Free Bowl of Heaven by Gregory Benford and Larry Niven

to land, Captain?”
    “Down there.” Redwing waved toward Cupworld’s green-tinged rim.
    “Yes, I thought so. If you land near the Knothole, you’ll be millions of klicks from any water source, and right on top of the systems that shape the electromagnetic fields. We could be perceived as a threat.”
    Redwing blinked. “You think so?”
    Mayra kept her face blank, apparently her way of being diplomatic. “We have no idea how the builders of this thing feel about visitors.”
    Cliff couldn’t resist saying, “At least they didn’t shoot at us.”
    Redwing grimaced; he had not been chosen for fighting skills. “They haven’t tried to talk to us. I don’t like that.”
    Cliff put in, “But, Captain, the rim is where all the water and farmland is. They must live there.”
    Mayra added, “It’s spinning around at thirty-four klicks per second, too.”
    Redwing nodded. “Higher than our orbital speed, right? Do we have onboard fuel to catch up with that spin?”
    Abduss said, “It will take a significant fraction of our onboard reserves, principally water for the nuclear rocket.”
    Redwing snorted. “ All our onboard ships are fusion powered. We can fly wherever we like if we can get water from Cupworld. We’ll need the same trick to use any of them. Okay, say we see a lake. We’ll put SunSeeker in a nearer orbit and drop the lander from there. Beth will know how to do that. Cliff!”
    Cliff jumped.
    “Where shall we land?”
    They were asking him as the biologist. “It all looks like farmland and meadows and forests,” he said. “Different habitats, probably—see those ice fields? I don’t know how they create those, but our telescopes can’t make out individual trees. All I’ve got is a light spectrum, but clearly from spectral reflections, the plants are using chlorophyll, Captain. Land anywhere near water on the rim, I’d say, and refuel the tanks first thing.”
    Mayra asked, “Do we land on the inside of the bowl? Or the outside?”
    Redwing frowned. “Inside, of course. That’s where they live.”
    Mayra pursed her lips and said evenly, “They surely launch their own spacecraft from the outer surface. They could simply put their ships in elevators, lower them through an outer air lock, and let them go. Immediately the ships would have a thirty-four-kilometer-per-second velocity. All with no need to fly through an atmosphere, or out through the film that covers their atmosphere.”
    Cliff grinned. Mayra had been thinking as he did, asking how the hell this enormous contraption worked. “You think we could go in through their outer air locks? From underneath? Maybe to reenter, they have magnetic clamps or something to catch incoming craft. Maybe we could use those.”
    Mayra shrugged. “Suppose we do. How do we knock on the door?”
    Redwing mused, “They must have safeguards.…”
    “Even if we get in the door, they control the locks,” Cliff added. “We’d be caught.”
    Redwing liked that. He sat back and gave them all a glassy grin. “Makes it easy to choose, doesn’t it? We must retain our freedom of maneuver until we know what—whom—we’re dealing with. We go down through the atmosphere, then.”
    “We’ll have to bust through that film they have,” Cliff observed.
    Abduss added, “They might see that as aggressive. I would.”
    Redwing nodded. “But it’s the only way not to be cornered from the start.”
    “Makes you wonder, doesn’t it?” Cliff said casually. “They must have seen us. How come they haven’t come out to pay a call?”
    Abduss said, “Good, yes. I have received no electromagnetic transmissions, either.”
    “Funny,” Redwing said. “You’d expect at least broadcast radio.”
    “Perhaps they use point-to-point comm, laser links,” Mayra said. “Just as we do.”
    Redwing sat up straight, switching to his command voice. “Abduss, would we have time to hover? Pick a landing spot?”
    “Not much.”
    “We’ll take Eros, ” Captain