Abstract
Abstract In situ measurement of Moon-originating ions picked-up in orbit round the Moon is expected to provide valuable information regarding the thin lunar atmosphere and surface. Secondary ions sputtered by the solar wind ions reflect the surface abundance. Global composition mapping of the lunar surface may be thus achieved by measuring the sputtered ions as one would perform laboratory SIMS.We studied the dynamics of picked-up lunar ions when the Moon was exposed to the solar wind. Our model’s source mechanism involved photoionization of the lunar exospheric atoms, photon-stimulated ion desorption, and ion sputtering. We propose that an intense flux of picked-up lunar ions (104 /cm2 sec) exists at an altitude of 100 km, for nearly a quarter of the orbit. The ion flux originating from the lunar surface is mono-directional and mono-energetic, and is distinguishable from that of lunar atmospheric origin whose energy spectra correspond to their spatial distribution. Our calculation suggested that ion measurements in orbit round the Moon enable remote SIMS analyses.
Highlights
The Moon, Mercury, and some of the planetary satellites and asteroids maintain thin and sometimes transient atmospheres
The ion flux originating from the lunar surface is mono-directional and mono-energetic, and is distinguishable from that of lunar atmospheric origin whose energy spectra correspond to their spatial distribution
The yields of Na+ generated by photon-stimulated desorption (PSD) and by the solar wind sputtering are extremely larger than the yield of Na+ originating from the atmosphere, the sum of the Na+ yield from the atmosphere between the surface and 100-km altitude is larger than the yields from the surface
Summary
The Moon, Mercury, and some of the planetary satellites and asteroids maintain thin and sometimes transient atmospheres. The ion transport simulation of Cladis et al (1994) verified that some lunar ion species could be detected by spacecraft that is the upstream of the Earth’s bow shock in spite of diffusion caused by magnetic turbulence These previous observations and experiments suggested that a variety of ions originating from the lunar atmospheres and surface presumably exist around the Moon. As for the source mechanism of the thin lunar alkali atmosphere, five processes have been proposed These are (1) thermal desorption, (2) electron-stimulated desorption (ESD), (3) photon-stimulated desorption (PSD), (4) ioninduced desorption (sputtering), and (5) vaporization by micrometeoroid impacts (Madey et al, 1998, and references therein). The dependence on the solar zenith angle was cos φ because the sputtering yields are proportional to the solar wind ion flux
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
