt are the least likely to describe the formation of the martian gullies. Although some discrepancies still exist between prediction and observation, the shallow and deep aquifer models remain as the most plausible theories. Interior processes involving subsurface fluid sources are generally favored over exogenic processes such as wind and snowfall for explaining the origin of the martian gullies. These findings gleaned from the northern hemisphere data are in general agreement with analyses of gullies in the southern hemisphere [Heldmann, J.L., Mellon, M.T., 2004. Icarus 168, 285-304].

  • 8.
    Johnson, Jeffrey R.
    et al.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    III, J.F. Bell
    Arizona State University.
    Bender, S.
    Planetary Science Institute, Tucson.
    Blaney, D.
    Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Cloutis, E.
    University of Winnipeg, Manitoba.
    DeFlores, L.
    Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Ehlmann, B.
    California Institute of Technology, Pasadena.
    Gasnault, O.
    Université de Toulouse, CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Gondet, B.
    Institut d’Astrophysique Spatiale, Batîment 12, 91405 Orsay Campus.
    Kinch, K.
    Niels Bohr Institute, University of Copenhagen.
    Lemmon, M.
    Texas A&M University, College Station.
    Mouélic, S. Le
    Université de Nantes, Laboratoire de Planétologie et Géodynamique.
    Maurice, S.
    Université de Toulouse, CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Rice, M.
    California Institute of Technology, Pasadena.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars2015In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, p. 74-92Article in journal (Refereed)
    Abstract [en]

    The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400–840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets’ housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (

  • 9.
    Karman, Tijs
    et al.
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA. Radboud University, Nijmegen, the Netherlands. Durham University, United Kingdom.
    Gordon, Iouli
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    van der Avoird, A.
    Radboud University, Nijmegen, the Netherlands.
    Baranov, Yury
    Institute of Experimental Meteorology, Obninsk, Russia.
    Boulet, Christian
    Université Paris-Sud, Orsay, France.
    Drouin, Brian
    Jet Propulsion Laboratory, Caltech, Pasadena, CA, USA.
    Groenenboom, Gerrit
    Radboud University, Nijmegen, the Netherlands.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hartmann, Jean-Michel
    Sorbonne Université, Palaiseau, France.
    Kurucz, Robert
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    Rothman, Laurence
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    Sun, Kang
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA. University at Buffalo, Buffalo, NY, USA.
    Sung, Keeyoon
    Jet Propulsion Laboratory, Caltech, Pasadena, CA, USA.
    Thalman, Ryan
    University of Colorado Boulder, Boulder, CO, USA. Snow College, Ephraim, UT, USA.
    Tran, Ha
    Sorbonne Université, Paris, France.
    Wishnow, Edward
    University of California Berkeley, Berkeley, CA, USA.
    Wordsworth, Robin
    Harvard University, Cambridge, MA, USA.
    Vigasin, Andrey
    Russian Academy of Sciences, Moscow, Russia.
    Volkamer, Rainer
    University of Colorado Boulder, Boulder, CO, USA.
    van der Zande, Wim
    Radboud University, Nijmegen, the Netherlands.
    Update of the HITRAN collision-induced absorption section2019In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 328, p. 160-175Article in journal (Refereed)
    Abstract [en]

    Correct parameterization of the Collision-induced Absorption (CIA) phenomena is essential for accurate modeling of planetary atmospheres. The HITRAN spectroscopic database provides these parameters in a dedicated section. Here, we significantly revise and extend the HITRAN CIA data with respect to the original effort described in Richard et al. [JQSRT 113, 1276 (2012)]. The extension concerns new collisional pairs as well as wider spectral and temperature ranges for the existing pairs. The database now contains CIA for N2N2, N2H2, N2-CH4, N2H2O, N2O2, O2O2, O2-CO2, CO2-CO2, H2H2, H2He, H2-CH4, H2H, HHe, CH4-CH4, CH4-CO2, CH4He, and CH4Ar collision pairs. The sources of data as well as their validation and selection are discussed. A wish list to eliminate remaining deficiencies or lack of data from the astrophysics perspective is also presented.

