Actinomadura soli sp. nov., isolated from the top soil layer on basaltic material in Turkey

An actinobacterium, designated 14C53T, was isolated from a soil sample on basaltic material from Samsun, Turkey. The growth ranges for NaCl concentration and pH of strain 14C53T were quite limited and the growth temperature range of the strain was 20–37 °C, with an optimum at 28 °C. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain 14C53T was most closely related to Actinomadura geliboluensis A8036T (98.5 % similarity value), but in the phylogenetic tree, it formed a clade with Actinomadura alkaliterrae D310AT. The genome tree revealed a close relationship between the strain and Actinomadura pelletieri DSM 43383T. However, the digital DNA–DNA hybridization and average nucleotide identity values between strain 14C53T with Actinomadura geliboluensis A8036T and Actinomadura pelletieri DSM 43383T were 28.6–30.2 % and 84.3–85.5 %, respectively, and comparative analyses based on the genome sequences demonstrated that it represents a novel species of the genus Actinomadura . The genome size of strain 14C53T was approximately 9.0 Mb and the genomic DNA G+C content of the strain was 71.3 mol%. The major cellular fatty acids of strain 14C53T were C16 : 0 and iso-C16 : 0. Strain 14C53T contained meso-diaminopimelic acid as the diamino acid in the cell-wall peptidoglycan. The predominant menaquinones were MK-9(H8) and MK-9(H6). Based on evidence collected from the phenotypic, genotypic and phylogenetic analyses, a novel species Actinomadura soli sp. nov. is proposed, with 14C53T (=DSM 104447T=KCTC 39878T) as the type strain.

Search for Candidate Exogenous Material on Bennu using MapCam and PolyCam Images

<p><strong>Introduction:</strong> Exogenous material has been reported on asteroids (101955) Bennu and (162173) Ryugu.  The albedo, color, and spectra of six bright boulders on Bennu show that they are distinct from the rest of Bennu’s comparatively dark surface and are likely basaltic material from asteroid (4) Vesta (DellaGiustina et al. 2019; 2020).  Bright boulders identified on asteroid (162173) Ryugu show absorptions near 1 µm but not near 2 µm, suggesting olivine-rich anhydrous silicates (Tatsumi et al., 2019; 2020).</p><p><strong>Methods: </strong>In this work, we used images of Bennu obtained by the MapCam and PolyCam instruments (Rizk et al. 2018; Golish et al. 2020) on NASA’s OSIRIS-REx spacecraft (Lauretta et al. 2017) to search for more potentially exogeneous material on the surface of Bennu.  </p><p><strong>Results: </strong>We identified approximately 50 bright boulders on Bennu with significant x-band (0.85 µm) absorptions, including the six bright boulders previously described in DellaGiustina et al. (2020).  These bright boulders are distributed across Bennu’s surface, concentrated in terrains with larger than average particle size.  The boulders exhibit three main morphologies (homogeneous, heterogenous, and breccia) and three spectral types (reflectance peak at 0.55 µm, flat, and reflectance peak at 0.7 µm). There is some correlation between the morphology and the spectra. More specifically, three of the four boulders with reflectance peaks at 0.55 µm are in the breccia category and one is in the heterogeneous category, whereas all the boulders with reflectance peaking at 0.7 µm fall in the homogeneous and heterogenous categories. Bright boulders with reflectance peaking at 0.55 µm have lower normal albedo than the other two spectral groups, suggesting a different composition and possibly a different origin. An initial comparison with Ryugu (Tatsumi et al. 2019) indicates that Bennu is more abundant in possible exogeneous material.  </p><p><strong>Discussion: </strong>Further analysis of MapCam and PolyCam images has revealed a wider diversity of potentially exogenous lithologies on Bennu, expanding on the findings of DellaGiustina et al. (2020).  We continue our study of this diversity of material on Bennu’s surface to constrain the asteroid’s origin, evolution, and collisional history (e.g., Ballouz et al. 2020).</p><p><strong>References: </strong>DellaGiustina D. et al. (2019) Nat. Astron. 3, 341-351. DellaGiustina D. et al. (2020) Nat. Astron, in revision. Lauretta D. S. et al. (2017) Space Sci. Rev. 212, 925–984. Tatsumi E. et al. (2019) LPI Contribution No. 2132, id.1753. Rizk B. et al. (2018) Space Sci. Rev. 214, 26. Golish D.R. et al. (2020) Space Sci. Rev. 216, 12. Ballouz R.-L. et al. 2020, EPSC abstract.</p>

Distribution and spectrophotometric classification of basaltic asteroids

ABSTRACT We aim to determine the distribution of basaltic asteroids (classified as V-types) based on the spectrophotometric data reported in the MOVIS-C catalogue. A total of 782 asteroids were identified. The observations with all four filters (Y, J, H, Ks), available for 297 of these candidates, allow a reliable comparison with the laboratory data of howardite, eucrite, and diogenite meteorites. We found that the majority of the basaltic candidates (≈95${{\ \rm per\ cent}}$) are located in the inner main belt, while only 29 (≈4${{\ \rm per\ cent}}$) and 8 (≈1${{\ \rm per\ cent}}$) are located in the middle (MMB) and outer main belt (OMB), respectively. A fraction of ≈33${{\ \rm per\ cent}}$ from the V-type candidates is associated with the Vesta family (with respect to AstDyS). We also identified four MMB V-type candidates belonging to (15) Eunomia family, and another four low inclination ones corresponding to (135) Hertha. We report differences between the colour indices and albedo distributions of the V-type candidates located in the inner main belt compared to those from the MMB and OMB. These results support the hypothesis of a different origin for the basaltic asteroids with a semimajor axis beyond 2.5 au. Furthermore, lithological differences are present between the vestoids and the inner low inclination basaltic asteroids. The data allow us to estimate the unbiased distribution of basaltic asteroids across the main asteroid belt. We highlight that at least 80${{\ \rm per\ cent}}$ of the ejected basaltic material from (4) Vesta is missing or is not yet detected because it is fragmented in sizes smaller than 1 km.

