一一一笨鸟字幕一一一 因为爱好而翻译此字幕
环绕着壮丽的环状行星——土星 ROWE: Orbiting the magnificent ringed planet, Saturn,
运行的是那些非凡的卫星 are a series of extraordinary moons.
兰扎:我们看得越近 LANZA: The closer that we look,
就越能看到它的卫星就像自己的世界一样—— the more that we see its moons are like worlds of their own --
这样的有活力，如此的像地球 so dynamic, so Earth-like.
这些距离太阳近10亿英里的冰冻世界 ROWE: Almost a billion miles from the Sun,
很可能是生命2.0的家园 these icy worlds could be home for Life 2.0.
土星的卫星可能是 The moons of Saturn offer possibly the best
太阳系中发现外星生命的 chance of finding extraterrestrial life
最佳场所 in our solar system.
每完成一项新任务 ROWE: With each new mission, we get closer
我们就离解开土星卫星的奥秘更近一步 to unraveling the mysteries of Saturn's moons.
宇宙是如何运行的 本字幕翻译自Discovery官方指定字幕
第十一季第1集 本字幕翻译自Discovery官方指定字幕
2019年10月 ROWE: October 2019.
天文学家发现了20颗 Astronomers discover 20 new moons
环绕土星运行的新卫星 orbiting the gas giant, Saturn.
这些3英里宽的小天体 These tiny, three-mile-wide objects
使这颗环状行星的卫星数量超过80个 bring the ringed planet's moon count to over 80,
是太阳系中卫星数量最多的行星 the most of any planet in our solar system.
你可能不喜欢偏袒任何行星，但我还是要说—— You hate to play favorites, but I'm gonna say it --
土星是我最喜欢的行星系统 Saturn is my favorite planetary system.
它美得令人难以置信，有着令人难以置信的 It is unbelievably beautiful, with this incredible system of
环和卫星系统 rings and moons,
里面有很多神秘的东西 and there's a lot of mystery kind of all bound up in there.
旅行者号宇宙飞船让我们第一次 ROWE: The Voyager spacecraft gave us our
近距离观察土星和它的光环 first close look at Saturn and its rings.
二十年后，卡西尼号让我们 Two decades later, Cassini got us even closer
更接近土星的许多卫星 to many of Saturn's moons.
普罗米修斯，潘多拉和阿特拉斯 There's Prometheus, Pandora, and Atlas.
这是最大的卫星，土卫六 Its largest moon, Titan, is a moon that's shrouded
是一颗神秘的卫星 in mystery.
那是土卫一（米玛斯），真的很小 There's Mimas, that's fairly small,
土卫三（特提斯）和土卫四（狄俄涅）要大一些 and then Tethys and Dione are a bit larger.
那是一对卫星——杰纳斯和厄庇米修斯—— There are a pair of moons -- Janus and Epimetheus --
在过去可能是一个卫星 that were perhaps one moon in the past.
土卫八（伊阿珀托斯），一半是亮白色 Iapetus, half of it's bright white.
另一半像煤一样暗 The other half of it is sort of as
有点像阴和阳 dark as coal, sort of yin and yang.
土星的每一颗卫星 Each of the moons of Saturn
都有不同寻常的故事 had remarkable stories to tell.
2005年，卡西尼号 ROWE: In 2005, Cassini discovered that
发现一颗卫星的故事特别令人兴奋 one moon's story was particularly exciting.
普莱特:是的，土卫二（恩克拉多斯） PLAIT: Yeah, Enceladus.
土卫二是土星的一颗小卫星 Enceladus is one of Saturn's wee little moons.
它大约有300英里宽——就规模而言 It's about 300 miles across -- for scale,
它大约是科罗拉多州的大小 it's roughly the size of Colorado.
探测器上的摄像机发现了 ROWE: The spacecraft's cameras spot plumes of
以每小时800英里的速度从土卫二喷出的 water vapor shooting out from Enceladus
水蒸气羽状物 at 800 miles an hour.
是黄石公园 Three times as powerful than
所有温泉总和的三倍 all the hot springs in Yellowstone.
间歇泉的发现 RADENBAUGH: The discovery of geysers gushing out of tiny,
完全改变了我们对卫星到底应该是什么样的看法 little Enceladus that should have been cold and dead,
之前我们一直认为土卫二是小小的冰冻的死亡世界 completely changed our view of what that moon exactly was.
杜尔达:它是活的，这个卫星活着 DURDA: It's alive. That moon is alive.
我真的很想站在土卫二的表面 I'd like to be standing there on the surface of Enceladus to
看看这些水蒸气和冰晶 see with the -- this water vapor
它们以超音速的速度 and ice crystals booming out of the surface
从表面喷出 at supersonic speeds.
卡西尼号的传感器探测到 ROWE: Cassini's sensors probe deep beneath
土卫二冰冻表面下的深处 the frozen surface of Enceladus,
有岩石核心的迹象 the frozen surface of Enceladus,
还有其他一些 detecting hints of a rocky core
更值得注意的东西 and something else even more remarkable.
在那层厚厚的冰层下面 Underneath that thick layer of ice,
是液态水海洋 there is liquid water ocean.
克里斯蒂安森:测量结果表明，它是土卫二 CHRISTIANSEN: The measurements suggest his is a huge part of
内部体积的很大一部分 Enceladus's interior volume,
大约6英里深，正因为如此，它使土卫二 about six miles deep, because it was making Enceladus
在轨道上摆动 wobble in its orbit.
想象一下把液体放进一个球里并滚动它 Imagine putting liquid inside a ball and rolling it.
