At 6:17 a.m., the screen on the main control console was still flashing.

Chen Hao stared at the replay window, dragging out that less than one-second heat source trajectory for the fifth time. The surface temperature on the northern ridge in the video suddenly jumped, like someone blinking, and then disappeared.

"Looking again?" Nana's voice came from the side.

"This thing is too short." Chen Hao didn't look up. "It's so short it's like the equipment is malfunctioning."

“But it appeared on two different sensors.” Nana stood to his right, the optical module aligned with the projection area. “Similar fluctuations were also observed in the underground cavity in the eastern valley, with a time difference of three minutes.”

Chen Hao finally turned his head. "You mean, one was emitting heat underground, and the other flashed on the mountain, and then the two signals coincided?"

"Current data supports this correlation," she said.

Susan then pushed open the door and came in, carrying a kettle of hot water. She placed the water on the table and casually took off her coat, draping it over the back of the chair.

"You two look worse than I did when I was brushing my teeth in the mirror this morning."

"I've discovered something." Chen Hao pulled up the map. "Here, here." He tapped twice. "There's residual heat underground, and a heat source flashed across the mountain. The timing is close, and the frequency is strange."

Susan walked over and stared at it for a few seconds. "Not an animal?"

“Too fast,” Nana said. “The body temperature movement wouldn’t last only 0.8 seconds.”

“It’s not the weather either.” Susan touched the edge of the screen. “There were no thunderstorms last night, and no record of ground temperature rise.”

The three of them were silent for a few seconds.

"Should we investigate?" Susan asked.

“I’ve already checked.” Chen Hao opened his portable terminal. “I noted down the coordinates last night. I was planning to wait until dawn to talk about it, but as soon as you walked in, I felt like—if I waited any longer, I’d scare myself to sleep.”

Nana began downloading the geological model files. "I'll compare them to common natural discharge phenomena on the planet. If the signal comes from mineral reactions or thermoelectric currents, I should be able to find matching cases in the database."

"Then you go ahead with your work." Susan picked up her thermos and took a sip. "I'm going to the warehouse to get some sampling tools, just in case I need to go out and take a look."

"Don't go alone," Chen Hao said. "Even if it's just a hot stone, you can't go far by yourself."

"I know." She smiled. "I'm not going on a date."

Ten minutes later, the three stood on a small platform outside the base. The morning breeze made them feel a little stiff, and the outline of the distant valley was blurred, like a pencil line that had been smudged.

Nana unfolded the foldable sensor array and mounted it on the stand. Chen Hao was in charge of connecting the power, muttering as he plugged in the cables, "This thing is more delicate than my router."

"It can detect electric field changes of one ten-thousandth of a volt." Nana pressed the switch lightly, and the indicator light turned green. "Now, let's start collecting the basic background values."

Susan squatted on the slope, brushing aside a layer of loose snow and gravel. "The soil here is different." She reached out and picked up a piece of dark gray rock. "It has a high iron content and slight signs of oxidation on the surface."

Nana took the stone and scanned it. "The iron-nickel alloy content is 34%, which meets the conditions for local magnetic disturbance."

"What do you mean?" Chen Hao asked.

“When the temperature difference between day and night exceeds 60 degrees Celsius, these types of mineral layers will generate weak currents.” She pulled up a simulation diagram. “The pulse frequency is concentrated at around 2,000 hertz—which is consistent with the abnormal signal we have been listening to.”

"So the rocks generate their own electricity?" Chen Hao scratched his head.

"That's one way to understand it."

"What about the heat source on the mountain?"

“It might be a concomitant phenomenon.” Nana zoomed in on the regional heat map. “Underground heat rises through the fissures, causing a brief rise in surface temperature. The sensor captured that moment.”

Susan suddenly stood up. "There's a gap over there."

She pointed down the slope. A thin crack in the frozen soil lay there, less than two fingers wide, but you could see very faint white steam rising from it.

“Shallow steam,” she said. “This indicates that there is indeed thermal activity below.”

Nana immediately turned the sensor in that direction. The data showed that the electric field oscillated slightly, then subsided after four seconds.

"The signal pattern is 92 percent similar to last night's," she said.

Chen Hao breathed a sigh of relief. "So, no one's hiding underground sending us Morse code?"

"There is currently no evidence of manipulation," Nana said.

“That’s natural.” Chen Hao plopped down on the ground. “I thought I’d finally run into an alien spy.”

