2017
| Title: | The Vertical Dust Profile Over Gale Crater, Mars |
|---|---|
| Authors: | Guzewich, Scott D.; Newman, C. E.; Smith, M. D.; Moores, J. E.; Smith, C. L.; Moore, C.; Richardson, M. I.; Kass, D.; Kleinböhl, A.; Mischna, M.; Martín-Torres, F. J.; Zorzano-Mier, M.-P.; Battalio, M. |
| Affiliation: | AA(NASA Goddard Spaceflight Center, Greenbelt, MD USA), AB(Aeolis Research, Pasadena, CA USA), AC(NASA Goddard Spaceflight Center, Greenbelt, MD USA), AD(Department of Earth and Space Science and Engineering, York University, Toronto, ON Canada), AE(Department of Earth and Space Science and Engineering, York University, Toronto, ON Canada), AF(Department of Earth and Space Science and Engineering, York University, Toronto, ON Canada), AG(Aeolis Research, Pasadena, CA USA), AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA), AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA), AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA), AK(Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden; Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain), AL(Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden; Centro de Astrobiología (INTA-CSIC), Madrid, Spain), AM(Department of Atmospheric Sciences, Texas A&M University, College Station, TX USA) |
| Journal: | Journal of Geophysical Research: Planets, Volume 122, Issue 12, pp. 2779-2792. |
| Publication Date: | Dec 2017 |
| Origin: | American Geophysical Union (AGU) |
| Keywords: | Mars, atmosphere, dust, Curiosity, MSL, Gale Crater |
| Abstract Copyright: | ©2017. American Geophysical Union. All Rights Reserved. |
| DOI: | https://doi.org/10.1002/2017JE005420 |
| Bibliographic Code: | 2017JGRE..122.2779G |
| Abstract: | We create a vertically coarse, but complete, profile of dust mixing ratio from the surface to the upper atmosphere over Gale Crater, Mars, using the frequent joint atmospheric observations of the orbiting Mars Climate Sounder (MCS) and the Mars Science Laboratory Curiosity rover. Using these data and an estimate of planetary boundary layer (PBL) depth from the MarsWRF general circulation model, we divide the vertical column into three regions. The first region is the Gale Crater PBL, the second is the MCS-sampled region, and the third is between these first two. We solve for a well-mixed dust mixing ratio within this third (middle) layer of atmosphere to complete the profile. We identify a unique seasonal cycle of dust within each atmospheric layer. Within the Gale PBL, dust mixing ratio maximizes near southern hemisphere summer solstice (L<SUB>s</SUB> = 270°) and minimizes near winter solstice (L<SUB>s</SUB> = 90-100°) with a smooth sinusoidal transition between them. However, the layer above Gale Crater and below the MCS-sampled region more closely follows the global opacity cycle and has a maximum in opacity near L<SUB>s</SUB> = 240° and exhibits a local minimum (associated with the "solsticial pause" in dust storm activity) near L<SUB>s</SUB> = 270°. With knowledge of the complete vertical dust profile, we can also assess the frequency of high-altitude dust layers over Gale. We determine that 36% of MCS profiles near Gale Crater contain an "absolute" high-altitude dust layer wherein the dust mixing ratio is the maximum in the entire vertical column. |
| Title: | Martian sand sheet characterization and implications for formation: A case study |
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| Authors: | Runyon, Kirby D.; Bridges, Nathan T.; Newman, Claire E. |
| Affiliation: | AA(Johns Hopkins University Department of Earth and Planetary Sciences, 301 Olin Hall, 3400N. Charles Street, Baltimore, MD 21218, USA), AB(Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA), AC(Aeolis Research, 600N. Rosemead Blvd., Suite 205, Pasadena, CA 91107, USA) |
| Journal: | Aeolian Research, Volume 29, p. 1-11. |
| Publication Date: | Dec 2017 |
| Origin: | Elsevier BV |
| Abstract Copyright: | (c) 2017 Elsevier B.V. |
| DOI: | https://doi.org/10.1016/j.aeolia.2017.09.001 |
| Bibliographic Code: | 2017AeoRe..29....1R |
