DOCSLIB.ORG

Boundary Condition Controls on the High-Sand-Flux Regions of Mars Matthew Chojnacki1, Maria E

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Boundary Condition Controls on the High-Sand-Flux Regions of Mars Matthew Chojnacki1, Maria E https://doi.org/10.1130/G45793.1 Manuscript received 8 November 2018 Revised manuscript received 18 January 2019 Manuscript accepted 20 February 2019 © 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 11 March 2019 Boundary condition controls on the high-sand-flux regions of Mars Matthew Chojnacki1, Maria E. Banks2, Lori K. Fenton3, and Anna C. Urso1 1Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA 2National Aeronautics and Space Administration (NASA) Goddard Space Flight Center, Greenbelt, Maryland 20771, USA 3Carl Sagan Center at the SETI (Search for Extra-Terrestrial Intelligence) Institute, Mountain View, California 94043, USA ABSTRACT DATA SETS AND METHODS Wind has been an enduring geologic agent throughout the history of Mars, but it is often To assess bed-form morphology and dynamics, unclear where and why sediment is mobile in the current epoch. We investigated whether we analyzed images acquired by the High Resolu- eolian bed-form (dune and ripple) transport rates are depressed or enhanced in some areas tion Imaging Science Experiment (HiRISE) cam- by local or regional boundary conditions (e.g., topography, sand supply/availability). Bed- era on the Mars Reconnaissance Orbiter (0.25–0.5 form heights, migration rates, and sand fluxes all span two to three orders of magnitude m/pixel; McEwen et al., 2007; see Table DR1 in across Mars, but we found that areas with the highest sand fluxes are concentrated in three the GSA Data Repository1). Digi tal terrain mod- regions: Syrtis Major, Hellespontus Montes, and the north polar erg. All regions are located els (1 m/pixel) and orthoimages of dune fields near prominent transition zones of topography (e.g., basins, polar caps) and thermophysical were constructed from HiRISE data using SOCET properties (e.g., albedo variations); these are not known to be critical terrestrial boundary SET® BAE Systems photogrammetry software conditions. The two regions adjacent to major impact basins (Hellas and Isidis Planitia) (Kirk et al., 2008). Volumetric sand fluxes q( crest) showed radially outward upslope winds driving sand movement, although seasonally revers- for dunes were obtained using the product of ing wind regimes were also observed. The northern polar dunes yielded the highest known the estimated height and lee crest displacement fluxes on the planet, driven by summer katabatic winds modulated by the seasonal CO2 cap over the intervening time between acquisition of retreat—processes not known to affect terrestrial dunes. In contrast, southern dune fields repeated HiRISE images (2–5 Mars years), mea- (<45°S) were less mobile, likely as a result of seasonal frost and ground ice suppressing sand sured in units of m3 m–1 yr–1 in time units of Earth availability. Results suggest that, unlike on Earth, large-scale topographic and thermophysi- years. Sand fluxes, migration rates, and heights cal variabilities play a leading role in driving sand fluxes on Mars. were collected for 54 dune fields (495 separate dunes). Ripple migration rates were integrated INTRODUCTION construction appears to be extremely limited on from prior work (Banks et al., 2015, 2018). For most of the history of Mars, eolian pro- Venus (based on orbital radar data; Greeley et al., To provide regional context for monitor- cesses have been one of the leading factors in 1995), whereas bed forms on Titan (a moon of ing sites, topographic and thermal properties landscape evolution, in contrast to Earth and Saturn) cover an estimated ~13% of the surface (albedo and daytime surface temperature) were early Mars, where aqueous processes prevailed. (from similar data; Le Gall et al., 2012). The examined from Mars Orbiter Laser Altimeter Recent orbital studies have revealed that winds numerous extraneous environmental factors on data (Smith et al., 2001) and Thermal Emission frequently transport fine-grained sediments planetary bodies with atmospheres (e.g., transport Spectrometer (on the Mars Global Surveyor) across the surface of Mars today, as evidenced capacity, sand supply, topography) operate non- data (Christensen et al., 1992), respectively. See by the mobility of eolian bed forms (dunes and linearly to produce self-organized bed forms that the GSA Data Repository, sections 1 and 2, for ripples; e.g., Silvestro et al., 2010; Chojnacki evolve in response to environmental conditions additional methodology and boundary condition et al., 2011, 2017, 2018; Bridges et al., 2011, (e.g., Kocurek and Lancaster, 1999; Ewing and characterization details, respectively. 