Rainbow Mars

by Larry Niven

A final tiny push and they were up against bark, in a ring of light-sail stumps. Miya was already in the airlock. Svetz followed her through, his flesh shrinking from unseen high-velocity bits of metal.

  Slowly, carefully, Miya showed him how to make knots that would come apart at a pull. They wound cables around the huge stumps, moored the Minim tight, then climbed back inside. The airlock held them both, intimately, as something like a rainstorm began: bullets ticking against the hull.

  The sky lurched into motion.

  The inner door opened. Miya moved briskly to her chair.

  Svetz blocked the sun’s flickering arc with his forearm. He watched stars whirling around him, the brighter twinkling of clustered light-sails, whirling Mars sinking away. A wooden structure built itself on one side of the Minim, and continued to flicker with motion.

  “Studying us,” Svetz guessed. “They saw us disappear here. Zeera, could they detect us?”

  “How would I know?”

  Mars was a ruddy dot, not even a half-moon anymore. The sun was fixed, a glare among the mirrors at one end of the tree.

  Svetz asked, “Miya, you had a plan. Are we still on track?”

  “Me? Plan?” Miya laughed, then sobered. “All right. I’m trying to think like an orbital tower here, like a tree, Hanny. Where does a Hangtree want to go? It must have crossed interstellar space to get here. Why didn’t it go straight to Earth?”

  “Low gravity, high spin. Mars, not Earth.” She’d told him that.

  “But Mars is mostly desert. Earth is mostly ocean. Why wouldn’t a Hangtree want to zero in on the richest water-and-oxygen spectrum in the sky? Our problem is we got hung up on seeds,” Miya said. “A plant can bundle tiny bits of information into a million seeds. A Hangtree can’t do anything that simple. Interstellar space is just too big to find anything by accident. Even a seed that got lucky wouldn’t be anything more than a bit of meteor.

  “It must have crossed space as a tether, already a hundred thousand klicks long and festooned with solar sails, all ready to move into place and take over a planet.” She looked at them. “Right?”

  Svetz was reserving judgment.

  “Ten thousand years on route, getting energy from starlight but using up its reserves of mass, getting more like a dried-out dead tree all the time. It leaves fat and arrives lean. Anything that migrates does that,” Miya said. “It finds a world and takes up orbit, maneuvering with the sails. Drops seeds. An anchor grove grows. The Hangtree drops a root. The grove sends up water and soil nutrients. The Hangtree sends down sugar sap. They feed each other. They grow.

  “It picked Mars because Mars is easy. Earth makes a better garden, but two and a half times the gravity means a tree has to be longer and stronger. Now it’s strong enough. It was almost ready to tear loose from Mars. Then we got here and war came swarming up the tree. All that dead weight tore it loose, or maybe it was just ready.

  “It’s going to Earth.”

  28

  When it became clear that nothing was going to happen fast, Zeera and Miya went to sleep, leaving Svetz on watch.

  * * *

  The tree had made accommodation with the prevailing tide. Its down branch was pointed into the sun. Constellations streamed past, conveying a sense of progress, marking a year for every circuit.

  There was motion on the tree.

  The dulled silver elevator track was being stressed, stretched, pulled apart. Anchor points popped. Torn ends slithered away from each other, up and down the trunk. Then a wave of repair ran down the rail and left it intact and shining silver and flickering with traffic.

  Mirrors at the tree’s end points flickered endlessly. Bubble domes sprang up along the tree’s up branch, then were replaced by more angular, more solid structures. Svetz could see their mutating silhouettes against the glare of mirrors at the up end.

  Beehives formed along the down branch. Plumbing began to grow along the bark. Suddenly the pipes were shattered and most of the beehives became charred craters in the bark. It all began to grow again, like mushrooms.

  Svetz tried to guess how many Martians, how many martian races, were still on the Hangtree. It seemed they’d built vertical cities, fought, then reached an accommodation.

  The tree was maneuvering, going somewhere: the flicker of light-sails told him that. The Minim’s instruments might have told him more if he’d learned to read them.

  New light-sails were beginning to unfold on the old stumps around the Minim.

  The elevator track wriggled restlessly, now crooked, now straightening. Torn again, repaired again…?

