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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.02.003 Byline: Glenn S. Orton (a), Magnus Gustafsson (b), Martin Burgdorf (c), Victoria Meadows (d) Keywords: Atmospheres; structure; Uranus; Neptune; Infrared observations; Spectroscopy Abstract: A revised ab initio calculation of the H.sub.2-H.sub.2 collision-induced absorption results in significant differences compared with the work of J. Borysow et al. [Borysow, J., Trafton, L., Frommhold, L., Birnbaum, G., 1985. Astrophys. J. 296, 644-654] for wavenumbers greater than 600 cm.sup.-1 and temperatures below 120 K. The revision has significant influence on the spectra of Uranus and Neptune, and essentially removes the need for models with 'super-solar' helium abundances or stratospheric hazes to explain the spectrum of Uranus. Author Affiliation: (a) MS 169-237, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA (b) Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA (c) Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD, UK (d) Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125, USA Article History: Received 21 November 2006; Revised 25 January 2007

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.08.025 Byline: Brigette E. Hesman (a), Gary R. Davis (b), Henry E. Matthews (c), Glenn S. Orton (d) Keywords: Abundances; atmospheres; Neptune; atmosphere; Radiative transfer; Spectroscopy Abstract: The Ja=a3-2 rotational line of CO in Neptune has been measured using the heterodyne receiver B3 at the JCMT. The spectral resolution was 1.25 MHz and 25 tunings were used to cover a frequency range of almost 20 GHz. The measured line shape, encompassing both the broad absorption feature arising in the lower atmosphere and a narrow emission core from the upper stratosphere, indicates that the CO mole ratio is not uniform with altitude, with best-fit values of 2.2.sub.-0.4.sup.+0.6x10.sup.-6 in the upper stratosphere and 0.6[+ or -]0.4x10.sup.-6 in the lower stratosphere and troposphere. The higher stratospheric abundance indicates that a dual, internal and external, origin of CO is most likely. Author Affiliation: (a) University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada (b) Joint Astronomy Centre, 660 N. A'ohoku Place, University Park, Hilo, HI 96720, USA (c) National Research Council of Canada, HIA, Victoria, BC V9E 2E7, Canada (d) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA Article History: Received 30 June 2005; Revised 29 August 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.08.009 Byline: Amy A. Simon-Miller (a), Bradley W. Poston (b), Glenn S. Orton (c), Brendan Fisher (c) Keywords: Jupiter; atmosphere; Atmospheres; dynamics; Infrared observations Abstract: Jupiter's equatorial atmosphere, much like the Earth's, is known to show quasi-periodic variations in temperature, particularly in the stratosphere, but variations in other jovian atmospheric tracers have not been studied for any correlations to these oscillations. Data taken at NASA's Infrared Telescope Facility (IRTF) from 1979 to 2000 were used to obtain temperatures at two levels in the atmosphere, corresponding to the upper troposphere (250 mbar) and to the stratosphere (20 mbar). We find that the data show periodic signals at latitudes corresponding to the troposphere zonal wind jets, with periods ranging from 4.4 (stratosphere, 95% confidence at 4[degrees] S planetographic latitude) to 7.7 years (troposphere, 97% confidence at 6[degrees] N). We also discuss evidence that at some latitudes the troposphere temperature variations are out of phase from the stratosphere variations, even where no periodicity is evident. Hubble Space Telescope images were used, in conjunction with Voyager and Cassini data, to track small changes in the troposphere zonal winds from 20[degrees] N to 20[degrees] S latitude over the 1994-2000 time period. Oscillations with a period of 4.5 years are found near 7[degrees]-8[degrees] S, with 80-85% significance. Further, the strongest evidence for a QQO-induced tropospheric wind change tied to stratospheric temperature change occurs near these latitudes, though tropospheric temperatures show little periodicity here. Comparison of thermal winds and measured zonal winds for three dates indicate that cloud features at other latitudes are likely tracked at pressures that can vary by up to a few hundred millibar, but the cloud altitude change required is too large to explain the wind changes measured at 7[degrees] S. Author Affiliation: (a) NASA's Goddard Space Flight Center, Code 693.0, Greenbelt, MD 20771, USA (b) University of Maryland College Park, 1208B Cambridge Hall, College Park, MD 20742, USA (c) Jet Propulsion Laboratory, 4800 Oak Grove Road, M/S 169-237, Pasadena, CA 91109, USA Article History: Received 24 February 2006; Revised 3 August 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.08.002 Byline: Amy A. Simon-Miller (a), Nancy J. Chanover (b), Glenn S. Orton (c), Michael Sussman (b), Irene G. Tsavaris (d), Erich Karkoschka (e) Keywords: Jupiter, atmosphere; Atmospheres, dynamics Abstract: Jupiter's remaining White Oval changed color in late 2005 and became noticeably red in early 2006, as reported by amateur observers. We present wind and color analyses from high spatial resolution images taken with the Hubble Space Telescope Advanced Camera for Surveys in April 2006. These images suggest that the recent color change was tied to a strengthening of this storm, as implied by increased vorticity, causing it to become more like the Great Red Spot. From a historical perspective, the current activity may be consistent with the generation of new anticyclones at this latitude in the coming months and years. Author Affiliation: (a) NASA Goddard Space Flight Center, Code 693.0, Greenbelt, MD 20771, USA (b) New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003, USA (c) Jet Propulsion Laboratory, 4800 Oak Grove Road, M/S 169-237, Pasadena, CA 91109, USA (d) University of Maryland, College Park Scholars, 1208B Cumberland Hall, College Park, MD 20742, USA (e) Department of Planetary Sciences & Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA Article History: Received 9 May 2006; Revised 7 August 2006 Article Note: (footnote) [star] Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO10192, GO10782 and GO10783.

