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Home , Allan Hills 84001, Amazonian (Mars), Chassigny (meteorite), Maskelynite, Merrillite, Northwest Africa 7034

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show evidence of being subjected to high shock pressures, with commonly converted to . volcanic are prob- Unique from Early ably not rare, given the observed widespread occurrence of volcanism on . However, Mars: -Rich Basaltic launch and delivery of such materials to Earth as has not been observed (9). Although NWA 7034 is texturally heterogeneous, both in the hand specimen and microscopically (Fig. 1), it can be considered a monomict breccia because Carl B. Agee,1,2* Nicole V. Wilson,1,2 Francis M. McCubbin,1,2 Karen Ziegler,1 Victor J. Polyak,2 it shows a continuous range of feldspar and Zachary D. Sharp,2 Yemane Asmerom,2 Morgan H. Nunn,3 Robina Shaheen,3 Mark H. Thiemens,3 compositions that are consistent with a Andrew Steele,4 Marilyn L. Fogel,4 Roxane Bowden,4 Mihaela Glamoclija,4 common petrologic origin (figs. S5 and S6). We Zhisheng Zhang,3,5 Stephen M. Elardo1,2 find no outlier or compositions that would indicate the existence of multiple lithologies We report data on the Northwest Africa (NWA) 7034, which shares some or exotic components. We also see no evidence petrologic and geochemical characteristics with known martian meteorites of the SNC for polymict lithologies in either the radiogenic or (i.e., shergottite, , and chassignite) group, but also has some unique characteristics stable ratios of NWA 7034 solids. How- that would exclude it from that group. NWA 7034 is a geochemically enriched crustal rock ever, many clasts and some of the fine-grained compositionally similar to and average martian crust measured by recent Rover and groundmass have phases that appear to have been Orbiter missions. It formed 2.089 T 0.081 billion ago, during the early Amazonian affected by secondary processes to form reaction in Mars’ geologic history. NWA 7034 has an order of magnitude more indigenous water than zones. We observed numerous reaction textures, most SNC meteorites, with up to 6000 parts per million extraterrestrial H2O released during some with a ferric oxide hydroxide phase; this stepped heating. It also has bulk isotope values of D17O = 0.58 T 0.05 per mil and a phase and are the hosts of the water D17 T heat-released water oxygen isotope average value of O = 0.330 0.011 per mil, suggesting in NWA 7034 (fig. S2). Impact processes are on April 7, 2013 the existence of multiple oxygen reservoirs on Mars. likely to have affected NWA 7034 by virtue of the fact that this meteorite was launched off of he only tangible samples of the planet porphyritic basaltic monomict breccia, with a few Mars, exceeding the escape velocity—presumably Mars available today for study in Earth- euhedral phenocrysts up to several millimeters by an impact—although the shock pressures did Tbased laboratories are the so-called SNC and many phenocryst fragments of dominant an- not produce maskelynite. One large (1-cm) quench (shergottite, nakhlite, and chassignite) meteor- desine, low-Ca pyroxene, , and melt clast that was found could originate from ites (1) and a single cumulate set in a fine-grained, clastic to plumose, shock processes (fig. S3). On the other hand, the ( 84001). The SNCs currently number groundmass with abundant and mag- very fine groundmass with the large phenocrystic

110 named stones and have provided a treasure hemite; accessory sanidine, anorthoclase, Cl-rich and strongly suggests an www.sciencemag.org trove for elucidating the geologic history of Mars apatite, , rutile, , pyrite, a ferric eruptive volcanic origin for NWA 7034; thus, it is (2). But, because of their unknown field context oxide hydroxide phase, and a calcium carbonate likely that volcanic processes are a source of the and geographic origin on Mars and their fairly were identified by electron microprobe analyses brecciation. narrow range of types and forma- on eight different sections at the University of It has been shown (10) that Fe-Mn systemat- tion ages (3), it is uncertain to what extent SNC NewMexico(UNM).X-raydiffraction(XRD) ics of pyroxenes and are an excellent meteorites sample the crustal diversity of Mars. analyses conducted at UNM on a powdered sam- diagnostic for classifying planetary basalts. The In fact, geochemical data from NASA’sorbiter ple and on a polished surface show that plagio- Fe-Mn systematics of NWA 7034 pyroxenes, as

