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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.2006.05.016 Byline: Frank Bensch (a)(b), Gary J. Melnick (a), David A. Neufeld (c), Martin Harwit (d)(e), Ronald L. Snell (f), Brian M. Patten (a), Volker Tolls (a) Keywords: Comet Tempel-1; Radiative transfer; Radio observations; Comets; coma Abstract: On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the 1.sub.10-1.sub.01 ortho-water ground-state rotational transition in Comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8x10.sup.7kg on the water ice evaporated by the impact. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with Q.sub.H.sub.2O[approximately equal to]10.sup.28molecules.sup.-1 alternated with periods with low outgassing (Q.sub.H.sub.2O[less than or approximately equal to]5x10.sup.27molecules.sup.-1). We estimate that 9P/Tempel 1 vaporized a total of N[approximately equal to]4.5x10.sup.34 water molecules ([approximately equal to]1.3x10.sup.9kg) during June-September 2005. Our observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the comet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates. Author Affiliation: (a) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA (b) Argelander-Institut fur Astronomie, Universitat Bonn, Abteilung Radioastronomie, Auf dem Hugel 71, 53121 Bonn, Germany.sup.1 1 Founded in 2006 by merging of the Sternwarte, Radioastronomisches Institut and Institut fur Astrophysik und Extraterrestrische Forschung der Universitat Bonn. (c) Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA (d) 511 H street, SW, Washington, DC 20024, USA (e) Cornell University, Ithaca, NY 14853, USA (f) Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA Article History: Received 27 January 2006; Revised 17 May 2006

On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the cornet. NASNs Submillimeter Wave Astronomy Satellite (SWAS) observed the [1.sub.10]-[1.sub.01] ortho-water ground-state rotational transition in Cornet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8 x [10.sub.7] kg on the water ice evaporated by the impact. However, the water production rate of the cornet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with [MATHEMATICAL EXPRESSIONS NOT REPRODUCIBLE IN ASCII] ~ [10.sup.28] [molecules.sup.- 1] alternated with periods with low outgassing ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] 5 x [10.sup.27] [ molecule s-.sup.-1]). W that 9P/Tempel I vaporized a total of N ~ 4.5 x [10.sup.34] water molecules (~ 1.3 x [10.sup.9] kg) during June-September 2005. Out observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the cornet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates. Keywords: Cornet Tempel-1; Radiative transfer; Radio observations; Comets, coma

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

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 [micro]bar, up to ~ 45 km altitude) showed rapid heating of up to 40 K, the average surface brightness temperature plummeted by ~ 20 K at the peak of the storm. The storm appears to have had little impact on the global temperature structure at altitudes above ~ 10 [micro]bar (~ 60 km). Keywords: Mars, atmosphere; Radio observations; Atmospheres, structure