Chen Hao wiped his face and stared at the data curve on the main control panel screen. The line representing the solar thermal efficiency had been stable above 75 for almost three hours.

He turned to look at Nana, "Our solar panel is finally working."

Nana didn't look up, her finger sliding across the control panel. "The system is running normally, but the weather forecast shows that cloud cover will rise to 89 percent in the next 48 hours."

"Does that mean it'll be cloudy for two days?" Chen Hao grinned. "Doesn't that mean we'll have to rely on the old stove for fuel again?"

“Yes,” she said. “Energy reserves are still insufficient to support long-term consumption.”

Chen Hao propped himself up from the chair and stretched. His portly body swayed as he walked to the tool rack in the corner, pulling out a pile of old parts. He picked up a rusty metal arm, shook off the dust, and said, "This thing's from a mining robot, right?"

“Model M-7, it’s been scrapped.” Nana walked over and glanced at it. “The hydraulic system is damaged, but the motor is still usable.”

“Then let’s dismantle it.” Chen Hao put the robotic arm on the ground. “Anyway, it’s just sitting idle. Didn’t we agree to work on geothermal energy? Let’s start now.”

Nana paused for half a second, "There is currently no professional drilling equipment, the underground structure is unknown, and there are risks in starting operations rashly."

“I know.” Chen Hao squatted down and pried open the outer shell. “But don’t you have a database? Look up how to make something that can drill holes.”

Nana's camera flashed slightly as she accessed the internal database. A few seconds later, a set of assembly drawings was projected onto the ground. "The M-7's rotary drill bit and hydraulic push rod, combined with a solar pump unit for power, can be modified into a low-power vertical drilling rig."

"It sounds like a puzzle," Chen Hao laughed. "I like it."

The two began disassembling the robot. Chen Hao was responsible for tightening screws and cutting wires, his movements slow but steady. Nana, on the other hand, precisely separated the usable parts, arranging each piece of metal neatly according to its category.

“This gear is badly worn.” She handed over a small part.

"This will do." Chen Hao took it and stuffed it into his backpack. "If it really gets stuck, we'll figure out another way."

Around noon, assembly was complete. A crooked drilling rig stood in the corner, with exposed pipes and a piece of the casing missing, but the motor hummed when powered on.

"As long as it can turn around, that's fine." Chen Hao patted the fuselage. "Where to dig next?"

Nana opened the geological scan map and pointed to the southwest corner of the base. "Below the water reservoir, the soil layer is stable and far from the load-bearing area. I suggest drilling a pilot hole with a diameter of 30 centimeters."

"Okay, let's go there."

They moved the drilling rig into position. The ground was originally covered with metal plates, which Chen Hao peeled off piece by piece, revealing the frozen soil underneath. He swung the pickaxe a few times, the impact making his hands numb.

"This soil is as hard as stone."

"Use a heated spray gun to soften the surface," Nana said, handing over the tools.

Flames erupted, and the soil began to smoke and loosen. The two men took turns operating the machine, and after more than an hour, they dug a deep pit. The drill was secured in, the support frame was reinforced, and everything was ready.

"Ready to start," Nana said.

"Wait a minute." Chen Hao took out a pen and a piece of paper from his pocket, wrote a few words and pasted them on the side of the drilling rig—"Geothermal Well No. 1".

"Don't forget what this is for later."

Nana glanced at the note, "The name has no practical functional meaning."

“It’s meaningful.” Chen Hao patted the machine. “Giving it a sense of ritual will give it the energy to work.”

The drill bit slowly descended, and the moment it touched the ground, the motor noise suddenly became deep. Rock fragments flew everywhere as the drill bit gradually sank deeper into the ground.

The first five meters went smoothly. Monitoring data showed that the rock strata were uniform and the temperature was rising slowly.

"Eight degrees... twelve degrees... seventeen degrees," Chen Hao read out the readings. "That's still within the normal range."

When it reached the eighth meter, the drilling rig suddenly shook and the sound became hoarse.

"Stuck?" He frowned.

"Insufficient power." Nana checked the current. "The drill bit is experiencing too much resistance. I suggest pausing the process."

Chen Hao turned off the power and took a breath. "I was really afraid it would just stop working."

They waited ten minutes to allow the motor to cool down. During this time, Nana adjusted the drilling speed parameters and reduced the drilling force.

“Try again,” she said.

After restarting, the drill bit slowly continued to descend. Three meters later, at a depth of eleven meters, the sensor alarm sounded.

“Temperature anomaly.” Nana quickly pulled up the image. “A local area reached 63 degrees Celsius and continues to rise.”

Chen Hao's eyes widened. "It's so hot! Is there a fire underneath?"

"It's more likely to be a groundwater-thermal cycle," Nana analyzed. "Shallow geothermal activity is commonly found in fault zones or hot spring veins."

As soon as he finished speaking, a wisp of white steam rose from the edge of the drill hole.

"Steam is coming out!" Chen Hao jumped back a step. "Is it going to explode?"

“Pressure is building up.” Nana immediately cut off the power. “Manually release the pressure relief valve.”

Chen Hao reached out to turn the small valve next to him. With a click, a burst of hot air shot out, hitting his glove and burning his hand.

