Thermal metamorphic evolution of the Pułtusk H chondrite breccia – compositional and textural properties not included in petrological classification

The thermal history that chondrites experienced on their parent body is an aspect of their petrological classification. However, in the classification scheme, metamorphic conditions are generally limited to the peak metamorphic temperature attained, while it is known that reconstruction of the genuine thermal evolution of any rock requires identification of various metamorphic factors, definition of the temperature-time path during metamorphism and characterization of the processes responsible for heating. Study of the brecciated Pułtusk H chondrite shows that the meteorite comprises both low and high petrologic type material and should be classified as a H3.8–6 chondrite. Based on the textures and mineral and chemical composition, the thermal metamorphic history of the breccia is reconstructed and it is shown to be inconsistent with the petrologic classification; the textural maturation and degree of compositional equilibrium in the meteorite do not correspond to the temperatures attained. The metamorphic conditions are shown to be a function of the primary composition of the accreted minerals and of two metamorphic phases, progressive and retrogressive. First, a prograde phase led to textural maturation and equilibration of the chemical composition of silicates and oxides. The peak metamorphic temperatures were at least ~700ºC for the type 3.8. and 4 material, and up to ~1000ºC in H6 clasts i.e., sufficient to locally give rise to partial melting. The following retrograde metamorphism led to compositional re-equilibration of minerals and textural re-equilibration of minerals with partial melts. The cooling rate during retrograde metamorphism down to at least ~700ºC was low, which allowed potassium feldspar to form patches in Na-plagioclase and pseudobrookite-armalcolite breakdown to form an association of ilmenite and rutile. The two-phase metamorphic evolution of the Pułtusk breccia was the most likely the result of impact heating, which affected the parent body in its very early history.This article is available to all readers online, published under a creative commons attribution license (https://creativecommons.org/licenses/by/3.0/). The attached file is the published version of the article which can also be accessed here: https://doi.org/10.7306/gq.126

Sulfur and chlorine in nakhlite clinopyroxenes: Source region concentrations and magmatic evolution

The volatile concentrations of the martian mantle and martian magmas remain important questions due to their role in petrogenesis and planetary habitability. The sulfur and chlorine concentrations, and their spatial distribution, in clinopyroxenes from nakhlites MIL 03346, Nakhla, and NWA 998 were measured to provide insight into these volatiles in the parental melts and source regions of nakhlites, and to constrain the evolution of the nakhlite melts. Sulfur and chlorine in four clinopyroxene crystals from MIL 03346, four from Nakhla, and five from NWA 998 were measured in crystal cores and rims by synchrotron X-ray fluorescence using beamline I18 at the Diamond Light Source. Portions of two crystals from MIL 03346 and one from Nakhla were mapped for S and Cl; a few reconnaissance analyses of Cl and F in MIL 03346 and Nakhla were made by ion microprobe. Clinopyroxene cores in Nakhla and NWA 998 contain ~ 10 ppm S, ~ 10 ppm Cl and ~ 74 ppm F (only Nakhla analyzed), whereas the cores of MIL 03346 contain ~ 10 ppm S, ~ 5 ppm Cl and ~ 53 ppm F. Using the volatile concentrations in the cores combined with previously determined partition coefficients we calculate that these clinopyroxenes crystallized from evolved basaltic melts containing ~ 500 ppm S, ~ 500 to 1900 ppm Cl, and 160 to 420 ppm F. These evolved melts can be used to calculate primitive melts in equilibrium with martian peridotite and the concentrations of S, Cl and F in the mantle source region of the nakhlite melts. Depending upon the extent of melting (5 to 30 %) necessary to produce the primary melts associated with nakhlites, our calculations indicate that the nakhlite source region has a S concentration between 20 (5 % melting) to 120 ppm (30 % melting), Cl between 16 to 97 ppm, and F between 14 to 48 ppm. These concentrations in the nakhlite magma source region are similar to previous estimates for the martian mantle; our calculated source region concentrations of F and Cl agree best with previous estimates if the martian mantle undergoes 10 to 20% melting to produce primary magmas that evolve to be parental to nakhlites. However, our maximum estimated sulfur concentration of the source (calculated for 30 % melting) is near previous minimum estimates for the martian mantle, suggesting the possibility that the nakhlite source region is depleted in sulfur relative to much of Mars’ mantle. Mapping the spatial distribution of volatiles in three clinopyroxene crystals demonstrates that S and Cl concentrations of the evolving melts changed significantly from the core to the rim, particularly those in MIL 03346. Increasing S and Cl concentrations between the core and rim of MIL 03346 crystals are attributed to incorporation of additional volatiles through assimilation, but the Nakhla crystal shows no such evidence. However, concentrations of Cl and S at some outer crystal rims of one MIL 03346 crystal decrease, most probably due to volatile degassing during the final stages of clinopyroxene growth