and lander missions suggest that the SNC me- clase feldspar is the most abundant phase (38.0 T determined by electron microprobe analyses, most Downloaded from teorites are a mismatch for much of the martian 1.2%), followed by low-Ca pyroxene (25.4 T resemble the trend of the SNC meteorites from crust exposed at the surface (4). For example, the 8.1%), clinopyroxenes (18.2 T 4.0%), oxides Mars (Fig. 2); other planetary pyroxenes such as basalts analyzed by the Mars Exploration Rover (9.7 T 1.3%), alkali feldspars (4.9 T 1.3%), and in lunar samples and basalts from Earth are poor Spirit at Crater (5, 6) are distinctly differ- apatite (3.7 T 2.6%). The x-ray data also indicate a matches for NWA 7034. Furthermore, feldspar ent from SNC meteorites, and Odyssey Orbiter minor amount of iron sulfide and chromite. The compositions (fig. S5) (8) and compositions of gamma-ray spectrometer (GRS) data (7)show data are also consistent with magnetite and mag- other accessory phases in NWA 7034 are con- that the average martian crust composition does hemite making up ~70% and ~30%, respectively, sistent with commonly found in SNC not closely resemble SNC. of the iron oxide detected (8). meteorites (11) but not with any other known NWA 7034, on deposit at the Institute of Me- Petrology and geochemistry. Numerous clasts group. However, the average bulk teoritics in Albuquerque, was purchased by Jay and textural varieties are present in NWA 7034, chemical composition of NWA 7034 does not Piatek from Aziz Habibi, a Moroccan meteorite including gabbros, quenched melts, and iron oxide– overlap in major element space with SNC; in- dealer, in 2011. It is a 319.8-g single stone, and ilmenite-rich reaction spherules (figs. S1 to S4) stead, it is remarkably similar to the geochemistry (8). However, the dominant textural type is a fine- of the rocks and soils at Gusev Crater and the grained basaltic porphyry with feldspar and average martian crust composition from the Odyssey 1Institute of , University of New Mexico, Albuquerque, NM 87131, USA. 2Department of Earth and Planetary Sciences, pyroxene phenocrysts. NWA 7034 is a mono- Orbiter GRS (Fig. 3 and figs. S7 and S8). NWA University of New Mexico, Albuquerque, NM 87131, USA. 3De- mict brecciated porphyritic that is textur- 7034, Gusev rocks, and the GRS average martian partment of Chemistry and , University of Califor- ally unlike any SNC meteorite. Basaltic breccias crust all have higher concentrations of the alkali 4 nia, San Diego, La Jolla, CA 92093, USA. Geophysical Lab, are common in Apollo samples, lunar meteorites, elements sodium and potassium than do SNC Carnegie Institution of Washington, Washington, DC 20005, USA. 5School of Environmental Science and Engineering, and HED meteorites but are wholly absent in meteorites. Other major and minor element ratios Yat-Sen University, Guangzhou 510275, China. the world’s collection of SNC meteorites (9). The such as Mg/Si, Al/Si, and Ni/Mg have similarly *To whom correspondence should be addressed. E-mail: absence of shock-produced SNC breccias seems good matches between NWA 7034 and Gusev [email protected] curious at face value, because nearly all of them Crater rocks (figs. S7 and S8). Although some

