HCN production from impact ejecta on the early Earth

Parkos, Devon; Pikus, Aaron; Alexeenko, Alina; Melosh, H. J.

doi:10.1063/1.4967665

Cited by 6 publications

(9 citation statements)

References 13 publications

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“…Following the integration of species fluxes at the domain boundaries, we use the extracted CN and HCN generation rates to form a response surface for chemical production rates as a function of altitude and velocity for each examined ejecta collocation point. We then stochastically propagate spherule trajectories (Parkos et al, , ). More information on this process is provided in the supporting information (O'Keefe & Ahrens, ).…”

Section: Resultsmentioning

confidence: 99%

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

et al. 2018

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Major impact events have shaped the Earth as we know it. The Late Heavy Bombardment is of particular interest because it immediately precedes the first evidence of life. The reentry of impact ejecta creates numerous chemical by‐products, including biotic precursors such as HCN. This work examines the production of HCN during the Late Heavy Bombardment in more detail. We stochastically simulate the range of impacts on the early Earth and use models developed from existing studies to predict the corresponding ejecta properties. Using multiphase flow methods and finite‐rate equilibrium chemistry, we then find the HCN production due to the resulting atmospheric heating. We use Direct Simulation Monte Carlo to develop a correction factor to account for increased yields due to thermochemical nonequilibrium. We then model 1‐D atmospheric turbulent diffusion to find the time accurate transport of HCN to lower altitudes and ultimately surface water. Existing works estimate the necessary HCN molarity threshold to promote polymerization that is 0.01 M. For a mixing depth of 100 m, we find that the Late Heavy Bombardment will produce at least one impact event above this threshold with probability 24.1% for an oxidized atmosphere and 56.3% for a partially reduced atmosphere. For a mixing depth of 10 m, the probability is 79.5% for an oxidized atmosphere and 96.9% for a partially reduced atmosphere. Therefore, Late Heavy Bombardment impact ejecta is likely an HCN source sufficient for polymerization in shallow bodies of water, particularly if the atmosphere were in a partially reduced state.

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Section: Resultsmentioning

confidence: 99%

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

et al. 2018

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“…Abiotic fixation in the early Archean included lightning, high-energy particle interaction, atmospheric shock heating by frequent meteorite impacts, a higher solar UV radiation, and coronal mass ejections related to super flares (e.g., Airapetian et al, 2016). Generally, also throughout later periods until today, nonbiological pathways occur via hightemperature reducing or oxidation reactions of N 2 to NH x / HCN/NO x (Navarro-González et al, 2001;Martin et al, 2007;Parkos et al, 2016), depending on the environment's redox state. These occur during combustion or lightning in the troposphere, followed by conversion into water-soluble molecules (e.g., HNO 3 ) within the atmosphere, which are quickly scavenged by rain.…”

Section: Development Of the Geobiological Nitrogen Cyclementioning

confidence: 99%

“…The other above-mentioned fixation processes are still present in the Archean and estimated to fix 1-10 (Tg N)/yr (Navarro-González et al, 1998), whereby EUVdriven photochemistry and the impactor flux decrease in efficiency over time. All these processes can also be responsible for substantial amounts of HCN molecules in a reducing atmosphere, quickly deposited by rain (e.g., Zahnle, 1986;Martin et al, 2007;Parkos et al, 2016). Assuming today's nitrogen outgassing, the buildup of a significant partial surface pressure within this period is not possible-even assuming a factor of 10 higher volcanic activities (Sano et al, 2001;Hilton et al, 2002; see the tables in the appendix).…”

