China scrapes the surface
China’s expertise in space is going ahead in leaps and bounds.
That is especially true of its lunar program which, with its current mission called Chang’e 6, is likely to achieve another ‘first’ soon, with the return of samples of surface material from the far side of the Moon.
The mission includes instruments from four different international partners: France, Sweden, Italy and Pakistan.
China was the third country to successfully soft-land spacecraft on the Moon, after the USSR in 1966 and the US in 1967.
However, with one exception, all of the lunar landing successes so far, including the more recent ones by India and Japan, have landed on the near side. That exception was Chang’e 4, which touched down on the far side of the Moon in January 2019, but Chang’e 6 goes a major step further than its predecessor two missions earlier, the big difference being its sample return capability.
The ‘far side’ of the Moon is the side that we never see from Earth. You will have noticed that apart from minor variations, the dark patches clearly visible to the unaided eye, called maria (which are plains of lava that entered basins former by impacts) are always in about the same position on the lunar disc as seen from Earth. However, that does not mean that the Moon does not rotate. It does indeed turn on its axis – in the same amount of time that it takes to complete an orbit around Earth.
Because we peer at the Moon from slightly different angles as it moves around us, and because of a slight physical lunar wobble, we see, overall, about 59 per cent of the Moon at one time or another.
The remaining 41 per cent cannot be viewed other than in images taken by spacecraft, the first of which we saw in 1959 when the Soviet craft Luna 3 first showed us that the far side looks very different – there are very few maria, even though these are abundant on the near side. The maria that do exist on the far side are generally much smaller.
Another difference is that there are considerably fewer impact craters on the near side, despite the fact that we can see plenty of them when using even a quite small telescope. Yet another is that the lunar crust is thicker on the far side.
Scientists have long been trying to understand the reason, or reasons, for the differences between the two sides of the Moon.
One possibility for the reason for the crustal differences is that the near side faced the very hot early Earth – hot because of the dramatic collision between the still-forming Earth and a Mars-sized object which is thought to have formed the Moon billions of years ago.
Built like a miniature version of the Apollo lunar module, the upper stage of the Chang’e 6 lander will lift off from the Moon, carrying the precious samples to a service module that will return to Earth.
Finally, the container of samples will be released from the orbiter for its return to Earth’s surface in Outer Mongolia. The arrival of the samples on Earth is expected in late June.
Nothing will provide more information about the far side of the Moon than examining these lunar samples under laboratory conditions on Earth.
It is hoped that about 2kg of material will be available for examination.
I fully expect that with Chang’e 6, China will continue its string of lunar successes. However, will China have people walking on the Moon before the US returns? That’s hard to judge. Several years ago I was of the opinion that China would win this ‘modern’ race, but I now think that there will be bootprints of US landing crews on the Moon in 2026 or 2027 – a few years before Chinese ones. I feel sure, though, that China will get there. Both countries’ projects will be fascinating to follow.