2012; Ayoub et al., 2014; Banks et al., 2015, Kocurek, 2010). Recognition of these underly- 2018). The degree of contemporary sand mobil- ing boundary conditions can provide insight into RESULTS ity has implications for the Martian climate, dust landscape evolution on Mars because eolian pro- cycle, and landscape evolution. Moreover, spa- cesses have played a major role there for most of Global Results of Bed-Form Transport tial variations in bed-form transport parameters its history (Armstrong and Leovy, 2005). Parameters relate to external forcing factors (i.e., boundary The objective of this investigation was to Active eolian bed forms were detected across conditions), some of which may be unique to assess the boundary conditions that govern bed- Mars within craters, canyons, structural fossae, the red planet. form migration trends on Mars and whether those volcanic paterae, polar basins, and extracrater (e.g., Terrestrial antecedent conditions, such as conditions differ from ones on Earth. Recogniz- plains) terrain (Fig. 1). The average migration rate, near-surface water tables and vegetation, can ing these factors may also provide predictabil- typically for barchan or barchanoid dune morphol- critically influence local bed-form patterns and ity for other locations lacking sufficient data for ogies, across all sites investigated here was ~0.5 ± mobility. On Mars, factors like crater morphology monitoring. This was achieved by quantifying the 0.4 m/yr (1σ) for dunes ~2–120 m tall. Superposed and local surface roughness can influence sand dynamic activity of bed forms globally and evalu- sub-meter-tall ripples (~40 cm tall, where height fluxes (Chojnacki et al., 2017). Large-scale dune ating the regional factors that may play a role. estimates were from in situ observations; Ewing 1GSA Data Repository item 2019150, Figures DR1–DR5, Tables DR1 (list of images), Tables DR2 and DR3 (region summary tables), and Animations DR1–DR8, is available online at http:// www .geosociety .org /datarepository /2019/, or on request from editing@ geosociety .org. CITATION: Chojnacki, M., Banks, M.E., Fenton, L.K., and Urso, A.C., 2019, Boundary condition controls on the high-sand-flux regions of Mars: Geology, v. 47, p. 427–430, https:// doi .org /10 .1130 /G45793.1 Geological Society of America | GEOLOGY | Volume 47 | Number 5 | www.gsapubs.org 427 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/47/5/427/4680645/427.pdf by guest on 01 October 2021 Figure 1. Global trends in E conditions dictate many physical aspects of dune bed-form mobility. Top: N Polar cap morphology and activity, the three regions with Map of sand dune crest Abalos Undae Olympia Undae Sand Flux (m3 m–1 yr –1) remarkably high sand fluxes deserve further flux measurements for 0.8–5.0 54 dune fields (graduated consideration. 5.0–9.0 Arabia Terra Syrtis Major circles with low [red], 9.0–19.8 moderate [orange], and Mobile Valles Marineris Isidis basin Gale Syrtis Major high [green] sand flux No Detection Meridiani values), bed-form mobility Dunes across the low-albedo (~0.1) Syrtis detection status (trian- Hellespontus Major are found in a variety of geographical con- Hellas basin gles; Banks et al., 2015, Terra Cimmeria texts (e.g., fossae, paterae, plains, and craters), but 2018), and dune field dis- Terra Sirenum Noachis Terra their migration vectors appear to be strongly influ- tributions (red polygons; S Polar cap enced by the 4–5-km-deep Isidis basin to the east Hayward et al., 2014). Three high-sand-flux Dune Rate (m yr–1) Dune Height (m) Sand Flux (m3 m–1 yr –1) (Fig. 3; Table DR2). Westward sand transport at regions of Syrtis Major, n=495 n=495 n=495 this equatorial latitude is governed by the super- Hellespontus Montes, and 0.49 ± 0.43 19 ± 14 7.8 ± 6.4 position of the meridional (Hadley cell) overturn- the north polar erg (Mars) ing circulation and planetary rotation, but this flow are outlined in black and shown in more detail in is further enhanced by a strong thermal tide and Figure 3. Base map is Mars Orbiter Laser Altimeter (MOLA) shaded relief with colorized eleva- anabatic slope winds driven up and radially out- tion from +4 (red) to –5 km (blue). Bottom: Histograms of dune metrics with averages ± 1σ. ward from the dusty Isidis basin (albedo ~0.23) by daytime solar heating (e.g., Ayoub et al., 2014). et al., 2017) showed similar rates (~0.5 m/yr), west of the Isidis basin, Hellespontus west of the Dunes near Jezero crater and deep within Nili Fos- although examples of faster ripples have often been Hellas basin, and the circumpolar erg adjacent to sae are clearly migrating to the west-northwest reported (Bridges et al., 2012). The average qcrest the north polar cap (Figs. 3 and 4). Elevation pro- (Chojnacki et al., 2018), whereas sand dunes along for all dune fields ranged between 0.8 and 17.6 files several hundreds of kilometers in length from Nili and Meroe Paterae are translating toward the m3 m–1 yr–1 (Fig. 2), while the highest flux for an basins toward the higher-elevation terrains have west-southwest (Fig. 3; see Animations DR1 3 –1 –1 individual dune was 35 m m yr (average qcrest = 4–7 km in relief, except for the shorter (~2-km- and DR2 and Table DR1).
