Impact Induced Atmosphere-Mantle Exchange Sets the Volatile Elemental Ratios on Primitive Earths

Abstract

Conventional planet formation theory suggests that chondritic materials have delivered crucial atmospheric and hydrospheric elements such as carbon (C), nitrogen (N), and hydrogen (H) onto primitive Earth. However, recent measurements highlight the significant elemental ratio discrepancies between terrestrial parent bodies and the supposed planet building blocks. Here we present a volatile evolution model during the assembly of Earth and Earth-like planets. Our model includes impact losses, atmosphere-mantle exchange, and time dependent effects of accretion and outgassing calculated from dynamical modeling outcomes. Exploring a wide range of planetesimal properties (i.e., size and composition) as well as impact history informed by N-body accretion simulations, we find that while the degree of CNH fractionation has inherent stochasticity, the evolution of C/N and C/H ratios can be traced back to certain properties of the protoplanet and projectiles. Interestingly, the majority of our Earth-like planets acquire superchondritic final C/N ratios, implying that the volatile elemental ratios on terrestrial planets are driven by the complex interplay between delivery, atmospheric ablation, and mantle degassing.

24 pages, 10 figures, 3 tables; accepted to Earth and Planetary Science Letters

References in corpus (15)

• The origins and concentrations of water, carbon, nitrogen and noble gases on Earth
• Water Delivery and Giant Impacts in the 'Grand Tack' Scenario
• Highly Siderophile Elements in the Earth's Mantle as a Clock for the Moon-forming Impact
• The Nitrogen Budget of Earth
• Atmospheric Mass Loss During Planet Formation: The Importance of Planetesimal Impacts
• Evidence for multiple magma ocean outgassing and atmospheric loss episodes from mantle noble gases
• Oxygen fugacities of extrasolar rocks: Evidence for an Earth-like geochemistry of exoplanets
• Lunar and Terrestrial Planet Formation in the Grand Tack Scenario
• Outward migration of Jupiter and Saturn in 3:2 or 2:1 resonance in radiative disks: implications for the Grand Tack and Nice models
• Early volatile depletion on planetesimals inferred from C-S systematics of iron meteorite parent bodies
• The dehydration of water worlds via atmospheric losses
• Numerous chondritic impactors and oxidized magma ocean set Earth's volatile depletion
• The Flaring TESS Objects of Interest: Flare Rates for all Two Minute Cadence TESS Planet Candidates
• Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection
• The impact of AGN outflows on the surface habitability of terrestrial planets in the Milky Way

Cited by in corpus (4)

• Distinguishing oceans of water from magma on mini-Neptune K2-18b
• The erosion of large primary atmospheres typically leaves behind substantial secondary atmospheres on temperate rocky planets
• Sporadic Spin-Orbit Variations in Compact Multi-planet Systems and their Influence on Exoplanet Climate
• Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems