The ferry that had brought them to the Aldrin from the Flinger was only a skeleton of nuclear engines and control systems, with their party and Marsbound supplies the only payload. Humans were luxury items on Mars, still. To avoid harming the Marsmat that underlay most of the warmer depths of the planet, the workforce was mostly robots, without messy, smelly humans.

The same ferry, with its ceramic shell, was used to do the atmospheric braking at Mars—buffeting down, surfing an entire atmosphere—and Rachel would go home on the same personnel ferry, because it cycled, too.

Inside the Aldrin’s stony shield she had enjoyed the longest pseudo-vacation of her life, in a watery paradise. She could forget entirely that the whole neatly arranged cylinder-world was crouching inside a spinning, stony shelter, fending off the sleet of cosmic rays and hard vacuum. The Aldrin took about 2.135 Earth years to arc in a single synodic period, an eccentric loop around the sun from near-Earth to the Martian orbit, beyond Mars and then back to Earth. Getting to Mars took 146 days. Then the Aldrin spent the next sixteen months beyond Mars, serving the miners in the inner asteroid belt, picking up cargo and dispensing supplies. The SETI contingent would catch it to go back to Earth.

The other Mars cycler, the Holmbolt, followed a complementary trajectory, half an orbit away. Taxi and cargo vehicles attached to a cycler at one planet and detached when reaching the other.

Once steered into place, the cyclers—with utterly dependable schedules and low sustaining cost—had opened the door for routine travel to Mars. Plus (the real point) a permanent human presence for asteroid mining. Mars was a side issue of little import. The Belt, a vast mishmash of cinders, rubble piles, dead comets, and mineral-rich floating mountains, attracted no tourists. But it fed a quiet revolution, the true use of space for resources, and so then the Third Industrial Era. Long-term economic advantages made the cyclers invulnerable to cancellation by political whim.

So the colonization of Mars came as a side benefit of big industry.

This made it simple for Rachel, Fraq, Xiaoling, and the rest of the SETI team to take the five-month trip to Mars in relative comfort, protected from the sleet of gamma rays and high-energy protons peppering the rocky skin. Fraq and his flock went into some kind of hibernation for the whole voyage, devising their own chambers and chemicals and monitoring equipment. Ythri were quite quick at mastering human technologies, turning them to new uses.

Rachel and Xiaoling had studied and played and explored. They admired the huge smelters and borers bound for the asteroid mines. They swam in the axial zero-g spherical droplet, using air tanks. Many hours passed as they watched the incredible views, with advanced optics to telescope in on distant worlds. The hollowed-out asteroid had already yielded a huge inventory of metals, especially platinum. Such wealth had kicked off the wildcat opening of the Third Industrial, making the Aldrin both a lavish hotel and a living, spinning monument.