Rivers and lakes in Western Arabia Terra: The Fluvial catchment of the ExoMars 2022 rover landing site

Description

This file
contains the supplementary data to accompany ‘Rivers and lakes in Western
Arabia Terra: The Fluvial catchment of the ExoMars 2022 rover landing site’

Peter
Fawdon ([e-mail]). The Open University, Walton Hall, Milton
Keynes MK7 7EA United Kingdom,

All data is
supplied in a equirectangular projection centered on Oxia Planum at 335.45deg
east following Fawdon et al., (2021) A geographic framework for exploring the
ExoMars rover landing site at Oxia Planum, Mars

Shapefile
data

01_Pourpoints

Point data
used to calculate Oxia Planum model watersheds

02_Watersheds

Polygons
delimiting the extent of the Oxia Planum model watersheds

03_Channels

All
channels observed in CTX data within the model watersheds.

‘Channel_ty’
field has 5 values: WFF, Wide Flat Floored. NUS - U-section. LRC, Low Relief
channels. SLR, sinuous ridges. INT, channels within impact craters. INF,
Inferred or possible channel pathways

04_Lakes

All
possible lakes identified in the within the model watersheds with the numbers
of morphological indicators for each possible lake.

‘Type’
field has 4 values: 1, Large Crater lakes. 2, Rimless Crater lakes. 3.
Irregular Dark depressions. 4, possible sediment fans.

Geomorphological
features recorded are: Inlets, Outlets, Sediment fans, Interior channels,
Smooth floor, Strandlines and Concentric albedo changes.

Possible
maximum models volumes have been calculated for some lakes using the volume
difference between unfilled and filled MOLA DEM within the boundary of the
possible lake as defined by where the
fill hillshade = 180.

05_StreamOrder

Strahler
stream order for the model flow accumulation pathways for the model watersheds
areas.

Raster
Data

Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin.tif

Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin_fill.tif

Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin_fill_hillshade.tif

Extract
from the methord section of ‘Rivers and lakes in Western Arabia Terra: The
Fluvial catchment of the ExoMars 2022 rover landing site’

Geomorphological
observations of fluvial features were made using CTX, 6 meter/pixel data at a
scale of 1:50,000, georeferenced to High Resolution Stereo Camera MC11
quadrangle mosaic basemap (HRSC; Gwinner et al., 2016; Neukum et al., 2004).
THermal EMission Imaging System (THEMIS; Christensen et al., 2013) night and
daytime IR global mosaics were used to inform identification of features
observed in the CTX data, and Colour and Stereo Surface Imaging System (CaSSIS;
Thomas et al., 2017) images were used where available for colour
interpretation. Mars Orbital Laser Altimeter (MOLA; Zuber et al., 1992) data
were used for topographic information. Using these data, a fluvial
(valley/channel and sinuous ridges) and lacustrine features was identified.
After the initial survey, a topographic flow accumulation model was used to
identify areas to revise where the model suggested channels might be present,
and these were then searched more closely for any subtle morphological evidence
of fluvial landforms. This iterative, multi-data process enabled many more
fluvial systems to be identified than using one dataset alone.

To
determine the watershed area for Oxia Planum (Figure 1), the ArcMap 10.5
Spatial Analyst ‘ArcHydro’ toolset (Esri, 2016) was used to calculate a model
of flow accumulation grids and a drainage network map using topographic data
from the MOLA DEM (Smith et al., 2001). Areas in the DEM that created sinks or
basins were filled prior to calculating flow direction and accumulation. It is
important to note that these processing steps ‘fill in’ areas of low-lying
terrain and impact craters, as well as unwanted error and noise in the DEM.
These ‘filled in’ areas create model flow pathways stretched across basins that
were retained to identify where ponding may have occurred and where the model
flow is likely to deviate from the geomorphic observations.

The
watershed and contributory areas were calculated using the flow accumulation
model upslope of two pour points located in the Oxia Basin. The location of
both pour points (see Figure 2) was based on the correspondence of preliminary
model flow accumulation paths calculated for the whole MC-11 Quad and
geomorphological features resolved in the MOLA DEM. The eastern pour point (the
lowest point in the ‘fan’ watershed) was located where the channel of Coogoon
Valles opens out into Oxia Basin at the highest elevation of the sediment fan
remnants. The northern pour point (the lowest point in the basin watershed) was
located at the lowest point of the Oxia Basin leading northwards to Chryse
Planitia. The watershed is defined where the flow accumulation is 0 (i.e. there
are no cells from which water would flow). The pour points, their watersheds,
and the flow accumulation pathways were converted to Strahler stream order
(Strahler, 1957).

