Planetary surfaces

Abstract:

An analysis of thermal profiles and dynamics over a wide range of latitudes for the venusian atmosphere between 70 and 90 km is presented based on high spatial resolution infrared spectra of the night side obtained by the near infrared mapping spectrometer (NIMS) experiment during the Galileo-Venus encounter in February 1990. Using the 4.3-μm CO2 absorption band, the temperature profile is retrieved in the 75- to 91-km altitude region over a latitudinal range of -59· to + 64·. Compared to earlier observations from the Pioneer Venus mission, the temperature at 91 km is about 10 K higher and between 74 and 83 km about 3.6 K colder. An equator to pole warming at constant pressure levels is found and implications for the zonal wind profiles are drawn under the assumption that the atmosphere is in cyclostrophic balance in the region of 70 to 90 km. The results are in correspondence with direct wind measurements from ground-based observations at 95 km and 105 km altitude. © 1995 Academic Press, Inc.

Abstract:

A short description is given of the Occultation Radiometer which has been flown recently on the EURECA carrier. A brief outline of the scientific rationale, instrument characteristics and status of the data reduction is presented.

Abstract:

Venus as a planet resembles the Earth, but has a much hotter and denser atmosphere due to an extreme case of the greenhouse effect, caused by compositional differences and tile thick cloud cover. Studies of the lower atmosphere are inhibited by the cloud opacity, which makes remote measurements at most frequencies short. of the radio range quite difficult. Progress in understanding of the com position and thermal structure below the clouds has been made by the Pioneer and Venera entry probes of the 1970s, and more recently with results from the Galileo fly-by in 1990. The latter exploited the newly discovered near-infrared 'windows' to achieve measurements of carbon monoxide and water vapour abundances in the deep atmosphere, and provided the first detailed view of the global cloud structure. The morphology and spatial variations seen in the main mass of clouds are remarkable, and suggest a powerful and diverse meteorology dominated by convection. Carbon monoxide is significantly more abundant at high northern latitudes than at low latitudes in either hemisphere.