  Hours passed in the Minim. Svetz had lost count of the years passing outside. Sixty? Seventy?

  Light glinted from Miya’s eyes. She was awake.

  He spoke his fear, lightly. “We are going to Earth, aren’t we?”

  “I’m sure it’s what the tree wants.” Sleep made her voice gravelly.

  “Maybe it’s ready to cross to another star.”

  Miya wasn’t looking at him. Her fingertips glided over her instrument display.

  Svetz said, “We’ve been between planets for something near a century. Whatever Martians are still with us must have made their peace with the tree—”

  “They’re here if they want to be. Any Martian would have had time to get back down to Mars.”

  “What if they learn to steer the tree?”

  “There’s a nice thought.” Miya laughed. “They could take the tree to Europa. Let it pick up gigatons of water, bring it back to Mars, cut into the trunk and let sap bleed out. Fill up those canals! We’d end up at Europa with no fuel and nothing to eat. Pass me a dole brick, Hanny.”

  He did that. Miya said, “Now, the FFD completely futzes up our inertial guidance, and the computer can’t find our location because nobody thought to tell it about changes in the constellations. But I’ve graphed our insolation—that’s the light that’s been falling on us since we left Mars. Here.” Tap. Svetz’s display changed. Sure enough, that was a graph. “Curve looks choppy, doesn’t it? Sunlight should be more steady. Maybe all the mirrors screw it up. But see for yourself, Hanny, we’re getting twice the sunlight now. We’re going in toward the sun, not out. Anyway, the Earth-Moon system went past while you were talking, and here it comes again. See it?”

  Svetz never could find anything that someone else had to point at. He said, “I’ll take your word.”

  “Are you awake?”

  “I want some sleep, if you can take over.”

  “Go ahead.”

  * * *

  Still asleep, or trying, he let both arms drift up to block a blue-white strobe. It almost worked. A fitful glare lit up his eyelids anyway.

  When he opened his eyes, the Minim was in a bouquet of rippling mirrors.

  The mirrors shifted languidly. Edges parted and closed again. He caught partial views of glare-white clouds forming and swirling and dissolving frenetically on a whirling blue background. A black shadow swept across …

  Zeera saw that he was awake. “We haven’t moved for a while. We thought you should be up when we turn off the FFD.”

  “Should think so. Martians all around us.” Svetz loosed himself from the web. He was groggy. Free fall made him clumsy. “Good call, Miya. Earth. Did the tree touch down yet?”

  “Not yet. It’s dropped seeds. Showers of seeds, a dozen times in a dozen places. I think it must be waiting to see which anchor trees come up. We’ve been here two years and a fraction. We’re not in geosynchronous orbit; we’re drifting.”

  “Can we finally check in with the Institute?”

  “The talker doesn’t work in Fast Forward. We’ll have to drop out.” Zeera’s forefinger reached.

  “Hold it!”

  Miya spoke soothingly. “Hanny, we’re fine. We programmed the Minim for reentry. Those light-sail stumps weren’t dead after all, so we’re pretty well hidden from any Martians. We drop out, we use the talker to call present time—”

  “Cut the Minim loose first! Miya,
we can’t see them. Take translators and blasters too. Are we all going out?”

  Zeera laughed. “Translators? In vacuum?”

  “If you find yourself wound in a net in some Softfinger pressure dome, Zeera, you will be glad you have a translator.”

  “All right, Hanny. You and Miya do that. I’ll phone home.”

  29

  The spinning Earth jarred to a stop. Svetz went out first into a forest of mirrors. Yes, it was fun to squeeze in next to Miya, but they’d be too confined to fight!

  He worked fast. Reality rippled bewilderingly, showing him an army of brilliant green bulb-headed lizards. Now came a forest of companions in a yellow pattern, and Miya was beside him, helping. Now came larger distorted shapes in silver-brown—

  Svetz whirled and lashed out. He couldn’t remember snatching out the heavy blaster. Blaster handle and fist whacked hard into protruding glass goggles in a bronze mask as big as his whole chest. Glass shattered and sprayed.

