China's Chang'e 5 is bringing back the first moon rocks in 44 years

Chang’e 5 is on the last leg of its mission on the moon. After a visit to the lunar surface lasting less than 48 hours, it is back in orbit around the moon and ready to bring its samples home so that scientists on Earth can analyse them.

The spacecraft consists of an orbiter, re-entry capsule, a lander and ascent stage, and launched on 23 November aboard a Long March 5 rocket. It landed on the moon on 1 December. It is China’s first sample return mission, making the nation only the third – after the US and the Soviet Union – to bring back rocks and dust from the moon. The most recent mission to bring back lunar samples was the Soviet Luna 24 probe in 1976.

Chang’e 5 landed in an unexplored area of the moon called Oceanus Procellarum, or the Ocean of Storms. “It’s a region where there are these really volcanically young landforms, and we currently don’t have samples in the Apollo samples or the Russian samples that have anything like that, so these samples will really enable some new science,” says Kerri Donaldson Hanna at the University of Central Florida.

Most of the areas that have been sampled on the moon are about 3 billion years old or older. Scientists estimate that the rocks in Chang’e 5’s landing area are less than 2 billion years old based on the layering of craters in the area. Once we get the samples back to Earth, we will have a better idea of how old these volcanic rocks are.

That’s crucial because on other worlds, the only way we can tell the age of an area on the surface is by analysing the craters – there is no direct way to confirm those ages. By comparing the age directly measured from the samples to the age inferred from craters on the moon, we can create a link between those methods of analysis that will also be useful on other crater-pocked worlds like Mars and Mercury.

After Chang’e 5 landed, it almost immediately began digging into the lunar surface. It has two mechanisms to get samples both from the surface and underground: a robotic arm with a scoop to collect surface soil, and a drill to collect a core about 2 metres deep.

The sampling had to be done quickly. The spacecraft is solar powered and doesn’t have the heaters it would have needed to survive the frigid lunar night, so sampling had to be finished within a single lunar day at most – about 14 Earth days. After the drilling was done, the samples were loaded into the ascent stage which launched back off the moon to reunite with the orbiter and re-entry capsule.

The re-entry capsule full of samples is expected to land in Inner Mongolia in mid-December. If all goes well, that will be when the work of analysing the new stash of moon rocks begins.

“These samples will not only add to our understanding of the ages of volcanic features, they will also help us understand the origins of the moon, how the moon formed and evolved, and where water on the moon might have come from,” says Jessica Barnes at the University of Arizona. Part of the haul will also be placed in permanent storage at Hunan University in Changsha, China, for future analysis.

Chang’e 5 is part of a series of missions that began with an orbiter that circled the moon from 2007 to 2009.“The Chinese lunar exploration programme has been building up the capability to do science from orbit, and then from the surface, then collect samples and bring them back – that’s a logical progression,” says Barnes. “The next step is to send humans.” China’s space agency has said they expect to send humans to the moon around 2030.

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