Tissint Martian Meteorite: A Fresh Look at the Interior, Surface, and Atmosphere of Mars

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Science DOI: 10.1126/science.1224514
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Tissint Martian Meteorite: A Fresh Look at the Interior, Surface, and
Atmosphere of Mars
1,2,* 3 4 2 5 6 7
H. Chennaoui Aoudjehane , G. Avice , J.-A. Barrat , O. Boudouma , G. Chen , M. J .M. Duke , I. A. Franchi ,
8 7,9 7 5 10 2 4
J. Gattacecca , M. M. Grady , R. C. Greenwood , C. D. K. Herd , R. Hewins , A. Jambon , B. Marty ,
8 9,11,12 10 7 13 10
P. Rochette , C. L Smith , V. Sautter , A. Verchovsky , P. Weber , B. Zanda

+ Author Affiliations

*
To whom correspondence should be addressed. E-mail: chennaoui_h@yahoo.fr, h.chennaoui@fsac.ac.ma

AB S T R ACT

Tissint (Morocco) is the fifth Martian meteorite collected after it was witnessed falling to Earth. Our
integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite
similar to EETA79001A. Highly magnesian olivine and abundant glass containing Martian atmosphere are
present in Tissint. Refractory trace element, S and F data for the matrix and glass veins in the meteorite
indicate the presence of a Martian surface component. Thus, the influence of in situ Martian weathering can
be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering
features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic
ray exposure age of 0.7 ± 0.3 Ma, consistent with those of many other shergottites, notably EETA79001,
suggesting that they were ejected from Mars during the same event.

Demonstration in the early 1980s that an important group of meteorites was of Martian origin represented a
breakthrough in attempts to understand the geological evolution of Mars (1–3). Unfortunately, most of the samples
were collected long after their arrival on Earth and thus have experienced variable degrees of terrestrial
weathering (4). Even the few Martian meteorites that were collected shortly after their observed fall to Earth have
been exposed to organic and other potential contaminants during storage. Here we report on the Tissint Martian
meteorite, which fell on 18th July 2011 in Morocco (figs. S1 and S2). This is only the fifth witnessed fall of a
meteorite from Mars and therefore provides an opportunity to improve our understanding of processes that
operated on that planet at the time the meteorite was ejected from its surface.

The largest recovered stones from the Tissint fall are almost fully covered with a shiny black fusion crust (Fig. 1).
Internally the meteorite consists of olivine macrocrysts set in a fine-grained matrix of pyroxene and feldspathic
glass (maskelynite) (5) (figs. S3 to S6, tables S1 to S6). The matrix is highly fractured and penetrated by numerous
dark shock veins and patches filled with black glassy material enclosing bubbles (fig. S7). The petrology of Tissint
shows similarities to other picritic shergottites (an important group of olivine-rich Martian basaltic rocks), in
particular, lithologies A and C of EETA79001 (2). The grain density and magnetic properties of Tissint (fig. S8)
also match previous results from basaltic and picritic shergottites (6).

Fig. 1

The Natural History Museum (London) stone. This 1.1 kg stone
(BM.2012,M1) exhibits a black fusion crust with glossy olivines.
The olivine macrocrysts (pale green) and the numerous black
glass pockets and veins, are characteristics of this shergottite.
The scale is in cm.

1 de 5 11/10/2012 19:11


Tissint is an Al-poor ferroan basaltic rock, rich in MgO and other compatible elements (Ni, Cr, Co). Its major
element abundances are similar to those of the other picritic shergottites, especially EETA79001. Furthermore, key
−3
element ratios (wt%/wt%) such as FeO/MnO (39.7), Al/Ti (7.2), Na/Ti (1.41), Ga/Al (3.9 10 ), Na/Al (0.20) (3, 4,
17
14) and Δ O (+0.301‰) (fig. S9) (7) are also typical of Martian meteorites. The average composition of the black
glass (tables S7 and S8) is identical to a mixture of the major phases of the rock (augite, maskelynite and olivine:
50:20:30) with compositional variations reflecting incomplete dissolution of one phase or another (fig. S7). Among
minor elements in the black glass, chlorine is always below the detection level of EMPA (100 ppm), whereas
fluorine and sulfur exhibit variations in the range 0-4000 ppm and 0-6000 ppm respectively (5).

Like most other pictritic shergottites, bulk Tissint displays a marked depletion in light rare earth elements (LREE)
and other highly incompatible elements, such as Rb, Li, Be, Nb, Ta, Th and U (Fig. 2). Its Lu/Hf ratio (0.2) is in the
range of values measured for EETA79001 and other basaltic shergottites (0.1 to 0.2, e.g., (8)), and lower than
those of the picritic shergottites DaG 476/489, SaU 005 and Dhofar 019 (about 0.3, (9-11)). Although the sizes of
the two samples analyzed here are somewhat limited (0.49 g and 1.25 g), their trace element abundances are very
similar and so are likely to be representative of the whole rock composition, despite the irregular distribution of
olivine megacrysts.

Fig. 2

REE patterns: Top: Tissint in comparison with other depleted
picritic shergottites. Bottom: Black glass and groundmass-rich
fraction in comparison with enriched shergottite Zagami. Data
from (9-11). CI chondrite normalization values are from (24).

