SPECIAL ISSUE - RESEARCH ARTICLE
Mine alogy o he LAR 12095 Ma ian she go i e as
de e mined by mic o-Raman and mic o-X- ay luo escence
spec oscopies
Jenni e Huidob o | Julene A amendia | C is ina Ga cía-Flo en ino |
I a xe Poblaci
on | Kepa Cas o | Go ka A ana | Juan Manuel Mada iaga
Depa men o Analy ical Chemis y,
Uni e si y o he Basque Coun y
(UPV/EHU), Bilbao, Spain
Co espondence
Jenni e Huidob o, Depa men o
Analy ical Chemis y, Uni e si y o he
Basque Coun y (UPV/EHU), Ba io
Sa iena s/n, 48940 Leioa, Spain.
Email: [email p o ec ed]
Funding in o ma ion
Na ional Science Founda ion (NSF);
NASA; Raman On Ma s p ojec ,
G an /Awa d Numbe :
PID2019-107442RB-C31; Spanish Agency
o Resea ch; S a egic P ojec “Te es ial
and Plane a y Al e a ion P ocesses”,
G an /Awa d Numbe : UPV/EHU
PES18/57; UPV/EHU
Abs ac
In his wo k, he geochemical cha ac e iza ion o he oli ine-phy ic Ma ian
she go i e LAR 12095 was pe o med by using wo complemen a y analy ical
echniques: mic o-Raman and mic o-ene gy dispe si e X- ay luo escence
spec oscopies. Thanks o his me hodology, oli ine, py oxene, and ilmeni e
we e de ec ed as p ima y mine als om Ma s. Maskelyni e, hema i e, ana ase,
ch omi e, me illi e, oxidized mackinawi e, py ho i e, elemen al sul u , ma -
casi e, ja osi e, epsomi e, and gypsum we e classi ied as seconda y mine als.
The majo no el y o his wo k is ha al e a ions unde anae obic and ae obic
condi ions o S-bea ing mine als can be app ecia ed. In his sense, p ima y
sul ides we e al e ed o seconda y sul ides, elemen al sul u and sul a es unde
he oxygen- ee Ma ian a mosphe e. Howe e , in he Ea h's oxidizing a mo-
sphe e, p ima y sul ides a e wea he ed o i on oxides, such as hema i e. In
addi ion, i should be highligh ed ha he p esence o ilmeni e, mackinawi e,
elemen al sul u , and ja osi e has been epo ed o he i s ime in his
me eo i e.
KEYWORDS
LAR 12095 Ma ian me eo i e, Ma s, Ma ian sul u cycle, mine alogy
1|INTRODUCTION
Resea che s s udy he o ma ion and e olu ion o plane s,
such as Ma s, by o bi e s, o e s, lande s, o s udying
ock samples. On he one hand, o bi e s ha e eco ded
emo ely he plane 's mine alogy, geomo phology, and
composi ion.
1
On he o he hand, o e s and lande s
ha e pe o med ieldwo k, using analy ical echniques
ha ha e been able o analyze in si u he chemis y and
mine alogy o Ma ian ocks and egoli h. Tables 2 and
3 o he Huidob o e al.
2
e iew show he p os and cons
o in si u analysis made by o e s, lande s, and labo a o y
echniques. I has been ound ha in si u measu emen s
ha e wo se de ec ion limi s, limi a ions o he analysis
due o en i onmen al condi ions, and lowe p ecision
and accu acy han labo a o y echniques. Thus, in o de
o ge be e esul s, ock samples should also be analyzed
in e es ial labo a o ies. Un il now, ocks om he
Recei ed: 7 No embe 2022 Re ised: 12 Janua y 2023 Accep ed: 15 May 2023
DOI: 10.1002/j s.6558
This is an open access a icle unde he e ms o he C ea i e Commons A ibu ion-NonComme cial-NoDe i s License, which pe mi s use and dis ibu ion in any
medium, p o ided he o iginal wo k is p ope ly ci ed, he use is non-comme cial and no modi ica ions o adap a ions a e made.
© 2023 The Au ho s. Jou nal o Raman Spec oscopy published by John Wiley & Sons L d.
1248 J Raman Spec osc. 2023;54:1248–1257.
wileyonlinelib a y.com/jou nal/j s
Ma ian su ace can only be ob ained om he ejec ed
ocks ha a i ed o he Ea h in he o m o me eo i es.
Ma ian me eo i es we e adi ionally di ided in o h ee
main g oups: she go i e, nakhli es, and chassigni es
(SNC). Mo eo e , SNC me eo i es ha e been con i med
o belong o Ma s on he basis o apped noble gas
composi ions ha ma ch wi h Ma ian a mosphe e.
3
The
majo g oup is ha o she go i e, which ep esen s he
83% o he o al s udied samples.
1
Howe e , he s udy o me eo i es p esen s a handicap,
and i is ha hey a e o en hea ily wea he ed because
hese samples a e mos ly ound in ho and cold dese s,
whe e hey ha e spen a conside able amoun o ime
exposed o he e es ial su ace condi ions. The e o e,
iden i ying he o igin o me eo i e mine als has become a
challenge because i is necessa y o di e en ia e be ween
p ima y, seconda y, and e es ial wea he ing mine als.
This classi ica ion can be made based on he mine als
al eady ound on Ma s by in si u analy ical echniques
and based on hei chemical al e a ions. Tha is, p ima y
mine als, as he name implies, a e hose ha a e o igi-
nally om Ma s and ha e no unde gone any al e a ion.
