Pan, Lu

Quantin-Nataf, Cathy

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Regional geological context of the InSight landing site from mineralogy and stratigraphy

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Regional geological context of the InSight landing site
from mineralogy and stratigraphy
Lu Pan, Cathy Quantin-Nataf
To cite this version:
Lu Pan, Cathy Quantin-Nataf. Regional geological context of the InSight landing site from mineralogy
and stratigraphy. 49th Lunar and Planetary Science Conference, Mar 2018, The Woodlands, TX,
United States. ￿hal-02284121￿
REGIONAL GEOLOGICAL CONTEXT OF THE INSIGHT LANDING SITE FROM MINERALOGY 
AND STRATIGRAPHY.  L. Pan1 and C. Quantin1, 1Laboratoire de Géologie de Lyon, Université Claude Bernard 
Lyon 1 (2 rue Raphaël Dubois, Bâtiment GEODE, Villeurbanne, 69622. lu.pan@univ-lyon1.fr). 
 
Introduction: Planned to launch in May 2018, the 
InSight (Interior Exploration using Seismic Investiga-
tions, Geodesy and Heat Transport) robotic lander will 
explore the interior of Mars with a set of geophysical 
instruments [1-2]. Orbital data for the InSight landing 
site may provide crucial information on the regional 
context, rock properties and potential structural discon-
tinuities in the crust, which can be utilized to better in-
terpret the future seismic data collected by SEIS (Seis-
mic Experiment for Interior Structures) instrument on 
board InSight lander. Complementary to the previous 
studies on the surface properties in the landing ellipses 
[3-4], here we present a study on the regional geologic 
context of the landing site using a combination of orbital 
datasets and discuss the interpretation for the lithology 
and structure in the subsurface of the landing site.  
Geologic context: Situated between the Elysium 
volcanic structure and the dichotomy boundary, the In-
Sight landing site region has been shaped by the early 
formation and subsequent modification of the Martian 
dichotomy. The landing site is situated in an Early Hes-
perian transition unit [5-6], inferred to be volcanic in 
origin [3], overlain by the Elysium Mons volcanic unit 
[7] and younger lavas from Cerberus Fossae [5,7] to the 
north and the Medusae Fossae Formation to the east [8]. 
The surface of the landing site is covered by >3 m thick 
regolith, evidenced by the onset diameter of small rocky 
ejecta craters [4]. As a consequence, this investigation 
is focused on the limited exposures in the craters and 
local scarps in this region.  
Method:  We analyzed 79 CRISM (Compact Re-
connaissance Imaging Spectrometer for Mars) targeted 
images (18-36 m/pixel, 438 channels) in the landing site 
region (125°E to 145°E, 2°S to 15°N), following the 
data processing method in the previous northern low-
lands survey [9]. For locations where subsurface miner-
alogy is detected, we analyzed the accompanying 
HiRISE (High Resolution Imaging Science Experi-
ment) and CTX (Context Camera) images to investigate 
the correlation of the mineral detections with morpho-
logical units. The annual median thermal inertia of rel-
evant units is derived from measurements by the Ther-
mal Emission Spectrometer [10]. 
Results: Mafic detections in the volcanic units. Oli-
vine spectral signatures with weak absorptions are de-
tected on small craters rims close to the landing site, on 
the ridged plains unit (Fig. 1). The mineral detection is 
well-correlated with the bedrock exposure on the crater 
wall. The olivine-rich composition; surface expression 
of wrinkle ridges and the relatively older age compared 
to nearby volcanic units [5-6] imply their relation to the 
Hesperian lava flow units widespread in the northern 
lowlands [11-13]. Both olivine and low-calcium pyrox-
ene are found in a small crater within the Elysium Mons 
unit to the north of the landing ellipse, indicating either 
a different composition or heavier dust cover masking 
pyroxene absorptions in the ridged plains unit. More de-
finitive olivine and clay detections are found in the tran-
sitional unit close to the dichotomy, which could be the 
remnants of highlands materials, possibly of similar 
origin as the adjacent stratigraphy in the Sharp-Knobel 
watershed [14].  
Phyllosilicate detection and layered unit in a 50-km 
crater. Of particular interest is the Fe/Mg phyllosilicate 
identified in the central peak of a 50-km crater on the 
southwest flank of Elysium Mons. The phyllosilicate 
detection based on the 2.3 and 1.9 µm bands show the 
strongest absorptions in a topographic depression within 
the central peak. Similar spectral features with weaker 
absorptions are found in the adjacent central peak, 
which consists of a fragmented unit characterized by 
relatively light-toned features and heavily eroded mor-
phology (Fig. 2C-D). The alternating resistant (cliff-
forming) and friable (slope-forming) layers in this unit 
form an irregular cliff-bench morphology, exhibiting 