In order to evaluate the possible heterogeneity of this stone, we analyzed two additional samples: a
groundmass-rich sample (devoid of large olivine crystals, and weighing 181 mg) and a fragment of the same
glassy pocket selected for volatile analysis (40 mg). Both samples display markedly higher LREE abundances,
with REE patterns generally similar to those of the enriched shergottites, as exemplified by Zagami. However,
there is a minor, but analytically valid, positive Ce anomaly (Ce/Ce*=1.1) (Fig. 2) and the La/Nd, La/Nb and Th/La
ratios are higher than those of other enriched shergottites (fig. S10). These two samples indicate that a
LREE-enriched component, different from those previously recorded in other shergottites, is heterogeneously
dispersed throughout the matrix of Tissint.
48
The presence of short-lived V (T½=16 days), among other cosmogenic isotopes, demonstrates that the stones
th
we analyzed are from the fall of July 18 (table S10). We measured stable cosmogenic isotopes of He, Ne and Ar
in three aliquots, consisting of matrix-rich, glass-matrix mixed, and glass-rich separates (table S11). The Cosmic
3 21 38
Ray Exposure ages (CRE ages) computed for He , Ne , and Ar are 1.2 ± 0.4, 0.6 ± 0.2 and 0.9 ± 0.4 Ma
c c c
respectively, resulting in an average CRE age of 0.7 ± 0.3 Ma for Tissint. This age is in the range of CRE ages of
other shergottites, notably that of EETA79001 (0.73 ± 0.15 Ma (2)), suggesting that Tissint and other shergottites
were ejected during a single event. Nitrogen isotopes were analyzed together with the noble gases. The glass
15 15
aliquot displayed a well-defined excess of N, which persisted after correction for contribution of cosmogenic N
c
−13 15 15
(assuming a production rate of 6.7 ± 2.6 × 10 mol N/gMa) (12). This excess N is best explained by trapping
15 40
of a Martian atmospheric component (2). Using a δ N versus Ar/N correlation and taking a Martian atmospheric
15
value from the Viking measurements, of 0.33 ± 0.03 (13), we obtain a δ N value of 634 ± 60 ‰ (1σ), which
agrees well with the Viking measurement of 620 ± 160 ‰ (14) (Fig. 3).

Fig. 3

Gas analyses of the black glass. Both bulk analyses and step
heating analyses plot on a single mixing line between terrestrial
atmospheric gas (at left) and Mars atmospheric gas (13), Zagami
data from (25).

Simultaneous measurement of carbon and nitrogen was carried out by stepped combustion-mass spectrometry on
a small chip (21 mg) from the same sample we used for oxygen isotopic analysis (5). The sample had a total
13 15
carbon abundance of 173 ppm and δ C of -26.6 ‰, and contained 12.7 ppm nitrogen with total δ N of -4.5 ‰. At
temperatures above 600°C, both carbon and nitrogen were distributed between 3 discrete Martian components
(fig. S11, table S12). Below 600°C, readily-resolvable components of organic material combusted; while these may
have been introduced during post-fall collection and sample storage, and are an unavoidable consequence of

2 de 5 11/10/2012 19:11


sample handling procedures, we cannot yet rule out the presence of small quantities of indigenous Martian organic
matter (5). At the highest temperatures of the extraction, there was a clear indication of the presence of trapped
13 15
Martian atmosphere, with elevated δ C and δ N (even allowing for a cosmogenic component, blank-corrected
13 15
δ C reaches +16 ‰ and δ N reaches +298 ± 25 ‰). At intermediate temperatures (600 – 800°C), there were
13 15
maxima in both δ C (-14 ‰) and δ N (+110 ‰), suggesting that the component bears some relationship to the
Martian atmosphere. In addition, there was clear analytical evidence for a simultaneous release of sulfur (~19
ppm), presumably from either sulphide or sulfate decomposition. This intermediate component probably
corresponds to a surface-derived weathering component, as identified in Tissint glass on the basis of REE, S and
F data (see below). The third Martian component represents magmatic carbon, which is present in low abundance
13 15
(1.4 ppm with δ C of -26.3 ‰) and is associated with isotopically-light nitrogen (δ N < +10 ‰).

Our study demonstrates that Tissint is a picritic shergottite comparable in many respects to EETA79001. The
black shock glass resembles lithology C of EETA79001, as well as shock melt pockets commonly found in other
shergottites (15). Major elements and oxygen isotope data indicate that this glass represents a melted mixture of
the surrounding bulk rock, composed of olivine, maskelynite and clinopyroxene (5). However, this glass is
substantially different from the bulk meteorite and igneous groundmass in that it has a variable, but generally high
15
S and F content; a distinct LREE-enriched composition; and a high δ N value indicative of trapped Martian
atmosphere.

The LREE-enriched composition of the glass is somewhat enigmatic. Phosphates are often invoked as a carrier of
REE. However, the P content of the black glass relative to bulk rock is not consistent with enrichment in
phosphates. One possibility to explain the LREE composition of the glass might be selective crustal contamination
prior to final emplacement of the Tissint magma. Although LREE-enriched magmatic rocks have been generated
on Mars, as exemplified by the Nakhlites and Chassignites, these do not exhibit anomalous Ce abundances (16,
17). In addition, crustal contamination of magma is unlikely to result in REE ratio variations at the sub-centimeter
4+
scale, as observed here. Decoupling of Ce from the other REE, indicates partial oxidation to Ce , a process that
requires oxidising conditions, such as those that prevail in the near-surface environment of Mars. Surface
weathering caused by leaching of phosphates by acid aqueous fluids, the process that is responsible for terrestrial
alteration of eucritic meteorites in Antarctica (18), would also explain the LREE-enriched composition of the Tissint
15
glass The high δ N value of the Tissint glass, as well as its enrichment in S and F, demonstrates that it has been
contaminated by Martian surface components. In view of this evidence, the most likely explanation for the relatively
LREE-enriched composition of the glass, and the origin of the Ce anomaly, is that these features also reflect the
presence of a near-surface Martian component in Tissint. A Martian soil component was previously suggested for
EETA79001 lithology C, which also contains Martian atmospheric gases (19). However, because this meteorite is a
find, rather than a fresh fall like Tissint, there’s the possibility of terrestrial contamination, which complicates the
interpretation (20).

We propose the following scenario in order to explain the composite nature of Tissint. A picritic basalt was
emplaced at or near the surface of Mars. After some period, the rock was weathered by fluids, which had leached
elements from the Martian regolith. Subsequently, these fluids deposited mineral phases within fissures and
cracks. The Martian weathering products are the most likely source of the required LREE, incompatible and
volatile elements. Upon impact, preferential, shock-induced melting occurred in the target rock along fractures
where weathering products were concentrated. This melting produced the black glass and retained in it chemical
signatures characteristic of the Martian surface. Shock melting also trapped a component derived from the Martian
atmosphere, as revealed by stepped combustion-mass spectrometry. About 0.7 Ma ago, the sample was ejected
from Mars and eventually landed on Earth in July 2011. The Martian weathering features in Tissint described here
are compatible with spacecraft observations on Mars, including those made by the NASA Viking landers, MER
Spirit rover and ESA’s Mars Express orbiter (5, 21–23).

