Search Publications
Jupiter's Cloud Structure as Constrained by Galileo Probe and HST Observations
Sromovsky, L. A.; Fry, P. M.
The Galileo Probe sampled Jupiter's atmosphere at the edge of a 5-µm hot spot, where it found very little cloud opacity above the 700 mb level. Only τ=1-2 at λ=0.5 µm was inferred from Net Flux Radiometer observations (Sromovsky et al. 1998, J. Geophys. Res.103, 22,929-22,977), in seeming conflict with Chanover et al. (1997, Icarus128,…
Photoelectric Charging of Submicron Aerosols and Macromolecules in the Titan Haze
McKay, Christopher P.; Bakes, E. L. O.; Bauschlicher, Charles W.
We quantify the charge states of submicrometer aerosols and aromatic macromolecules in Titan's organic haze. The aerosol charge is balanced between the recombination of positive ions with the aerosol plus the ejection of electrons from the aerosol via the UV-driven photoelectric effect and the recombination of electrons with the aerosol. During th…
Keck Adaptive Optics Images of Uranus and Its Rings
de Pater, Imke; Roe, H. G.; Max, C. E. +3 more
We present adaptive optic images of Uranus obtained with the 10-m W. M. Keck II telescope in June 2000, at wavelengths between 1 and 2.4 µm. The angular resolution of the images is ∼0.06-0.09″. We identified eight small cloud features on Uranus's disk, four of which were in the northern hemisphere. The latter features are ∼1000-2000 km in ex…
Methane Abundance on Titan, Measured by the Space Telescope Imaging Spectrograph
Lorenz, Ralph D.; Lemmon, Mark T.; Smith, Peter H.
Although methane is the dominant absorber in Titan's reflection spectrum, the amount of methane in the atmosphere has only been determined to an order of magnitude. We analyzed spectra from the Space Telescope Imaging Spectrograph, looking at both a bright surface region (700-km radius) and a dark surface region. The difference between the spectra…
A Comparative Study of Jovian Anticyclone Properties from a Six-Year (1994-2000) Survey
Colas, F.; Lecacheux, J.; Morales-Juberías, Raúl +1 more
We have used the Hubble Space Telescope archived images of Jupiter for the period 1994-2000, complemented by ground-based telescopic observations, to study in detail the long-term properties of synoptic-scale anticyclonic vortices (size > 1500 km, lifetime > months). We have also analyzed a set of Voyager 1 and 2 images obtained in 1979 to c…
Sungrazing Comets: Properties of Nuclei and in Situ Detectability of Cometary Ions at 1 AU
Bochsler, P.; Küppers, M.; Benz, W. +1 more
A one-dimensional sublimation model for cometary nuclei is used to derive size limits for the nuclei of sungrazing comets and to estimate oxygen ion fluxes at 1 AU from their evaporation. Given that none of the ≈300 sungrazers detected by the SOlar and Heliospheric Observatory (SOHO) was observed after disappearing behind the sun, and that small n…
Spatially Resolved Far Ultraviolet Spectroscopy of the Jovian Aurora
Clarke, J. T.; Grodent, D.; Gérard, J. C. +1 more
Spatially resolved spectra in four 50-Å FUV spectral windows were obtained across the jovian aurora with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope. Nearly simultaneous ultraviolet imaging makes it possible to correlate the intensity variations along the STIS slit with those observed in the images and to ch…
The Unusual Dynamics of Northern Dark Spots on Neptune
Baines, K. H.; Sromovsky, L. A.; Fry, P. M.
Hubble Space Telescope (HST) and ground-based observations of Neptune from 1991 to 2000 show that Neptune's northern Great Dark Spots (NGDS) remained remarkably stable in latitude and longitudinal drift rate, in marked contrast to the 1989 southern Great Dark Spot (GDS), which moved continuously equatorward during 1989 and dissipated unseen during…
A Comparative Study of Jovian Cyclonic Features from a Six-Year (1994-2000) Survey
Colas, F.; Sánchez-Lavega, Agustín.; Lecacheux, J. +1 more
This work presents a six-year study aimed at characterizing the morphology and properties of the atmospheric features present in jovian cyclonic regions. It complements our previous analysis for the same period on the anticyclonic vortices (Morales-Juberias et al. 2002, Icarus 157, 76-90). The main difference between cyclonic and anticyclonic regi…
Aging of Titan's Aerosols
Dimitrov, Vasili; Bar-Nun, Akiva
Titan's haze is composed of aerosols containing long chain polymers of acetylene with some hydrogen cyanide. These polymers have alternating double/single and triple/single bonds, which can open spontaneously or under the action of UV radiation or particle impact. Once opened, they can induce the opening of a double or triple bond in an adjacent c…