金星大気の観測 これまで
（風速以外）	
今村(JAXA)	

Venera-4 Descent
Module (1967)

Marov (1978)	

Marov (1978)	

Polarization of sunlight reflectedby Venus	
Hansen & Hovenier (1974)	

Refractive index = 1.44
àconsistent with H2SO4-H2O
solution
Effective radius ~ 1 µm 	Microphysical properties• H2SO4-H2O droplets with radii r < 5 µm
• Smallest mode (including sub-cloud haze) might becondensation nuclei whose composition is unknown.
• Size distribution is variable.
Knollenberg & Hunten (1980)	
Pioneer Venus LCPS (54 km)

Mode 1

Venera-13
LanderMode 2Mode 30.11
10Diameter (µm)

Cl ? S ? P ?	

Microphysical properties••

H2SO4-H2O droplets with radii r < 5 µm
Smallest mode (including sub-cloud haze) might be condensation
nuclei whose composition is unknown.
• Size distribution is variable.
Pioneer Venus LCPS
(54 km)Mode 1

Vega ISAV(48-52 km)

Mode 2Mode 30.1

1
10Diameter (µm)

Knollenberg & Hunten (1980)	

0.5

1
2 3 4 5Diameter (µm)

Gnedykh et al., 1987	

Three-layered structure – Different dynamical and chemicalregimes at different altitudes?
Pioneer Venus LCPS (Knollenberg and Hunten, 1980)

Static stability
measured by entry
The bulk of theprobes

mass exists inMode 2 (r ~ 1µm)

Middle cloud
Lower cloud

Altitude (km)Upper cloud

The bulk of themass exists inMode 2 and 3 (r= 1-5 µm)

Sulfur-rich atmosphere: origin of H2SO4 ?	
SO2 measurements by Vega landers	

Bertaux et al. (1996)	

H2SO4 vapor profiles

oby Pioneer Venus

67 N byMagellan

Equator by Mariner 10050km

50km

40km

40km

5 (ppm)05Equator

High lat.

10 15 (ppm)

Kolodner & Steffes (1998)

Jenkins & Steffes (1991)

Traditional 1D model(Krasnopolsky & Pollack 1994; James et al. 1997)
70km

Photochemical production of
H2SO4 from SO2 and H2O
60km

Upward diffusion of
SO2 and H2O

CloudSedimentation of
H2SO4-H2O droplets

50km

Evaporation (Cloud base)Upward diffusion of
40km
SO2 and H2O

30km

Downward diffusion of
H2SO4 vapor
Thermal decomposition of
H2SO4 into SO2 and H2O

Ground-based observations of cloudrelated gaseous species	

Pollack et al., Icarus 103, 1, 1993	

Retrieved vertical profiles	

Pollack et al., Icarus 103, 1, 1993	

硫黄サイクル	

CO2安定化サイクル	

硫酸エアロゾル	

凝結核？太陽光吸収物質？	

Sを含む主要物質であるSO2	Zhang	  et	  al.	  (2012)	

Mills	  et	  al.	  (2007)	

SO, SO2 profiles above cloud observed by Venus Express
solar occultations (Belyaev et al. 2011)	

SO: blackSO2: blue	• Enhancement at high altitudes cannot be explained bytraditional photochemical models. 	

(Zhang et al. 2012)	
Artificial H2SO4 source added above 90 km:	Transport of cloud particles to theupper atmosphere by winds ?
à Open question	

Pioneer Venus
紫外画像(365 nm)	

雲の模様の源	••

遠紫外（<320nm）の吸収はほぼSO2
近紫外（>320nm）の吸収物質の候補： S3, S4, S8, Cl2, FeCl3, SCl2, C5O5H2,(NH4)2S2O5, NOHSO4, S2O (Mills et al. 2007)

UV absorption coefficient based on
Venera probe measurements	

Ekonomov et al. (1984)	

Crisp (1986)	

Other vertical transport processes

Y-feature- Kelvin wave?

‘Cells’ near sub-solar region

Convection cells near subsolar?
Amplitude of the diurnal
component of solar heating (K/day)(Crisp 1986)

Cloud-top water vapor observed by Pioneer
Venus (Koukouli et al. 2005)

Radio wave generation by lightning discharges ?	

Russell et al. (2008)	

電波での放射率	

標高	雲アルベドによる気候安定化仮説(Hashimoto & Abe, 2005） 	

気候を安定化する可能性大気-地殻化学相互作用	
炭酸塩による大気バッファ仮説		
CaSiO3 + CO2 ßà CaCO3 + SiO2

気候を不安定化する可能性(はしもと・阿部、1998)

Variability of SO2 above clouds	Belyaev et al. (2008)	

Volcanic eruptions ?
Change of atmospheric dynamics ?	

Marcq et al. 2012