Supplementary Materials
www.sciencemag.org/cgi/content/full/science.1224514/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S11
Tables S1 to S13
References (26–35)

Received for publication 9 May 2012.
Accepted for publication 25 September 2012.

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36. Acknowledgments: Authors acknowledge: Dean N. Menegas and family for their generous donation
enabling the acquisition of Tissint (BM.2012,M1), Mohamed Aoudjehane for fieldwork, Adam Aaranson for
field information, Jenny Gibson for her assistance with oxygen isotope analysis, Luc Labenne for providing
and loan of a sample, and Tony Irving for 400 mg powdered sample. This study was funded at Hassan II
University Casablanca, FSAC by CNRST, Morocco and CNRS France, PICS SDU 01/10, and CMIFMP
Volubilis (MA/11/252); CRPG, Nancy, France by the CNES, the CNRS, and the ERC under the ECSFP
(FP7/2007-2013 no. 267255); UBO-IUEM, Plouzané, France by the PNP, INSU; Open University, by STFC
grant to the Planetary and Space Sciences Discipline; and University of Alberta, by NSERC grant 261740-03.

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www.sciencemag.org/cgi/content/full/science.1224514/DC1

Supplementary Materials for
Tissint Martian Meteorite: A Fresh Look at the Interior, Surface, and
Atmosphere of Mars
H. Chennaoui Aoudjehane,* G. Avice, J.-A. Barrat, O. Boudouma, G. Chen, M. J. M.
Duke, I. A. Franchi, J. Gattacecca, M. M Grady, R. C. Greenwood, C. D. K. Herd, R.
Hewins, A. Jambon, B. Marty, P. Rochette, C. L Smith, V. Sautter, A. Verchovsky, P.
Weber, B. Zanda

*To whom correspondence should be addressed. E-mail: chennaoui_h@yahoo.fr, h.chennaoui@fsac.ac.ma

Published 11 October 2012 on Science Express
DOI: 10.1126/science.1224514

This PDF file includes:

Materials and Methods
Supplementary Text
Figs. S1 to S11
Tables S1 to S13
References (26–35)

1. Materials and Methods

Oxygen isotope analysis was carried out at the Open University using an infrared laser-

assisted fluorination system (7). Whole-rock chips of Tissint, with a total mass of approximately

100 mg, were powdered and homogenized and from this ~2 mg of powder was loaded for each

replicate analysis. In addition, fragments of black shock glass were hand picked under a

binocular microscope and then loaded without further treatment. Oxygen was liberated from the

sample by laser-heating in the presence of BrF5. After fluorination the O2 released was purified

by passing it through two cryogenic nitrogen traps and over a bed of heated KBr. O2 was

analyzed using a MAT 253 dual-inlet mass spectrometer. Analytical precision (2σ), based on

replicate analysis of international (NBS-28 quartz, UWG-2 garnet) and internal standards, is

approximately ±0.08‰ for δ17O; ±0.16‰ for δ18O; ±0.05‰ for Δ17O (7). The quoted precision

(2σ) for Tissint is based on the results obtained on replicate analyses.

Results for the oxygen isotope analysis of Tissint are reported in standard δ notation,

where δ18O has been calculated as: δ18O = [(18O /16Osample)/(18O /16Oref)-1] × 1000 (‰) and

similarly for δ17O using the 17
O /16O ratio. Δ17O, which represents the deviation from the

terrestrial fractionation line, has been calculated as: Δ17O = δ17O – 0.52 δ18O (Fig. S9).

Measurements of short-lived cosmogenic nuclides by gamma-ray spectroscopy were

performed in La Chaux de Fonds (La Vue-des-Alpes underground laboratory) (26) and the

University of Alberta on 29 g and 58 g specimens, respectively.

The Germanium detector in the "la Vue-des-Alpes Underground Laboratory" is shielded

from:

- The cosmic exposure, thank to the 600 meters water-equivalent above the detector; the

neutron flux is thus reduced by a factor 10'000.

- The natural radioactivity of the rock in the laboratory; the germanium detector is

shielded with 30 cm of ultralow radioactivity Cu and 30 cm of ultraslow radioactivity Pb.

- The radon contained in the air; nitrogen is flushed into the detection volume, in order to

replace the air and avoid a radon counting into the detector.

The gamma analysis starts when nitrogen completely replaced the air. These shielding

methods allow gamma counting of samples with a very low background:

- The detector background at 320.1keV (51Cr peak) is 0.24+/-0.43 counts/day

- The detector background at 983.5keV (48V peak) is 0.19+/-0.16 counts/day

Moreover, in order to get quantitative activity values of the measured cosmogenic

isotopes, a Monte-Carlo simulation, based on the GEANT3 code from CERN, is run.

This simulation takes into account the sample's chemical composition, density, and its geometry

(self-absorption). The detector efficiency of measuring a gamma from the sample is then

calculated for each peak energies.

Unlike gamma-ray spectrometer systems specifically designed to measure cosmogenic

radionuclides in meteorites (27-28) the University of Alberta SLOWPOKE Reactor Facility

gamma-ray spectrometer utilized to measure the cosmogenic radionuclides of the Tissint

meteorite sample is typically used for measuring naturally occurring radionuclides in terrestrial
54 22 26
samples. Consequently, determining the cosmogenic radionuclides Mn, Na, and Al in the

Tissint meteorite, with acceptable statistical uncertainties, required counting the sample for an

extended period (1,250,000 s, i.e., 14.4676 d). The University of Alberta γ-ray spectroscopy

system utilized consists of a 41% efficient ORTEC FX Profile hyperpure Ge detector, with
210
carbon end-window, housed in a 15 cm Pb cave (the inner 5 cm consisting of ‘old’, Pb-poor,

lead) with a Cu lining. The detector is attached to an ORTEC DSPEC Pro digital spectrometer.

The system was efficiency calibrated using a variety of certified naturally occurring radioactive

standards, corrected for natural background. Fortuitously, the Tissint sample analyzed was

similar in both shape and mass to the standards used for efficiency calibration. Consequently, no

corrections were applied for differing counting geometries, or possible gamma-ray self-

attenuation effects.

