Almost Complete Short Fiction, page 111
Black, pyramidal mushroom-equivalents jutted two and three meters up from the forest floor reeking both fetid and sweet. Like everything on Haze and Shadow, except where an eruption, storm, or recent impact had caused a kill, it seemed to be a climax forest, or even more than that, a collage of living fossils some of which might be older than multicellular life on Earth.
The trees frequently hosted vines of comparable scale, which apparently did them no harm. Beams of light lanced through the mists of the upper canopy. An eerily ape-like pseudosimian cavorted in the vines far above them. Shape prejudice made them seem like relatives, but the consensus was that they were less intelligent than, say, terrestrial opossums.
“Damnedest thing you ever saw, isn’t it?” Marianne said, coming up behind him. “Ready?”
“Ready,” he replied.
“Grab a walking stick.” She gestured to a stand of “beetle plants,” whose overlapping iridescent leaves had reminded someone of beetle wing covers.
“Walking sticks? Marianne, it’s only a tenth of a gravity up here and these packs mass less than four kilos!”
“Which means a lot less weight to steady you and less friction to stop you—though your momentum is as much as ever. We need the balance aid. Also they’re useful for clearing plants away and avoiding close encounters with Hazing life of the slobbering kind. They can’t eat us, but they don’t ah know that. We can’t use anything technological but our com electronics in here. But what we can have is a stick. Take one.”
Too warm and uncomfortable to argue, Akil just nodded and pulled the stiff leaves off what seemed a suitable staff, though with more effort than he’d have guessed. What was left reminded him of bamboo.
Marianne led, bounding off toward the tree line. He followed.
The forest had a profusion of detail, but all the details looked much alike to Akil.
“How do you know where we’re going?” he asked.
“Look for the yellow-brick-fruit tags.” Marianne pointed above with her staff. “There’s one.”
Akil looked for a while and finally spotted a basketball-sized yellow globe hanging from a low branch, patterned with what looked for all the world like alternating rows of yellow bricks. A few more seconds of searching revealed another one about thirty meters ahead.
“Those are native to the outer pole archipelago, so any that you find here, we put there. If you pick them before they get ripe, they seem to last forever. At least they’ve lasted for the couple of months since we’ve been here.”
“Okay, we follow the yellow-brick-fruit road, then.”
Marianne laughed at the reference. “That’s the general idea. The Forest People always come down the same base trunk to visit us. We’ll assume she went up the same way. The path slants up the aureole wall, then heads straight up the mountain till we get to the first base trunk ring, about ten kilometers from the central caldera. Then we circle north until we hit the right main trunk and ascend about ten kilometers.”
An hour into their trek, Akil noticed that the canopy blocked the view above, forming a green and yellow sky. Oshatsh, approaching the horizon now, shone under this, and the shadows of tree trunks became more and more numerous until the effect was one of shafts of sunlight reaching in, rather than individual shadows. But there would be no problem with light until the eclipse. Oshatsh set was a long-extended affair, as light refracted through the least curved horizon of the deep atmosphere—and the vast half globe of a waxing Shadow would light the sky for another hour, though less and less as the umbra of Haze bit into it. He looked for spots, but Oshatsh was a settled old K5 star with a generally placid surface.
For the next hour, the path led up the slope of the volcano around which the forest grew. The terrain was awesome; huge blocks of “ah-ah” lava as large as spaceships jutted up through the carpet of debris, massive trunks and vines headed endlessly skyward into the mist, and webs that seemed made of thin vines filled in much of the space. Though he had “flown” through it in virtual reality, clearly any real flight by anything much larger than a duck was impossible. Sticking close to the ground, they got under most of it and lifted up any obstructing web with their walking sticks.
“Where are the spiders for these webs?” he asked.
“The webs are the ‘spiders,’ ” Marianne said. “Sort of. Look, we’ve given these things descriptive common names according to whatever they remind us of from home. But never forget that webs aren’t webs, pseudosimians aren’t apes, and flying elephants don’t act anything like terrestrial elephants. Look, over there. A web’s got a butterball.”