Seconda y mine als a e hose ha come om p ima y
mine als because hey ha e unde gone al e a ion p o-
cesses ha caused a chemical change. Finally, as me eo -
i es a e ound on he e es ial su ace, hey may su e
u he wea he ing p ocesses. Thus de ec ing wea he ing
mine als is c ucial o iden i y which a e he main p o-
cesses ha deg ade me eo i es on he Ea h.
These mine als in me eo i es, and hei classi ica ion,
can be de e mined using labo a o y analy ical ech-
niques, gi ing also in o ma ion abou he his o y o he
me eo i e and consequen ly he his o y o Ma ian su -
ace om whe e he me eo i e was ejec ed. This knowl-
edge will also help o analyze quickly he i s Ma ian
samples ha will a i e o he Ea h hanks o he Ma s
Sample Re u n (MSR) mission.
4
O e ime, adi ional analy ical echniques ha e been
adap ed o he e a o in si u space explo a ion. In ac ,
esea ch is always in p og ess in o de o imp o e accu-
acy, minia u iza ion, p ecision, eal- ime measu emen s,
au oma ion, powe consump ion, eliabili y o ope a ion
unde ex eme condi ions, and so o h.
2
Nowadays, mo e
sophis ica ed analy ical echniques ha e been used,
especially hose non-des uc i e ones wi h spec oscopic
imaging capabili ies, enhancing he cha ac e iza ion pos-
sibili ies o me eo i e samples a he mic ome ic le el.
In his wo k, he she go i e LAR 12095 was selec ed o
demons a e he use ulness o using only wo o hose new
non-des uc i e analy ical echniques o i s cha ac e iza-
ion: mic o-Raman spec oscopy, in he poin -by-poin and
imaging modes; and mic o-ene gy dispe si e X- ay luo es-
cence (μ-EDXRF) spec oscopy, mainly in he imaging
mode.
5
The combina ion o μ-Raman spec oscopy and
μ-EDXRF spec oscopy gi es highly ele an esul s o he
sample mine alogy, because hey p o ide he elemen al
and he molecula cha ac e iza ions espec i ely o he
me eo i e as well as he isualiza ion o he dis ibu ion o
mine als and elemen s on he su ace o he me eo i e.
Bo h echniques we e selec ed in o de o p o e ha
he i s in si u analy ical echnique on Ma s
(XRF spec oscopy), on boa d de Viking lande ,
6
and he
mos no el echnique o each Ma s (Raman spec os-
copy), on boa d he Ma s 2020 o e ,
4
a e a combina ion
o echniques ha gi e be e esul s when used
oge he .
7
In ac , bo h echniques a e implemen ed in
he las o e men ioned abo e. These echniques p e-
se e he sample due o hei non-des uc i e cha ac e
gi ing complemen a y esul s especially when he ele-
men al and molecula homogenei y need o be checked
o gua an ee ep esen a i eness o esul s.
8
The e o e, he o e all goal o his wo k is o cha ac-
e ize he mine alogy o he LAR 12095 Ma ian she go -
i e. Likewise, he e a e also di e en speci ic objec i es:
(1) o de e mine he p ima y, seconda y, and wea he ing
mine al phases; (2) o de ec he possible p ocesses occu -
ing on Ma s ha caused he al e a ion o p ima y o sec-
onda y mine als in LAR 12095 Ma ian me eo i e; (3) o
iden i y he e es ial p ocesses ha ha e wea he ed he
me eo i e; and (4) o p o e ha he combina ion o
Raman and μ-EDXRF spec oscopy is one o he simples
and bes pe o ming combina ions o s udy he mine al-
ogy o me eo i es.
2|EXPERIMENTAL
2.1 |Sample
The La kman Nuna ak (LAR) 12095 Ma ian me eo i e
was ound in 2012 in he La kman Nuna aks egion o
he T ansan a c ic Moun ains, Eas An a c ica, by he US
An a c ic Sea ch o Me eo i es p og am (ANSMET). The
weigh o he ini ial me eo i e was 133.13 g and i s
dimensions we e 5.5 3.8 3.4 cm. Howe e , i
was cu in o hin sec ions o mo e de ailed analysis. The
measu emen s in his wo k we e pe o med on a
hin sample ha weigh s 1.26 g and has dimensions o
1.3 1.0 0.2 cm, including he esin in which i is
embedded. Bo h polished su aces look simila o he
naked eye, ha ing a g eenish g ay ma ix wi h some da k
inclusions, sepa a ed by c acks and eins.
This sample was deli e ed o he IBeA Resea ch
G oup o he Uni e si y o he Basque Coun y
(UPV/EHU) by a loan ag eemen be ween NASA's
Johnson Space Cen e (JSC) and he UPV/EHU.
HUIDOBRO ET AL.1249
10974555, 2023, 11, Downloaded om h ps://analy icalsciencejou nals.onlinelib a y.wiley.com/doi/10.1002/j s.6558 by Uni e sidad Del Pais Vasco, Wiley Online Lib a y on [07/05/2024]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
The ini ial cha ac e iza ion classi ied i as a Ma ian
she go i e, acco ding o he Me eo i ical Bulle in.
9
Li e -
a u e and he Me eo i ical Bulle in epo s ha he LAR
12095 she go i e is composed by py oxene (61–62 ol%),
oli ine (16–17 ol%), and maskelyni e (21–23 ol%)
g oundmass. Mino phospha es (mainly me illi e, wi h
a e apa i e), oxides (1 ol%, ch omi e and Ti-magne i e),
and sul ides (1 ol%, mainly Fe- ich py ho i e) a e also
p esen . In addi ion, mic os uc u al ea u es o shock
me amo phism, including eins and da kened oli ine a e
also obse ed.