  • 10.
    Molina, Antonio
    et al.
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid. Spain.
    López, Iván
    Universidad Rey Juan Carlos, 28933 Móstoles, Madrid. Spain.
    Prieto-Ballesteros, Olga
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid. Spain.
    Fernández-Remolar, David
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. British Geological Survey, Nicker Hill, Keyworth NG12 5GG. United Kingdom.
    Ángel de Pablo, Miguel
    Universidad de Alcalá, 28871 Alcalá de Henares, Madrid. Spain.
    Gómez, Felipe
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid.
    Coogoon Valles, western Arabia Terra: Hydrological evolution of a complex Martian channel system2017In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 293, p. 27-44Article in journal (Refereed)
    Abstract [en]

    Coogoon Valles is an intricate fluvial system, and its main channel was formed during the Noachian period through the erosion of the clay-bearing basement of the Western Arabia Terra. This region is characterized by a thinner crust compared to the rest of the highlands and by the occurrence of massive phyllosilicate-bearing materials. The origin of this region is still under discussion. Its surface has been exposed to a large-scale volcanism, and several episodes of extensive denudation were primarily controlled by fluvial activity. In this regard, the study of the oldest channels in Arabia Terra is crucial for understanding the global geological evolution of early Mars. The reactivation of the hydrological system by sapping followed by aeolian erosion had reshaped the channel, as well as exposed ancient materials and landforms. The examination of the bed deposits suggests an old episode of detrital sedimentation covering the Noachian basement followed by an erosive event that formed the current Coogoon Valles configuration. A complex system of deltas and alluvial fans is situated at the termination of this channel, which has been proposed as a landing site for the upcoming ExoMars and Mars 2020 missions.

  • 11.
    Moore, Casey A.
    et al.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Moores, John E.
    York University, Toronto, Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Lemmon, Mark T.
    Texas A&M University, College Station.
    Rafkin, Scot C.R.
    Southwest Research Institute, Boulder.
    Francis, Raymond
    University of Western Ontario, Centre for Planetary Science and Exploration, University of Western Ontario, London.
    Pla-Garcia, Jorge
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Haberle, Robert
    Ames Research Centre, NASA Ames Research Center, Moffett Field.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto Nacional de Técnica Aeroespacial, Madrid, Centro de Astrobiologia, Madrid, Centro de Astrobiología (CSIC-INTA), Madrid.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Burton, John R.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    A Full Martian Year of Line-of-Sight Extinction within Gale Crater, Mars as Acquired by the MSL Navcam through sol 9002016In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 264, p. 102-108Article in journal (Refereed)
    Abstract [en]

    We report on line-of-sight extinction in northern Gale Crater, Mars as seen by the Mars Science Laboratory (MSL) rover, Curiosity from sol 100 to sol 900; a little more than an entire martian year. Navcam images oriented due north, which show the distant crater rim, the near ground and the sky allow the extinction due to dust within the crater to be determined. This line-of sight extinction is compared to a complementary dataset of column extinctions derived from Mastcam. The line-of-sight extinction within the crater is less than the column extinction for the majority of the martian year. This implies that the relatively low mixing ratio of dust within the crater as compared to the atmosphere above the crater rim persists through most of the year. This suggests relatively little mixing between the atmosphere above the crater and the atmosphere inside the crater and suggests that northern Gale Crater is a net sink of dust in the current era. The data does however show a yearly convergence of the line-of-sight extinction and the column-averaged extinction around Ls = 270° – 290°. This suggests that air above the crater mixes with air in the crater at this time, as predicted by mesoscale models. Matching line-of-sight and column extinction values are also seen around Ls ≈ 135°, a season that has only been observed once in this dataset, this is particularly interesting as the Rover Environmental Monitoring Station onboard Curiosity reports increased convective boundary layer heights in the same season.

