Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere

Context. We present here an analysis of the potential sources of oxygen species in the Uranus atmosphere. Aims. Our aim is to explain the current measurements of HO, CO, and CO in the Uranus atmosphere, which would allow us to constrain the influx of oxygen-bearing species and its origin in this pla...

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Autores: Lara, Luisa María, Rodrigo Montero, Rafael, Moreno, R., Lampón, M.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2019
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/179444
Acceso en línea:http://hdl.handle.net/10261/179444
Access Level:acceso abierto
Palabra clave:Planets and satellites: Atmospheres
Planets and satellites: Individual: Uranus
Planets and satellites: Gaseous planets
Planets and satellites: Composition
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oai_identifier_str oai:digital.csic.es:10261/179444
network_acronym_str ES
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spelling Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere Lara, Luisa María Rodrigo Montero, Rafael Moreno, R. Lampón, M. Planets and satellites: Atmospheres Planets and satellites: Individual: Uranus Planets and satellites: Gaseous planets Planets and satellites: Composition Context. We present here an analysis of the potential sources of oxygen species in the Uranus atmosphere. Aims. Our aim is to explain the current measurements of HO, CO, and CO in the Uranus atmosphere, which would allow us to constrain the influx of oxygen-bearing species and its origin in this planet. Methods. We used a time-dependent photochemical model of the Uranus atmosphere to ascertain the origin of HO, CO, and CO. We thoroughly investigated the evolution of material delivered by a cometary impact, together with a combined source, i.e. cometary impact and a steady source of oxygen species from micrometeoroid ablation. Results. We find that an impactor in the size range ∼1.2-3.5 km hitting the planet between 450 and 822 yr ago could have delivered the CO currently seen in the Uranus stratosphere. Given the current set of observations, an oxygen-bearing species supply from ice grain ablation cannot be ruled out. Our study also indicates that a cometary impact cannot be the only source for rendering the observed abundances of HO and CO. The scenarios in which CO originates by a cometary impact and HO and CO result from ice grain sublimation can explain both the space telescope and ground-based data for HO, CO, and CO. Similarly, a steady influx of water, carbon monoxide, and carbon dioxide, and a cometary impact delivering carbon monoxide give rise to abundances matching the observations. The time evolution of HCN also delivered by a cometary impact (as 1% of the CO in mass), when discarding chemical recycling of HCN once it is lost by photolysis and condensation, produces a very low stratospheric abundance which could be likely non-detectable. Consideration of N-initiated chemistry could represent a source of HCN allowing for a likely observable stratospheric mixing ratio. Conclusions. Our modelling strongly indicates that water in the Uranus atmosphere likely originates from micrometeroid ablation, whereas its cometary origin can be discarded with a very high level of confidence. Also, we cannot firmly constrain the origin of the detected carbon monoxide on Uranus as a cometary impact, ice grain ablation, or a combined source due to both processes can give rise to the atmospheric mixing ratio measured with the Herschel Space Observatory. To establish the origin of oxygen species in the Uranus atmosphere, observations have to allow the retrieval of vertical profiles or HO, CO, and CO. Measurements in narrow pressure ranges, i.e. basically one pressure level, can be reproduced by different models because it is not possible to break this degeneracy about these three oxygen species in the Uranian atmosphere.© ESO 2019. This research has been supported by the Spanish Ministerio de Economía y Competitividad under contracts ESP2014–54062–R and ESP 2016–76076–R. M.L. acknowledges the Agencia Estatal de Investigación for the BES–2015–074542 Peer Reviewed EDP Sciences http://hdl.handle.net/10261/179444
title Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
spellingShingle Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
Lara, Luisa María
Planets and satellites: Atmospheres
Planets and satellites: Individual: Uranus
Planets and satellites: Gaseous planets
Planets and satellites: Composition
title_short Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
title_full Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
title_fullStr Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
title_full_unstemmed Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
title_sort Analysis of the origin of water, carbon monoxide, and carbon dioxide in the Uranus atmosphere
author Lara, Luisa María
author_facet Lara, Luisa María
Rodrigo Montero, Rafael
Moreno, R.
Lampón, M.
author_role author
author2 Rodrigo Montero, Rafael
Moreno, R.
Lampón, M.
author2_role author
author
author
topic Planets and satellites: Atmospheres
Planets and satellites: Individual: Uranus
Planets and satellites: Gaseous planets
Planets and satellites: Composition
topic_facet Planets and satellites: Atmospheres
Planets and satellites: Individual: Uranus
Planets and satellites: Gaseous planets
Planets and satellites: Composition
description Context. We present here an analysis of the potential sources of oxygen species in the Uranus atmosphere. Aims. Our aim is to explain the current measurements of HO, CO, and CO in the Uranus atmosphere, which would allow us to constrain the influx of oxygen-bearing species and its origin in this planet. Methods. We used a time-dependent photochemical model of the Uranus atmosphere to ascertain the origin of HO, CO, and CO. We thoroughly investigated the evolution of material delivered by a cometary impact, together with a combined source, i.e. cometary impact and a steady source of oxygen species from micrometeoroid ablation. Results. We find that an impactor in the size range ∼1.2-3.5 km hitting the planet between 450 and 822 yr ago could have delivered the CO currently seen in the Uranus stratosphere. Given the current set of observations, an oxygen-bearing species supply from ice grain ablation cannot be ruled out. Our study also indicates that a cometary impact cannot be the only source for rendering the observed abundances of HO and CO. The scenarios in which CO originates by a cometary impact and HO and CO result from ice grain sublimation can explain both the space telescope and ground-based data for HO, CO, and CO. Similarly, a steady influx of water, carbon monoxide, and carbon dioxide, and a cometary impact delivering carbon monoxide give rise to abundances matching the observations. The time evolution of HCN also delivered by a cometary impact (as 1% of the CO in mass), when discarding chemical recycling of HCN once it is lost by photolysis and condensation, produces a very low stratospheric abundance which could be likely non-detectable. Consideration of N-initiated chemistry could represent a source of HCN allowing for a likely observable stratospheric mixing ratio. Conclusions. Our modelling strongly indicates that water in the Uranus atmosphere likely originates from micrometeroid ablation, whereas its cometary origin can be discarded with a very high level of confidence. Also, we cannot firmly constrain the origin of the detected carbon monoxide on Uranus as a cometary impact, ice grain ablation, or a combined source due to both processes can give rise to the atmospheric mixing ratio measured with the Herschel Space Observatory. To establish the origin of oxygen species in the Uranus atmosphere, observations have to allow the retrieval of vertical profiles or HO, CO, and CO. Measurements in narrow pressure ranges, i.e. basically one pressure level, can be reproduced by different models because it is not possible to break this degeneracy about these three oxygen species in the Uranian atmosphere.© ESO 2019.
publishDate 2019
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url http://hdl.handle.net/10261/179444
eu_rights_str_mv openAccess
publisher EDP Sciences
institution Consejo Superior de Investigaciones Científicas (CSIC)
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
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publishDateSort 2019
author_browse Lampón, M.
Lara, Luisa María
Moreno, R.
Rodrigo Montero, Rafael
publisherStr EDP Sciences
score 6.924472

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