| Abstract: | Windblown sand and dust dominate surface geologic processes in Mars' current environment. Besides sand dune fields, areally extensive sand sheets are common across Mars, blanketing the underlying topography with several meters of rippled sand. Earth's sand sheets commonly form upwind or cross-wind to dunes and both partially trap and source sediment to downwind dunes. In contrast, Mars' sheets are frequently located downwind of active barchan and dome sand dunes, suggesting they cannot be a sediment source for the dunes as on Earth. Here, we characterize a Martian sand sheet and its geologic context, model the regional atmospheric circulation, and more broadly consider the implications for sand sheet formation on Mars. Our case study sand sheet in central Herschel Crater is < 5 m thick, with an upwind margin forming in the lee of topographic obstacles such as dunes, crater rims, and small hills. The sheet has actively migrating superposing ripples with estimated total sand fluxes comparable to total fluxes measured from slip faces on local, regional, and global dunes, some of which have eroded away. A smooth geologic unit interpreted as outcrops of paleo-sand sheets is adjacent to the active sheets. Our observations and atmospheric modeling-which predict wind shear stresses above the sand suspension threshold-indicate that the upwind dunes may be eroding and their sand deposited downwind in sheets in what may be a cyclical process, possibly related to Mars' axial obliquity cycles. |
| Title: | Martian aeolian activity at the Bagnold Dunes, Gale Crater: The view from the surface and orbit |
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| Authors: | Bridges, N. T.; Sullivan, R.; Newman, C. E.; Navarro, S.; van Beek, J.; Ewing, R. C.; Ayoub, F.; Silvestro, S.; Gasnault, O.; Le Mouélic, S.; Lapotre, M. G. A.; Rapin, W. |
| Affiliation: | AA(Applied Physics Laboratory, Laurel, Maryland USA;), AB(Cornell Center for Astrophysics and Planetary Sciences, Cornell University, Ithaca, New York USA), AC(Aeolis Research, Pasadena, California USA), AD(Instituto Nacional de Técnica Aeroespacial, Torrejon de Ardoz, Spain), AE(Malin Space Science Systems, San Diego, California USA), AF(Department of Geology and Geophysics, Texas A&M University, College Station, Texas USA), AG(Jet Propulsion Laboratory, Pasadena, California USA), AH(Osservatorio Astronomico Capodimonte, Naples, Italy; SETI Institute, Carl Sagan Center, Mountain View, California, USA), AI(Centre National de la Recherche Scientifique, Institut de Recherche en Astrophysique et Planétologie, CNRS-Université Toulouse, Toulouse, France), AJ(Laboratoire de Planétologie et Géodynamique de Nantes, CNRS, UMR 6112, Université de Nantes, Nantes, France), AK(California Institute of Technology, Pasadena, California USA), AL(Centre National de la Recherche Scientifique, Institut de Recherche en Astrophysique et Planétologie, CNRS-Université Toulouse, Toulouse, France; California Institute of Technology, Pasadena, California USA) |
| Journal: | Journal of Geophysical Research: Planets, Volume 122, Issue 10, pp. 2077-2110. |
| Publication Date: | Oct 2017 |
| Origin: | American Geophysical Union (AGU) |
| Keywords: | Mars, dunes, Curiosity, wind, HiRISE, change detection |
| Abstract Copyright: | ©2017. American Geophysical Union. All Rights Reserved. |
| DOI: | https://doi.org/10.1002/2017JE005263 |
| Bibliographic Code: | 2017JGRE..122.2077B |
| Abstract: | The first in situ investigation of an active dune field on another planetary surface occurred in 2015-2016 when the Mars Science Laboratory Curiosity rover investigated the Bagnold Dunes on Mars. High Resolution Imaging Science Experiment images show clear seasonal variations that are in good agreement with atmospheric model predictions of intra-annual sand flux and migration directions that together indicate that the campaign occurred during a period of low wind activity. Curiosity surface images show that limited changes nevertheless occurred, with movement of large grains, particularly on freshly exposed surfaces, two occurrences of secondary grain flow on the slip face of Namib Dune, and a slump on a freshly exposed surface of a large ripple. These changes are seen at Martian solar day (sol)-to-sol time scales. Grains on a rippled sand deposit and unconsolidated dump piles show limited movement of large grains over a few hours during which mean friction speeds are estimated