Iris

The Command Module of Deepstar, shaped roughly like a cylinder, was divided into three floors, perpendicular to its long axis. The middle and by far largest floor was designed with ten personnel compartments around its periphery, surrounding a gear-shaped room that comprised fully half the habitable volume of the CM. This central chamber had been outfitted with a ramfloor , from which a myriad of couches, tables, and other memomolecular shapes could be extruded on demand. In its center was a p-curtained door leading aft, and forward access was through the ceiling to the next deck, where the kitchen module was housed. Directions were defined by the pull of em-fields on clothing. As they gathered for a final preinsertion briefing, the central room had been reconfigured into a sunken amphitheater and everyone was em-stuck to its surface except for Aksinia Ockels, who was late. She hung above them for an instant like some huge, gauzy-winged insect/bird hybrid, then assumed a sitting position. She touched the static-node of her clothing, creating a faint breath of em-force, and settled like a dust mote on the edge of the upholstered crater.

Jana Li Hu looked up from an attitude of concentration, licking her upper lip slowly. Annoyed at the woman's interruption, she glanced at the rest of the group. Placed at odd angles, they wore induction circlets around their heads, except for Sealock and Krzakwa, who had waveguides plugged into an unobtrusive gang-tap. Ariane Methol made a triad with them. She was a slim, mid-sized woman with a dark, lustrous mestizo complexion, fathomlessly expressive eyes,and shiny black hair worn just over shoulder length. Unrestrained by gravity, it floated in a shifting nimbus around her head. Her face was pretty and regular, though not really remarkable. It was the sort of face people had come to expect on a fashion model simulacrum: narrow, smooth, and cool.

She was a poly-tech engineer, specializing in Comnet subprogram debugging, and, in some ways, was the best in the world at what she did. There were others who knew more, others more skilled, but they were research scientists, useless in a tight commercial universe.

'OK.' Hu was flat-voiced, angry. 'To continue with the summary of planetography . . .' As she spoke, images illustrating the subject matter entered the minds of her listeners and textual data were superimposed on their vision fields. She wanted to present it fully, to force all the information on them, despite their disinterest. She had no illusion that some of them would retain what she said, or even understand it. But she would make the effort anyway.

'As you can see, the extreme smoothness of the ocellus on III is plain evidence, at least to me, of the enormously slow process of resolidification. This implies that either there was a forced eccentricity in this presently very regular system or else an object impacted on III that was itself a source of heat energy. To account for the paucity of craters we see here, we must posit, in addition to the extreme enhancement of cratering rates on the leading hemisphere relative to the trailing, a very long-lived glacial annealing process.

'Though superficially it looks like the basins on Tethys and Titania, it seems to be a different phenomenon. The data suggest that a small body, fifty kilometers or less in diameter, wrought profound changes in the entire object, melting a fifth of its total volume. You can see how the craters covering the remainder of the moon are lacking in relief. What you see are the remains of old craters at some depth, covered by the neon, argon, and other gases that constituted Ill's atmosphere during this period. . . .' Suddenly, Ariane spoke up. 'What does that mean, a body that tiny as source of heat?' Tem said, 'Any concentration of radionuclide would do,though it would have to have a relatively short half-life. I wonder what cosmological process would concentrate it?'

'I have already given this matter a great deal of thought,' said Jana. 'The total disruption of any second-generation macrobody that had completely fractionated would account for it. My report to the IAAU-PD will suggest as much.'

'Do you think that this 'body' was part of the Iridean system?' asked John.

'Unlikely since we're dealing with a planetary system that formed out of almost pristine type-2 galactic material. Iris and her satellites show a general depletion ofall radionuclides , as well as a scarcity of transironic elements. It was probably an intruder.'

'What about mascons?' asked Krzakwa. 'Is there one under the ocellus?'

'There's a slight gravitational anomaly associated with it, but this object sank almost to the center of Ocypete, so it's difficult to resolve it from the silicate core in general.

'Iris itself is very different from the gas giants we're used to. Aside from its small size, hardly half again the diameter of the Earth and only about 0.58e-mass, and slow rotation rate, it's meteorologically bland. Except at the very lowest levels, where there is a slow convective overturning, the atmosphere is quiescent. Iris, or at least the eighty percent of its total mass that is gaseous, has differentiated, giving rise to the Rayleigh -scattering mantle, which is a thick layer of hydrogen and, underneath it, a thinner stratum of helium. The surface of the white ball within is made up of nitrogen cirrus not unlike the obscuring haze of Saturn. I should point out that Iris is losing considerable mass due to solar irradiation. It has only been able to maintain its current mass/diameter ratio because of the extreme cold.' Aksinia laughed. 'You mean it's evaporating?'

Jana nodded. 'If it stayed this distance from Sol, it would dwindle to about a fifth of its present size, at which point its gravitation would be sufficient to permit retention of theremaining gases.....I can see by some of your faces that seems counterintuitive. You think that the smaller it gets the less able it should be to retain anything. Well, that's true—but it's a simple matter of the point at which the velocities in the excited gases attain escape velocity for that particular depth in the gravitational field. There are plenty of elementary texts in the library ...'

Another look about. Too many faces were blank. Some of them didn't know enough for anything to be counterintuitive. Once again, she wondered what the hell they were doing out here. . . . She sighed, and went on. 'Anyway, Iris' magnetosphere is very low grade, almost nonexistent, so we won't have to waste energy on a charged-particle shield.

'The Iridean ring is very much like Saturn's, without, of course, the gaps that give Saturn's its unique appearance. Iris' ring is nearly opaque, and it has a greater proportion of millimeter and smaller particles, there not being much in the way of magnetic sweeping here. Aello is an interesting small body which shows no immediately identifiable endogenic asterologic features. It's probably the best chance we'll ever get to examine a nearly pristine, totally undifferentiated body composed of cryogenic volatiles. Podarge is much like the many similar-sized moons in the Solar System, showing resurfaced terrains and an albedo asymmetry due to preferential gardening of the 'front'