9–12
2.2 |Ins umen a ion
2.2.1 | Mic o-Raman spec oscopy
The molecula cha ac e iza ion was pe o med using a
Renishaw inVia con ocal mic o-Raman spec ome e
(Renishaw, UK). The analyses we e ca ied ou bo h in
single poin mode and in he spec oscopic imaging
mode. The ins umen is equipped wi h a 785 (Renishaw,
UK, RL785 wi h a nominal 45 mW ou -pu powe ) and
532 nm (Renishaw, UK, RL532C50 wi h a nominal
300 mW ou -pu powe ) exci a ion diode lase s and wi h
a CCD de ec o cooled by Pel ie e ec . In addi ion, he
ins umen is coupled o a Leica DMLM mic oscope
(B ad o d, UK), implemen ing a XYZ S age Con ol ool-
ba and equipped wi h a mic o-came a o sea ching he
poin s o in e es . 5N PLAN (0.12 NA), 20N PLAN
EPI (0.40 NA) lenses, and 50N PLAN (0.75 NA) long-
ange objec i e we e used o isualiza ion and ocusing.
The nominal powe o he sou ce can be modula ed
be ween 0.1% and 100% o he o al powe o a oid
he mo-decomposi ion o he sample. Fo his wo k, less
han 20% was always used o p ese e he sample. The
spec a we e ob ained in he ange o 150–1350 cm
1
,
wi h an a e aged spec al esolu ion o 1 cm
1
, accumu-
la ing se e al scans om each spec um o imp o e he
signal- o-noise a io.
The Raman images we e ob ained using he high-
esolu ion S eam Line™se up (Renishaw, UK) coupled
o he inVia Raman spec ome e . The con ol so wa e
mo es he sample benea h he lens o he inVia's mo o -
ized mic oscope s age, so ha he line is as e ed ac oss
he egion o in e es wi h a spa ial esolu ion down o
1μm and mo ing in he snake mapping mode. The da a
a e swep synch onously ac oss he de ec o as he line
mo es ac oss he sample and he spec a a e ead ou
con inuously, eco ding a Raman spec um a each pixel
o he line as e .
The a e age spec al esolu ion is 1cm
1
in he
spec al egion o wa enumbe s co e ed in hese
expe imen s. A he end, 2D Raman images a e ob ained
con aining indi idual Raman in o ma ion a pixel le el.
The inVia spec ome e was daily calib a ed
se ing he 520.5 cm
1
silicon line. Da a acquisi ion and
ea men we e ca ied ou by he Wi e™4.2 so wa e
package by Renishaw. The esul s we e in e p e ed by
compa ing he collec ed Raman spec a wi h Raman
spec a o pu e s anda d compounds o he public da a-
bases RRUFF
13
and bibliog aphy.
The measu emen pa ame e s (lase , lase powe ,
numbe o accumula ions, and he acquisi ion ime o he
spec a) we e op imized o each analysis. Al hough bo h
Raman lase s we e used, be e esul s we e ob ained wi h
he 532 nm lase . This was because he sample is mainly
silica e-bea ing mine als and he use o he 785 nm lase
p omo ed a luminescence phenomenon ha mask o he
Raman signals, hiding aluable molecula in o ma ion
14
as well as an o se in he baseline o he whole spec um.
2.2.2 | μ-EDXRF spec ome e
The elemen al cha ac e iza ion o he LAR 12095 Ma -
ian me eo i e was pe o med using bo h single poin
analysis and hype map capabili ies o he μ-EDXRF
spec ome e M4 To nado (B uke Nano GmbH, Be lin,
Ge many). This ins umen has a mic o- ocus side win-
dow Rh ube powe ed by a low-powe HV gene a o and
cooled by ai ha ex ends o a maximum cu en o
700 μA and ol age o 50 kV. I implemen s a XFlash sili-
con d i de ec o wi h 30 mm
2
sensi i e a ea and ene gy
esolu ion o 145 eV o he Mn K-αline. The mic ome ic
la e al esolu ion o he ins umen , 25 μm o he K-α
line, is achie ed hanks o he polycapila op ics. The spo
size a ies as a unc ion o he ene gy, being 17 μma
2.3 KeV and 32 μm a 18.3 KeV. The ocusing p ocess is
suppo ed by wo ideo mic oscopes, one o hem
explo es he sample unde a low magni ica ion (1 cm
2
a ea) whe eas he o he pe o ms he inal ocusing
(1 mm
2
a ea). As he ins umen can de ec elemen s
wi h an a omic numbe (Z) highe han 10 (s a ing om
he sodium), he measu emen s we e pe o med unde
acuum (20 mba ) o enhance he de ec ion o he ligh -
es elemen s. A decon olu ion o he signals in he sum
spec um ep esen ing he comple ely mapped a ea was
conduc ed au oma ically o cons uc he elemen al
images. A e ha , he dis ibu ion map o each elemen
was ep esen ed as a unc ion o he in ensi y o each
de ec ed elemen K
α
line, excep o Pb, using in his case
he L
β
line. Elemen al semi quan i a i e da a o hese
images can also be ob ained in he o m o a able, bu i
should be highligh ed ha hese esul s a e semi-
quan i a i e due o he me hod used is unspeci ic and is
1250 HUIDOBRO ET AL.
10974555, 2023, 11, Downloaded om h ps://analy icalsciencejou nals.onlinelib a y.wiley.com/doi/10.1002/j s.6558 by Uni e sidad Del Pais Vasco, Wiley Online Lib a y on [07/05/2024]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
based on he i ing o he elemen s de ec ed in he spec-
um. I quan i a i e da a should be equi ed, he me hod
would be alida ed wi h ce i ica e e e ence ma e ial. All
he spec a acquisi ion and he image cons uc ion we e
pe o med using he M4 TORNADO so wa e.