“If they were spies, they wouldn’t use such a primitive way to communicate.” Nana put away her equipment. “This kind of signal can’t even interfere with an old-fashioned radio.”

Susan brushed the dirt off her hands. "So, all that tension we've been going through was just this planet hiccuping?"

"Almost." Chen Hao stood up and patted his pants. "Next time it makes a loud noise, remember to record it and use it as an alarm clock."

It was past nine in the morning when I returned to the control room. Sunlight streamed through the window, falling on the control panel and casting beams of light that reflected off the drifting dust particles.

Nana compiled all the data into a report and uploaded it to the local log. Chen Hao crossed out the "Suspicious Signals" column on the whiteboard and changed it to "Environmental Monitoring Upgrade".

"In the future, analyze these kinds of situations first before reporting them," he said. "Don't keep quiet about them."

Nana looked at him. "I judged the information to be of low priority at the time."

"I know," Chen Hao waved his hand, "but next time, even if you think it's a small matter, just say so. We can't afford any misunderstandings right now."

She nodded. "Understood."

Susan flipped through her notebook. "I suggest two inspections a day, one in the morning and one in the evening, focusing on the east and north sides. I can bring people to take turns."

“Okay.” Chen Hao wrote it down. “And make a simple marker post, so that one day our own people might step on it and think there’s an earthquake.”

“I will design low-power sensing nodes,” Nana said. “The system will automatically alert you if the electric field or temperature changes abruptly beyond a threshold.”

"High technology plus simple methods, perfect." Chen Hao stretched. "Finally, I can get my mind back on the important matter."

Susan packed her bag, ready to leave. "I'm going to the warehouse to get some PVC pipes and sealant to make a few protective covers."

"Be careful," Chen Hao said. "Don't get your feet pricked by nails."

“You are.” She turned around and smiled. “Don’t fall asleep on the chair and roll off.”

After the door closed, only two people remained in the room.

Nana continued debugging the program, her fingers rapidly tapping on the keyboard. Chen Hao leaned back in his chair, watching her work.

“Actually, what you just said was quite human,” he said.

Which sentence?

"When it's said that information has a low priority."

She paused for a second. "I just did a logical assessment."

“But you never used to ‘assess’ this,” Chen Hao grinned. “You would just report it directly, no matter how small the matter was.”

“Team efficiency needs to be balanced,” she said. “Concealing some non-urgent information may reduce unnecessary resource mobilization.”

"It sounds like an excuse."

"It's more like learning."

Chen Hao laughed. "You're learning pretty fast, aren't you? Are you going to steal my job in a couple of days?"

“I’m not eating,” she said.

“Oh yeah.” He scratched his head. “You just drink electricity.”

At 12:03 PM, the three of them reunited in the control room.

Susan handed in the first inspection schedule, Nana completed the first draft of the early warning script, and Chen Hao updated the task list.

"The signal problem is solved," he said. "Although it was a false alarm, it reminds us that this place is not simple."

“The natural environment may also pose risks,” Nana added.

“So I’ve decided,” Chen Hao wrote on the whiteboard, “to conduct a full-band scan every three days, plus two on-site inspections daily. Any problems found will be recorded on the spot, without further delay.”

Susan nodded. "I can take charge of organizing the logs."

“Okay.” Chen Hao circled her name. “Nana will be in charge of data analysis and alarm mechanisms. Carl and I will check the equipment status regularly.”

"What's next?" Susan asked.

"Get to work," Chen Hao decided. "The material substitution plan must be finalized today; the workshop is waiting to start operations."

Susan got up to grab her bag. "I'll go find Carl now to coordinate the vine removal process."

Nana also switched to the work interface. "I'm updating the geological parameters in the database to avoid errors in subsequent calculations."

Chen Hao sat back in his chair and opened his tablet to revise the plan document. Just as he entered the table of contents, Nana suddenly spoke up.

"etc."

He looked up.

“We just received new ground motion readings,” she said. “The amplitude is small in the direction of the eastern valley, but the waveform is asymmetrical.”

Chen Hao slowly sat up straight.

"Not the same regular pulse as last time?" he asked.

“No.” Nana pulled up a chart. “This time it’s intermittent low-frequency vibrations, and the intervals are getting shorter and shorter.”

Susan stopped in her tracks.

How short?

“The first interval is 120 seconds.” Nana stared at the data stream. “The second time, 80 seconds. The third time… 40 seconds.”