你可以看到 You see the natural wobble of
液体四处晃动时 You see the natural wobble of
球就会自然摆动 the ball as the liquid sloshes around.
外星世界上巨大的液态海洋 ROWE: Giant liquid oceans on an alien world,
开启了令人兴奋的新的可能性 opening up exciting new possibilities.
哪里有水，哪里就可能有生命 Where you find water, you could possibly find life.
如果你在20年前问我太阳系除了地球之外 If you had asked me 20 years ago where there might be life
还有哪些地方可能存在生命 in the solar system besides Earth,
我想土星的卫星是我最不可能 I think Saturn's moons would have been the last place
选择的地方 I would have picked.
但不管怎么说，这颗环绕土星的小冰卫星 But against all odds, it's looking like this tiny icy
虽然距离太阳 moon orbiting Saturn
近10亿英里，但可能是寻找生命的 nearly a billion miles from the Sun may be one of
最佳地点之一 the best places to look for life.
2021年7月 ROWE: July 2021.
一项新的研究重新检查了 A new study reexamines Cassini's plume data
卡西尼号的羽流数据，发现了大量的甲烷 and finds huge quantities of methane.
这么大的数量 This large amount can't be
不能仅仅用地球化学过程来解释 explained by just geochemical processes.
甲烷可能来自于土卫二海洋中 The methane might be from primordial organic matter
原始有机物的分解 breaking down in Enceladus's oceans,
甚至是我们从未见过的过程 or even processes we've never seen before.
但也有可能是 But it could be that
活的微生物帮助产生了甲烷 living microorganisms helped generate the methane,
就像它们在地球上一样 just like they do on Earth.
土卫二可能看起来很像早期的地球 Enceladus might actually look a lot like early Earth in its
在它深深的海洋里，生命可能刚刚开始出现 deepest oceans, when life was first arising,
因为我们知道土卫二上可能发生的 because we know that there are some chemical pathways that are
一些化学反应在地球上也发生过 likely occurring on Enceladus that happened on Earth.
这些化学途径始于 ROWE: These chemical pathways start with
地球上寒冷海底的热液喷口 hot, hydrothermal vents on Earth's
它们向海洋释放重要的 cold sea floor, releasing important life-giving chemicals
生命化学物质 into the oceans.
拥有热液喷口对生命的进化 Having hydrothermal vents are a real
是一个真正的福音 boon to the evolution of life.
普莱特:这些是地壳的裂缝 PLAIT: These are cracks in the Earth's crust, where
热物质可以在那里喷入海洋 hot material can then spew out into the ocean.
拉德博:这是生命形成 RADEBAUGH: And that's the energy
所需要的能量 that life needs to be able to form,
然后是水，所以一切都存在 and then water so everything is present, and things
生物能够抓住所有这些资源和能量 are able to just grab all these resources and energy
然后开始进化 and just start to evolve.
在地球上，热液喷口会产生甲烷 ROWE: On Earth, hydrothermal vents produce methane,
但数量很少 but only in small amounts.
生活在热液喷口周围的 Microbial life
微生物构成了其余部分 living around the vents makes the rest.
也许微生物 Maybe microorganisms do the same
在土卫二的深海底部也有同样的作用 at the bottom of Enceladus's deep oceans.
土卫二上的热液喷口 Hydrothermal vents on Enceladus could offer
为化学反应变成生物化学 the perfect location for chemistry
进而变成生命提供了绝佳的地点 becoming biochemistry becoming life.
热液喷口通常需要 ROWE: Hydrothermal vents normally require
来自热核的热量 heat from a hot core.
那么土卫二内部发生了什么？ So what's going on inside Enceladus?
这是一颗冰冷的卫星，位于寒冷的外太阳系 This is an icy moon out there in the cold outer solar system.
这些热量是从哪里来的？ Where is all this heat coming from?
卡西尼号发现了土卫二表面 ROWE: Cassini spotted Enceladus's plumes
平行的裂缝中喷出的羽状物 shooting out from parallel cracks
这些裂缝被称为虎纹 in the surface, called tiger stripes.
裂缝是间歇泉起源 The cracks are a clue to the origin of the geysers
和能量来源的线索 and the energy that powers them.
我们观察土卫二本身的轨道 We look to the orbit of Enceladus itself.
它并不是在环绕行星的 It's not in a perfectly circular orbit
完美圆形轨道上 around the planet.
它在一个略微椭圆的轨道上 It's on a slightly elliptical orbit, and that means that
这意味着作用在卫星上的潮汐力会随着时间而变化 the tidal forces acting on the moon change over time.
这有点像橡皮球上的力 It's a little bit like the forces on a rubber ball.
当卫星离行星更近的时候，它就会被拉伸 When the moon is closer to the planet, it's stretched out,
当卫星离行星更远的时候 and when the moon is farther from the planet,
它就会放松一点，所以随着时间的推移 it's relaxed back a little bit, so you're gonna squeeze
就会挤压和变形 and deform and squish the body of
而挤压卫星的过程，就会加热它的内部 that moon over time, which is gonna heat its interior.
温暖的岩石核心加热了海洋 ROWE: The warm, rocky core heats up the ocean,
这既为间歇泉提供了动力 which both powers the geysers as they burst
使它们从表面爆发出来 through the surface
也创造了支持生命的条件 and creates conditions that could support life.
杜尔达:我们看到能量源 DURDA: We see the energy source kicking the water
正在把土卫二地下的水踢出来 out of the Enceladus subsurface.
把这种能源和液态水结合起来 You combine that energy source
这就意味着 and liquid water, that harkens to putting
土卫二走上了地球上早期生命 us on the same path that early life
可能走过的同一条道路 may have taken here on the Earth.
