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Sciencewww.sciencemag.org.ez1.periodicos.capes.gov.brPublished Online October 11 2012

Science DOI: 10.1126/science.1224514

REPORT

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

H. Chennaoui Aoudjehane1,2,*, G. Avice3, J.-A. Barrat4, O. Boudouma2, G. Chen5, M. J .M. Duke6, I. A. Franchi7,

J. Gattacecca8, M. M. Grady7,9, R. C. Greenwood7, C. D. K. Herd5, R. Hewins10, A. Jambon2, B. Marty4,

P. Rochette8, C. L Smith9,11,12, V. Sautter10, A. Verchovsky7, P. Weber13, B. Zanda10

Author Affiliations

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

ABSTRACT

Tissint (Morocco) is the fifth Martian meteorite collected after it was witnessed falling to Earth. Ourintegrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottitesimilar to EETA79001A. Highly magnesian olivine and abundant glass containing Martian atmosphere arepresent in Tissint. Refractory trace element, S and F data for the matrix and glass veins in the meteoriteindicate the presence of a Martian surface component. Thus, the influence of in situ Martian weathering canbe unambiguously distinguished from terrestrial contamination in this meteorite. Martian weatheringfeatures in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmicray 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 abreakthrough in attempts to understand the geological evolution of Mars (1–3). Unfortunately, most of the sampleswere collected long after their arrival on Earth and thus have experienced variable degrees of terrestrialweathering (4). Even the few Martian meteorites that were collected shortly after their observed fall to Earth havebeen exposed to organic and other potential contaminants during storage. Here we report on the Tissint Martianmeteorite, which fell on 18th July 2011 in Morocco (figs. S1 and S2). This is only the fifth witnessed fall of ameteorite from Mars and therefore provides an opportunity to improve our understanding of processes thatoperated 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 feldspathicglass (maskelynite) (5) (figs. S3 to S6, tables S1 to S6). The matrix is highly fractured and penetrated by numerousdark shock veins and patches filled with black glassy material enclosing bubbles (fig. S7). The petrology of Tissintshows similarities to other picritic shergottites (an important group of olivine-rich Martian basaltic rocks), inparticular, 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 blackglass pockets and veins, are characteristics of this shergottite.The scale is in cm.

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Tissint is an Al-poor ferroan basaltic rock, rich in MgO and other compatible elements (Ni, Cr, Co). Its majorelement abundances are similar to those of the other picritic shergottites, especially EETA79001. Furthermore, keyelement ratios (wt%/wt%) such as FeO/MnO (39.7), Al/Ti (7.2), Na/Ti (1.41), Ga/Al (3.9 10−3), Na/Al (0.20) (3, 4,14) and Δ17O (+0.301‰) (fig. S9) (7) are also typical of Martian meteorites. The average composition of the blackglass (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). Amongminor elements in the black glass, chlorine is always below the detection level of EMPA (100 ppm), whereasfluorine 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 therange of values measured for EETA79001 and other basaltic shergottites (0.1 to 0.2, e.g., (8)), and lower thanthose of the picritic shergottites DaG 476/489, SaU 005 and Dhofar 019 (about 0.3, (9-11)). Although the sizes ofthe two samples analyzed here are somewhat limited (0.49 g and 1.25 g), their trace element abundances are verysimilar and so are likely to be representative of the whole rock composition, despite the irregular distribution ofolivine megacrysts.

Fig. 2

REE patterns: Top: Tissint in comparison with other depletedpicritic shergottites. Bottom: Black glass and groundmass-richfraction in comparison with enriched shergottite Zagami. Datafrom (9-11). CI chondrite normalization values are from (24).

In order to evaluate the possible heterogeneity of this stone, we analyzed two additional samples: agroundmass-rich sample (devoid of large olivine crystals, and weighing 181 mg) and a fragment of the sameglassy 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/Laratios are higher than those of other enriched shergottites (fig. S10). These two samples indicate that aLREE-enriched component, different from those previously recorded in other shergottites, is heterogeneouslydispersed throughout the matrix of Tissint.

