Stefano began, “I have not seen—”

“This is hours old. The Mat is now exhaling a great deal of CH₄, methane.”

Rachel was startled. “Didn’t that happen during the first explorations?”

Hassan nodded. “And not since, not in such quantities. Several times an Earth year there are small, well, belches. But not like this.”

Stefano asked, “Maybe that’s a symptom of greater growth?”

Hassan shrugged. “As I recall, sometimes it recalls previous visits we’ve made, other times not. It must be reminded a bit through physical symbols—simple geometries, mostly—and photos displayed on screens.”

“Suppose the flooding, the methane—it’s referring to a deep, long memory?” Rachel asked quietly. Use your intuition. Time to put the cat among the pigeons.

Hassan’s mouth was open to continue, but his eyes flickered and he said nothing.

“Of what?” Stefano broke the silence.

Hassan took a breath and let the words slide out, as though letting go of a secret idea. “Perhaps we should read the flooding as a sign that the Mat liked the wet, warm ages.”

Stefano scowled skeptically. “Why should it?”

Hassan said, “That’s when it might have gotten out onto the surface. Spread, maybe. The atmospheric pressure was much higher then, mostly CO₂ and water, providing some shield against the UV and cosmic rays.”

Rachel sighed. “It could see the stars! At last. Earth, the planets. It had millions of years to think over the sights as they changed.” The words came out like breathing, easy and immediate and without conscious thought.

Rachel could see the two men considering how this idea shifted their positions, eyes veiled. To some, everything was politics, in the end. She decided to step in as they pondered, just to stir things up; this was fun. “In that time, could it have directly connected with other parts of the Marsmat, on the surface?”

They eyed her. Plainly this was a chess game, with ideas as pieces to advance, when needed.

“Preposterous,” Stefano said.

“Why?” Hassan chided.

“To think the Mat would remind us of its past—”

“The alien was there, Fraq,” Rachel said. “That made a difference.”

Stefano pulled the edges of his mouth down in disdain. “Why?”

“The Mat could tell that Fraq was different from us. I was there, sure, but I certainly don’t know why. Maybe its ‘eyesight’—if that’s what it has, with chem senses, too, maybe—can distinguish humans from other species.”

Hassan put in, “We’ve never shown it an animal. There are pets here, a few, but never occurred to show the Mat one. Then how could the Mat—Only… only by experience.”

Rachel saw it then. “Yes. The Mat has seen Fraq’s kind before. Something happened back then.”

Stefano sniffed. “This is all mere supposition.”

“Sure it is,” Hassan said. “Let’s follow the logic.”

“To what conclusion?” Stefano insisted.

“Well, for one, how about this idea that the flooding was a recognition signal?” Rachel said.

Stefano’s mouth compressed into a thin line. “But that would imply—”

Hassan shot back, “That Mars was wet when Fraq’s kind came here.”