Photon‐Stimulated Desorption of MgS as a Potential Source of Sulfur in Mercury's Exosphere

Mercury has a relatively high sulfur content on its surface, and a signal consistent with ionized atomic sulfur (S+) was observed by the fast ion plasma spectrometer (FIPS) instrument on the MESSENGER spacecraft. To help confirm this assignment and to better constrain the sources of exospheric sulfu...

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Bibliographic Details
Published in:Journal of geophysical research. Planets 2020-08, Vol.125 (8), p.n/a
Main Authors: Schaible, Micah J., Sarantos, Menelaos, Anzures, Brendan A., Parman, Stephen W., Orlando, Thomas M.
Format: Article
Language:English
Subjects:
Atmospheric models
Atoms & subatomic particles
Computer simulation
Desorption
Electron states
Exosphere
Ionization
Magnesium
Mass spectrometry
Mercury
Mercury (planet)
Mercury exosphere
Mercury surface
MESSENGER Spacecraft
Micrometeorites
Photons
photon‐stimulated desorption
Radiation
Solar wind
Spacecraft
Spectroscopy
Substrates
Sulfur
Sulfur content
Vaporization
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Summary:Mercury has a relatively high sulfur content on its surface, and a signal consistent with ionized atomic sulfur (S+) was observed by the fast ion plasma spectrometer (FIPS) instrument on the MESSENGER spacecraft. To help confirm this assignment and to better constrain the sources of exospheric sulfur at Mercury, 193 nm photon‐stimulated desorption (PSD) of neutral sulfur atoms (S0) from MgS substrates was studied using resonance‐enhanced multiphoton ionization (REMPI) spectroscopy and time‐of‐flight (TOF) mass spectrometry. Though the PSD process is inherently nonthermal, the measured velocities of ejected S0 were fit using flux‐weighted Maxwellian distributions with translation energies expressed as translational “temperatures” Ttrans = /μkB. A bimodal distribution consisting of both thermal (Ttrans = 300 K) and suprathermal (Ttrans > 1,000 K) components in roughly a 2:1 ratio was found to best fit the data. The PSD cross‐section was measured to be approximately 4 × 10−22 cm2 and, together with the velocity distributions, was used to calculate the PSD source rate of S0 into the exosphere of Mercury. Exosphere simulations using the calculated rates demonstrate that PSD is likely the primary source of S0 in Mercury's exosphere at low (
ISSN:2169-9097
2169-9100
DOI:10.1029/2020JE006479