at 0.3-0.4 m s<SUP>-1</SUP>. Overall, the correlation between changes and peak Rover Environmental Monitoring Station (REMS) winds is moderate, with high wind events associated with changes in some cases, but not in others, suggesting that other factors are also at work. The distribution of REMS 1 Hz wind speeds shows a significant tail up to the current 20 m s<SUP>-1</SUP> calibration limit, indicating that even higher speed winds occur. Nonaeolian triggering mechanisms are also possible. The low activity period at the dunes documented by Curiosity provides clues to processes that dominated in the Martian past under conditions of lower obliquity. |
| Title: | The Modern Near-Surface Martian Climate: A Review of In-situ Meteorological Data from Viking to Curiosity |
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| Authors: | Martínez, G. M.; Newman, C. N.; De Vicente-Retortillo, A.; Fischer, E.; Renno, N. O.; Richardson, M. I.; Fairén, A. G.; Genzer, M.; Guzewich, S. D.; Haberle, R. M.; Harri, A.-M.; Kemppinen, O.; Lemmon, M. T.; Smith, M. D.; de la Torre-Juárez, M.; Vasavada, A. R. |
| Affiliation: | AA(Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA), AB(Aeolis Research, Pasadena, CA, USA), AC(Departamento de Física de la Tierra, Astronomía y Astrofísica II, Universidad Complutense de Madrid, Madrid, Spain), AD(Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA), AE(Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA), AF(Aeolis Research, Pasadena, CA, USA), AG(Centro de Astrobiología (CSIC-INTA), Madrid, Spain; Department of Astronomy, Cornell University, Ithaca, NY, USA), AH(Earth Observation, Finnish Meteorological Institute, Helsinki, Finland), AI(NASA Goddard Space Flight Center, Greenbelt, MD, USA), AJ(Space Science Division, NASA Ames Research Center, Moffett Field, CA, USA), AK(Earth Observation, Finnish Meteorological Institute, Helsinki, Finland), AL(Department of Physics, Kansas State University, Manhattan, KS, USA), AM(Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA), AN(NASA Goddard Space Flight Center, Greenbelt, MD, USA), AO(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA), AP(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA) |
| Journal: | Space Science Reviews, Volume 212, Issue 1-2, pp. 295-338. |
| Publication Date: | Oct 2017 |
| Origin: | Springer Science and Business Media LLC |
| Keywords: | Mars, Atmosphere, Climate, Meteorology |
| Abstract Copyright: | (c) 2017: The Author(s) |
| DOI: | https://doi.org/10.1007/s11214-017-0360-x |
| Bibliographic Code: | 2017SSRv..212..295M |
| Abstract: | We analyze the complete set of in-situ meteorological data obtained from the Viking landers in the 1970s to today's Curiosity rover to review our understanding of the modern near-surface climate of Mars, with focus on the dust, CO<SUB>2</SUB> and H<SUB>2</SUB>O cycles and their impact on the radiative and thermodynamic conditions near the surface. In particular, we provide values of the highest confidence possible for atmospheric opacity, atmospheric pressure, near-surface air temperature, ground temperature, near-surface wind speed and direction, and near-surface air relative humidity and water vapor content. Then, we study the diurnal, seasonal and interannual variability of these quantities over a span of more than twenty Martian years. Finally, we propose measurements to improve our understanding of the Martian dust and H<SUB>2</SUB>O cycles, and discuss the potential for liquid water formation under Mars' present day conditions and its implications for future Mars missions. Understanding the modern Martian climate is important to determine if Mars could have the conditions to support life and to prepare for future human exploration. |
| Title: | Winds measured by the Rover Environmental Monitoring Station (REMS) during the Mars Science Laboratory (MSL) rover's Bagnold Dunes Campaign and comparison with numerical modeling using MarsWRF |
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| Authors: | Newman, Claire E.; Gómez-Elvira, Javier; Marin, Mercedes; Navarro, Sara; Torres, Josefina; Richardson, Mark I.; Battalio, J. Michael; Guzewich, Scott D.; Sullivan, Robert; de la Torre, Manuel; Vasavada, Ashwin R.; Bridges, Nathan T. |