Load more

Recommended publications
  • North Polar Region of Mars: Advances in Stratigraphy, Structure, and Erosional Modification
    Icarus 196 (2008) 318–358 www.elsevier.com/locate/icarus North polar region of Mars: Advances in stratigraphy, structure, and erosional modification Kenneth L. Tanaka a,∗, J. Alexis P. Rodriguez b, James A. Skinner Jr. a,MaryC.Bourkeb, Corey M. Fortezzo a,c, Kenneth E. Herkenhoff a, Eric J. Kolb d, Chris H. Okubo e a US Geological Survey, Flagstaff, AZ 86001, USA b Planetary Science Institute, Tucson, AZ 85719, USA c Northern Arizona University, Flagstaff, AZ 86011, USA d Google, Inc., Mountain View, CA 94043, USA e Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA Received 5 June 2007; revised 24 January 2008 Available online 29 February 2008 Abstract We have remapped the geology of the north polar plateau on Mars, Planum Boreum, and the surrounding plains of Vastitas Borealis using altimetry and image data along with thematic maps resulting from observations made by the Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter spacecraft. New and revised geographic and geologic terminologies assist with effectively discussing the various features of this region. We identify 7 geologic units making up Planum Boreum and at least 3 for the circumpolar plains, which collectively span the entire Amazonian Period. The Planum Boreum units resolve at least 6 distinct depositional and 5 erosional episodes. The first major stage of activity includes the Early Amazonian (∼3 to 1 Ga) deposition (and subsequent erosion) of the thick (locally exceeding 1000 m) and evenly- layered Rupes Tenuis unit (ABrt), which ultimately formed approximately half of the base of Planum Boreum. As previously suggested, this unit may be sourced by materials derived from the nearby Scandia region, and we interpret that it may correlate with the deposits that regionally underlie pedestal craters in the surrounding lowland plains.
    [Show full text]
  • Scf Pan Sahara Wildlife Survey
    SCF PAN SAHARA WILDLIFE SURVEY PSWS Technical Report 12 SUMMARY OF RESULTS AND ACHIEVEMENTS OF THE PILOT PHASE OF THE PAN SAHARA WILDLIFE SURVEY 2009-2012 November 2012 Dr Tim Wacher & Mr John Newby REPORT TITLE Wacher, T. & Newby, J. 2012. Summary of results and achievements of the Pilot Phase of the Pan Sahara Wildlife Survey 2009-2012. SCF PSWS Technical Report 12. Sahara Conservation Fund. ii + 26 pp. + Annexes. AUTHORS Dr Tim Wacher (SCF/Pan Sahara Wildlife Survey & Zoological Society of London) Mr John Newby (Sahara Conservation Fund) COVER PICTURE New-born dorcas gazelle in the Ouadi Rimé-Ouadi Achim Game Reserve, Chad. Photo credit: Tim Wacher/ZSL. SPONSORS AND PARTNERS Funding and support for the work described in this report was provided by: • His Highness Sheikh Mohammed bin Zayed Al Nahyan, Crown Prince of Abu Dhabi • Emirates Center for Wildlife Propagation (ECWP) • International Fund for Houbara Conservation (IFHC) • Sahara Conservation Fund (SCF) • Zoological Society of London (ZSL) • Ministère de l’Environnement et de la Lutte Contre la Désertification (Niger) • Ministère de l’Environnement et des Ressources Halieutiques (Chad) • Direction de la Chasse, Faune et Aires Protégées (Niger) • Direction des Parcs Nationaux, Réserves de Faune et de la Chasse (Chad) • Direction Générale des Forêts (Tunis) • Projet Antilopes Sahélo-Sahariennes (Niger) ACKNOWLEDGEMENTS The Sahara Conservation Fund sincerely thanks HH Sheikh Mohamed bin Zayed Al Nahyan, Crown Prince of Abu Dhabi, for his interest and generosity in funding the Pan Sahara Wildlife Survey through the Emirates Centre for Wildlife Propagation (ECWP) and the International Fund for Houbara Conservation (IFHC). This project is carried out in association with the Zoological Society of London (ZSL).
