Saturn is officially losing its rings — and they’re disappearing much faster than scientists had anticipated
導讀：土星環正在消失，NASA最新數據顯示土星環可能會比之前預測的提前2億年消失。土星環到底是什麼？又是什麼原因導致它的提前消失？
If you were to pick Saturn out of a lineup you』d probably recognize it by its iconic rings. They’re the biggest, brightest rings in our solar system. Extending over 280,000 km from the planet; wide enough to fit 6 Earths in a row. But Saturn won’t always look this way. Because its rings are disappearing.
如果你想從行星群中找出土星，可以通過它周邊那醒目的光環一眼認出它。因為土星環在整個太陽系中最大，也最為明亮，圍繞土星向外蔓延至28萬千米以外，其直徑寬度相當於6個地球並排的直徑總和。可是土星不會一直這樣，因為土星環正在逐漸消失。
That’s right, Saturn is losing its rings! And fast. Much faster, even, than scientists had first thought. Right now, it’s raining 10,000 kilograms of ring rain on Saturn per second. Fast enough to fill an Olympic-sized pool in half an hour.
是的，土星環正在消失！而且速度驚人。甚至比科學家之前預測的速度還要快。就是此時此刻，土星環上的物質也是以每秒1萬公斤重的環雨的形式掉落到土星。打個比方，照這個速度，灑落的環雨可以在半個小時內填滿像奧林匹克廣場那樣大的水池。
This rain is actually the disintegrated remains of Saturn’s rings. Saturn’s rings are mostly made up of chunks of ice and rock,which are under constant bombardment: some by UV radiation from the Sun and others by tiny meteoroids.
這些環雨實際上就是土星環上分離掉落的物質。土星環大部分是由冰塊和石塊組成，這些冰塊、石塊在不斷的撞擊之下開始分崩離析：這些撞擊力有的是太陽的紫外輻射造成的，有的則是來自太空中的小型流星體。
When these collisions take place, the icy particles vaporize, forming charged water molecules that interact with Saturn’s magnetic field; ultimately, falling toward Saturn, where they burn up in the atmosphere.
一旦遭受撞擊，土星環中的冰塊物質就會開始受熱蒸發，形成帶電的水分子，並在土星磁場的影響下，最後以環雨的形式掉落到土星，並在大氣層處摩擦燃燒。
Now, we』ve known about ring rain since the 1980s when NASA’s Voyager mission first noticed mysterious, dark bands that turned out to be ring rain caught in Saturn’s magnetic fields. Back then, researchers estimated the rings would totally drain in 300 million years. But observations by NASA’s former Cassini spacecraft give a darker prognosis. Before its death dive into Saturn in 2017, Cassini managed to get a better look at the amount of ring-dust raining on Saturn’s equator.
上個世紀80年代，美國旅行者計劃首次觀察到這個神秘模糊的環狀物以環雨的形式掉落在土星磁場區，自那時起我們對環雨才有所了解。當時科學研究者們預測土星環的壽命長達3億年之久。然而，美國國家航空航天局之前通過卡西尼號空間探測器對土星進行觀測，其結果顯示並不樂觀。卡西尼號打算在土星環消亡之前對土星赤道地區的大量環雨物質進行進一步研究。
And discovered that it was raining heavier than previously thought. With these clearer observations, scientists calculated the rings had only 100 million years left to live. Now, it’s tough to imagine a ringless Saturn.
卡西尼號也發現掉落的環雨量超乎之前的想像。通過這些愈發明顯的觀測結果，科學家們預測土星環可能只有1億年的壽命。對於現在的我們來說，很難想像土星沒有這些土星環會是什麼樣子。
But for much of its existence, the planet was as naked as Earth. While Saturn first formed around 4.5 BILLION years ago, studies suggest the rings are only 100- 200 million years old,tops. That’s younger than some dinosaurs.
但是縱觀宇宙發展史，土星大部分時候的狀態還是跟地球一樣，身邊空無一物。雖然土星已有約45億年的歷史，但是研究表明這些行星環最多只有1億到2億年左右的壽命。甚至比有些種類的恐龍存在的歷史還要短。
So when you think about it, we’re pretty lucky we happened to be around to see those magnificent rings. Really lucky, in fact. Because efforts to study those rings have led us to other discoveries.
所以這樣一想的話，我們應該為我們現在能夠看到這些神奇美妙的行星環感到慶幸。事實上我們也確實很幸運，因為研究這些行星環還讓我們有了其他的發現。
For example, as Cassini explored Saturn’s moon Enceladus, it uncovered a trail of ice and gas leading back to Saturn’s E ring. Enceladus is the whitest, most reflective moon in our solar system.
比如說，卡西尼號在土衛二上發現了冰和氣體的存在痕跡，這些痕跡延伸至土星環中的E環。土衛二恩賽勒達斯是太陽系中表面最白也是反射性最強的衛星。
And by studying the ring more closely, scientists now know why. Turns out, the moon is constantly gushing out gas and dust.
由於對行星環不斷深入的研究，科學家已經知道了其中奧秘所在。科學解釋就是，土衛二之所有具有這樣的特性是因為上面不斷地噴湧出氣體和微塵等顆粒物。
Some of it ends up in space and in the E ring while the rest snows back onto the moon’s surface, creating a blinding white frost.
這些氣體和固態物質有的散在太空中或是土星E環中，其餘的都像雪一樣覆蓋在衛星的表面，所以使土衛二看起來白得刺眼。
So, who knows what other discoveries might be hiding within the rings? At the very least, it’s clear we』d better keep looking while we still can.
所以，誰知道在這些行星環的背後到底還有多少奧秘等待發現呢？但是，至少有一點我們很清楚，那就是只要土星環存在一天，人類就應該繼續研究關注。
Source: Business Insider
Translation: English Head News from IYUBA