780 15 FEBRUARY 2013 VOL 339 SCIENCE www.sciencemag.org RESEARCH ARTICLES experimental work has been conducted to a negative slope, and light rare-earth elements fied in any of the investigated thin sections or martian meteorites to surface rocks analyzed by (LREE) are elevated relative to the heavy rare- probe mounts. the Mars Exploration Rovers (12–14), and aside earth elements (HREE) [CI- normalized Radiometric . A five-point isochron gives from the exotic “” (15)atMeridiani lanthanum-ytterbium ratio (La/Yb)N =2.3].Bulk an Rb-Sr age for NWA 7034 of 2.089 T 0.081 Planum and a hypothesized com- SNC meteorites are much less enriched in REE billion years ago (Ga) [2s; mean square weighted ponent in Tissint melt pockets (16), there has been (17) than is NWA 7034 (fig. S10); although deviation (MSWD) = 6.6], an initial 87Sr/86Sr no direct link between the bulk chemical com- LREE enrichment relative to HREE and REE ratio of 0.71359 T 54 (Fig. 4), and a calculated positions of martian meteorites and surface rocks patterns with negative slopes are seen in , source 87Rb/86Sr ratio of 0.405 T 0.028 (Fig. 5). to date. only magmatic inclusions and mesostasis in The Sm-Nd data for the same samples result in an The rare-earth element (REE) abundances of nakhlites and estimated nakhlite parent isochron of 2.19 T 1.4 Ga (2s). The high un- NWA 7034 were determined by multicollector have LREE enrichments comparable to those certainty in the latter is due to minimal separation inductively coupled plasma mass spectrometry of NWA 7034 (17, 18). We observed ubiquitous, between the data points generated from analy- (Neptune MC-ICP-MS) at UNM. They are en- relatively large (up to ~100 mm) Cl-rich apatite sis of separates. The small error on the riched relative to chondritic abundances, with grains in NWA 7034 that presumably harbor a Rb-Sr age may come from the abundance and a marked negative europium anomaly (Eu/Eu* = substantial fraction of the REEs in this meteorite, variety of feldspar compositions in NWA 7034 0.67) (fig. S9 and table S2). The REE pattern has as neither nor were identi- (fig. S5). Furthermore, we are confident that the Rb-Sr isochron and variations in the 87Sr/86Sr values are the result of the time-integrated ra- diogenic growth from 87Rb and not the results of mixing between end members with different 87Sr/86Sr values (figs. S11 to S14). The combined REE and isotopic data show that NWA 7034 is an enriched martian crustal rock (Fig. 5). The whole rock has 143Nd/144Nd = 0.511756 and 147Sm/144Nd = 0.1664, giving a calculated initial (source value) 143 144 T e Nd/ Nd = 0.509467 0.000192 (initial Nd = on April 7, 2013 –9.1 T 1.7, calculated using the Rb-Sr age). This requires that NWA 7034 was derived from an enriched martian reservoir (19), with an inferred time-integrated 147Sm/144Nd = 0.1680 T 0.0061, assuming separation from a chondrite-like mar- tian mantle at 4.513 Ga (18). Data for each of our analyses are available in table S3. An age of ~2.1 Ga for NWA 7034 would make it the only dated 19

meteorite sample from the early Amazonian ( ) www.sciencemag.org epochinMars’ geologic history. NWA 7034 is derived from the most enriched martian source identified to date; it is even more enriched than the most enriched shergottites (20–23) (Fig. 5). On the basis of REE enrich- ment, isotopic values, and match to rover ele- mental data, NWA 7034 may better represent the

’ crust than other martian Downloaded from meteorites. Although NWA 7034 may not be rep- resentative of a magmatic liquid, the negative eu- ropium anomaly and the absence of merrillite or whitlockite (24) suggest either that the (s) parental to basaltic breccia NWA 7034 under- went fractionation before eruption or that feldspar was left in the residuum during partial melting. Because of the instability of pla- gioclase at high pressure (25), these processes would have necessarily occurred in the crust or upper mantle of Mars. Consequently, the geo- chemically enriched source that produced NWA 7034 could have originated from the martian crust or mantle, much like the geochemically enriched reservoir(s) that are recorded in the shergottites (26–30). Carbon. Confocal Raman imaging spectros- copy conducted at the Carnegie Institution Geo- physical Laboratory in Washington, DC, identified Fig. 1. (A) Two views of the NWA 7034 hand specimen. (B) Backscatter electron image of porphyritic the presence of macromolecular carbon (MMC) texture in NWA 7034. Large dark crystals are feldspar; large light-colored crystals are pyroxene. A portion within mineral inclusions in the groundmass min- of a gabbroic clast is shown above the scale bar. erals of NWA 7034 (8). This MMC is spectrally

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similar to reduced organic macromolecular car- D17O = 0.58 T 0.05‰ (n = 21). These interlab error of the acid-washed samples; this indicates bon that has been identified in several shergottites values of bulk samples are in good agreement but that NWA 7034 has, at most, only minor terres- and a single nakhlite meteorite (fig. S15) (30), are significantly higher than literature values for trial weathering products, which would drive indicating that the production of organic carbon SNC meteorites (D17O range 0.15 to 0.45‰) the non–acid-washed values closer to D17O= from abiogenic processes in the martian interior (33–36). Figure 6 shows that the d18O values (5.5 0.00. The slope of the best-fit line to the combined may not be unique to SNC-like source regions in to 7.0‰ versusSMOW)ofNWA7034arehigh- UNM acid-washed and non–acid-washed data is Mars. Steele et al.(31) also demonstrated that the er than any determination from the SNC group. 0.517 T 0.025, which suggests that the oxygen formation mechanism of MMC requires reducing The D17O values of the non–acid-washed sam- isotopic composition of NWA 7034 is the result magmatic conditions consistent with oxygen fu- ples measured at UNM are similar to and within of mass-dependent fractionation processes. gacities below the fayalite-magnetite-quartz (FMQ) buffer. Consequently, much of the ferric iron in the oxides of NWA 7034, as evidenced by electron 0.040 probe microanalysis and XRD, was likely a product Mars of oxidation subsequent to igneous activity as a 0.035 result of secondary processes. Bulk carbon and carbon isotopic measure- 0.030 ments on NWA 7034 were also carried out at Carnegie, using combustion in an elemental ana- 0.025 NWA 7034 lyzer (Carlo Erba NC 2500) interfaced through a Conflo III to a Delta V Plus isotope ratio mass 0.020

