Recent spacecraft observations reveal properties of Martian dust and the feature of Martian dust storm and its horizontal scale, occurrence frequency and duration. Because of increasing of Martian meteorological data, numerical simulation of Martian dust storm by using General Circulation Model (GCM) which can predict distribution of atmospheric dust are now beginning to be challenged by several research groups. In order to improve forecast performance of atmospheric dust distribution by using GCM, it is necessary to consider parameters associated with micro physics of dust loading and parameterization of small scale wind fluctuations which cannot be represented in GCM explicitly.
The sulfuric acid cloud of Venus is a highly-variable and complicated system driven by photochemistry and atmospheric dynamics. The upper part of the cloud layer is generally thought of as photochemical haze, while the lower part is formed by the condensation of sulfuric acid vapor supplied by dynamical motions from the reservoir below. The elucidation of this system is crucial for understanding the energy balance and the chemical cycle of the Venusian atmosphere. In spite of many previous observations and theoretical studies, however, many fundamental questions raised so far still remain unsolved. Various observations with new techniques are now being conducted to explore this complicated system.
Traditional understanding and recent studies on the cloud structure of Jupiter's atmosphere are briefly reviewed, and the effects of aerosols on Jupiter's clouds are discussed. The cloud structure of Jupiter's atmosphere has been expected by using Equilibrium Cloud Condensation Model (ECCM) . It shows that H2O forms the lowest cloud layer and that the cloud layer of NH4SH and NH3 ice form above that of the H2O ice. The results of the optical remote sensing by Galileo Orbiter and the direct measurement by Galileo Probe were, however, not consistent with the prediction of ECCM. Recently, we have been numerically investigating possible cloud structures of Jupiter by using moist convection model which can represent convective motion and associated cloud formation explicitly. The results of numerical simulations performed by using moist convection model show that the H2O and NH4SH clouds can be advected to the altitude of the NH3 cloud layer by convective motion. For further investigation of the cloud structure of Jupiter's atmosphere, however, it is necessary to consider the effects of the candidate species of aerosols in Jupiter's atmosphere on its cloud microphysics.
Planetary aerosol laboratory experiments for science education were carried out in a curriculum of Kyoto University. Our goal is to reproduce “the blue sunset” on Mars which are reported from NASA's Mars Pathfinder. In reproducing the rays scattered by Martian atmosphere (dust storm) in a laboratory, the number density of scattering particles has to be as large as possible. Three experiments were conducted in the air and water. Although we were not able to reproduce Martian blue sunset, we elucidated its spectrum. Converting this spectrum to a color in the RGB system, we obtained R = 114, G = 122, B = 192. Though the experiment, we proved that planetary aerosol laboratory experiments are significantly fruitful for science education as well as for science studies. We propose that researchers and lecturers should make active use of planetary aerosol laboratory experiments for science education.
Titan is the largest satellite of Saturn, and has dense (ca. 1,500 hPa) atmosphere mainly composed of nitrogen and methane. In addition to various organic compounds, aerosol is found in the atmosphere. It is suggested that the aerosol was made of complex organic compounds, which was formed from Titan atmosphere by such energies as ultraviolet light, high-energy electrons (discharges) and cosmic rays. Voyager and Cassini missions partly revealed the nature of the aerosol. A wide variety of laboratory simulation experiments have been conducted by using a gas mixture of nitrogen and methane, and the resulting solid products are often referred as “Titan tholins”. The present paper reviews these observations and simulation experiments on the Titan aerosol, and discusses its relevance to origins of life.
We present the current status of the research for interplanetary dust particles, based on the results recently obtained by space missions for exploration of primitive bodies, i.e. Stardust and Deep-impact missions to comets, and HAYABUSA mission to asteroid. The comet missions have suggested the existence of grain materials produced in high (beyond 1,000 K) temperature region, which implies the presence of radial convection of grains in the proto-planetary nebula. On the other hand, the asteroid mission has revealed that the asteroid Itokawa has low mass density of 1.95 g/cm3, and consequently it suggests high interior porosity of about 40 %. This evidence suggests that the occurrence of catastrophic collisional disruption of mother bodies yielded the high porosity aggregates consisting of fragment debris, as well as a large amount of dust particles in interplanetary space.
PM2.5 and PM1 mass concentrations, and elemental carbon (EC) , organic carbon (OC) , and trace metal concentrations in PM2.5 and PM1 were measured in the Tokyo metropolitan area during winter and summer in 2004. PM2.5 and PM1 were collected by using multi-nozzle cascade impactor (MCI) . Sum of concentrations of elemental carbon and organic compounds accounted for 75 % of PM1 mass concentrations in winter, while it did only 30 % in summer. It was possibly due to the enhancement of photochemical formation of secondary inorganic compounds (mainly sulfate) in summer. Concentration of organic matter (OM) in winter was higher than that in summer; therefore, ambient OM in the sampling site was originated mainly from primary sources. Most of trace metal concentrations were high in winter and low in summer, however, vanadium and nickel concentrations in summer was higher than those in winter. We suggested that one of the reasons of the fact was due to increase of the use of oil fuel for power generation in summer season.
In order to investigate the sources and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs) in aerosol particles in the urban atmosphere of Kumamoto, Japan, atmospheric particles were collected by using two high volume air samplers at a roadside site and a residential site during December 2003 ∼ May 2004, and 16 major PAHs in the samples were analyzed with GC-MS. It was confirmed that the PAHs were mainly from diesel and gasoline engines as expected at both sites. At the roadside site, the total concentration of the 16 PAHs was 10.08 ∼ 99.12 ng m-3 with the average 46.60 ng m-3. At the residential site it was 11.68 ∼ 60.93 ng m-3 with the average 30.03 ng m-3, which is apparently smaller than that at the roadside site. However, the carcinogenicity of the particulate PAHs at the residential site was approximately at the same level as that at the roadside site. Benzo(b)fluoranthene (BbF) , Benzo(k)fluoranthene (BkF) and Dibenzo(a.h)anthracene (DahA) were the major contributors to the carcinogenicity. The concentration of DahA was much smaller than that of BbF and BkF at both sites, but it was considerably larger at the residential site than at the roadside site, which made the carcinogenicity at the residential site comparable to that at the roadside site.
Simulation of droplet formation by the breakdown of two-phase jet ejected into air is conducted with Volume of Fluid (VOF) method supplied by Computational Fluid Dynamic Package (CFD, Fluent ver. 6.1) for studying the generation of monodisperse droplets. Studied is the system where an oil jet sheathed with water is ejected into air and breaks down into droplets under the influence of acceleration force. The simulation results showed that the dimensionless parameter Da/V2 where D is the nozzle diameter, a the acceleration of jet, V the ejection velocity of liquid is a dominative parameter for determining the droplet size. VOF is one of the useful tools in finding governing dimensional parameters for the generation of droplets through the breakdown of two-liquid jet.
The sticking probabilities of a water molecule to a water cluster at several temperatures are calculated as a function of cluster size by using the models proposed for dissociation and stabilization rate constants of vibrationally excited clusters. The model for dissociation is built from RRK theory, while the model for stabilization is based on the general equation describing V → T relaxation rates of diatomic molecules. The sticking probabilities calculated are strongly dependent on the size of the water clusters. They increase from zero to levels close to unity in the cluster-size region of 3 through approximately 20 and keep constant at levels close to unity at a cluster size larger than 20 at 253, 273, and 300 K.