COMPARISON OF EOLIAN DUST COMPOSITION AT GALE AND
JEZERO
J. Lasue, IRAP, CNRS, Université de Toulouse, UPS-OMP, Toulouse, France (jlasue@irap.omp.eu), P. Y.
Meslin, A. Cousin, O. Forni, O. Gasnault, S. Maurice, P. Pilleri, W. Rapin, IRAP, CNRS, Université de Toulouse, UPS-OMP, Toulouse, France, R. Anderson, U.S. Geological Survey, Flagstaff, Arizona, USA, P. Beck,
Univ. Grenoble Alpes, CNRS, IPAG, France, S. M. Clegg, P. Gasda, Los Alamos National Laboratory, Los
Alamos, New Mexico, USA, R.C. Wiens, Purdue University, West Lafayette, Indiana, USA E. Dehouck,
Université de Lyon, UCBL, ENSL, CNRS, LGL-TPE, Villeurbanne, France, J. Frydenvang, University of Copenhagen, Denmark, Los Alamos National Laboratory, Los Alamos, New Mexico, USA, E. Hausrath, University of Nevada, Las Vegas, USA, S. Le Mouélic, LPG, CNRS, Nantes, France and the SuperCam team.

Introduction: On February 18th 2021, the
NASA Perseverance rover landed at Jezero crater,
Mars, a 50 km Noachian-aged lake system located on
the western side of the Isidis impact structure. The
geomorphology of the crater indicates the past presence of a fluvial delta with associated inlet and outlet
valleys and infrared observations from orbit have
detected the presence of carbonates, mafic and hydrated minerals [1]. Since its arrival at the Octavia E.
Butler landing site, the rover has explored about
7 km away from its initial landing position and has
analyzed the local bedrocks [2] and soils [3, 4] surrounding it.
Instruments: Located on the top of the mast of
the Perseverance rover is SuperCam, a multitechniques remote sensing instrument able to acquire
high resolution color images, passive visible/nearinfrared, laser-induced breakdown spectroscopy
(LIBS) and Raman spectra, and including also a microphone [5, 6]. The LIBS technique is similar to the
one used by ChemCam onboard the Curiosity rover,
which has been exploring Gale crater since 2012: a
series of 30 powerful laser pulses at 1064 nm ablates
targets at a distance of few meters, inducing a plasma
spark, the light of which is analyzed by spectroscopy
to determine its elemental composition (e.g. [7]).
During such an analysis, the spectra obtained
from the first five laser shots at each location are
contaminated by dust deposited on the surface of the
rock targets [8] and these spectra are usually removed from further analysis [9]. These spectra present a very homogeneous composition that is different from those of the underlying targets and from
those of the surface of ‘fresh’ targets such as abraded
patches or drill hole walls. As such, they have been
interpreted to represent an analysis of eolian dust
deposited over time on the surface of Mars [10].
In this study, we compare the spectral results obtained with the SuperCam first shots on the targets
analyzed at Jezero crater with the average first shot
spectra obtained by ChemCam on the rock targets at
Gale Crater to determine to which extent the spectra
correspond to a global eolian dust cover or to local

material contributions.
Method: We have used all the LIBS first shot
spectra acquired since the landing of Perseverance
over the first 300 sols of the mission on targets that
were not disturbed by the rover operations. Therefore, abraded targets, drill holes and calibration targets have been removed from the analysis. This corresponds to ~1300 different spectra processed by
denoising, background removal, wavelength calibration, and correction for instrument response [9]. The
average spectrum obtained from these data can then
be appropriately compared with the average first shot
spectrum obtained by ChemCam at Gale crater,
which was built over 1500 sols (~ 8500 spectra) [10].
There is about an order of magnitude difference
between the number of first shots spectra acquired by
SuperCam and ChemCam at this time, so we can
expect the SuperCam results to be less representative
than the ChemCam ones, but averaging more than
1000 spectra should already give reasonable statistics
for each instrument.
Results: After normalizing the spectra to their
total intensity, it is possible to superpose them as
shown in Figure 1. The first shots average LIBS
spectra superposition indicates strong similarities in
major element compositions The only disparity
comes from stronger Mg and Ca lines in the
SuperCam signal, which are possibly due to a contribution from local rocks and soils, as Ca-rich pyroxene and olivine have been detected amongst the local
rocks minerals [2, 11, 12]. The alkali do not present
very strong differences. The minor elements, such as
H (highlighted in Figure 1), Li, Mn, Cr, also present
peaks with intensities similar to the ones detected on
the ChemCam spectra, indicating a similar level of
hydration and minor elements contents of the dust
fraction at Jezero and at Gale. The H content also
appears related with the presence of alteration coatings on the surface of rocks at Jezero [13].

Mg
Si

Fe
Al

Ti

Ca

Conclusions: The average of the first LIBS shot
spectra acquired by SuperCam at Jezero crater compare very well with the average spectrum of
ChemCam’s first shots at Gale crater. The intensity
and ratios of the emission lines in the two average
spectra are very similar confirming the probable
global mixing of the eolian dust deposited all over
the surface of Mars. Some differences in Fe, Mg and
Ca content could be due to local contributions by
high Ca-pyroxene and olivine detected at Jezero.
Additional constraints might be obtained using
passive infrared spectra acquired before the LIBS
shots. Further analysis of this global extremely fine
material will be available in the laboratory since any
sample collected by the mission and returned to
Earth will provide some amount of eolian dust cover
on the surface of the bedrocks and since regolith
samples will also be acquired. This will enable critical additional information about this global dust
phase, and its implications for past climate, surface
processes, and future exploration

H
C

Figure 1: Comparison of average first shots LIBS spectra of
ChemCam at Gale Crater ([10] in red) and average first shots
LIBS spectra of SuperCam at Jezero Crater (in blue). A) UV
range, B) blue-violet range, C) Orange range with H emission line
comparison.

While the rocks analyzed by SuperCam at Jezero
crater appear visually to be less covered by dust than
the ones seen at Gale crater, our analysis indicates
that the rocks studied at Jezero remain covered by a
thin layer of homogeneous material similar in composition to the eolian deposited dust. This result is
consistent with a global mixing of the eolian dust
cover on Mars, or possibly a single origin for the
eolian dust on Mars as proposed in previous studies
(e.g. [14, 15]).
Relationship with local soils at Jezero: Comparison between the spectra of Jezero soils and
eolian dust indicates a composition close to the finegrained soils (grain size < 1 mm, e.g. Sei sol 84, Fig.
2 top) but significantly different than the coarsegrained soils (grain size > 1 mm, e.g. A_Koo sol 72,
Fig. 2 bottom) with an elevated content in Ti for the
fine-grained soils and dust and an increase in Fe and
Mg content in the coarse-grained soils (also shown in
[3]) that could be linked to the local contribution by
comminution of local rocks. H content is more elevated in the fine-grained soils, at the same level as
seen for the eolian dust.

Figure 2: RMI mosaic of fine-grained soil Sei (sol 84) and
coarse-grained soil A_Koo (sol 72).

Acknowledgments: The Perseverance rover and
the SuperCam instrument were funded by NASA,
CNES and LANL.
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