  • 12.
    Moores, John E.
    et al.
    York University.
    Lemmon, Mark T.
    Texas A&M University.
    Kahanpää, Henrik
    Finnish Meteorological Institute.
    Rafkin, Scot C R
    Southwest Research Institute, San Antonio, Texas.
    Francis, Raymond
    University of Western Ontario.
    Pla-Garcia, Jorge
    Centro de Astrobiología, Instituto Nacional de Técnica Aeroespacial.
    Bean, Keri
    Texas A&M University.
    Haberle, Robert
    Ames Research Centre, Naval Air Station, Moffett Field.
    Newman, Claire
    Ashima Research, Pasadena.
    Mischna, Michael
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Vasavada, Ashwin R.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Juárez, Manuel de la Torre
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Rennó, Nilton
    University of Michigan.
    Bell, Jim
    Arizona State University.
    Calef, Fred
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Cantor, Bruce
    Malin Space Science Systems.
    Mcconnochie, Timothy H.
    GSFC/U Maryland.
    Harri, Ari Matti
    Finnish Meteorological Institute.
    Genzer, Maria
    Finnish Meteorological Institute.
    Wong, Michael H.
    University of Michigan.
    Smith, Michael D.
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, María-Paz
    Centro de Astrobiología, Instituto Nacional de Técnica Aeroespacial.
    Kemppinen, Osku
    Finnish Meteorological Institute.
    McCullough, Emily
    University of Western Ontario.
    Observational evidence of a suppressed planetary boundary layer in northern Gale Crater, Mars as seen by the Navcam instrument onboard the Mars Science Laboratory rover2015In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, p. 129-142Article in journal (Refereed)
    Abstract [en]

    The Navigation Cameras (Navcam) of the Mars Science Laboratory rover, Curiosity, have been used to examine two aspects of the planetary boundary layer: vertical dust distribution and dust devil frequency. The vertical distribution of dust may be obtained by using observations of the distant crater rim to derive a line-of-sight optical depth within Gale Crater and comparing this optical depth to column optical depths obtained using Mastcam observations of the solar disc. The line of sight method consistently produces lower extinctions within the crater compared to the bulk atmosphere. This suggests a relatively stable atmosphere in which dust may settle out leaving the air within the crater clearer than air above and explains the correlation in observed column opacity between the floor of Gale Crater and the higher elevation Meridiani Planum. In the case of dust devils, despite an extensive campaign only one optically thick vortex (τ=1.5±0.5×10-3) was observed compared to 149 pressure events > 0.5Pa observed in REMS pressure data. Correcting for temporal coverage by REMS and geographic coverage by Navcam still suggests 104 vortices should have been viewable, suggesting that most vortices are dustless. Additionally, the most intense pressure excursions observed on other landing sites (pressure drop >2.5Pa) are lacking from the observations by the REMS instrument. Taken together, these observations are consistent with pre-landing circulation modeling of the crater showing a suppressed, shallow boundary layer. They are further consistent with geological observations of dust that suggests the northern portion of the crater is a sink for dust in the current era.

  • 13.
    Newsom, Horton E.
    et al.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Mangold, Nicolas
    LPGN, CNRS, UMR 6112, Université Nantes.
    Kah, Linda C.
    Department of Earth and Planetary Sciences, University of Tennessee, Knoxville.
    Williams, Joshua M.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Arvidson, Ray E.
    Washington University, St. Louis.
    Stein, Nathan
    Washington University, St. Louis.
    Ollila, Ann M.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Bridges, John C.
    Space Research Centre, Department of Physics and Astronomy, University of Leicester.
    Schwenzer, Susanne P.
    Department of Physical Science, The Open University, Walton Hall, Milton Keynes.
    King, Penelope L.
    Research School of Earth Sciences, Australian National University, Canberra.
    Grant, John A.
    Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington.
    Pinet, Patrick
    Université Paul Sabatier, Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse.
    Bridges, Nathan T.
    Applied Physics Laboratory, Laurel, Maryland.
    III, Fred Calef
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Wiens, Roger C.
    Los Alamos National Laboratory.
    Spray, John G.
    Planetary and Space Science Centre, University of New Brunswick, Fredericton.
    Vaniman, David T.
    Planetary Science Institute, Tucson.
    Elston, Wolf E.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Berger, Jeff A.
    University of Western Ontario, London.
    Garvin, James B.
    NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Palucis, Marisa C.
    Department of Earth and Planetary Science, University of California, Berkeley.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Gale crater and impact processes: Curiosity's first 364 Sols on Mars2015In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, p. 108-128Article in journal (Refereed)
    Abstract [en]

