NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Solar Wind Implantation into Lunar Regolith: Hydrogen Retention in a Surface with DefectsSolar wind protons are implanted directly into the top 100 nm of the lunar near-surface region, but can either quickly diffuse out of the surface or be retained, depending upon surface temperature and the activation energy, U, associated with the implantation site. In this work, we explore the distribution of activation energies upon implantation and the associated hydrogen-retention times; this for comparison with recent observation of OH on the lunar surface. We apply a Monte Carlo approach: for simulated solar wind protons at a given local time, we assume a distribution of U values with a central peak, U(sub c) and width, U(sub w), and derive the fraction retained for long periods in the near-surface. We find that surfaces characterized by a distribution with predominantly large values of U (greater than 1 eV) like that expected at defect sites will retain implanted H (to likely form OH). Surfaces with the distribution predominantly at small values of U (less than 0.2 eV) will quickly diffuse away implanted H. However, surfaces with a large portion of activation energies between 0.3 eV less than U less than 0.9 eV will tend to be H-retentive in cool conditions but transform into H-emissive surfaces when warmed (as when the surface rotates into local noon). These mid-range activation energies give rise to a diurnal effect with diffusive loss of H at noontime.
Document ID
20170002398
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Farrell, W. M.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Hurley, D. M.
(Johns Hopkins Univ. Laurel, MD, United States)
Zimmerman, M. I.
(Johns Hopkins Univ. Laurel, MD, United States)
Date Acquired
March 21, 2017
Publication Date
September 28, 2014
Publication Information
Publication: Icarus
Publisher: Elsevier Inc.
Volume: 255
ISSN: 0019-1035
Subject Category
Solar Physics
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN40242
Distribution Limits
Public
Copyright
Other
Keywords
regolith
moon
solar wind

Available Downloads

There are no available downloads for this record.
No Preview Available