Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Evening Poster

P (Space and Planetary Sciences) » P-CG Complex & General

[P-CG22] New Developments of Planetary Sciences with ALMA

Wed. May 23, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Takayuki Muto(Division of Liberal Arts, Kogakuin University), Munetake Momose(The College of Science, Ibaraki University), Hideo Sagawa(京都産業大学理学部, 共同), Masumi Shimojo(National Astronomical Observatory of Japan)

[PCG22-P04] Investigation of Venusian upper troposphere using millimeter-wave continuum emission

*Hideo Sagawa1, Hiroyuki Maezawa2 (1.Kyoto Sangyo University, 2.Osaka Prefecture University)

Keywords:Venus, atmosphere, ALMA

Venus has dense 90-bar CO2 atmosphere with a thick cloud layer covering entire the planet at altitudes of ~50 - 70 km. This optically thick cloud layer hampers us to observe any information below the cloud. Only a few specific spectral regions at near infrared (e.g., 2.3 micron) play as the atmospheric “window” at which wavelengths the thermal emission from the hot lower atmosphere (~35 km for 2.3 micron window) leaks to the space. The emission at such near infrared wavelengths is attenuated by cloud particles, and can be used to retrieve cloud opacities.

A new approach to the upper troposphere of Venus is proposed by using millimeter-wave (microwave) observations. At the microwave region, the main opacity source in the Venusian atmosphere is the collision induced absorption (CIA) of CO2, whereas the cloud opacity becomes almost negligible due to relatively long wavelength of observations compared to the sizes of cloud particles (~order of several microns). The CO2 CIA reduces its absorption intensity with increasing the wavelength at millimeter-wave domain (and becomes almost transparent at radio frequencies). The radiative transfer calculation of the CO2 CIA opacity indicates that the thermal emission originated from the altitudes of ~40–60 km can be observed at millimeter-wave of λ = 3 - 4 mm (frequency of ~60 – 100 GHz) — which is the operation wavelength of the currently under development ALMA Band-2 receiver.

This study reviews potential scientific topics that can be investigated with the millimeter-wave continuum emission from Venus atmosphere, and presents feasibility study of the application of ALMA – Band 2 receiver in future Venus observations.