Priest said, “We know now the atmosphere is impossibly thin. It’s mostly carbon dioxide, and there’s no oxygen, and hardly any water vapor. Not even nitrogen… Mariner didn’t find any canals, incidentally. Even though it flew over an area where a lot of the most prominent canals were expected.

“All our ideas were turned upside down by this. With such a thin atmosphere, any life must be very hardy. Nothing like terrestrial life at all. But, of course, the question of life won’t be settled until humans land there. It was one hell of a disappointment, the NASA guys tell me. Suddenly, Mars became a place it wasn’t worth traveling to. If we don’t make it to Mars, if the funding and resources aren’t assembled, then for me, that shock of Mariner 4 will have been the turning point.”

York shrugged. “But NASA oversold Mars for years. It was a kind of holiday resort in the sky, teeming with life, justifying all the billions they wanted to pour into rockets and spaceships…”

Priest laughed. “A holiday resort. I like that.”

After Mariner she’d become briefly interested in Mars, and its history in the human imagination. She got books from the library. Mars as the Abode of Life by Percival Lowell, New York, 1909; Mars and Its Canals by Lowell, New York, 1906… She remembered fantastic, gaudy pictures of huge irrigation canals dug across the face of a dying, drying Mars, long descriptions of the waves of vegetation and the herds of animals which must sweep across the red Martian plains. The Mars Project: Wernher von Braun, University of Illinois, 1953. It had a big rocket ship on the cover, like a kid’s book. Von Braun wanted to build ten spaceships in Earth orbit, each weighing three and a half thousand tons, and carrying seven men. It would take nine hundred flights to orbit to assemble the Meet. There would be two-hundred-ton landing boats, to take fifty people down to the surface for a year-long stay… These visions, she’d thought, were a boy’s dreams of power, dressed up as serious engineering plans.

York had put that stuff aside. Even at the age of sixteen, York was hot on science, on the strictness and logic of it; she found herself getting unreasonably impatient at illogic, and wishful thinking, and the emotional coloration of rational processes of all sorts.

(Actually she was much too severe for most of the boys her mother tried to match her with. You’d think that someone who’d suffered as messy a divorce as Maisie York would learn not to meddle in other people’s relationships…)

The fact was that to her the real Mars was a hell of a lot more interesting than Lowell’s anthropocentric dreams.

Because of Mariner, Mars had turned into a place you could do some geology.

How would the geology of Mars differ from Earth’s? What would that tell you about Earth that you couldn’t have learned from staying at home? A hell of a lot, probably.