Natural long-lived radiogenic elements (238U, 232
Th and 40
K and their decay products)

were observed in addition to 26Al and 22Na, and up to four other short-lived cosmogenic isotopes

(Table S10). These data however cannot be directly compared to those from Martian meteorites

because there are no measurements of short-lived cosmogenic isotopes for other Martian

meteorites. The average 22Na/26Al ratio at the time of fall for the two determinations is 2.05 (±

0.17). Differences in the specific activities of the cosmogenic radionuclides may be due to the

pre-break-up size of the meteorite and location of the analyzed samples in the original meteorite.

The consistency of the ratio of the University of Alberta/La Chaux de Fond 26Al, 22Na, and 54Mn

determinations (1.7 ± 0.1) supports this explanation.

Electron Microprobe Analysis (EMPA): All major and minor mineral phases have been

analyzed by EMPA with a Cameca SX100 electron microprobe in Paris according to the

procedures presented in (29) and are reported in Tables S1-6. In particular the FeO/MnO of

pyroxene (30±5) and olivine (50±12) despite significant variability correlate with their Mg# and

are characteristic of a Martian composition. The detection limits for F and Cl are 200 and 100

ppm respectively. Furthermore, P, F, Cl and S were analysed in the black glass. We report in

Table S7 the average composition obtained for 150 data points and range. The detection limits

for these elements are 100, 200, 100 and 100 ppm respectively. No correlation between F and Fe

is observed as would be the case if Fe-L line and F-K line were not properly resolved.

SEM: images on several polished sections were made at the NHM in London using a

Zeiss EVO 15LS SEM and in Paris using Zeiss ULTRA 55VP (Fig. S4-S5-S7). Chemical

mapping was performed in London using an EDX spectrometer (Oxford Instruments INCA

system).

Bulk Elemental Composition:

Analyses were obtained by ICP-MS at University of Alberta on a 400 mg subsample of a

1.25 g homogenized interior sample according to the procedure described in (30), by ICP-AES

and ICP-SFMS at UBO in Brest following the procedure described in (24). Finally, a 5 mg of

black glass was analyzed by ICP-AES and ICP-MS at CRPG in Nancy, following the procedure

described in (31). All these procedures are well established, and the same geostandards (e.g.,

BIR-1 and BHVO-2) were used during the sessions in order to avoid any systematic bias

between the three laboratories. Based on replicate standards, the 1-σ analytical uncertainties for

abundances are better than 5 % for all the elements. Trace element ratios are often determined

with a much better accuracy. In the case of the Ce/Ce* (where Ce* is the expected Ce

concentration for a smooth CI-normalized REE pattern, such that Ce*n=(Lan x Prn)1/2), the 1σ

analytical uncertainties are about 1 % or better, even at low REE abundances, as exemplified by

the USNM3529 Allende standard (see Table 4 in ref. 24).

For N-noble gas analysis, mg-sized aliquots were loaded in a laser chamber, outgassed under

vacuum at 100 °C overnight, and then left under high vacuum for several days to decrease the

background. Each sample was heated with a continuous mode infrared CO2 laser (10.6 nm

wavelength) for 5 min in static vacuum. Modulating the power of the laser permitted to apply 2

temperature steps (~800°C and fusion). The evolved gas was split into two fractions, one for

nitrogen isotope analysis and one for noble gas analysis, and sequentially analyzed with a static

mass spectrometer (see (32) for further details).

Carbon and nitrogen analyses were carried out at the Open University. They were extracted by

CO2 laser step-heating of mg sized samples, and analysed using the FINESSE isotope ratio mass

spectrometer (33). A small chip of 21 mg was wrapped in platinum foil, then heated under excess

oxygen in increments from room temperature to 1400°C. System blanks were < 4 ng carbon and

< 1 ng nitrogen per increment for temperatures below 600°C, and < 10 ng carbon and < 2 ng

nitrogen per increment for temperatures above 600°C. Data are shown in Figure S11 and

summarized in Table S12.

2- Supplementary text

Field evidence

At about 2 am local time on July 18, 2011, a bright fireball was observed in the region of

the Oued Drâa valley, SE of Tata, Morocco.

One eyewitness reported that it illuminated the entire area, before splitting into two parts.

Two sonic booms were also reported. In October 2011, after a thorough search, nomads began to

find fresh, fusion-crusted stones in a remote area, centred about 50 km ESE of Tata and 48 km

SSW of Tissint, both N and S of the Oued El Gsaïb valley and near El Ga’ïdat plateau. The

weather in this desert area is very dry, especially in summer, when rain is exceptionally rare. It

wasn’t until December 2011 that the Martian origin of the fall was realised. The first pieces were

collected at the end of October and sold in Erfoud. A few pieces weighing between 2 kg and 0.1

kg have been recovered, but the largest number consists in thousands of smaller pieces, crusted

or splintered from larger stones. The total meteorite mass recovered, as of the end of February

2012, is estimated at about 17 kg (Fig. S1-S2). A number of large specimens are now preserved

in national or public institutions (Table S13).

Mineralogy and Petrography:

When broken open, the crust reveals a pale grey interior, with pale yellow olivine

macrocrysts (up to 2 mm across) and microphenocrysts, which comprise up about 16 vol. % of

the rock. The finer groundmass is composed of light grey pyroxene (about 50 vol%) and darker,

mostly, but not totally amorphized plagioclase (maskelynite) 18±2 vol % (Fig. 1, Fig. S3-S5).

All olivines are of the same composition with no difference between large and small crystals;

they exhibit thin ferroan rims against groundmass and contain small chromite inclusions. Narrow

ferroan zones also occur within the interior of some olivine along fractures. Olivine macrocrysts

(FeO/MnO=42-44) are zoned from the core (Fa16-20) to the rim (Fa43-60, FeO/MnO=50-55) where

it reaches a Fa value similar to olivine interstitial microcrysts, (cores Fa29-30, FeO/MnO=45-46;

rims up to Fa53, FeO/MnO=53), (Fig. S3-S6). Augite/pigeonite exhibits patchy zoning as is

observed in e.g. QUE 94201 with orthopyroxene cores (Fs24-24Wo4-5, FeO/MnO=30-32),

pigeonite (Fs26 -52Wo12-17, FeO/MnO=31-35) and sub-calcic augite (Fs22-23Wo25-24,

FeO/MnO=26-28), rims (Fig. S4-S6). Plagioclase (maskelynite, An61-64Or0.5-0.4) is slightly zoned

but does not include silica or mixed silica rich glass, it shows a relict of twin lamella (Fig.

