Decades ago when Beijing’s top leadership signed off on a plan to catapult China into the club of space superpowers, two goals were set: manned trips and missions such as the recent one that retrieved lunar samples.
The ultimate imperative is to one day pip the US in a new space race.
China accomplished the first feat in October 2003 when People’s Liberation Army Rear Admiral Yang Liwei became the first Chinese in space. Seventeen years later, a probe touched down on a lunar maria and brought rocks and soil 363,000 kilometers back to Earth.
However, amid the hype about the 1.73 kilos of lunar soil stored at the National Astronomical Observatory in Beijing and Mao Zedong’s birthplace of Shaoshan in Hunan province, few are aware that more than a decade of groundwork went into China’s moonshot.
The Chang’e 5’s odyssey could not have succeeded without the down-to-earth studies of lunar soil and a bid to make a mock-up of the landing site.
The Chinese University of Geosicences (CUG), based in Wuhan, was given the job in 2009 of producing mock lunar soil for Chang’e 5’s designers to determine if its robotic arm could reach its design parameters and was tough enough for the perilous trek.
Xiao Long, who works for the university’s Planetary Science Institute, devoted much of his time since then digging through data extracted from NASA’s study of roughly 380 kilos of lunar samples brought back by the manned Apollo program missions.
Xiao, also a core scientist for the Chang’e 5 mission, told Beijing-based Lifeweek magazine that his team had shipped more than 100 tons of pseudo but “very convincing” lunar soil made with Earth ingredients to the Chang’e 5 task force over the years.
“Designers and engineers of the Chang’e 5 probe at China’s National Space Administration (NSA) needed these manmade lunar soil and rocks to simulate sampling and drilling as well as to test the airtightness and structural integrity of containers,” Xiao said.
He added that his lab in Wuhan also drew on years of data from China’s extensive telemetry survey of the lunar surface.
Xiao, however, did not reveal how his team gained access to NASA’s lunar data since the US space agency has since 2011 been banned from comparing notes or collaborating with China on space programs.
The university’s Wuhan Planetary Science Institute did not respond to emailed inquiries about its exchanges with and possible reliance on US researchers.
In early 2020, when Covid-19 brought Wuhan to a halt, all research at the university and Xiao’s institute were paused.
Xiao said at one time he feared, when the development of artificial lunar soil was stuck in the city’s lockdown between February and April, that the Chang’e 5 missions could be grounded for a year or two.
He told Xinhua in a separate interview in November that transport of essential equipment and ingredients had been snarled by the lockdown. He said his team lost no time resuming its work to provide the soil when Wuhan opened up in last April.
In a seminar in December, Hou Jun, chief of the NSA’s lunar program and top commander of the Chang’e 5 mission, revealed a “small incident” during the high-stakes sample collection after the Chinese probe descended on to the lunar surface on December 1.
Hou admitted that the probe’s robotic arm hit a “hard lump of rock” during drilling, and ground control in Beijing decided to end sample collection well ahead of schedule.
Xiao has given a more detailed account of the incident.
During the small hours of December 2, he was also on the deck in the hushed ground control center in Beijing with his eyes riveted on images from cameras on Chang’e 5, when its robotic arm failed to dig deep into the surface.
“We envisaged three scenarios for sample collection: a good one, meaning smooth drilling and collection, and an extreme episode, meaning the arm and driller must break into hard, encrusted layers to penetrate to the intended depth of about two meters. The last scenario was procedures to follow if the entire mission is aborted,” he said.
“Yet right after the arm started digging into the lunar surface after landing, it stopped about 90cm beneath the surface and I immediately realized that it must have hit some hard obstacle.”
He also revealed that another challenge was rocks and pebbles bigger than 1 centimeter in diameter that could clog a key suction pipe.
“We experts at the ground control were split over if the Chang’e 5 should keep digging to get more samples, but we eventually agreed to play safe and stop,” Xiao explained.
“Because the motor driving the robotic arm relied on solar power to operate and may break down in prolonged drilling and that breaking through hard objects may risk losing soil samples already collected and stored in suction tubes inside the arm, so we should take no chances as any reckless move to proceed may forsake all previous efforts.”
The Chang’e 5 samples thus fell short of the 2-kilo goal.
Still, Xiao insisted that the amount of soil collected would be of immense scientific value and may help unravel the lunar origin, because they chose to land the probe on a plain near the Mons Rumker in the Oceanus Procellarum, a vast and uncharted lunar mare on the western edge of the moon’s near side.
“We have now collected the youngest and freshest soil samples, about 1.5-2 billion years old, compared with the average age of at least 3 billion years returned by the Apollo missions. This is because the Chang’e 5’s landing site has a very short geological history, significantly younger than the places visited by American astronauts,” said Xiao, adding that fresher samples could give scientists new perspectives on the formation of the moon and fill a gap in their understanding of the lunar history.
Xiao’s team is now producing more soil as the NSA engineers are working on the designs for the Chang’e 6 and 7 probes. The pair will be primed for the moon’s southern polar region, in missions tentatively set for 2023 and beyond.