    [Show full text]
  • Slender-Horned Gazelle Gazella Leptoceros Conservation Strategy 2020-2029
    Slender-horned Gazelle Gazella leptoceros Conservation Strategy 2020-2029 Slender-horned Gazelle (Gazella leptoceros) Slender-horned Gazelle (:Conservation Strategy 2020-2029 Gazella leptoceros ) :Conservation Strategy 2020-2029 Conservation Strategy for the Slender-horned Gazelle Conservation Strategy for the Slender-horned Conservation Strategy for the Slender-horned The designation of geographical entities in this book, and the presentation of the material, do not imply the expression of any opinion whatsoever on the part of any participating organisation concerning the legal status of any country, territory, or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The views expressed in this publication do not necessarily reflect those of IUCN or other participating organisations. Compiled and edited by David Mallon, Violeta Barrios and Helen Senn Contributors Teresa Abaígar, Abdelkader Benkheira, Roseline Beudels-Jamar, Koen De Smet, Husam Elalqamy, Adam Eyres, Amina Fellous-Djardini, Héla Guidara-Salman, Sander Hofman, Abdelkader Jebali, Ilham Kabouya-Loucif, Maher Mahjoub, Renata Molcanova, Catherine Numa, Marie Petretto, Brigid Randle, Tim Wacher Published by IUCN SSC Antelope Specialist Group and Royal Zoological Society of Scotland, Edinburgh, United Kingdom Copyright ©2020 IUCN SSC Antelope Specialist Group Reproduction of this publication for educational or other non-commercial purposes is authorised without prior written permission from the copyright holder provided the source is fully acknowledged. Reproduction of this publication for resale or other commercial purposes is prohibited without prior written permission of the copyright holder. Recommended citation IUCN SSC ASG and RZSS. 2020. Slender-horned Gazelle (Gazella leptoceros): Conservation strategy 2020-2029. IUCN SSC Antelope Specialist Group and Royal Zoological Society of Scotland.
    [Show full text]
  • The Environmental History and Present Condition of Saudi Arabia's
    UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY The environmental history and present condition of Saudi Arabia's northern sand seas by J. W. Whitney I/, D. J. Faulkender, and Meyer Rubin 2/ Open-File Report 83- 7V Prepared for Ministry of Petroleum and Mineral Resources, Deputy Ministry for Mineral Resources Jiddah, Kingdom of Saudi Arabia This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature I/ U.S. Geological Survey, Denver, CO 80225 2/ U.S. Geological Survey, Radiocarbon Lab., Reston, VA 22092 1983 CONTENTS Page ABSTRACT................................................ 1 INTRODUCTION............................................ 2 PHYSICAL SETTING AND SEDIMENT SOURCES OF THE SAND SEAS.. 4 AGE AND ORIGIN OF THE SAND SEAS......................... 8 QUATERNARY EOLIAN AND LACUSTRINE DEPOSITS............... 12 Dune systems........................................ 12 Active versus stable dunes.......................... 15 Pleistocene and Holocene lake deposits.............. 18 Diatomite........................................... 24 PRESENT CONDITION OF THE SAND SEAS...................... 25 Precipitation and temperature....................... 25 Vegetation.......................................... 27 Modern and paleo-wind systems....................... 29 ENVIRONMENTAL HISTORY OF THE SAND SEAS.................. 32 DATA STORAGE............................................ 35 REFERENCES CITED........................................ 36 ILLUSTRATIONS
    [Show full text]
  • INVESTIGATING the ORIGIN of GYPSUM in OLYMPIA UNDAE: CHARACTERIZING the MINERALOGY of the BASAL UNIT. E. Das1, J. F. Mustard1 and J