He looked in time to see a web collapse around what looked like a yellowish soccer ball. The soccer ball had a beak like a parrot’s at one end and four ridiculously small, claw-tipped wings arranged around its belly. It squawked once, then vanished from view, as layer after layer of white netting wrapped itself around the struggling creature.
“Vicious,” Akil said.
“That’s why you don’t often see butterballs this deep in the forest.”
“Are the nets dangerous?”
“One of them started to wrap me up once, but spit me out before completing the job. I got an interesting pattern of acid burns out of it, but they healed in a couple of days.”
“Sounds like fun.”
She shook her head. “Cured me of going bare-assed out here. I wrote the page on the nets; how much study did you get in before they sent you down here?”
“Level three on fauna. . . .”
“That was flora, Akil.”
“Oh.” Unfortunately, Akil had never been that interested in plants.
“Just try not to touch anything but rocks, trees, and blackleaf vines, and you’ll be okay. Don’t rest on the large elephant-ear leaf vines. They grow around things—quickly, by plant standards.”
Using paths filled in by forest debris, they made good time through the ah-ah field. The shade gave little relief from the heat; this deep in the distended Hazian atmosphere, heat was borne by air more than light. Akil brushed by something that looked like a loose ball of spaghetti with long thorns that made a sound like ripping paper as they scratched across his coveralls. He felt a sharp sting as one of them penetrated the weave.
“Porcupine Plant,” Marianne said as she saw him pull it out. “The quills can be a nuisance.”
He nodded, ruefully.
As they ascended, the lava field changed from the blocky ah-ah into a more smooth, ropy pahoehoe, but on a scale ten times what Akil had seen on Earth. The largest lava tubes under them would be immense, and he savored the thought of exploring them.
What appeared to be a clearing opened beyond the trees to their right, looking at first like a slightly raised meadow. Akil suspected otherwise, and confirmed his suspicions through his com patch. “Marianne, can we hold up a bit?”
“Uh, sure. Whew.” She looked like she could use a break. “We’re almost there, anyway.”
“Ever been over there?” He nodded toward the clearing.
“No. A crater?”
“The main east vent. We think it’s going to be active again in a few days. Want to take a look?”
Marianne took a breath. “Eclipse is coming up. I want to be on the tree by then.”
It was getting darker; Akil knew that far above the canopy, the shadow of Haze had started to cover the almost full disk of its sister world. Mid eclipse would bring real night.
“Just a quick look?” he asked.
“Okay. Quickly.”
They hopped up the slight rise in a couple of minutes and were rewarded by a kilometer-wide hole in the ground filled with smooth, flat, lifeless rock. Dim in the diffuse fading light, the forest rose around it on all sides like some kind of giant’s cathedral. High overhead, individual trunks and vines lost themselves in the misty gloom.
“Chaos, what a place!” Marianne said in a hushed and awed voice.
Akil smiled. Then he saw what he was looking for. “Steam,” he said, and pointed to his left. “Over there on the rim.” Thin white tendrils rose there, easily visible against the almost-black of the forest.
“Akil . . .”
“What?”
“Down below. In that big wide crack. I see a glow.”
Akil stared, couldn’t see anything at first, and turned to Marianne to tell her so, but as soon as he averted his vision, the red glow jumped out at him a little further along the crack than he had been looking. “Good eyes! If things go as predicted, that hole could be full of molten lava in a few hours. Okay, we’d best get going.”
But Marianne stayed rooted, wide-eyed. “Is this what the main caldera looks like, on a larger scale, of course?”
Akil shook his head. “Radiography shows it’s full of debris. No light in there, anyway.”
“Okay. Ready to go.”
