# # Program information file # PROGRAM_ID 2023B066 PROGRAM_TITLE Surface composition of Venus inferred from near-infrared thermal mapping PROGRAM_INV1 Takao Sato PROGRAM_INV2 Hideo Sagawa PROGRAM_INV3 Shohei Aoki PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT major planets / satellites PROGRAM_ABSTRACT_BEG Why has Venus' climate evolved so different from Earth? - this is a fundamental question in planetary science, and also is the key to understand how the habitability has emerged in terrestrial rocky planets. Although there are many unsolved scientific problems on Venus' climate system, there is no doubt that the chemical interactions between the surface and atmosphere are playing a significant role there. For instance, a reaction with surface pyrite and CO2 atmosphere can be a buffer of gaseous SO2 and CO. However, the detail effectiveness of such interactions [chemical weathering] is still in debate. For the further understanding, a map of the surface composition becomes essential information. Recently, near-infrared emissivity of Venus' surface analog materials was measured under high-temperature conditions in laboratory. By comparing observed Venus' surface emissivity maps with such new database, it should be possible to constrain the surface composition of Venus. We propose to derive the Venus' surface emissivity maps by scanning the nightside disk with the prism and SXD modes of SpeX during the period around the inferior conjunction of Venus. The emissivity maps will be obtained by observing the thermal emissions from the surface at 0.85, 0.90, 1.02, 1.10, and 1.18 micron. Because the thermal emissions at these wavelengths are contaminated by the atmosphere and clouds of Venus, to remove such contamination with the aid of radiative transfer model at the data analysis stage, thermal emissions at 1.28, 1.31, 1.74, and 2.3 micron where the contribution from the surface is negligible are observed simultaneously. Our similar observation with SpeX is scheduled in the 2023A semester. This follow-up proposal aims to extend the observational coverage of the Venus' surface and to improve our analysis method. PROGRAM_ABSTRACT_END