Arrakis has a density of 4.95 g/cm3 and an acceleration due to gravity of 864 cm/sec2. With a gravitational attraction of this magnitude, the light gases such as hydrogen and helium have all but escaped into space. Atmospheric pressure at the equator is 760 mm, about average for a planet of this diameter and mass.
Arrakis is the only planet in the Canopus planetary system to harbor organic life forms. Life on Arrakis has been subject to harsh conditions during its history. Along with the local star group, there is an extensive dust cloud that permeates the Canopus near space. This dust cloud was first detected by the Arrakian astronomer Chelin in 12704. The consequences of the cloud were not fully recognized until 12984 when evidence was found that correlated ice-age-like periods with the dust cloud opacity. The peculiar velocity of Canopus carried it and the planetary system through regions of varying cloud opacity. This had the resulting effect of reducing the radiation incidents on Arrakis, thus triggering near ice-age conditions. A similar, but even more severe shift in conditions occurred when Arrakis's third moon was destroyed by an asteroid/comet some 200,000 years ago.
Krelln — first satellite. Krelln is the largest of the two Arrakian satellites. Krelln has a mean radius of 488 km and orbits the parent planet at a mean distance of 324,077 km.
The satellite has a density of 3.97 g/cm3 and is composed of titanium-rich silicates in the crust and mantel. The silicate mantel, extends to a depth of 170 km. There is no apparent differentiation in composition which implies scant reheating following satellite formation. The presence of a small, rocky core has been established by seismic studies.
Large numbers of craters dot the surface of Krelln. Crater diameters range from 40 km to small pit-like features less than 1 mm in diameter. Since Krelln has no atmosphere, the landscape is stark with the only erosion due to thermal stress and particle impact. A layer of meteoritic dust covers the surface of Krelln to a depth of 11 cm.
Krelln orbits Arrakis once every 25.5 days with nearly the same face toward Arrakis. Libration of 16 degrees occurs once each orbit. Because of the small angular diameter of Krelln (10.36 arc minutes), total eclipses of Canopus do not occur.
Krelln has been of limited commercial use; however, titanite mining operations were established. Krelln has also functioned as an observational facility for deep space surveillance.
Arvon — second satellite. Arvon is the smaller of the Arrakian satellites with a radius of 201 km. The satellite orbits Arrakis in 5.7 days and occupies a nearly circular orbit with a perigee distance of 103,000 km. Arvon orbits Arrakis in less than one-fourth the time required for Krelln. Arvon subtends an angle of 13.42 arc minutes. Having a diameter larger than Krelln, total eclipses of Krelln occur every 547.2 days.
The physical characteristics of Arvon differ from those of Krelln. A density value of only 2.02 g/cm3 results from the presence of large amounts of subterranean water ice and frozen carbon dioxide. Cratering is evident, but is less pronounced due to the more fluid crystal structure. Arvon has no measurable magnetic field and is geologically inert. No evidence of tectonic activity has been detected by Arrakian scientists.
Extaris. The fourth planet, Extaris, is the smallest of the outer planetary bodies with an equatorial radius of 8,112 km. Extaris has a mean density of only 1.31 g/cm3; such a low density is characteristic of the outer planets.
The primary constituents of Extaris's atmosphere and their relative abundance are: atomic helium 0.83, Zeon 0.15, carbon monoxide 0.01, and trace amounts of Zenon, Krypton, and cyanogen.
Atmospheric pressures exceed 250 standard atmospheres, yet Extaris's weather is essentially benign. This is due to three factors; one, the orbit is nearly circular (eccentricity 0.015); two, the axial rotation is slow, with the Extaris day equal to 42 hours; and three, the upper atmospheric layer of Zeon ice reflects 97% of the incident radiation from Canopus back into space. These effects minimize the transfer of thermal energy to the lower atmosphere. The resulting lack of thermal gradients prevent the formation of significant cyclonic or anticyclonic circulation.
Unlike the inner high-density planets. Extaris and the other outer planets have several satellites. Extaris has five satellites that orbit the primary at distances from 117,000 km to 399,000 km. The four inner, icy satellites arc in circular orbits and were probably formed from the same molecular accretion as Extaris. The rocky outer satellite, however, occupies an extremely elliptical orbit (eccentricity 0.55) which is inclined to the equatorial plane by 19°. Furthermore, this satellite, Aja by name, orbits Extaris in a retrograde manner. These orbital characteristics clearly imply that Aja was gravitationally captured eons ago. No record of first observations of Aja has been found.
