Lunar exosphere dynamics at the north pole following Perseid 2009 meteoroid impacts

Abstract

Observations of the lunar exosphere provide valuable insights into dynamic processes affecting the Moon, such as meteoroid bombardment. The Chamberlain model was used to estimate the zenith column density and temperature of Na atoms on August 13/14, 2009 after the maximum of the Perseid meteor shower. The column density and temperature of Na atoms delivered to the lunar exosphere by slowly changing processes during the maximum of the Perseid meteor shower on August 12/13, 2009 are also estimated. Using the Chamberlain model and Monte Carlo simulations, expected ratios of line-of-sight column densities of Na atoms at three observed altitudes on August 12/13, 2009 are obtained. We attribute the heightened intensities of Na emission lines on August 12/13, 2009 to the onset of the third short-term peak in Perseid activity predicted by celestial mechanics. The best agreement between observations and theoretical models is achieved with a theoretical temperature of 3000 K for impact-produced Na atoms. This third peak of Perseids is estimated to have begun between 23:29 and 23:41 UT on August 12, 2009, lasting about 83 min, with a mass flux attributable to the Perseids ranging between 1.6 × 10⁻¹⁶ and 5 × 10⁻¹⁶ g cm⁻² s⁻¹. Additionally, depletion of Li content compared to Na content in the lunar exosphere is detected. We developed a model predicting Perseid meteoroid stream activity on the Moon, comparing it with performed spectral observations of the lunar exosphere. By modeling 25,000 years of comet 109P/Swift–Tuttle's orbits, we identified 175 cometary trails likely to have generated meteoroids near the Earth and the Moon during the Perseid 2009 meteor shower. Our results reveal annual maxima inducing filament trail structures, one of which aligned closely with the observed peak of the increased Na content in the lunar exosphere.