The presence of short-lived 48V (T½=16 days), among other cosmogenic isotopes, demonstrates that the stoneswe analyzed are from the fall of July 18th (table S10). We measured stable cosmogenic isotopes of He, Ne and Arin three aliquots, consisting of matrix-rich, glass-matrix mixed, and glass-rich separates (table S11). The CosmicRay Exposure ages (CRE ages) computed for 3Hec, 21Nec, and 38Arc are 1.2 ± 0.4, 0.6 ± 0.2 and 0.9 ± 0.4 Marespectively, resulting in an average CRE age of 0.7 ± 0.3 Ma for Tissint. This age is in the range of CRE ages ofother shergottites, notably that of EETA79001 (0.73 ± 0.15 Ma (2)), suggesting that Tissint and other shergottiteswere ejected during a single event. Nitrogen isotopes were analyzed together with the noble gases. The glassaliquot displayed a well-defined excess of 15N, which persisted after correction for contribution of cosmogenic 15Nc(assuming a production rate of 6.7 ± 2.6 × 10−13 mol 15N/gMa) (12). This excess 15N is best explained by trappingof a Martian atmospheric component (2). Using a δ15N versus 40Ar/N correlation and taking a Martian atmosphericvalue from the Viking measurements, of 0.33 ± 0.03 (13), we obtain a δ15N value of 634 ± 60 ‰ (1σ), whichagrees well with the Viking measurement of 620 ± 160 ‰ (14) (Fig. 3).

Fig. 3

Gas analyses of the black glass. Both bulk analyses and stepheating analyses plot on a single mixing line between terrestrialatmospheric gas (at left) and Mars atmospheric gas (13), Zagamidata from (25).

Simultaneous measurement of carbon and nitrogen was carried out by stepped combustion-mass spectrometry ona small chip (21 mg) from the same sample we used for oxygen isotopic analysis (5). The sample had a totalcarbon abundance of 173 ppm and δ13C of -26.6 ‰, and contained 12.7 ppm nitrogen with total δ15N of -4.5 ‰. Attemperatures 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 mayhave been introduced during post-fall collection and sample storage, and are an unavoidable consequence of

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sample handling procedures, we cannot yet rule out the presence of small quantities of indigenous Martian organicmatter (5). At the highest temperatures of the extraction, there was a clear indication of the presence of trappedMartian atmosphere, with elevated δ13C and δ15N (even allowing for a cosmogenic component, blank-correctedδ13C reaches +16 ‰ and δ15N reaches +298 ± 25 ‰). At intermediate temperatures (600 – 800°C), there weremaxima in both δ13C (-14 ‰) and δ15N (+110 ‰), suggesting that the component bears some relationship to theMartian atmosphere. In addition, there was clear analytical evidence for a simultaneous release of sulfur (~19ppm), presumably from either sulphide or sulfate decomposition. This intermediate component probablycorresponds to a surface-derived weathering component, as identified in Tissint glass on the basis of REE, S andF data (see below). The third Martian component represents magmatic carbon, which is present in low abundance(1.4 ppm with δ13C of -26.3 ‰) and is associated with isotopically-light nitrogen (δ15N < +10 ‰).

Our study demonstrates that Tissint is a picritic shergottite comparable in many respects to EETA79001. Theblack shock glass resembles lithology C of EETA79001, as well as shock melt pockets commonly found in othershergottites (15). Major elements and oxygen isotope data indicate that this glass represents a melted mixture ofthe surrounding bulk rock, composed of olivine, maskelynite and clinopyroxene (5). However, this glass issubstantially different from the bulk meteorite and igneous groundmass in that it has a variable, but generally highS and F content; a distinct LREE-enriched composition; and a high δ15N value indicative of trapped Martianatmosphere.

