China has postponed a mission to return three astronauts from its space station after a suspected debris strike on a spacecraft, the country’s space authorities said on Wednesday.

中国航天部门周三表示，因航天器疑似受到太空碎片撞击，推迟三名航天员从空间站的返航任务。

The China Manned Space Agency said in a statement that an analysis of the suspected strike and a risk assessment was underway, and that it had decided to delay the return mission for the health and safety of the astronauts.

中国载人航天工程办公室在声明中称，目前对疑似撞击事件正在进行影响分析及风险评估工作，为保障航天员的健康安全，决定推迟返航任务。

The mission, known as Shenzhou-20, was launched on April 24 from the Jiuquan Satellite Launch Center in northern China’s Gobi Desert and is the 35th flight of the country’s manned space program. The astronauts — the mission commander, Chen Dong, and Chen Zhongrui and Wang Jie — have spent six months in orbit at the Tiangong space station. They were expected to return on Thursday to the Dongfeng Landing Site in China’s northern region of Inner Mongolia.

这次任务名为神舟二十号，于4月24日从中国北部戈壁沙漠的酒泉卫星发射中心发射升空，是中国载人航天工程的第35次飞行任务。航天员包括指令长陈冬、航天员陈忠瑞和王杰，已在天宫空间站轨道驻留六个月。他们原计划于周四返回中国北部内蒙古的东风着陆场。

The investigation into the debris strike on Shenzhou-20 will include an assessment of the impact to determine whether it caused any damage to critical parts of the spacecraft’s system, creating a problem for re-entry back to Earth.

针对神舟二十号遭遇碎片撞击的调查将包括撞击影响评估，以确定是否对航天器系统关键部件造成损坏，从而影响返回地球。

Debris in space has become a bigger problem in recent years as more satellites are sent into orbit. Rocket pieces often remain in orbit long after satellites are launched.

随着入轨卫星的数量增多，太空碎片问题近年来日益突出。卫星发射后，火箭残骸往往会长期滞留轨道。

Antisatellite tests have created large volumes of waste, too. Scientists are tracking debris from one Chinese strike in 2007 that destroyed a weather satellite.

反卫星试验同样制造了大量太空垃圾。科学家们仍在追踪2007年中国一次反卫星试验产生的碎片，该试验摧毁了一颗气象卫星。

Scientists and space organizations have done a good job of cataloging larger objects in space, making it easier to avoid collisions, said Christophe Bonnal of the International Academy of Astronautics. But numerous smaller objects, like micrometeroids and debris, float in space, too.

国际宇航科学院的克里斯托夫·邦纳尔表示，科学家和航天机构已对太空中的大型物体进行了妥善分类编目，这让规避碰撞变得更加容易。但太空中还漂浮着大量微小物体，比如微流星体和碎片。

“You don’t see them, and they are deadly,” Mr. Bonnal said.

“这些小物体肉眼不可见，却具有致命杀伤力。”邦纳尔说。

An object as small as 1 millimeter can wreak havoc in space because it will have a similar impact as a bowling ball barreling down at 100 kilometers per hour on earth, Mr. Bonnal said. Some estimates say that there are about 130 million such objects orbiting the earth.

邦纳尔指出，一颗直径仅1毫米的物体在太空中也能造成严重破坏，其撞击力相当于地球上时速100公里飞驰的保龄球。据估计，地球轨道上约有1.3亿个此类微小物体。

The probability of collisions in space has risen in the last decade with the deployment of large satellite constellations such as SpaceX’s Starlink and two Chinese equivalents, Qianfan and Guowang.

过去十年间，随着SpaceX的“星链”，以及中国“千帆”、“国网”等大型卫星星座的部署，太空碰撞的概率有所上升。

“We can see there are more risks,” said Bian Zhigang, vice administrator of China’s National Space Administration.

“我们能看到风险在增加，”中国国家航天局副局长卞志刚表示。

His country is researching “the active removal of space debris on orbit,” Mr. Bian said, speaking at the International Astronautical Congress in Sydney in September.

今年9月，卞志刚在悉尼举行的国际宇航大会上透露，中国正在研究“在轨主动清除太空碎片”技术。

China’s space agency addressed questions about space debris strikes last year, saying at a news conference that in extreme situations, it could launch one of its standby emergency spacecraft to rescue astronauts. In this case, that would mean sending an unmanned spacecraft to the space station for the Shenzhou-20 crew to return home.

中国航天部门去年曾在新闻发布会上回应太空碎片撞击相关问题，表示极端情况下可发射备用应急航天器营救航天员。具体而言，此次可能会向空间站发射无人航天器，接神舟二十号乘组返回地球。

After launching its first satellite in 1970, China fell behind in space exploration for two decades until the 1990s.

中国于1970年发射了第一颗人造卫星，此后二十年间，其太空探索事业落后于世界，直到20世纪90年代才逐步追赶。

Over the past few years, its space program has catapulted from fourth in world rankings behind the United States, Russia and Europe, to a close second behind the U.S. with a large stable of launch vehicles, said Jonathan McDowell, an astronomer and expert on space exploration.

天文学家、太空探索专家乔纳森·麦克道威尔表示，过去几年间，中国航天事业已从世界第四（落后于美国、俄罗斯和欧洲）跃升至紧随美国之后的第二位，拥有了完备的运载火箭体系。

“They have now moved to this era of permanent human occupation,” Mr. McDowell said, referring to the fact that the space station always has a Chinese astronaut. “That is a really impressive achievement from a late starter.”

“中国现已进入人类长期驻留太空的时代。”麦克道威尔说，他指的是中国空间站始终有航天员驻留的现状。“对于后来者而言，这是一项令人印象深刻的成就。”

During their time in space, the Shenzhou-20 crew has made several spacewalks, handled cargo deliveries and conducted scientific experiments, among other tasks.

神舟二十号乘组在轨期间完成了多次出舱活动、货物转运、科学实验等任务。

They were joined last week at the Tiangong station by a relief crew aboard another spacecraft known as the Shenzhou-21. Both spacecraft are now docked at the station.

上周，神舟二十一号乘组已乘坐另一艘航天器抵达天宫空间站执行轮换任务，目前两艘飞船均与空间站对接。