  A meter of sharp silver lashed out. Svetz ducked under the backhand stroke as a long-barreled weapon spat fire past him. Then both weapons were wheeling through space while the intruder covered its face with both arms, trying to hold in the air. While Svetz gaped, a third appendage reached far out and closed like a vise around his leg.

  If he’d seen the intruder first, he’d have frozen in terror. It was four meters long. It had six limbs like an insect, but no thorax or tail. And Miya was on its back, her fingers working to pull its upper arms loose.

  Fog puffed out. The intruder went limp.

  Svetz wriggled out of the loosening grip on his knee. He barked, “Zeera, did you cover all that? Do you see more of them?”

  “Just the one, but futz!”

  “I want to bring it in. Don’t vent the air, pump it.” A live prisoner would be nice … vacuum doesn’t kill instantly … but a corpse would do, and they’d want that air.

  Miya disengaged herself from the monster and pulled it around to look at it. She couldn’t have seen much inside the hard-shelled suit. She wrestled the helmet off. “Come see these eyes,” she said.

  Svetz shuddered.

  Had he disappointed her? She said, “I used to envy you. The weird, wild creatures you’ve seen and touched. Come on, Hanny. Look at the way the eyes are placed, so it can see to both sides at once. It could almost be an herbivore—”

  He let her pull him close.

  The skin was yellow-green. The eyes were closed under lids that might have been cut from tennis balls. They were too far apart, vulnerable-looking at the edges of a squarish head. The Martian would see forward too. Hands opened and closed reflexively at Miya’s touch. The middle pair were thick and clumsy, with a callused heel.

  The Minim’s great cargo door opened to the sky in a trace of icy fog. Svetz and Miya pulled the creature inside.

  “Some erg counter has me on hold,” Zeera said. “Shall I close up and pressurize?”

  “Right,” said Miya.

  They pulled a cargo net over the alien. The Minim had just become a lot smaller. Zeera said, “I wish we could bag that. When it starts to rot—”

  Miya said, “We can look it over first.”

  Svetz didn’t want to be involved in that. “I’ll finish up out there. I want us loose,” he told Miya. “No, wait.” He fished his blaster out and put it back on the wall. “If we’d fired these deathtraps in that house of mirrors, we’d be nothing but ash!”

  “Oh, futz! But, Hanny, what if there are more?”

  “It’s a risk.”

  * * *

  Svetz took his time, methodically pulling tethers loose and coiling them and stowing them under hatches on the hull.

  Any creature this big had to be something of a loner, just to find enough to eat! If a squad of green giants had found the Minim, they would hardly let Svetz smash their man’s visor and kidnap him, would they? They couldn’t be that different.

  If these lines got tangled, the Minim couldn’t reenter.

  But, methodically pulling cables loose and stowing them, he kept spinning around to look for intruders.

  Miya’s radio voice said, “It’s not breathing. How are you doing?”

  “Near finished.”

  “I’ve got its suit off. There’s flexible tubing down the insides of the suit. It’s got a backpack too.”

  The Minim was free.

  “There aren’t any fingernails or toenails. Its ancestors may have had an exoskeleton, but there are only a few plates left, like it was born wearing armor. The tusks are bone, and there are bones and joints in the limbs … no ribs … still, a well-developed endoskeleton. That middle pair is legs and arms both. I can almost see how the shoulders rotate. Mph?”

  “What?”

  “Oh, now I see. Hanny, you’re going to love this.”

  “I’m coming in.”

  Miya’s arms were around the green giant, compressing its torso, releasing. “It still isn’t breathing.”

  Too much to hope for, wasn’t it, that an alien captive would be built like Earth’s life-forms? Still—“Insects don’t have lungs. Check for openings along its sides.”

  “That’s what I meant, but spiracles still have to be pumped!”

  Zeera shouted, “Futz it, will you both strap in? I might have to launch—”

  The cheery voice of Willy Gorky barked, “Zeera! How’s it going?”

  Zeera’s arms waved frantically, summoning Miya and Svetz to their seats. “That’s a long story, Willy, but we’ve got everything you wanted.”

  The voice from the other end of time said, “Great!”

  They took turns talking. “We saw at least five kinds of tool user. I’m pretty sure they weren’t all intelligent.”