| Affiliation: | AA(Aeolis Research, Pasadena, CA 91107, USA), AB(Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain), AC(Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain), AD(Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain), AE(Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain), AF(Aeolis Research, Pasadena, CA 91107, USA), AG(Texas A&M University, College Station, TX 77843, USA), AH(NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), AI(Cornell University, Ithaca, NY 14853, USA), AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA), AK(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA), AL(Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA) |
| Journal: | Icarus, Volume 291, p. 203-231. |
| Publication Date: | Jul 2017 |
| Origin: | Elsevier BV |
| Abstract Copyright: | (c) 2017 Elsevier Inc. |
| DOI: | https://doi.org/10.1016/j.icarus.2016.12.016 |
| Bibliographic Code: | 2017Icar..291..203N |
| Abstract: | A high density of REMS wind measurements were collected in three science investigations during MSL's Bagnold Dunes Campaign, which took place over ∼80 sols around southern winter solstice (Ls∼90°) and constituted the first in situ analysis of the environmental conditions, morphology, structure, and composition of an active dune field on Mars. The Wind Characterization Investigation was designed to fully characterize the near-surface wind field just outside the dunes and confirmed the primarily upslope/downslope flow expected from theory and modeling of the circulation on the slopes of Aeolis Mons in this season. The basic pattern of winds is 'upslope' (from the northwest, heading up Aeolis Mons) during the daytime (∼09:00-17:00 or 18:00) and 'downslope' (from the southeast, heading down Aeolis Mons) at night (∼20:00 to some time before 08:00). Between these times the wind rotates largely clockwise, giving generally westerly winds mid-morning and easterly winds in the early evening. The timings of these direction changes are relatively consistent from sol to sol; however, the wind direction and speed at any given time shows considerable intersol variability. This pattern and timing is similar to predictions from the MarsWRF numerical model, run at a resolution of ∼490 m in this region, although the model predicts the upslope winds to have a stronger component from the E than the W, misses a wind speed peak at ∼09:00, and under-predicts the strength of daytime wind speeds by ∼2-4 m/s. The Namib Dune Lee Investigation reveals 'blocking' of northerly winds by the dune, leaving primarily a westerly component to the daytime winds, and also shows a broadening of the 1 Hz wind speed distribution likely associated with lee turbulence. The Namib Dune Side Investigation measured primarily daytime winds at the side of the same dune, in support of aeolian change detection experiments designed to put limits on the saltation threshold, and also appears to show the influence of the dune body on the local flow, though less clearly than in the lee. Using a vertical grid with lower resolution near the surface reduces the relative strength of nighttime winds predicted by MarsWRF and produces a peak in wind speed at ∼09:00, improving the match to the observed diurnal variation of wind speed, albeit with an offset in magnitude. The annual wind field predicted using this grid also provides a far better match to observations of aeolian dune morphology and motion in the Bagnold Dunes. However, the lower overall wind speeds than observed and disagreement with the observed wind direction at ∼09:00 suggest that the problem has not been solved and that alternative boundary layer mixing schemes should be explored which may result in more mixing of momentum down to the near-surface from higher layers. These results demonstrate a strong need for in situ wind data to constrain the setup and assumptions used in numerical models, so that they may be used with more confidence to predict the circulation at other times and locations on Mars. |
| Title: | An integrated model for dune morphology and sand fluxes on Mars |
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| Authors: | Runyon, K. D.; Bridges, N. T.; Ayoub, F.; Newman, C. E.; Quade, J. J. |
