But as she continued to ascend, day after day, up and up beyond all imagining, the snow patches became thinner, less frequent. Eventually she was twenty kilometers above the datum— twenty-one above sea level— nearly seventy thousand feet above the ice!— more than twice as high as Everest was above Earth’s oceans; and still the cone of the volcano rose above her, a full seven thousand meters more!Right up into the darkening sky, right up into space.

Far below scrolled a smooth flat layer of cloud, obscuring Tharsis. As if the white sea were chasing her up the slope. Up at this level there were no clouds, at least on this day; sometimes thunderheads would tower up beside the mountain, other days cirrus clouds could be seen overhead, slashing the sky with a dozen thin sickles. Today the sky above was a clear purple indigo suffused with black, pricked with a few daytime stars at the zenith, Orion standing faint and alone. Out to the east of the volcano’s summit streamed a thin cloud, a peak banner, so faint she could see the dark sky through it. There wasn’t much moisture up here, nor much atmosphere either. There would always be a tenfold difference between the air pressure at sea level and up here on the big volcanoes; pressure up here must therefore be about thirty-five millibars, very little more than what had existed when they had arrived.

Nevertheless she spotted tiny flecks of lichen in hollows on the tops of rocks, in pits that caught some snow and then a lot of sun. They were almost too small to see. Lichen: a symbiotic team of algae and fungus, working together to survive, even in thirty millibars. It was hard to believe what life would endure. So strange.

So strange, in fact, that she suited up and went out to look at them. Up here one had to employ all the old careful habits: secure walker, lock doors; out into the bright glare of low space.

The rocks that harbored the lichen were the kind of flat sunporches on which marmots would have sunbathed, if they could have lived so high. Instead, only little pinheads of yellow green, or battleship gray. Flake lichen, the wrist-pad guide said. Bits of it torn away in storms, blown up here, falling on rocks, sticking like little vegetable limpets. The kind of thing only Hiroko could explain.

Living things. Michel had said that she loved stones and not men because she had been mistreated, her mind damaged. Hippocampus significantly smaller, strong startle reaction, a tendency toward dissociation. And so she had found a man as much like a stone as she could. Michel too had loved that quality in Simon, he told her— such a relief in the Underhill years to have even one such charge, a man you could trust, quiet and solid, that you could heft in your hand and feel the weight of.