INSUBCONTINENT EXCLUSIVE:
Image copyrightCNSAImage caption
Artwork: The Chang'e-4 rover will explore a huge impact basin on the far side
China has launched the first mission to land a robotic craft on the far side of the Moon, Chinese media say.The Chang'e-4 mission will
off atop a Long March 3B rocket from Xichang Satellite Launch Center.The mission will pave the way for the country to deliver samples of
Moon rock and soil to Earth.The landing will not occur until early January, when the probe will descend on thrusters and touch down on the
rugged terrain of the lunar far side
This was probably formed by a giant asteroid impact billions of years ago.The landers will characterise the region's geology and the
composition of rock and soil.Because of a phenomenon called "tidal locking", we see only one "face" of the Moon from Earth
This is because the Moon takes just as long to rotate on its own axis as it takes to complete one orbit of Earth.Though often referred to as
the "dark side", this face of the Moon is also illuminated by the Sun and has the same phases as the near side; "dark" in this context
simply means "unseen".Image copyrightNASAImage caption
The lunar far side has a thicker crust and is more heavily
cratered than the near side
The far side looks rather different to the more familiar near side
It has a thicker, older crust that is pocked with more craters
There are also few of the "mare" - dark basaltic "seas" created by lava flows - that are evident on the near side.The powerful impact that
created the South Pole Aitken Basin may have punched through the crust down to the Moon's mantle layer
Chang'e-4's instruments could examine whether this was the case, shedding light on the early history of our only natural satellite.Seed
experimentThe mission will also characterise the "radio environment" on the far side, a test designed to lay the groundwork for the creation
of future radio astronomy telescopes on the far side, which is shielded from the radio noise of Earth.The static lander will carry a 3kg
(6.6lb) container with potato and arabidopsis plant seeds to perform a biological experiment
The "lunar mini biosphere" experiment was designed by 28 Chinese universities."We want to study the respiration of the seeds and the
photosynthesis on the Moon," Liu Hanlong, chief director of the experiment and vice president of Chongqing University, told the state-run
Xinhua news agency earlier this year.Image copyrightCNSAImage caption
China's Yutu rover, part of the Chang'e-3
mission, explored the Moon in 2013
Xie Gengxin, chief designer of the experiment, told Xinhua: "We have to keep the
temperature in the 'mini biosphere' within a range from 1 degree to 30 degrees, and properly control the humidity and nutrition
We will use a tube to direct the natural light on the surface of Moon into the tin to make the plants grow."Because the landers on the far
side have no line of sight with our planet, they must send data back via a relay satellite named Queqiao, launched by China in May this
year.The probe's design is based on that of its predecessor, Chang'e-3, which deployed landing craft to the Moon's Mare Imbrium region
However, it has some important modifications.China's lunar ambitionsThe lander is carrying two cameras; a German-built radiation
experiment called LND; and a spectrometer that will perform the low-frequency radio astronomy observations.The rover will carry a panoramic
camera; a radar to probe beneath the lunar surface; an imaging spectrometer to identify minerals; and an experiment to examine the
interaction of the solar wind (a stream of energised particles from the Sun) with the lunar surface.The mission is part of a larger Chinese
programme of lunar exploration
The first and second Chang'e missions were designed to gather data from orbit, while the third and fourth were built for surface operations
Chang'e-5 and 6 are sample return missions, delivering lunar rock and soil to laboratories on Earth.Follow Paul on Twitter.