S5)(34).

Minor phases are Ti-poor chromite, ilmenite, titanomagnetite (modal abundance of oxides

is less than 1%), pyrrhotite, apatite and merrillite.

Physical properties:

Grain density of 3.41±0.03, measured on a 28 g sample, exceeds that measured in other

shergottite falls (3.28; (35)) in agreement with a more mafic composition of Tissint compared

with other shergottites. Magnetic properties, measured on 29 samples from different stones of

various origins, exhibit particularly low variability. They are in agreement with data obtained on

other shergottites whose magnetization is carried by pyrrhotite (6), although it appears that a

significant fraction of magnetization is carried by Fe rich oxides (Fig. S8). Natural remanence

measurement of a number of uncrusted fragments reveals that the majority have been tested with

a magnet. Extra-terrestrial field estimate from remaining fragments is lower than previous data

from shergottite falls.

Geochemistry

The composition of the black glass was estimated using two approaches: wet chemical

analysis of the aliquot of glass used for gas analysis and taking the average composition from

two sets of EMPA data from 150 and 127 individual spots. Data from the wet chemical analysis

and from one of the EPMA data sets are reported in Table S7. An indication of sample variability

is given by the range of composition in Table S7. Several points relevant to the origin of the

Tissint black glass merit further discussion here. The agreement between the two methods is

fair, especially when the compositional variability is considered. The major element composition

is equivalent to a mixture of approximately 30% olivine, 50% pyroxene and 20% maskelynite

and the variability is explained by imperfect mixing/melting of the major phases (Fig. S7).

Among the minor elements, F, P, S and Cl are of particular significance. Fluorine is estimated

from EMPA analyses as having an average value of 720 ppm, with 45% of the data below the

detection limit of EMPA (200 ppm). Modal mineralogy of the rock indicates 0.5 % merrillite

corresponding to about 0.25 % P2O5, which is in the same range as that measured in the black

glass (0.5-0.25 %) using both bulk chemical analysis and EMPA. Modal mineralogy also

suggests the presence of <0.1% troilite, whereas the amount of S measured by EMPA

corresponds to an equivalent of 0.7 % FeS. A similar observation was made by Rao et al. (19) in

EETA79001. Chlorine has a low abundance (<200 ppm), and 97% of the results are below the

EPMA detection limit for Cl. Chlorine is essentially absent. Rao et al. (19) noticed a similarly

low level of Cl in EETA79001 lithology C, despite the presence of excess S. P is present at

levels expected from bulk rock melting. This point is important, as phosphate is a potential

carrier phase of REE. The overabundance of S compared with that contained in the bulk rock and

its strong variability suggests that it was contributed by a sulphide which volatilised during shock

melting and which is now present in the shock-melted, glass veins and pockets. Fluorine is also

clearly overabundant compared to the bulk rock value. The only common phase of the

groundmass, which could carry F, is merrillite. Its measured F abundance however is always

below the detection limit of EMPA (Table S4). We must, therefore, conclude that the black glass

veins and pockets contain an S and F-rich component which is absent from the groundmass and

which is irregularly distributed in the veins and pockets.

Oxygen isotope analysis results for both bulk Tissint and black shock glass are given in

Table S9 and plotted in Fig. S9. The results are shown in Fig. S9 in relation to the Mars

Fractionation Line (7) and other published Martian meteorite oxygen isotope analyses obtained

by laser fluorination. The analysis of bulk Tissint in Fig. S9 plots close to the Mars Fractionation

Line (MFL) and within the broad field occupied by other shergottitic meteorites, thus confirming

that it is a member of the Martian meteorite group. Also shown in Fig. S9 is the mean analysis of

black shock glass in Tissint. This has a similar δ18O value to the bulk meteorite, but displays a

significantly greater level of heterogeneity with respect to Δ17O, with a 2σ value of ± 0.090 ‰

compared to ± 0.002 ‰ for the bulk meteorite.

The stepped combustion profiles (Fig. S11) indicate that both carbon and nitrogen are

distributed between several discrete components (Table S12). The data are interpreted in the

following way: below 600°C, the abundance histograms clearly show that there are two separate

components, the first of which combusts between 200-400°C, with δ13C ~ -28‰, δ15N ~ -10‰

and a variable C/N of between ~10-30. The second component has a slightly higher δ13C, at ~ -

26‰, but similar δ15N ~ -10‰ and variable C/N of ~10-30. Almost all of the carbon and

nitrogen released below 600 °C is believed to emanate from combustion of organic material

mixed with release of adsorbed terrestrial atmosphere. Although the carbon isotopic composition

of the components is compatible with interpretation of its having a terrestrial origin, this by itself

is insufficient to rule out the presence of small quantities of indigenous Martian organic matter.

Three additional components of presumed Martian origin were identified as combusting (or

being released) at temperatures above 600 °C; they are described in the main text.

Based on the production rate of cosmogenic 15N (see “cosmogenic isotopes” section) the

contribution of the component, if it is all released at 1100oC, is about 60‰.

The amount of sulphur released between 650 and 800oC is calculated based on the total

pressure of CO2+SO2 measured by baratron and the amount of CO2 measured as mass 44 peak

intensity in the mass spectrometer.

