China plots a course for the 'dark' side of moon

In a white paper published on Tuesday, the Chinese government said its Chang'e 4 mission aims to explore the mysterious far side of the lunar surface.

The plan envisages the project fulfilling the three strategic steps of "orbiting, landing and returning" from the distant surface of Earth's nearest neighbor.

After a "soft landing" on the moon, it's planned that the rover will map contours and surface features, as well as looking at the geology on the far side. It's hoped that the probe might be returned with soil samples, and bring back clues about how the moon formed.

"Geological survey and research as well as low-frequency radio astronomy observation and research will be carried out targeting the landing area on the far side of the moon for a better understanding of the formation and evolution of the moon," said the white paper, which envisages 2018 as a launch date.

Not completely in the dark

The "dark" tag is something of a misnomer, being unrelated to the amount of light that reaches the far side of Earth's nearest neighbor.

Tidal forces from the Earth have slowed the Moon's rotation so that one side constantly faces the Earth, a phenomenon called tidal locking, but both sides of the Moon experience two weeks of sunlight followed by two weeks of night. The far side is fully shrouded in darkness only when we perceive the moon as being full.

The term "dark" instead refers to a sense of mystery - with the far side of the moon unseen by human eyes until man was able to send spacecraft around it. The far side was first imaged by the Soviet Luna 3 spacecraft in 1959. 

Famously, the crew of Apollo 13 photographed the far side of the moon as they used lunar gravity to slingshot their crippled spacebound craft back in the direction of Earth. Those and subsequent Apollo images show a more pockmarked appearance than on the near side with its lunar "seas" or "maria."

Radio telescope plan

In truth, the near side is a bit lighter thanks to "Earthshine" - the reflected light from our planet onto the lunar surface - light which never reaches the dark side.

In a similar way to that light, the Moon's far side is also shielded from radio transmissions from Earth, something that would make it the ideal location for a radio telescope. A number of bowl-shaped craters would provide natural formations for a stationary telescope similar to one here on Earth, in Arecibo, Puerto Rico. They could keep in touch with Earth stations using specially placed relay satellites.

It's not the first inkling we've had that China's plans to land on the far side in the near future, but the white paper marks a firm official statement of intent.

Space security expert He Qisong told the AP news agency that the announcement means China probably had the basic technology in place to achieve its goal. "China never talks big and says something it's unable to achieve," said Qisong.

Popular with space buffs

China has already landed a probe on the near side of the moon, deploying the rover Jade Rabbit as part of its Chang'e-3 lunar mission. The project proved a hit with Chinese space fans, who had been asked to name the rover and who followed its "first person" social media account of life on the lunar surface.

In other parts of the white paper on Tuesday China reiterated its plan to launch a Mars probe by 2020, saying it aims to bring back samples from the Red Planet. It also aims to explore the Jupiter system and "conduct research into major scientific questions such as the origin and evolution of the solar system, and search for extraterrestrial life."