Fitzroy River Basin, Queensland, Australia. III. Identification of sediment sources in the coastal zone

Environmental context. The Fitzroy River Basin is a major source of suspended sediment and nutrients to the southern Great Barrier Reef lagoon. A reduction in sediment and nutrient loads is necessary to protect coastal reefs and this requires an understanding of the sediment sources. The present geochemical and modelling study provides a quantitative estimate of the spatial and temporal variations in the sources of sediment deposited in the Fitzroy River coastal zone. Abstract. Sediment sources to the Fitzroy River coastal zone have been identified and quantified using an integrated geochemical and modelling approach. The coastal sediments display little geochemical variation as a result of substantial homogenisation during hydrodynamic processes and indicate a sediment composition consistent with derivation from mixed catchment sources. A lack of substantial temporal geochemical variation in the sediment records indicates weathering regimes and hydrodynamic transport have been relatively consistent throughout the Holocene. Despite this apparent geochemical homogeneity, a modelling approach using a Bayesian statistical model revealed changes in catchment sediment sources over time. Variations in the occurrence and intensity of rainfall events in different parts of the catchment as well as land-use changes following European settlement are likely to have had a substantial effect on the relative contributions of the catchment sources delivered to and deposited in the coastal zone. Additionally, large variations in flow events and variable estuary hydrodynamics result in different catchment soil types being delivered and deposited under different conditions. The present study found that basaltic material is the dominant catchment source in the coastal surface sediments with an estimated enrichment of ~3 relative to catchment and estuary abundances. Basaltic soils present as a more recent and extensive, weathered surficial cover are more readily mobilised than other catchment soils and will be transported further within freshwater flood plumes. It is likely that in large flood events, this basaltic material may reach the coral-dominated outer shelf. Improved land management practices to reduce sediment loads can be targeted to the areas supplying the majority of sediment to the coastal zone.

The Emergence of the Diversity of Igneous Rocks As A Geological Problem: Part One—Early Speculations

Speculation about igneous rock diversity began in the first half of the nineteenth century after acceptance of the existence of ancient volcanism and the recognition of two fundamental types of lava: basalt and trachyte. Before 1850, George Poulett Scrope (1797-1876), Charles Darwin (1809-1882), and James Dwight Dana (1813-1895) attributed diversity to intumescence of gas-rich lava, crystal settling, and differential fusion of minerals. In the 1850s, Robert Bunsen (1811-1899) maintained that lava is derived from two deep normal trachytic and normal pyroxenic sources. Wolfgang Sartorius von Waltershausen (1809-1876), Joseph Durocher (1817-1860), and Ferdinand von Richthofen (1833-1905) universalized Bunsen's sources by postulating a density-stratified Earth in which a layer of acid, feldspathic material rested above a layer of basic, basaltic material. Exploration of the complex volcanic terranes of western America in the 1860s and 1870s undermined the two-source theories and opened the way for the concept of fusion of already solid crust. Prior to 1880, speculations about diversity were typically suggested by naturalists, chemists, and geological generalists with strong interests in the geomorphic or geophysical aspects of Earth. Consequently, the problem of diversity was a peripheral concern to most of those proposing hypotheses. The hypotheses characteristically reflected the professional interests of their proposers. The content of the early speculations was further shaped by the nature of the field areas studied by proposers, and by their views on the correlation between geologic age and igneous rock type. Those, like Scrope, Darwin, Dana, Joseph Jukes (1811-1869), Carl Bernhard von Cotta (1808-1870), and Clarence Dutton (1841-1912), who rejected such correlations, located the source of igneous rock diversity at the surface, within a volcano, or within the acid crust. Those, like Bunsen, von Waltershausen, Durocher, von Richthofen, and Clarence King (1842-1901), who accepted the Wernerian idea that there had been changes in igneous rock type through time were more inclined to attribute diversity to multiple lava sources at great depth.

Microscopic planar features in quartz from Scollard Canyon, Alberta, and the Cretaceous–Tertiary boundary event

Quartz grains separated from the Cretaceous–Tertiary (K/T) boundary clay at Scollard Canyon, Alberta, have prominent, microscopic planar features. These occur in 15–30% of the grains from the lower 1.5 cm of the boundary clay. They commonly correspond to the ω and π orientations found at known meteorite impact sites and differ from deformation features produced by other dynamic geologic processes. Basal planar features, however, are absent here and at other K/T sites. One possible explanation is that quartz at boundary sites is an incomplete sample of shocked quartz from the postulated K/T impact and unshocked detrital quartz. The source of the shocked quartz most likely was close to the point of impact and near surface. This and previous isotopic data suggest the K/T target site contained a relatively thin upper unit of quartz-bearing crystalline rocks overlying basaltic material, corresponding possibly to thinned continent or a continental margin.