Person:
Orlando, Thomas M.

Permanent Link
https://hdl.handle.net/1853/71563
Associated Organization(s)
ORCID
ArchiveSpace Name Record

Filters

2020 2
2
2
Reset filters

Settings
Author: Sarantos, Menelaos × Item Type: Publication × search.filters.applied.f.isOrgUnitOfPublicationTitle: School of Chemistry and Biochemistry ×

Publication Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Photon Stimulated Desorption of MgS as a Potential Source of Sulfur in Mercury’s Exosphere - Data Files
    (Georgia Institute of Technology, 2020-06-14) Schaible, Micah J. ; Sarantos, Menelaos ; Anzures, Brendan A. ; Parman, Stephen W. ; Orlando, Thomas M.
    Mercury has a relatively high sulfur content on its surface, and a signal consistent with 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) and time-of-flight (TOF) mass spectrometry. Though the PSD process is inherently non-thermal, the measured velocity distributions were fit using flux weighted Maxwellian distributions with translation energies ˂E> expressed as translational “temperatures” Tt = ˂E>/µkB. A bi-modal distribution consisting of both thermal (Tt = 300 K) and supra-thermal (Tt >1000 K) components in roughly a 2:1 ratio was found to best fit the data. The experimental PSD cross-section, ~4×10-22 cm2, and integrated velocity distributions were 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 a primary source to S0 in Mercury’s exosphere at low (<1000 km) altitudes.
  • No Thumbnail Available
    Item
    A New In Situ Quasi-continuous Solar-wind Source of Molecular Water on Mercury - Data Files
    (Georgia Institute of Technology, 2020) Jones, Brant M. ; Sarantos, Menelaos ; Orlando, Thomas M.
    Radar observations of Mercury and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft data indicate the probable existence of water ice in the permanently shadowed polar regions. Generally, water is accepted to be of exogenous origin through delivery via comets and meteoritic impact. However, a continuous water formation process that involves thermal transformation of chemically stable mineral-bound hydroxyl groups produced by implanted solar wind protons is readily available on the surface of Mercury. At typical temperatures prevailing on Mercury’s dayside surface, H2O can be produced from reactions involving OH groups on or within the H-saturated regolith grain interfaces. Similar reactions will also occur due to micrometeorite impact events on both the day and nightside. Once produced, H2O is released into the exosphere and then transported and processed via Jeans escape, photodissociation, dissociative adsorption, or condensation. Water reaching cold traps will be bound over geological periods. This simple water cycle will produce a highly chemically reduced surface and can contribute significant amounts of H2O over geological time periods. The overall process is an important but hitherto unnoticed source term that will contribute to the accumulation of water in the permanently shadowed regions of Mercury.