The lunar soil samples     1    (bring) back by China’s Chang’e-5 probe (探测器) will go on display for the public in Beijing soon after     2    (they) first showing at the Great Hall of the People.

The Chang’e-5 probe     3    (collect) 1,731 grams of lunar samples, and the return capsule landed in north China on December 17, 2020. Lunar soil is a     4    (combine) of bedrock dust and glassy pieces containing different minerals and other substances, and is a result of meteorite (陨石), space rays and solar wind     5    (hit) the moon over time. The lunar soil looks like concrete, with each piece about 100 micrometers     6     size.

It’s     7    (possible) to grow vegetables in the soil as it is lacking organic nutrients (营养物) and extremely dry. On the contrary, the soil on Earth is composed of minerals, organic materials and water,     8     allow plants and flowers to grow.

For scientific purposes, it is an ideal opportunity for humans     9    (study) the moon—analyzing soil taken directly from the lunar surface in the lab—which is an experience that neither remote sensing     10     meteorite study can provide.

China launched a satellite on Sunday morning to carry out technological tests for space debris (碎片) management, according to China Aerospace Science and Technology Corp, the country's major space contractor.

The State-owned conglomerate(联合大公司) said in a brief news release that the Shijian 21 was lifted into space on a Long March 3B carrier rocket at 9:27 am from the Xichang Satellite Launch Center in southwestern China's Sichuan province, and later entered     1     preset orbit. The launch marked the 393rd flight of a Long March class rocket.

    2     (develop) by the country's Shanghai Academy of Spaceflight Technology, the spacecraft is tasked with demonstrating its ability to alleviate and neutralize space debris, the company said, without giving more details about the mission.

Space debris consists of useless artificial objects, including everything from spent rocket stages     3     old satellites to fragments resulting from disintegration (瓦解), erosion and collisions. Some of that debris     4     collide (碰撞) with operational spacecraft or cause hazards to manned spaceflights.

A 1-centimeter object moving at 17,000 kilometers per hour would deliver as much energy as a hand grenade, and could destroy a spacecraft.

There are more than 100 million pieces of debris smaller than 1 cm in space, altogether     5     (weigh) thousands of metric tons, the administration said.

    6     China started a space debris action plan in 2000, it has so far allocated considerable resources to research the detection, prevention and mitigation of space debris.

The China National Space Administration established its Space Debris Monitoring and Application Center in June 2015,     7     is responsible for tracking waste, analyzing hazards, developing prevention and disposal plans, creating a debris database and communicating with other nations and international organizations.

    8     Tang Jingshi, a research at Nanjing University's School of Astronomy and Space Science in Jiangsu province, about 34,000 pieces of space debris are larger than 10 cm, and nearly 900,000     9     (size) between 1 cm and 10 cm. As many as 120 million pieces     10     (small) than 1 cm orbiting the Earth, he said, noting that even a millimeter - sized piece is powerful enough to disable a satellite.

About half of the debris was created by disintegrated spacecraft, said Liu Jing, a senior researcher at the National Astronomical Observatories and deputy director of the Space Debris Monitoring and Application Center. She added that abandoned mission payloads and used rocket parts are also major sources.