Northern Xanthe Terra: Update on the Reference Site for the Exomars2022 Landing Site in Oxia Planum
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Northern Xanthe Terra: Update on the Reference Site for the
Exomars2022 Landing Site in Oxia Planum
T. Frueh¹, ², E. Hauber², S. Adeli², D. Tirsch² and A. Nass²
¹Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str.10, 48149 Münster, Germany, (thomas.frueh@uni-muenster.de),
²Institute of Planetary Research, German-Aerospace-Center (DLR), Rutherfordstr. 2, 12489 Berlin, Germany.
ESA’s ExoMars rover will land in the Oxia Planum (OP) region [1,2], which was chosen for its ancient age, evidence for the
sustained presence of water, the presence of layered deposits, and the potential for biosignature preservation [2]. While some of
the geological characteristics have been studied in detail [3-5], other aspects are less well understood. In particular, it is unclear
if the situation in OP is a unique one, or if the geologic setting is representative for Mars on a regional, or even a global scale. To
test the hypothesis that OP is representative for a circum-Chryse geologic setting, we selected a site in
northern Xanthe Terra (XT) to investigate key geologic features and compare them to Oxia Planum.
Here we present preliminary results of our mapping and geologic analysis.
© ESA/ATG medialab
Introduction EPSC 2021
T. Frueh et al.
ESA’s ExoMars rover will land in the Oxia Planum region (blue box in Fig. 1) [1,2], which was chosen for its ancient age, evidence
for the sustained presence of water, the presence of layered deposits, and the potential for biosignature preservation [2].
The selected study site in northern Xanthe Terra is marked with
the red box in Fig. 1. This site displays several characteristics
similar to Oxia Planum, making it a suitable reference site:
• Its location at the highland-lowland boundary at Chryse
Planitia, expressed as a gradual slope rather than a sharp
topographic step
• The presence of phyllosilicates [3]
• The proximity to fluvial features [4-6], e.g., fan or delta
deposits and various types of fluvial channels
• The abundance of remnant mounds or buttes [7]
For uniformity, mapping was performed in accordance with
the regional geological mapping of the Oxia Planum landing
Oxia Planum
site [8].
Xanthe Terra
Figure 1. Locations of the Xanthe Terra study site (red box; ~9 - 13.5°N/315 - 318.5°E)
and Oxia Planum (blue box) visualized on global topography (MOLA). Upper right is a
HRSC image mosaic of the study site. 2|6
Preliminary Map EPSC 2021
T. Frueh et al.
Legend • The elevation increases in height from north to
Chaotic Terrain south from approximately -2,960 m to -1,800 m.
• The highland material in the south (Fig. 2) is the
Outflow Channel oldest material present. Towards the north the
Ejecta units tend to get younger.
• The oldest and largest craters (> 10 km) are
Buttes completely infilled in the northern study area (Fig.
Mesas 1). The extent of infilling decreases from the
Chryse basin towards the south. A similar trend
Delta Capping Unit with a southeast orientation exists in Oxia
Light Plains Planum. The presence of infilled craters suggests
extensive sedimentation at northern Xanthe Terra
Dark Plains and Oxia Planum.
Highland Material • The outflow channel and the chaotic terrain are
the youngest units of the preliminary map.
• NW two arms of the Hypanis fan reach into the study area (Fig. 2). The fan
• interpreted
deposits were previously interpreted to be of deltaic origin [9,10], i.e., formed
beneath a standing body of water. The Hypanis delta is accompanied by a dark
capping unit [9-10] (Fig. 2).
Figure 2. Preliminary map of the study area (Note that this is a very early and simplified stage of
the map!). Certain boundaries are presented in lines and uncertain boundaries in dashed lines.
Uncertainty can be due to an early stage in the mapping progress, image quality, or due to the
occuring geology. The stratigraphic relationships between the different units is not completely
clear yet. 3|6
Remnant Mounds EPSC 2021
T. Frueh et al.
Mounds are present in the northern study region (Fig. 1,2) and increase in height and abundance towards the north, similar to the mounds
in OP [15]. The mounds appear dark in THEMIS nighttime infrared images. While they occur scattered throughout the northern study, some
mounds are concentrated at the rims of ancient filled craters (Fig. 1,2). Individual mounds, however, can be present within these ancient
craters. The diameters of mounds range from tens of meters to several kilometers. Their appearance is variable and resembles mesas,
rounded knobs/buttes, and “bread-crust-like features” (Fig. 3A). They vary in height and rounded buttes, for example, can be higher than mesas
in their immediate neighborhood (Fig. 3C). While most of the mounds do not show a layering, there are some individual mounds with a coarse
layering. Near the Hypanis delta, mounds seem to stand on top of a finely layered basis (Fig. 3B). Different phases of mound formation can´t be
ruled out. ESP_037783_1920_RED
B
Stratigraphic Relationships
• The ejecta of at least seven large craters (d > 5 km) covers
mounds partly.