    52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2390.pdf INVESTIGATING THE ORIGIN OF GYPSUM IN OLYMPIA UNDAE: CHARACTERIZING THE MINERALOGY OF THE BASAL UNIT. E. Das1, J. F. Mustard1 and J. D. Tarnas1,2, 1Department of Earth, Environmental and Planetary Sciences, Brown University, Providence RI 02912 ([email protected]), 2Jet Propulsion Laboratory, California Institute of Technology Introduction: The Olympia Undae Sand Sea, near eigenvectors derived from the Hysime algorithm [10] the North Polar ice cap, contains the largest known and determines the independent components of the deposit of gypsum discovered on Mars [1]. The mixed system. 2) Dot Product Mapping: The dot formation of gypsum requires liquid water, hinting that products of the image cube with individual it formed in the North Polar region under circumstances eigenvectors, specifically those containing interesting vastly different from today’s Martian environment. The spectral features, are obtained to highlight regions presence of gypsum in the late Amazonian age dunes, within the image cube where the target mineral may likely sourced from materials of the late Hesperian- have a strong spectral signal. The 3rd eigenvector along early/mid-Amazonian ages [2], are consistent with with its associated dot product map of a subset of wetter periods during these ages. Since the discovery of CRISM image (HRL00003084) over Olympia Undae gypsum in the north polar dunes, various hypotheses are shown in Figure 1. The 3rd eigenvector was chosen have been suggested for its source. One hypothesis as it contained prominent spectral features similar to the suggested formation from in-situ aqueous alteration of target mineral gypsum.
    [Show full text]
  • Origin of the Sinai-Negev Erg, Egypt and Israel: Mineralogical and Geochemical Evidence for the Importance of the Nile and Sea Level History Daniel R
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USGS Staff -- ubP lished Research US Geological Survey 2013 Origin of the Sinai-Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history Daniel R. Muhs U.S. Geological Survey, [email protected] Joel Roskin Ben-Gurion University of the Negev Haim Tsoar Ben-Gurion University of the Negev Gary Skipp U.S. Geological Survey, [email protected] James Budahn U.S. Geological Survey See next page for additional authors Follow this and additional works at: https://digitalcommons.unl.edu/usgsstaffpub Part of the Geology Commons, Oceanography and Atmospheric Sciences and Meteorology Commons, Other Earth Sciences Commons, and the Other Environmental Sciences Commons Muhs, Daniel R.; Roskin, Joel; Tsoar, Haim; Skipp, Gary; Budahn, James; Sneh, Amihai; Porat, Naomi; Stanley, Jean-Daniel; Katra, Itzhak; and Blumberg, Dan G., "Origin of the Sinai-Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history" (2013). USGS Staff -- Published Research. 931. https://digitalcommons.unl.edu/usgsstaffpub/931 This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USGS Staff -- ubP lished Research by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Authors Daniel R. Muhs, Joel Roskin, Haim Tsoar, Gary Skipp, James Budahn, Amihai Sneh, Naomi Porat, Jean-Daniel Stanley, Itzhak Katra, and Dan G. Blumberg This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/usgsstaffpub/931 Quaternary Science Reviews 69 (2013) 28e48 Contents lists available at SciVerse ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Origin of the SinaieNegev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history Daniel R.
    [Show full text]
  • This Article Appeared in a Journal Published by Elsevier. the Attached
    (This is a sample cover image for this issue. The actual cover is not yet available at this time.) This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Aeolian Research 8 (2013) 29–38 Contents lists available at SciVerse ScienceDirect Aeolian Research journal homepage: www.elsevier.com/locate/aeolia Review Article Summary of the Third International Planetary Dunes Workshop: Remote Sensing and Image Analysis of Planetary Dunes, Flagstaff, Arizona, USA, June 12–15, 2012 ⇑ Lori K. Fenton a, , Rosalyn K. Hayward b, Briony H.N. Horgan c, David M. Rubin d, Timothy N. Titus b, Mark A. Bishop e,f, Devon M. Burr g, Matthew Chojnacki g, Cynthia L. Dinwiddie h, Laura Kerber i, Alice Le Gall j, Timothy I. Michaels a, Lynn D.V. Neakrase k, Claire E. Newman l, Daniela Tirsch m, Hezi Yizhaq n, James R. Zimbelman o a Carl Sagan Center at the SETI Institute, 189 Bernardo Ave., Suite 100, Mountain View, CA 94043, USA b United States Geological Survey, Astrogeology Science Center, 2255 N.
