In order to observe the lunar sodium exosphere out to one-half degree around the Moon, we designed, built and installed a small robotically controlled coronagraph at the Winer Observatory in Sonoita, Arizona. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Center or from Prescott, Arizona. We employ an And over temperature-controlled 1.5 angstrom wide narrow-band filter centered on the sodium D-2 line, and a similar 1.5 angstrom filter centered blueward of the D-2 line by 3 angstrom for continuum observations. Our data encompass lunation in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images, During the course of three years we have refined the observational sequence in many respects. Therefore this paper only presents the results of the spring, 2017, observing season. We present limb profiles from the south pole to the north pole for many lunar phases. Our data do not fit any power of cosine model as a function of lunar phase or with latitude. The extended Na exosphere has a characteristic temperature of about 2250-6750 K, indicative of a partially escaping exosphere. The hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component.

Based on the equilibrium thermochemical approach and quenching theory, the formation of Na-, K-, Li-, Si-, Ca-, Al-, Mg-, and Fe-bearing molecules and dust particles in impact-produced clouds formed after collisions between meteoroids and the Moon is considered. Photolysis lifetimes and energies of photolysis products of oxides and hydroxides of the main elements are estimated. The estimated fraction of uncondensed species, and list of the main molecules and their properties regarding photolysis during impact processes may be useful for the analysis of future observations of atoms of alkali and refractory elements in the exospheres of the Moon and Mercury. (C) 2013 Elsevier Inc. All rights reserved.

We have extended our Monte Carlo model of exospheres [Wurz, P., Lammer, H., 2003. Icarus 164 (1), 1-13] by treating the ion-induced sputtering process from a known surface in a self-consistent way. The comparison of the calculated exospheric densities with experimental data, which are mostly upper limits, shows that all of our calculated densities are within the measurement limits. The total calculated exospheric density at the lunar surface of about 1 x 10(7) m(-3) as result of solar wind sputtering we find is much less than the experimental total exospheric density of about 10(12) m(-3). We conclude that sputtering contributes only a small fraction of the total exosphere, at least close to the surface. Because of the considerably larger scale height of atoms released via sputtering into the exosphere, sputtered atoms start to dominate the exosphere at altitudes exceeding a few 1000 km, with the exception of some light and abundant species released thermally, e.g. H-2, He, CH4, and OH. Furthermore, for more refractory species such as calcium, our model indicates that sputtering may well be the dominant mechanism responsible for the lunar atmospheric inventory, but observational data does not yet allow firm conclusions to be drawn. (C) 2007 Elsevier Inc. All rights reserved.