The four inner satellites are composed of a thick ice mantel surrounding an outer core of silicate material. At the center of the outer core is a very small, dense, inner core of nickel-iron. This inner core has no fluidity which accounts for the lack of measurable magnetic fields generated by internal dynamo activity.
Ven. Ven, the fifth planet, is the giant of the Canopus planetary system with an equatorial radius of 210,500 km. Together, Ven and Canopus account for 99.9% of the total mass and angular momentum of the system. The planet orbits in a mildly elliptical orbit (eccentricity 0.11) at a mean distance of 2.58 x 109 Km.
The planet is just under the mass limit that separates planet from star. Temperatures at the cloud tops, however, never exceed 57° Kelvin. At this temperature the only atmospheric components that can exist in the gaseous state are hydrogen, helium, and monophospherine. The latter molecular specie is responsible for the soft pink appearance of Ven.
From a distance, Ven presents a very pleasant, tranquil appearance. However, upon closer scrutiny Ven is found to be a most inhospitable planet. Crashing atmospheric pressure coupled with sub Kelvin temperatures preclude the existence of organic life. An extraordinary feature not observed elsewhere in the planetary system is the complete absence of organic molecules. Extensive laboratory studies by Krai, et al. (15188), showed that monophospherine has strong catalytic properties that can distort and eventually break down the covalent bonds of organic molecules. The resulting carbon, nitrogen, zeon, and other residue lie kilometers deep on the liquid nitrogen surface of Ven.
Almost a star, Ven radiates strongly in the very far infrared and millimeter regions, of the electromagnetic spectrum. The emitted radiation is not uniformly distributed over the planet, but is observed to be emitted from discrete regions. The radiation emanates from three localized areas, one in the subpernal zone, and two in the upper mid-temperate band. The emissions from these active regions are periodic with each region having a different, but constant, period. Periods range from 790 microseconds to 12 milliseconds. Unfortunately, all attempts to locate these discrete sources with remote sensing probes have been unsuccessful. While speculation abounds, no reasonable explanation for the natural occurrence of such phenomena has been established. Most Arrakian scientists felt that these radiating sources were placed deep within the body of the planet by intelligent beings in the remote past — perhaps to provide a navigational guide beacon for deep space vehicles.
Revona. Orbiting at a distance of 7.7 x 109 km is Revona. The planet is so remote that Canopus appears as just a very bright first-magnitude star.
Revona has a radius of 2,225 km and occupies a unique place in the Canopus system. The planet is composed entirely of helium existing in different phase states. A dense atmosphere of atomic helium covers the planet to a depth of 70,000 meters. Temperatures in this layer vary from 11°K at the upper helium boundary to 4.2°K at the quasi liquid surface. It was the discovery of this interface by Daret in 14390 that stunned the members of the Planetoscience Council on Arrakis. Just beneath this interface, the pressure is sufficient to alter the phase state of helium from gaseous to liquid. The result of this phase-state change is a pale blue sea of liquid helium forming just below the interface.
At a depth of 3,900 meters, the liquid temperature reaches 2.6°K and the he
lium abruptly changes to the zero-viscosity helium 3, This abrupt change occurs as the liquid helium passes through the tri-alpha transition. This transition is only a few meters thick and is characterized by high dynamic turbulence.
Hypo-seismic studies have shown that Revona possesses a solid central core the composition of which is not known. Most planetologists agree that the most plausible core material is helium existing in the supra metallic state.
Revona is not alone in its remote position. It shares space with one satellite, Laran. Laran is 553 km in radius and orbits Revona at a mean distance of 37,000 km. Laran's composition is strikingly dissimilar to Revona. The satellite has no atmosphere and has a solid crust and interior of carbonaceous material. Permanently stationed geoseismic monitors have recorded no internal activity, only occasional meteoritic bombardment. This data, together with the satellite's composition, suggest that Laran is a captured body and has an age measurable in eons.
Laran serves two very useful functions: that of being the most remote outpost in the system, and of being the site of the Revonan helium conversion facility. This facility provides the liquid helium 3 required for supercooling the reactive coils of the hypo-gravimetric power generators used on Arrakis.
W.H.