Retrievals performed on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby in 2000/2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere, but to higher latitudes than were shown previously by Flasar et al. [Flasar, F.M., 39 colleagues, 2004a. Nature 427, 132-135, Flasar, F.M., 44 colleagues, 2004b. Space Sci. Rev. 115, 169-297]. Similar retrievals were performed on Voyager 1 IRIS data to provide the first detailed IRIS map of the stratosphere, and high latitudes in the troposphere. Thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes, and meridional temperature gradients indicate the presence of circumpolar jets, as well. The temperatures retrieved from the two spacecraft were also compared with yearly ground-based data obtained over the intervening two decades. Tropospheric temperatures reveal gradual changes at low latitudes, with little obvious seasonal or short-term variation [Orton et al., 1994. Science 265, 625-631]. Stratospheric temperatures show much more complicated behavior over short timescales, consistent with quasi-quadrennial oscillations at low latitudes, as suggested in prior analyses of shorter intervals of ground-based data [Orton et al., 1991. Science 252, 537-542; Friedson, A.J., 1999. Icarus 137, 34-55]. A scaling analysis indicates that meridional motions, mechanically forced by wave or eddy convergence, play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter timescales. At latitudes away from the equator, the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative. Ground-based observations with improved vertical resolution and/or long-term monitoring from spacecraft are required for this purpose, though the Voyager and Cassini data given indications that the magnitude of the forcing is very small. Keywords: Jupiter, atmosphere; Atmospheres, dynamics; Atmospheres, temperature

Neptune was observed by the Infrared Space Observatory (ISO) Long-Wavelength Spectrometer (LWS) between 46 and 185 [micro]m. At wavelengths between 50 and 110 pm the accuracy of these measurements is [less than or equal to] 0.3 K. Observations of this planet made by the ISO Short-Wavelength Spectrometer between 28 and 44 gm were combined with the LWS data to determine a disk-averaged temperature profile and derive several physical quantities. The combined spectra are matched best by a He/([H.sub.2] + He) mass ratio of [26.4.sup.+2.6.sub.-3.5]%, reflecting a He molar fraction of [14.9.sup.+1.7.sub.-2.2]%, assuming the molar fraction of C[H.sub.4] to be 2% in the troposphere. This He abundance is consistent with one derived from analysis of joint Voyager-2 IRIS and radio occultation experiment data, a technique whose accuracy has recently been called into question. For a disk average, the para-[H.sub.2] fraction is found to be no more than ~ 1.5% different from its equilibrium value, and the [N.sub.2] mixing ratio is probably less than 0.7%. The composite spectrum is best fit by invoking a C[H.sub.4] ice condensate cloud. Using a Mie approximation to particle scattering and absorption, best-fit particle sizes lie between 15 and 40 pm. The composite spectra are relatively insensitive to the vertical distribution of the cloud, but the particle scale height must be greater than 5% of the gas scale height. The best models are consistent with an effective temperature for Neptune that is 59.5 [+ or -] 0.6 K, a value slightly lower than derived by the Voyager IRIS experiment--possibly Neptune's mid- and far-infrared emission has changed during the seven years that lie between its encounter with Voyager 2 and the first spectra taken of this planet with ISO. The model spectra are also ostensibly lower than ground-based observations in the spectral range of 17-24 [micro]m, but this discrepancy can be relieved by perturbing the temperature of the lower stratosphere where the LWS spectrum is not particularly sensitive, combined with the uncertainty in the absolute calibration of the ground-based measurements. Keywords: Infrared observations; Neptune; Abundances; Atmospheres; Spectrophotometry

During the first six orbits of the Galileo spacecraft's prime mission, the Solid State Imaging (SSI) system acquired multispectral image mosaics of Jupiter's Great Red Spot, an equatorial belt/zone boundary, a '5-[[micro]meter] hot spot' similar to the Galileo Probe entry site, and two of the classic White Ovals. We present mosaics of each region, approximating their appearance at visible wavelengths and showing cloud height and opacity variations. The local wind field is derived by tracking cloud motions between multiple observations of each region with time separations of roughly 1 and 10 hr. Vertical cloud structure is derived in a companion paper by Banfield et al. (Icarus 135, 230-250). Galileo's brief, high-resolution observations complement Earth-based and Voyager studies and offer local meteorological context for the Galileo Probe results. Our results show that the dynamics of the zonal jets and large vortices have changed little since Voyager, with a few exceptions. We detect a cyclonic current within the center of the predominantly anticyclonic Great Red Spot. The zonal velocity difference between 0 [degrees] S and 6 [degrees] S has increased by 20 m [sec.sup.-1]. We measure a strong northeast flow approaching the hot spot. This flow indicates either massive horizontal convergence or the presence of a large anticyclonic vortex southeast of the hot spot. The current compact arrangement of two White Ovals and a cyclonic structure greatly perturbs the zonal jets in that region. Key Words: Jupiter atmosphere; atmospheric dynamics; image processing; spacecraft.

