Evaluation of the heat, entropy, and rotational changes produced by gravitational segregation during core formation

Core formation should have stripped the terrestrial, lunar, and martian mantles of highly siderophile elements (HSEs). Instead, each world has disparate, yet elevated HSE abundances. Late accretion may offer a solution, provided that ≥0.5% Earth masses of broadly chondritic planetesimals reach Earth’s mantle and that ~10 and ~1200 times less mass goes to Mars and the Moon, respectively. We show that leftover planetesimal populations dominated by massive projectiles can explain these additions, with our inferred size distribution matching those derived from the inner asteroid belt, ancient martian impact basins, and planetary accretion models. The largest late terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially modified Earth’s obliquity by ~10°, whereas those for the Moon, at ~250 to 300 kilometers, may have delivered water to its mantle.

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Core formation in asteroids

Journal of Geophysical Research Atmospheres ◽

10.1029/92je01501 ◽

1992 ◽

Vol 97 (E9) ◽

pp. 14717 ◽

Cited By ~ 72

Author(s):

G. Jeffrey Taylor

Keyword(s):

Core Formation

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HID-1 controls formation of large dense core vesicles by influencing cargo sorting and trans-Golgi network acidification

Molecular Biology of the Cell ◽

10.1091/mbc.e17-08-0491 ◽

2017 ◽

Vol 28 (26) ◽

pp. 3870-3880 ◽

Cited By ~ 14

Author(s):

Blake H. Hummer ◽

Noah F. de Leeuw ◽

Christian Burns ◽

Lan Chen ◽

Matthew S. Joens ◽

...

Keyword(s):

Biochemical Properties ◽

Neuroendocrine Cells ◽

Dense Core ◽

Core Formation ◽

Dense Core Vesicles ◽

Atpase Subunit ◽

Trans Golgi Network ◽

Large Dense Core Vesicles ◽

Golgi Network ◽

Cargo Sorting

Large dense core vesicles (LDCVs) mediate the regulated release of neuropeptides and peptide hormones. They form at the trans-Golgi network (TGN), where their soluble content aggregates to form a dense core, but the mechanisms controlling biogenesis are still not completely understood. Recent studies have implicated the peripheral membrane protein HID-1 in neuropeptide sorting and insulin secretion. Using CRISPR/Cas9, we generated HID-1 KO rat neuroendocrine cells, and we show that the absence of HID-1 results in specific defects in peptide hormone and monoamine storage and regulated secretion. Loss of HID-1 causes a reduction in the number of LDCVs and affects their morphology and biochemical properties, due to impaired cargo sorting and dense core formation. HID-1 KO cells also exhibit defects in TGN acidification together with mislocalization of the Golgi-enriched vacuolar H+-ATPase subunit isoform a2. We propose that HID-1 influences early steps in LDCV formation by controlling dense core formation at the TGN.

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