“Sure is wetter. Look at the walls.”
In her headlamp the brown-red rock had a sheen. “Ice! Enough water to stick! Last week some of this stuff was all the way up to the entrance.”
“I can see fingers of fog going by me. Who woulda thought?”
She let herself down slowly, watching the rock walls, and that was why she saw the subtle turn in color. The rock was browner here, and when she reached out to touch it there was something more, a thin coat. “Mat! There’s a mat here.”
“Algae?”
“Could be.”
“Hot damn!”
She let herself down further so that he could reach that level. The brown scum got thicker before her eyes. “I bet it comes from below.”
She contained her excitement as she got a good shot of the scum with the recorder and then took a sample in her collector rack. Warmer fog containing inorganic nutrients would settle as drops on these cooler mats. Just like the toads emerging from their burrows in the desert?
Analogies were useful, but data ruled, she reminded herself. Stick to observing. Every moment here will get rehashed a millionfold by every biologist on Earth…and the one on Mars, too.
Marc hung above her, turning in a slow gyre to survey the whole vent. “Can’t make out the other side real well, but it looks brown, too.”
“The vent narrows below.” She reeled herself down.
“How does it survive here? What’s the nutrient source?”
“The slow-motion upwelling, like the undersea hydrothermal vents on Earth.”
Marc followed her down. “Those black smokers?”
She had never done undersea work, but everyone was aware of the sulfur-based life at the hydrothermal vents. Meter-long tube worms and ghostly crabs. They harvested from the bacteria that existed on chemical energy in the warm volcanic upwelling. The vent communities on Earth were not large, a matter of meters wide before the inexorable cold and dark of the ocean bottom made life impossible.
She wondered how far away the source was from here. Kilometers?
Down. Slow, careful, watch your feet.
In the next fifty meters the scum thickened but did not seem to change. The brown filmy growth glistened beneath her headlamp as she studied it.
Poked it. Wondered at it.
“Marsmat,” she christened it. “Like the algal mats on Earth, a couple of billion years ago.”
Marc said wryly, puffing, “We spent months and only found fossils, up there in the dead lake beds. The real thing was hiding from us down here.”
Ten meters more. Reeling out the impossibly thin black cable, the life cord.
The walls got closer and the mist cloaked them now in a lazy cloud. “You were right,” Marc said as they rested on a meter-wide shelf. They were halfway through their oxygen cycle time. “Mars made it to the pond scum stage, and it’s still here.”
“Not electrifying for anybody but a biologist, but better than just fossils. This is more than just algal scum. It implies a community of organisms, several different kinds of microbes aggregated in, okay, slime—a biofilm.”
She peered down. “You said the heat gradient is milder here than on Earth, right?”
“Sure. Colder planet anyway, and lesser pressure gradient because of the lower gravity. On Earth, one klick deep in a mine it’s already fifty-six degrees C. So?”
“So microbes could survive farther down than the couple of klicks they manage on Earth. They’re stopped by high heat.”
“Maybe.”
“Let’s go see.”
“Now? You want to go down there now?”
“When else?”
“We’re at oxy turnaround point.”
“There’s lots in the rover.”
“How far down do you want to go?”
“As far as possible. There may be no tomorrow. Look, we’re here now, let’s just do it.”
He looked up at his readouts. “Let’s start back while we’re deciding.”
“You go get the tanks. I’ll stay here.”
“Split up?”
“Just for a while.”