    Impact processes at all scales have been involved in the formation and subsequent evolution of Gale crater. Small impact craters in the vicinity of the Curiosity MSL landing site and rover traverse during the 364 Sols after landing have been studied both from orbit and the surface. Evidence for the effect of impacts on basement outcrops may include loose blocks of sandstone and conglomerate, and disrupted (fractured) sedimentary layers, which are not obviously displaced by erosion. Impact ejecta blankets are likely to be present, but in the absence of distinct glass or impact melt phases are difficult to distinguish from sedimentary/volcaniclastic breccia and conglomerate deposits. The occurrence of individual blocks with diverse petrological characteristics, including igneous textures, have been identified across the surface of Bradbury Rise, and some of these blocks may represent distal ejecta from larger craters in the vicinity of Gale. Distal ejecta may also occur in the form of impact spherules identified in the sediments and drift material. Possible examples of impactites in the form of shatter cones, shocked rocks, and ropy textured fragments of materials that may have been molten have been observed, but cannot be uniquely confirmed. Modification by aeolian processes of craters smaller than 40 m in diameter observed in this study, are indicated by erosion of crater rims, and infill of craters with aeolian and airfall dust deposits. Estimates for resurfacing suggest that craters less than 15 m in diameter may represent steady state between production and destruction. The smallest candidate impact crater observed is ∼0.6 m in diameter. The observed crater record and other data are consistent with a resurfacing rate of the order of 10 mm/Myr; considerably greater than the rate from impact cratering alone, but remarkably lower than terrestrial erosion rates.

  • 14.
    Ortiz, J.L.
    et al.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Aceituno, F.J.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Quesada, J.A.
    Huétor Santillán Observatory, Granada.
    Aceituno, J.
    Centro Astronómico Hispano-Alemán de Calar Alto, Almería.
    Fernández, M.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Santos-Sanz, P.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Trigo-Rodríguez, J.M.
    Institut de Ciències de l'Espai (CSIC) Campus UAB, Facultat de Ciencies, Bellaterra, Institut d'Estudis Espacials de Catalunya (IEEC), Campus UAB, Facultat de Ciencies, Bellaterra.
    Llorca, J.
    Institut de Tècniques Energètiques, Univ. Politècnica de Catalunya, Barcelona, Institut d'Estudis Espacials de Catalunya (IEEC), Campus UAB, Facultat de Ciencies, Bellaterra.
    Martin-Torres, Javier
    Analytical Services and Materials Inc., Hampton.
    Montañés-Rodríguez, P.
    Big Bear Solar Observatory, New Jersey Institute of Technology, Newark.
    Pallé, E.
    Big Bear Solar Observatory, New Jersey Institute of Technology, Newark.
    Detection of sporadic impact flashes on the Moon: Implications for the luminous efficiency of hypervelocity impacts and derived terrestrial impact rates2006In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 184, no 2, p. 319-326Article in journal (Refereed)
    Abstract [en]

    We present the first redundant detection of sporadic impact flashes on the Moon from a systematic survey performed between 2001 and 2004. Our wide-field lunar monitoring allows us to estimate the impact rate of large meteoroids on the Moon as a function of the luminous energy received on Earth. It also shows that some historical well-documented mysterious lunar events fit in a clear impact context. Using these data and traditional values of the luminous efficiency for this kind of event we obtain that the impact rate on Earth of large meteoroids (0.1–10 m) would be at least one order of magnitude larger than currently thought. This discrepancy indicates that the luminous efficiency of the hypervelocity impacts is higher than 10−2, much larger than the common belief, or the latest impact fluxes are somewhat too low, or, most likely, a combination of both. Our nominal analysis implies that on Earth, collisions of bodies with masses larger than 1 kg can be as frequent as 80,000 per year and blasts larger than 15-kton could be as frequent as one per year, but this is highly dependent on the exact choice of the luminous efficiency value. As a direct application of our results, we expect that the impact flash of the SMART-1 spacecraft should be detectable from Earth with medium-sized telescopes.