    [Show full text]
  • Assessment of the Distribution and Activity of Dunes in Iran Based on T Mobility Indices and Ground Data ⁎ H.R
    Aeolian Research 41 (2019) 100539 Contents lists available at ScienceDirect Aeolian Research journal homepage: www.elsevier.com/locate/aeolia Assessment of the distribution and activity of dunes in Iran based on T mobility indices and ground data ⁎ H.R. Abbasia,b, , C. Oppa, M. Grolla, H. Rohipourb, A. Gohardoustb a Faculty of Geography, University of Marburg, 35032 Marburg, Germany b Desert Division, Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), 13165-116 Tehran, Iran ARTICLE INFO ABSTRACT Keywords: Sand dune movement causes severe damage to infrastructure and rural settlements in Iran every year. Iran, sand dunes Identifying active dunes and monitoring areas with migrating sand are important prerequisites for mitigating Dune mobility index these damages. With regard to this objective, the spatial variation of the wind energy environment based on the Wind energy sand drift potential (DP) was calculated from 204 meteorological stations. Three commonly used dune activity Active dune models – the Lancaster mobility index (1988), the Tsoar mobility index (2005), and the index developed by Yizhaq et al. (2009) – were used for the evaluation of Iran’s sand dune activity. The analysis of the indices showed that the dune activity was characterized by great spatial variation across Iran’s deserts. All three models identified fully active dunes in the Sistan plain, the whole of the Lut desert, as well as in the ZirkuhQaienand Deyhook regions, while the dunes in the northern part of Rig Boland, Booshroyeh and in the Neyshabor du- nefields were categorized as stabilized dunes. For other dunes, the models show a less unified activity classifi- cation, with the Lancaster and Yizhaq models having more similar results while the Tsoar model stands more apart.
    [Show full text]
  • Linear Dune Morphometrics in Titan's Belet Sand Sea and a Comparison
    Brigham Young University BYU ScholarsArchive Theses and Dissertations 2018 Linear Dune Morphometrics in Titan’s Belet Sand Sea and a Comparison with the Namib Sand Sea Corbin Robert Lewis Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd Part of the Geology Commons BYU ScholarsArchive Citation Lewis, Corbin Robert, "Linear Dune Morphometrics in Titan’s Belet Sand Sea and a Comparison with the Namib Sand Sea" (2018). Theses and Dissertations. 7688. https://scholarsarchive.byu.edu/etd/7688 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Linear Dune Morphometrics in Titan’s Belet Sand Sea and a Comparison with the Namib Sand Sea Robert Corbin Lewis A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science Jani Radebaugh, Chair Eric H. Christiansen Samuel M. Hudson Department of Geological Sciences Brigham Young University Copyright © 2018 Robert Corbin Lewis All Rights Reserved ABSTRACT Linear Dune Morphometrics in Titan’s Belet Sand Sea and a Comparison with the Namib Sand Sea Robert Corbin Lewis Department of Geological Sciences, BYU Master of Science Despite atmospheric and compositional differences on Titan and Earth, the similarity in the shape and spacing of linear dunes of the Belet Sand Sea of Titan and the Namib Sand Sea of Earth suggests that comparisons will yield a better understanding of the dictating factors of dune- forming processes.
