Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan
Thermochemical modeling and shock-tube experiments show that shocks applied to N _2 /CH _4 gas mixtures can synthesize organic molecules. Sufficiently large, hypersonic meteoroids entering the atmosphere of Saturn’s moon Titan should therefore drive organic chemistry. To do so meteoroids must be suf...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Planetary Science Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/PSJ/acdfc9 |
| _version_ | 1797326959821193216 |
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| author | Erin E. Flowers Christopher F. Chyba |
| author_facet | Erin E. Flowers Christopher F. Chyba |
| author_sort | Erin E. Flowers |
| collection | DOAJ |
| description | Thermochemical modeling and shock-tube experiments show that shocks applied to N _2 /CH _4 gas mixtures can synthesize organic molecules. Sufficiently large, hypersonic meteoroids entering the atmosphere of Saturn’s moon Titan should therefore drive organic chemistry. To do so meteoroids must be sufficiently large compared to the atmospheric mean free path at a given altitude to generate shocks, and deposit enough energy per path length to produce temperatures high enough to excite and dissociate the relevant molecules. The Cassini spacecraft imaged multiple meteoroid impacts on Saturn’s rings, allowing for the first time an empirical estimate to be made of the flux and size–frequency distributions of meteoroids in the millimeter-to-meter size range. We combine these results with an atmospheric entry model and thermochemical and experimental shock production efficiencies for N _2 /CH _4 atmospheres and calculate the shock production rates for HCN, C _2 H _2 , and C _2 H _4 as well as the resulting H _2 generation. We find that meteoroids may be producing these molecules at as much as ∼1% the production rate of photochemistry driven by UV photons, and may be depositing more energy than magnetospheric ions and 90–100 nm UV photons. Moreover, these meteoroids produce these organic molecules hundreds of kilometers lower in Titan’s atmosphere than the relevant UV photons and magnetospheric ions penetrate, with peak production occurring between 200 and 500 km altitudes, i.e., at the observed haze layer. Meteoroid-driven shock generation of molecules may therefore be crucial to understanding Titan’s atmospheric chemistry. |
| first_indexed | 2024-03-08T06:31:38Z |
| format | Article |
| id | doaj.art-bf1c5971f07b4d969dfb60de79207ff5 |
| institution | Directory Open Access Journal |
| issn | 2632-3338 |
| language | English |
| last_indexed | 2024-03-08T06:31:38Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Planetary Science Journal |
| spelling | doaj.art-bf1c5971f07b4d969dfb60de79207ff52024-02-03T11:21:27ZengIOP PublishingThe Planetary Science Journal2632-33382023-01-014712710.3847/PSJ/acdfc9Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of TitanErin E. Flowers0https://orcid.org/0000-0001-8045-1765Christopher F. Chyba1https://orcid.org/0000-0002-6757-4522Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08540, USADepartment of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08540, USA; School of Public and International Affairs, Princeton University , 20 Prospect Lane, Princeton, NJ 08540, USAThermochemical modeling and shock-tube experiments show that shocks applied to N _2 /CH _4 gas mixtures can synthesize organic molecules. Sufficiently large, hypersonic meteoroids entering the atmosphere of Saturn’s moon Titan should therefore drive organic chemistry. To do so meteoroids must be sufficiently large compared to the atmospheric mean free path at a given altitude to generate shocks, and deposit enough energy per path length to produce temperatures high enough to excite and dissociate the relevant molecules. The Cassini spacecraft imaged multiple meteoroid impacts on Saturn’s rings, allowing for the first time an empirical estimate to be made of the flux and size–frequency distributions of meteoroids in the millimeter-to-meter size range. We combine these results with an atmospheric entry model and thermochemical and experimental shock production efficiencies for N _2 /CH _4 atmospheres and calculate the shock production rates for HCN, C _2 H _2 , and C _2 H _4 as well as the resulting H _2 generation. We find that meteoroids may be producing these molecules at as much as ∼1% the production rate of photochemistry driven by UV photons, and may be depositing more energy than magnetospheric ions and 90–100 nm UV photons. Moreover, these meteoroids produce these organic molecules hundreds of kilometers lower in Titan’s atmosphere than the relevant UV photons and magnetospheric ions penetrate, with peak production occurring between 200 and 500 km altitudes, i.e., at the observed haze layer. Meteoroid-driven shock generation of molecules may therefore be crucial to understanding Titan’s atmospheric chemistry.https://doi.org/10.3847/PSJ/acdfc9TitanNatural satellite atmospheres |
| spellingShingle | Erin E. Flowers Christopher F. Chyba Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan The Planetary Science Journal Titan Natural satellite atmospheres |
| title | Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan |
| title_full | Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan |
| title_fullStr | Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan |
| title_full_unstemmed | Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan |
| title_short | Shock Synthesis of Organic Molecules by Meteoroids in the Atmosphere of Titan |
| title_sort | shock synthesis of organic molecules by meteoroids in the atmosphere of titan |
| topic | Titan Natural satellite atmospheres |
| url | https://doi.org/10.3847/PSJ/acdfc9 |
| work_keys_str_mv | AT erineflowers shocksynthesisoforganicmoleculesbymeteoroidsintheatmosphereoftitan AT christopherfchyba shocksynthesisoforganicmoleculesbymeteoroidsintheatmosphereoftitan |