Tissint results compared to spacecraft remote-sensing data

Evidence described in this paper for a Martian weathering component in Tissint is consistent

with observations made by both orbital spacecraft and landers on Mars. The fact that S is a major

component in the Martian soil was first demonstrated by the NASA Viking landers (21). The

NASA Spirit MER rover undertook a detailed compositional analysis of rocks and soils at Gusev

crater (22). These showed clear evidence for the interaction of water and volcanic rocks at

Gusev, with anomalously high concentrations of sulphur, chlorine and bromine. In addition,

multilayer coatings on the surface of rocks at Gusev have high ferric (Fe3+) ion enrichments

consistent with a highly oxidizing environment. This latter feature is clearly relevant to the

evidence presented in our paper for partial oxidation of Ce to Ce4+ under oxidising conditions,

which prevail at the surface of Mars. A range of hydrated sulphate minerals have been detected

on Mars by the OMEGA hyperspectral imager on ESA’s Mars Express orbiter (23). In the case

of Tissint, sulphur is found to be in excess in the black glass relative to the groundmass. The

same is true for fluorine. High levels of halogens have been detected in the Martian soil (bromine

and chlorine), but as yet evidence for high levels of fluorine is not as strong. Chlorine, which is

present in the soil is not found at a significant level in the black glass. Our conclusion is

therefore that contamination is not from soil incorporation, which would concern all elements (S

and Cl) but rather contamination by infiltration. On this point it is interesting to note that the

Spirit MER rover data indicates: “decoupling of sulphur, chlorine and bromine concentrations in

trench soils compared to Gusev surface soils, indicating chemical mobility and separation.”

(22).

Discussion: Tissint is an olivine-phyric shergottite; the olivine macrocrysts are likely to have

been accumulated into a more evolved liquid. Nevertheless, it seems clear that Tissint has

affinities to the depleted mantle source on Mars, based on its REE composition. It is possibly

related (and possibly launched paired) with EETA79001, which displays the same Lu/Hf ratio.

The numerous patches and veins of black glass are the result of shock melting.

Fig. S4: BSE image. Notice the fractured olivine macrocryst invaded by the groundmass and its zoning.
Maskelynite is dark grey, oxides and sulfides apear white. The variable grey otherwise corresponds
mostly to patchy zoning of pyroxene; small olivines are slightly normally zoned are light grey.

Wo
0.5

0.4

0.3

0.2

0.1

0.0
En 0 0.2 0.4 0.6 0.8 1 Fs
EETA79001

Fo Fa
0 0.2 0.4 0.6 0.8 1

Fig. S6. Composition of pyroxene and olivine in Tissint compared to those in
the shergottite EETA79001.

Fig. S7: BSE image of a black glass pocket, fractured and containing bubbles. The glass
shows significant compositional heterogeneity due to variable melting of olivine, pyroxene
and plagioclase.

Fig. S8: Tissint Data: Magnetic susceptibility is 1.27±0.2 10-6m3/kg and saturation remanence
62±8 mAm2/kg. logMrs in mAm2/kg versus logc in 10-9 m3/kg for pyrrhotite and magnetite
dominant shergottites, circles and triangles, highlighting Tissint in red and falls in bold.

Fig. S9. Oxygen isotope analyses for Tissint and shock glass in Tissint shown in relation to
other published laser fluorination analyses of SNC meteorites. Error bars for bulk Tissint and
Tissint shock glass are 2σ. MFL: Mars Fractionation Line (5). TFL: Terrestrial Fractionation
Line.

10
EETA
79001A
sample / chondrite

Tissint (W.R.)
1 1.25 g sample
0.492 g sample
SaU 005
DaG 476

Zagami

10

Tissint
W.R.
1
black glass
"groundmass"

Y Zr Ba U La Pr Eu Tb Ho Tm Lu
Hf Nb Th Ce Nd Sm Gd Dy Er Yb
Fig. S10. Trace element pattern: Top: Whole-rock trace element systematics of Tissint in comparison
with other depleted picritic (olivine-bearing) shergottites. Bottom: Black glass and groundmass-rich
fraction in comparison with Tissint whole rock and Zagami. Notice the Ce anomaly in the black glass
and groundmass which is not observed in Zagami. Data from (7-9). CI chondrite normalization
values are from (18).

Fig. S 11: Stepped combustion data acquired from a 21 mg chip of Tissint (from the Natural
History Museum, London, specimen). (a) carbon; (b) nitrogen and (c) atomic C/N ratio. In (a)
and (b), the histograms are the amount of material released, normalised to the width of the
temperature step, whilst the line profiles are isotopic composition. Errors in isotopic composition
are less than the size of the symbol unless shown otherwise.

4. Supplementary Tables

Table S1: Representative analyses of pyroxene. Structural formula based on 4 cations and 6
oxygens.

Pigeonite

Augite

86/20
86/174
85/17
82/98
85/130

SiO2
54.04
48.60

52.67
49.89
52.02

Al2O3
0.56
0.69

0.82
0.90
1.98

MgO
24.41
12.51

18.26
9.94
14.59

FeO
16.27
29.15

15.64
21.36
11.93

MnO
0.56
0.85

0.48
0.60
0.42

CaO
2.89
5.71

9.77
14.13
16.75

Na2O
0.07
0.06

0.09
0.17
0.13

K2O
0.00
0.01

0.00
0.03
0.01

TiO2
0.07
0.70

0.16
1.18
0.35

Cr2O3
0.47
0.15

0.50
0.13
0.98

NiO
0.00
0.00

0.00
0.00
0.09

Total
99.35
98.43

98.38
98.34
99.24

Mg#
0.73
0.43

0.68
0.45
0.69

FeO/MnO
28.84
34.29

32.58
35.49
28.27

Si
1.99
1.94

2.00
1.98
1.97

Al
0.02
0.03

0.04
0.04
0.09

Mg
1.34
0.75

1.03
0.59
0.82

Fe
0.50
0.97

0.50
0.71
0.38

Mn
0.02
0.03

0.02
0.02
0.01

Ca
0.11
0.25

0.40
0.60
0.68

Ti
0.00
0.02

0.00
0.04
0.01

Cr
0.01
0.00

0.01
0.00
0.03

En
0.66
0.37

0.52
0.30
0.41

Fs
0.25
0.46

0.27
0.39
0.22

Wo
0.05
0.10

0.19
0.30
0.31

Table S2: Representative analyses of olivine. Structural formula based on 3 cations.