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

Copper in ordinary chondrites: Proxies for resource potential of asteroids and constraints for minimum-invasive and economically efficient exploitation

Ordinary chondrites originate from S-type asteroids. These meteorites can be used for laboratory studies that further our understanding of the geological conditions on asteroids, including assessment of their resource potential. Asteroids have since long been considered to host significant resources of siderophilic elements such as Fe, Ni, Co, Cu, that could be exploited in situ. However bulk rock mining would be largely impractical. In this paper, we report on abundance and mineral occurrences of copper in H chondrites, identify Cu carrier minerals and interpret their distribution in the context of processes that must have affected parent bodies. This leads us to suggestion that some parts of S-type asteroids contain Cu in a form and amount that would satisfy requirements of potentially economically and environmentally more efficient exploitation. Parent bodies of chondrites contain 70–100 ​ppm of Cu in bulk and this is mainly contained in Fe,Ni-alloy. However, parts of asteroids that were affected by shock processes and post-shock thermal annealing may host Cu that exsolved from primary alloy and forms native, pure-Cu grains. Up to 50 ​ppm of Cu may be present in such phase in these parts of asteroids. Grains of native copper can be extracted from the host rock via mechanical mineral processing methods, releasing need of extensive chemical leaching. This makes potential exploitation more targeted and less destructive for the local environment. A characteristic feature associated with enrichment in native Cu in chondrites is presence of shock-darkened zones. Therefore, we suggest that shock-darkened asteroids are potentially best sites for Cu exploitation

Assays to determine tolerance of cherry rootstock to bacterial canker caused by Pseudomonas syringae pv. syringae

Bacterial canker, caused by Pseudomonas syringae pv. syringae is recognized as one of the greatest limiting factors in cherry production in Oregon. Disease incidence may be decreased when susceptible cultivars are high-grafted onto tolerant/resistant rootstocks. This research was begun to develop a rapid screening method which could be used to test cherry rootstocks for tolerance to Pseudomonas syringae pv. syringae. In 1988, one-year-old wood of 'Napoleon', 'Corum' and F/12-1 was collected at monthly intervals from November until January. 'Napoleon' and 'Corum' are found to be susceptible, and F/12-1 to be tolerant to Pseudomonas syringae pv. syringae. Twigs were inoculated with water, one avirulent, and three virulent strains of bacteria at 10⁵, 10⁶, and 10⁷ cfu/ml. Browning, gummosis, and callus production were evaluated at the inoculation site after incubation for 4 weeks. Generally, browning and gummosis induced by concentrations of 10⁶ and 10⁷ cfu/ml across the virulent strains were not different. No gummosis and browning were observed on twigs inoculated with water or the avirulent strain. Callus production did not appear to be a usable criterion of the disease in this assay. 'Napoleon' and 'Corum' had significantly higher browning and gummosis ratings than F/12-1. In 1989, one-year-old twigs from 'Napoleon', 'Corum', and a number of cherry rootstocks were collected from October until December . The rootstocks included: F/12-1, M x M 2, M x M 39, M x M 60, GI 148-1, GI 148-8, GI 154-2, GI 154-5, GI 169-15, GI 172-9, and GI 173-9. Twigs were inoculated with water alone as a check, one avirulent and three virulent strains at 10⁷ cfu/ml. Incision browning, gummosis and callus production were evaluated after incubation for 4 weeks. Based on incision browning and gummosis all the rootstocks tested were more tolerant than 'Napoleon' and 'Corum', and most did not differ from F/12-1. However, rootstocks GI 172-9 and GI 169-15 showed more browning than F/12-1 in a number of instances. On the last sampling date, rootstocks M x M 2, GI 173-9, GI 148-8, and GI 154-2 showed less browning than F/12-1. The expression of virulence genes in P. syringae has been shown to be induced by plant signals extracted from cherry leaves. Crude aqueous extracts from 'Napoleon', 'Corum', and various cherry rootstock twigs were adjusted to a concentration of 0.2, 1.0, and 2.0 mg-ml⁻¹, and evaluated for the ability to induce virulence in Pseudomonas syringae pv. syringae. A decrease in activity was generally observed at the two highest concentrations of plant extracts. Reduced activity may have been due to inhibition of the assay or saturation of active sites of the enzyme produced by the bacteria. Compared to tolerant genotype F/12-1, 'Napoleon' and 'Corum' had the highest activity of all the genotypes tested. Rootstocks M x M 60, GI 148-1, GI 148-9, GI 154-5, and GI 169-15 had higher activity than F/12-1 in plant extracts of 0.2 mg-ml⁻¹. Activity induced in rootstocks MxM2, MxM39, GI 154-2, GI 172-9, and GI 173-9 was not different from that of F/12-1. The lowest activity observed was for 'Colt', however this activity was not statistically different from that induced by F/12-1

