Detectable Abundance of Cyanoacetylene (HC<sub>3</sub>N) Predicted on Reduced Nitrogen-rich Super-Earth Atmospheres

Rimmer, Paul B.; Majumdar, Liton; Priyadarshi, Akshay; Wright, Sam; Yurchenko, Sergei N.

doi:10.3847/2041-8213/ac2f3a

Cited by 8 publications

(11 citation statements)

References 31 publications

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“…If M-dwarf planetary systems in fact feature late impacts of reducing debris-as is realized in a minor fraction of our simulations only-then JWST may be able to observe the transient signature of this (Ferus et al 2020;Rimmer et al 2021). Our simulations predict the observable time window for this to be in the first few tens of Myr across the M-dwarf mass spectrum.…”

Section: Observational Testsmentioning

confidence: 58%

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Lichtenberg

Clement

2022

ApJL

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Ocean-vaporizing impacts of chemically reduced planetesimals onto the early Earth have been suggested to catalyze atmospheric production of reduced nitrogen compounds and trigger prebiotic synthesis despite an oxidized lithosphere. While geochemical evidence supports a dry, highly reduced late veneer on Earth, the composition of late-impacting debris around lower-mass stars is subject to variable volatile loss as a result of their hosts’ extended pre-main-sequence phase. We perform simulations of late-stage planet formation across the M-dwarf mass spectrum to derive upper limits on reducing bombardment epochs in Hadean-analog environments. We contrast the solar system scenario with varying initial volatile distributions due to extended primordial runaway greenhouse phases on protoplanets and the desiccation of smaller planetesimals by internal radiogenic heating. We find a decreasing rate of late-accreting reducing impacts with decreasing stellar mass. Young planets around stars ≤0.4 M ⊙ experience no impacts of sufficient mass to generate prebiotically relevant concentrations of reduced atmospheric compounds once their stars have reached the main sequence. For M-dwarf planets to not exceed Earth-like concentrations of volatiles, both planetesimals, and larger protoplanets must undergo extensive devolatilization processes and can typically emerge from long-lived magma ocean phases with sufficient atmophile content to outgas secondary atmospheres. Our results suggest that transiently reducing surface conditions on young rocky exoplanets are favored around FGK stellar types relative to M dwarfs.

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Section: Observational Testsmentioning

confidence: 58%

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Lichtenberg

Clement

2022

ApJL

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“…If M-dwarf planetary systems in fact feature late impacts of reducing debris -as is realised in a minor fraction of our simulations only -then JWST may be able to observe the transient signature of this (Ferus et al 2020;Rimmer et al 2021). Our simulations predict the observable time window for this to be in the first few tens of Myr across the M-dwarf mass spectrum.…”

Section: Observational Testsmentioning

confidence: 59%

Reduced late bombardment on rocky exoplanets around M-dwarfs

Lichtenberg¹,

Clement²

2022

Preprint

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Ocean-vaporizing impacts of chemically reduced planetesimals onto the early Earth have been suggested to catalyse atmospheric production of reduced nitrogen compounds and trigger prebiotic synthesis despite an oxidized lithosphere. While geochemical evidence supports a dry, highly reduced late veneer on Earth, the composition of late-impacting debris around lower-mass stars is subject to variable volatile loss as a result of their hosts' extended pre-main sequence phase. We perform simulations of late-stage planet formation across the M-dwarf mass spectrum to derive upper limits on reducing bombardment epochs in Hadean analog environments. We contrast the Solar System scenario with varying initial volatile distributions due to extended primordial runaway greenhouse phases on protoplanets and desiccation of smaller planetesimals by internal radiogenic heating. We find a decreasing rate of late-accreting reducing impacts with decreasing stellar mass. Young planets around stars ≤ 0.4 M experience no impacts of sufficient mass to generate prebiotically relevant concentrations of reduced atmospheric compounds once their stars have reached the main sequence. For M-dwarf planets to not exceed Earth-like concentrations of volatiles, both planetesimals and larger protoplanets must undergo extensive devolatilization processes and can typically emerge from long-lived magma ocean phases with sufficient atmophile content to outgas secondary atmospheres. Our results suggest that transiently reducing surface conditions on young rocky exoplanets are favoured around FGK-stellar types relative to M-dwarfs.

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“…The presence and nature of any atmosphere on GJ 1132 b is highly debated (e.g., Southworth et al, 2017;Diamond-Lowe et al, 2018;Libby-Roberts et al, 2021;Mugnai et al, 2021), although P. B. Rimmer et al (2021) suggests that if the Swain et al (2021) data is correct, HC 3 N (cyanoacetylene) should be detectable on GJ 1132 b possibly with a single JWST transit.…”

Section: Discussionmentioning

confidence: 99%

Growth and evolution of secondary volcanic atmospheres: I. Identifying the geological character of warm rocky planets

Liggins,

Jordan,

Rimmer

et al. 2021

Preprint

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The geology of Earth and super-Earth sized planets will, in many cases, only be observable via their atmospheres. Here, we use the creation of volcanic atmospheres as a key window into planetary geochemistry. We couple volcanic outgassing with atmospheric chemistry models to simulate the growth of C-O-H-S-N atmospheres in thermochemical equilibrium, aiming to establish what information about the planet's mantle f O 2 and bulk silicate H/C ratio can be determined by atmospheric observation. Warm (800 K) volcanic atmospheres develop distinct compositional groups as the mantle f O 2 is varied, which can be identified using sets of (often minor) indicator species: Class O, representing an oxidised mantle and containing SO 2 and sulphur allotropes; Class I, formed by intermediate mantle f O 2 's and containing CO 2 , CH 4 , CO and COS; and Class R, produced by reduced mantles, containing H 2 , NH 3 and CH 4 . These atmospheric classes are largely independent of the bulk silicate H/C ratio. However, the H/C ratio does affect the dominant atmospheric constituent, which can vary between H 2 , H 2 O, CO 2 and CH 4 once the chemical composition has stabilised to a point where it no longer changes substantially with time. This final state is dependent on the mantle f O 2 , the H/C ratio, and time since the onset of volcanism. Superchondritic H/C enrichment to the level of Earth (H/C = 0.99 ± 0.42) and higher can only be inferred for planets with reduced mantles producing Class R atmospheres. On warm, volcanically active planets, mantle f O 2 could be identifiable from atmospheric observations using JWST.

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Detectable Abundance of Cyanoacetylene (HC₃N) Predicted on Reduced Nitrogen-rich Super-Earth Atmospheres

Cited by 8 publications

References 31 publications

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Reduced late bombardment on rocky exoplanets around M-dwarfs

Growth and evolution of secondary volcanic atmospheres: I. Identifying the geological character of warm rocky planets

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Detectable Abundance of Cyanoacetylene (HC3N) Predicted on Reduced Nitrogen-rich Super-Earth Atmospheres

Cited by 8 publications

References 31 publications

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Reduced late bombardment on rocky exoplanets around M-dwarfs

Growth and evolution of secondary volcanic atmospheres: I. Identifying the geological character of warm rocky planets

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Product

Resources

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Detectable Abundance of Cyanoacetylene (HC₃N) Predicted on Reduced Nitrogen-rich Super-Earth Atmospheres