3|RESULTS AND DISCUSSION
The me hodology ca ied ou o he analysis o his
me eo i e consis ed on he ollowing s a egy. Fi s , he
elemen al cha ac e iza ion was pe o med by means o
he acquisi ion o μ-EDXRF maps on bo h su aces.
Thanks o he μ-EDXRF maps, i was possible o es ablish
coexis ence o elemen s and de ec ho spo s o in e es
o he subsequen molecula cha ac e iza ion by means
o poin -by-poin Raman analyses. Finally, when a end
was de ec ed and/o i he mine al dis ibu ion was sig-
ni ican ly in e es ing, Raman images we e pe o med.
In his way, he elemen al cha ac e iza ion was ca -
ied ou in bo h sides o he me eo i e and no elemen al
di e ence be ween hem was obse ed. Figu e 1shows
he 12 elemen s ha we e de ec ed in he sample.
Elemen s wi h a ela i e abundance highe han 10%
w . we e conside ed as majo elemen s, namely Fe, Si,
and Mg. Ca and Al we e ound as mino elemen s wi h a
ela i e abundance be ween 1 and 10% w . Finally, ace
elemen s (<1% w .) we e Mn, C , Ti, S, P, V, and Ni.
3.1 |Main mine al phases: Oli ine,
py oxene, and plagioclase
In Figu e 1, i is obse ed ha i on and magnesium coexis
in se e al a eas, o ming phenoc ys s. The e o e, in o de
o ind ou wha mine als we e in ol ed in hose g ains,
Raman analyses we e pe o med. The spec a ob ained a e
composed by he Raman bands (Figu e 2A) ha appea a
140 ( e y weak, w), 225 (weak, w), 304 (w), 400 (w),
436 (w), 584 (w), 625 (medium, m), 820 ( e y s ong, s),
849 ( s), 917 ( w), and 959 ( w) cm
1
,
13
which co espond
o he bands o oli ine [(Mg, Fe)
2
SiO
4
].
13
The li e a u e
15
con i ms ha he band posi ion o he double
(800–880 cm
1
) changes as a unc ion o he Mg/(Mg
+Fe) con en . Thus, his ac can be used o es ima e he
o s e i e (Fo, Mg
2
SiO
4
) and ayali e (Fa, Fe
2
SiO
4
) con en
in he oli ine g ains. Hence, acco ding o he To e-Fdez
e al.
15
equa ions and a e selec ing he main band
posi ion o all oli ine spec a ob ained, he o s e i e and
ayali e ange composi ion in he LAR 12095 is be ween
Fo
55.0
Fa
45.0
and Fo
60.4
Fa
39.6
, in ag eemen wi h li e a-
u e.
12
Once he poin -by-poin analyses we e done, a
Raman map o he cen al a ea was acqui ed. In his way,
he spec al ange 814–823 cm
1
was selec ed o ob ain
he oli ine dis ibu ion Raman image. As can be seen in
Figu e 2A (in blue), he dis ibu ion o oli ine co esponds
pe ec ly wi h he c ys als showing he highes con en o
i on in he elemen al dis ibu ion (Figu e 1).
In addi ion, Figu e 1shows ha silicon is he main
elemen ha composes he ma ix. The g oundmass was
cha ac e ized by Raman spec oscopy and he spec um
pa e n o py oxene [R
2
(Si,Al)
2
O
6
] (R: Mg, Fe, Ca, Al, Ti,
Mn, Na, K, o Li)
16
(Figu e 2B) was ound, being p esen
bo h high Ca- and low Ca-py oxenes. Low Ca-py oxenes
seems o be p edominan wi h Raman bands a 332 (m),
398 (m), 538 (w), 658 (shoulde , sh m), 672 (m), 940 ( w),
and 1003 ( s) cm
1
. Acco ding o he wo k o Wang
e al.,
17
his is a magnesium- ich py oxene wi h a Pbca o
P2
1/c
c ys al s uc u e. This is because he Raman spec-
um has wo double s, one in he 650–700 cm
1
egion
and he o he in he 300–400 cm
1
egion. Acco ding o
he wo k o Huang e al.,
18
his spec um co esponds o
a ens a i e- e osili e o hopy oxene [(Mg, Fe)SiO
3
].
Finally, on he Raman map ca ied ou in he middle o
he sample, he spec al in e al o a cha ac e is ic
py oxene band (668–680 cm
1
) was selec ed o ob ain he
py oxene Raman image (Figu e 2B, in ed). As seen,
py oxene can be conside ed he main mine al in he bulk
o he me eo i e in ag eemen wi h he ini ial esul s om
he Me eo i ical Bulle in.
7
Se e al Al- ich spo s (see Figu e 1) we e analyzed by
mic o-Raman spec oscopy and he spec a showed b oad
bands in 450–7000 cm
1
egion, which co espond o
some ype o plagioclase [NaAlSi
3
O
8
-CaAl
2
Si
2
O
8
].
14,19
Al hough Raman spec oscopy can iden i y di e en non-
shocked plagioclases, he plagioclase ound in his sample
is clea ly maskelyni e, because no seconda y bands in he
200–450 cm
1
egion we e ound (Figu e S1A).
19
FIGURE 1 Elemen al dis ibu ion o Fe, Si, Mg, Ca, Al, Mn,
C , Ti, S, P, V, and Ni in he LAR 12095 Ma ian me eo i e ob ained
by μ-EDXRF. The Fe phenoc ys s a e he b igh es a eas o he i on
map, which ma ch wi h hose o Mg. This ac allows hinking
abou he p esence o oli ine phenoc ys s.