Ten more minutes of bounding uphill brought them to an immense vertical trunk that Akil thought must be thirty meters across. It had two yellowbrick fruits hanging from a lower branch. A glance at the map displayed on his com patch showed them about ten kilometers out from the main caldera. So near, yet so far—but he was on another mission today. He prepared himself for a climb that would be long, hot, and tiring even in low gravity that had noticeably decreased as they ascended closer to the nullgee point between the worlds. But as they approached the tree, he heard a very low pitched moaning.
“Hear that?” Marianne asked. “This is one of the first trunks that actually goes all the way to the LI point. It’s also our elevator.”
“Elevator?”
She grinned. “That’s the surprise. It’s hollow. See that opening? What you hear is a draft blowing into it. In the trunk, the flow rises about seven meters per second.” Marianne smiled at him.
It was darker black on lighter, but Akil could make out a notch in the tree twice as big as a person.
Marianne stuck her staff on her backpack and approached the notch from the side. She grabbed a vine on the way and then moved in front of the notch, coveralls flapping in the first stiff breeze Akil had seen on Haze. She clearly needed to hold onto the vine to keep herself from being sucked in.
“Cool at last! Oh, this feels good! See you upstairs!” She let go and was gone.
Venturi effect, Akil thought. If the shaft velocity was seven meters per second, and the opening half the area of the shaft, the inlet air stream would be about fourteen meters per second. He thought for a moment. Terminal velocity, where wind resistance equaled weight, for a spread-out person falling on Earth, was around 48 meters/second. In Vie gravity, that was reduced by the square root to about 12 meters per second. Then the atmosphere was almost three times as dense; so a light breeze of 4 meters per second should be enough to support his weight here. So a seven-meter-per-second air stream should leave him with a net ascent rate of about three meters per second. Air density would trail off some with altitude, but here between the worlds, gravity would trail off even faster.
He followed Marianne’s example and approached from the side, grabbed a vine, then moved into the air stream. He had to hold on hard, but the wind felt wonderful—cooling and drying him.
It was time to go. Still, to just let go and let himself be blown away worried him. What if he hit something? If he was going to hit the inside of the tree opposite the wall, he wanted to hit feet-first, so he grabbed the edges of the opening and lifted his feet.
The wind swung him up like a vertical hanging gate, and he let go when he was horizontal. He brushed some resilient foliage on the top of the notch a couple of times, and then he was floating up in the breeze. Turbulence near the sides of the tube pushed him back toward the center whenever he
drifted away from it. He could barely sense his motion, but the spot of light below him grew steadily smaller. Then it vanished altogether. Eclipse.
“Marianne?” he said into his com patch, worrying about a collision in the dark. A comforting dim glow came from its screen, light enough for his dark-adapted eyes to see the insides of the hollow tree trunk as he drifted past them, if he didn’t stare directly at the screen.
“I’m about a hundred meters above you,” she replied.
Plenty of distance. “Just out of curiosity, how do we get off?” he asked.
Marianne laughed. “There’s a net blocking the shaft at our stop—no worries; it’s a dead one. Now I have some questions for you. Why is it so hot here? With the eclipses, the forest gets half as much light as the rest of this double planet!”
“Convection. This thick air and Oshatsh’s redder spectrum means most of the incoming energy gets absorbed on the way down and distributed by air currents. Around the tree, the atmosphere is even deeper because the gravitational potential levels are further apart. That blocks more of the infrared radiation; so you get more greenhouse effect. Still, because of the eclipses and lower pressure, it averages about five kelvins cooler here than Haze’s outer pole.”
“Could have fooled me. Exercising too much, I guess. Okay, now tell me why Haze and Shadow even have an atmosphere. And why haven’t Haze and Shadow merged?”
Very good questions, Akil thought; questions that formed much of the motivation for the expedition in the first place. There were plenty of models, all with a lot of free parameters and some good guesses, none of which was proven.
“We’re still working on it; we’ve only been here for a few months, after all. I can tell you this much; because the atmosphere is so thick, water and any other hydrogen compounds tend to freeze out many kilometers below the mesosphere. So it’s almost all dry nitrogen, oxygen, and helium above the stratosphere, and largely helium atoms with only a few nitrogen and oxygen molecules when you get to the top of the atmosphere where molecules might escape.
