Stohlberg held a lettuce frond delicately between his fingers.
“I appreciate you taking the time to come down here,” Lindenmeyr said.
Stohlberg shook his head slightly. “Not at all. Truth be told, a lot of our digging equipment was seconded by the Stephenson Project. There’s less work for us now, out at the open-cut site.”
Lindenmeyr and Stohlberg each wore light-weight, long-sleeved ponchos. Lindenmeyr explained that metal halide light lit the hydroponic bay; metal halide emitted more light in the blue spectrum, which accelerated plant growth, but was a carcinogen to exposed human skin.
“We light each of the bays for eighteen to twenty hours each day,” Lindenmeyr said. “Between the halide light and the lengthened days, we’re producing crops in greater yields than on the Quoqasi. The hydroponics facilities in Alphas One, Three and Four are together producing a sufficient excess to feed the population of Alpha-2.”
“I see,” Stohlberg replied. “I feel drunk.”
“That’s the cee-oh-two. We keep the levels pretty high in here, again, for the plants. It’s not dangerous, but it takes some getting used to.”
He looked up from the lettuce and saw, stretched a hundred meters ahead of him, row upon row of plants, aglow in the artificial blue-white light. The greens were simply breathtaking. Lindenmeyr remarked that it was not a colour seen outside the hydroponics facilities; not in the Colonies nor on Fram itself. She spoke of a psychological study done on the journey to Alpha Centauri that had shown that the botanists who worked in the hydroponic labs were on average happier than their peers.
Stohlberg nodded, and asked her, “What is grown here?”
“Lettuce, pak choi, asparagus. Carrots, tomatoes. Mushrooms. Spinach. Plants with high levels of vitamins and minerals. Our staple is soy, of course. Those versatile, little beans pack a lot of nutritional value for the space it takes to grow them.”
Lindenmeyr explained the process behind the hydroponic crops. She called it Soilless, Controlled Environment Agriculture. The plants existed on a nutrient solution that flowed constantly past their roots; she pushed back the overhanging fronds of a head of lettuce and pointed to the bank in which the plant sat. Here there was a shallow channel of water, running through a bed of clay aggregate pebbles upon which the roots rested. The pebbles were not entirely submerged by the solution.
“Thus, the roots are well oxygenated while still fed by the nutrient solution.”
Stohlberg watched the nutrient solution move past the roots of the plants in this bank. Lindenmeyr rattled off a list of elements made soluble and dissolved into the water: essentials like iron, manganese, magnesium and zinc; and macronutrients like potassium nitrate and calcium nitrate. There were also sulphates mixed in for the sulphur.
“I didn’t realise until now just how much of what we dig up in the mines goes into our bodies,” Stohlberg commented. “From the Earth we come, to the Earth we return.”
Lindenmeyr frowned. “An anachronistic adage.”
Lindenmeyr pointed to the banks arranged in long rows along the length of the bay. Each of the rows was inclined at an angle, which allowed the nutrient solution to run easily and prevented the solution from pooling. Stohlberg noticed that these rows were not continuous, but that the banks were segmented every ten to fifteen meters; this, Lindenmeyr replied, was to prevent the depletion of nitrogen which occurred when too many plants were nourished from a single nutrient feed.
“There are plant rooms attached to each of the hydroponic bays,” Lindenmeyr said. She pointed to the wall on their right. “Enormous carbon filters through which we run the nutrient solution. There we can monitor pH levels, salinity, flow rate.”
“And top up the solubles?”
Stohlberg lowered his nose to the lettuce frond and sniffed deeply.
“Sera, this is wonderful. But I don’t know how a geologist could help here. Fram is thousands of years away from having soil – maybe tens of thousands. Sure, the regolith has magnesium, potassium, sodium, chloride. But there’s no nitrogen, and it’s completely unable to retain moisture.”
Lindenmeyr looked up at Stohlberg with an amused grin. “I’m a botanist. I know that!”
Again, she carefully pushed back the lettuce heads and scooped a handful of the pebbles from the nutrient channel. They were a variety of rich colours, Stohlberg saw now: brown and red and terracotta. Lindenmeyr described how the pebbles had been baked from the clay of Earth and Mars – the rusty red pebbles were clearly Martian – and had been carried with us on the journey from Sol. After each crop rotation the pebbles were washed in a solution of hydrogen peroxide.
Lindenmeyr cracked open a pebble; Stohlberg saw that it was porous, and criss-crossed by tiny lines invisible from the exterior.
“Are those fracture lines? From firing in the kiln?” he asked.
Lindenmeyr shook her head. “No. This is root growth. From thousands of generations of crops grown in the same clay aggregate. For almost six years.”
She explained that this root growth did not have a detrimental effect on subsequent crop yield, but only if the pebbles were sterilised in hydrogen peroxide after each harvest – an enormous investment of hydrogen and oxygen.
“If we were to use a local product as a medium,” Lindenmeyr spoke enthusiastically, “we could further tighten down the life-support loop by cutting out the hydrogen peroxide wash completely.”
Stohlberg nodded. “But there’s no clay on Fram.”
He grinned. “I’m a geologist. I know that!”
He listened while Lindenmeyr explained the need for a mixture of perlite and vermiculite – fusions of basalt and granite – superheated until expanded into glassy pebbles. If produced in sufficient quantities, the hydroponics facilities of the Colonies could simply discard the clay aggregate and use the disposable perlite/vermiculite mix.
She asked, “Do you know how many tonnes of H and O that would free up?”
“You won’t get much from the open-cut site,” Stohlberg continued, oblivious to her question. “The tails are being ransacked for uranium. And the Yom Kippur site is well past the bedrock. Actually, I think the Stephenson dig sites are the most promising – they’ve had a lot of trouble with basalt sheets around Charlotte Station.”
Stohlberg smiled, leaned down and kissed Lindenmeyr on the cheek.
“I’ll get to work!”