"Oh dear! This is no joke."

"Pressure has been released." Nana confirmed that the pressure had returned to zero. "Prepare to deploy the high-temperature probe."

She took out a thin metal tube with a sensor at the tip and slowly inserted it through the drill hole.

"Twelve meters... fifteen meters..." she counted as she monitored the distance.

Once the probe reaches the bottom, it begins transmitting data back. A new curve appears on the screen.

"The water temperature is 78 degrees Celsius," Nana said. "The flow rate is 1.2 liters per minute, and it contains trace minerals, making it suitable for indirect heat exchange."

Chen Hao stared at the numbers for five seconds, then suddenly burst out laughing.

"We've struck gold!"

"Currently, only the existence of the heat source has been confirmed," Nana cautioned. "A safe extraction mechanism has not yet been established."

"I know," Chen Hao waved his hand, "but at least I know it's not just a waste of time. This temperature is warm enough to keep the house warm."

"The problem is how to extract heat without causing leaks or corrosion," she said. "Groundwater may contain acidic components, which ordinary pipes cannot withstand in the long run."

Chen Hao scratched his head, "Then what should we do? We can't just stay here looking at data every day, can we?"

"I suggest sealing the back pressure to keep the heat source closed." Nana pulled up the new model. "The subsequent design will be a closed heat exchange system that absorbs heat through external pipes to avoid direct contact with the water source."

"That sounds complicated."

"New materials and sealing technologies are indeed needed."

Chen Hao thought for a moment, then slapped his thigh and said, "Then I'll remember this! We'll start construction when we find suitable materials later."

After he finished speaking, he bent down and picked up the note that read "Geothermal Well No. 1," only to find that it was wrinkled from the steam. He found another piece of wood, wrote the same words on it with a marker, and nailed it to the support at the edge of the borehole.

"Leave a mark so I don't forget."

Nana backs up all detection data simultaneously and sets up a timed monitoring program to automatically record temperature changes every half hour.

"The data will be continuously updated," she said. "A second verification can be conducted tomorrow."

"Okay." Chen Hao stretched. "I've accomplished something big today."

He turned to leave, but his foot slipped, and he almost fell. Looking down, he saw that the soles of his shoes were covered in a sticky mixture of mud and mineral residue that had solidified from the steaming hot water.

"This place is impassable," he muttered. "We'll have to lay a plank later."

“Cleaning is not a priority,” Nana said. “The current focus is on ensuring the borehole is sealed.”

"You only know about priorities," Chen Hao chuckled as he polished his shoes. "Hey Nana, if we really get geothermal heating up, won't we be able to lie down and keep warm?"

"It depends on system stability and maintenance frequency."

"Can't you just say it straight?"

"Facts are satisfying."

Chen Hao shook his head and followed her towards the control room. Neither of them spoke on the way; only the drilling rig's cooling fan was still humming softly in the distance.

Back at the console, a steady red line was displayed in the center of the screen—that was the temperature data from underground, consistently above 75 degrees Celsius.

Chen Hao lay on the platform, staring at the line and grinning foolishly.

"I never expected that there would be a hot water pool hidden beneath our base."

Nana is organizing her log. "Based on the available information, it is speculated that the heat source has existed for many years and may be driven by residual heat from deep magma."

"Sounds like a volcano."

"Inactive state, no signs of eruption."

"That's good." Chen Hao sat up straight. "Otherwise, one day you might fall asleep and find your house sprayed into the sky."

"The probability is less than three in a thousand."

"You really know how to calculate."

He reached out to touch the mouse, but Nana stopped him as soon as he got close.

“Your hands are contaminated beyond the safe limit,” she said. “Please clean your hands before operating the equipment.”

"I didn't get it dirty on purpose." Chen Hao withdrew his hand. "I just got it on my hands while moving the drill."

He took out a wet wipe, wiped himself a couple of times, and sat down again.

"What's the next step?" he asked. "Should we dig deeper, or wait until we have all the materials?"

“It is not advisable to expand the borehole at this stage.” Nana pulled up the geological profile map. “We must first simulate the heat exchange efficiency and pipeline layout to prevent energy loss or structural damage.”

"So we still need to draw diagrams?"

"yes."

Chen Hao sighed, "I thought that once we found a heat source, we could immediately connect the water pipes."

"Energy development should be carried out in a gradual manner."

"Alright, you're right again." He smiled. "But it's okay, we have a direction now, let's take it slow."

He stood up, stretched his neck, and looked out the window at the darkening sky.

"I'm a little tired today, but it was worth it."

Nana did not respond, but simply set the probe recycling program to run automatically at 6 a.m. the next morning.

Chen Hao yawned and was about to say something when the control panel suddenly emitted a short notification sound.

The temperature curve on the screen flickered slightly.

The temperature, which had been stable at 78 degrees Celsius, suddenly rose to 79.3 degrees Celsius.

Before he could react, the data dropped again.

What just happened?

Nana quickly retrieved the millisecond-level records.

“A brief fluctuation,” she said. “The reason is unknown.”

Chen Hao leaned closer to the screen.

The red line lay there quietly, as if nothing had ever happened.