    [Show full text]
  • Severe Decline of Large Birds in the Northern Sahel of West Africa: a Long-Term Assessment
    Bird Conservation International (2006) 16:353–365. ß BirdLife International 2006 doi: 10.1017/S0959270906000487 Printed in the United Kingdom Severe decline of large birds in the Northern Sahel of West Africa: a long-term assessment JEAN-MARC THIOLLAY Summary The current status of most West African birds is little known and may change quickly with increasing human population pressure and agriculture, road, tourism, hunting and mining developments. Following documented declines of raptors in Sudan and the Southern Sahel zones, I compared the number of birds counted along the same eight extensive transect counts in 1971– 1973 (3,703 km) and 2004 (3,688 km) in arid steppes, acacia woodlands and desert mountains of northern Mali and Niger (Adrar des Iforhas, Aı¨r, Te´ne´re´). The once widespread Ostrich Struthio camelus is now extinct west of Chad. No Arabian Ardeotis arabs and Nubian Bustards Neotis nuba were seen in 2004 (216 in 1970s) nor any Ru¨ ppell’s Griffon Gyps rueppellii and Lappet-faced Vultures Torgos tracheliotus (114 and 96 respectively recorded in the 1970s). From Adrar to Te´ne´re´, just one Egyptian Vulture Neophron percnopterus was recorded in 2004 (vs 75 in 1970s), but it was still common in the oases of Kawar (27 vs 38). These data are exploratory and the current status of the species involved should be further documented. Nevertheless, they are a serious warning about the future of several taxa. Overhunting, aggravated by overgrazing and degradation of acacia woodlands are obvious causes of the collapse of Ostrich and bustards. The near-extinction of wild ungulates, intensified use of cattle, increased disturbance and poisoning of predators may have been critical in the dramatic decline of vultures.
    [Show full text]
  • Wind Erosion of Layered Sediments on Mars: the Role of Terrain
    Wind erosion of layered sediments on Mars: The role of terrain For submission to ROSES - Solar System Workings 2014 (NNH14ZDA001N-SSW) 1. Table of contents ............................................................................................................0 2. Scientific/Technical/Management ................................................................................1 2.1 Summary .................................................................................................................1 2.2 Goals of the Proposed Study .................................................................................1 2.3 Scientific Background ............................................................................................1 2.3.1. Wind erosion on Mars ...................................................................................1 2.3.2. Slope winds ...................................................................................................3 2.3.3. Formation of sedimentary mounds and moats ..............................................4 2.4 Technical Approach and Methodology ................................................................4 2.4.1. Application of the Mars Regional Atmospheric Modeling System ..............5 2.4.2. Numerical experiments with idealized craters and canyons .........................6 2.4.3. Consideration of the effect of sedimentary infill (sedimentary mounds) .....7 2.4.4. Simulation of slope-eroding winds for geologically realistic terrain ............9 2.4.5. Incorporation of slope
    [Show full text]
  • Carnegie Institution Carnegie
    C68099_CVR.qxd:CVR 3/29/11 7:58 Page 1 2009-2010 CARNEGIE INSTITUTION FOR 2009-2010 SCIENCE YEAR BOOK 1530 P Street, N.W. Washington DC 20005 Phone: 202.387.6400 Carnegie Institution Fax: 202.387.8092 www.CarnegieScience.edu FOR SCIENCE CARNEGIE INSTITUTION FOR SCIENCE INSTITUTION FOR CARNEGIE YEAR BOOK The paper used in the manufacturing this year book contains 30% post-consumer recycled fiber. By using recycled fiber in place of virgin fiber, the Carnegie Institution preserved 41 trees, saved 126 pounds of waterborne waste, saved 18,504 gallons of water and prevented 4031 pounds of greenhouse gasses. The energy used to print the report was produced by wind power. Designed by Tina Taylor, T2 Design Printed by Monroe Litho ISSN 0069-066X C68099_CVR.qxd:CVR 3/29/11 7:58 Page 2 Department of Embryology 3520 San Martin Dr. / Baltimore, MD 21218 410.246.3001 Geophysical Laboratory 5251 Broad Branch Rd., N.W. / Washington, DC 20015-1305 202.478.8900 Department of Global Ecology 260 Panama St. / Stanford, CA 94305-4101 650.462.1047 The Carnegie Observatories 813 Santa Barbara St. / Pasadena, CA 91101-1292 626.577.1122 Las Campanas Observatory Casilla 601 / La Serena, Chile Department of Plant Biology 260 Panama St. / Stanford, CA 94305-4101 650.325.1521 Department of Terrestrial Magnetism 5241 Broad Branch Rd., N.W. / Washington, DC 20015-1305 202.478.8820 Office of Administration 1530 P St., N.W. / Washington, DC 20005-1910 202.387.6400 www.CarnegieScience.edu 2 009-2010 YEAR BOOK The President’s Report July 1, 2009 - June 30, 2010 CARNEGIE INSTITUTION FOR SCIENCE Former Presidents Former Trustees Daniel C.
    [Show full text]