S. Gupta, R. V. Yelle, N. M. Schneider, S. K. Jain, A. S. Braude, L. Verdier, F. Montmessin, H. Nakagawa, M. Mayyasi, J. Deighan, S. M. Curry
{"title":"火星高层大气分子氧的昼夜差异","authors":"S. Gupta, R. V. Yelle, N. M. Schneider, S. K. Jain, A. S. Braude, L. Verdier, F. Montmessin, H. Nakagawa, M. Mayyasi, J. Deighan, S. M. Curry","doi":"10.1029/2024JE008322","DOIUrl":null,"url":null,"abstract":"<p>We use the extensive stellar occultation data set of the Imaging Ultraviolet Spectrograph aboard the Mars Atmosphere and Volatile EvolutioN spacecraft to determine the first quantification of vertical variation in O<sub>2</sub> mole fraction separately for day and night in the ∼90–130 km altitude range. The upper atmospheric O<sub>2</sub> variation is expected to be due to the interplay between diffusion and advection because of its long photochemical lifetime. It is therefore a useful tracer of the state of atmospheric mixing and circulation. The altitude-averaged mixing ratio is measured to be 2.69(±0.03) × 10<sup>−3</sup> for the nightside and 2.05(±0.03) × 10<sup>−3</sup> for the dayside. The average O<sub>2</sub> mole fraction for day and night are nearly identical below 105 km, consistent with the value of 1.61 × 10<sup>−3</sup> derived from the Mars Curiosity Rover/Sample Analysis at Mars near-surface measurements. At higher altitudes, dominated by molecular diffusive separation, the measured O<sub>2</sub> mole fraction demonstrates a vertical gradient with a local time dependence. The nightside mole fraction is a factor of 1.37 ± 0.04 larger than the dayside value at ∼125 km. This nightside enhancement is explained in terms of the relative role of solar-driven rapid horizontal winds at high altitudes and slower vertical diffusion, resulting in a nightside (dayside) downward (upward) diffusive flux. Using the 1-D diffusion model, the measured profiles correspond to a vertical eddy diffusion coefficient <i>K</i> = 3.5(±1.5) × 10<sup>6</sup> <i>cm</i><sup>2</sup>/<i>s</i>. The Mars Climate Database predicts comparable but lower day-night differences in oxygen mole fraction due to an overestimated <i>K</i> = 7.0(±1.0) × 10<sup>6</sup> <i>cm</i><sup>2</sup>/<i>s</i>, which affects atmospheric mixing as well as the rate of atmospheric escape to space.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":null,"pages":null},"PeriodicalIF":3.9000,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Day/Night Differences in Molecular Oxygen in the Martian Upper Atmosphere\",\"authors\":\"S. Gupta, R. V. Yelle, N. M. Schneider, S. K. Jain, A. S. Braude, L. Verdier, F. Montmessin, H. Nakagawa, M. Mayyasi, J. Deighan, S. M. Curry\",\"doi\":\"10.1029/2024JE008322\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>We use the extensive stellar occultation data set of the Imaging Ultraviolet Spectrograph aboard the Mars Atmosphere and Volatile EvolutioN spacecraft to determine the first quantification of vertical variation in O<sub>2</sub> mole fraction separately for day and night in the ∼90–130 km altitude range. The upper atmospheric O<sub>2</sub> variation is expected to be due to the interplay between diffusion and advection because of its long photochemical lifetime. It is therefore a useful tracer of the state of atmospheric mixing and circulation. The altitude-averaged mixing ratio is measured to be 2.69(±0.03) × 10<sup>−3</sup> for the nightside and 2.05(±0.03) × 10<sup>−3</sup> for the dayside. The average O<sub>2</sub> mole fraction for day and night are nearly identical below 105 km, consistent with the value of 1.61 × 10<sup>−3</sup> derived from the Mars Curiosity Rover/Sample Analysis at Mars near-surface measurements. At higher altitudes, dominated by molecular diffusive separation, the measured O<sub>2</sub> mole fraction demonstrates a vertical gradient with a local time dependence. The nightside mole fraction is a factor of 1.37 ± 0.04 larger than the dayside value at ∼125 km. This nightside enhancement is explained in terms of the relative role of solar-driven rapid horizontal winds at high altitudes and slower vertical diffusion, resulting in a nightside (dayside) downward (upward) diffusive flux. Using the 1-D diffusion model, the measured profiles correspond to a vertical eddy diffusion coefficient <i>K</i> = 3.5(±1.5) × 10<sup>6</sup> <i>cm</i><sup>2</sup>/<i>s</i>. The Mars Climate Database predicts comparable but lower day-night differences in oxygen mole fraction due to an overestimated <i>K</i> = 7.0(±1.0) × 10<sup>6</sup> <i>cm</i><sup>2</sup>/<i>s</i>, which affects atmospheric mixing as well as the rate of atmospheric escape to space.