The next morning, Pang Xuelin was woken up hungry, and as soon as he opened his eyes, he saw Watney chewing an energy bar.

"This is what I found in the car, it is estimated that Martha left them behind when they went on a mission, a total of four, which can be used as food for us today."

Pang Xuelin took the energy bar, tore open the package, stuffed it into his mouth and chewed it.

With some food in his stomach, Pang Xuelin took a breath and said, "Watney, have you thought of any way?" ”

Watney shook his head and said, "The only way I can think of is to open the airlock and let all the air out of it, but then those plant seeds in the inhabiting chamber and the bacteria produced by our fertile fertilizer will die from the cold and lack of oxygen, and we will not be able to survive even a year when there is not enough food." Alas, it would be nice if there was an air separation plant......"

Pang Xuelin's heart suddenly moved, and he asked, "What did you just say?" Air separation equipment? ”

Watney said, "Yes, air separation equipment, but we don't have it." “

Pang Xuelin said: "But we have an atmospheric regulator!" “

Watney was slightly stunned and said: "The atmospheric regulator can only regulate the oxygen content, it can reduce the temperature to a minimum of 90K, so that the oxygen is liquefied, but the nitrogen with a condensation point of 77K can remain gaseous." However, the freezing point of hydrogen is only 21K, and we have no way to separate it. ”

Pang Xuelin laughed: "We don't need to separate the hydrogen, we just need to separate the oxygen, as long as the oxygen concentration in the perching cabin is reduced to a certain extent, then no matter whether we ignite or do something, the hydrogen will not explode, and then we can use an oxygen tank to spray oxygen into the air, and then use batteries and wires to make electric sparks, so that the hydrogen in the perching cabin can be burned under control, and the hydrogen can be removed slowly." ”

"But if the oxygen level is too low, the bacteria and plant seeds will still die!" “

Pang Xuelin couldn't help frowning, if this still doesn't work, he really doesn't have a good way.

"Wait! I have a way to keep plant seeds and bacteria alive! ”

Watney Road.

"What's the solution?"

"We can reduce the oxygen concentration to a certain level, about one hundredth, and then reduce the temperature in the perching chamber to freezing, at that time, whether it is plant seeds or bacteria, it will enter a state like hibernation, and the oxygen concentration of one percent will not make the hydrogen explode at all, so we don't have to worry about not being able to grow it later!"

Pang Xuelin's eyes lit up and said, "Okay, let's do this!" ”

This method is easy to say, but it is very cumbersome to do.

The two ventured back to the perch, first adjusting the temperature in the pod to freezing, then activating the atmospheric regulator to separate the oxygen, and only when the oxygen content in the perch dropped to one percent before they stopped working.

Then, Pang Xuelin and Watney found a tank of pure oxygen injection and made a small electric spark generator, and it took them a whole day to remove the hydrogen from the perching cabin.

Over the next month, Pang Xuelin and Watney kept the water production to less than 40 litres a day, and the rest of the time was spent cleaning up the hydrogen accumulated in the perch.

After 32 Martian days, the two used 500 liters of hydrazine to make a whole ton of distilled water.

The remaining 100 liters of hydrazine serve as an emergency reserve.

To this ton of water, they added 200 liters of water to the water circulation system, and the remaining 800 liters of water, all mixing them with twenty cubic meters of Martian soil.

……

35th Martian day.

Today is a big day for Pang Xuelin and Martin Watney.

They will go down in history as the first human to farm on Mars.

Today's planting results will also be the foundation for their future survival on Mars.

However, before planting, they have to check the condition of the equipment inside the entire perch.

The perching chamber has a total of three airlock doors, which are located in the living module, the planting module and the energy module.

The planting cabin and the energy cabin are connected by a gate and a living compartment respectively, and the three cabins are arranged in a zigzag structure.

In order to prevent accidents, Pang Xuelin and Martin Watney inspected the heating system, the main battery pack, the nitrogen and oxygen storage tank, the lighting system, the computer system, the water circulation system, the air conditioning system, etc.

Subsequently, the two men completely closed the electronic control system of the airlock door on the side of the planting tank, adjusted it to a mechanical control state, and then sealed it.

For a long time to come, they will no longer enter and exit through the airlock door on this side of the plantation tank.

As for the gate between the living cabin and the planting cabin, they also closed the electronic control system and chose a mechanical control.

The two agreed that at any time, whenever entering and exiting the planting cabin, the hatch must be manually closed.

After all the preparations were completed, the two began the formal planting work.

Watney had already cut the potatoes open and dug holes in the soil of the planting tank.

Pang Xuelin learned from Watney, buried half a potato in the pit, poured a spoonful of fertile fertilizer, added a spoonful of water, and then covered the Martian soil.

