VOA科学技术2024--NASA Spacecraft Unlocks Asteroid Dinkinesh's History

NASA's Lucy spacecraft visited a little asteroid¹ called Dinkinesh last November. The visit, scientists say, unlocks a surprisingly interesting history of the asteroid along with its companion, Selam.

Asteroids² are ancient objects from the beginning of the solar system. They offer clues about how Earth and other planets formed about 4.5 billion years ago.

The U.S. space agency launched Lucy in 2021 on a 12-year mission to study asteroids. The mission is especially interested in Jupiter's Trojan asteroids, two groups of space rocks that lead and follow the giant planet as it orbits the sun.

On the way, Lucy flew past Dinkinesh and Selam in the inner edge of the main asteroid belt. The spacecraft observed ridges⁴, trough structures and other features on Dinkinesh.

Dinkinesh has a diameter of nearly 720 meters. Selam is made up of two similarly sized lobes⁶, one about 230 meters wide and the other about 210 meters. Selam orbits Dinkinesh once about every 53 hours at a distance of about 3.1 kilometers.

It appears, the researchers said, that a big piece of rock broke free sometime in the past from Dinkinesh. The rock was about a quarter its total size, creating a trough on its surface and sending debris⁷ into space. Some of this debris, they said, fell back onto Dinkinesh's surface to form a ridge³ structure.

Other materials came together to form Selam, becoming what is called a contact-binary moonlet.

Katherine Kretke, from the Southwest Research Institute in Colorado, is a co-writer of the study published in Nature. She said that "a contact-binary is when it appears that a single body is composed of two objects that collided gently enough not to become disrupted."

Kretke said they are common in the solar system, but Selam was "the first time a contact-binary has been observed orbiting another asteroid."

Simone Marchi is another co-writer of the study. He said, "A planet like Earth formed by the accumulation of countless⁸ small bodies. Understanding the properties of small asteroids such as Dinkinesh and Selam helps us to have a better picture of the earliest phases of planet formation."

NASA's spacecraft was named for the Ethiopian fossil of the extinct human relative Australopithecus called "Lucy." That fossil has provided information about early human beings, much like asteroids provide knowledge of planetary formation.

Dinkinesh is the Ethiopian name for the Lucy fossil, meaning "you are marvelous" in the Amharic language. Selam, the Ethiopian name for another Australopithecus fossil, means "peace" in Amharic.

Lucy will next visit the asteroid Donaldjohanson in 2025 in the main asteroid belt. The spacecraft is expected to visit 11 asteroids in total.

Words in This Story

belt - n. a band of material that is worn around a person's waist

ridge - n. a long area of land that is on top of a mountain or hill

trough - n. a long, low area between waves or hills

lobe⁵ - n. a curved or rounded part of something

debris - n. the pieces that are left after something has been destroyed

collide - v. to hit something or each other with strong force

accumulate - v. to gather or acquire gradually as time passes

fossil - n. something that is from a plant or animal which lived in ancient times and that you can see in some rocks

marvelous - adj. extremely good or enjoyable

1 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

2 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

3 ridge   

n.山脊；鼻梁；分水岭

参考例句：

• We clambered up the hillside to the ridge above.我们沿着山坡费力地爬上了山脊。
• The infantry were advancing to attack the ridge.步兵部队正在向前挺进攻打山脊。

4 ridges   

n.脊( ridge的名词复数 )；山脊；脊状突起；大气层的)高压脊

参考例句：

• The path winds along mountain ridges. 峰回路转。
• Perhaps that was the deepest truth in Ridges's nature. 在里奇斯的思想上，这大概可以算是天经地义第一条了。

5 lobe   

n.耳垂，（肺，肝等的）叶

参考例句：

• Tiny electrical sensors are placed on your scalp and on each ear lobe.小电器传感器放置在您的头皮和对每个耳垂。
• The frontal lobe of the brain is responsible for controlling movement.大脑前叶的功能是控制行动。

6 lobes   

n.耳垂( lobe的名词复数 )；（器官的）叶；肺叶；脑叶

参考例句：

• The rotor has recesses in its three faces between the lobes. 转子在其凸角之间的三个面上有凹槽。 来自辞典例句
• The chalazal parts of the endosperm containing free nuclei forms several lobes. 包含游离核的合点端胚乳部分形成几个裂片。 来自辞典例句

7 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

8 countless   

adj.无数的，多得不计其数的

参考例句：

• In the war countless innocent people lost their lives.在这场战争中无数无辜的人丧失了性命。
• I've told you countless times.我已经告诉你无数遍了。