Probe the lunar water ice ratios using FUV instrument

Chengling Kuo^1*, Chikuang Chao¹, Loren Chang¹, Jannyenq Liu¹, Winghuen Ip², Shinfa Li³, Jihrun Tsai³

¹Department of Space Science and Engineering, National Central University, Taiwan
²Graduate Institute of Astronomy, National Central University, Taiwan
³NSPO, Taiwan

* Presenter:Chengling Kuo, email:chengling.kuo@gmail.com

It is vital to investigate the water ice formation in the dilute lunar atmosphere or similar planetary environment. The origins, transport, and ice water formation are the crucial answer to the lunar water cycle. The lunar surface is a natural laboratory environment to study the water ice evidence and answer the possible lunar volatile transport in a high-radiation atmosphere. Knowing the spatial distribution of water ice will help future exploration of Lunar lander missions. We can also understand the water ice cycle's physical mechanism in a similar planetary environment. Diffuse illumination in the FUV band from interplanetary medium Lyman scattering and background UV-radiated stars can probe the PSRs. In PSRs in lack of sunlight, ice water can be deposited without destroying. A net migration toward the poles where the volatiles may be condensed in PSRs. Although some PSR with ice water is identified, careful evaluation of water ice abundance is still tricky. With the aids of the high sensitivity FUV instrument, we can precisely measure the lunar regolith reflectance and evaluate the water ice abundance in these identified PSRs. We proposed the FUV instrument to study these scientific topics from easy to difficult: (1A) Identify localized exposed water ice area of PSR; (1B) Evaluating the source, migration, and deposition of lunar polar volatiles by cold trapping; (2A) Spectral reversal of the lunar surface (maria/high land); (3A) Access the lunar atmosphere and its variability by the solar wind. These subjects are associated with instrument capability: (1) Pinpoints of water ice regions; (2) To evaluate the water abundance of lunar regolith; (3) Global FUV albedo of the lunar surface at night, (4) Global distribution of the water abundance of lunar regolith and (5) Solar wind data or other helpful data. The min requirement of FUV instruments are (1) nadir viewpoint, (2) polar orbit at low altitude (e.g., 100 km), and (3) two FUV Bands to evaluate the measurement ratios. Besides, with aids of modeling the albedo of mixing regolith and ice water in the lunar surface with considering other minerals (e.g., maria and high land), we will obtain a global map of the water abundance. With continuous recording, we can study the space weather effect of water ice remains. That will help us to reveal the water cycle in the Lunar Atmosphere and Dust Environment.

Keywords: FUV, lunar surface, water ice