如果是这样的话 And if that's the case,
在土星的一颗卫星的表面下 there could be little beasties swimming underneath the surface
可能有小动物在游泳 of one of Saturn's moons.
土星对土卫二的挤压 ROWE: Saturn's squeezing of Enceladus may
可能使其变成了一个生命世界 have transformed it into a living world,
但其他卫星就没有这么幸运了 but other moons weren't as lucky.
他们在激烈的战斗中被撕裂 They've been torn apart in vicious fights
最终死亡 to the death.
环绕土星的卫星种类繁多 ROWE: There are a huge variety of moons orbiting Saturn,
有比水星还大的土卫六 from Titan, a moon larger than the planet Mercury,
也有只有体育场大小的物体 to objects about the size of a sports stadium.
拉德博:一定发生了什么戏剧性的事情 RADEBAUGH: There must be something dramatic that happened
才会这样 to create a system
就在我们眼前创造了一个 that's so complicated and changing
如此复杂和变化的系统 before our very eyes.
为了了解这一显著的大小差异 ROWE: To understand such a marked difference in size,
科学家们在卫星围绕土星的轨道中 scientists look for clues in the moon's orbits around
寻找线索 Saturn itself.
这个系统的大多数卫星都沿同一方向运行 Most of the moons of that system orbit in the same direction.
这显然不是巧合 That's obviously not a coincidence.
这是太阳系形成时 That's motion left over from the formation
遗留下来的运动 of our solar system.
这表明这些卫星与土星 ROWE: This suggests the moons formed around
形成的时间大致相同 the same time as Saturn did.
46亿年前 4.6 billion years ago,
这个无环气体巨星 the ringless gas giant grows from gas,
从原行星盘中的气体、岩石和冰中 rock, and ice in the protoplanetary disk,
生长出来，以及一系列的卫星 along with a family of moons.
这个起源故事适用于大多数土星卫星 This origin story works for most of Saturn's moons,
但不适用于最近发现的 but not for the recently discovered objects orbiting
与土星自转方向相反的天体 in the opposite direction of the planet's rotation.
如果有一个朝另一个方向运行的卫星 If there's a moon orbiting in the other direction,
它就不可能和行星一起形成 it couldn't have formed with the planet.
它一定是从别的地方来的 It must have come from somewhere else.
是土星捕获了这些卫星 ROWE: Saturn captured these moons.
但是从哪里来的？ But from where?
沃尔什:我们认为，在40亿年前 WALSH: We think there was a huge upheaval in the solar system
太阳系发生了一次巨大的剧变 over four billion years ago,
巨行星从最初靠得比较近 where the giant planets
然后开始相互作用 went from a close and compact configuration, started
相互移动 having interactions with each other,
最终进入了它们今天所发现的 moved each other around to end up into the orbits
轨道 that they find today.
在这个过程中，很多较小的天体 During that process, a lot of smaller bodies,
比如来自太阳系远处的 like asteroids from the distant part
那些小行星 of the solar system got scattered
被分散到各个方向 every which direction.
在这个古老的剧变中 ROWE: During this ancient upheaval,
土星抓住了一些分散的物体 Saturn grabs some of the scattered objects.
许多天体聚集在行星周围的区域 Many bodies now crowd the region around the planet,
这意味着碰撞 and that means collisions.
有些是破坏性的 Some are destructive.
其他的则形成新卫星 Others form new moons.
在宇宙“弹球游戏”中 In the cosmic pinball,
一些卫星被抛出星系 some moons are thrown out of the system,
另一些则被土星“吃掉” and others, into Saturn.
只有一颗大卫星在这场大屠杀中幸存下来 Only one large moon survives the carnage.
沃尔什:突然之间 WALSH: And all of a sudden, most of the mass
所有卫星的大部分质量都集中在土卫六上 of all the satellites is in that single moon, Titan.
土卫六可能是由那些与土星同时形成的 ROWE: Titan may have formed from the material in
原行星盘中的物质形成的 the protoplanetary disk at the same time as Saturn,
但随后又大量吸收了后来卫星碰撞产生的 but then gorged on the debris created in the later
那些碎片 lunar collisions.
它收集了土星轨道上96%的物质 It amassed 96 percent of the material orbiting Saturn
并变得非常之大，以至于形成了稠密的大气层 and grew so large that it developed a dense atmosphere.
克里斯蒂安森:当旅行者号拍摄土卫六时 CHRISTIANSEN: When Voyager photographed Titan,
它清楚地显示出土卫六有一层厚厚的大气层 it clearly showed that Titan had a thick atmosphere,
这是多么令人难以置信地兴奋 which was so incredibly exciting,
但它又是非常的密集和不可穿透 but it was so dense and impenetrable,
使得我们不能看透它 that was all we could see.
在旅行者号20年后 ROWE: Two decades after Voyager,
惠更斯号探测器从卡西尼号发射 the Huygens Probe launched from Cassini
穿过土卫六阴暗的大气层深处 and plunged through the murky depths of Titan's atmosphere.
达特内尔:我们拍摄到的 DARTNELL: Our first images of what
第一张土卫六的照片 the Titanic landscape was like
非常地震撼人心 were utterly and truly mind-blowing.
豪威特:照片表明那里有山脉 HOWETT: It showed there were mountains
这些山脉上有某种侵蚀 and there was sort of erosion
看起来像液体 on those mountains that looked like liquid
从山上流下来，并带来了物质 had fallen down the mountains and brought material with it.
那液体一定是从什么地方来的 That liquid must have come from somewhere.
除了下雨 And where else than rain,
土卫六上的天气还能有什么呢？ the weather on Titan?