spectrometer (ThermoFisher) in the same manner Mn (afu) as the data reported by (31, 32)[see(8)]. These 0.015 data indicate that carbon is present within mineral Moon inclusions in NWA 7034 at concentrations of at 0.010 least 22 T 10 ppm, and that the d13C isotopic value – T ‰ 0.005 of this carbon is 23.4 0.73 , which is very on April 7, 2013 similar to previous bulk C and d13Canalysesof Earth NWA 7034 Pyroxenes carbon included in shergottite meteorites ana- 0.000 lyzed in the same manner (31, 32). These data 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 indicate that multiple geochemical reservoirs in Fe (afu) the martian interior may have similarly light d13C Fig. 2. Fe versus Mn (atomic formula units) showing the trend for all NWA 7034 pyroxenes (cyan dots, values. The bulk C concentration in the untreated 349 microprobe analyses) and, for comparison, pyroxene trends from Mars (red), the Moon (), and sample performed in these measurements was Earth (blue) (10). 2080 T 80 ppm C, with a corresponding d13C – T ‰

value of 3.0 0.16 . Scattered carbonate vein- www.sciencemag.org lets from desert weathering were observed by 10 backscatter electron imaging and element map- ping with the electron microprobe, especially 9 Trachyte in the near-surface material but less frequently in the deeper interior slices of NWA 7034. Although Trachy- Rhyolite 8 this carbonate is below the detection limits of our XRD analyses of the bulk sample and is thus a Tephrite 7 Basaltic

minor phase within the meteorite, we believe that trachy- Downloaded from this weathering product is sampled in our bulk andesite 8 O wt% 6 Foidite Trachy- carbon and carbonate analyses ( ) (fig. S16). 2 basalt Oxygen . Measurements of oxygen 5

isotopic composition were performed by laser O+K fluorination at UNM on acid-washed and non– 2 4 acid-washed bulk sample and at the University of Na California, San Diego (UCSD), on vacuum pre- 3 GRS heated (1000°C) bulk sample (table S4). The triple oxygen isotope precision on San Carlos Picro- 18 2 standard [d O=5.2‰ versus standard basalt Basaltic mean ocean water (SMOW); D17O=0‰] analyzed Andesite Dacite Andesite during sessions at UNM was D17O=T0.03‰;the 1 precision at UCSD using NBS-28 quartz standard SNC Meteorites (d18O = 9.62‰) was also D17O=T0.03‰.In 0 35 40 45 50 55 60 65 70 75 total, we carried out 21 analyses of bulk NWA 7034 (Fig. 6). The mean value obtained at UNM SiO2 wt% 17 was D O=0.58T 0.05‰ (n = 13) for acid- Fig. 3. classification scheme based on the abundance of alkali elements and SiO ,modified 17 2 washed samples and D O = 0.60 T 0.02‰ (n =6) after McSween et al.(4). Red dots denote analyses of rocks and soils at Gusev Crater by the Alpha Particle for non–acid-washed samples; at UCSD the X-ray Spectrometer (APXS) onboard the Spirit rover (5, 6). The yellow rectangle is the average martian mean value was D17O = 0.50 T 0.03‰ (n =2) crust as measured by the GRS onboard the Mars Odyssey orbiter (7). The pink field is the known range of for vacuum preheated samples that were dewa- martian meteorite (SNC) compositions. The cyan dot is the mean value of bulk NWA 7034 as determined tered and decarbonated. The combined data give by 225 electron microprobe analyses of fine-grained groundmass; error bars denote SD.