• In some cases, wrinkle ridges are deforming overlying mounds,
while in other cases mounds seem to be unaffected by wrinkle A
ridges.
• Individual mounds can be present within ancient craters.
• Generally, mounds seem to stand on top of the delta (Fig. 3B)
[9,10] and the shape of the delta does not seem to be C
influenced by the mounds. However, the correlation between
the Hypanis deposits and the mounds can be conflicting, but at
least some of the mounds seem to be younger then the
Hypanis delta.
• The eastern outflow channel cuts through several mounds and Figure 3. (A) shows the three different mound appearances. (B) Butte with coarse
there are no mounds present within the outflow channel. layering (white arrow) on top of a layered basis near the Hypanis Delta. (C) 3D
model (CTX DEM) of remnant mounds in the study area. 4|6
Phyllosilicates EPSC 2021
T. Frueh et al.
Phyllosilicates are widespread in OP [4-6] and are the main target of the ExoMars rover. Apart from their spectral signature, they are also
characterized by a bright THEMIS nighttime IR signature (Fig. 4) and a polygonised texture at HiRISE scale (Fig. 4BC). A global-scale search for
chemical alteration signatures revealed the presence of Fe/Mg phyllosilicates in northern XT, marginal to Chryse [4].
• At least two different phyllosilicate-bearing units are present in A
this region. The most widespread is a light and layered unit (Light
Plains, Fig. 2, 4B), which is partly eroded, exposing a darker
material underneath (Dark Plains, Fig. 2,4C). B ESP_055400_1905_RED
• NW – SE orientated small dunes and periodic bedrock ridges (Fig.
4B, white arrow), a type of aeolian erosional landforms which is
ubiquitous in the clay-bearing plains of OP [14], are present on
top of the darker unit.
• HiRISE coverage of both units shows distinct polygonised textures.
While the orientation of the polygon margins in the light plains is
random, the polygons in the dark plains have a preferential NW C
trending orientation (Fig. 4BC). ESP_066161_1905_RED
• The phyllosilicate-bearing plains are overlain by a widespread
unit, which seems to be present in most of the northern study
area. Figure 4. (A) THEMIS nighttime IR
• The phyllosilicate bearing units are older than the ancient, now image of the southern study
filled craters and are, therefore, one of the most ancient units in area. (B) HiRISE image of the
the study area. dark plains. (C) HiRISE image of
• Several fluvial features, i.e., small channels, inverted channels and the light plains (Red dashed lines
highlight the polygonization).
washed-out morphologies indicate a wet and fluvial history.
5|6
Conclusion and References
EPSC 2021
T. Frueh et al.
Conclusion: Northern Xanthe Terra and Oxia Planum share various geological characteristics (e.g., sedimentary fans,
phyllosilicates, remnant mounds) and a comparable location at the lowland-highland boundary at Chryse Planitia. These
similarities enable a comparison between both sites and a testing of hypotheses related to the ExoMars rover landing site.
[1] Vago, J. L. et al. (2015) Sol. Syst. Res., 49, 538–542 [9] Fawdon et al. (2018) EPSL, 500, 225–241
[2] Bridges, J. C. et al. (2018), LPS XLIX, Abstract #2177 [10] Adler, J. B. et al. (2019) Icarus, 319, 885–908
[3] Vago, J. L. et al. (2017) Astrobiol., 17, 471–510 [11] McNeil, J. et al. (2021) LPSC, 52, Abstract #2548
[4] Carter, J. et al., (2013) J. Geophys. Res., 118, 831–858 [12] Ivanov, M. A. et al. (2020) Sol. Syst. Res., 54, 1-14
[5] Quantin-Nataf, C. et al. (2021) Astrobiol., 21, 994-1013 [13] Molina, A. et al. (2017) Icarus, 293, 27-44
[6] Mandon, L. et al. (2021) Astrobiol., 21, 464-480 [14] Silvestro, S. et al. (2021) GRL, doi: 10.1029/2020GL091651
[7] Carter, J. et al. (2019) Ninth Int. Conf. Mars, Abstract #6175 [15] McNeil, J. D. et al. (2021) J. Geophys. Res., 126, doi: 10.1029/2020JE006775
[8] Hauber, E. et al. (2009) Planet. Space Sci., 57, 944–957
How to cite: Frueh, T., Hauber, E., Adeli, S., Tirsch, D., and Nass, A.: Northern Xanthe Terra: Update on the Reference Site for the Exomars2022 Landing Site in Oxia
Planum , European Planetary Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-615, https://doi.org/10.5194/epsc2021-615, 2021.
© ESA/ATG medialab
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