e noted that all Neta 2C planets regardless of after-fixes are habitable CLIMATE The climate over most of the planet was best described as hot and dry Sub-freezing temperatures occurred only at the poles where surface temperatures were almost always below the water freezing point Nights were generally cool (in a relative sense) The planet had little in the way of seasons since its orbit about Canopus was nearly circu lar and the planet s axis of rotation was direct ed almost perpendicular to its ecliptic plane Because of this the small polar ice caps appeared to remain unchanged (orbital observation) However extensive scientific stud ics have shown that the caps did exhibit a very slight advance and retreat with the sea sons and hence a slight amount of water vapor was transported between the poles Ptahtercicah (9527) investigated the mecha nisms of water vapor transport in terms of the minimum amount lequired to sustain any ARRAKIS ATMOSPHERE 24 ARRAKIS ATMOSPHERE life The correctness of these theoretical calculations was confirmed using Arrakis as the test case Her work is the base from which the planetary classification system, particularly for Neta class, evolved WEATHER PHENOMENA Thin, cirrus clouds occurred seasonally in the vicinity of the polar caps, but dust clouds (and the generating storms) were the dominant fea tare of Arrakis's weather Every day dust was injected into die atmosphere by small vortex or pseudo-vortex systems Ancient lore tells us that these slender pillars of dust represented the spirits of ancestors However, scientific investigation showed that these manifestations were a result of severe heating of the ground surface with cooler temperatures above and light wind The hot air rose and pulled down the cooler air The presence of a light wind was critical to the process since it was needed for the vortex to form These whirls are common to the desert portions of all Neta-class planets They do not normally present a hazard to humans Nefad (9156) proposed that the Conohs storms were but a manifestation nf the accumulation of multiple vortices associated with die turning of the wind vector by planetary rotation ^ It is now known that Nefad's early considerations were overly simplistic and in part incorrect Hohshas (11301) provided the basis from which our present understanding of these storms has been derived 4 Conohs forces did indeed play a major role, but the seventy of the storm involves several factors All had to combine in harmony to produce the greatest of these storms An almost constant temperature difference (annual mean) of 27 degrees Celsius existed between the equator and the poles This temperature difference caused atmospheric flow between equator and poles On Arrakis the flow was quite sluggish The cooler air from the poles, being more dense, flowed along the surface, but was warmed quickly by surface radiation In the northern hemisphere this flow was detected westward, in the southern