HUIDOBRO ET AL.1251
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3.2 |Oxides: Hema i e, ana ase, ilmeni e,
and ch omi e
By means o bo h modes, single poin analysis and
Raman mappings, he oxides hema i e [Fe
2
O
3
],
20
ana ase
[TiO
2
],
21
ilmeni e [FeTiO
3
],
22
and ch omi e [FeC
2
O
4
]
22
we e also de ec ed.
The Raman bands posi ion o hema i e appea a
223 (w), 292 (m), 403 (m), 605 (w), and 1303 (b oad
and weak, bw) cm
1
(Figu e 3D).
20
This i on oxide was
unequi ocally iden i ied on Ma s, o he i s ime, in
1996 by he The mal Emission Spec ome e (TES) on
boa d he Ma s Global Su eyo spacec a .
23
In ac ,
ine-g ained hema i e gi es Ma s i s cha ac e is ic ed
colo , he eason why his plane is called he “Red
Plane .”Se e al s udies ha e con i med ha he p es-
ence o hema i e on Ma s is due o a wea he ing p o-
cess.
23,24
Tha is, on Ma s he e a e many i on- ich
mine als, so ha h ough chemical eac ions, hese
compounds a e wea he ed, in pa , o hema i e.
23,24
Thus, hema i e is conside ed a seconda y mine al
om Ma s.
The i anium oxide ana ase
21
is a me as able mine al
phase ( he low empe a u e polymo ph) o i anium
dioxide, which is e y well cha ac e ized and dis inc i e
om o he polymo phs by Raman spec oscopy because
i s peaks appea a 142 ( s), 194 (w), 396 (w), 517 (w),
and 639 (m) cm
1
(Figu e S1B).
21
I is well known ha
ana ase is usually a seconda y mine al de i ed om
o he i anium-bea ing mine als. In addi ion, i can be
de i ed om he wea he ing o ocks by hyd o he mal
p ocesses o om c ys al ac iona ion o igneous
samples.
25
In addi ion o hema i e and ana ase, o he oxides
we e iden i ied. The Fe-Ti-C -oxides ha e simila Raman
spec a pa e ns, which include a main band in he 600–
800 cm
1
ange, and ew mino peaks a lowe wa enum-
be s.
22
Knowing all majo and mino Raman peaks, i
would be possible o dis inguish be ween he di e en
Fe-Ti-C -oxides, bu when he S/N signal is low, i is
qui e di icul o do so. In his sample, many spec a wi h
a s ong band in he ange o he Fe-Ti-C oxides we e
ound and he seconda y Raman bands appea ed in di -
e en posi ions allowing us o dis inguish among
FIGURE 2 (A) Raman image o oli ine and i s Raman spec um. The image was ob ained using he in e al 814–823 cm
1
. (B) Raman
image o py oxene and i s Raman spec um. The image was ob ained using he in e al 668–680 cm
1
. Bo h spec a we e acqui ed wi h he
ollowing condi ions: 532 nm lase , 1800 L/mm g a ing, 3 s o exposu e ime, 2 accumula ions, 10% o lase powe , 5objec i e.
1252 HUIDOBRO ET AL.
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di e en Fe-Ti-C oxides. In his sense, he i s Fe-Ti-C
oxide ound ea u es he mos in ense band a 686 cm
1
,
whe eas he seconda y bands appea a 228 (m), 335 (m),
and 376 (w) cm
1
, which co espond o he cha ac e is ic
spec um o ilmeni e (Figu e 1SC).
22
The measu emen
condi ions: lase 532 nm, 6 s o exposu e ime, 20 accu-
mula ions, 5% o lase powe , and objec i e 5. The o e
Spi i o he Ma s Explo a ion Ro e Mission de ec ed
ilmeni e in he Guse C a e o Ma s by he alpha
pa icle-X- ay spec ome e and he Mössbaue spec om-
e e .
26
In ac , ilmeni e was de ec ed in he same ock as
py oxene, oli ine, hema i e, nanophases o i on oxides,
and magne i e.
26
This ac p o es ha ilmeni e is a p i-
ma y mine al om Ma s.
The o he Fe-Ti-C oxide ound has a b oad Raman
band a 684 cm
1
and a seconda y b oad peak a
560 cm
1
. Acco ding o he wo k o Wang e al.,
22
he
spec um ound ma ches pe ec ly wi h he ch omi e
spec um (Figu e S1D). The Raman posi ion o he main
band e eals he mola a io (C +Fe)/(C +Fe +Al).
22
In his case, Raman peak sugges s alues o 0.8–1.0. This
ange indica es ha he ch omi e ound may con ain
aces o aluminum, which is consis en because
μ-EDXRF images showed ha some imes aluminum
coexis ed wi h ch omium. In addi ion, magnesioch omi e
was also de ec ed hanks o i s Raman bands: 560 (m),
598 (m), 645 (s), 689 ( s), and 1363 (w, b).
13
Ma ian
o bi e s, o e s, and lande s ha e no ye ound ch omi e
on he ed plane . Howe e , he e a e many Ma ian
me eo i es
22,27
wi h ch omi e p esen .
In addi ion o he majo mine al phases and he
oxides ound, phospha es, sul ides, elemen al sul u , and
sul a es we e also de ec ed as mino mine al phases.
3.3 |Phospha e
As can be seen in Figu e S2A, whe e some elemen al
images we e o e lapping, some imes he dis ibu ion o
calcium, magnesium, and phospho us ma ch. In
hese poin s, he calcium phospha e me illi e [Ca
9
NaMg
(PO
4
)
7
]
28
was de ec ed by single Raman poin mode. I s
Raman spec um is cha ac e ized by he Raman bands
ha appea a 354 (w), 407 (m), 958 ( s), 975 ( s), and
1111 (m) cm
1
(Figu e S1E).
