scholarly journals Tracing the Origins of Refractory Inclusions - the  Solar System's Oldest Solids: a Petrographic, Geochemical and 26Al-26Mg Dating Study of  CV and CK Refractory Inclusions

2021 ◽  
Author(s):  
◽  
Christopher Campbell Town
Keyword(s):  
Solar System ◽  
Thermal History ◽  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Chemical Fractionation ◽  
Initial Concentration ◽  
Isotopic Analyses ◽  
Isotope Analyses ◽  
Multiple Episodes

<p>Refractory inclusions in carbonaceous chondrite meteorites are of particular interest because both long- and short-lived chronometers have shown that they are the oldest sampled material to have formed in the Solar System. The objective of this study was to establish high-precision petrographic, chemical and isotopic analyses of refractory inclusions and thus offer insights into the chemical and astrophysical environments present during the formation of the Solar System. The former presence of the short-lived isotope 26Al (T1/2 = ca.730 KYr) has been established in a majority of refractory inclusions. Recent studies using both solution-based and in situ methodologies have suggested that the initial 26Al/27Al0 value of refractory inclusions is ca.6 x 10-5, higher than the established "canonical" value of [5.00 +/- 0.05] x 10-5. Knowing the initial concentration of 26Al within the Solar System provides a useful anchor from which ancient materials can be dated. Petrographic and trace element analyses were performed on nine newly-extracted refractory inclusions from CV3 and CK3 chondrites. These analyses revealed all but three refractory inclusions to have experienced multiple episodes of melting and evaporation prior to crystal closure. Mg isotope analyses were performed on eight of the newly extracted refractory inclusions in addition to five inter-laboratory samples. All refractory inclusions shown to have remained unaltered following crystal-closure, regardless of thermal history prior to closure, yielded a model 26Al/27Al0 of [4.89 x 0.265] x 10-5; within error of the canonical value. This result confirms that 26Al was homogenous and at canonical concentrations in the solar nebula. The results also suggest that chemical fractionation and crystal closure for the analysed refractory inclusions was completed within no more than 160 Kyr.</p>

scholarly journals Tracing the Origins of Refractory Inclusions - the  Solar System's Oldest Solids: a Petrographic, Geochemical and 26Al-26Mg Dating Study of  CV and CK Refractory Inclusions

2021 ◽  
Author(s):  
◽  
Christopher Campbell Town
Keyword(s):  
Solar System ◽  
Thermal History ◽  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Chemical Fractionation ◽  
Initial Concentration ◽  
Isotopic Analyses ◽  
Isotope Analyses ◽  
Multiple Episodes

<p>Refractory inclusions in carbonaceous chondrite meteorites are of particular interest because both long- and short-lived chronometers have shown that they are the oldest sampled material to have formed in the Solar System. The objective of this study was to establish high-precision petrographic, chemical and isotopic analyses of refractory inclusions and thus offer insights into the chemical and astrophysical environments present during the formation of the Solar System. The former presence of the short-lived isotope 26Al (T1/2 = ca.730 KYr) has been established in a majority of refractory inclusions. Recent studies using both solution-based and in situ methodologies have suggested that the initial 26Al/27Al0 value of refractory inclusions is ca.6 x 10-5, higher than the established "canonical" value of [5.00 +/- 0.05] x 10-5. Knowing the initial concentration of 26Al within the Solar System provides a useful anchor from which ancient materials can be dated. Petrographic and trace element analyses were performed on nine newly-extracted refractory inclusions from CV3 and CK3 chondrites. These analyses revealed all but three refractory inclusions to have experienced multiple episodes of melting and evaporation prior to crystal closure. Mg isotope analyses were performed on eight of the newly extracted refractory inclusions in addition to five inter-laboratory samples. All refractory inclusions shown to have remained unaltered following crystal-closure, regardless of thermal history prior to closure, yielded a model 26Al/27Al0 of [4.89 x 0.265] x 10-5; within error of the canonical value. This result confirms that 26Al was homogenous and at canonical concentrations in the solar nebula. The results also suggest that chemical fractionation and crystal closure for the analysed refractory inclusions was completed within no more than 160 Kyr.</p>

scholarly journals 1. The Origin of Comets

1977 ◽  
Vol 39 ◽  
pp. 453-467 ◽  
Author(s):  
A. H. Delsemme
Keyword(s):  
Solar System ◽  
Mass Loss ◽  
Empirical Evidence ◽  
Empirical Data ◽  
Solar Nebula ◽  
Giant Planets ◽  
Outer Ring ◽  
Arrow Of Time ◽  
Satisfactory Theory