  • 15.
    Orton, Glenn S.
    et al.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Fletcher, Leigh N.
    Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford.
    Moses, Julianne I.
    Space Science Institute.
    Mainzer, Amy K.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Hines, Dean
    Space Telescope Science Institute, Boulder.
    Hammel, Heidi B.
    Association of Universities for Research in Astronomy, Washington DC.
    Martin-Torres, Javier
    Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Burgdorf, Martin
    HE Space Operations.
    Merlet, Cecile
    Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford.
    Line, Michael R.
    Department of Astronomy and Astrophysics, University of California - Santa Cruz.
    Mid-infrared spectroscopy of Uranus from the Spitzer Infrared Spectrometer: 1. Determination of the mean temperature structure of the upper troposphere and stratosphere2014In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 243, p. 494-513Article in journal (Refereed)
    Abstract [en]

    On 2007 December 16-17, spectra were acquired of the disk of Uranus by the Spitzer Infrared Spectrometer (IRS), ten days after the planet's equinox, when its equator was close to the sub-Earth point. This spectrum provides the highest-resolution broad-band spectrum ever obtained for Uranus from space, allowing a determination of the disk-averaged temperature and molecule composition to a greater degree of accuracy than ever before. The temperature profiles derived from the Voyager radio occultation experiment by Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92, 14987-15001) and revisions suggested by Sromovsky et al. (Sromovsky, L.A., Fry, P.A., Kim, J.H. [2011]. Icarus 215, 292-312) that match these data best are those that assume a high abundance of methane in the deep atmosphere. However, none of these model profiles provides a satisfactory fit over the full spectral range sampled. This result could be the result of spatial differences between global and low-latitudinal regions, changes in time, missing continuum opacity sources such as stratospheric hazes or unknown tropospheric constituents, or undiagnosed systematic problems with either the Voyager radio-occultation or the Spitzer IRS data sets. The spectrum is compatible with the stratospheric temperatures derived from the Voyager ultraviolet occultations measurements by Herbert et al. (Herbert, F. et al. [1987]. J. Geophys. Res. 92, 15093-15109), but it is incompatible with the hot stratospheric temperatures derived from the same data by Stevens et al. (Stevens, M.H., Strobel, D.F., Herbert, F.H. [1993]. Icarus 101, 45-63). Thermospheric temperatures determined from the analysis of the observed H2 quadrupole emission features are colder than those derived by Herbert et al. at pressures less than ~1μbar. Extrapolation of the nominal model spectrum to far-infrared through millimeter wavelengths shows that the spectrum arising solely from H2 collision-induced absorption is too warm to reproduce observations between wavelengths of 0.8 and 3.3mm. Adding an additional absorber such as H2S provides a reasonable match to the spectrum, although a unique identification of the responsible absorber is not yet possible with available data. An immediate practical use for the spectrum resulting from this model is to establish a high-precision continuum flux model for use as an absolute radiometric standard for future astronomical observations.

  • 16.
    Orton, Glenn S.
    et al.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Gustafsson, Magnus
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Burgdorf, Martin
    Astrophysics Research Institute, Liverpool John Moores University, UK.
    Meadows, Victoria
    Spitzer Science Center, California Institute of Technology, USA.
    Revised ab initio models for H2–H2 collision-induced absorption at low temperatures2007In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 189, no 2, p. 544-549Article in journal (Refereed)
    Abstract [en]

    A revised ab initio calculation of the H2–H2 collision-induced absorption results in significant differences compared with the work of J. Borysow et al. [Borysow, J., Trafton, L., Frommhold, L., Birnbaum, G., 1985. Astrophys. J. 296, 644–654] for wavenumbers greater than 600 cm−1 and temperatures below 120 K. The revision has significant influence on the spectra of Uranus and Neptune, and essentially removes the need for models with “super-solar” helium abundances or stratospheric hazes to explain the spectrum of Uranus.

  • 17.
    Orton, Glenn S.
    et al.
    MS 183-501, Jet Propulsion Laboratory, California Institute of Technology.
    Moses, Julianne I.
    Space Science Institute.
    Fletcher, Leigh N.
    Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford.
    Mainzer, Amy K.
    MS 321-535, Jet Propulsion Laboratory, California Institute of Technology.
    Hines, Dean
    Space Telescope Science Institute, Boulder.
    Hammel, Heidi B.
    Association of Universities for Research in Astronomy, Washington DC.
    Martin-Torres, Javier
    Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Burgdorf, Martin
    HE Space Operations.
    Merlet, Cecile
    Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford.
    Line, Michael R.
    Department of Astronomy and Astrophysics, University of California - Santa Cruz.
    Mid-infrared spectroscopy of Uranus from the Spitzer infrared spectrometer: 2. Determination of the mean composition of the upper troposphere and stratosphere2014In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 243, p. 471-493Article in journal (Refereed)
    Abstract [en]

