The relative influence of H<sub>2</sub>O and CO<sub>2</sub> on the primitive surface conditions and evolution of rocky planets

Salvador, Arnaud; Massol, Hélène; Davaille, Anne; Marcq, Emmanuel; Sarda, Philippe; Chassefière, Éric

doi:10.1002/2017je005286

Cited by 93 publications

(179 citation statements)

References 103 publications

Supporting

Mentioning

174

Contrasting

Order By: Relevance

“…Despite its importance to planetary evolution, the fO2 at the magma ocean-atmosphere interface is not well-constrained. There are two end-members: (1) in analogy with the modern Earth mantle, the magma ocean-primordial atmosphere system may be chemically oxidized (logfO2≈QFM), with water vapor and carbon dioxide dominant (Abe and Matsui, 1988;Kasting, 1988;Lebrun et al, 2013;Salvador et al, 2017).…”

Section: Primordial Atmospheric Compositionsmentioning

confidence: 99%

Hydrogen isotopic evidence for early oxidation of silicate Earth

Pahlevan¹,

Schaefer²,

Hirschmann³

2019

Preprint

View full text Add to dashboard Cite

The Moon-forming giant impact extensively melts and partially vaporizes the silicate Earth and delivers a substantial mass of metal to Earth's core. The subsequent evolution of the magma ocean and overlying atmosphere has been described by theoretical models but observable constraints on this epoch have proved elusive. Here, we report thermodynamic and climate calculations of the primordial atmosphere during the magma ocean and water ocean epochs respectively and forge new links with observations to gain insight into the behavior of volatiles on the Hadean Earth. As accretion wanes, Earth's magma ocean crystallizes, outgassing the bulk of its volatiles into the primordial atmosphere. The redox state of the magma ocean controls both the chemical composition of the outgassed volatiles and the hydrogen isotopic composition of water oceans that remain after hydrogen escape from the primordial atmosphere. The climate modeling indicates that multi-bar H2-rich atmospheres generate sufficient greenhouse warming and rapid kinetics resulting in ocean-atmosphere H2O-H2 isotopic equilibration. Whereas water condenses and is mostly retained, molecular hydrogen does not condense and can escape, allowing large quantities (~10 2 bars) of hydrogen -if present -to be lost from the Earth in this epoch. Because the escaping inventory of H can be comparable to the hydrogen inventory in primordial water oceans, equilibrium deuterium enrichment can be large with a magnitude that depends on the initial atmospheric H2 inventory. Under equilibrium partitioning, the water molecule concentrates deuterium and, to the extent that hydrogen in other forms (e.g., H2) are significant species in the outgassed atmosphere, pronounced D/H enrichments (~1.5-2x) in the oceans are expected from equilibrium partitioning in this epoch. By contrast, the common view that terrestrial water has a carbonaceous chondritic source requires the oceans to preserve the isotopic composition of that source, undergoing minimal D-enrichment via equilibration with H2 followed by hydrodynamic escape. Such minimal enrichment places upper limits on the amount of primordial atmospheric H2 in contact with Hadean water oceans and implies oxidizing conditions (logfO2>IW+1, H2/H2O<0.3) for outgassing from the magma ocean.Preservation of an approximate carbonaceous chondrite D/H signature in the oceans thus provides evidence that the observed oxidation of silicate Earth occurred before crystallization of the final magma ocean, yielding a new constraint on the timing of this critical event in Earth history. The seawater-carbonaceous chondrite "match" in D/H (to ~10-20%) further constrains the prior existence of an atmospheric H2 inventory -of any origin -on post-giant-impact Earth to <20 bars, and suggests that the terrestrial mantle supplied the oxidant for the chemical resorption of metals during terrestrial late accretion.

show abstract

Section: Primordial Atmospheric Compositionsmentioning

confidence: 99%

Hydrogen isotopic evidence for early oxidation of silicate Earth

Pahlevan¹,

Schaefer²,

Hirschmann³

2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Large collisions, in combination with heating by short-lived radioisotopes and differentiation, can lead to local or even global magma oceans. Existing water is either vaporized into a steam atmosphere, or gradually outgassed during magma ocean solidification, after which it is susceptible to atmospheric loss processes and impact erosion (Schlichting et al 2015; proximately Earth-sized planets (Hamano et al 2013;Lebrun et al 2013;Salvador et al 2017) suggest that beyond a critical distance (∼ 0.7 au in the Solar System) rapid magma ocean solidification within a few Myr and subsequent water ocean formation are possible. Smaller bodies can experience considerable volatile losses also farther from the star before re-condensation (Odert et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Realistic collisional water transport during terrestrial planet formation

