arXiv subjects

Emily A. Pringle

Publications and source records attributed to Emily A. Pringle.

5 recordsLinked to original sources

arXiv2017

A history of violence: insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes, and water contents

Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provide vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomitantly, during post-accretionary shock impact(s).

astro-ph.EP↗

arXiv2017

Early formation of planetary building blocks inferred from Pb isotopic ages of chondrules

The most abundant components of primitive meteorites (chondrites) are millimeter-sized glassy spherical chondrules formed by transient melting events in the solar protoplanetary disk. Using Pb-Pb dates of 22 individual chondrules, we show that primary production of chondrules in the early solar system was restricted to the first million years after formation of the Sun and that these existing chondrules were recycled for the remaining lifetime of the protoplanetary disk. This is consistent with a primary chondrule formation episode during the early high-mass accretion phase of the protoplanetary disk that transitions into a longer period of chondrule reworking. An abundance of chondrules at early times provides the precursor material required to drive the efficient and rapid formation of planetary objects via chondrule accretion.

astro-ph.EP↗

arXiv2017

Testing the chondrule-rich accretion model for planetary embryos using calcium isotopes

Understanding the composition of raw materials that formed the Earth is a crucial step towards understanding the formation of terrestrial planets and their bulk composition. Calcium is the fifth most abundant element in terrestrial planets and, therefore, is a key element with which to trace planetary composition. However, in order to use Ca isotopes as a tracer of Earth's accretion history, it is first necessary to understand the isotopic behavior of Ca during the earliest stages of planetary formation. Chondrites are some of the oldest materials of the Solar System, and the study of their isotopic composition enables understanding of how and in what conditions the Solar System formed. Here we present Ca isotope data for a suite of bulk chondrites as well as Allende (CV) chondrules. We show that most groups of carbonaceous chondrites (CV, CI, CR and CM) are significantly enriched in the lighter Ca isotopes ($δ^{44/40}Ca$ = +0.1 to +0.93 permill) compared with bulk silicate Earth ($δ^{44/40}Ca$ = +1.05 $\pm$ 0.04 permill, Huang et al., 2010) or Mars, while enstatite chondrites are indistinguishable from Earth in Ca isotope composition ($δ^{44/40}Ca$ = +0.91 to +1.06 permill). Chondrules from Allende are enriched in the heavier isotopes of Ca compared to the bulk and the matrix of the meteorite ($δ^{44/40}Ca$ = +1.00 to +1.21 permill). This implies that Earth and Mars have Ca isotope compositions that are distinct from most carbonaceous chondrites but that may be like chondrules. This Ca isotopic similarity between Earth, Mars, and chondrules is permissive of recent dynamical models of planetary formation that propose a chondrule-rich accretion model for planetary embryos.

astro-ph.EP↗

arXiv2016

Silicon isotopes reveal recycled altered oceanic crust in the mantle sources of Ocean Island Basalts

The study of silicon (Si) isotopes in ocean island basalts (OIB) has the potential to discern between different models for the origins of geochemical heterogeneities in the mantle. Relatively large (several per mil per atomic mass unit) Si isotope fractionation occurs in low-temperature environments during biochemical and geochemical precipitation of dissolved Si, where the precipitate is preferentially enriched in the lighter isotopes relative to the dissolved Si. In contrast, only a limited range (tenths of a per mil) of Si isotope fractionation has been observed from high-temperature igneous processes. Therefore, Si isotopes may be useful as tracers for the presence of crustal material within OIB mantle source regions that experienced relatively low-temperature surface processes in a manner similar to other stable isotope systems, such as oxygen. Characterizing the isotopic composition of the mantle is also of central importance to the use of the Si isotope system as a basis for comparisons with other planetary bodies (e.g., Moon, Mars, asteroids). Here we present the first comprehensive suite of high-precision Si isotope data obtained by MC-ICP-MS for a diverse suite of OIB. Samples originate from ocean islands in the Pacific, Atlantic, and Indian Ocean basins and include representative end-members for the EM-1, EM-2, and HIMU mantle components. On average, Si isotope compositions of OIB are in general agreement with previous estimates for the Si isotope composition of bulk silicate Earth. Nonetheless, some small systematic variations are present; specifically, most HIMU-type (Mangaia; Cape Verde; La Palma, Canary Islands) and Iceland OIB are enriched in the lighter isotopes of Si, consistent with recycled altered oceanic crust and lithospheric mantle in their mantle sources.

astro-ph.EP↗

arXiv2013

Interstellar dust properties of M51 from AKARI mid-infrared images

Using mid-infrared (MIR) images of four photometric bands of the Infrared Camera (IRC) onboard the AKARI satellite, S7 (7 um), S11 (11 um), L15 (15 um), and L24 (24 um), we investigate the interstellar dust properties of the nearby pair of galaxies M51 with respect to its spiral arm structure. The arm and interarm regions being defined based on a spatially filtered stellar component model image, we measure the arm-to-interarm contrast for each band. The contrast is lowest in the S11 image, which is interpreted as that among the four AKARI MIR bands the S11 image best correlates with the spatial distribution of dust grains including colder components, while the L24 image with the highest contrast traces warmer dust heated by star forming activities. The surface brightness ratio between the bands, i.e. color, is measured over the disk of the main galaxy, M51a, at 300 pc resolution. We find that the distribution of S7/S11 is smooth and well traces the global spiral arm pattern while L15/S11 and L24/S11 peak at individual HII regions. This result indicates that the ionization state of PAHs is related to the spiral structure. Comparison with observational data and dust models also supports the importance of the variation in the PAH ionization state within the M51a disk. However, the mechanism driving this variation is not yet clear from currently available data sets. Another suggestion from the comparison with the models is that the PAH fraction to the total dust mass is higher than previously estimated.

astro-ph.CO↗