This Colloquium was initiated by the AF Cambridge Research Laboratories to stimulate interest and encourage activity in a field which has tremendous research opportunities. In the small group indicated above, a free flow of thoughts definitely delimited the small extent of current knowledge in the field of Mesospheric Physics and indicated the large area where active research is vitally necessary.
The Colloquium was opened by the topic "Mesospheric Properties" under the chairmanship of F. L. Whipple. The enormous difficulties involved in the obtainment of samples of the upper atmosphere for a determination of constitution were discussed. A novel method of employing a balloon-or rocketborne liquid hydrogen trap which could be opened at definite levels and thereby provide frozen air samples from given altitudes was mentioned. The complicating effects of absorption and adsorption by the container in the usual sampling procedure, or of the heat of association (in the case of atomic oxygen) upon the frozen sampling methods were brought out. The possibility of employing a vehicle-borne mass spectrograph for determination of composition was also examined. While it was thought that water vapor is largely dissociated at about 75 km. and above, detailed theoretical studies on the composition supplemented by experimental results are desirable. The use of interference filters in the infrared to study water vapor was proposed.
Meteor observations currently indicate higher atmospheric number densities in the region 50-90 km. than those determined directly by means of rockets. A seasonal and latitudinal variation in the number density of the atmosphere at higher altitudes probably exists. With respect to noctilucent clouds, if water vapor is dissociated at the level concerned, meteoric flotsam or cosmic dust