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J. Benson, B. Bonev, P. James, K. Shan, B. Cantor, M. Caplinger ICARUS

The Seasonal Behavior of Water Ice Clouds in the Tharsis and Valles Marineris Regions of Mars: Mars Obiter Camera Observations. J. Benson, B. Bonev, P. James, K. Shan, B. Cantor, M. Caplinger ICARUS. Presented by Kate Hale 12/9/04. Outline. Objectives of the study

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J. Benson, B. Bonev, P. James, K. Shan, B. Cantor, M. Caplinger ICARUS

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  1. The Seasonal Behavior of Water Ice Clouds in the Tharsis and Valles Marineris Regions of Mars: Mars Obiter Camera Observations J. Benson, B. Bonev, P. James, K. Shan, B. Cantor, M. Caplinger ICARUS Presented by Kate Hale 12/9/04

  2. Outline • Objectives of the study • Why is the study important? • Description of technique • Data • Results

  3. Objectives • Quantify seasonal variations of cloud characteristics associated with certain topographical features (canyons and volcanoes) • Determine periodicities in data • Estimate cloud top height • Determine optical depth of observed clouds to estimate their water content

  4. Why is this study important? Past Studies: • Ground based • Mariners 6, 7 & 9 • Viking • Hubble Space Telescope ALL LIMITED None able to perform continuous, daily monitoring

  5. Techniques of the study • Data taken from March 15 1999, to July 31, 2001 • Mars Orbital Camera took images in both red and blue bandpass range • In blue the ice clouds appear very bright (high scattering albedo) separating them from the darker dust clouds • In 24-hr period a complete global map is obtained of resolution = 7.5 km/pixel (Daily Global Maps) • However some missing data at times due to solar conjunction and incomplete data reception at Deep Space Network (~19 Martian days) • Visually located areas of high cloud density, then matched with blue images and cloud area measured • Thermal Emission Spectrometer (TES) data complemented visual images

  6. Data - 4 Tharsis region volcanoes From (D) Formed from upward slope of volcano Ripple “W” cloud (large, bright, limb clouds) From (C) • Arsia Mons (1˚S, 130˚W by 10˚S, 110˚W)* May 2001 • Alba Patera (50˚N, 128˚W by 30˚N, 99˚W)*Dec 2000 • Ascraeus Mons (25˚N, 129˚W by 2˚N, 88.5˚W)*February 2001 • Pavonis Mons (11˚N, 127˚W by 8˚S, 105˚W)*February 2001 *Window coordinates: (left top, right bottom)

  7. Data- Seasonal for Volcanoes Aerocentric Longitude: Angle of Mars in its orbit around the sun, measured from the vernal equinox (Ls = 0 starting northern hemisphere’s Spring season) Observations: - Olympus and Ascraeus are similar - Arsia has constant cover - Pavonis Mons had double peak

  8. Alba Patera • Alba Patera also has double peak (highest peak at 1.2 million km2) • Anticorrelated with Olympus and Ascraeus

  9. Data • Cloud height taken for several days throughout cloudy season. • - Visual inspection of position relative to volcano compared against topographical maps of the volcanoes • Cloud optical depth was calculated from blue images and the radiance (albedo) of the clouds using the 3 layer model which was used in modeling Hubble’s observations. • - Observed radiance compared with outside point surface albedo • - TES data used to estimate dust optical depth • Water column abundances were calculated from final calculated cloud depths

  10. Results • Overlapping of data shows that there is seasonal repeatability for the Tharsis volcanoes, Olympus Mons, and Alba Patera • Cloud area on short scale (< 10-15 sols) intensifies in both size and thickness as the day progresses • Clouds at Valles Marineris are in form of haze from Spring to mid-Summer, then small discrete clouds until end of Summer. • Cloud heights increase as day progresses • Range for Alba Patera 5.5 – 6.5 km compared to • Olympus Mons 19 – 21 km • H2O abundances range from .080 - .820 pr μm for Arsia Mons to .101 – 1.358 pr μm (pr μm = precipitable microns)

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