我们在太阳系中只发现了两个地方 ROWE: We've only found two places in the solar system
有河流和雨水—— with rivers and rain --
地球和土卫六 Earth and Titan.
在这片黑暗之外 Out of this thick gloom,
这是我们见过的与地球最相似的地方 this is the most similar place to Earth we've ever seen.
相似，但不完全相同 ROWE: Similar, but not identical.
填满土卫六湖泊和河流的“雨”不是水 That rain filling lakes and rivers on Titan isn't water.
是液态甲烷 It's liquid methane.
这就像如果地球上的每一口油井 It's like if every oil well, if every gas station on
每一个加油站都开始到处泄漏 Earth started leaking all over the place,
这就是我们在这个世界上看到的 that is what we see on this world.
甲烷在土卫六上是液态的 ROWE: The methane is a liquid on Titan
因为土卫六表面温度是零下290华氏度 （相当于零下179摄氏度） because the surface temperature is 290 degrees below zero,
据我们所知，这对生命来说 which is a big problem for life
是个大问题 as we understand it.
我们不知道有什么生物 We don't know of any organism that can really survive past
能在零下4华氏度下存活 （相当于零下20摄氏度） negative 4 degrees Fahrenheit, and that's just because
因为细胞在这个温度会结冰 cells will tend to freeze there.
豪威特:我们所拥有的细胞 HOWETT: The cells that we have,
它们的组成成分，这些蛋白质和脂肪物质 what they're made up from, these proteins and fatty
会停止工作，一切都会死亡 material, stop working, and everything would die.
这就是发生在地球上的水基细胞上的事情 ROWE: That's what happens to Earth's water-based cells.
但以甲烷为基础的生命能在极寒环境中存活吗？ But could methane-based life survive in extreme cold?
ALMA望远镜在土卫六富含氮和甲烷的大气中 （阿塔卡玛毫米/亚毫米波阵列望远镜） The ALMA telescope spotted a clue in Titan's nitrogen-
发现了线索 and-methane-rich atmosphere.
当阳光照射到土卫六的大气层时 With sunlight hitting the atmosphere of Titan,
甲烷和氮等物质可以分解 things like methane and nitrogen can get broken apart
并重新组合，就像玩乐高积木一样 and reassembled, like playing with LEGO blocks,
然后这些分子重新组合 and then these molecules recombine to
形成新的分子，就像氰化乙烯一样 make new ones, like vinyl cyanide.
美妙的重组 Artist depiction.
在地球上用于制造塑料的氰化乙烯 ROWE: Used on Earth to make plastics, vinyl cyanide can
可以构建长链分子 build long chains of molecules,
这是构建细胞膜所需的类型 the type you need to build cell membranes.
但与地球上的水基细胞不同 But unlike Earth's water-based cells,
极端寒冷不会破坏它们 the extreme cold wouldn't destroy them.
豪威特:它们可以在这样的低温下存活 HOWETT: It could survive at those low temperatures.
所以在土卫六上，这种氰化乙烯 So on Titan, it could be that this vinyl cyanide is able
可能能够形成 to form the membranes
细胞发育所需的膜 that are required for cells to develop,
这是生命发生所必需的 which are required for life to happen.
好消息是 ROWE: And good news --
土卫六上现在有很多这样的东西 there's a lot of this stuff on Titan right now.
仅在一个湖泊中就有多达 There's as much as 10 billion tons of this vinyl cyanide
100亿吨的氰化乙烯 in just one of the lakes.
如果你想用它来制造生物—— If you want to start making creatures out of it --
比如说，巨型乌贼—— say, I don't know, a giant squid --
你喜欢巨型乌贼吗？ do you like giant squids?
我希望如此，因为你可以 I hope so, because you could make billions
用这种氰化乙烯制造出数十亿只巨型鱿鱼 of giant squids out of this vinyl cyanide.
正如我们所知，土星的间歇泉卫星 ROWE: Saturn's geyser moon, Enceladus,
土卫二可能存在生命 could have life as we know it.
土卫六上可能有一些真正的外星生物 Titan might have something truly alien.
与地球相比，这是一个 It is an unrelentingly brutal,
无情、寒冷的地方 cold place compared to Earth.
但对于土卫六上的生命来说，这可能是最理想的 But for Titanic life, it might just be ideal.
库珀:当我们寻找地球以外的生命时 COOPER: As we search for life beyond Earth,
仍然带有我们所知道的生命的偏见 it still comes with a bias of life as we know it.
所以这很好，随着我们 And so it's great, as we continue
继续探索和不断发展我们对生命的定义 to explore and continue to evolve our definitions,
我们可以扩展我们如何寻找生命的途径 we can expand our view of how to search for life.
也许土星系统有两个生命世界 Maybe the Saturn system has two living worlds.
但要想让生命在土卫六表面茁壮成长 ROWE: But for life to thrive on Titan's surface,
就必须在致命粒子风暴中存活下来 it must survive a storm of deadly particles
因为太阳正在以每小时100万英里的速度 racing out of the Sun
不断喷出这些致命粒子 at over a million miles an hour.
太阳除了提供光和热…… ROWE: The sun provides light and warmth...
还有一种非常危险的东西—— and something else, something very dangerous --
太阳风 the solar wind.
这些致命的太阳粒子 These lethal solar particles can strip away
可以剥离行星和卫星上的大气层 atmosphere from planets and moons.
如果没有大气层 Without an atmosphere,
地球将是一片贫瘠的沙漠，对吧？ Earth would be a barren desert, right?
不会有水，因为水会蒸发掉 There wouldn't be any water, it would just all boil away.