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There are no other known or plan- Venus because it experienced low-temperature otic material. The idea of separate long-lived etary samples with bulk oxygen isotope values alteration on its and has significant silicate reservoirs is supported by radiogenic similar to those of NWA 7034. Most achondrite indigenous water, which would not persist with isotope studies (21, 23). The distinct D17Oand groups have negative or near-zero D17O values, the high surface temperatures on Venus (40). d18O values of the silicate fraction of NWA as do rocks from Earth and the Moon. The oxy- The distinct d18OandD17O values relative to 7034 relative to all SNC meteorites measured to gen isotope compositions of Venus and Mercury other martian meteorites can be explained by date further support the idea of distinct litho- are currently unknown, but NWA 7034 is too multiple reservoirs—either within the martian lith- spheric reservoirs that have remained unmixed oxidized and iron-rich to be derived from Mer- osphere or between the lithosphere and a surficial throughout martian history. A near-surface com- cury (37–39), and it seems to be a poor match for component (41, 42)—or by incorporation of ex- ponent with high D17O values has been proposed on the basis of analysis of low-temperature al- teration products (41–43), and this may in part 0.780 explain the D17O differences between the bulk 0.722 and “water-derived” components of NWA 7034. However, the D17O value of 0.58‰ for the bulk 0.770 Drk-1 silicate is different from the D17O value of 0.3‰ 0.721 Light-1 found in all SNC samples measured to date. If 0.760 Drk-2 materials with a D17O value other than 0.3‰ are attributed to a surficial (atmospheric) component, Drk-3 0.720 then the bulk of NWA 7034 would have nec- 0.750 0.22 0.24 0.26 0.28 essarily undergone extensive exchange with this Sr

86 reservoir. This is a possibility, given the abun-

Sr/ 0.740 dance of low-temperature iron oxides. The ram-

87 ifications of distinct lithospheric reservoirs are very different from those attributed to a different 0.730 WR surficial reservoir. The latter could be explained Age = 2089 ± 81 Ma Drk-2 by photochemical-induced isotope fractionation on April 7, 2013 87 86 and/or hydrodynamic escape (44–46), whereas 0.720 Drk-1 Initial Sr/ Sr = 0.71359 ± 54 Drk-3 MSWD = 6.6 the former is consistent with a lack of initial planet-wide homogenization and an absence 0.710 of plate tectonics (41). Isolated lithospheric 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 oxygen isotope reservoirs are inconsistent with 87Rb/86Sr a global magma ocean scenario for early Mars, Fig. 4. Rb-Sr whole-rock mineral isochron of NWA 7034. The mineral fractions are labeled as Light-1, which would have very efficiently homogenized Drk-1, Drk-2, and Drk-3 according to abundance of dark magnetic minerals. Light-1, with high 87Rb/86Sr, oxygen isotopes in the planet, as occurred for ’ was the least magnetic fraction. An MSWD value of 6.6 suggests that the small scatter in the values cannot Earth and the Moon. Instead, Mars differentia- www.sciencemag.org be explained by analytical errors and may include slight isotopic heterogeneities in the rock. 2s tion could have been dominated by basin-forming measurement errors were used for the 87Sr/86Sr data; 2% errors for the 87Rb/86Sr data were used for age impacts that left regional or even hemisphere- calculation. Larger errors were assigned to the 87Rb/86Sr ratios because of the inability to perform internal scale magmatic complexes (47, 48) with dis- mass fractionation on Rb isotopic measurements (Rb only has two isotopes). There was not enough Sm and tinct and varied isotopic and geochemical Nd in the mineral fractions to provide a meaningful age. characteristics.

A 2.5 B 0.35 Downloaded from NWA 7034 Lunar M a c Cumulat es 2.0 0.30

Nd QUE 94201 44 1 1.5 DaG 476 Los Angeles 1 Shergotty Sm/ 0.25 Nak/Chas Zagami 147 EET 79001A/ B

La/ Yb 1.0 LEW 88516 ALH 77005 ALH 77005 Source 0.20 Zagami 0.5 LEW 88516 Shergotty DaG 476 Lunar EET 79001A/ B QUE 94201 Los Angeles1 NWA 7034 KREEP 0.0 0.15 -20-100 102030405060 0.0 0.1 0.2 0.3 0.4 0.5 0.6 87 86 Nd at 175 Ma Source Rb/ Sr

Fig. 5. (A) Plot of bulk rock La/Yb ratio versus eNd calculated at 175 Ma for mantle sources. Solid line represents two-component mixing line between NWA 7034 and basaltic shergottites. Solid line represents two-component depleted lunar mafic cumulates and lunar potassium, rare-earth elements, and mixing line between NWA 7034 and QUE 94201. (B)Plotofcalculatedparent/ phosphorus (KREEP). Depleted lunar mafic cumulates are estimated by (54–56). daughter source ratios for NWA 7034, basaltic shergottites, nakhlites includ- Lunar KREEP is estimated by (56). Data for basaltic shergottites, nakhlites, and ing (which has values similar to nakhlites) (Nak/Chas), and lunar Chassigny are from (22, 23) and references therein.