rim
rim
core
core

85/351
89 / 93
89 / 41
37 / 1

SiO2
33.45
35.12
38.31
38.98

Al2O3
0.03
0.01
0.03
0.07

MgO
16.18
23.67
36.47
41.16

FeO
49.53
40.38
25.09
19.02

MnO
0.81
0.69
0.55
0.29

CaO
0.35
0.33
0.26
0.21

Na2O
0.05
0.02
0.01
0.01

K2O
0.00
0.00
0.00
0.00

TiO2
0.05
0.00
0.00
0.00

Cr2O3
0.03
0.05
0.25
0.21

NiO
0.00
0.01
0.19
0.14

Total
100.48
100.27
101.16
100.09

Mg#
0.37
0.51
0.72
0.79

FeO/MnO
61.1
58.5
45.9
65.4

Si 1.00
1.00
1.00
1.00

Mg 0.72
1.01
1.42
1.57

Fe 1.24
0.96
0.55
0.41

Mn 0.02
0.02
0.01
0.01

Ca 0.01
0.01
0.01
0.01

Cr 0.00
0.00
0.01
0.00

Table S3: Representative compositions of maskelynite

Maskelynite
60 / 1 84 / 3
SiO2 51.83 56.78
Al2O3 30.39 26.42
MgO 0.13 0.05
FeO 0.65 0.68
MnO 0.04 0.02
CaO 13.66 9.90
Na2O 3.42 5.13
K 2O 0.04 0.50
TiO2 0.04 0.08
Cr2O3 0.01 0.00
NiO 0.00 0.00
Total 100.21 99.55
Si 2.36 2.58
Al 1.63 1.42
Ca 0.67 0.48
Na 0.30 0.45
K 0.00 0.03

Table S4: Representative analyses of merrillite

18 / 1 14 / 1 6/1
SiO2 0.21 0.17 0.39
Al2O3 0.04 0.03 0.24
MgO 1.94 2.69 3.07
FeO 3.99 2.96 2.05
MnO 0.20 0.14 0.08
CaO 46.00 46.57 46.55
Na2O 0.80 0.92 0.98
TiO2 0.04 0.11 0.13
Cr2O3 0.02 0.01 0.05
P 2O 5 46.19 46.04 45.45
SO2 0.01 0.54 0.01
Cl 0.00 0.00 0.02
F 0.00 0.00 0.00
Total 99.43 100.19 99.02

Table S5: Representative analyses of sulphides

8 =7 19 / 1 13 / 1 23 / 1
Weight %
S 38.43 37.22 37.65 38.35
Fe 58.00 55.54 54.80 52.55
Co 0.04 0.08 0.10 0.12
Ni 1.38 2.81 4.53 6.02
Cu 0.06 0.15 0.03 0.00
Zn 0.05 0.07 0.00 0.06
Total 97.96 95.86 97.11 97.11
mol%
S 52.97 52.58 52.54 53.33
Fe 45.89 45.04 43.91 41.96
Co 0.03 0.06 0.08 0.09
Ni 1.04 2.16 3.45 4.57
Cu 0.04 0.11 0.02 0.00
Zn 0.03 0.05 0.00 0.04
100.00 100.00 100.00 99.99

Table S6: Representative analyses of oxides. Structural formula based on 3 cations and 4
oxygens.

70 / 1 78 / 1 76 / 1 41 / 1 74 / 1 51 / 1 49 / 1 54 / 1 43 / 1 83 / 1
SiO2 0.17 0.22 0.15 0.29 0.04 0.02 0.03 0.05 0.06 0.08
Al2O3 7.22 7.29 7.13 8.46 5.61 5.59 4.51 3.60 2.57 1.31
MgO 3.59 5.11 4.72 3.43 1.48 2.14 2.19 1.78 1.17 0.37
MnO 0.00 0.00 0.00 0.02 0.21 0.23 0.35 0.47 0.65 0.57
FeO 29.04 27.06 27.46 29.37 43.02 45.34 46.71 51.89 54.03 63.04
CaO 0.00 0.00 0.03 0.09 0.04 0.07 0.10 0.05 0.06 0.16
TiO2 0.75 0.73 0.72 1.28 10.67 11.86 19.29 20.85 24.64 31.20
Cr2O3 58.16 59.37 59.75 53.30 38.90 32.28 24.99 20.48 13.97 0.36
Total 98.93 99.79 99.95 96.24 99.98 97.53 98.17 99.16 97.15 97.09

Si 0.006 0.008 0.006 0.010 0.001 0.001 0.001 0.002 0.002 0.003
Ti 0.020 0.019 0.019 0.035 0.287 0.325 0.528 0.569 0.693 0.888
Al 0.301 0.298 0.291 0.360 0.237 0.240 0.194 0.154 0.113 0.058
Cr 1.625 1.627 1.641 1.520 1.101 0.929 0.720 0.587 0.413 0.010
Fe 0.858 0.784 0.797 0.886 1.288 1.380 1.423 1.575 1.690 1.995
3+
Fe 0.022 0.022 0.019 0.029 0.085 0.180 0.027 0.117 0.083 0.149
2+
Fe 0.836 0.762 0.778 0.857 1.202 1.200 1.396 1.458 1.607 1.846
Mg 0.189 0.264 0.245 0.184 0.079 0.116 0.119 0.096 0.065 0.021
Ca 0.000 0.000 0.001 0.003 0.001 0.003 0.004 0.002 0.003 0.006

Mg# 18.46 25.74 23.91 17.71 6.14 8.82 7.84 6.21 3.91 1.11
Spin 15.22 14.92 14.58 18.68 11.83 12.29 9.86 7.77 5.84 3.00
Chrom 82.15 81.53 82.08 78.98 55.04 47.62 36.66 29.60 21.27 0.54
Usp 1.98 1.89 1.89 3.63 28.74 33.30 53.82 57.39 71.33 91.48
Mgt 1.09 1.10 0.94 1.52 4.27 9.25 1.39 5.88 4.28 7.70

Table S7: Major element composition

Bulk Rock Groundmass Black Glass
Alberta UBO UBO CRPG EMPA range
Mass 1250 mg 492 mg 181 mg 5 mg n=150 n=150
SiO2 44.86 45.74 35-55
TiO2 0.63 0.65 0.67 0.56 0.36 0-1.5
Al2O3 4.86 5.50 6.37 4.09 3.58 0-18
FeO 21.15 20.87 18.80 21.84 20.24 9-26
MnO 0.52 0.53 0.49 0.51 0.53 0.3-0.7
MgO 17.06 17.92 15.09 19.99 20.91 10-35
CaO 6.53 7.31 7.16 6.03 5.68 0.3-14
Na2O 0.72 0.77 1.13 0.63 0.46 0-2.2
K 2O 0.02 0.02 0.09 0.04 0.02 0-0.2
P 2O 5 0.48 0.56 0.44 0.46 0.24 0-5
Cr2O3 0.41 0.78 0.70 0.81 0.71 0.2-1.5
NiO 0.03 0.02 0.02 0.03 0.05 0-0.2
S 0.27 0-1
F 0.07 0-0.4
Cl 0.00 0-0.03
Total 99.85 98.80 98-101
Mg# 0.59 0.60 0.59 0.62 0.65 0.56-0.71
FeO/MnO 41 39 38 42 38 28-44

Table S8: Chemical analyses, trace elements. All in ppm.