    Mid-infrared spectral observations Uranus acquired with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope are used to determine the abundances of C2H2, C2H6, CH3C2H, C4H2, CO2, and tentatively CH3 on Uranus at the time of the 2007 equinox. For vertically uniform eddy diffusion coefficients in the range 2200-2600cm2s-1, photochemical models that reproduce the observed methane emission also predict C2H6 profiles that compare well with emission in the 11.6-12.5μm wavelength region, where the υ9 band of C2H6 is prominent. Our nominal model with a uniform eddy diffusion coefficient Kzz=2430cm2s-1 and a CH4 tropopause mole fraction of 1.6×10-5 provides a good fit to other hydrocarbon emission features, such as those of C2H2 and C4H2, but the model profile for CH3C2H must be scaled by a factor of 0.43, suggesting that improvements are needed in the chemical reaction mechanism for C3Hx species. The nominal model is consistent with a CH3D/CH4 ratio of 3.0±0.2×10-4. From the best-fit scaling of these photochemical-model profiles, we derive column abundances above the 10-mbar level of 4.5+01.1/-0.8×1019molecule-cm-2 for CH4, 6.2±1.0×1016molecule-cm-2 for C2H2 (with a value 24% higher from a different longitudinal sampling), 3.1±0.3×1016molecule-cm-2 for C2H6, 8.6±2.6×1013molecule-cm-2 for CH3C2H, 1.8±0.3×1013molecule-cm-2 for C4H2, and 1.7±0.4×1013molecule-cm-2 for CO2 on Uranus. A model with Kzz increasing with altitude fits the observed spectrum and requires CH4 and C2H6 column abundances that are 54% and 45% higher than their respective values in the nominal model, but the other hydrocarbons and CO2 are within 14% of their values in the nominal model. Systematic uncertainties arising from errors in the temperature profile are estimated very conservatively by assuming an unrealistic "alternative" temperature profile that is nonetheless consistent with the observations; for this profile the column abundance of CH4 is over four times higher than in the nominal model, but the column abundances of the hydrocarbons and CO2 differ from their value in the nominal model by less than 22%. The CH3D/CH4 ratio is the same in both the nominal model with its uniform Kzz as in the vertically variable Kzz model, and it is 10% lower with the "alternative" temperature profile than the nominal model. There is no compelling evidence for temporal variations in global-average hydrocarbon abundances over the decade between Infrared Space Observatory and Spitzer observations, but we cannot preclude a possible large increase in the C2H2 abundance since the Voyager era. Our results have implications with respect to the influx rate of exogenic oxygen species and the production rate of stratospheric hazes on Uranus, as well as the C4H2 vapor pressure over C4H2 ice at low temperatures.

  • 18.
    Smith, Michael D.
    et al.
    NASA Goddard Space Flight Center.
    Mier, Maria-Paz Zorzano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Lemmon, Mark T.
    Department of Atmospheric Sciences, Texas A&M University, Texas A&M University, College Station.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Cal, Maria Teresa Mendaza de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes2016In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 280, p. 234-248Article in journal (Refereed)
    Abstract [en]

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately 1.75 Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

  • 19.
    Ullán, Aurora
    et al.
    Departamento de Teoría de la Señal y Comunicaciones, Escuela Politécnica Superior , Universidad de Alcalá, Madrid.
    Zorzano Mier, Maria-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Valentin-Serrano, Patricia
    nstituto Andaluz de Ciencias de la Tierra (CSIC - UGR), Granada.
    Kahanpää, Henrik
    Finnish Meteorological Institute, Helsinki.
    Harri, Ari-Matti
    Finnish Meteorological Institute, Helsinki.
    Gómez-Elvira, Javier
    Centro de Astrobiologí a (CSIC-INTA), Torrejón de Ardoz, Madrid.
    Navarro, Sara
    Centro de Astrobiología (CSIC - INTA), Torrejón de Ardoz, Madrid.
    Analysis of wind-induced dynamic pressure fluctuations during one and a half Martian years at Gale Crater2017In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 288, p. 78-87Article in journal (Refereed)
    Abstract [en]