</p>\",\"PeriodicalId\":16101,\"journal\":{\"name\":\"Journal of Geophysical Research: Planets\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.9000,\"publicationDate\":\"2024-05-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geophysical Research: Planets\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1029/2024JE008322\",\"RegionNum\":1,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Planets","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024JE008322","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Day/Night Differences in Molecular Oxygen in the Martian Upper Atmosphere
We use the extensive stellar occultation data set of the Imaging Ultraviolet Spectrograph aboard the Mars Atmosphere and Volatile EvolutioN spacecraft to determine the first quantification of vertical variation in O2 mole fraction separately for day and night in the ∼90–130 km altitude range. The upper atmospheric O2 variation is expected to be due to the interplay between diffusion and advection because of its long photochemical lifetime. It is therefore a useful tracer of the state of atmospheric mixing and circulation. The altitude-averaged mixing ratio is measured to be 2.69(±0.03) × 10−3 for the nightside and 2.05(±0.03) × 10−3 for the dayside. The average O2 mole fraction for day and night are nearly identical below 105 km, consistent with the value of 1.61 × 10−3 derived from the Mars Curiosity Rover/Sample Analysis at Mars near-surface measurements. At higher altitudes, dominated by molecular diffusive separation, the measured O2 mole fraction demonstrates a vertical gradient with a local time dependence. The nightside mole fraction is a factor of 1.37 ± 0.04 larger than the dayside value at ∼125 km. This nightside enhancement is explained in terms of the relative role of solar-driven rapid horizontal winds at high altitudes and slower vertical diffusion, resulting in a nightside (dayside) downward (upward) diffusive flux. Using the 1-D diffusion model, the measured profiles correspond to a vertical eddy diffusion coefficient K = 3.5(±1.5) × 106cm2/s. The Mars Climate Database predicts comparable but lower day-night differences in oxygen mole fraction due to an overestimated K = 7.0(±1.0) × 106cm2/s, which affects atmospheric mixing as well as the rate of atmospheric escape to space.
期刊介绍:
The Journal of Geophysical Research Planets is dedicated to the publication of new and original research in the broad field of planetary science. Manuscripts concerning planetary geology, geophysics, geochemistry, atmospheres, and dynamics are appropriate for the journal when they increase knowledge about the processes that affect Solar System objects. Manuscripts concerning other planetary systems, exoplanets or Earth are welcome when presented in a comparative planetology perspective. Studies in the field of astrobiology will be considered when they have immediate consequences for the interpretation of planetary data. JGR: Planets does not publish manuscripts that deal with future missions and instrumentation, nor those that are primarily of an engineering interest. Instrument, calibration or data processing papers may be appropriate for the journal, but only when accompanied by scientific analysis and interpretation that increases understanding of the studied object. A manuscript that describes a new method or technique would be acceptable for JGR: Planets if it contained new and relevant scientific results obtained using the method. Review articles are generally not appropriate for JGR: Planets, but they may be considered if they form an integral part of a special issue.