George E. McGill 2005 <p><span class="TextRun SCXW45984790 BCX8" lang="EN-US" xml:lang="EN-US" data-contrast="auto"><span class="NormalTextRun SCXW45984790 BCX8">Cydonia </span><span class="NormalTextRun SCXW45984790 BCX8">Mensae</span><span class="NormalTextRun SCXW45984790 BCX8"> lie adjacent to the boundary separating the highland terrain of western Arabia Terra from the northern lowlands (the dichotomy boundary), where this boundary is gradational rather than abrupt, as is generally the case. Cydonia </span><span class="NormalTextRun SCXW45984790 BCX8">Mensae</span><span class="NormalTextRun SCXW45984790 BCX8"> are characterized by abundant knobs and mesas, most of which occur in </span><span class="ContextualSpellingAndGrammarError SCXW45984790 BCX8">well defined</span><span class="NormalTextRun SCXW45984790 BCX8"> clusters that commonly are long and narrow. The adjacent lowland of </span><span class="NormalTextRun SCXW45984790 BCX8">Acidalia</span><span class="NormalTextRun SCXW45984790 BCX8"> Planitia contains abundant troughs that define a crude, very </span><span class="ContextualSpellingAndGrammarError SCXW45984790 BCX8">large scale</span><span class="NormalTextRun SCXW45984790 BCX8"> polygonal pattern. This pattern, and the troughs, are similar in size and spacing to those in Utopia Planitia (for example, McGill and Hills, 1992; </span><span class="SpellingError SCXW45984790 BCX8">Hiesinger</span><span class="NormalTextRun SCXW45984790 BCX8"> and Head, 2000). The six 1:500,000-scale quadrangles mapped are MTM 40007, 40012, 40017, 45007, 45012, and 45017, which include northern Cydonia </span><span class="NormalTextRun SCXW45984790 BCX8">Mensae</span><span class="NormalTextRun SCXW45984790 BCX8">, part of southern </span><span class="NormalTextRun SCXW45984790 BCX8">Acidalia</span><span class="NormalTextRun SCXW45984790 BCX8"> Planitia, and a small area of Arabia Terra highlands. These six quadrangles are combined into a single map at 1:1,000,000 scale for this publication. Issues of interest addressed by this mapping include the crustal history implied by the knobs and mesas of Cydonia </span><span class="NormalTextRun SCXW45984790 BCX8">Mensae</span><span class="NormalTextRun SCXW45984790 BCX8">, the implications of the gradational dichotomy boundary, the age of the </span><span class="NormalTextRun SCXW45984790 BCX8">Acidalia</span><span class="NormalTextRun SCXW45984790 BCX8"> plains materials, the origin and age of the giant polygons, the validity of putative shorelines inferred to be present in this area, and the origin of the very abundant small cones and domes, specifically if these imply the past presence of water or ice within the </span><span class="NormalTextRun SCXW45984790 BCX8">plains</span><span class="NormalTextRun SCXW45984790 BCX8"> materials. Earlier maps (</span><span class="NormalTextRun SCXW45984790 BCX8">Witbeck</span><span class="NormalTextRun SCXW45984790 BCX8"> and Underwood, 1984; Scott and Tanaka, 1986; Tanaka and others, 2003) that included the area mapped for this study addressed some or </span><span class="AdvancedProofingIssue SCXW45984790 BCX8">all of</span><span class="NormalTextRun SCXW45984790 BCX8"> these issues, but these maps were more regional in coverage and were at smaller scales. In addition, new orbital data from Mars Global Surveyor and Mars Odyssey missions were available only to Tanaka and others (2003). The intent of this present study is to address the issues listed by mapping at a scale large enough to permit greater map detail and to better understand the areal distribution of the materials and features of interest.</span></span></p> application/pdf 10.3133/i2811 en U.S Geological Survey Geologic map of Cydonia Mensae - southern Acidalia Planitia, Mars, quadrangles MTM 40007, 40012, 40017, 45007, 45012, and 45017 reports