Investigating the source of unusual kaolinite-spinel float rocks in Jezero crater, Mars, and their implications for Mars crustal processes.
Candice Bedford
(1)
,
Clément Royer
(2)
,
Roger C. Wiens
(1)
,
Jeffrey R. Johnson
(3)
,
Briony H. N. Horgan
(4)
,
Adrian Broz
(4)
,
Olivier Forni
(5)
,
Stephanie Connell
(1)
,
Lucia Mandon
(6)
,
Bavani Kathir
(7)
,
Elisabeth M. Hausrath
(8)
,
Arya Udry
(8)
,
Juan Manuel Madariaga
(9)
,
Erwin Dehouck
(10)
,
Ryan Anderson
(11)
,
Pierre Beck
(12)
,
Olivier Beyssac
(13)
,
Elise Clave
(14)
,
Sam Clegg
(15)
,
Edward Cloutis
(16)
,
Thierry Fouchet
(17)
,
Travis Gabriel
(11)
,
Bradley Garczynski
(7)
,
Athanasios Klidaras
(1)
,
Henry Manelski
(1)
,
Lisa E. Mayhew
(18)
,
Jorge Núñez
(3)
,
Ann M Ollila
(15)
,
Susanne Schröder
(19)
,
Jim Bell
(20)
,
Justin I. Simon
(21)
,
Z. Uriah Wolf
(15)
,
Kathryn M. Stack
(22)
,
Agnes Cousin
(5)
,
Sylvestre Maurice
(5)
1
Purdue University [West Lafayette]
2 PLANETO - LATMOS
3 APL - Johns Hopkins University Applied Physics Laboratory [Laurel, MD]
4 EAPS - Department of Earth, Atmospheric, and Planetary Sciences [West Lafayette]
5 IRAP - Institut de recherche en astrophysique et planétologie
6 CALTECH - California Institute of Technology
7 WWU - Western Washington University
8 WGU Nevada - University of Nevada [Las Vegas]
9 UPV / EHU - Universidad del País Vasco [Espainia] / Euskal Herriko Unibertsitatea [España] = University of the Basque Country [Spain] = Université du pays basque [Espagne]
10 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
11 USGS - United States Geological Survey
12 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
13 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
14 DLR - Deutsches Zentrum für Luft- und Raumfahrt
15 LANL - Los Alamos National Laboratory
16 Department of Geography [Winnipeg]
17 LESIA - Laboratoire Energie Signal Images et Automatique [Univ Ngaoundéré]
18 University of Colorado [Boulder]
19 Institut für Optische Sensorsysteme
20 ASU - Arizona State University [Tempe]
21 JSC - NASA Johnson Space Center
22 JPL - Jet Propulsion Laboratory
2 PLANETO - LATMOS
3 APL - Johns Hopkins University Applied Physics Laboratory [Laurel, MD]
4 EAPS - Department of Earth, Atmospheric, and Planetary Sciences [West Lafayette]
5 IRAP - Institut de recherche en astrophysique et planétologie
6 CALTECH - California Institute of Technology
7 WWU - Western Washington University
8 WGU Nevada - University of Nevada [Las Vegas]
9 UPV / EHU - Universidad del País Vasco [Espainia] / Euskal Herriko Unibertsitatea [España] = University of the Basque Country [Spain] = Université du pays basque [Espagne]
10 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
11 USGS - United States Geological Survey
12 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
13 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
14 DLR - Deutsches Zentrum für Luft- und Raumfahrt
15 LANL - Los Alamos National Laboratory
16 Department of Geography [Winnipeg]
17 LESIA - Laboratoire Energie Signal Images et Automatique [Univ Ngaoundéré]
18 University of Colorado [Boulder]
19 Institut für Optische Sensorsysteme
20 ASU - Arizona State University [Tempe]
21 JSC - NASA Johnson Space Center
22 JPL - Jet Propulsion Laboratory
Résumé
Since Landing in Jezero crater, the Mars 2020 Perseverance rover has encountered over 4,000 light-toned float rocks (“float”) scattered across the dark-toned, mafic to ultramafic crater floor and volcaniclastic Jezero delta. To date (Sol ~1100), no outcrop of these light-toned float has been found. Here, we use imaging, chemical, and mineralogical data from the SuperCam and Mastcam-Z instruments onboard the Perseverance rover to constrain the potential origins of these unusual float.
Geochemical data acquired from the SuperCam laser induced breakdown spectrometer (LIBS) shows that these rocks are rich in Al2O3 (up to 44 wt%), with low abundances of MgO, FeOT, CaO and Na2O (averages <2 wt%) and an unusually high abundance of Ni, Cr, and Cu. Al2O3 abundances in these rocks are negatively correlated with SiO2 and hydration. Mineralogical data provided by SuperCam Visible Near-Infrared spectrometer show that the main minerals present in these rocks are likely kaolinite (strong signature in one target) and spinel, with potential accessory sulfates, zeolites, Al-smectite/illite, and hydrated silica or alumina.
Kaolinite horizons overlying Fe/Mg smectite clay horizons have been detected in multiple places in the Jezero crater watershed suggesting that a possible formation mechanism for the high Al2O3 abundances and low MgO, FeOT, CaO, and Na2O, and the mineralogical observation of kaolinite could be due to pedogenic leaching in a warmer and wetter ancient Mars [1]. However, the low hydration observed by both LIBS and IR spectra in many of these targets suggests they are rich in metakaolinite, a metastable dehydroxylated kaolinite. Temperatures from 450-700°C are required to form metakaolinite [2]. Spinel is also known to form from high temperature metamorphism of Al-bearing rocks [e.g., 3]. Possible sources of heat in the Jezero crater watershed or crater rim include impact or volcanic processes. Due to the presence of a kaolinite-bearing megabreccia block and several detections of light-toned boulders on the Jezero crater rim in long-distance images, we suggest impact metamorphism of a kaolinite weathering horizon is the most likely source of these light-toned float.
[1] Ehlmann et al., 2009 https://doi.org/10.1029/2009JE003339
[2] Sperinck et al., 2011 https://doi.org/10.1039/C0JM01748E
[3] Wang et al., 2021 https://doi.org/10.1007/s00710-021-00743-1