Abstract Details
| Name: Tirtha Pratim Das Affiliation: Scientist, Space Physics Laboratory, VSSC, ISRO Conference ID: ASI2018_1606 Title : Study of noble gases in lunar exosphere using the CHACE-MIP observation of Chandrayaan-1 Authors and Co-Authors : Tirtha Pratim Das Scientist, Vikram Sarabhai Space Centre, ISRO, Trivandrum Abstract Type : Thesis Abstract Category : Thesis Abstract : Earth’s Moon has a surface boundary exosphere (SBE), which is a result of the dynamic equilibrium between several source and sink processes. The lunar exosphere is also known to be highly variable, revealing a strong diurnal cycle and responds promptly to the fluctuations in the solar wind flux. The solar forcing on the Moon in terms of radiation, particles and fields make the sunlit side of the lunar exosphere more dramatic than the night side. On 14 November 2008, the CHandra’s Altitudinal Composition Explorer (CHACE) mass spectrometer (mass range: 1 to 100 amu) investigated of the sunlit side of the lunar neutral exosphere aboard the Moon Impact Probe (MIP) in the Chandrayaan-1 mission. The CHACE experiment yielded the first-ever (and till date unique) set of observations of the sunlit lunar exosphere with broad latitudinal (40 deg N to 89 deg S) and altitudinal (98 km to surface) coverage. The lunar exosphere is studied using noble gases (Ar, Ne, He) and H2 as tracers. The important outcomes of the experiment are listed below, which are the first of their kind. 1. Two dimensional (latitude versus altitude) distribution of lunar exospheric Ar, Ne and H2 based in the sunlit lunar exosphere along the plane of the MIP trajectory is established. 2. Results on the spatial heterogeneity and indications of inter-hemispherical asymmetry of radiogenic activity in the lunar interior through the measurement of the 40Ar:36Ar ratio. 3. Empirical formula connecting the surface number density of lunar Ne and the surface temperature is proposed. 4. Upper limit of the He density in the sunlit lunar exosphere under extreme astronomical conditions is proposed. 5. Spatial heterogeneity of H2 in the lunar exosphere is brought out. These results evoked enough scientific curiosity which prompted detailed in-situ investigation of the lunar exosphere from a polar orbiting platform in Chandrayaan-2, and are potential inputs for constraining the lunar exospheric models. |