28
The e is no any epo
abou he p esence o me illi e on Ma s, bu i is a domi-
nan mine al in Ma ian me eo i es. Un o una ely, he
o igin o i s p esence in me eo i es is no ye ully es ab-
lished. Ne e heless, i is known ha whi locki e (p i-
ma y mine al om Ma s
29
) can be ans o med in o
me illi e by shock p ocesses. This leads us o hink ha
he whi locki e was ans o med in o me illi e in he
p ocess o me eo oid gene a ion. The e o e, me illi e
could be conside ed a seconda y mine al om Ma s.
3.4 |Sul u - ich mine al phases
In addi ion o he mine als seen so a , sul u - ich com-
pounds we e expec ed o be ound, because he elemen al
images o sul u and i on ma ch (see Figu e S2B). Almos
50 yea s ago, Viking missions e ealed ha Ma s has S-
and Cl- ich su ace egoli h, and since ha ime, sul u
has been con i med by in si u measu emen s made by
lande s and o e s, by emo e sensing obse a ions made
by o bi e s, and by analyses o Ma ian me eo i es in e -
es ial labo a o ies.
30
I is es ima ed ha mos p ima y
igneous sul u is concen a ed in sul ides, including
FIGURE 3 Raman spec a o (A) oxidized mackinawi e, (B) oxidized mackinawi e and b oad i on oxide bands, (C) oxidized
mackinawi e, py ho i e, and b oad i on oxide bands, (D) hema i e and (E) elemen al sul u and ma casi e. Measu emen condi ions:
532 nm exci a ion lase , 1800 L/mm g a ing, 10 s o exposu e ime, 10 accumula ions, 10% o lase powe , 50objec i e.
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py ho i e, a e chalcopy i e, cubani e, oili e, pen land-
i e, and py i e.
31
In addi ion o p ima y mine als, sul u
is also ound in a a ie y o seconda y mine al phases in
Ma ian me eo i es, such as seconda y sul ides, sul a es,
elemen al sul u , and impac glasses, among o he s.
31
A e unde s anding his, i is necessa y o emphasize
ha he sul u cycle domina es many geochemical p o-
cesses on Ma s. Du ing he o ma ion o Ma s, sul u
was dis ibu ed in he co e o o m a liquid Fe-(Ni)S
co e. Subsequen ly, he ans e o S o he c us
occu ed h ough olcano degassing, magma ism, and
hyd o he mal p ocesses, which esul ed in a conside -
able amoun o S a he su ace. Acco ding o Huidob o
e al.,
6
pho ochemical ac i i y and he p esence o oxidiz-
ing agen s led o apid o ma ion o S-bea ing mine als,
such as sul ides. I oxida ion con inued on Ma s wi hou
he p esence o a mosphe ic oxygen (anae obic condi-
ions), he p ima y sul ides may ha e oxidized o second-
a y sul ides,
32
elemen al sul u , and sul a es. In con as ,
i he oxida ion o sul u compounds occu s on Ea h,
unde oxygen p esence (ae obic condi ions), he esul s
is comple ely di e en , leading o he o ma ion o i on
oxides, such as hema i e, goe hi e, lepidoc oci e, among
o he s.
32,33
Su p isingly, bo h ypes o oxida ion, ae obic and
anae obic, we e obse ed in he LAR 12095 me eo i e.
Fi s o all, mackinawi e [ e agonal FeS, me as able]
33
was de ec ed and i is well known ha i s Raman bands
appea a 208 (s), 274 ( s), and 385 (s) cm
1
,
33
bu he
ones de ec ed expe imen ally appea a 214 ( s), 273 ( s),
and 382 (b, m) cm
1
(Figu e 3A). Mendili e al.
32
we e
able o obse e ha mackinawi e is a me as able i on sul-
u and is highly suscep ible o ans o m. In ac , i has
been p o en ha he main mackinawi e Raman bands
shi owa d highe wa enumbe s, un il he al e a ion
causes a change in he c ys al s uc u e om e agonal
o monoclinic [py ho i e, FeS, s able].
32
The e o e, as
he expe imen ally bands de ec ed ha e he same s uc-
u e as mackinawi e bu wi h a small displacemen
owa d highe wa enumbe s, i can be concluded ha
he compound ound is an oxidized mackinawi e
(see Figu e 3A).
Secondly, Figu e 3B shows he oxidized mackinawi e
oge he wi h he 385 and 582 cm
1
Raman bands,
32,33
which means ha he me as able i on sul ide o med in
anoxic condi ions on Ma s has s a ed o oxidize in he
p esence o oxygen, o ming he appea ance o he i s
i on oxide bands.
Thi dly, Figu e 3C shows he oxidized mackinawi e
wea he ing unde anae obic condi ions, whe e pa o
he mackinawi e has been ans o med o py ho i e.
32
Al hough he exac Raman peaks o py ho i e can a y
as unc ion o s oichiome y as well as wi h he deg ee o
o de ing, and e lec a ia ions in he FeS bond leng hs,
hei pa e n spec um is cha ac e ized by s ong peaks
close oge he below 400 cm
1
.
34
And he ones ob ained
in he labo a o y appea a 329, 363, and 396 cm
1
.
35
Finally, Figu e 3D shows he hema i e spec um,
which is he p oduc o he comple e al e a ion o i on
sul ides in he p esence o oxygen.
As men ioned abo e, anae obic oxida ion o p ima y
sul ides wi h high sul u inpu can p oduce seconda y
oxides o FeS
2
(py i e o ma casi e, FeS
2
, s able, and
me as able, espec i ely
6
), elemen al sul u [S
8
]
6
and
Fe
2+
sul a es.
