VOA科学技术2024--Scientists: Icy Moon of Saturn Likely Has an Underground Ocean

Scientists: Icy Moon of Saturn¹ Likely Has an Underground Ocean

　　Researchers say new evidence suggests Saturn's icy moon Mimas likely has a large underground ocean.

　　Astronomers³ based their finding on data collected by the American space agency NASA's Cassini spacecraft. Cassini observed Saturn and its more than 140 moons for more than 10 years before ending operations in 2017.

　　The spacecraft's data covered details about the moon's orbit and rotation⁴. Researchers reported the data provided the best evidence yet of a hidden ocean about 20 to 30 kilometers beneath the frozen surface.

　　Mimas is a relatively⁵ small moon, about 400 kilometers wide. Researchers say Mimas lacks formations on its surface found on other moons, which suggest the presence of underground water. These can include a broken surface as well as geyser activity.

　　Scientists said the fact that Mimas did not have unusual surface formations made it an unlikely candidate for an underground ocean.

　　Valery Lainey, of the Paris Observatory⁶, was co-author of a study describing the research in the publication Nature. "Mimas was probably the most unlikely place to look for a global ocean — and liquid water more generally," he said in an email to the Associated Press.

　　Lainey added, "So that looks like a potential(ly) habitable world. But nobody knows how much time is needed for life to arise."

　　The amount of water thought to exist below the surface of Mimas would represent just 1.2 to 1.4 percent of Earth's oceans, Lainey said. That is because of the moon's small size.

　　However, Mimas does have a very large crater⁷ caused by a crash with a space object. For this reason, the appearance of the moon has been compared to the fictional⁸ "Death Star" space station in the popular movie series Star Wars.

　　English astronomer² William Herschel discovered Mimas in 1789. It is named after a giant in Greek mythology⁹.

　　An article appearing with the study in Nature was co-written by Matija Cuk of the SETI Institute research center and Alyssa Rose Rhoden of the Southwest Research Institute. The two were not part of the study. But they wrote that they find the idea that a small, icy moon can contain young oceans "inspiring."

　　The researchers said the underground ocean appears to have formed recently in space terms, possibly between 5 and 15 million years ago. Lainey said the ocean would likely have an overall temperature of around zero degrees Celsius¹⁰. But the temperature at the seafloor might be much warmer.

　　The fact that the water is in contact with the moon's rocky center may create the right complex chemical conditions to support life. But the researchers noted¹¹ that because the ocean is believed to be young, it might not be ideal for life to form there.

　　Scientists have said in the past that another moon of Saturn, Enceladus, might possess the warmth, water and chemical compounds necessary to support life. But because Mimas' ocean is so young, it "might be a challenge for life's development," study co-writer Gabriel Tobie told Reuters. Tobie is a scientist at the French scientific research agency CNRS and The University of Nantes.

　　However, Tobie added, "Nobody knows how long life needs to emerge from a suitable environment. Mimas may offer a unique opportunity to explore the first stage of life's development."

　　Words in This Story

　　rotate – v. to turn in a circular direction

　　mythology –n. old, stories that belong to certain cultures and which appear again and again in writing and art

　　geyser – n. a hole in the ground from which hot water and steam come out

　　habitable – adj. having the ability to support life

　　potential – n. existing in possibility

　　fictional – adj. not existing in real life

　　inspire – v. to make someone feel that they want to do something and can do it

　　challenge – n. something difficult that tests one's ability or determination

　　emerge – v. to appear somewhere

　　opportunity – n. a chance to do something

1 Saturn   

n.农神，土星

参考例句：

• Astronomers used to ask why only Saturn has rings.天文学家们过去一直感到奇怪，为什么只有土星有光环。
• These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们，土星由较轻的物质构成。

2 astronomer   

n.天文学家

参考例句：

• A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
• He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。

3 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

4 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

5 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

6 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。

7 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

8 fictional   

adj.小说的，虚构的

参考例句：

• The names of the shops are entirely fictional.那些商店的名字完全是虚构的。
• The two authors represent the opposite poles of fictional genius.这两位作者代表了天才小说家两个极端。

9 mythology   

n.神话，神话学，神话集

参考例句：

• In Greek mythology,Zeus was the ruler of Gods and men.在希腊神话中，宙斯是众神和人类的统治者。
• He is the hero of Greek mythology.他是希腊民间传说中的英雄。

10 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

11 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。