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The astronauts were on a six-month rotation at the space station and had been originally scheduled to return Nov. 5, four days after .

Their return was delayed for more than a week. China's Manned Space Engineering Office said there were minor cracks in a window of the return capsule of the Shenzhou-20 spacecraft, most likely caused by impact from .

There are millions of pieces of mostly tiny debris circling the Earth at speeds faster than a bullet flies. They can come from launches and collisions and pose a risk to satellites, space stations and the astronauts who operate outside them.

The three Chinese astronauts — Chen Dong, Chen Zhongrui and Wang Jie — were coming back on the Shenzhou-21 craft, the Manned Space Engineering office said.

The Shenzhou-20 will remain in orbit, it said. It wasn't clear if the change in spacecraft would affect the timing of future space station missions, which typically take place at six-month intervals. The engineering office said that Shenzhou-22 would be launched but did not specify when.

The returning crew, which had traveled to the Tiangong space station in April, was " , working and living normally,� the same office said earlier this week.

China's space program has since 2003. It has built its own space station and has a goal of landing a person on the moon by 2030.

The latest Shenzhou-21 mission brought four mice to the space station to study how they would be affected by weightlessness and confinement.