Identification and characterization of tetracycline resistance in Lactococcus lactis isolated from Polish raw milk and fermented artisanal products

To assess the occurrence of antibiotic-resistant Lactic Acid Bacteria (LAB) in Polish raw milk and fermented artisanal products, a collection comprising 500 isolates from these products was screened. Among these isolates, six strains (IBB28, IBB160, IBB161, IBB224, IBB477 and IBB487) resistant to tetracycline were identified. The strains showing atypical tetracycline resistance were classified as Lactococcus lactis: three of them were identified as L. lactis subsp. cremoris (IBB224, IBB477 and IBB487) and the other three (IBB28, IBB160, IBB161) were identified as L. lactis subsp. lactis. The mechanism involving Ribosomal Protection Proteins (RPP) was identified as responsible for tetracycline resistance. Three of the tested strains (IBB28, IBB160 and IBB224) had genes encoding the TetS protein, whereas the remaining three (IBB161, IBB477 and IBB487) expressed TetM. The results also demonstrated that the genes encoding these proteins were located on genetic mobile elements. The tet(S) gene was found to be located on plasmids, whereas tet(M) was found within the Tn916 transposon

Intra- and Interspecies Conjugal Transfer of Tn916-Like Elements from Lactococcus lactis In Vitro and In Vivo▿

Tetracycline-resistant Lactococcus lactis strains originally isolated from Polish raw milk were analyzed for the ability to transfer their antibiotic resistance genes in vitro, using filter mating experiments, and in vivo, using germfree rats. Four of six analyzed L. lactis isolates were able to transfer tetracycline resistance determinants in vitro to L. lactis Bu2-60, at frequencies ranging from 10−5 to 10−7 transconjugants per recipient. Three of these four strains could also transfer resistance in vitro to Enterococcus faecalis JH2-2, whereas no transfer to Bacillus subtilis YBE01, Pseudomonas putida KT2442, Agrobacterium tumefaciens UBAPF2, or Escherichia coli JE2571 was observed. Rats were initially inoculated with the recipient E. faecalis strain JH2-2, and after a week, the L. lactis IBB477 and IBB487 donor strains were introduced. The first transconjugants were detected in fecal samples 3 days after introduction of the donors. A subtherapeutic concentration of tetracycline did not have any significant effect on the number of transconjugants, but transconjugants were observed earlier in animals dosed with this antibiotic. Molecular analysis of in vivo transconjugants containing the tet(M) gene showed that this gene was identical to tet(M) localized on the conjugative transposon Tn916. Primer-specific PCR confirmed that the Tn916 transposon was complete in all analyzed transconjugants and donors. This is the first study showing in vivo transfer of a Tn916-like antibiotic resistance transposon from L. lactis to E. faecalis. These data suggest that in certain cases food lactococci might be involved in the spread of antibiotic resistance genes to other lactic acid bacteria