Characteristics and Regional Distribution of Intracrater Layered Deposits in Arabia

Introduction: Exposures of layered materials on Mars are of significant interest because of their potential for yielding information on past geologic processes and environments [1-12]. Arabia Terra, an extensive region of cratered ancient highlands, has an abundance of light-toned layered deposits that are both intracrater and intercrater in nature [6,7]. Analysis of the western and southwestern portions of this region have shown that these two groups are unrelated and may have formed under different geological processes [7]. Recent work on some intracrater layered deposits in Ara-bia Terra have shown that repeated sets of layers may be related to orbital climate cyclicity [8]. Using several datasets from the Mars Reconnaissance Orbiter mission , we are assessing the morphology and other characteristics of intracrater layered deposits with regard to their regional distribution in Arabia Terra. Study Region and Datasets: A 60x30 degree area (330-30 E, 0-30 N) was selected for studying the in-tracrater layered deposits. The region includes many used to assess crater and layer morphologies. Select CRISM spectral browse products in the visible-to-near-infrared and infrared spectrum were used for compositional information. In addition to these data-sets, global gridded MOLA topography and thermal inertia (TI) [13] were used to determine heights and relative dustiness of the deposits. All of the data were imported into ArcGIS and co-registered for viewing and analysis. A total of 46 impact craters were initially identified to have possible deposits based on THEMIS images and previous studies [9-10]. Of these 46 craters, 34 had sufficient image coverage by CTX, MOC, HiRISE, or some combination of the three to identify deposit morphologies and possible layering. Of these 34 craters, 29 had deposits with exposed layers that could be confidently identified. Other ancillary information regarding crater size and deposit features were also gathered. Layered Deposit Characteristics: The following describes the deposit forms, layer styles, and layer abundance observed in Arabia Terra. Deposit forms. Intracrater deposits generally have 4 forms: floor mound, isolated mound, floor, and buttes. Floor mounds are deposits with sloped sides that cover most, if not all of the crater floor with some parts abut-ting the crater wall, creating an " attached " appearance.