Empirical data are confronted with different hypotheses on the origin of comets. The hypotheses are classified into three categories: 1) Comets were condensed from the solar nebula and ejected later into the Oort’s cloud. 2) Comets were condensed in situ, more or less recently, on their present trajectories; 3) Reversing the arrow of time in the traditional evolution of comets. Only two hypotheses, both from the first category, are found to be in agreement with all empirical data. The first hypothesis explains the origin of the Oort’s cloud by the perturbations of the giant planets (mainly Uranus and Neptune and possibly Pluto) on a ring of proto-comets, during the final accretion stages of the solar system. The second hypothesis uses the fast mass loss of the solar nebula to expell an outer ring of proto-comets into elliptic trajectories. Although no empirical evidence requests that the Oort’s cloud be older than a few million years, its matter is not likely to be from a different reservoir than solar system stuff, and no satisfactory theory explains its formation more recently than 4,5 billion years ago.

scholarly journals Heliocentric Zoning of the Asteroid Belt by Aluminum-26 Heating

Science ◽  
1993 ◽  
Vol 259 (5095) ◽  
pp. 653-655 ◽  
Author(s):  
Robert E. Grimm ◽  
Harry Y. McSween
Keyword(s):  
Thermal History ◽  
Solar Nebula ◽  
Planetary System ◽  
Asteroid Belt ◽  
The Sun ◽  
Initial Concentration ◽  
Decay Products ◽  
Spectral Class ◽  
Time Required ◽  
Electrical Induction

The dependence of asteroid spectral class (and inferred composition and thermal history) on heliocentric radius has been held to be the result of heating by a solar energy source, most likely electrical induction, during the formation of the planetary system. Such variations in thermal history can be more simply explained by the presence of different amounts of the radionuclide aluminum-26, whose decay products are observed in meteorites, in planetesimals. These differences occurred naturally as a function of the increasing amount of time required to aecrete objects farther from the sun, during which aluminum-26 decayed from its initial concentration in the solar nebula. Both theory and isotopic evidence suggest that increases in aecretion time across the asteroid belt are of order several half-lives of aluminum-26, which is sufficient to produce the inferred differences in thermal history.

scholarly journals 4. Oort’s Cometary Cloud in the Light of Modern Cosmogony

1977 ◽  
Vol 39 ◽  
pp. 483-484
Author(s):  
V. S. Safronov
Keyword(s):  
Solar System ◽  
Ad Hoc ◽  
Solar Nebula ◽  
Slow Growth ◽  
Large Mass ◽  
Giant Planets ◽  
Interstellar Grains ◽  
Small Density ◽  
Rule Out

Although the existence of Oort’s cometary cloud has been generally accepted, his hypothesis on its origin has been repeatedly called into question, in particular because of the large mass that Jupiter would also have simultaneously ejected out of the solar system. However, the extremely slow growth of particles in regions of small density seems to rule out that comets condensed “in situ” at their present large distances. Also, the accumulation of interstellar grains in satellite disks orbiting around the primitive solar nebula seems an “ad hoc” hypothesis that cannot be proved or disproved. Therefore, the most reasonable hypothesis is that comets were ejected from the region of the giant planets as a natural by-product of their accretion.

Laboratory and in-situ analysis of comet dust

1988 ◽  
Vol 46 ◽  
pp. 8-9
Author(s):  
D.E. Brownlee ◽  
A.L. Albee
Keyword(s):  
Electron Microscopy ◽  
Solar System ◽  
Laboratory Study ◽  
Isotopic Analysis ◽  
Building Blocks ◽  
Sem Analysis ◽  
Early Solar System ◽  
Cometary Material ◽  
Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

scholarly journals New from Old: Thorectandrin Alkaloids in a Southern Australian Marine Sponge, Thorectandra choanoides (CMB-01889)

Marine Drugs ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. 97
Author(s):  
Shamsunnahar Khushi ◽  
Angela A. Salim ◽  
Ahmed H. Elbanna ◽  
Laizuman Nahar ◽  
Robert J. Capon
Keyword(s):  
Marine Sponge ◽  
Tissue Specificity ◽  
Spectroscopic Analysis ◽  
Transformation Products ◽  
Chemical Fractionation ◽  
Cancer Tissue ◽  
Michael Acceptor ◽  
Michael Acceptors ◽  
Stable Ring