当然就不会有生命了 There wouldn't be any life,
幸运的是，地球有一个内置的防御系统 ROWE: Luckily, Earth has a built-in defense system.
萨特:在地球的中心 SUTTER: In the center of our Earth,
我们有一个固体铁核 we have a solid iron core, and surrounding that is liquid iron
周围是不断移动、旋转和对流的液态铁 that is constantly moving and swirling and convecting,
这些复杂的运动 and these complex motions
增强了一个全球范围的磁场 power up a global-scale magnetic field
普拉特:这就像一个对抗太阳风的力 PLAIT: And this acts like a force field
磁场把太阳风推开 against the solar wind, pushes it away,
这样它就不会撞到我们 pushes it around us so it doesn't hit us.
我们认为土星的卫星土卫六 ROWE: We think that Saturn's moon, Titan,
没有熔融的铁芯 has no molten iron core
因此也就没有保护性的磁场 and therefore no protective magnetic field.
所以它只能受太阳风的支配 So it's at the mercy of the solar wind.
这就引出了一个问题 It kind of begs the question, why does Titan
为什么土卫六有这么厚的大气层？ have such a thick, dense atmosphere?
土卫六在没有防护罩的情况下 ROWE: Titan retaining an atmosphere without
是怎么保持大气层的 a protective shield makes no sense.
萨特:土卫六的确没有磁场 SUTTER: Titan doesn't have a magnetic field,
但土星有 but Saturn does.
所以，土卫六的大气层 So maybe there's some sort of interaction between
和土星的巨大磁场之间可能存在某种相互作用 the atmosphere of Titan and Saturn's giant magnetic field.
气态巨行星土星产生的磁场 ROWE: The gas giant Saturn generates a magnetic field
大约是地球磁场的600倍 around 600 times larger than Earth's,
这足以保护土卫六不受太阳风的影响 large enough to shield Titan from the solar wind.
所以土卫六本身是脆弱的 So Titan by itself is vulnerable.
但土星就像母舰 Saturn is like the mother ship.
它有一个巨大的力场 It has this giant force field
可以用来保护土卫六 that it can use to protect Titan.
尽管有土星的拥抱，但土卫六仍然会失去一些大气层 ROWE: Despite Saturn's embrace, Titan still loses
因为偶尔 some of its atmosphere, because occasionally,
卫星会离开它的保护母体 the moon wanders away from its protective parent.
在大部分的运行时间内 Titan orbits inside of that magnetic field...
土卫六的轨道在磁场内部 mostly, most of the time.
但它的轨道不是完美的圆形 Its orbit isn't perfectly circular.
它有点椭圆 It's slightly elliptical.
所以当土卫六围绕行星公转的时候，有一小段时间 So as Titan orbits the planet, for a little bit of time,
大约5%的轨道 about 5 percent of its orbit,
它实际上是稍微在磁场外的 it's actually slightly outside the magnetic field
然后又回到磁场里 before dipping back in again.
但这些短暂的攻击 ROWE: But these short forays into
不会造成任何持久的伤害 the firing line don't cause any lasting damage.
真正奇怪的是土卫六上 What's really weird is that there's sort of a residual
还有残留的磁效应 magnetic effect on Titan.
当它离开土星的保护磁场时 When it leaves Saturn's protective field,
它应该会立即消失 it should just immediately drop to nothing.
但仍然有残留的磁场 But there still is this residual field,
保护它不受太阳风的影响 protecting it from the solar wind.
萨特:它可以保持磁场的记忆 SUTTER: It can maintain the memory of that magnetic field
同时还能保留一些保护 and still preserve some of that protection.
这就像是土星试图教土卫六 It's almost like Saturn is trying to teach
如何拥有磁场 Titan how to have a magnetic field,
土卫六可以记住一点 and Titan can remember for a little bit,
但之后它需要回家 but then it needs to come back home.
这种磁记忆可以帮助土卫六 ROWE: This magnetic memory could help
保护星球表面上的任何生命 support any life on Titan's surface,
为太阳风提供一个安全的避风港 providing a safe haven that's protected from the solar wind.
卡西尼号发现了土星的磁性 And Cassini spots a way
也可能使其卫星 Saturn's magnetism might also allow
发展生命的一种方式 its moons to develop life.
围绕土星最惊人的发现之一是 One of the most amazing discoveries around Saturn was
它的磁场不仅仅是 that its magnetic field is not
改变太阳的带电粒子 just transporting charged particles from,
而且还将物质从一个卫星传输到 say, the sun, but it's also transporting material
另一个卫星 from one moon to another.
土星的磁场从其姐妹卫星土卫二上 ROWE: Saturn's magnetic field helps boost
窃取物质 the chance of life on Titan
从而增加了土卫六上存在生命的可能性 by stealing material from its sister moon, Enceladus.
的确，磁力是一种强大的力量 Magnetism is a strong force, of course,
但在这样的规模和范围内发挥作用 but to act on a scale and a range
将物质从一个卫星运送到另一个卫星 like this and maybe transport matter from moon to moon,
这真的很酷 that's pretty cool.
土星的磁场粉碎了 ROWE: Saturn's magnetic field smashes apart
土卫二间歇泉喷出的水分子 water molecules blasted out from Enceladus's geysers
并将剩余的氧气带到土卫六 and carries the leftover oxygen to Titan.
萨特:土星的磁场 SUTTER: The magnetic field of Saturn
就像土星系统中的一条星间高速公路 acts like an inter-lunar highway
将氧气从土卫二 in the Saturn system, transporting oxygen
一路运送到土卫六 from Enceladus all the way to Titan.
