Measuring The Atomic Composition Of Planetary Building Blocks


(A) Dominant locking locations for C, N, and O, relative to innermost dust radius (0.3 AU) (26), water ice snowline (4 AU)(27), CO snowline (14), and theoretical N2 snowline. (B) Cartoon of observed disk structures. Millimeter grains (maroon fill, ALMA) (24), small grains (purple fill, SPHERE) (25), and CO gas (mustard fill) (28, 29). (C) Visualization of the analytic locking model zones. C/H depletion factors and fraction locked or accreted are indicated, for a refractory fraction of 97.4%.

Volatile molecules are critical to habitability, yet difficult to observe directly at the optically thick midplanes of protoplanetary disks, where planets form.

We present a new technique to measure indirectly the bulk atomic composition and distribution of solids that have been removed from the gas accreting onto the young star TW Hydrae. Our results suggest that disk gaps and planetesimal formation in TW Hya efficiently prevent radial drift and effectively block replenishment of the inner disk solids from ice reservoirs.

Volatile-enhancement of giant planet atmospheres cannot be explained by primary accretion of this gas. Half of the missing oxygen is locked in silicates inside the snowline, while carbon is predominantly locked in organics beyond the CO snowline, leaving terrestrial planet-forming region solids both 'dry' and carbon-poor. Earth's depletion of carbon could be common amongst terrestrial exoplanets.

M. K. McClure, C. Dominik
(Submitted on 16 Oct 2019)

Comments: Main text (~2500 words, 3 figures, 1 table) & supplemental text (~2500 words, 4 figures, 2 tables), under review at a journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1910.07345 [astro-ph.EP] (or arXiv:1910.07345v1 [astro-ph.EP] for this version)
Submission history
From: Melissa McClure
[v1] Wed, 16 Oct 2019 13:47:26 UTC (784 KB)
https://arxiv.org/abs/1910.07345
Astrobiology, Astrochemistry

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