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    Photochemical escape of oxygen from Mars: First results from MAVEN in situ data

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    Issue Date
    2017-02-21
    Author
    Lillis, Robert J.
    Deighan, Justin
    Fox, Jane L.
    Bougher, Stephen W.
    Lee, Yuni
    Combi, Michael R.
    Cravens, Thomas Edward
    Rahmati, Ali
    Mahaffy, Paul R.
    Benna, Mehdi
    Elrod, Meredith K.
    McFadden, James P.
    Ergun, Robert E.
    Andersson, Laila
    Fowler, Christopher M.
    Jakosky, Bruce M.
    Thiemann, Ed
    Eparvier, Frank
    Halekas, Jasper S.
    Leblanc, François
    Chaufray, Jean-Yves
    Publisher
    American Geophysical Union
    Type
    Article
    Article Version
    Scholarly/refereed, publisher version
    Rights
    ©2017. American Geophysical Union. All Rights Reserved.
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    Abstract
    Photochemical escape of atomic oxygen is thought to be one of the dominant channels for Martian atmospheric loss today and played a potentially major role in climate evolution. Mars Atmosphere and Volatile Evolution Mission (MAVEN) is the first mission capable of measuring, in situ, the relevant quantities necessary to calculate photochemical escape fluxes. We utilize 18 months of data from three MAVEN instruments: Langmuir Probe and Waves, Neutral Gas and Ion Mass Spectrometer, and SupraThermal And Thermal Ion Composition. From these data, we calculate altitude profiles of the production rate of hot oxygen atoms from the dissociative recombination of O2+ and the probability that such atoms will escape the Mars atmosphere. From this, we determine escape fluxes for 815 periapsis passes. Derived average dayside hot O escape rates range from 1.2 to 5.5 × 1025 s−1, depending on season and EUV flux, consistent with several pre‐MAVEN predictions and in broad agreement with estimates made with other MAVEN measurements. Hot O escape fluxes do not vary significantly with dayside solar zenith angle or crustal magnetic field strength but depend on CO2 photoionization frequency with a power law whose exponent is 2.6 ± 0.6, an unexpectedly high value which may be partially due to seasonal and geographic sampling. From this dependence and historical EUV measurements over 70 years, we estimate a modern‐era average escape rate of 4.3 × 1025 s−1. Extrapolating this dependence to early solar system, EUV conditions gives total losses of 13, 49, 189, and 483 mbar of oxygen over 1–3 and 3.5 Gyr, respectively, with uncertainties significantly increasing with time in the past.
    URI
    http://hdl.handle.net/1808/27074
    DOI
    https://doi.org/10.1002/2016JA023525
    Collections
    • Physics and Astronomy Scholarly Works [1559]
    Citation
    Lillis, R. J., et al. (2017), Photochemical escape of oxygen from Mars: First results from MAVEN in situ data, J. Geophys. Res. Space Physics, 122, 3815–3836, doi:10.1002/2016JA023525

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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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