3 required for supercooling the reactive colls of the hypo gravimetric power generators used on'Arrakis WH ARRAKIS, Atmosphere of before the Atreides COMPOSITION Major gaseous constitu ents were nitrogen (74 32% by mass), oxy gen (23 58%), and argon (1 01%) The most important trace gases were water vapor (less than 0 5%, variable), carbon dioxide (0 035%), and ozone (0 52%) The numerical values are those given by Kynes in his pioneering studies of the planet' Present differences are due to compositional changes that have oc curred over the five intervening millennia and in no way reflect inaccuracies m Kynes' measurements The composition was quite similar to that of other Neta 2C 53B planets except that the amount of ozone was anomalously high and that of water vapor anomalously low The excess ozone was of considerable sigmfi cance to many atmospheric phenomena A notable example is the so-called "Conohs storm'' The role of ozone in this and other aspects of the atmosphere is discussed in subsequent sections Considerable dust was present in the atmosphere at all times This of course, was the result of the dessicated surface and the violent storms that swept the planet The sky thus had an almost uniform dullness due to light scattenng by the dust However, in the polar regions the sky often appeared bluish while in other areas it did so occasionally The atmospheric dust content was within the bounds of the Neta 2C-53B classification PHYSICAL CHARACTERISTICS Surface pressure, mean wind and temperature were also compatible with Neta 2C 53B guidelines e g 1000 5 millibars mean pressure (planetary), 286 2 degrees absolute plane tary mean temperature (annualized), and a mean global wind speed standard height of 20 3 kilometers per hour It should b