The return of three Chinese astronauts to Earth has been postponed indefinitely after their spacecraft was reportedly hit by a small piece of debris, according to Chinese state media.

The astronauts, who are part of the Shenzhou-20 mission, travelled to the Tiangong space station in April and were scheduled to return on Wednesday following a six-month stay. Their replacements, the Shenzhou-21 crew, had already arrived over the weekend.

“The Shenzhou-20 crewed spacecraft is suspected to have been struck by a small piece of orbital debris, and assessment of the impact and associated risks is currently under way,” the China Manned Space Agency (CMSA) said in a statement.

“To ensure the health and safety of the astronauts and the successful completion of the mission, it has been decided that the originally planned return of Shenzhou-20 on November 5 will be postponed.”

Officials did not specify when the debris incident occurred. Earlier in the week, state media reported that both crews had shared a meal of baked chicken prepared using the station’s first oven, delivered by the Shenzhou-21 team. On Tuesday, videos showed the two teams holding a handover ceremony.

Yu Jun, a science communicator known online as Steed’s Scarf, said that if the spacecraft is deemed unsafe to return, authorities could activate a backup plan.

“Shenzhou-22 and the Long March 2F (launcher) were already on standby. This is our rolling backup mechanism. They are in ‘emergency duty’ mode and ready to bring our astronauts home safely if needed,” Yu told his more than five million followers on Weibo.

China has continued to expand its human spaceflight program, completing 37 flights and six crewed missions so far, with plans to land astronauts on the moon by 2030.

The Shenzhou-20 commander, Chen Dong, holds China’s record for the longest cumulative space time more than 380 days and the highest number of spacewalks, with six.

Chinese astronauts have not joined the International Space Station, a partnership between the US, Russia, Europe, Canada, and Japan, due to a US law preventing NASA from cooperating with China’s space program. Instead, China has said it welcomes international cooperation on its Tiangong space station.

(The Guardian Uk)