| Affiliation: | AA(Johns Hopkins University, Department of Earth and Planetary Sciences, 301 Olin Hall, 3400 N. Charles Street, Baltimore, MD 21218, USA), AB(Johns Hopkins University, Applied Physics Laboratory, Planetary Exploration Group, 11101 Johns Hopkins Road, Laurel, MD 20723, USA), AC(Geological and Planetary Sciences, California Institute of Technology, MC 100-23, Pasadena, CA 91125, USA), AD(Aeolis Research, 600 N. Rosemead Blvd., Suite 205, Pasadena, CA 91107, USA), AE(University of Maryland, James A. Clark School of Engineering, 4611 College Ave, College Park, MD 20740, USA) |
| Journal: | Earth and Planetary Science Letters, Volume 457, p. 204-212. |
| Publication Date: | Jan 2017 |
| Origin: | Elsevier BV |
| Keywords: | aeolian, Mars, climate, stratigraphy, surface processes, GCM |
| Abstract Copyright: | (c) 2017 Elsevier Science B.V. All rights reserved. |
| DOI: | https://doi.org/10.1016/j.epsl.2016.09.054 |
| Bibliographic Code: | 2017E&PSL.457..204R |
| Abstract: | The transport and deposition of sand is the most prevalent agent of landscape modification on Mars today, with fluxes comparable to some sand dunes on Earth. Until now, the relationship between sand flux and dune field morphology has been poorly constrained. By tracking dune movement over ∼10 km-long dune fields in Herschel Crater and Nili Patera, representative of many dune fields on Mars, we find a downwind flux decrease that correlates with a sequence of changing morphology from barchans to barchanoids and seifs (longitudinal dunes) to isolated dome dunes and ending with sand sheets. We show empirical consistency with atmospheric Internal Boundary Layer (IBL) theory which can describe these broad flux and morphology changes in Martian dune fields. Deviations from IBL flux predictions are from wind streamline compressions up slopes, leading to a speedup effect. By establishing a dune field morphology type example and correlating it with measured and predicted flux changes, we provide an integrated morphology and flux model that can be applied to other areas of Mars and be used to infer paleo-environmental conditions from preserved sandstone. |
2016
| Title: | Winds measured by the Rover Environmental Monitoring Station (REMS) during Curiosity's Bagnold Dunes Campaign |
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| Authors: | Newman, Claire E.; Gomez-Elvira, Javier; Navarro Lopez, Sara; Marin Jimenez, Mercedes; Torres Redondo, Josefina; Richardson, Mark I. |
| Affiliation: | AA(Aeolis Research), AB(Centro de Astrobiologia), AC(Centro de Astrobiologia), AD(Centro de Astrobiologia), AE(Centro de Astrobiologia), AF(Aeolis Research) |
| Journal: | American Astronomical Society, DPS meeting #48, id.210.02 |
| Publication Date: | Oct 2016 |
| Origin: | AAS |
| Abstract Copyright: | (c) 2016: American Astronomical Society |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2016.12.016http://bit.ly/2ohyIZJ |
| Bibliographic Code: | 2016DPS....4821002N |
| Abstract: | Curiosity's damaged wind sensor has trouble measuring winds coming from behind the rover, due to the loss of its side-pointing boom during landing. During the Bagnold Dunes Campaign, however, the rover was turned to permit measurements of winds from missing directions, capturing upslope/downslope day-night flow on the slopes of Aeolis Mons and blocking of wind in the lee of a dune.The rover's heading is generally determined by the drive direction and often varies little over many tens of sols. Good wind measurements are made when the wind comes from the hemisphere to the front of the rover, but there are sometimes long periods during which winds from certain directions (i.e., at certain times of sol) are largely missed. Since rover turns are often precluded by rover safety and other operational constraints, it is usually not possible to turn to measure such winds properly.During the Bagnold Dunes Campaign, wind measurements were prioritized to provide context for aeolian dune studies. Rover headings were optimized for three wind investigations covering a period of about 90 sols. The first investigation characterized the wind field on approach to the dunes, with the rover turned to face two unusual headings for several sols each and monitoring focused on the 