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Another possibility is that NWA 7034 origi- Fig. 6. Oxygen isotope 5.0 nally had oxygen isotope values similar to or the plot showing the values same as SNC, but a cometary component with 4.5 18 17 17 of NWA 7034 from this higher d O, d O, and D O was mixed with it study. Cyan dots, 13 analy- through impact processes on Mars, thus producing ses of acid-washed and 17 4.0 a D O excess relative to SNC. Until we find six analyses of non–acid- clear evidence of such an exotic component in washed bulk samples 3.5 NWA 7034, this scenario seems less likely than the (UNM); cyan squares, two other two. analyses of dry, decarbon- 3.0 Water. The oxygen isotope ratio of water re- ated bulk preheated to leased by stepped heating in a vacuum at UCSD 1000°C (UCSD). Red dots (table S5) shows that most, possibly all, of the are SNC meteorites from V-SMOW) O (per mil 2.5

17 SNC water in NWA 7034 is extraterrestrial, with D17O the literature (33–36, 41). δ TFL values well above the terrestrial fractionation line TFL, terrestrial fractiona- 2.0 NWA 7034 (UCSD) (Fig. 7). NWA 7034 water falls primarily within tionline(slope0.528). NWA 7034 (UNM) the range of values for bulk SNC meteorites, with a 1.5 weighted mean value of D17O = +0.33 T 0.01‰; 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 δ18 d18O and d17O values give a slope of 0.52, O (per mil V-SMOW) indicating mass-dependent fractionation. Note that the D17O value for NWA 7034 water is lower than, and outside the range of, the D17O Fig. 7. Plot of D17Over- 0.8 for bulk NWA 7034, offering clear evidence that sus temperature, showing 0.7 there are multiple distinct oxygen isotope sources values for NWA 7034 wa- for this sample. The D17O value of the water ter released by stepped 0.6 heating. Vertical error released at the 500° to 1000°C range (+0.09‰) 0.5 bars are given for each

approaches terrestrial values, possibly because of on April 7, 2013 decomposition of the terrestrial carbonate veins data point; horizontal line 0.4 in the meteorite and equilibration of the produced segments show the tem- perature range for each 0.3 CO2 with the released water. Karlsson et al.(41) step, and the thickness 0.2 reported oxygen isotope values of water from V-SMOW) O (‰

of the line segment indi- 17 Δ

several SNC meteorites and also saw that they 0.1 D17 cates the relative pro- differed from the O of the bulk SNC samples. portion of water released D17 0.0 However, their observed O relationship be- at each step. Dashed line tween bulk rock and water is reverse to the one is the mean value of -0.1 17 Δ17 ± seen in NWA 7034, with in general hav- D OforNWA7034wa- Water Released in Stepwise Heating. Mean value O=0.330 0.011‰ www.sciencemag.org D17 -0.2 ing more positive O values than their respec- ter. Also shown are ranges 0 200 400 600 800 1000 17 tive host rocks (Nakhla, Chassigny, and Lafayette). of D OforbulkNWA Temperature (°C) Only two shergottites (Shergotty and EETA- 7034 analyses and for 79001A) have waters with D17O values more bulk SNC values from the literature. negative than the host rock, and Nakhla has water similar to its host rock. Romanek (43) analyzed iddingsite, an alteration product of oli- at 804°C and 1014°C, respectively (table S6), fractionated as a function of temperature, or there