但当磁场试图将氧气从这条星间高速公路 ROWE: But there's a problem when the oxygen tries to
土卫六的出口出移开时，就出现了一个问题 take the Titan exit off of this inter-lunar highway.
正常情况下，这些氧气 Normally, this oxygen wouldn't survive
不会在土卫六的大气中存活 in the atmosphere of Titan.
它会与那里的甲烷反应，产生二氧化碳 It would react with the methane there and create carbon dioxide.
为了完整地到达水面 ROWE: To get to the surface
氧气完整地连接在一起 in one piece, oxygen hitches
氧与一种叫做富勒烯的物质搭在一起 a ride with something called a fullerene.
富勒烯是一种 Fullerenes are these sort of
足球形状的中空分子 soccer ball shaped molecules that are hollow.
如果氧原子进去了 If the oxygen atom gets in there,
它就可以安全地穿过土卫六的大气层 it can be safely transported through Titan's atmosphere.
一旦到达星球表面，氧气可以帮助产生 ROWE: Once on the surface, the oxygen could help create
氨基酸 amino acids,
氨基酸是蛋白质的基本组成部分 the essential building blocks of proteins,
是生命出现的另一块垫脚石 another stepping stone for life to emerge.
想想所有复杂的 Think of all the complex coincidences
巧合的化学反应 that have to happen
都必须要发生 for these chemical reactions to take place.
如果土卫六的轨道有任何不同 If Titan's orbit was any different,
它根本就不存在 it simply wouldn't exist.
土星保护着其卫星上任何潜在的生命 ROWE: Saturn protects any potential life on its moons.
事实证明 And as it turns out, the moons
这些卫星通过创造和维护 return the favor by helping create
土星标志性的光环来回报土星 and maintain Saturn's iconic rings.
直径达17万英里 ROWE: At 170,000 miles in diameter,
但某些地方只有30英尺厚 but only 30 feet thick in places,
土星美丽的光环总是抢尽风头 Saturn's beautiful rings have always stolen the show,
但它们的起源仍然是一个谜 but their origin is still a mystery.
土星有这些美丽的光环 Saturn has these beautiful rings that really
真是这些将它定义为一颗行星 define it as a planet,
但它在太阳系中是独一无二的 but its unique in the solar system in the sense that no
因为没有其他行星有这么大的光环系统 other planet has such a big ring system.
塞勒:所有其他气体巨星都有残留的光环 THALLER: All of the other gas giants have remnants of a ring,
但那是又小又薄又暗的光环，与土星不同 kind of small, thin, dark rings, but nothing like Saturn.
所以土星周围发生了非常不同的事情 So something very different happened around Saturn.
线索来自光环的组成 ROWE: A clue comes from the rings' composition.
它们大约99%是水冰 They're around 99 percent water ice,
这让光环看起来闪闪发光 giving the rings their sparkling appearance.
这让天文学家提出了一个大胆的理论 This leads astronomers to a bold theory.
我们不知道土星的冰环是如何形成的 We do not know how Saturn's icy rings formed.
我们甚至不确定它们的年龄 We're not even sure how old they are,
但有一种想法是，它们是由 but one idea is that they formed from ice that was
以前存在于卫星上的冰形成的 existing previously on a moon.
这太神奇了 How amazing is that?
几十亿年前，土星可能是没有光环的 ROWE: Several billion years ago, Saturn may have been ringless,
只有一颗巨大的冰质卫星 with a large, icy moon.
卫星足够大，它的引力将岩石等较重的物质 The moon was big enough that its gravity drew heavier
吸引到它的核心 stuff like rock to its core
而冰等较轻的物质则漂浮到顶部 and lighter stuff like ice floated to the top.
我们认为卫星离土星太近了 ROWE: We think the moon strayed too close to Saturn.
沃尔什:来自土星的引力会把它撕裂 WALSH: The gravity from Saturn could tear it apart,
它会把冰从岩石部分分离出来 and it could separate the ices from the rocky parts
冰会留在轨道上形成土星环 and the ices could stay in orbit and form our rings,
岩石部分会被土星吞噬 and the rocky parts would get swallowed up by Saturn.
一颗大卫星的消亡可能形成了土星环 The death of a large moon may have built the rings,
但它们现在的样子要归功于 but they owe their current appearance to the moons that
那些仍然活着的卫星 are still alive.
塞勒:当你一次又一次地 THALLER: When you go back to Saturn's rings,
回顾土星环时,它们都略有不同 time and time again, they're all slightly different.
它们在变化，彼此交织在一起—— They are changing, they are braiding in and out of
我们不知道光环 each other -- we had no idea there would be
会有如此的美丽和如此的神秘 so much beauty and so much mystery in the rings.
土星的两颗卫星 ROWE: The behavior of two of Saturn's moons,
普罗米修斯和阿特拉斯 Prometheus and Atlas,
镶嵌在土星环中 which are embedded in the rings
它们的行为尤其令人惊讶 is especially surprising.
这些最小的卫星中有一些 Some of these smallest moons
散布在光环系统中 are interspersed within the ring system.
他们中的一些正在做一些非常奇怪的事情 Some of them are doing something really bizarre.
在某些情况下，这些卫星看起来像是在守护着 In some cases, it looks like the moons were shepherding
光环的边缘，并让它们保持在自己的位置上 the edges of the rings and keeping them in their place.
卫星的引力会清理这些环 ROWE: The moon's gravity cleans up the rings,
有时会在它们的尾迹上雕刻出形状 sometimes, sculpting shapes in their wake.
土星环不是静止的，有一些非常迷人的 Saturn's rings aren't static, and there's some really
相互作用，卫星显然在推动土星环 fascinating interactions where moons are clearly pushing on
并产生奇怪但又很酷的波浪 the rings and causing weird and cool waves,
使土星环更加美丽 making the rings just that much more beautiful.
