The system resembled a chainsaw held together by the forces of inertia and magnetism.
The impact of a gazillion of these iron rings against the magnetic field of the top block had originally boosted it—and the freight-transfer station built around it—high into the Martian sky. The top of the fountain extended from the well at Tharsis Montes almost up to synchronous orbit. As the top station had sailed aloft during the initial stages of construction, the engineers fabricated and attached a series of collapsible shells to its lower perimeter, enclosing the ever-lengthening stream against random winds at ground level and providing spaced magnetic deflectors that nudged the higher segments eastward to counteract the planets Coriolis forces.
In those early stages, bringing the hoop-stream up to speed had consumed nine-tenths of the systems energy. The flying rings had consumed whole quads of electricity, enough to drive the industrial sector of a fair-sized moon. That initial input had come from a cloverleaf of solar farms and fission piles constructed on the planet's surface for this purpose. Once the operation was balanced, however, it required only minor additions of maintenance energy to stabilize the stream and the structures it supported against the pull of Mars's gravity. The power plants could then be diverted to serve other needs in the local economy.
The fountain only required small inputs to replace the minuscule amounts of kinetic energy that the freight handlers bled off in the form of electricity. They used this current to pass cargo and passenger pods to and from the interplanetary ships that crossed above the tower in intersecting orbits. The electricity also worked mass drivers, which pushed goods and people up and down the exterior tower shell between the top station and the surface.
Although the system had cost billions of Neumarks to build and power up, it now saved as much or more ever year in the costs of rocket propellant and hull ablation—not to mention the occasional pyrotechnic tragedies—associated with orbital shuttles. Being wholly electric in operation, the Tharsis Montes Space Fountain was as quiet, non-polluting, and safe to ride as a trolley. In principle and structure this system copied the Earth-based fountains operated by the U.N. at Porto Santana, Brazil; Kismayu, Somalia; and Bukit-tingi, Indonesia. Like Tharsis Montes, these were all on the planets equator and served geostationary transit points, although the technology worked at all altitudes and at any latitude; the small fountain at Tsiolkovskii, for example, was nowhere near the Moon's equator.
Although the Mars fountain's supporting stream of flying rings was silent and vibrationless in operation, their iron composition did induce momentary currents in the tower's metallic superstructure. These showed up as ionization along its outer surfaces. Against the star-filled blacks of" space surrounding the tower's upper segments, Demeter sensed an aura of plum-colored light at the periphery of her vision. But as she neared the planet's surface and entered what remained of Mars s indigenous atmosphere, the blacks faded to salmon pink and the glow dimmed to a patina of lilac over the gray of finished steel.
Her mothers colors.
Despite the massive energies involved in erecting and maintaining the space fountain, at this point in her trip Demeter Coghlan was still essentially in freefall, after seven months of microgravity on the transport ship coming up from Earth. Looking out the viewport past the purple mists of atmospheric ionization, she was barely conscious that she floated on her stomach with her heels higher than her head. Demeter didn't at all mind a few more hours of swimming weightlessness; she was just glad she could finally give up those mandatory three hours of osteopathic exercise per ship's day. Demeter hated jogging on the wheel with her arms and legs strapped into spring-weights—even if the workout had taken off thirteen pounds of cellulite that she really could afford to lose.
Craning her neck, and pressing her cheek against the cold glass—or whatever clear laminate they used for pressure windows here—she tried to look down and see the base of the fountain. The column of violet light seemed to touch the ground in the wide caldera of a shallow lava cone. Coghlan thought this was Olympus Mons itself but decided to query that fact with her personal chrono, which tied into the local computer grid whenever it could. Certainly the fountains transit pod would have an RF antenna in the walls or something for the convenience of passengers and their cyber servants.
"Hey, Sugar!" Demeter whispered into the titanium bauble on her bracelet. "What's that-there volcano I'm looking at?"
"Could y'all be a tad more specific, Dem?" came back the pearly voice with the Annie Oakley twang she'd programmed into its microchips.
"Well, I'm riding the space fountain on Mars, y'see, and we're just about at the bottom. There's this big crater right below us—I thought maybe Olympus Mons, you know? Looks like it could be, oh, sixty or eighty klicks in diameter, with an ash cone maybe five or six times that wide. So, is this an important piece of real estate or what?"
"Please wait." The lag must have been mere microseconds, because Sugar spoke again almost at once. "Regretfully, I can establish 110 interconnect with network resources. Electromagnetic interference inherent to the operation of Hyde Industries' space elevators must be blocking my radio signals. However, knowing that we were going to Mars, I did pack some general history and geography into spare memory. Want to hear it?"
"Go on ahead."
"Olympus Mons—with a diameter of six hundred kilometers and an elevation of twenty-six, the Solar System s largest volcano—is located at twenty degrees north latitude. That would be almost twelve hundred kilometers from your present position. I doubt even the southern shield of the Olympus trap rock would be visible from your current elevation on the fountain's lower structure. On the other hand, the transaction coil for the Mars elevator is based at one-hundred-twelve degrees west longitude, zero degrees latitude, adjacent to the population center known as Tharsis Montes. That is the second-largest tunnel complex built by Earths colonists to date."
"I already know that, Sugar."
"Ahh, right.... So, the nearest natural feature of any prominence is Pavonis Mons, with a height of twenty-one kilometers. This is one of the largest calderas of the Tharsis Ridge. After accounting for variables like pod elevation, atmospheric density, and probable dust-storm activity, I deduce this to be the cone you-all are describing, Dem. Chance of error is less than twenty percent."
Coghlan summed up. "Okay, so Tharsis Montes is the name for the colony—"
"And this whole volcanic plateau," Sugar put in.
"—while Pavonis is the big crater. Got you. Thanks, Sugar."
"No never mind, Dem."
Ever since her accident, Demeter Coghlan had placed certain operating restrictions on her chrono. For one thing, she had voice-programmed it with a persistent courtesy, rendered in such null phrases as "please" and "never mind." That didn't make Sugar any more human, but Coghlan found it easier to relate to a machine that talked like one. For another, she had limited the unit's on-line access to the planetwide computer grid. Consequently, Sugar had to announce where she was getting her data from and the probability for error in any calculation—something most cybers omitted in talking to humans these days. As a third precaution, whenever Coghlan went to bed she put Sugar and her charm bracelet in a drawer or under a water glass. That way, the device wouldn't pick up anything she might say in her sleep and report it back-to the grid. Probably paranoid behavior on her part, but all the same it made Coghlan feel better.