He felt someone sliding into the port-side couch, bulky in his space suit. Shigeru pressed his face close to the view-port, his face illuminated by the bright, white reflections from outside. “I had to see,” he said. “You have no idea how I’ve wanted to see these things with my own eyes, instead of through the optics of teleoperated probes!”
“Is that Europan life, then?” Jeff asked. Some of the brown stuff looked a lot like moss, with long filaments waving in the current created by hot, upwelling water.
“We think so.”
“You think so? Don’t you know? Haven’t you gathered specimens?”
“Oh, certainly. And we’ve given it the provisional genus name of Muscomimus, the ‘moss-mimic.’ But Dr. Red-mondson, our chief of exobiology, is not yet convinced that it is a true life form. It may simply be an unusual accretion of sulfur and carbon compounds in long-chain molecules, a purely nonorganic process.”
“It looks like it’s growing…and reproducing. All over the E-DARES’ hull.”
“We’ve seen whole forests of the stuff growing on the bottom of the ice. And it is gathering raw materials, food, if you will, from the water, and it seems to carry on this process by drawing energy—in this case, thermal energy from the hot water coming up from the E-DARES’ anti-icers—from its surroundings. But, well, we’re still working on finding a good definition for the word life.”
Jeff chuckled. “That’s a hell of a note.”
“What?”
“That the more we learn, the more we find out about the universe around us, the harder it is to answer the simple questions, like ‘what is life?’”
“Basic questions, Major. Not simple. In fact, that one may be one of the most complex questions there is.”
“Yeah?”
“Yes. Just ask any AI.”
The Manta continued its slow turn, and the E-DARES hull slid out of view off to the right. Tiny motes danced in the sub’s searchlight beams, a snowstorm of particles.
“Europamegabacter sulfurphilos,” Shigeru said. “That is alive.”
“It looks like dirt,” Jeff said. “Or snow.”
“It appears to be a close analogue of a life form known on Earth. Not related, of course, but an example of convergent evolution.”
“Yes?”
“A bacteria discovered off the coast of Angola seventy years ago. A single cell, yet it’s large enough to be seen by the naked eye—about the size of a period in a sentence, in fact, thousands of times larger than an ordinary bacterium. Most of that size is taken up by a huge vacuole, in which it stores nitrates to help in the metabolism of sulfur.”
“That stuff looks a lot bigger.”
“It is. Some specimens reach ten to fifteen millimeters in diameter. But they are single-cell organisms, nonetheless.
“So far, all of the life we’ve discovered on Europa is carbon based, like ours, but dependent on sulfur for metabolic processes. Just like the giant bacteria on Earth, or the sulfur-loving life discovered at the openings of volcanic vents in Earth’s oceans, at the intersection of seismic plates. You see, it doesn’t need light, as photosynthetic life does.”
Jeff could only shake his head. Here, things that looked like they were alive and growing might well not be alive at all, at least in the conventional sense, while stuff that looked like dirty snow caught in the Manta’s lights was following the same patterns of life laid down by organisms on Earth.
“Whoa,” Carver said suddenly. “Hey, Major. You hear that?”
“Hear what?”
“Listen.”
Yes…he did hear something. It was so faint at first he’d not been able to hear over the background conversation, the hum of the air ventilation system, the hollow rush of water across the vessel’s hull. Slowly, though, it grew louder, swelling to a low, eerie ululation, mingled with rattling clicks and keening, high-pitched shrieks, but still so distant you had to strain to make it out.
“The Singer, Chief Carver,” Jeff said.
“Affirmative, sir. I was picking up some as soon as we hit the water, but it didn’t really become audible until we got down beneath the ice. It’s muffled quite a bit by the hull. Must be pretty loud outside, for us to hear it this clearly.”
“Yes,” Shigeru said. “We didn’t hear it until we lowered hydrophones well beneath the icecap and into the ocean proper. But the sound, especially the lower registers, travels quite well for astonishing distances. The sound waves reflect between the ice and the bottom, you know, and can travel all the way around the moon.”