Infrared spectra of Jupiter's atmosphere were obtained with the infrared spectrometer (IRS) on the 1.5-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) during the first 2 days of the impacts of the fragments of Comet Shoemaker-Levy 9 (1993e). We monitored 3.51 [+ or -] 0.17/[[micro]meter] radiation from the impact areas, undisturbed areas, and auroral regions of Jupiter after the A and E impacts. The strong emission of a portion of the P-branch of the [v.sub.3] band of C[H.sub.4] was detected on the A impact area 4 hr after the impact. [Mathematical Expression Omitted] emissions are found to be decreased at the A and E impact sites after 4 hr and 10 hr 50 min of the impacts, respectively, compared with undisturbed areas at the same latitude. The temperatures of the southern [Mathematical Expression Omitted] aurora were normal within the first several hours following the A and E impacts.

The optical constants [n.sub.r] + i[n.sub.i] of liquid methane and phase I solid methane were determined over the entire spectral range by the use of various data sources published in the literature. Kramers-Kronig analyses were performed on the absorption spectra of liquid methane at the boiling point (111 K) and the melting point (90 K) and on the absorption spectra of phase I solid methane at the melting point and at 30 K. Measurements of the static dielectric constant at these temperatures and refractive indices determined over limited spectral ranges were used as constraints in the analyses. Applications of methane optical properties to studies of outer solar system bodies are described.

Ethane emission variation on Neptune is examined using previous 7-14 micrometer spectrometric data. The ratio of ethane to methane emission increased by a factor near 1.47 between 1985 and 1991, due more to the 12.2 micrometer ethane feature than to the 7.7 micrometer methane feature. The change may be traced to a nonuniform stratospheric thermal increase or a 15% or more rise in ethane concentration.

New 5.2-[micro]m thermal images of Saturn's clouds reveal a strong axisymmetric banded structure centered at 45 [degrees] S with discrete cold spots about 30,000-50,000 km long that: (i) lower the ~180-K brightness temperature by 8-10 K; (ii) rotate at a rate that is consistent with cloud-tracked zonal winds; and (iii) exhibit no correlation with structures seen in reflected sunlight. They are explained by variations of optical thickness of clouds just below the 1-bar level. Key Words: Saturn, atmosphere; jovian planets; radiative transfer; spectrophotometry.

Far-infrared Fourier-transform spectrometer measurements of the 1-0 and 3-2 [PH.sub.3] transitions in Saturn's disk near 267 and 800 GHz (8.9 and 26.7 [cm.sup.-1]), respectively, were analyzed simultaneously to derive a global mean profile for the [PH.sub.3] vertical mixing ratio between 100 and 600 mbar total pressure. The far-infrared spectrum is relatively free from spectral interlopers, suffers minimal absorption or scattering by atmospheric particulates, and contains intrinsically weak [PH.sub.3] lines that are sensitive to a range of atmospheric depths. The combined spectra are inconsistent with a uniform tropospheric mixing ratio, even with a stratospheric cutoff. They are consistent with a volume mixing ratio of [PH.sub.3] that drops from 1.2 x [10.sup.-5] at 645 mbar pressure to a value of 4.1 x [10.sup.-7] at 150 mbar pressure, a decrease that is linear in log abundance vs log pressure. The mixing ratio could drop even more quickly at atmospheric pressures below 150 mbar and still be consistent with the data. The mixing ratio may well remain constant with depth for pressures above 630 mbar. The maximum [PH.sub.3] mixing ratio in this model is consistent with a [P]/[H] ratio in the deep atmosphere that is about a factor of 10 higher than solar composition. Such a model is consistent with rapid mixing up to the radiative-convective boundary and transport by, for example, vertical waves just above this boundary. In the best fitting model, the eddy diffusion coefficient is ~[10.sup.4] [cm.sup.2] near 630 mbar, and it must increase with altitude. The predominant [PH.sub.3] loss mechanisms are direct photolysis by UV radiation and scavenging by H atoms produced by the photolysis. Key Words: atmospheres, composition; photochemistry; Saturn, atmosphere; spectroscopy.

Part II. Studies the multispectral imaging of the Jovian atmosphere based on infrared and ultraviolet wavelength. Summary of the probable layers of the various cloud layers; Polar hoods and anticyclonic ovals; South Equatorial Disturbance.