vine and pyroxene, in Lafayette and found the similar to values seen in the nakhlites (50). are two distinct hydrogen isotope reservoirs. Downloaded from D17O value is 1.37‰ for a 90% iddingsite sep- Figure 8 shows that most of the water in NWA Our data show that NWA 7034 has more than arate, supporting the positive D17O shift of 7034 is released between approximately 150° an order of magnitude more indigenous water Lafayette water relative to host rock. Karlsson and 500°C, and that there are two plateaus of dD than most SNC meteorites. The amount of water (41) argued that this D17O difference suggested a values, one around –100‰ at 50° to 200°C and released at high temperature (>320°C) is 3280 T lack of equilibrium between water and host rock, a second around +300‰ at 300° to 1000°C. 720 ppm. Leshin et al.(50) measured an average with the lithosphere and hydrosphere having dis- This suggests that there are two distinct dD of 249 T 129 ppm H2O released above 300° to tinct oxygen isotopic reservoirs. Our data sup- components in NWA 7034: a low-temperature 350°C in seven bulk SNC meteorites, with the ex- port this conclusion but suggest that the D17O negative-value component and a high-temperature ception of the anomalous Lafayette nakhlite (which value of the “water” reservoir is not always hea- positive-value component. One possibility is that released 1300 ppm H2O above 300°C). They (50) vier than the rock reservoir. the low-temperature negative values are from argued that some of the water released at tem- We determined the deuterium/hydrogen iso- terrestrial water contamination, although the peratures as low as 250°C could in fact be from tope ratio (dD value versus SMOW) and the D17O values in water released at even the lowest martian alteration products. Given our oxygen water content of whole-rock NWA 7034 at UNM temperature step of 50°C have a 0.3‰ anomaly water analyses, this could also be the case for NWA by both bulk combustion and stepped heating (Fig. 7). It is also possible that protium-rich water 7034 at temperatures as low as 50°C. Hence, the in a continuous-flow helium stream with high- is released at the lowest steps of dehydration, total amount of martian water in NWA 7034 could temperature carbon reduction (49) (Fig. 8 and although such fractionation is not observed on be in the vicinity of 6000 ppm, possibly support- table S6). Six whole-rock combustion measure- terrestrial samples. Alternatively, the hydrogen ing hypotheses that aqueous alteration of near- ments yielded a bulk water content of 6190 T but not the oxygen isotope ratios could have been surface materials on Mars occurred during the early 620 ppm. The mean dD value for the bulk com- affected by terrestrial alteration. Finally, it is Amazonian epoch (2.1 Ga) either by magmati- bustion analyses was +46.3 T 8.6‰. The max- possible that nearly all the released water from cally derived or meteoric aqueous fluids (51–53). imum dD values in two separate stepwise heating NWA 7034 is in fact martian and not terrestrial. In Conclusions. The young crystallization age of experiments were +319‰ and +327‰, reached this case, the hydrogen isotope ratios have NWA 7034, 2.1 Ga, requires that it is planetary

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400 45 400 45

40 40 % H % H 300 300 35

2 35 2 O of total evolved water O of total evolved water 200 30 200 30

25 25 100 100 20 20

15 15 D (‰ V-SMOW) D (‰ 0 D (‰ V-SMOW) D (‰ 0 δ δ 10 10 -100 -100 5 5

-200 0 -200 0 0 100 200 300 400 500 600 700 800 900 1000 0 200 400 600 800 1000 1200 Temperature (°C) Temperature (°C) Fig. 8. Plots of dD versus temperature, showing data for the NWA 7034 bulk sample during stepped heating. The horizontal solid lines represent the temperature intervals; circles are mid-interval temperatures. The two plots represent two aliquots of the NWA 7034 sample. in origin. Its major, minor, trace, and isotopic 16. H. Chennaoui Aoudjehane et al., Science 338, 785 43. C. S. Romanek et al., Meteorit. Planet. Sci. 33, 775 chemistry is inconsistent with originating from (2012). (1998). 17. M. Wadwa, G. Crozaz, J.-A. Barrat, Antarct. Meteorite Res. 44. E. D. Young, R. D. Ash, P. England, D. Rumble 3rd, Earth, the Moon, Venus, or Mercury, and it is 17, 97 (2004). Science 286, 1331 (1999). most similar to rocks from Mars. Nonetheless, 18. J. M. Day, L. A. Taylor, C. Floss, H. Y. Mcsween Jr., 45. Y. L. Yung, W. B. Demore, Photochemistry of Planetary