The LREE-enriched composition of the glass is somewhat enigmatic. Phosphates are often invoked as a carrier ofREE. However, the P content of the black glass relative to bulk rock is not consistent with enrichment inphosphates. One possibility to explain the LREE composition of the glass might be selective crustal contaminationprior to final emplacement of the Tissint magma. Although LREE-enriched magmatic rocks have been generatedon 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-centimeterscale, as observed here. Decoupling of Ce from the other REE, indicates partial oxidation to Ce4+, a process thatrequires oxidising conditions, such as those that prevail in the near-surface environment of Mars. Surfaceweathering caused by leaching of phosphates by acid aqueous fluids, the process that is responsible for terrestrialalteration of eucritic meteorites in Antarctica (18), would also explain the LREE-enriched composition of the Tissintglass The high δ15N value of the Tissint glass, as well as its enrichment in S and F, demonstrates that it has beencontaminated by Martian surface components. In view of this evidence, the most likely explanation for the relativelyLREE-enriched composition of the glass, and the origin of the Ce anomaly, is that these features also reflect thepresence of a near-surface Martian component in Tissint. A Martian soil component was previously suggested forEETA79001 lithology C, which also contains Martian atmospheric gases (19). However, because this meteorite is afind, rather than a fresh fall like Tissint, there’s the possibility of terrestrial contamination, which complicates theinterpretation (20).

We propose the following scenario in order to explain the composite nature of Tissint. A picritic basalt wasemplaced at or near the surface of Mars. After some period, the rock was weathered by fluids, which had leachedelements from the Martian regolith. Subsequently, these fluids deposited mineral phases within fissures andcracks. The Martian weathering products are the most likely source of the required LREE, incompatible andvolatile elements. Upon impact, preferential, shock-induced melting occurred in the target rock along fractureswhere weathering products were concentrated. This melting produced the black glass and retained in it chemicalsignatures characteristic of the Martian surface. Shock melting also trapped a component derived from the Martianatmosphere, as revealed by stepped combustion-mass spectrometry. About 0.7 Ma ago, the sample was ejectedfrom Mars and eventually landed on Earth in July 2011. The Martian weathering features in Tissint described hereare compatible with spacecraft observations on Mars, including those made by the NASA Viking landers, MERSpirit 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.

References and Notes

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Acknowledgments: Authors acknowledge: Dean N. Menegas and family for their generous donationenabling the acquisition of Tissint (BM.2012,M1), Mohamed Aoudjehane for fieldwork, Adam Aaranson forfield information, Jenny Gibson for her assistance with oxygen isotope analysis, Luc Labenne for providingand loan of a sample, and Tony Irving for 400 mg powdered sample. This study was funded at Hassan IIUniversity Casablanca, FSAC by CNRST, Morocco and CNRS France, PICS SDU 01/10, and CMIFMPVolubilis (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 STFCgrant to the Planetary and Space Sciences Discipline; and University of Alberta, by NSERC grant 261740-03.

36.

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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 17O /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

samples. Consequently, determining the cosmogenic radionuclides 54Mn, 22Na, and 26Al 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

carbon end-window, housed in a 15 cm Pb cave (the inner 5 cm consisting of ‘old’, 210Pb-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, 232Th and 40K 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.

3. Supplementary Figures

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.

0.0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1En Fs

Wo

Fo Fa0 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.

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.

1

10

YHf

ZrNb

BaTh

U LaCe

PrNd Sm

EuGd

TbDy

HoEr

TmYb

Lu

Zagami

1

10

DaG 476

EETA79001A

SaU 005

1.25 g sample0.492 g sample

Tissint (W.R.)

Tissint

black glass"groundmass"

W.R.

sam

ple

/ cho

ndrit

e

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 K2O 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 P2O5 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 Fe3+ 0.022 0.022 0.019 0.029 0.085 0.180 0.027 0.117 0.083 0.149 Fe2+ 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 K2O 0.02 0.02 0.09 0.04 0.02 0-0.2 P2O5 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

SAMPLE δ17O‰ 1σ δ18O‰ 1σ Δ17O‰ 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).

Sample 14N ppm δ15NAIR,

‰ T(3Hec) T(21Nec) T(38Arc) ± ± ± ± ± 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) [C]

(ppm) δ13C (‰)

[N] (ppm)

δ15N (‰)

C/N (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

(soil?) 600 - 800 2.3 > -17 0.1 +63 25

4. Magmatic 800 - 1000 1.4 -26.3 0.2 < +10 12 5. Martian

atmosphere > 1000 < 1.2 < +16 < 0.04 < +300 40

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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