Section: The Likely Evolution Of the Nitrogen Partial Pressure On Earthmentioning

confidence: 99%

The Role of N₂as a Geo-Biosignature for the Detection and Characterization of Earth-like Habitats

et al. 2019

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Since the Archean, N 2 has been a major atmospheric constituent in Earth's atmosphere. Nitrogen is an essential element in the building blocks of life; therefore, the geobiological nitrogen cycle is a fundamental factor in the long-term evolution of both Earth and Earth-like exoplanets. We discuss the development of Earth's N 2 atmosphere since the planet's formation and its relation with the geobiological cycle. Then we suggest atmospheric evolution scenarios and their possible interaction with life-forms: first for a stagnant-lid anoxic world, second for a tectonically active anoxic world, and third for an oxidized tectonically active world. Furthermore, we discuss a possible demise of present Earth's biosphere and its effects on the atmosphere. Since life-forms are the most efficient means for recycling deposited nitrogen back into the atmosphere at present, they sustain its surface partial pressure at high levels. Also, the simultaneous presence of significant N 2 and O 2 is chemically incompatible in an atmosphere over geological timescales. Thus, we argue that an N 2 -dominated atmosphere in combination with O 2 on Earth-like planets within circumstellar habitable zones can be considered as a geo-biosignature. Terrestrial planets with such atmospheres will have an operating tectonic regime connected with an aerobic biosphere, whereas other scenarios in most cases end up with a CO 2 -dominated atmosphere. We conclude with implications for the search for life on Earth-like exoplanets inside the habitable zones of M to K stars.Abbreviations anammox ¼ anaerobic ammonium oxidation ELT ¼ Extremely Large Telescope GOE ¼ Great Oxidation Event 950 LAMMER ET AL.

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“…Earth's present thunderstorm lightning fixes 4-6 Tg N/yr [144][145][146][147][148], which sums up to more than 10 mbar N in 10 Myr [73]). Generally, throughout Earth's history, abiotic fixation pathways have occurred via high-temperature reduction or oxidation reactions of N2 to NHx/HCN/NOx depending on the environment's redox state [73,[149][150][151]. The resulting compounds are mostly water-soluble molecules that are quickly deposited by rain [146].…”

Section: Atmospheric Electricitymentioning

confidence: 99%

Ariel – a window to the origin of life on early earth?

et al. 2020

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Is there life beyond Earth? An ideal research program would first ascertain how life on Earth began and then use this as a blueprint for its existence elsewhere. But the origin of life on Earth is still not understood, what then could be the way forward? Upcoming observations of terrestrial exoplanets provide a unique opportunity for answering this fundamental question through the study of other planetary systems. If we are able to see how physical and chemical environments similar to the early Earth evolve we open a window into our own Hadean eon, despite all information from this time being long lost from our planet's geological record. A careful investigation of the chemistry expected on young exoplanets is therefore necessary, and the preparation of reference materials for spectroscopic observations is of paramount importance. In particular, the deduction of chemical markers identifying specific processes and features in exoplanetary environments, ideally "uniquely". For instance, prebiotic feedstock molecules, in the form of aerosols and vapours, could be observed in transmission spectra in the near future whilst their surface deposits could be observed from reflectance spectra. The same detection methods also promise to identify particular intermediates of chemical and physical processes known to be prebiotically plausible. Is Ariel truly able to open a window to the past and answer questions concerning the origin of life on our planet and the universe? In this paper, we discuss aspects of prebiotic chemistry that will help in formulating future observational and data interpretation strategies for the Ariel mission. This paper is intended to open a discussion and motivate future detailed laboratory studies of prebiotic processes on young exoplanets and their chemical signatures.

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HCN production from impact ejecta on the early Earth

Cited by 6 publications

References 13 publications

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

The Role of N₂as a Geo-Biosignature for the Detection and Characterization of Earth-like Habitats

Ariel – a window to the origin of life on early earth?

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HCN production from impact ejecta on the early Earth

Cited by 6 publications

References 13 publications

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

The Role of N2as a Geo-Biosignature for the Detection and Characterization of Earth-like Habitats

Ariel – a window to the origin of life on early earth?

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The Role of N₂as a Geo-Biosignature for the Detection and Characterization of Earth-like Habitats