'missing' winds / times of sol. This confirmed the expected primary wind pattern of daytime roughly upslope winds (from ~NW/N) and nighttime downslope winds (from ~S/SE) on the slopes of Aeolis Mons, with significant sol-to-sol variability in e.g. the timing of the reversals. Comparison with the previous year suggests an increasingly upslope-downslope pattern as Curiosity approached the slope.The second investigation studied changes to the wind pattern in the lee of the Namib Dune. This revealed the blocking of northerly winds by the large dune, leaving primarily a westerly component to the daytime winds with weaker wind speeds.The third investigation characterized the wind field at the side of Namib Dune. The rover heading was chosen to optimize daytime winds, in support of 'change detection' experiments that were designed to correlate strong winds with changes in surface grain positions imaged over periods ranging from a few hours to several sols. |
| Title: | The influence of subsurface flow on lake formation and north polar lake distribution on Titan |
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| Authors: | Horvath, David G.; Andrews-Hanna, Jeffrey C.; Newman, Claire E.; Mitchell, Karl L.; Stiles, Bryan W. |
| Affiliation: | AA(Colorado School of Mines, Department of Geophysics and Center for Space Resources, 1500 Illinois Street, Golden, CO 80401, USA), AB(Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, USA), AC(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA), AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA) |
| Journal: | Icarus, Volume 277, p. 103-124. |
| Publication Date: | Oct 2016 |
| Origin: | ELSEVIER |
| Keywords: | Titan, hydrology, surface |
| Abstract Copyright: | (c) 2016 Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2016.04.042http://bit.ly/2oDPIqa |
| Bibliographic Code: | 2016Icar..277..103H |
| Abstract: | Observations of lakes, fluvial dissection of the surface, rapid variations in cloud cover, and lake shoreline changes indicate that Saturn's moon Titan is hydrologically active, with a hydrocarbon-based hydrological cycle dominated by liquid methane. Here we use a numerical model to investigate the Titan hydrological cycle - including surface, subsurface, and atmospheric components - in order to investigate the underlying causes of the observed distribution and sizes of lakes in the north polar region. The hydrocarbon-based hydrological cycle is modeled using a numerical subsurface flow model and analytical runoff scheme, driven by a general circulation model with an active methane-cycle. This model is run on synthetically generated topography that matches the fractal character of the observed topography, without explicit representation of the effects of erosion and deposition. At the scale of individual basins, intermediate to high permeability (10-8-10-6 cm2) aquifers are required to reproduce the observed large stable lakes. However, at the scale of the entire north polar lake district, a high permeability aquifer results in the rapid flushing of methane through the aquifer from high polar latitudes to dry lower polar latitudes, where methane is removed by evaporation, preventing large lakes from forming. In contrast, an intermediate permeability aquifer slows the subsurface flow from high polar latitudes, allowing greater lake areas. The observed distribution of lakes is best matched by either a uniform intermediate permeability aquifer, or a combination of a high permeability cap at high latitudes surrounded by an intermediate permeability aquifer at lower latitudes, as could arise due to karstic processes at the north pole. The stability of Kraken Mare further requires reduction of the evaporation rate over the sea to 1% of the value predicted by the general circulation model, likely as a result of dissolved ethane, nitrogen, or organic solutes, and/or a climatic lake effect. These results reveal that subsurface flow through aquifers plays an important role in Titan's hydrological cycle, and exerts a strong influence over the distribution, size, and volatile budgets of Titan's lakes. |
| Title: | Variations in Titan's dune orientations as a result of orbital forcing |