Figure 1: Geological map of the InSight landing site vicinity based on 
[6], with major geological units labeled and inferred age of each unit 
given in brackets (Am: Amazonian, Hr: Hesperian, N: Noachian). Stars 
show the mineral detections from CRISM data.  
1918.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
extensive layering of <10 m thick. The fragments of 2-
5 meters in size within the unit show evidence of little 
to no relative displacement (Fig. 2E).  
Discussion:  Possible origins of layered units. The 
clay-bearing unit in the central peak of a 50-km crater 
in the Elysium volcanic unit, is found with light-toned, 
cliff-bench morphology, consistent with the attributes 
of sedimentary rocks identified elsewhere on Mars [15]. 
Though the morphology resembles certain locations in 
the lower member of the Medusae Fossae Formation 
[16], the unit has distinctively higher thermal inertia (up 
to 500-1000 J m-2 K-1 s-½) than that of the Medusae Fos-
sae Formation.  
The feature of incipient fracturing (Fig. 2E) in the 
layers suggests they likely result from the structural up-
lift of a homogeneous rock mass at the impact event, 
instead of deposition at a later stage. The original depth 
of the central peak unit is >3-4 km, inferred from the 
size of the impact crater. Such layering units may form 
via subaerial (aeolian, volcaniclastic) or subaqueous 
processes before the emplacement of Elysium Mons la-
vas. The detection of Fe/Mg phyllosilicates associated 
with the central peak indicates aqueous alteration has 
occurred, which may be directly related to the presence 
of water during deposition. Alternatively, the layering 
structure and fragmentation in the unit could make it 
more susceptible to alteration after its deposition or ex-
cavation by the impact. Though the exposure is limited, 
it is possible that such unit is more extensive within the 
subsurface of Elysium Planita. Other large craters in the 
landing site vicinity also show possible detections of hy-
drated minerals, but the absorptions are obscured, likely 
due to a combination of noise and dust mixing. 
Inferred stratigraphy and implications for InSight. 
The overall stratigraphy of the landing site shows a gra-
dational sequence which becomes younger toward Ely-
sium Mons. This analysis suggests a clay-bearing sedi-
mentary unit underlies lava flows of several kilometers 
thick and a regolith layer close to the InSight landing 
site. The presence of these different geologic units in the 
subsurface of the landing site can result in variations in 
density or seismic anisotropy, which may be analyzed 
using data collected by the seismic instrument on board 
InSight lander. 
Future work: To better understand the origin of the 
layered unit, further analysis will focus on its distribu-
tion and the thickness and orientation of the layers 
through continued survey of HiRISE images and digital 
elevation models. We will also extend the investigation 
to regions around Elysium Mons and the adjacent high-
land crust, to gain a wider view of crustal structure and 
geologic history of the InSight landing site vicinity. 
Acknowledgement: This project has received funding 
from the European Union’s Horizon 2020 research and inno-
vation programme under the Marie Sklodowska-Curie grant 
agreement No. 751164. 
References: [1] Banerdt W.B. et al. 
(2013) LPS XLV Abstract #1915. [2] 
Banerdt W. B. et al. (2017) LPS XLVIII Ab-
stract #1896. [3] Golombek M., et al. (2017) 
Space Sci. Rev. 211, 1-4, 5-95. [4] Warner 
N. H. et al. Space Sci. Rev. 211, 1-4, 147-
190.  [5] Tanaka K. L., Chapman M. G. and 
Scott D. H. (1992) USGS No. 2147. [6] Ta-
naka K. L. et al. (2014) Planet. Space Sci 
95, 11-24. [7] Vaucher J. et al. (2009) Ica-
rus 204, 2, 418-422. [8] Kerber L. and Head 
J. W. (2010) Icarus 206, 2: 669-684. [9] 
Pan et al. (2017) JGR Planets, 122, 9, 
1824-1854. [10] Putzig et al. (2013) AGU. 
[11] Head J. W., Kreslavsky M. A. and Pratt 
S. (2002) JGR Planets 107, E1. [12] Salva-
tore M. R. et al. (2010). JGR Planets, 
115(E7). [13] Ody, A. et al. (2013) JGR 
Planets 118, 2: 234-262. [14] Ehlmann, B. 
L. and Buz J. (2015) GRL 42, 2, 264-273. 
[15] Malin, M. C. and Edgett K. S. (2000) 
Science 290, 5498, 1927-1937. [16] Zim-
belman J. R. and Griffin L. J. (2010) Icarus 
205, 1, 198-210. 
 
Figure 2: Layered units wi th phyllosilicates in unnamed large crater central peak. A. CRISM 
false color image overlain by spectral parameter map highlighting phyllosilicate detections. B. 
Type spectra of phyllosilicate detections in the central peak. C-D. Cliff-bench morphology of 
the central peak layered unit.  E. Details of the fragmentation of the layered unit. 
1918.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)


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Regional geological context of the InSight landing site from mineralogy and stratigraphy

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