豪威特:土星和它的卫星、土星环之间的 HOWETT: The whole dance between Saturn and its moons,
整个“舞蹈” its rings, how they all
以及它们是如何相互联系的，完全令人着迷 are interconnected, is just completely fascinating.
这是一个充满活力 It's a dynamic, amazing,
令人惊叹、生机勃勃的地方 living, geologically vibrant place.
土星的卫星也许能让土星环保持有序 ROWE: Saturn's moons may keep the rings orderly,
但它们无法解释为什么土星环如此干净 but they can't explain why the rings are so clean,
几乎是原始的 almost pristine.
普拉特:他们太亮了 PLAIT: They're too shiny.
如果它们有数十亿年的历史 If they were billions of years old,
那么它们现在应该聚集了大量的灰尘 they should have collected a lot of dust by now
颜色也会深得多 and be a lot darker.
它们闪闪发光的事实暗示着 The fact that they're shiny kind of implies that
它们可能比我们最初想象的要年轻得多 maybe they're a lot younger than we first thought.
也许我们今天看到的这些光环 ROWE: Perhaps the rings we see today
是最近才生成的 are a more recent upgrade.
这些环可能只有1亿年的历史 The rings might only be 100 million years old,
大约是恐龙的时代生成的 about the time of the dinosaurs.
所以如果恐龙发明了望远镜 So if the dinosaurs had invented telescopes,
他们就能看到没有光环的土星 they could have seen Saturn without rings.
这不由得让人猜想 And it makes you wonder, is this
这是土星的第一个环系吗？ the first ring system that Saturn had?
或者还有另一个 Or was there another ring system
可能被慢慢侵蚀的环系？ that may be slowly eroded away?
也许是一颗彗星或一颗天体离土星太近了 Perhaps a comet or a body came in too close to Saturn,
土星的引力真的把它撕裂了 and Saturn's gravity literally tore it apart,
然后我们得到了一个全新的环系统 and then we got a brand-new ring system.
后来的恐龙可能目睹了环的形成 The later dinosaurs could have watched the rings form,
然后它们就被小行星消灭了 and then they would have been wiped out by an asteroid.
是的，应该造更好的望远镜 Yeah, should have built better telescopes,
恐龙，你真差劲 dinosaurs, sucks to be you.
我们仍然不知道为什么土星环 ROWE: We still don't know why the rings of Saturn
如此干净 are so clean.
有可能这些环真的很古老 It could be that the rings really are old, and they have
它们有某种清洁系统 some sort of cleaning system,
可以清除上面的灰尘 which removes the dust from them,
让它们看起来很年轻,或者它们实际上很年轻 making them look young, or they may actually be young, and this
这可能是第七代，第八代或任何一代的环 may be the seventh or eighth or whatever generation rings.
它与其他行星系统截然不同 It is so different than any other planetary system.
这些谜团仍然存在 And those mysteries still exist.
我们知道发生了什么 We have some idea what went on,
但关于土星还有很多我们不知道的 but there's a lot that we don't know about Saturn.
卡西尼号正在改变这一点 ROWE: Cassini is changing that.
它发现了一个全新的卫星形成过程 It's discovered a whole new moon-making process,
以土星环为主导 with the rings taking the lead.
卡西尼号在执行为期13年的土星任务的中途 ROWE: Midway through its 13-year mission to Saturn,
捕捉到了一张有趣的图像 Cassini captures an intriguing image,
这是土星最外层环边缘的 a bright feature at the edge
一个明亮特征 of one of Saturn's outermost rings,
这是我们以前从未见过的 something we'd never seen before.
当我们看到土星环的图片时，我真的很兴奋 I was really excited when we saw these images of Saturn's
它看起来像一个肿块 rings, and it looked like there was a lump,
可能是一个卫星在那里形成，他们给它起了个绰号佩吉 maybe a moon forming there, which they nicknamed Peggy.
佩吉是以发现它的 ROWE: Named after the mother-in-law
科学家的岳母命名的 of the scientist who discovered it,
它还太小不能被认为是一颗 Peggy was still too small to be considered
完整的卫星，但附近 a fully-formed moon, but nearby orbits
有一群物体的轨道恰好足够大，可以成为卫星 a group of objects that are just big enough to be moons,
它们真的很奇怪 and they are really weird.
这些卫星真的很不寻常 These moons are really unusual.
我们认为它们和我们见过的任何东西都不一样 We don't think of them as like anything else we've seen.
它们是一种毛茸茸的小土豆 They're kind of little fuzzy potatoes or maybe
甚至可能像馄饨或牛角包 even like a ravioli is another one or a croissant.
为什么我们总是想到食物？ Why do we always come up with food?
但与此同时，这正是它们的样子 But at the same time, that's exactly what they look like.
土星上形状最奇特的卫星是土卫四 The most bizarrely-shaped moon of Saturn is Pan.
它有纵横交错的裂缝 It's got these crisscrossing cracks,
就像面包一样，外面是一条 just like bread, and then around the outside
起伏的腹带 is a belly band, it's undulatory.
怎么会变成那样的呢？ How would this get there?
卡西尼号发现了一条线索 ROWE: Cassini discovered a clue.
就像土星环一样 Like Saturn's rings,
这些卫星几乎完全由水冰构成 these moons were made almost entirely of water ice.
它们一定是从 They must have grown from
环内的小块状物质中生长出来的 tiny lumps trapped within the rings.
普莱特:它们将会非常脆弱 PLAIT: They're going to be extremely fragile,
有点像围绕土星运行的雪花 kind of like a snowflake orbiting Saturn.
