China: Chang'e 5's space probe collects moon samples

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The Chang’e 5 mission in 2020 marked China’s fifth-ever venture to the Moon but, more importantly, it was the country’s first sample-return mission. The Chinese spacecraft landed on the Moon on December 1, targetting a region previously unexplored by US astronauts or Soviet probes. This was the first sample-return mission since the Soviet Union’s Luna 24 in 1976 and made China only the third country to collect samples from the Moon when Chang’e 5 landed back on Earth on December 16.

Hailed a great victory for the Chinese space programme, the mission has provided fascinating new insight into the Moon’s history.

The rock and dust collected in the Moon’s Oceanus Procellarum region (Ocean of Storms), appear to be much younger than previously collected samples.

The site was specifically chosen for Chang’e 5’s landing because its creates suggested it was younger than the areas surveyed by the Apollo and Luna missions.

In total, the Chang’e 5 spacecraft returned to Earth about 3.81 pounds (1.73 kilograms) of lunar rock and dust.

Subsequent analysis of the lunar material has confirmed that volcanism on the Moon occurred much later than previously thought, and that has proven to be something of a scientific conundrum.

According to a report in Space.com, scientists first dated a fragment of the lunar rock samples to about 1.97 billion years ago.

This was done in October last year by researchers at the Washington University in St Louis.

At the time, Professor Brad Jolliff, director of the university’s McDonnell Center for the Space Sciences, called it a “perfect sample to close a two billion-year gap”.

Up until that point, all rock samples collected by the Apollo missions between 1969 and 1972, were found to be older than three billion years old.

China launches Chang'e-5 lunar probe with Long March-5 rocket

Prof Jolliff said: “And all of the young impact craters whose ages have been determined from the analysis of samples are younger than 1 billion years.

“So the Chang’e-5 samples fill a critical gap.”

A new study published in the journal Nature has now used a similar dating method on a different lunar sample and has found the lunar rocks to be about 2.03 billion years old.

Both studies seemingly confirm volcanic activity in this particular part of the Moon about a billion years after the regions surveyed by NASA and the Soviet Union were already geologically dead.

The findings have shed new light on the layer of rock directly below the Moon’s crust.

James Head III, a professor of geological sciences at Brown University and a co-author on the first paper, told Space.com: “This means that the mantle had sufficient internal deep mantle heat two billion years ago to continue to melt mantle material and produce extrusive mare basalts.”

However, scientists have so far been unable to figure out why this part of the Moon remained active so late in the Moon’s history.

Joshua Snape, a planetary scientist at the University of Manchester, said: “The jury is still out on how and why the late-stage volcanism occurred.”

According to one theory, this part of the Moon might have been abundant in KREEP – heat-producing elements potassium (K), rare Earth elements and phosphorus.

But an analysis of the Chang’e 5 samples has failed to find significant levels of KREEP in the lunar rocks.

Dr Snape said: “Perhaps we need to consider whether tidal heating, caused by the stretching and squeezing by gravitational interactions between the Earth, Moon and Sun, could be a larger factor than anticipated.”

According to NASA, the Moon formed when a Mars-sized body slammed into the Earth.

The resulting debris that was cast into space eventually coalesced into a single satellite about 239,000 miles from Earth’s surface.

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