ARRAKIS, Atmosphere of before the Atreides
COMPOSITION. Major gaseous constituents were nitrogen (74.32% by mass), oxygen (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 planet1. Present differences are due to compositional changes that have occurred over the five intervening millennia, and in no way reflect inaccuracies in 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 significance to many atmospheric phenomena. A notable example is the so-called "Coriolis 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 scattering 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 planetary mean temperature (annualized), and a mean global wind speed, standard height, of 20 ± 3 kilometers per hour. It should be 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 circular and the planet's axis of rotation was directed almost perpendicular to its ecliptic plane. Because of this the small polar ice caps appeared to remain unchanged (orbital observation). However, extensive scientific studies have shown that the caps did exhibit a very slight advance and retreat with the seasons and hence a slight amount of water vapor was transported between the poles. Ptahtercicah (9527) investigated the mechanisms of water vapor transport in terms of the minimum amount required to sustain any 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.2
WEATHER PHENOMENA. Thin, cirrus clouds occurred seasonally in the vicinity of the polar caps, but dust clouds (and the generating storms) were the dominant feature of Arrakis's weather. Every day dust was injected into the 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 Coriolis storms were but a manifestation of the accumulation of multiple vortices associated with the turning of the wind vector by planetary rotation3. 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 derived4. Coriolis forces did indeed play a major role, but the severity 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 low 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 deflected westward, in the southern hemisphere eastward (Coriolis effect, planetary designation 3). Planetary rotation is in the B class, meaning that the general circulation was broken up into eddies. These are called cyclones and anticyclones, using the ancient Terran names. On all Neta-type planets with a 3 classification the cyclones produce storms. But the cyclones on Arrakis produced violent storms, primarily because of excess ozone.
Ozone was concentrated only two kilometers above the surface. It was produced by Canopus's strong ultraviolet flux and absorbed much of the flux. The atmosphere thus experienced considerable heating at this low altitude. Temperature was high at the surface, decreased with altitude, but then increased when the ozone layer was encountered. Convection and advection associated with the cyclones was thus normally confined within two kilometers of the surface. This confinement greatly intensified storm severity.
Surprisingly, the greatest Coriolis storms on Arrakis were not produced in this manner. A truly great storm occurred only when the ozone heat barrier was broken! Nefad almost recognized this fact. The strength of the ozone heat barrier depended upon the ultraviolet flux from Canopus, which varies. The strength of the cyclones varied also, but most important were the convective vortices. As we now know from the Rakis Finds, these were most prevalent during a daytime frontal passage. The stronger the cyclone the more vortices that were produced. Each vortex carried surface heat upward to the ozone barrier. On those occasions when conditions were right the heat transported upward could produce temperatures immediately below the ozone layer which were greater than that within the layer itself. The barrier was destroyed when this occurred. The reaction was self-perpetuating and explosive in its impact, and a truly great dust/sand storm evolved as the atmosphere in a real sense was overturned.
Wind speeds as high as 800 kilometers per hour were recorded within these storms by certified instruments (which also managed to survive the storms' fury). Pachtra (10002) reported a single measurement of wind speed in excess of 1000 kilometers per hour. This is generally discredited since his instrument was out-of-certification at the time5. Additionally, such a speed would exceed the speed of sound, ground level, on Arrakis. Supersonic winds have never been confirmed on any planetary surface. Yet, as Ghralic so aptly puts it: "The residents of Arrakis reported fearfully loud noises during the greatest-storms. Could it be that the winds exceeded Mach-1 at times? The entire subject merits an attempt at laboratory duplication under controlled conditions."
Electrica
l phenomena were an integral part of the surface environment. The dust whirls and storms generated considerable dust charging through tribo-electrification. Lightning discharges occurred frequently within the clouds and occasionally bolts struck the surface. Ozone was produced but this was only a minor contributor to total atmospheric ozone.
Sand size (and larger) grains remained mostly in the lower levels of the Coriolis storms. Those closest to the surface caused severe erosion. If the planet were not so geologically active (see ARRAKIS — GEOLOGY) its surface would have been entirely flat except for the ubiquitous dune fields.
During the decay phase of the storms much of the dust settled back onto the surface. Water vapor absorbed on the grains was carried downward also (a phenomenon locally called El-Sayal). Ionization by ultraviolet rays gradually released the water back to the atmosphere. Return was complete within a few days.
SURFACE EFFECTS. Surface erosion from storms and the presence of dune fields are noted above. The processes involved have been understood since antiquity and no elaboration is needed here. However, the dust chasms (sometimes called tidal dust basins) and the drum sands merit special attention.
The chasms or basins were produced by geological processes, being subsequently filled with dust. They were a hazard to unwary travelers because the dust had a quicksand-like behavior. The dust packing was so under-dense that tidal motions much like oceanic tides were readily observable (locally called sandtides). The question of considerable scientific interest is why the dust should have exhibited almost negative packing, hence fluid-like behavior, since similar situations have rarely been found on any other planet. We are indebted to Asterák (15104) whose brilliant insight provided the final and correct answer by successfully producing the effect in the laboratory6. The sequence of events is as follows:
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