Bulk Rock Groundmass Black Glass
Alberta UBO UBO CRPG
Mass 1.25 g 0.492 g 0.181 g 0.005 g
ppm
Li 2.18 2.00 4.60
Be 0.031 0.097
P 2074 2285 1906
K 200 235 771
Sc 39.38 36.49 38.3
Ti 3789 4044 3732
V 194 219 205 200
Cr 3042 5323 4756 5549
Co 58.1 58.5 47.7 63.2
Ni 269 262 199 268
Cu 13.8 9.80 9.94 23
Zn 63.0 63.2 55.0 87.3
Ga 12.05 11.32 11.25 9.29
Rb 0.376 0.305 2.52 1.36
Sr 34.78 31.79 43.40 25.07
Y 14.91 13.22 12.82 8.21
Zr 23.14 19.69 24.73 20.1
Nb 0.28 0.219 0.771 0.226
Cs 0.0153 0.0710 0.184
Ba 3.54 2.50 36.57 5.91
La 0.315 0.283 2.62 1.20
Ce 1.16 0.945 6.19 2.81
Pr 0.237 0.192 0.745 0.324
Nd 1.63 1.37 3.37 1.58
Sm 1.07 0.877 1.13 0.673
Eu 0.503 0.405 0.452 0.271
Gd 1.85 1.70 1.79 1.05
Tb 0.364 0.333 0.331 0.196
Dy 2.38 2.22 2.17 1.24
Ho 0.504 0.466 0.453 0.266
Er 1.48 1.30 1.24 0.764
Tm 0.204
Yb 1.30 1.17 1.10 0.772
Lu 0.190 0.160 0.15 0.11
Hf 1.01 0.81 0.96 0.67
Ta 0.0138 0.0533
W 0.041 0.094
Pb 0.25 0.15 0.74
U 0.0070 0.100 0.123
Th 0.0240 0.915 0.323

Table S9: Oxygen isotope results
17 18 17
SAMPLE δ O‰ 1σ δ O‰ 1σ Δ O‰ 1σ

Bulk BM 1 2.69 4.58 0.30
Bulk BM 2 2.61 4.43 0.30
Bulk BM 3 2.49 4.22 0.30

Mean BM 2.60 0.10 4.41 0.18 0.30 0.00

black glass 1 2.54 4.37 0.26
black glass 2 2.52 4.21 0.33
black glass 3 2.51 4.29 0.28
black glass 4 2.62 4.45 0.30
black glass 5 2.47 4.18 0.29
black glass 6 2.51 4.28 0.29
black glass 7 2.54 4.35 0.28

Mean Black
Glass 2.53 0.05 4.31 0.10 0.29 0.02

Table S10: Radiogenic isotopes at the time of fall.

La Chaux de Fonds Univ. of Alberta
Isotope T(1/2) dpm/kg ± 1σ dpm/kg ± 1σ
238U 2.24 0.80
232Th 2.10 0.45
40K 262 19 391 99

26Al 0.717 My 23.9 2.2 38.6 4.2
22Na 2.60 y 46.1 2.7 83.9 4.6

51Cr 27.7 d 161 62
7Be 53.3 d 192 60
54Mn 312.2 d 47.0 2.7 77.1 4.4
48V 16.0 d 5460 2030

Table S11: Nitrogen abundance and isotopic composition in groundmass and black glass.
Cosmogenic ages in Ma according to (2).

δ15NAIR,
14 3 21 38
Sample N ppm ‰ T( Hec) T( Nec) T( Arc)
± ± ± ± ±
Groundmass #1
(5.252 mg)
≈800 °C 0.181 0.005 9 16
≈1000 °C 0.059 0.002 4 28
Total 0.241 0.005 7 22 1.07 0.10 0.57 0.03 0.61 0.02
Groundmass #2
(6.262 mg)
≈800 °C 0.322 0.009 10 6
≈1000 °C 0.164 0.005 27 11
Total 0.486 0.010 19 5 1.30 0.13 0.54 0.03 0.88 0.02
Black Glass
(3.845 mg)
≈800 °C 0.042 0.002 -53 49
≈1000 °C 0.135 0.004 133 15
Total 0.176 0.004 100 13 1.31 0.13 0.72 0.04 1.17 0.03

Table S12. Approximate compositions of carbon- and nitrogen-bearing components in
Tissint identified by stepped combustion

Component Temp. [C] δ 13C [N] δ 15N C/N
(° C) (ppm) (‰) (ppm) (‰) (atom)
1. Organic 200-400 73 -28.7 5.5 -8.7 15
2. Organic 400-600 95 -25.8 6.7 -5.6 16
3. Intermediate 600 - 800 2.3 > -17 0.1 +63 25
(soil?)
4. Magmatic 800 - 1000 1.4 -26.3 0.2 < +10 12
5. Martian > 1000 < 1.2 < +16 < 0.04 < +300 40
atmosphere

Table S13. Specimens list in national institutions as of July 2012.

Institution
Mass (g)

NHM London, UK
1099 + 79 + 25

NHM Wien, Austria
990

ASU Carleton B. Moore Meteorite collection
USA
370

Smithsonian Institution, Washington DC, USA
159.46

University of New Mexico, Albuquerque, USA
108

University of Alberta, Edmonton, Canada
58

University of Washington, USA
30.3

Centre culturel AGM, Marrakesh, Morocco
23

Université P. et M. Curie, Paris, France
3.5

University of Tokyo, Japan
1.26

MNHN Paris, France
1.28

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