36
Figu e 3E shows he Raman bands o
ma casi e and elemen al sul u , which a e 319 ( s) and
381 (s); and 149 (m), 219 (m), 244 (w), and 471 (m),
espec i ely.
6,13
Mo eo e , in his me eo i e, i was obse ed ha he
oxida ion in an anae obic en i onmen pe sis ed. Sul ides
and elemen al sul u con inued o oxidize o anhyd ous
sul a es, which can hyd a e h ough hyd o he mal ac i -
i y, leading o he o ma ion o hyd a ed sul a es. In his
sense, he i on sul a e ja osi e [KFe
3
(SO
4
)(OH)
6
]
37
was
de ec ed hanks o i s Raman bands ha appea a
139 (m), 224 (s), 300 (m), 355 (w), 434 ( s), 454 (m),
573 (m), 625 (m), 1007 ( s), 1051 (w), 1103 ( s), and 1153
(w) cm
138
(Figu e 4). On he Ea h, ja osi e o ms as he
esul o low- empe a u e acidic-oxida i e wea he ing o
i on-bea ing mine als in wa e p esence.
36,37
In addi ion,
FIGURE 4 Raman spec a o ja osi e, gypsum, and epsomi e. Measu emen condi ions: 532 nm exci a ion lase , 1800 L/mm g a ing,
10 s o exposu e ime, 3 accumula ions, 10% o lase pose , 50objec i e.
1254 HUIDOBRO ET AL.
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his compound was epo ed in 2004 by he Oppo uni y
o e a ine-g ained sedimen s o Me idiani Planum.
37
The e o e, he ja osi e o his me eo i e can be conside ed
as a seconda y mine al as well as a wea he ing mine al
phase.
As can be seen in Figu e S2C,D, he dis ibu ion o
sul u along he me eo i e also o en ma ch wi h he dis-
ibu ion o calcium and magnesium. In his way, wo
addi ional sul a es we e de ec ed by Raman spec oscopy:
gypsum [CaSO
4
.2H
2
O] and epsomi e [MgSO
4
.7H
2
O].
Bo h hyd a ed sul a es ha e been de ec ed in Ma s by he
Oppo uni y o e , he OMEGA on he Ma s Exp ess
o bi e , he Phoenix lande , he CRISM on he Ma s
Reconnaissance o bi e , among o he s.
39
Gypsum was iden i ied hanks o i s Raman bands:
133 (w), 183 (w), 224 (w), 328 (w), 416 (w), 435 (w),
495 (m), 620 (w), 674 (w), 1009 ( s), 1103 (w), 1138 (w),
and 1454 (w) cm
1
(Figu e 4). Epsomi e was de ec ed
h ough i s main Raman band ha appea s a
984 ( s) cm
1
(Figu e 4). These mine als a e coming om
a sul a e-al e a ion/e apo a ion p ocess and can be
o med in a wide a ie y o deposi ional en i onmen s.
Acco ding o li e a u e,
40,41
he p esence o hyd a ed sul-
a es on Ma s is due o sul u -bea ing wa e in e ac s
wi h Ca/Mg-bea ing mine als, lea ing gypsum and epso-
mi e as wa e e apo a ed.
The e o e, he gypsum and epsomi e o his me eo i e
may be due o he al e a ion o S-bea ing wa e and Ca-
bea ing mine als on Ma s o on he Ea h. As bo h min-
e al phases appea occasionally in some a eas in he su -
ace o he me eo i e and do no ha e a dis ibu ion along
he c acks, i seems ha bo h sul a es a e likely o ha e a
Ma ian o igin and ha a e no due o an a e wa ds e -
es ial wea he ing. A e ejec ion, bo h hyd a ed sul a es
p obably dehyd a ed, bu a e he me eo i e landing on
he An a c ica ices, bo h could be ehyd a ed again.
Thus, in he LAR 12095 Ma ian me eo i e, i has
been possible o e i y once again he di e en s ages, in
which sul u can be ound om he mos educed o m o
he mos oxidized.
All he p oposed eac ions can be seen shown in
Figu e 5. The p ima y Ma ian sul ides can ollow h ee
di e en pa hways. The i s one consis on o ming
seconda y sul ides due o p essu e changes. The second
one is he anae obic ou e, which occu s on Ma s, due o
oxidizing agen s seconda y sul ides, elemen al sul u and
elemen al i on a e p oduced. The hi d possibili y is ha
p ima y o seconda y sul ides may be oxidized unde
ae obic condi ions, which occu s on Ea h, gene a ing
i on oxides, such as hema i e, and sul u oxides (SOx).
Finally, he elemen al sul u and he seconda y sul-
ides can be al e ed un il anhyd ous o hyd a ed sul a es.
This p ocess may occu due o hyd o he mal condi ions
on Ma s o due o e es ial wea he ing.
4|CONCLUSIONS
By means o Raman expe imen s, pe o med on ho spo s
selec ed a e a μ-EDXRF mapping o he su ace, he
LAR 12095 she go i e was geochemically cha ac e ized.
I was ound ha he ma ix o he samples was mainly
composed by a g oundmass o ens a i e- e osili e o ho-
py oxene [(Mg,Fe)SiO
3
] and oli ine phenoc ys s embed-
ded in he ma ix. Bo h mine al phases a e classi ied as
p ima y mine als. Mo eo e , occasionally ilmeni e and
i on sul ides we e also ound as p ima y mine al phases.
As seconda y mine al phases, maskelyni e, hema i e,
ana ase, ch omi e, me illi e, oxidized mackinawi e, py -
ho i e, elemen al sul u , ma casi e, ja osi e, gypsum, and
epsomi e we e de ec ed.
