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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.02.009 Byline: Arielle Moullet (a), Mark A. Gurwell (a), Emmanuel Lellouch (b), RaphaA'l Moreno (b) Keywords: IO; Radio observations; Atmospheres, Structure Abstract: Many of the key properties of Io's atmosphere, such as its spatial distribution, temperature, column density and composition, are still not fully assessed despite decades of extensive observations. The contribution of the possible gas sources to the atmospheric replenishment are then still unclear. This paper presents disk-resolved observations performed with the Submillimeter Array (SMA) at 345GHz of atmospheric rotational lines of the main atmospheric species SO.sub.2, and, for the first time, of the minor species SO and NaCl. All these species appear concentrated on the anti-jovian hemisphere, but do not share the same spatial distribution. The obtained maps and line-averaged fluxes are compared to realistic models simulating gas sources including volcanic plume outgassing, SO.sub.2 frost sublimation and photolysis. Arguments in favor of each sources are examined and compared to observations, putting constraints on their relative roles for each species. While sublimation clearly appears as the favored major source for SO.sub.2, SO.sub.2 photolysis may account for most of the production of SO. Using constraints on the volcanic plumes distribution from Galileo results, we find that direct volcanic input can only contribute for a minor fraction of atmospheric SO.sub.2, but represent a more significant source for SO atmosphere, and is likely to be the only source for NaCl. Temperature and column densities findings are also presented for SO.sub.2, and compare well to previously published observations and atmospheric models. Author Affiliation: (a) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA (b) LESIA-Observatoire de Paris, Meudon F-02195, France Article History: Received 9 November 2009; Revised 20 January 2010; Accepted 9 February 2010

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.12.004 Byline: Mark A. Gurwell (a), Gary J. Melnick (a), Volker Tolls (a), Edwin A. Bergin (b), Brian M. Patten (a) Keywords: Venus; atmosphere; Abundances; atmospheres; Radio observations; Atmospheres; structure Abstract: We present the first detections of the ground-state H.sub.2.sup.16O (1.sub.10-1.sub.01) rotational transition (at 556.9 GHz) and the.sup.13CO (5-4) rotational transition from the atmosphere of Venus, measured with the Submillimeter Wave Astronomy Satellite (SWAS). The observed spectral features of these submillimeter transitions originate primarily from the 70-100 km altitude range, within the Venus mesosphere. Observations were obtained in December 2002, and January, March, and July 2004, coarsely sampling one Venus diurnal period as seen from Earth. The measured water vapor absorption line depth shows large variability among the four observing periods, with strong detections of the line in December 2002 and July 2004, and no detections in January and March 2004. Retrieval of atmospheric parameters was performed using a multi-transition inversion algorithm, combining simultaneous retrievals of temperature, carbon monoxide, and water profiles under imposed constraints. Analysis of the SWAS spectra resulted in measurements or upper limits for the globally averaged mesospheric water vapor abundance for each of the four observation periods, finding variability over at least two orders of magnitude. The results are consistent with both temporal and diurnal variability, but with short-term fluctuations clearly dominating. These results are fully consistent with the long-term study of mesospheric water vapor from millimeter and submillimeter observations of HDO [Sandor, B.J., Clancy, R.T., 2005. Icarus 177, 129-143]. The December 2002 observations detected very rapid change in the mesospheric water abundance. Over five days, a deep water absorption feature consistent with a water vapor abundance of 4.5[+ or -]1.5 parts per million suddenly gave way to a significantly shallower absorption, implying a decrease in the water vapor abundance by a factor of nearly 50 in less that 48 h. In 2004, similar changes in the water vapor abundance were measured between the March and July SWAS observing periods, but variability on time scales of less than a week was not detected. The mesospheric water vapor is expected to be in equilibrium with aerosol particles, primarily composed of concentrated sulfuric acid, in the upper haze layers of the Venus atmosphere. If true, moderate amplitude (10-15 K) variability in mesospheric temperature, previously noted in millimeter spectroscopy observations of Venus, can explain the rapid water vapor variability detected by SWAS. Author Affiliation: (a) Harvard-Smithsonian Center for Astrophysics, MS 42, 60 Garden Street, Cambridge, MA 02138, USA (b) University of Michigan, Department of Astronomy, 830 Dennison Building, Ann Arbor, MI 48109, USA Article History: Received 10 May 2006; Revised 30 November 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2004.10.009 Byline: Mark A. Gurwell (a), Edwin A. Bergin (b), Gary J. Melnick (a), Volker Tolls (a) Abstract: The dramatic growth and evolution of the 2001 martian global dust storm were captured using the Submillimeter Wave Astronomy Satellite (SWAS). While the lower and middle atmosphere (pressures greater than 50 [mu]bar, up to [approximately equal to]45 km altitude) showed rapid heating of up to 40 K, the average surface brightness temperature plummeted by [approximately equal to]20 K at the peak of the storm. The storm appears to have had little impact on the global temperature structure at altitudes above [approximately equal to]10 [mu]bar ([approximately equal to]60 km). Author Affiliation: (a) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA (b) University of Michigan, Department of Astronomy, 830 Dennison Building, Ann Arbor, MI 48109, USA

We report on new microwave heterodyne observations of the CO J(1-0) rotational transition from the stratosphere of Titan made in October 1994 with the Owens Valley Radio Observatory millimeter array. The spectrum obtained clearly exhibits a strong emission core over the [is nearly equal to] 600-MHz bandwidth of the upper sideband spectrometer. The lineshape, referenced to the flat spectrum simultaneously observed in the lower sideband, was inverted to determine a best fit CO mixing ratio profile consistent with the observations. The best fit profile is a constant mixing ratio of 5 [+ or -] 1 x [10.sup.-5] over the altitude range of 60-200 km. Combined with IR observations of tropospheric CO at 6 x [10.sup.-5] (B. L. Lutz et al. 1983, Science 220, 1374-1375), this result provides strong evidence that CO is well mixed from the surface to at least 200 km in Titan's atmosphere.

Owens Valley Radio Observatory's Caltech Millimeter Wave Interferometer was used to observe carbon monoxide (CO) in Venus' upper mesosphere in 1986 and 1988. The interferometer yielded high-quality, disk-resolved spectra, which, when inverted, allowed the CO mixing ratio profile in different regions to be determined. A qualitative model of mesospheric circulation in Venus was used to explain a shift in the CO maximum on the mesosphere's nightside.

Abstract: Many of the key properties of Io’s atmosphere, such as its spatial distribution, temperature, column density and composition, are still not fully assessed despite decades of extensive observations. The contribution of the possible gas sources to the atmospheric replenishment are then still unclear. This paper presents disk-resolved observations performed with the Submillimeter Array (SMA) at 345GHz of atmospheric rotational lines of the main atmospheric species SO2, and, for the first time, of the minor species SO and NaCl. All these species appear concentrated on the anti-jovian hemisphere, but do not share the same spatial distribution. The obtained maps and line-averaged fluxes are compared to realistic models simulating gas sources including volcanic plume outgassing, SO2 frost sublimation and photolysis. Arguments in favor of each sources are examined and compared to observations, putting constraints on their relative roles for each species. While sublimation clearly appears as the favored major source for SO2, SO2 photolysis may account for most of the production of SO. Using constraints on the volcanic plumes distribution from Galileo results, we find that direct volcanic input can only contribute for a minor fraction of atmospheric SO2, but represent a more significant source for SO atmosphere, and is likely to be the only source for NaCl. Temperature and column densities findings are also presented for SO2, and compare well to previously published observations and atmospheric models. [Copyright &y& Elsevier]