本文件包含伴随《西部阿拉伯地盾的河流与湖泊：ExoMars 2022 罗ver着陆点流域》的补充数据。

Peter Fawdon（[e-mail]）
开放大学，沃尔顿学院，米尔顿凯恩斯 MK7 7EA 英国

所有数据均以等角圆柱投影提供，投影中心位于奥克西亚平原，经度为335.45度，遵循Fawdon等人（2021年）的研究《探索奥克西亚平原ExoMars 罗ver着陆点的地理框架》。

Shapefile 数据

01_Pourpoints
用于计算奥克西亚平原模型流域的点数据。

02_Watersheds
界定奥克西亚平原模型流域范围的多边形。

03_Channels
在模型流域内观察到的所有通道，数据来源于CTX。
‘Channel_ty’字段包含5个值：WFF - 宽平底；NUS - U形；LRC - 低起伏通道；SLR - 波浪状脊；INT - 冲击坑内的通道；INF - 推测或可能的通道路径。

04_Lakes
在模型流域内识别的所有可能的湖泊，以及每个可能的湖泊的形态指标数量。
‘Type’字段包含4个值：1 - 大撞击坑湖；2 - 无边撞击坑湖；3 - 不规则暗色洼地；4 - 可能的泥沙扇。
记录的地质形态特征包括：入口、出口、泥沙扇、内部通道、平滑底部、海滩线和同心度反照率变化。
使用未填充和填充的MOLA DEM之间的体积差，计算了某些湖泊的可能最大模型体积，填充高程阴影等于180。

05_StreamOrder
模型流域区域的模型流积累路径的Strahler河流阶数。

Raster 数据

Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin.tif
Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin_fill.tif
Mars_MGS_MOLA_DEM_mosaic_global_463m_MC11_PourPoint_OxiaBasin_fill_hillshade.tif

方法部分摘录自《西部阿拉伯地盾的河流与湖泊：ExoMars 2022 罗ver着陆点流域》
使用CTX、6米/像素数据在1:50,000的比例下进行的河流特征地质观察，该数据通过高分辨率立体相机MC11四边形拼图基本图（HRSC；Gwinner等人，2016年；Neukum等人，2004年）进行地理配准。热发射成像系统（THEMIS；Christensen等人，2013年）的昼夜红外全球拼图用于告知CTX数据中观察到的特征，在有可用的情况下，使用彩色和立体表面成像系统（CaSSIS；Thomas等人，2017年）的图像进行颜色解释。火星轨道激光高度计（MOLA；Zuber等人，1992年）的数据用于地形信息。使用这些数据，识别了河流（山谷/通道和波浪状脊）和湖泊特征。在初步调查之后，使用地形流积累模型来确定可能存在通道的区域，然后对这些区域进行更细致的搜索，以寻找任何细微的河流地貌形态证据。这种迭代的多数据过程使得比单独使用一个数据集能够识别出更多的河流系统。

为了确定奥克西亚平原的流域面积（图1），使用了ArcMap 10.5空间分析师‘ArcHydro’工具集（Esri，2016年）来计算使用MOLA DEM（Smith等人，2001年）提供的地形数据的流积累网格模型和排水网络图。在计算流向和积累之前，首先填充了DEM中形成汇流点或盆地的区域。重要的是要注意，这些处理步骤‘填充’了低洼地形和撞击坑，以及DEM中的不想要的错误和噪声。这些‘填充’的区域在盆地中创建出延伸的模型流路径，这些路径被保留下来，以识别可能发生积水的地方，以及模型流向可能偏离地质观察的地方。
流域和贡献区域使用流积累模型上坡的两个位于奥克西亚盆地的汇流点进行计算。两个汇流点的位置（见图2）基于为整个MC-11四边形计算出的初步模型流积累路径与MOLA DEM中解析出的地质特征相对应。东部汇流点（‘扇’流域中的最低点）位于库古恩峡谷通道向奥克西亚盆地开口的最高沉积扇残留处。北部汇流点（盆地流域中的最低点）位于奥克西亚盆地北部的最低点，通往克里斯特平原。流域被定义为流积累为0的地方（即没有水可以从其流出的单元格）。汇流点、其流域和流积累路径被转换为Strahler河流阶数（Strahler，1957年）。