For Tony, Christine and Catherine

I am grateful to the following for assistance with research, suggestions and comments:

Jardine Barrington-Cook and his colleagues of the Space Division, Logica U.K. Ltd., who developed the guidance software for the Huygens Titan landing probe.

Mitchell Clapp of Pioneer Rockerplanes, author of the Black Horse spaceplane proposal.

Martyn Fogg, author of Terraforming: Engineering Planetary Environments, the standard text on the subject.

Dr. J. F. Zarnecki of the Space Sciences Unit, Kent University, U.K., who developed the surface science package for the Huygens probe.

And to the following for reading versions of the manuscript:

Simon Bradshaw

Eric Brown

Kent Joosten of the Solar System Exploration Division, Johnson Space Center, NASA.

After seven years of flight, after travelling a billion miles from Earth, the human spacecraft Cassini reached Saturn.

Cassini was about the size of a school bus. Thick, multi-layer insulation blankets covered most of the craft’s structure and radiation-hardened equipment. The blankets’ outermost layer was translucent amber-colored Kevlar, with shiny aluminum beneath; the two layers together made it look as if the spacecraft had been sewn into gold.

But Cassini looked its age.

The blankets were yellowed, and showed pits and scars from micrometeorite impacts. The brave red, white and blue flags and logos of the U.S., NASA, ESA and the contributing European countries, fixed as decals on the insulation, had faded badly in the years since launch. Cassini’s close approach to the sun, with the intense heat and solar wind there, had done most of the damage.