Rainbow Mars by Larry Niven

nothing like flowers or fruit or seeds or pinecones.
    Miya was taking more time to explore, but she was making bigger jumps. He stopped another hundred klicks down and dipped in again. Tree parasites had grown sparse. Nothing else had changed.
    The upper tree was a line of winking lights when he emerged. Pretty. Svetz zoomed his view. Lights twinkled all along the trunk to the far tip. Signals.… “Miya, they’re talking about us.”
    The edge in her voice matched his own. “I see it. Mirrors. They can chop huge mirrors out of those light-sails. What the futz is that?”
    *   *   *
    Something ghastly bright was coming at them out of the night. The breath froze in Svetz’s throat. Something like an eroded gray mountain came straight toward the tree, turning massively as it came. The flicker of mirror-speech stopped as it moved on them, growing, growing, gone past with several klicks’ clearance.
    Fear made Miya’s voice ragged. “Missed. Hanny? Talk to me!”
    â€œI’m okay, but that was disturbing. Phobos? It must scare the Martians into fits every time it comes by.”
    â€œIt and the tree must be in a resonance pattern. Ha! We can hope. What else have you found?”
    â€œLook up,” he said. Her suit was badly chosen, too like the colors of Mars, but he’d spotted her. “I found you. ”
    He dropped past her and slowed, keeping his distance. She eased alongside him. Two flight sticks fell together along the narrowing trunk. Dawn was crawling down the tree toward Mars. A broad crescent of dawn crawled across black land toward the base of the tree.
    Not black land. He saw lines of light, brighter where they crossed. Cities formed where canals met. There were more cities, arcs of light like little crescent moons on the darkness. Directly below was a cruciform glow. But none of those lights were blinking.
    â€œUp here they’re talking with reflected sunlight,” Miya said. “Talking about strangers on the tree. They’ll get answers as soon as it’s daylight below us, and then the whole planet will know all about us. Maybe it’s time to talk to some Martians.”
    Svetz agreed. “Offer them refuge. Tell them what’s going to happen.”
    â€œWe don’t exactly know what happened, Hanny.”
    â€œMakes us less persuasive. And from everything I can tell,” Svetz said, “Martians would rather open fire than conversation.”
    There were lights flickering below, not on Mars, but—
    â€œDuck,” he said. Another open cage was rising toward them, flashing with reflections and tiny puffs of fire. Futz, there were crabs crawling all over the outside! Crabs as big as Wrona, with human faces, it looked like. Human shapes inside the cage were doing the shooting.
    He glided sideways to put forest between him and what he’d seen.
    â€œFutz!”
    â€œWhat?”
    â€œSomething hit my helmet,” Miya said.
    â€œFutz! Pull into the foliage, let me look at you!”
    â€œI’m fine. My ears are ringing a little.”
    Still falling, braking with their flight sticks, they eased around the narrowing curve of the tree. Svetz heard Miya cursing softly before he spotted it.
    Above them on a second pair of silver tracks, a wooden raft hung vertically. A cargo lift, rising. Things were tied to it: a boxcar-sized bulb with a door in one end, and several smaller boxes. Man-shapes were clinging to the web of lines.
    Something struck his back-shell, not from the cargo lift. Svetz yelped and lifted on the flight stick. But that would take him too close to the guns on the cargo lift! Around the trunk, then, with bullets trying to follow him, and then turn off the flight stick and fall!
    â€œWhere are you?” Miya asked.
    â€œFalling. West side.”
    â€œThe trunk below us is swarming! Hanny, let’s go with your guess. Go in at the bottom end of the black forest. Hide in