“As we scrape them off to make room for potato fields.”
It laughed, a tinny, not unattractive, but quite unrealistic sound. “The native life is useful. And it is related to us.” It said this gravely, as if making a grand announcement.
“I don’t understand.”
“It is what I have deduced myself,” the ColU said with something like pride. “This was a significant achievement in itself. I do have a sophisticated genetic microlab on board, but when we began I didn’t even know what chemical basis any genetic material here might have. In the brief time we have been here I have managed to progress from that fundamental investigation to, by analogy, the discovery of the double helix… Yuri Eden, all Per Ardua life, like Earth life—that is, all I have sampled—belongs to a common family tree. And that family is related to the family of Earth life, as if they are two mighty trunks sharing the same root. But that commonality is deep, deep in time…”
Yuri, trudging in the hot light, said nothing. The ColU took that as an invitation to keep talking.
“Life on both Per Ardua and Earth is based on fundamentally the same chemistry: carbon, hydrogen, oxygen, nitrogen. Perhaps that was inevitable, given the physical nature of worlds like these, rocky, watery worlds, rich in carbon. But the choices made in how life evolves are not inevitable. All life on Earth is based on two chemicals, two acids: DNA, which stores the information that defines a life form, and RNA, which interprets that information and uses it to assemble proteins, which are the building blocks of life.”
“DNA as software, proteins as hardware.”
“That is an antiquated reference. You are showing your age, Yuri Eden. Both DNA and RNA are based on a particular kind of sugar, called ribose. Life on Per Ardua has a similar basic architecture. The information store is not DNA—but it is a kind of acid, based on the same sugar choice as DNA, ribose. There were other plausible possibilities—dextrose, for instance.
“Beyond that fundamental point, the two methodologies of life differ. Arduan genes do not use DNA; they use that ribose-based acid, which in turn encodes information using sequences of bases, but not the same sequences as DNA’s triple-base ‘letters’. Arduan life is based on proteins, which like your proteins are assembled from amino acids, but not from the twenty specific aminos used to construct your body, rather from an overlapping, non-identical set of twenty-four acids. Arduan life seems to rely on some genetic coding being stored in the proteins themselves—as if the genetic information is more distributed. This may help make the coding more flexible in the case of changing climatic conditions…
“On the other hand, Yuri Eden, life on Mars is based on a variant of DNA much closer to Earth’s than the Arduan system, and a more similar protein set. You can see the implication. Earth, Mars, Per Ardua—all these families of life are related. Mars is a more recent branching from Earth. Or vice versa.”
“Or it all branched off from what’s here, on a world of Proxima.”
“Yes. This is panspermia, Yuri Eden. A lovely idea, of life being carried through space, presumably in drifting rocks, blasted up by impacts from the surface of planets. The worlds of a solar system, Earth and Mars, say, or Per Ardua and the Pearl, may readily share material. But it is much harder, more rare, for material to be transferred between star systems. Whatever came here from Earth, or travelled from Per Ardua to Earth—or came from a third source entirely—came long ago, deep at the root of all the life forms on all the worlds. I imagine a panspermia bubble spanning the nearby stars, Sol, Proxima, Alpha A and B, perhaps others further out, all sharing the same basic chemistry. Beyond that, maybe there are other bubbles, of other sorts of life chemistry—perhaps nothing like our own at all.”
“And out of all that comes something as curious and busy as a builder.”
They were close to the forest fringe now. They came upon a garden of particularly large stromatolites, towering hemispheres each with a hardened carapace the colour of burned copper. They trudged on, parallel to the stromatolites and away from the track.
The ColU swivelled its camera eyes to study Yuri. “You have noticed that too. About the builders. That they display curiosity.”
Yuri shrugged.
“None of the others have noticed this, or if they have it has not been remarked to me.”
“So what?”
“Similarly, Yuri Eden, you try to puzzle out the transits of the inner worlds, while the others barely look up at the sky… You ask why I was made curious. Why are you curious, Yuri Eden?”
“Why shouldn’t I be?”
“The others aren’t. Not even Lieutenant Mardina Jones. You have all suffered huge trauma. You, in fact, have suffered more, having been sent away from your own time even before your exile here. And yet here you are, thinking, observing, watching the planets, the life of Per Ardua. You can speak to me openly, Yuri Eden.”
Curious about builders or not, Yuri didn’t like to look too deeply inside himself. He said uncomfortably, “I don’t think of it like that. It just feels like I keep getting pushed through these doors. From past to future, Earth to Mars, Mars to the Ad Astra, the Ad Astra to here. Or when things change. When people die, when Onizuka and Harry went crazy. That’s like we passed through another kind of door.”
“And?”
He shrugged. “And I can’t go back. I know that. I can’t bring Lemmy back to life. I can’t go back to the past. Every door I pass through is one way. So I may as well look around, and see what there is beyond the next door, and the next.”
“Hm. If you can’t go back, why won’t you reveal your true name to your fellow colonists?”
“Why should I?”
“That itself is a reaction to your past.”
He had no answer to that. They moved on for a while, walking, rolling, in companionable silence.
They came to one of the ColU’s experimental sites. This was an outcropping of rock, a black basalt, volcanic rock that had erupted in sheets from the sandy ground after some ancient magmatic event. They called this extrusion feature the Lip. Here the ColU had fenced off an expanse of bare rock, perhaps a quarter of an acre, and domed it over with a fine transparent mesh to keep out the native life. Lichen were growing busily on the naked rock, powdery white spots.
The ColU inspected this lichen garden, with sensors mounted on a manipulator arm.
“It’s doing well,” Yuri said.
“I think you’re right. I’ve used a variety of lichen here, some gen-enged, some a hybrid with cousins from Mars. But some of this is transplanted straight from Earth, from Antarctica, from the high deserts, from post-volcanic landscapes where lichen such as this would be the first colonists. What remarkable organisms—and themselves complex, a symbiosis between fungi and photosynthesising bacteria. They dissolve the rock for access to nutrients like phosphorus; they grow filaments to break up the rock, and later the mosses come and grow in the dust, and then plants… I did not manufacture these patches of nascent soil. The lichen are doing it for themselves. How remarkable, Yuri Eden—if you’re curious about anything, be curious about this! These are the true invaders of Per Ardua, the true colonists—”
A light, in the corner of Yuri’s eye. He spun around. A spark, sulphurous orange, climbed into the sky, from above the colony. “That’s a flare gun.”
The ColU immediately backed off, turned, and rolled away, cutting across the bare landscape. “We must return. Emergency, Yuri Eden! Emergency!” And it accelerated, soon outpacing Yuri, the pale light of Proxima gleaming from its upper dome.