    The Rover Environmental Monitoring Station (REMS) instrument on-board the Mars Science Laboratory (MSL) has acquired unprecedented measurements of key environmental variables at the base of Gale Crater. The pressure measured by REMS shows modulations with a very structured pattern of short-time scale (of the order of seconds to several minutes) mild fluctuations (typically up to 0.2 Pa at daytime and 1 Pa at night-time). These dynamic pressure oscillations are consistent with wind, air and ground temperature modulations measured simultaneously by REMS. We detect the signals of a repetitive pattern of upslope/downslope winds, with maximal speeds of about 21 m/s, associated with thermal changes in the air and surface temperatures, that are initiated after sunset and finish with sunrise proving that Gale, a 4.5 km deep impact crater, is an active Aeolian environment. At nighttime topographic slope winds are intense with maximal activity from 17:00 through 23:00 Local Mean Solar Time, and simultaneous changes of surface temperature are detected. During the day, the wind modulations are related to convection of the planetary boundary layer, winds are softer with maximum wind speed of about 14 m/s. The ground temperature is modulated by the forced convection of winds, with amplitudes between 0.2 K and 0.5 K, and the air temperatures fluctuate with amplitudes of about 2 K. The analysis of more than one and a half Martian years indicates the year-to-year repeatability of these environmental phenomena. The wind pattern minimizes at the beginning of the south hemisphere winter (Ls 90) season and maximizes during late spring and early summer (Ls 270). The procedure that we present here is a useful tool to investigate in a semi-quantitative way the winds by: i) filling both seasonal and diurnal gaps where wind measurements do not exist, ii) providing an alternative way for comparisons through different measuring principia and, iii) filling the gap of observation of short time-wind variability, where the REMS wind-sensor is blind

  • 20.
    Zorzano, María Paz
    et al.
    Centro de Astrobiología (CSIC-INTA), Instituto Nacional de Técnica Aeroespacial (INTA).
    Cordoba-Jabonero, Carmen
    nst Nacl Tecn Aeroespacial, Dept Observ Tierra.
    Influence of aerosol multiple scattering of ultraviolet radiation on martian atmospheric sensing2007In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 190, no 2, p. 492-503Article in journal (Refereed)
    Abstract [en]

    The ultraviolet (UV) radiative transfer problem in the martian atmosphere is dominated by multiple scattering of photons with the micronsized aerosols that are suspended in the thin atmosphere. By implementing a multiple stream, vertical fine layering description of the radiative transfer equation that is able to cope with the strong vertical variations of the atmospheric properties, we estimate the resulting upwelling and downwelling UV irradiances under different martian scenarios in equatorial and close to equatorial latitudes. We include the latest SPICAM measurements on the aerosol vertical profile (distribution of Angstrom exponent and aerosol loading), scattering properties (asymmetry parameter and single scattering albedo), ground albedo, and 03 content as well as MER long-term monitorization of ground-based aerosol optical depth. We show that due to the fact that the distributions of absorbing (ozone) and scattering (aerosols) agents are vertically coincident, the probability to absorb a photon following a multiple scattered trajectory is increased. One can thus best deteetweak ozone absorption signatures in the upwelling and downwelling diffuse irradiances. However as it is later shown, the absorption signature in the diffuse irradiance field and for a given total ozone column, changes with the total aerosol content and its vertical profile. This must be taken into account in order not to overestimate the total ozone column. It is shown that typical dust scenarios such as those seen by the MER long-term monitorization of ground-based aerosol optical depth, tau approximate to 0.45 and 0.9, produce UV nadir viewing reflectance values of the order of 0.02 and 0.04, respectively, which are comparable with those actually measured by Mars Express. For these scenarios, more than 75% of the upwelling irradiance at the top of the atmosphere (TOA) is backscattered by atmospheric aerosols alone, the rest being reflected by the low albedo ground. Depending on the aerosol vertical distribution, the ozone absorption signature may be changed by a factor of two. Finally we also show that the upwelling irradiance depends also on the ground altitude. In the future, this work may be useful to link in situ, ground-based UV measurements, with simultaneous satellite nadir measurements as well as to extract relevant atmospheric information from the irradiance measurements

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