BIROn - Birkbeck Institutional Research Online

    Complex burial histories of Apollo 12 basaltic soil grains derived from cosmogenic noble gases: implications for local regolith evolution and future in situ investigations

    Nottingham, M. and Stuart, F. and Chen, B. and Zurakowska, M. and Gilmour, J. and Alexander, L. and Crawford, Ian and Joy, K. (2022) Complex burial histories of Apollo 12 basaltic soil grains derived from cosmogenic noble gases: implications for local regolith evolution and future in situ investigations. Meteoritics and Planetary Science 57 (3), pp. 603-634. ISSN 1086-9379.

    [img]
    Preview
    Text
    Meteorit Planetary Scien - 2022 - Nottingham - Complex burial histories of Apollo 12 basaltic soil grains derived from.pdf - Published Version of Record
    Available under License Creative Commons Attribution.

    Download (2MB) | Preview

    Abstract

    We report the concentrations and isotope ratios of light noble gases (He, Ne, Ar) in ten small basalt fragments derived from lunar regolith soils at the Apollo 12 landing site. We use cosmic ray exposure and shielding condition histories to consider their geological context. We have devised a method of using cosmogenic Ne isotopes to partition the cosmic ray exposure history of each sample into two stages: a duration of ‘deep’ burial (shielding of 5-500 g/cm2) and a duration of near-surface exposure (shielding of 0 g/cm2). Three samples show evidence of measurable exposure at the lunar surface (durations of between 6 ± 2 to 7 ± 2 Myr). The remaining seven samples show evidence of a surface residence duration of less than a few hundred thousand years prior to collection. One sample records a single stage cosmic ray exposure age range of between 516 ± 36 and 1139 ± 121 Myr, within 0-5 g/cm2 of the lunar surface. This is consistent with derivation from ballistic sedimentation (i.e., local regolith reworking) during the Copernicus crater formation impact at ~ 800 Myr. The remaining samples show cosmic ray exposure age cluster around 124 ± 11 Myr, and 188 ± 15 Myr. We infer that local impacts, including Surveyor crater (180-240 Ma) and Head crater (144 Ma), may have brought these samples to depths where the cosmic ray flux was intense enough to produce measurable cosmogenic Ne isotopes. More recent small impacts that formed un-named craters may have exhumed these samples from their deep shielding conditions to the surface (i.e., ~0-5 g/cm2) prior to collection from the lunar surface during the Apollo 12 mission.

    Metadata

    Item Type: Article
    School: School of Science > Earth and Planetary Sciences
    Research Centres and Institutes: Planetary Sciences, Centre for (CPS)
    Depositing User: Ian Crawford
    Date Deposited: 14 Mar 2022 14:23
    Last Modified: 15 Mar 2022 14:25
    URI: https://eprints.bbk.ac.uk/id/eprint/47741

    Statistics

    Downloads
    Activity Overview
    9Downloads
    14Hits

    Additional statistics are available via IRStats2.

    Archive Staff Only (login required)

    Edit/View Item Edit/View Item