Thorectandra choanoides (CMB-01889) was prioritized as a source of promising new chemistry from a library of 960 southern Australian marine sponge extracts, using a global natural products social (GNPS) molecular networking approach. The sponge was collected at a depth of 45 m. Chemical fractionation followed by detailed spectroscopic analysis led to the discovery of a new tryptophan-derived alkaloid, thorectandrin A (1), with the GNPS cluster revealing a halo of related alkaloids 1a–1n. In considering biosynthetic origins, we propose that Thorectandrachoanoides (CMB-01889) produces four well-known alkaloids, 6-bromo-1′,8-dihydroaplysinopsin (2), 6-bromoaplysinopsin (3), aplysinopsin (4), and 1′,8-dihydroaplysinopsin (10), all of which are susceptible to processing by a putative indoleamine 2,3-dioxygenase-like (IDO) enzyme to 1a–1n. Where the 1′,8-dihydroalkaloids 2 and 10 are fully transformed to stable ring-opened thorectandrins 1 and 1a–1b, and 1h–1j, respectively, the conjugated precursors 3 and 4 are transformed to highly reactive Michael acceptors that during extraction and handling undergo complete transformation to artifacts 1c–1g, and 1k–1n, respectively. Knowledge of the susceptibility of aplysinopsins as substrates for IDOs, and the relative reactivity of Michael acceptor transformation products, informs our understanding of the pharmaceutical potential of this vintage marine pharmacophore. For example, the cancer tissue specificity of IDOs could be exploited for an immunotherapeutic response, with aplysinopsins transforming in situ to Michael acceptor thorectandrins, which covalently bind and inhibit the enzyme.

scholarly journals In Situ exploration of the giant planets

2021 ◽  
Author(s):  
O. Mousis ◽  
D. H. Atkinson ◽  
R. Ambrosi ◽  
S. Atreya ◽  
D. Banfield ◽  
...  
Keyword(s):  
Solar System ◽  
Giant Planets ◽  
Atmospheric Composition ◽  
Formation History ◽  
History Of ◽  
Composition Structure ◽  
Galileo Probe ◽  
Probe Measurements

AbstractRemote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our Solar System. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases’ abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune.

In situ Fe isotopic analyses of fourteen reference materials using a synthetic Cr standard for mass bias and isobaric interference corrections by femtosecond LA-MC-ICP-MS

2021 ◽  
Author(s):  
Lei Xu ◽  
Wen Zhang ◽  
Tao Luo ◽  
Jin-Hui Yang ◽  
Zhaochu Hu
Keyword(s):  
Reference Materials ◽  
Isotope Ratios ◽  
Isobaric Interference ◽  
Analytical Technique ◽  
Mass Bias ◽  
Icp Ms ◽  
Isotopic Analyses

High precise and accurate measurements of Fe isotope ratios for fourteen reference materials from the USGS, MPI-DING and CGSG were successfully carried out using a developed analytical technique by fs...

Uretero-Iliac artery fistula: a rare cause of haematuria

2020 ◽  
Vol 13 (9) ◽  
pp. e232189
Author(s):  
Natalia Hernandez ◽  
Bethany Desroches ◽  
Eric Peden ◽  
Raj Satkunasivam
Keyword(s):  
Iliac Artery ◽  
Percutaneous Nephrostomy ◽  
Arterial System ◽  
Endoscopic Evaluation ◽  
Stent Removal ◽  
Retrograde Pyelogram ◽  
History Of ◽  
Gross Haematuria ◽  
Multiple Episodes

A woman in her mid-forties with a history of cervical cancer requiring chemoradiation presented with bilateral ureteral strictures secondary to radiation therapy. The ureteral obstruction was initially relieved with bilateral percutaneous nephrostomy tubes, and subsequently, bilateral ureteral stents. Over the course of 8 months, she presented with multiple episodes of severe gross haematuria. This persisted even after stent removal and conversion back to percutaneous nephrostomy tubes. The initial evaluation, done with concern for an uretero-iliac artery fistula, which included bilateral retrograde pyelograms and CT angiography was non-diagnostic. Given continued haematuria, repeat endoscopic evaluation was undertaken; on retrograde pyelogram, brisk contrast was seen to pass into the arterial system, consistent with a left ureteroarterial fistula. The patient underwent endovascular iliac artery stent placement. Subsequently, the patient underwent resection of the iliac artery with endovascular graft in situ, left distal ureterectomy with proximal ureteral ligation following femoral-to-femoral bypass. This allowed for complete resolution of the patient’s gross haematuria episodes.

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