They rested through the day, and after dark they were off again. They passed the mouth of a long canyon that ran from Ceraunius to Jovis Tholus; it was an oddity in that it was neither straight nor sinuous, and was called Crooked Canyon. When the sun rose they were hidden on the apron of Crater Qr, just north of Jovis Tholus. Jovis Tholus was a bigger volcano than Tharsis Tholus, bigger in fact than any volcano on Earth, but it was located on the high saddle between Ascraeus Mons and Olympus Mons, and both were visible on skysills to east and west, bulking like vast plateau continents, and making Jovis seem compact, friendly, comprehensible— a hill you could walk up if you wanted to.

That day Sax sat and stared silently at his screen, tapping at it tentatively and getting a random assortment of texts, maps, diagrams, pictures, equations. He tilted his head at each, with no sign of recognition. Nirgal sat down beside him. “Sax, can you hear what I’m saying?”

Sax looked at him.

“Can you understand my words? Nod if you understand.”

Sax tilted his head to the side. Nirgal sighed, held by that inquisitive look. Sax nodded, hesitantly.

That night Coyote drove west again, toward Olympus, and near dawn he directed the rover right up to a wall of pocked and riven black basalt. This was the edge of a tableland cut by innumerable narrow twisting ravines, like Tractus Traction only on a much larger scale, creating a badlands like an immense expansion of the Traction’s maze. The tableland was a fan of broken ancient lava, the remnant of one of the earliest flows from Olympus Mons, capping softer tuff and ash from even earlier eruptions. Where the wind-cut ravines had worn deep enough, their bottoms broke through into the layer of softer tuff, so that some ravines were narrow slots with tunnels at their bottoms, rounded by eons of wind. “Like upside-down keyholes,” Coyote said, though Nirgal had never seen a keyhole remotely like these shapes.

Coyote drove the rover right into one of the black-and-gray tunnel ravines. Several kilometers up the tunnel he stopped the car, beside a wall of tenting that cut off a kind of embolism in the tunnel, a widened outer curve.

This was the first hidden sanctuary that Art had ever seen, and he looked suitably startled. The tent was perhaps twenty meters tall, containing a section of the curve a hundred meters long; Art exclaimed over the size of it until Nirgal had to laugh. “Someone else is already here using it,” Coyote said, “so be quiet for a second.”