Scientists are working to overcome obstacles ahead of the planned launch of a probe to Mars next year.
Sun Zezhou, chief designer of China's Chang'e 4 lunar probe, spoke quickly but clearly.
"Every time I see the moon, I think about how Chinese probes have left permanent footprints on it, especially Chang'e 4, the first spacecraft to soft-land on the far side. As a member of that mission, I'm very proud," he said, his eyes shining brightly.
Chinese engineers began to plan the Chang'e 1 lunar probe in the 1990s, when Sun joined the team.
The country only had a monitoring system for near-Earth satellites, so communicating with the moon at a distance of 380,000 kilometers was a big challenge.
"When I first heard the old experts discussing lunar exploration in 1996, I felt the moon was very distant," recalled Sun, who majored in monitoring and communication.
His eyes now turn to Mars whenever the nights are clear.
"Now, 380,000 km is no longer far, but 400 million km is a new headache," joked Sun, whose team is developing a Mars probe.
China plans to launch the probe next year, and aims to complete orbiting, landing and roving in one mission, which would be an unprecedented achievement.
"This shows China's innovative spirit in space exploration," Sun said.
Mars is a completely new challenge for Chinese engineers.
They have to solve problems such as long-distance monitoring, control and communication between Earth and Mars, in addition to working out how to land the probe.
Since the 1960s, more than 40 Mars missions have been undertaken, and about half of them have been successful.
Sun's biggest concern is the Martian atmosphere.
"When we were designing the lunar probe, we thought it would be great if the moon had an atmosphere. The probe had to carry lots of propellants. About two-thirds of the takeoff weight was propellants," he said.
"But when we started to develop the Mars probe, we found the Martian atmosphere very troublesome. Although we don't need to carry so many propellants, the uncertainty caused by the atmosphere is much more complicated. Sometimes, it relies on luck."
He used the phrase "very troublesome" to describe several difficulties in the development of the Mars probe. However, his team has risen to those challenges.
"It is pressure that brings about technological progress," Sun said.
As a child, Li Fei, 39, dreamed of space. After studying robotics at Tianjin University, he joined the China Academy of Space Technology in 2009, becoming a key member of the Chang'e 3 and Chang'e 4 teams.
"Our probe can be seen as a robot. The landing process of Chang'e 4 was totally autonomous. The probe could identify obstacles on the moon. In future space exploration, especially to Mars, Jupiter and even Pluto, communication between the probe and Earth will be longer and more difficult. So we need smarter robots," Li said.
When the team tested the hovering technology of the probe's lander in the suburbs of Beijing during a freezing winter, they had to get up at 3 am every day because the probe's instruments only worked in low temperatures.
After conducting trials every day, they had to analyze the data. This routine continued for a month.
In the 1960s and '70s, NASA's lunar landings were controlled by astronauts, while the Soviet Union's lunar probes lacked hovering and obstacle-avoidance technology. China first achieved autonomous hovering and obstacle avoidance during the lunar landing process.
A Russian space engineer told Li that he and his colleagues had watched a video of the Chang'e 3 landing more than 100 times to study how it was done.
"We studied the Soviet Union's lunar missions countless times, and now they are learning from us," Li said.
"The greatest joy of deep-space exploration is to discover the unknown and contribute to the development of science and technology."
According to Sun, deep-space exploration is always a high-risk venture.
"We can never stop. There are always new challenges. This is the attraction. If we repeat the same thing over many years without challenges, we will lose the meaning of exploration," he said.
"When we successfully land on Mars, we might feel that Jupiter is far away. But as China continues to advance deep-space exploration, Jupiter will become closer and closer."
Sun and members of his team who have taken part in both the lunar and Mars missions claim to be "the happiest people on Earth".
At the age of 33, Sun was deputy chief designer of the Chang'e 1 probe－the youngest space engineer in the post in China at the time.
The average age of the main scientists and technologists in China's lunar exploration and manned space programs, the Beidou Navigation Satellite System and other space science teams is about 30.
"We are fortunate to be here during the rapid development of China's space industry, which brings both lots of opportunities and pressure," Sun said.
Li said the new generation of Chinese space engineers has inherited its predecessor's spirit of selfless dedication, but the members are better educated and have a global vision, stronger innovation ability and more-flexible minds.
Chen Jianxin, a designer of the thermal control system of the Yutu 2 lunar rover, said: "As a new generation of space engineers, we have mastered more-powerful design tools. We hope also to achieve breakthroughs in innovation. Going to the far side of the moon is like climbing an unexplored mountain. We hope our lunar rover will make pioneering discoveries."