Titan, the largest moon of Saturn, has a dense atmosphere whose upper layers are mainly composed of methane (CH4) and molecular nitrogen (N2). The Cassini mission revealed that the interaction between those molecules and the solar VUV radiation, as well as the electrons from Saturn’s magnetosphere, leads to a complex chemistry above an altitude of 800km [1]; [2]; [3]; [4]. Cassini instruments s...

Measurements of the diurnal cycle of potassium (K) atoms between 80 and 110 km have been made during October (for the years 2004-2011) using a Doppler lidar at Kühlungsborn, Germany (54.1°N, 11.7°E). A pronounced diurnal variation is observed in the K number density, which is explored by using a detailed description of the neutral and ionized chemistry of K in a three-dimensional chemistry clim...

Many aspects of the nitrogen fixation process by photochemistry in the Titan atmosphere are not fully understood. The recent Cassini mission revealed organic aerosol formation in the upper atmosphere of Titan. It is not clear, however, how much and by what mechanism nitrogen is incorporated in Titan's organic aerosols. Using tunable synchrotron radiation at the Advanced Light Source, we demonst...

The hydrocarbon photochemistry in the upper atmosphere of Jupiter is investigated using a one-dimensional, photochemical-diffusive, and diurnally averaged model. The important chemical cycles and pathways among the major species are outlined and a standard model for the North Equatorial Belt region is examined in detail. It is found that several traditionally dominant chemical pathways among ...

Introduction: Knowledge of the structure and composition of the upper atmosphere of the giant planets is critical to a better understanding of thermospheric heat sources, radiative transport, methane photochemistry, and chemical-dynamical balance in the atmospheres of these planets, as well as being critical for planning future missions that involve deep atmospheric probes or aerobraking. Altho...

Atomic hydrogen escaping from the extrasolar giant planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. In fact, the upper atmosphere of this planet is evaporating. Observational evidences and interpretations coming from various models are reviewed. Implications for exoplanetology are discussed.

Cirrus clouds are composed of ice crystals condensed from humidity due to low temperature condition in the upper atmosphere. The microphysics of cirrus clouds including sizes and shapes of ice particles are not well understood but are important in climate modeling. Ice crystal will fall under gravitational sedimentation to reach terminal velocities which depend on the size, mass, and ice habit....

Atomic hydrogen escaping from the extrasolar giant planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. In fact, the upper atmosphere of this planet is evaporating. Observational evidences and interpretations coming from various models are reviewed. Implications for exoplanetology are discussed.

Jupiter’s upper atmosphere forms the boundary between the lower atmosphere and interplanetary space. As the topmost layer, the thermosphere absorbs solar extreme ultraviolet (EUV) radiation and charged particles from the magnetosphere that cause dissociation and ionization of thermospheric molecules. Subsequent chemistry establishes the ionosphere and the densities of minor, photoand electroche...