This thesis consists of inteferometric observation of carbon monoxide fromthree planetary atmospheres. The observations address specific questions about thestate and structure of each atmosphere. The analysis and results for each planetarybody are contained within individual chapters of the thesis and the abstract for eachis reproduced below.
Titan: Evidence for Well-Mixed Vertical Profile
We report on new millimeter heterodyne observations of the ^(12)CO J(1 - 0)rotational transition from the stratosphere of Titan made in October 1994 with theOwens Valley Radio Observatory Millimeter Array. The spectrum obtained clearlyexhibits a strong emission core over the ~600 MHz bandwidth of the upper sidebandspectrometer. The lineshape, referenced to the flat spectrum simultaneously observedin the lower sideband was inverted to determine a best fit CO mixing ratio profileconsistent with the observations. The bet fit profile is a constant mixing ratio of 5 ± 1 x 10^(-5) over the altitude range of 60- 200 km. Combined with IR observationof tropospheric CO (ƒco = 6 x 10^(-5), Lutz et al. 1983) this provides strong evidencethat CO is well mixed from the surface to at least 200 km in Titan’s atmosphere.
Mars: Thermal Structure from 0-70 km
Millimeter-wave heterodyne observations of the ^(12)CO J (l - 0) rotational transitionfrom the atmosphere of Mars were made on three dates in February 1993 withthe Owens Valley Radio Observatory Millimeter Array. These observations yieldedhigh-quality spectra with a spatial resolution of 4.2" on a 12.5" diameter Mars. Thespectra were numerically inverted for profiles of the local atmospheric temperaturefrom 0 to 70 km, assuming a constant CO mixing ratio for the atmosphere. Thederived average low latitude atmospheric temperature profile is approximately 20 Kcooler than reference temperature profiles compiled during the Viking era. This newtemperature profile is well-matched by cooler profiles determined from whole disk COmeasurements, suggesting very little dust loading of the atmosphere at the time ofthe observations (Clancy et al. 1990). In addition, the revealed thermal structureshows variation with latitude, and these temperature profiles compare well with profilesderived from Mariner 9 IRIS observations (Leovy 1982, Santee and Crisp 1993) and calculated thermal structure from the Mars General Circulation Model (Haberleet al.. 1993). The temperature profiles were averaged in local time and the resultingcross-section of temperature as a function of pressure and latitude used to infer themean zonal circulation of the atmosphere. These wind results are somewhat compromisedby the relatively low spatial resolution of the observation but do qualitativelymatch both inferred zonal winds from the Mariner 9 IRIS observations and MarsGCM calculations. These initial observations point toward the desirability of furtherinterferometric measurements.
Venus: Temporal Variations of the Mesophere
Millimeter-wave heterodyne observations of the ^(12)CO J(1-0) rotational transitionfrom the mesosphere of Venus were made in early November and early December1994 with the Owens Valley Radio Observatory Millimeter Array. The spatial resolute ion for each day was about 1000 km at the sub-earth point. The high quality COspectra were numerically inverted for profiles of the local CO mixing ratio from 80to 105 km, assuming a Pioneer Venus mean temperature profile for the atmosphere.For each day the revealed CO distribution shows a nightside maximum centered atlow latitudes and shifted from the anti-solar point toward the morning terminator.Both clays show a clear latitudinal falloff in the CO abundance. In November themaximum was centered at roughly 2^h local time at 100 km, while in December themaximum was at roughly 4 – 4.5^h local time at 100 km. In addition, CO abundanceswere slightly higher in November. The changes in the CO distribution areexamined in the context of the mesospheric circulation model of Clancy and Muhleman(1985b). The increased shift away from the anti-solar point and decreased COabundance for the December observations both point toward increased zonal and/ordecreased sub-solar to anti-solar circulation within the mesosphere during the monthbetween observations.
