China has a space station and, in just a few short years, has landed robots on the moon and Mars. This week the country’s space agency is targeting new, far-flung destinations and setting off for an asteroid that could contain secrets that explain how Earth and the moon formed.

中国早已建成一个空间站，并在短短几年内将机器人送上了月球和火星。本周，中国航天将目光投向了更遥远的新目标——发射探测器前往一颗可能有助于揭开地球与月球形成之谜的小行星。

The country’s Tianwen-2 spacecraft is lifted off aboard a Long March 3B rocket from the Xichang Satellite Launch Center in southwest China on Thursday around 1:31 a.m. local time, according to state media. (it was still Wednesday in New York).

据官方媒体报道，天问二号探测器已于当地时间周四（纽约时间的周三）凌晨1时31分左右，由长征三号乙运载火箭从位于中国西南部的西昌卫星发射中心发射升空。

After about a year, the robotic mission will arrive at 469219 Kamoʻoalewa, a near-Earth asteroid. There, it will perilously try to scoop up some rocky matter, and then swing back around to Earth. A capsule filled with geologic treasure would then plunge toward the planet for retrieval by scientists in late 2027.

约一年后，这个无人探测器将抵达近地小行星469219（又叫震荡天星）。在那里，它将冒险尝试采集岩石物质，随后折返地球。一个装有地质样本的返回舱将冲向地球，预计科学家将在2027年底将其回收。

If Tianwen-2 pulls this off, China will become the third nation — after Japan and the United States — to retrieve pristine material from an asteroid.

若天问二号成功完成任务，中国将成为继日本和美国之后，第三个从小行星获取原始物质的国家。

“All Chinese planetary scientists are now finger-crossed for this historic mission,” said Yuqi Qian, a lunar geologist at the University of Hong Kong.

“中国所有的行星科学家都在忐忑地期待这次历史性任务的成功，”香港大学月球地质学家钱煜奇表示。

The spacecraft also has a secondary target, an unusual comet that it could study as part of an extended mission.

探测器还有一个次要目标——一颗不寻常的彗星，作为扩展任务的一部分，它将对其展开研究。

Visiting these objects will help reveal more about the building blocks of the worlds of the inner solar system. And as asteroids can pose an impact risk to Earth, missions to study the structures and mineral makeups of these objects can aid planning to deflect or vaporize them.

造访这些天体将有助于揭示更多关于太阳系内行星形成的奥秘。鉴于小行星存在撞击地球的风险，研究其结构与矿物组成有助于制定偏转或摧毁它们的计划。

“A sample return mission is a gift that keeps on giving,” said Sara Russell, a planetary scientist at London’s Natural History Museum.

伦敦自然史博物馆的行星科学家萨拉·拉塞尔说：“样本返回任务如同一个不断带来新收获的礼物。”

While fragments of asteroids reach Earth’s surface periodically, they are contaminated and altered when they plummet through the atmosphere. Scientists prefer untouched matter from the source, brought back to study in ultraclean laboratories.

尽管小行星碎片会偶尔坠落到地球表面，但它们在穿过大气层时会遭到污染和改变。科学家更倾向于从源头获取未受干扰的物质，带回超净实验室进行研究。

“Sample return missions allow us to pick apart the physical and chemical properties of a body in a level of detail that’s not possible with remote observations by telescopes and spacecraft,” said Ashley King, a meteoriticist also at the London museum.

“样本返回任务能让我们以前所未有的精度解析天体的物理化学特性，这是望远镜或航天器远程观测无法实现的，”伦敦自然史博物馆陨石学家阿什利·金解释道。

Japan has accomplished this twice, with its Hayabusa spacecraft raiding the asteroids Itokawa in 2005 and Ryugu in 2019. NASA’s sample return mission to the asteroid Bennu, Osiris-Rex, pulled off the same feat in 2020.

日本已两次完成此类任务，它的隼鸟号探测器分别于2005年和2019年从小行星丝川和小行星“龙宫”采集样本。美国国家航空航天局的奥西里斯-Rex探测器也于2020年完成了对小行星贝努的样本采集。

China’s space agency has executed two successful sample return missions to the moon — in 2020 and 2024. But Tianwen-2 (Tianwen is often translated as “Questions to Heaven”) is China’s first foray into asteroid sample return.

中国的航天机构虽已在2020年和2024年两次成功从月球采样返回，但天问二号将是中国首次尝试小行星采样返回。

Kamoʻoalewa, the asteroid it will visit, is somewhat peculiar. As a quasi-satellite earlier known as 2016 HO3, it loops around Earth, but it is not a true moon, because it is gravitationally bound to the sun. Recent telescopic observations, though, suggest it is made of the same volcanic matter found on the moon, implying that it is a piece of the lunar surface shorn off by a meteor impact.

天问二号即将造访的这颗小行星颇为特殊。这颗曾编号2016HO3的准卫星虽绕地运行，但并非真正的地球卫星，因为它受太阳引力主导。它由与月球相同的火山物质构成，这意味着它可能是被陨石撞击后从月球表面剥离的一块碎片。

“Kamoʻoalewa, therefore, potentially holds key information about the formation and evolution of the Earth-moon system,” Dr. King said.

“因此，震荡天星可能掌握着地月系形成和演化的关键信息。”阿什利·金说。

However “its origins remain an open question,” said Benjamin Sharkey, a planetary astronomer at the University of Maryland who made those recent telescopic observations. He said he was excited that Tianwen-2 was going to bring some of the asteroid home for study, which should close the case of Kamoʻoalewa’s origins.

