A Chinese spacecraft is expected to become the first ever to land on the moon’s far side, in a milestone for human space exploration.
The craft is aiming to land in the unexplored South Pole-Aitken basin, the largest, oldest, deepest crater on the moon’s surface.
The robotic probe, Chang’e 4, entered an elliptical path around the moon at the weekend, coming as close as 15km (9 miles) from the surface. Chinese mission control has not confirmed a time for the touchdown attempt, but reports in state-run media suggested it would be early Thursday morning UK time.
Spacecraft have taken pictures of the moon’s far side before, but no lander has ever touched down there. If successful, Chang’e will mark a step towards China’s ambition to become a major power in space exploration alongside the US and Russia.
A major technological hurdle in targeting the side of the moon that constantly faces away from Earth, is that direct communication with the spacecraft is not possible. Instead, messages to and from Chang’e 4 are being relayed by the Queqiao (Magpie Bridge) satellite, which is in a “halo orbit” on the other side of the moon.
The mission is aiming to take detailed measurements of the moon’s terrain and mineral composition. The Aitken basin is thought to have been formed during a gigantic collision very early in the moon’s history. The collision is likely to have thrown up material from the moon’s interior, meaning that Chang’e could provide new clues to how the satellite was formed.
The far side of the moon is also viewed as an attractive site for radio astronomy in the future. A telescope situated there would be shielded from human radio activity, potentially making it more sensitive to radio bursts coming from the sun, or faint signals from deep space. Chang’e 4 is carrying an instrument to assess the “electromagnetic cleanliness” of the location as a first step to scoping out the possibility of placing a telescope there in the future.
“You’re completely shielded from all the emissions that we produce on Earth so you can get data that we couldn’t get elsewhere,” said Prof Lucie Green, a space scientist at University College London. “There’s been a lot of talk over the years of the potential of having a telescope on the far side. This mission could pave the way for more serious development on that side.”
Since the moon’s revolution cycle is the same as its rotation cycle, the same side always faces Earth. The other face, most of which cannot be seen from Earth, is called the far side or “dark side” of the moon, not because it is dark, but because most of it is uncharted.
