PowerPoint Presentation

Mercurys Seasonal Na Exosphere

Tim Cassidy, Aimee Merkel, Bill McClintock and the MASCS teamLiterature on Na exosphere, pre-MESSENGER:

That there is a dawn/dusk asymmetry, with more Na at dawnNa brightness peaks at the poles and is rapidly variable there, and that this is due to rapidly variable ion flux thereSometimes the brightness peaks near the subsolar pointA mix of processes supply the exosphere: sputtering, impact vaporization, thermal desorptionIn contrast to the rapid variability seen by most, models focus on seasonality

Potter andMorgan, 1990

Smyth and Marconi, 1995

Messenger limb scanvs.

Earth-based Na observationsMessenger UVVS data is especially valuable because it gives high resolution vertical profiles (limb scans) of the atmosphere

Potter andMorgan, 1990Killen et al., 2008column densityorradianceAltitude For Na, we will focus on near-surface (