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(单词翻译:双击或拖选)
This is Scientific American's 60-second Science. I'm Karen Hopkin.
When it comes to Saturn1, it's the rings that render the planet instantly recognizable. But it turns out that Saturn was not always so elaborately adorned2. Data from the final orbits of the Cassini mission indicate that Saturn's rings were a relatively3 recent addition...forming a scant4 100 to 10 million years ago. The findings are in the journal Science.
During what's been called the "grand finale" phase of the Cassini mission, the spacecraft repeatedly dove through the gap between the top of Saturn's clouds and the innermost edge of its rings. These flybys allowed researchers to separate the gravitational effects of the planet and its accessories...which led to a more precise measurement of the rings' mass.
"Their mass was the missing piece of the puzzle to determine their age."
Daniele Durante, a postdoc at Sapienza University in Italy, who analyzed5 the data.
"The rings are made up mostly of ice with a small fraction of impurities6. About one or two percent of the total rings' mass. These impurities consist of rocky material coming from outer space. Since these impurities are accumulated over time, these allow us to relate the total mass of the rings with their age."
Durante and his colleagues found that Saturn's bling has a combined mass of about one-and-a-half to two times 10 to the 19th kilograms...that's less than half the mass of its smallest moon. And when they crunched7 the numbers, the data suggested an age of no more than 100 million years. To put that in context, remember, dinosaurs8 roamed the earth from about 200 million years ago until 65 million years ago. And Saturn itself, like planet Earth, formed early in the life of the solar system, about 4.5 billion years ago.
"Therefore, the ring's formation came long after that of the planet."
The youthful accoutrement might have come from a captured comet or a pulverized9 moon. But no matter how they were made, the rings really do make Saturn a solar system standout.
Thanks for listening for Scientific American — 60-Second Science. I'm Karen Hopkin.
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1
Saturn
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n.农神,土星 | |
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2
adorned
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[计]被修饰的 | |
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3
relatively
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adv.比较...地,相对地 | |
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4
scant
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adj.不充分的,不足的;v.减缩,限制,忽略 | |
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5
analyzed
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v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析 | |
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6
impurities
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不纯( impurity的名词复数 ); 不洁; 淫秽; 杂质 | |
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7
crunched
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v.嘎吱嘎吱地咬嚼( crunch的过去式和过去分词 );嘎吱作响;(快速大量地)处理信息;数字捣弄 | |
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8
dinosaurs
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n.恐龙( dinosaur的名词复数 );守旧落伍的人,过时落后的东西 | |
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9
pulverized
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adj.[医]雾化的,粉末状的v.将…弄碎( pulverize的过去式和过去分词 );将…弄成粉末或尘埃;摧毁;粉碎 | |
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