![Computed abundance maps of ammonium cyanate, ammonium formate, ammonium acetate, ammonium hydrosulfide and ammonium carbamate in the solid phase for r < 50 au and computed after 1 Myr and 10 Myrs. We also show the ratio of the vertically integrated abundances of these salts relative to water ice. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Ammonium-salt-.png?fit=1200%2C674&ssl=1)
[astro-ph.EP] Ammonium salts may represent an important reservoir of volatile species in Solar system primitive bodies, but the question of how and when these salts can form during the star formation process remains unknown.
In this paper, we use thermo-chemical models to study the formation of ammonium salts during the protoplanetary disk stage. We show that ammonium salts form efficiently in the inner disk midplane (i.e. r≲50 au), inside the comet forming region.
In this region, our model predicts that almost all the available nitrogen is in the form of salts (i.e. mainly in ammonium cyanate) at the surface of grains after evolving for 10 Myrs. For sulfur, we show that almost all the available S is in the form of ammonium hydrosulfide in the inner disk midplane.
We show that inside r∼30 au, ammonium salt formation is enhanced by a cosmic-ray-driven sink effect that progressively converts gas-phase CO and N2 into carbon dioxide and salts, respectively, at the surface of grains on a timescale ≳1 Myr. This impacts the location of the CO and N2 radial snowlines which both shift closer to the star as a function of time.
Maxime Ruaud, Jean-Christophe Loison, Uma Gorti
Comments: 12 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2608.02173 [astro-ph.EP] (or arXiv:2608.02173v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2608.02173
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Submission history
From: Maxime Ruaud
[v1] Mon, 3 Aug 2026 12:53:01 UTC (912 KB)
https://arxiv.org/abs/2608.02173
Astrobiology
