Panayotis Lavvas

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0019-1035/$ see front matter 2010 Elsevier Inc. A doi:10.1016/j.icarus.2010.07.025 ⇑ Corresponding author. Fax: +1 520 621 4933. E-mail address: lavvas@lpl.arizona.edu (P. Lavvas) We present a one dimension simulation of Titan’s aerosol distribution and compare our results with the haze optical properties retrieved by the DISR observations (Tomasko, M.G.,(More)
Titan has long been known to harbour the richest atmospheric chemistry in the Solar System. Until recently, it had been believed that complex hydrocarbons and nitriles were produced through neutral chemistry that would eventually lead to the formation of micrometre sized organic aerosols. However, recent measurements by the Cassini spacecraft are(More)
The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism(More)
Experimental simulations of the initial steps of the ion-molecule reactions occurring in the ionosphere of Titan were performed at the synchrotron source Elettra in Italy. The measurements consisted of irradiating gas mixtures with a monochromatic photon beam, from the methane ionization threshold at 12.6 eV, up to and beyond the molecular nitrogen(More)
Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. Whereas the lower atmosphere (at altitudes of less than 200 kilometers) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen(More)
We use a stochastic approach in order to investigate the production and evolution of aerosols in Titan’s atmosphere. The simulation initiates from the benzene molecules observed in the thermosphere and follows their evolution to larger aromatic structures through reaction with gas phase radical species. Aromatics are allowed to collide and provide the first(More)
The large abundance of NH3 in Titan's upper atmosphere is a consequence of coupled ion and neutral chemistry. The density of NH3 is inferred from the measured abundance of NH4+. NH3 is produced primarily through reaction of NH2 with H2CN, a process neglected in previous models. NH2 is produced by several reactions including electron recombination of(More)
[1] We present in this paper an investigation of the distribution of H2 in Titan’s exosphere, based on the measurements made with the Ion Neutral Mass Spectrometer (INMS) onboard Cassini during 32 encounters with the satellite. The observedH2 density in Titan’s exosphere shows significant variance from flyby to flyby. However, no appreciable trend with(More)
Department of Physics, Imperial College, London SW7 2AZ, UK b Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092, USA c School of Astronomy and Space Sciences, Nanjing University, Nanjing 210008, China National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China e Swedish Institute of Space Physics,(More)