Hema i e is p obably coming om he acidic-
oxida i e al e a ion o Fe-bea ing mine al phases, such as
i on sul ides. On he o he hand, i is well known ha
ana ase is a p oduc o he wea he ing o Ti-bea ing min-
e als unde hyd o he mal condi ions. E en hough he
p esence o me illi e in Ma ian me eo i es is no ye
ully p o en, i is belie ed ha me illi e comes om he
al e a ion o whi locki e due o p essu e shock du ing he
me eo i e o ma ion.
FIGURE 5 Possible al e a ions o p ima y Ma ian sul ides on Ma s as a unc ion o he mine als ound in he LAR 12095 Ma ian
me eo i e by mic o-Raman spec oscopy and mic o-EDXRF.
HUIDOBRO ET AL.1255
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The mos no el disco e y made in his me eo i e was
he wo di e en pa hs ha al e a ions o S-bea ing min-
e als can ake. Tha is, i is known ha he ans e o S
o he c us occu ed h ough degassing, magma ism, and
hyd o he mal p ocesses, which esul ed in a conside able
amoun o S a he su ace. Pa o hese gasses we e oxi-
dized unde anae obic condi ions, o ming he p ima y
sul ides. A his poin , he al e a ion o p ima y i on sul-
ides can ollow wo di e en pa hs, he wo ha ha e
been seen in his me eo i e. A his poin , he al e a ion
o p ima y Ma ian sul ides can ollow wo di e en
pa hs, he one ha occu s on Ma s unde anae obic con-
di ions and he o he ha occu s on Ea h unde ae obic
condi ions. Acco ding o he i s pa h, p ima y sul ides
ans o m in o seconda y sul ides, elemen al sul u and
sul a es (unde hyd o he mal condi ions) on Ma s.
Rega ding he second pa h, p ima y sul ides al e in o
di e en oxides on Ea h due o he oxidizing e es ial
a mosphe e. The esul ed mine al phases ob ained in his
me eo i e h ough he i s pa h we e mackinawi e, py -
ho i e, ma casi e, and elemen al sul u . In con as , i on
oxides such as hema i e we e ob ained as a esul o he
second al e a ion pa h.
Ja osi e was epo ed o be on Ma s by he Oppo uni y
o e , bu i s p esence on he ed plane comes as he
esul o low- empe a u e acidic-oxida i e wea he ing o
Fe-bea ing mine als in wa e p esence. Finally, epsomi e
and gypsum a e common sul a e-al e a ion/e apo a ion
p oduc s and a e o med in a wide a ie y o deposi ional
en i onmen s, so hey come om he in e ac ion be ween
S-bea ing wa e wi h Ca/Mg-bea ing mine als, o due o
he oxida ion o S-bea ing p ima y mine als.
No mine als ha e been ound ha would ce ainly
come om e es ial wea he ing. Howe e , he o igin o
ch omi e is no ye es ablished, because Ma ian o bi e s,
o e s, and lande s ha e no ound ch omi e in Ma s,
and many Ma ian me eo i es ha e ch omi e. The e o e,
ch omi e may be a p ima y mine al no ye epo ed, a
seconda y mine al, o a e es ial wea he ing mine al.
A e his cha ac e iza ion, i can be said ha he
objec i es we e sa is ac o ily ul illed. In addi ion, i has
been possible o e i y how mic o-Raman spec oscopy
(using bo h poin -by-poin and imaging modes), assis ed
wi h mic o-EDXRF imaging is a as and comple e way o
ca y ou he geochemical cha ac e iza ion o samples
ha canno be des oyed and hus i could be used on he
u u e cha ac e iza ion o Ma s Re u ned samples om
he upcoming MSR mission.
ACKNOWLEDGMENTS
All he au ho s a e g a e ul o NASA o p o iding access
o he LAR 12095 Ma ian me eo i e sample h ough he
loan ag eemen be ween NASA's JSC and he UPV/EHU.
US An a c ic me eo i e samples we e collec ed by he An -
a c ic Sea ch o Me eo i es (ANSMET) p og am, which
has been unded by Na ional Science Founda ion (NSF)
and NASA, and cha ac e ized and cu a ed by he Depa -
men o Mine al Science o he Smi hsonian Ins i u ion
and As oma e ials Cu a ion O ice a NASA's JSCe.
Jenni e Huidob o and I a xe Poblaci
on a e g a e ul o he
Basque Go e nmen and UPV/EHU, espec i ely, o hei
p e-doc o al con ac s. Julene A amendia is g a e ul o he
Basque Go e nmen Ma ía Zamb ano con ac , and
C is ina Ga cía-Flo en ino is hank ul o he UPV/EHU
pos -doc o al con ac . This wo k has been suppo ed
h ough he Raman On Ma s p ojec : “Con ibu ion o he
Raman spec oscopy o he explo a ion o Ma s and
Ma ian Moons: ExoMa s, Ma s 2020 and MMX missions
(RamOnMa s)”(G an No. PID2019-107442RB-C31),
unded by he Spanish Agency o Resea ch ( h ough he
Spanish Minis y o Science and Inno a ion, MICINN, and
he Eu opean Regional De elopmen Fund, FEDER), and
he S a egic P ojec “Te es ial and Plane a y Al e a ion
P ocesses”(G an No. UPV/EHU PES18/57), unded by
he UPV/EHU.
CONFLICT OF INTEREST STATEMENT
The au ho s decla e ha he e is no con lic o in e es
ha could be pe cei ed as p ejudicing he impa iali y o
he esea ch epo ed.
ORCID
Jenni e Huidob o h ps://o cid.o g/0000-0001-8302-
8583
C is ina Ga cía-Flo en ino h ps://o cid.o g/0000-0002-
0329-8012
I a xe Poblaci
on h ps://o cid.o g/0000-0002-9162-3734
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