For a planting area in the early 100s, it took the two of them two hours to get it done.

"Pong, we'll be able to survive on Mars!"

Pang Xuelin and Watney looked at each other and smiled.

……

Coming out of the planting pod, closing the hatch, the two of them treated themselves to two packets of fried rice in the microwave.

Pang Xuelin said: "Watney, next, we almost have to think about how to restore communication with the earth. ”

Watney took a sip of the drink made from the peptide protein powder, frowned, and said, "Pang, I'm afraid the only way now is to go to Schiaparelli and use the MAV (Mars Liftoff Vehicle) prepared for Ares 4, which landed there in advance, to restore contact with the Earth." “

Pang Xuelin shook his head and said: "For a long journey of 3,200 kilometers, it is too dangerous to rely on a rover alone, and I don't recommend it." ”

Watney shrugged his shoulders and said, "Then can we have a better way?" ”

Pang Xuelin smiled, slowly put a spoonful of rice into his mouth, and said, "There may not be no way. ”

Watney was slightly stunned and said, "What way?" ”

Pang Xuelin got up and took off a topographic map hanging on the wall, put a × on it, and said: "Our current location is in the Asidaria Plain, with a latitude and longitude of 31.2 degrees north latitude and 28.5 degrees west longitude. Do you remember the training we took before we joined the Ares program? Before we officially landed on Mars, we used the rover to carry out large-scale unmanned exploration activities on Mars. ”

Watney looked at the × on the map, his eyes getting brighter and brighter: "Martian Pathfinder, I know, Martian Pathfinder!" ”

The Mars Pathfinder is an unmanned exploration spacecraft launched by NASA in December 1996 and landed on the surface of Mars on July 4, 1997. The Mars Pathfinder was originally planned to work for a week and a month, but in fact, it worked for three months and gained a lot of Martian intelligence that had never been seen before.

Pang Xuelin said: "The location of the Mars Pathfinder is at 28.9 degrees north latitude, 29.6 degrees west longitude, 800 kilometers southwest of us, it only stopped working because there was no power, as long as we pull it back, we can use it to restore communication with the earth." And now that so much time has passed, I think Project Ares command should find out that we're still alive! ”

Watney nodded: "You're right, but the distance of 800 kilometers, 1,600 kilometers round trip, our rover can run for up to three to four hours when fully charged, if the speed is 30 kilometers per hour, a charge can travel 100 kilometers, the problem is that the power of the rover still needs to maintain the temperature in the car, then a charge, at most 50 kilometers." And it would take us three or four hours to fully charge the battery after the journey. It can travel up to 100 kilometers a day, which means that it will take at least 16 days for our rover to bring back the Martian Pathfinder. In addition, we had to carry enough liquid oxygen, carbon dioxide filters and other equipment, and we had to have enough food to ensure ......"

Pang Xuelin smiled: "I have a way to halve the resources consumed on the road." ”

Watney wondered, "What's the solution?" ”

Pang Xuelin said: "Do you remember the radioisotope thermal battery in MAV? （RTG）”

Watney was slightly stunned and said, "Didn't that thing be buried by Commander Lewis's order?" ”

Radioisotope thermal batteries (RTGs) are devices in MAVs.

As a Mars launch vehicle, the MAV is the only equipment used by astronauts to return home.

It will make a soft landing at a predetermined location a few years before the astronauts land on Mars, then wait for the astronauts to arrive, and when they need to return, they will leave Mars on a MAV and dock with the Hermes spacecraft.

In order to ensure that the MAV is reliable in the unmanned state and can carry out system self-test in a timely manner, scientists have installed radioisotope thermal batteries on the basis of solar cells.

This radioisotope thermal battery (RTG) contains 2.6 kilograms of plutonium-238, which is very unstable and can decay all the time to release radiation and energy, and it can produce about 1500 watts of heat and 100 watts of electricity.

Pang Xuelin said: "We can dig it out, put it in the rover, and use it to heat the air in the rover, so that the rover does not need to consume additional electricity to keep warm." ”

"That's a good idea!" Watney clapped his hands, "In that case, it will only take us eight days to bring the Mars Pathfinder back!" A trip to the Schiaprelli crater in the future can also help us save a lot of time. ”

Pang Xuelin said: "That's true, but you don't have to go this time, I'll just drive over, on the one hand, the planting module needs you to keep an eye on, this is the foundation of our survival on Mars, we must not have problems, on the other hand, if I am alone, the consumption of carbon dioxide absorbers and liquid oxygen can be halved, and we must save resources now." ”

Watney hesitated for less than a second before accepting Pang Xuelin's statement.

"Okay, then let's dig up the RTG tomorrow, test the rover again, and then set off."

"Good!"

Pang Xuelin nodded.