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2. H. Y. McSween, T. L. Grove, J. Wyatt, J. Geophys. Res. L. A. Taylor, Geochim. Cosmochim. Acta 73, 2190 (2009). 56. P. H. Warren, J. T. Wasson, Rev. Geophys. Space Phys. 17, Downloaded from Planets 108, 5135 (2003). 29. A. B. Sarbadhikari, C. A. Goodrich, Y. Liu, J. M. D. Day, 73 (1979). 3. L. E. Nyquist et al., in Chronology and Evolution of Mars, L. A. Taylor, Geochim. Cosmochim. Acta 75, 6803 R. Kallenbach, J. Geiss, W. K. Hartmann, Eds. (Springer, (2011). Acknowledgments: We thank J. Piatek for acquiring the New York, 2001), p. 105. 30. C. D. K. Herd, Meteorit. Planet. Sci. 38, 1793 (2003). NWA 7034 specimen and for his generous donation to the 4. H. Y. McSween Jr., G. J. Taylor, M. B. Wyatt, Science 324, 31. A. Steele et al., Science 337, 212 (2012). UNM Meteorite Museum, which has enabled this research 736 (2009). 32. M. M. Grady, A. B. Verchovsky, I. P. , Int. J. and sample allocations for future research on NWA 7034. 5. R. Gellert et al., J. Geophys. Res. Planets 111, E02S05 Astrobiol. 3, 117 (2004). We also thank M. Spilde, V. Atudorei, and J. Connolly at the (2006). 33. R. N. Clayton, T. K. Mayeda, Earth Planet. Sci. Lett. 62, University of New Mexico for assistance with data collection. 6. D. W. Ming et al., J. Geophys. Res. Planets 113, E12S39 1 (1983). Supported by NASA Cosmochemistry Program grants (2008). 34. I. A. Franchi, I. P. Wright, A. S. Sexton, C. T. Pillinger, NNX11AH16G (C.B.A.) and NNX11AG76G (F.M.M.). S.M.E. 7. W. V. Boynton et al., J. Geophys. Res. Planets 112, Meteorit. Planet. Sci. 34, 657 (1999). acknowledges support from the New Mexico Space Grant E12S99 (2007). 35. D. W. Mittlefehldt, R. N. Clayton, M. J. Drake, K. Righter, Consortium, NASA Earth and Space Science Fellowship 8. See supplementary materials on Science Online. Rev. Mineral. Geochem. 68, 399 (2008). NNX12AO15H, and NASA Cosmochemistry grant NNX10AI77G 9. S. P. Wright, P. R. Christensen, T. G. Sharp, J. Geophys. 36. D. Rumble et al., Proc. 40th Lunar Planet. Sci. Conf. 40, to Charles K. Shearer. M.H.T. and R.S. acknowledge NSF Res. Planets 116, E09006 (2011). 2293 (2009). award ATM0960594, which allowed the development of an 10. J. J. Papike, J. M. Karner, C. K. Shearer, P. V. Burger, 37. F. M. McCubbin, M. A. Riner, K. E. Vander Kaaden, analytical technique to measure oxygen triple isotopic Geochim. Cosmochim. Acta 73, 7443 (2009). L. K. Burkemper, Geophys. Res. Lett. 39, L09202 composition of small (<1 mM) sulfate samples. 11. F. M. McCubbin, H. Nekvasil, Am. Mineral. 93, 676 (2012). Supplementary Materials (2008). 38. M. A. Riner, F. M. McCubbin, P. G. Lucey, G. J. Taylor, www.sciencemag.org/cgi/content/full/science.1228858/DC1 12. J. Filiberto, Geochim. Cosmochim. Acta 72, 690 J. J. Gillis-Davis, Icarus 209, 301 (2010). Materials and Methods (2008). 39. L. R. Nittler et al., Science 333, 1847 (2011). Figs. S1 to S16 13. H. Nekvasil, F. M. McCubbin, A. Harrington, S. Elardo, 40. K. Lodders, B. Fegley, The Planetary Scientist’s Tables S1 to S6 D. H. Lindsley, Meteorit. Planet. Sci. 44, 853 (2009). Companion (Oxford Univ. Press, Oxford, 1998). References (57–71) 14. F. M. McCubbin, H. Nekvasil, A. D. Harrington, 41. H. R. Karlsson, R. N. Clayton, E. K. Gibson Jr., S. M. Elardo, D. H. Lindsley, J. Geophys. Res. Planets 113, T. K. Mayeda, Science 255, 1409 (1992). 15 August 2012; accepted 14 December 2012 E11013 (2008). 42. J. Farquhar, M. H. Thiemens, T. Jackson, Science 280, Published online 3 January 2013; 15. J. Zipfel et al., Meteorit. Planet. Sci. 46, 1 (2011). 1580 (1998). 10.1126/science.1228858

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