“That’s the exobase, and its temperature is about 23 Celsius below freezing. To escape Haze and Shadow, atoms only need to move about 1900 meters per second, like on Earth’s moon. But the thermal velocity of neutral nitrogen or oxygen atoms at that temperature averages less than four hundred meters per second, so they pretty much stay put.
“Ion pickup is another matter, but Oshatsh has a lot less ultraviolet than Sol and doesn’t create a lot of ions. Nor does it have much solar wind, and what it does have is largely neutral. Still, there’s a significant loss. But there are significant reservoirs of volatiles, too. Big oceans and large ammonia clathrate deposits at the bottom of those oceans, mainly along the orthomeridian.”
“The what?”
“The great circle equidistant from the inner and outer poles; it’s at right angles to the prime meridian and goes through the north, south, east, and west poles. The term was invented back in the twenty-second century by the geographers of tide-locked worlds.”
Marianne sighed audibly. “Got it. So we think Haze and Shadow are losing their atmosphere, they just haven’t had time to lose most of it.”
“Yeah, more or less. Chandra thinks the time constant is something like five billion years. Sun-Oh used a different method and got three billion, but Oshatsh is easily eight billion years old, so there’s something they don’t understand going on here. That’s why we do these things, I guess. Haze and Shadow combined still have about two and half times as much atmosphere, by mass, as Earth does, and must have started with a lot more.”
“I see. Now,” Marianne asked, “why haven’t they crashed together?”
“We don’t know. Tidal perturbations and friction should have done the job long ago. But there are a couple of contrary influences; you notice how it’s always cloudier on the trailing hemisphere?”
“Yeah, come to think of it.”
“Well, the greater reflectance on that side provides a small net push in a spin-up direction. Also, the ongoing mass loss decreases the gravitational attraction. The geometry of the land gives a tidal slosh frequency that’s out of phase with rotation, so that drag effect is tiny as well. Finally, the forest itself may pump-up the rotation like a Landis tether, by contracting slightly during eclipses and relaxing otherwise.”
“The Gaia effect?”
Akil shook his head. “Thermal if anything. Anyway, the length of the day may actually be increasing, but we haven’t been able to find ancient coastal tide lines because all the land surface is volcanic and generally younger than the hundred million years or so of data we’d need. There’s essentially no fossil record.”
“Tell me about it,” Marianne said, a hint of exasperation in her voice. “We biologists have nothing to explain evolution here, either, or where the interforest came from. Those volcanoes look weird, don’t they? Like big nipples. Why?”
Akil laughed. “That one I can explain. It’s the sharply curved potential surfaces between the worlds. If you measure the mountain surface against the local mean potential surface, they have roughly the same slope as Olympus Mons, Mauna Loa, or any other shield volcano in the known universe. What low gravity gives in vertical scale, it takes back in a reduced coefficient of friction. Remember, it has to get down to zero in the center where their gravities cancel each other, about a hundred and sixty kilometers up. It’s like the two planets were trying to suck each other’s guts out.
“On the interforest, my guess is that the shield volcano on Shadow’s inner pole once reached almost to the LI point. Surface gravity would have been down to less than one percent of Earth’s at the surface. Trees of ten or fifteen kilometers height would have been structurally feasible, and their tops could easily have hung over into Haze’s gravity well and grown down to Haze.”
“Well . . .” Marianne sounded unconvinced. “The problem with that is that the main interforest trunks are more closely related to the local vines than the tall trees of the perimeter. It might have started as air weed at The L1 point that hung lower and lower until it touched the ground. Before you tell me The L1 point isn’t stable going in or out, we’ve thought of that. The updrafts from the inner poles are enough to keep things up there. A kind of Sargasso air sea formed between the inner poles. The wonder to me is that the forest survives the eruptions.”