“然而它的起源仍然是一个未解之谜，”马里兰大学的行星天文学家本杰明·沙基说。他表示很期待天问二号能把这颗小行星的样本带回地球进行研究，这应该能解开震荡天星的起源之谜。

China has revealed few details about how Tianwen-2 will work. An academic paper posted last year offers some clues. A variety of cameras and infrared imagers will ascertain Kamoʻoalewa’s shape, size, spin and mineral makeup, while a radar system will map its internal structure.

中国对天问二号如何运转的具体细节披露有限，不过去年发表的一篇学术论文透露了若干关键信息：多光谱相机与红外成像仪将测定震荡天星的形态、尺寸、自转参数及矿物组成，同时搭载的雷达系统将对其内部结构进行测绘。

By looking at the thermal properties of Kamoʻoalewa, Tianwen-2 will also help study the Yarkovsky effect. When sunlight hits a rotating asteroid, its sunward side heats up. As it continues to spin, it cools down, which nudges the asteroid, like a small thruster. Over time, escaping heat can push a harmless asteroid onto an Earth-impacting orbit.

通过观察震荡天星的热特性，天问二号还将帮助研究雅可夫斯基效应。当阳光照射到一颗旋转的小行星时，它向阳的一面会升温。当小行星继续旋转时，它就会冷却下来，从而推动小行星，就像一个小型推进器。随着时间的推移，逸散的热量会将一颗无害的小行星推向撞击地球的轨道。

Kamoʻoalewa can get within nine million miles of Earth, making it an easy target to reach. But diving down to sample it is risky. “The sample collection and return are hardest,” Dr. Russell said, “because humans have only a very limited amount of experience in doing both.”

尽管震荡天星距离地球最近可达1448万公里，是一个容易抵达的目标，但靠近表面采集样本仍有风险。“样本采集和返回是最困难的环节，”拉塞尔说，“因为人类在这两方面的经验非常有限。”

The asteroid may be only 130 feet across — a small target. Its rapid rotation, about once every 28 minutes, poses additional challenges. “You need to find ways to either grab the sample without landing or a way to hang on as it spins,” Dr. King said.

这是颗直径仅40米左右的小行星，目标很小，加上约28分钟一圈的高速自转特性，更是增加了采样难度。“必须研发非接触式采样技术，或实现与其自转同步的锚定系统，”阿什利·金解释道。

China’s spacecraft may try doing both. “Tianwen-2 will use two methods to collect samples from Kamoʻoalewa,” Dr. Qian said.

中国的探测器可能会同时尝试这两种方法。“天问二号将使用两种方法从震荡天星采集样本，”钱煜奇说。

The first is “Touch and Go,” a method employed by the U.S. and Japanese asteroid missions: The spacecraft briefly makes contact with the object, kicks up the surface (using compressed gas, or a fired projectile) and captures jettisoned rocks before the spacecraft flees the scene.

第一种是“触地即走”，这是美国和日本小行星任务即采用该方法：探测器短暂接触天体表面，通过压缩气体或发射弹丸扬起表面物质，捕获飞溅的石块，然后撤离。

The second method, “Anchor and Attach,” has never been tested. Using a series of drills, Tianwen-2 will try to adhere to the asteroid before retrieving both shallow and deeper samples.

第二种方法，即“锚定附着”，这种方法从未进行过实地测试。天问二号将使用一系列钻头固定在小行星上，然后采集浅层和深层样本。

If Tianwen-2 navigates those dangers and eventually drops its bits of Kamoʻoalewa to Earth, it will then fly to the Comet 311P/PanSTARRS, arriving in the early 2030s to study it remotely.

若天问二号成功克服这些风险，最终将震荡天星样本投放回地球，随后将飞往311P/PanSTARRS彗星，预计2030年代初抵达并开展远程研究。

While most comets witnessed from Earth travel on long-haul journeys around the sun, 311P is a main belt comet. These icy curiosities stay within the asteroid belt between Mars and Jupiter.

与大多数需要绕太阳长途跋涉的彗星不同，311P属于主带彗星——这些罕有的冰封天体会停留在火星与木星之间的小行星带。

“These types of objects remain very mysterious,” Dr. Sharkey said, not least because icy rocks should not exist this close to the sun’s warm glow. But they may help explain how Earth became a planet with vast oceans.

“这类天体仍然非常神秘，”沙基说，尤其是因为在靠近太阳温暖光芒的地方，冰质岩石本不应存在。但它们可能有助于解释地球是如何成为一颗拥有浩瀚海洋的行星的。

Tianwen-2 is more than just a scientific sleuth. It is also a technological steppingstone for China’s ambitious Tianwen-3 mission. Due to launch in 2028, it aims to retrieve rock samples from Mars and return them to Earth. A comparable effort led by the United States to achieve the same goal is facing major hurdles.

天问二号不仅仅是一项科学探索。它也是中国雄心勃勃的天问三号任务的技术垫脚石。后者将于2028年发射，目标是从火星采集岩石样本并送回地球。美国为实现相同目标的类似计划正面临重大困难。

But the race for the red planet should not overshadow China’s first bid to acquire shards of an asteroid.

然而，这场火星竞赛不应掩盖中国首次获取小行星样本的里程碑意义。

“This is very exciting,” said Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology. “But asteroids present their own challenges.”

“这非常令人兴奋，”麻省理工学院行星科学家理查德·宾泽尔说，“但小行星探测自有其独特挑战。”