Burger

Bazsó

Schäfer

2020

A&A

View full text Add to dashboard Cite

Context. According to the latest theoretical and isotopic evidence, Earth's water content originates mainly from today's asteroid belt region, or at least from the same precursor material. This suggests that water was transported inwards to Earth, and to similar planets in their habitable zone, via (giant) collisions of planetary embryos and planetesimals during the chaotic final phase of planet formation. Aims. In current dynamical simulations water delivery to terrestrial planets is still studied almost exclusively by assuming oversimplified perfect merging, even though water and other volatiles are particularly prone to collisional transfer and loss. To close this gap we have developed a computational framework to model collisional water transport by direct combination of long-term N-body computations with dedicated 3D smooth particle hydrodynamics (SPH) collision simulations of differentiated, self-gravitating bodies for each event.Methods. Post-collision water inventories are traced self-consistently in the further dynamical evolution, in accretionary or erosive as well as hit-and-run encounters with two large surviving bodies, where besides collisional losses, water transfer between the encountering bodies has to be considered. This hybrid approach enables us for the first time to trace the full dynamical and collisional evolution of a system of approximately 200 bodies throughout the whole late-stage accretion phase (several hundred Myr). As a first application we choose a Solar System-like architecture with already formed giant planets on either circular or eccentric orbits and a debris disk spanning the whole terrestrial planet region (0.5 -4 au).Results. Including realistic collision treatment leads to considerably different results than simple perfect merging, with lower mass planets and water inventories reduced regularly by a factor of two or more. Due to a combination of collisional losses and a considerably lengthened accretion phase, final water content, especially with giant planets on circular orbits, is strongly reduced to more Earth-like values, and closer to results with eccentric giant planets. Water delivery to potentially habitable planets is dominated by very few decisive collisions, mostly with embryo-sized or larger objects and only rarely with smaller bodies, at least if embryos have formed throughout the whole disk initially. The high frequency of hit-and-run collisions and the differences to predominantly accretionary encounters, such as generally low water (and mass) transfer efficiencies, are a crucial part of water delivery, and of system-wide evolution in general.

show abstract

“…Several previous magma ocean studies (e.g. Elkins-Tanton 2008; Lebrun et al 2013;Salvador et al 2017;Nikolaou et al 2019) do not appear to use the correct expression for the relationship between the partial pressure of a given volatile and its mass in the atmosphere (Eq. 2).…”

Section: Mass-partial Pressure Relationshipmentioning

confidence: 99%

“…However, the crucial difference is that whilst both studies use the same H 2 O absorption coefficient of 10 −2 m 2 /kg, we use a CO 2 absorption coefficient of 5 × 10 −2 m 2 /kg (i.e. larger than the H 2 O value) whereas Salvador et al (2017) use 10 −4 m 2 /kg (i.e. smaller than the H 2 O value).…”

Section: Outgassing Volatilesmentioning

confidence: 99%

“…Once H 2 O begins to outgas it dilutes the CO 2 in the atmosphere and drives the effective absorption coefficient of the multi-species atmosphere towards the value of the H 2 O absorption coefficient. For Salvador et al (2017), this means that the case with low initial CO 2 abundance is strongly diluted by H 2 O and hence cooling then proceeds slower due to the influence of the relatively large H 2 O absorption coefficient. This is compared to the case with high initial CO 2 abundance that is diluted less by H 2 O and hence retains an effective absorption coefficient that is closer to the value for pure CO 2 .…”

Section: Outgassing Volatilesmentioning

confidence: 99%

See 1 more Smart Citation

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Bower¹,

Kitzmann²,

Wolf³

et al. 2019

Preprint

View full text Add to dashboard Cite

Context.A terrestrial planet is molten during formation and may remain molten due to intense insolation or tidal forces. Observations favour the detection and characterisation of hot planets, potentially with large outgassed atmospheres. Aims. We aim to determine the radius of hot Earth-like planets with large outgassing atmospheres. Our goal is to explore the differences between molten and solid silicate planets on the mass-radius relationship and transmission and emission spectra.Methods. An interior-atmosphere model was combined with static structure calculations to track the evolving radius of a hot rocky planet that outgasses CO 2 and H 2 O. We generated synthetic emission and transmission spectra for CO 2 and H 2 O dominated atmospheres. Results. Atmospheres dominated by CO 2 suppress the outgassing of H 2 O to a greater extent than previously realised since previous studies applied an erroneous relationship between volatile mass and partial pressure. We therefore predict that more H 2 O can be retained by the interior during the later stages of magma ocean crystallisation. Formation of a surface lid can tie the outgassing of H 2 O to the efficiency of heat transport through the lid, rather than the radiative timescale of the atmosphere. Contraction of the mantle, as it cools from molten to solid, reduces the radius by around 5%, which can partly be offset by the addition of a relatively light species (e.g. H 2 O versus CO 2 ) to the atmosphere. Conclusions. A molten silicate mantle can increase the radius of a terrestrial planet by around 5% compared to its solid counterpart, or equivalently account for a 13% decrease in bulk density. An outgassing atmosphere can perturb the total radius, according to its composition, notably the abundance of light versus heavy volatile species. Atmospheres of terrestrial planets around M-stars that are dominated by CO 2 or H 2 O can be distinguished by observing facilities with extended wavelength coverage (e.g. JWST).

show abstract

The relative influence of H₂O and CO₂ on the primitive surface conditions and evolution of rocky planets

Cited by 93 publications

References 103 publications

Hydrogen isotopic evidence for early oxidation of silicate Earth

Hydrogen isotopic evidence for early oxidation of silicate Earth

Realistic collisional water transport during terrestrial planet formation

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Contact Info

Product

Resources

About

The relative influence of H2O and CO2 on the primitive surface conditions and evolution of rocky planets

Cited by 93 publications

References 103 publications

Hydrogen isotopic evidence for early oxidation of silicate Earth

Hydrogen isotopic evidence for early oxidation of silicate Earth

Realistic collisional water transport during terrestrial planet formation

Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations

Contact Info

Product

Resources

About

The relative influence of H₂O and CO₂ on the primitive surface conditions and evolution of rocky planets