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| Authors: | McDonald, George D.; Hayes, Alexander G.; Ewing, Ryan C.; Lora, Juan M.; Newman, Claire E.; Tokano, Tetsuya; Lucas, Antoine; Soto, Alejandro; Chen, Gang |
| Affiliation: | AA(School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30308, USA), AB(Department of Astronomy, Cornell University, Ithaca, NY 14853, USA), AC(Department of Geology and Geophysics, Texas A&M University, College Station, TX 77840, USA), AD(Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA), AE(Ashima Research, Pasadena, CA 91001, USA), AF(Institut für Geophysik und Meteorologie, Universität zu Köln, 50923 Köln, Germany), AG(AIM CEA-Saclay, Paris VII-Denis Diderot University, Paris 75013, France), AH(Southwest Research Institute, Boulder, CO 80032, USA), AI(Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA) |
| Journal: | Icarus, Volume 270, p. 197-210. |
| Publication Date: | May 2016 |
| Origin: | ELSEVIER |
| Keywords: | Titan, Titan, surface, Titan, atmosphere, Atmospheres, dynamics |
| Abstract Copyright: | (c) 2016 Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2015.11.036http://bit.ly/2bk6dBp |
| Bibliographic Code: | 2016Icar..270..197M |
| Abstract: | Wind-blown dunes are a record of the climatic history in Titan's equatorial region. Through modeling of the climatic conditions associated with Titan's historical orbital configurations (arising from apsidal precessions of Saturn's orbit), we present evidence that the orientations of the dunes are influenced by orbital forcing. Analysis of 3 Titan general circulation models (GCMs) in conjunction with a sediment transport model provides the first direct intercomparison of results from different Titan GCMs. We report variability in the dune orientations predicted for different orbital epochs of up to 70°. Although the response of the GCMs to orbital forcing varies, the orbital influence on the dune orientations is found to be significant across all models. Furthermore, there is near agreement among the two models run with surface topography, with 3 out of the 5 dune fields matching observation for the most recent orbital cycle. Through comparison with observations by Cassini, we find situations in which the observed dune orientations are in best agreement with those modeled for previous orbital configurations or combinations thereof, representing a larger portion of the cycle. We conclude that orbital forcing could be an important factor in governing the present-day dune orientations observed on Titan and should be considered when modeling dune evolution. |
| Title: | Atmospheric tides in Gale Crater, Mars |
|---|---|
| Authors: | Guzewich, Scott D.; Newman, C. E.; de la Torre Juárez, M.; Wilson, R. J.; Lemmon, M.; Smith, M. D.; Kahanpää, H.; Harri, A.-M. |
| Affiliation: | AA(CRESST and Planetary Systems Laboratory, NASA/GSFC, Greenbelt, MD 20771, United States), AB(Ashima Research, Pasadena, CA 91106, United States), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States), AD(Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08540, United States), AE(Texas A&M University, College Station, TX 77843, United States), AF(Planetary Systems Laboratory, NASA/GSFC, Greenbelt, MD 20771, United States), AG(Finnish Meteorological Institute, Helsinki, Finland), AH(Finnish Meteorological Institute, Helsinki, Finland) |
| Journal: | Icarus, Volume 268, p. 37-49. |
| Publication Date: | Apr 2016 |
| Origin: | ELSEVIER |
| Keywords: | Mars, atmosphere, Atmospheres, dynamics, Meteorology |
| Abstract Copyright: | (c) 2016 Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2015.12.028http://bit.ly/2boX8dS |
| Bibliographic Code: | 2016Icar..268...37G |