  “Miya’s collected some seeds—”

  “—big, heavy golden spheroids with a texture like foamed ceramic for a reentry shell. But those only make the anchor trees, Willy—”

  “—we think.”

  Descriptions of the last leg of the flight had to come from the women, while Svetz’s eyes peered between the mirror blossoms, up and down the trunk.

  “The tree still has some drift to it,” Miya said. “It’s been dropping seeds. It prefers targets on the equator—”

  “Strips of seeds fifty klicks long, generally crossing a shoreline.”

  “You’ll remember that the grove on Mars was partly on a canal.”

  “Boss, we don’t exactly know what to do now. The tree won’t bud a sapling until it’s ready to move on. If it locks to Earth and we leave it in place, will it still be here in present time?”

  That was a serious question. Ra Chen and Gorky held rapid discussion with techs and time travelers, irritatingly half audible. Willy Gorky said, “We certainly want to watch the tree link up.”

  “That could take years,” Svetz said.

  “Not for us.”

  “Willy!”

  There was whispering at the other end of time. Then Willy Gorky said, “You’ve got the FFD, Zeera. Use it. And the Secretary-General wants to see some Martians. Have they made any attempt to contact you?”

  “Yes and no—”

  “We had a prisoner, sir, but we th—”

  “It moved,” Svetz said.

  Miya loosed herself and went to look.

  Without the pressure suit it still looked armored. Dark green back, pale yellow face and belly. Jeweled ornaments were riveted to exoskeletal plates, and holsters for tools including tube weapons and knives. Nasty little spines of polished metal jutted from its mid-limb wrists. There were rows of holes along its flanks.

  Thick eyelids suddenly rolled open. Bulging eyes wobbled independently as they scanned the Minim, making Svetz’s own eyes hurt, then both centered on Miya.

  The hull rattled. Svetz turned to see shapes like spindly frogs bounding among the mirrors. Tubes in their hands spat fire. He saw three six-limbed giants wrestling a much bigger tube into place. It poked out through the silver petals, looking straight at him, and he yelled, “Launch!
Launch now!” Turned to scream, “Miya—”

  Tether yourself! died on his lips. Miya had been distracted. Six limbs wrapped themselves around her and pulled her close. Her fists and heels pounded against the creature’s shell.

  “Launching now,” Zeera said.

  The intruder sighed and sagged limp under nearly Earth’s gravity of thrust. Miya rolled clear.

  Dead aft, the big tube was looking right at the Minim.

  “We have a live prisoner.” Zeera spoke crisply above the rocket’s muted scream.

  “Great!” said Willy Gorky. “But you launched? To Earth? Of course to Earth, sorry, I’m still catching up, but Zeera, we want those Martians! The SecGen—”

  “They were firing on us!”

  The burn ended. The big tube spat orange flame. Attitude jets puffed as the Minim slewed sideways: automatics avoiding a meteor. Something massive tacked the hull anyway.

  The mid-trunk dwindled. It was still huge, a world in itself. Was it more slender than it had been at Mars? Earth’s Hangtree must be longer because geosynchronous orbit was higher. Of course it must have grown longer year after year, and more slender too, and that was why the rails had ripped!

  Miya still wasn’t in her command chair. Svetz looked back. Miya was moored to the wall by sleeping tethers, just beyond the monster’s reach. She was talking, the monster was talking, and the translator was talking too.

  Svetz always hated learning a new language.

  He said, “Willy, the only Martians I talked to did all their talking after I was a helpless prisoner. Maybe we’ve done exactly the right thing.”

  From the other end of time Gorky said, “Ah … maybe. Where are you coming down?”

  Zeera said, “South America, northern edge of what became Brazil, right on the equator and just at the shoreline. It’s where the anchor trees seem to be having the most success.”

  “Good luck.”

  “Wait! Sir, how do you expect to get us back?”

  Willy Gorky said, “We’ll send the small X-cage for you. Call us when you get down and give us decent coordinates.”

  “How?” Zeera cried. The inertial calendars on the X-cages weren’t that accurate, the Minim didn’t have one, and Willy Gorky didn’t see the problem at all.