Green Mars - Kim Stanley Robinson [160]
From the southern flank of Nicholson they could see south for many kilometers, and midway to the horizon was the black line of the cable’s second time around. This section had impacted many times harder than the first pass, and two swaths of ejecta paralleled the cable like henge mounds. It appeared that the cable just barely stuck out of the trench it had smashed into the plain.
As they got closer to it, weaving between ejecta boulders, they could see that the cable was a shattered mass of black rubble, a mound of carbon three to five meters higher than the plain, and steep on its sides, so that it did not look like it would be possible to drive over it in the boulder car.
Off to the east, however, was a dip in the mound of wreckage, and when they drove down the line to investigate, they found that a meteor impact subsequent to the cable’s fall had landed on the wreckage itself, smashing the cable and the ejecta swaths on both sides, and creating a new low crater that was all flecked and studded with black cable fragments, and occasional chunks of the diamond matrix that had spiraled inside the cable. It was a disordered mess of a crater, with no well-defined rim to block their way; and it looked like it would be possible to find a route through.
“Incredible,” said Coyote.
Sax shook his head vigorously. “Dei— Dei—”
“Phobos,” Nirgal said, and Sax nodded.
“Do you think so?” Spencer exclaimed.
Sax shrugged, but Spencer and Coyote discussed the possibility enthusiastically. The crater appeared oval, a so-called bathtub crater, which would support the idea of a low-angle impact. And while a random meteor hitting the cable in the forty years since its fall would be quite a coincidence, the fragments of Phobos had fallen entirely in the equatorial zone, and so a piece of it hitting the cable was much less surprising. “Very useful,” Coyote noted after he had negotiated their way over the little crater, and gotten the car south of the ejecta zone.
They parked next to one of the last big chunks of ejecta, and suited up and went back to have a look at the site.
There were brecciated chunks of rock everywhere, so that it was not obvious which were pieces of the meteor and which ejecta excavated by the cable’s fall. But Spencer was pretty good at rock ID, and he collected several samples that he said were exotic carbonaceous chondrite, very likely to be pieces of the impact rock. It would take a chemical analysis to be sure, but back in the car he looked at them under magnification, and declared himself confident that these were pieces of Phobos. “Arkady showed me a piece just like it, the first time he came down.” They passed around a heavy burned-looking black chunk. “Impact brecciation has metamorphosed it,” Spencer said, inspecting the stone when it came back to him. “I suppose it has to be called phobosite.”
“Not the rarest rock on Mars, either,” Coyote said.
• • •
To the southeast of Nicholson Crater, the two big parallel canyons of the Medusae Fossae ran for over three hundred kilometers, into the heart of the southern highlands. Coyote decided to drive up East Medusa, the bigger of the two fractures. “I like to go through canyons when I can, see if the walls have any overhangs or caves. That’s how I’ve found most of my cache sites.”
“What if you run into a transverse scarp that crosses the whole canyon?” Nirgal asked.
“I backtrack. I’ve done an inhuman lot of backtracking, no doubt about that.”
So they drove up the canyon, which proved mostly flat-floored, for the rest of the night. The following night, as they continued south, the floor of the canyon began to rise, in steps that they were always able to negotiate. Then they reached a new and higher level of flat floor, and Nirgal, who was driving, braked the car. “There’s buildings up there!”
They all crowded around to look through the windshield. On the horizon, under the eastern wall of the canyon, a cluster of small white stone buildings stood silently.
After a half hour’s examination with the car’s various imagers and scopes, Coyote shrugged.