A Comparison of the Importance of Electron-Stimulated Desorption of Sodium at Mercury and the Moon

We revisit the importance of Electron-Stimulated Desorption (ESD) as a source of neutral Na and Na+ in the exospheres of Mercury and the Moon. For the first time we have calibrated the ESD yield per electron as a function of electron energy in the energy range 100 - 950 eV. This calibrated yield per electron was convolved with the electron flux as a function of energy onto Mercury's cusps to determine the average release rate of Na+ to the exosphere, using electron flux and cusp area estimates from a recent hybrid magnetosphere model (Lavorenti, 2023). The electron flux and regions open to electrons are quite different at the Moon. Given that previous work showed the ESD yield of ions and neutral atoms are approximately equal, we compared the energy-weighted ESD release of Na+ to that deriving from impact vaporization, photon-stimulated desorption and ion-sputtering.