| Abstract: | Atmospheric tides are the primary source of daily air pressure variation at the surface of Mars. These tides are forced by solar heating of the atmosphere and modulated by the presence of atmospheric dust, topography, and surface albedo and thermal inertia. This results in a complex mix of sun-synchronous and non-sun-synchronous tides propagating both eastward and westward around the planet in periods that are integer fractions of a solar day. The Rover Environmental Monitoring Station on board the Mars Science Laboratory has observed air pressure at a regular cadence for over 1 Mars year and here we analyze and diagnose atmospheric tides in this pressure record. The diurnal tide amplitude varies from 26 to 63 Pa with an average phase of 0424 local true solar time, while the semidiurnal tide amplitude varies from 5 to 20 Pa with an average phase of 0929. We find that both the diurnal and semidiurnal tides in Gale Crater are highly correlated to atmospheric opacity variations at a value of 0.9 and to each other at a value of 0.77, with some key exceptions occurring during regional and local dust storms. We supplement our analysis with MarsWRF general circulation modeling to examine how a local dust storm impacts the diurnal tide in its vicinity. We find that both the diurnal tide amplitude enhancement and regional coverage of notable amplitude enhancement linearly scales with the size of the local dust storm. Our results provide the first long-term record of surface pressure tides near the martian equator. |
| Title: | Simulating Titan's methane cycle with the TitanWRF General Circulation Model |
|---|---|
| Authors: | Newman, Claire E.; Richardson, Mark I.; Lian, Yuan; Lee, Christopher |
| Affiliation: | AA(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA), AB(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA 0000-0001-9633-4141), AC(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA), AD(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA) |
| Journal: | Icarus, Volume 267, p. 106-134. |
| Publication Date: | Mar 2016 |
| Origin: | ELSEVIER |
| Keywords: | Titan, Titan, atmosphere, Atmospheres, dynamics, Atmospheres, structure, Meteorology |
| Abstract Copyright: | (c) 2016 Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2015.11.028http://bit.ly/22fPJwT |
| Bibliographic Code: | 2016Icar..267..106N |
| Abstract: | Observations provide increasing evidence of a methane hydrological cycle on Titan. Earth-based and Cassini-based monitoring has produced data on the seasonal variation in cloud activity and location, with clouds being observed at increasingly low latitudes as Titan moved out of southern summer. Lakes are observed at high latitudes, with far larger lakes and greater areal coverage in the northern hemisphere, where some shorelines extend down as far as 50°N. Rainfall at some point in the past is suggested by the pattern of flow features on the surface at the Huygens landing site, while recent rainfall is suggested by surface change. As with the water cycle on Earth, the methane cycle on Titan is both impacted by tropospheric dynamics and likely able to impact this circulation via feedbacks. Here we use the 3D TitanWRF General Circulation Model (GCM) to simulate Titan's methane cycle. In this initial work we use a simple large-scale condensation scheme with latent heat feedbacks and a finite surface reservoir of methane, and focus on large-scale dynamical interactions between the atmospheric circulation and methane, and how these impact seasonal changes and the long term (steady state) behavior of the methane cycle. We note five major conclusions: (1) Condensation and precipitation in the model is sporadic in nature, with interannual variability in its timing and location, but tends to occur in association with both (a) frequent strong polar upwelling during spring and summer in each hemisphere, and (b) the Inter-Tropical Convergence Zone (ITCZ), a region of increased convergence and upwelling due to the seasonally shifting Hadley cells. (2) An active tropospheric methane cycle affects the stratospheric circulation, slightly weakening the stratospheric superrotation produced. (3) Latent heating feedback strongly influences surface and near-surface temperatures, narrowing the latitudinal range of the ITCZ, and changing the distribution - and generally weakening the strength - of upwelling events. (4) TitanWRF favors low latitude 'cloudiness' around northern spring equinox as the ITCZ moves from south to north across the equator, versus the opposite time of year. (5) TitanWRF produces drying of low and mid latitudes with net transport of surface methane to high latitudes, and shows persistent hemispheric asymmetry in the methane cycle such that the favored pole for surface methane is the one with winter occurring closest to perihelion. |