它们可以开始吸收物质，然后生长 They can start drawing in material and then can grow.
可以想象卷起一个雪球 You can actually imagine rolling up a snowball
在外面积累越来越多的颗粒 and accumulating more and more particles on the outside.
用同样的方法 And in the same way, you could accumulate
可以在环中积累这些团块 these clumps in the rings.
如果它们靠近土星环的边缘 And if they're near the edge of the rings,
也许它们会挣脱束缚，向外形成小卫星 perhaps they actually break free and go out to form tiny moons.
这些太空雪球的大小 ROWE: The size of these space snowballs,
只有直径几十英里或更小 tens of miles across or less,
这有助于解释它们不同寻常的形状 helps explain their unusual shapes.
卫星的大小实际上会影响它的形状 The size of the moon actually affects its shape in that once
一旦低于一定的大小阈值 you get below a certain size threshold,
就不再是圆的了 you cannot be round anymore.
这是因为岩石或冰的强度太大 That's because the strength of the rock or the ice
引力无法克服 in this case is too great to be overcome by gravity,
所以这种不规则的形状可以保持下去 and so the kind of oblong shapes can be maintained.
再加上几次碰撞 ROWE: Add in a few collisions,
就会形成土星的“饺子”和“羊角面包”形状的卫星 and you get Saturn's ravioli- and croissant-shaped moons.
这是一个奇怪的过程，但却形成了一个美丽的形式 It's a bizarre process but leads to a beautiful form.
我们知道卫星会影响环 We know the moons affect the rings, but it looks
但在这种情况下，环似乎也会影响卫星 like in this case, the rings affect the moons, too.
它们是双向互相影响的 They're connected in both directions.
这些环形成了一个卫星工厂 ROWE: The rings form a moon factory,
能够建造无数代的新世界 capable of building countless generations of new worlds.
这是物理之舞 This is a dance of physics.
普莱特:如果这些冰环粒子可以形成小卫星 PLAIT: If moonlets can form by these icy ring particles,
它们就会生长，然后它们与环的自然引力 they'll grow, and then their natural gravitational
相互作用将使它们移动出去 interaction with the rings will make them move out.
他们不断向外扩张 They keep growing as they move out.
但随后，另一颗卫星在第一个卫星所在的位置形成 But then another moon forms where the first one was.
所以就会不断得到这些不断增长的卫星，对吧 So you keep getting these growing moons, right,
这个过程就像传送带一样重复 and this process repeats like on a conveyor belt.
结果是更大的卫星在离土星更远轨道上运行 And what you wind up with is bigger moons orbiting
而更小的卫星在离土星更近的 farther out from Saturn and smaller ones
轨道上运行 orbiting closer in.
但土星的传送带最终会坏掉 ROWE: But Saturn's conveyor belt will eventually break down.
当来自太阳的紫外线 When ultraviolet light from
与土星环的粒子相互作用时 the sun interacts with ring particles,
它们围绕土星的稳定轨道就会紊乱 it throws their steady orbit around Saturn out of whack.
太阳为土星环提供能量，并给它们“充电” The sun energizes the rings, and it gives them a charge.
这种电荷意味着 This charge means they can get picked
它们可以被土星的磁场带走 up by the magnetic field of Saturn.
所以这些微小的带电粒子 So these little tiny charged particles then are lifted
会被带离土星环 out of the rings,
沿着磁场线，像雨点一样 follow along the magnetic field lines,
落进土星的大气层 rain down into Saturn's atmosphere.
带电粒子是微小的冰晶 ROWE: The charged particles are tiny ice crystals.
它们落在土星上 They rain down onto Saturn,
每一秒都足以填满一个奥运会规模的 enough to fill an Olympic-sized swimming pool
游泳池 every second.
不到1亿年 In less than 100 million years,
土星环就会消失 Saturn's rings will be gone.
届时将没有物质来建造新卫星 There will be no material to build new moons.
土星的卫星和土星环 Saturn's moons and rings,
它们几乎让我感到苦乐参半 they almost make me feel bittersweet, because they
因为它们向你展示了物理学所能创造的美丽 show you the beauty of what physics can create,
但也有转瞬即逝的感觉 But also the fleeting-ness.
它们很快就要消失了，这让我很难过 They'll be gone soon, and that makes me sad.
我们看得越近 ROWE: The closer we look,
土星系统就变得越有趣 the more intriguing the Saturn system becomes.
现在，科学家们 And now, scientists
有了一个大胆的新计划 have an audacious new plan
让无人机在土星的一颗卫星上飞行 to fly a drone on one of Saturn's moons.
土星是太阳系中最有活力的 Saturn is one of the most dynamic places
地方之一 in the solar system.
我们想回到那里 We want to go back there,
近距离探索它的卫星 to explore its moons up close
直接寻找生命2.0 and hunt directly for Life 2.0.
一直以来，我们都在强调如果有 For so long, we've been emphasizing that to have
一颗适宜居住的行星 a habitable planet,
那必须是温暖的，必须离母恒星很近 you have to be warm, you have to be close to your star.
事实上，我们发现最有可能有生命机会的 In fact, the most likely chance we have to find
可能是在太阳系外的土星卫星上 life maybe way in the outer solar system in Saturn's moons.
但我们不能确定，除非我们 But we won't know for sure until we send
再向那里发射另一个探测器，专门寻找生命 another mission there, specifically to look for life.
惠更斯探测器让我们看到了 ROWE: The Huygens Probe gave us
土卫六表面的诱人景象 a tantalizing glimpse of Titan's surface,
但它不具备寻找生命的条件 but it wasn't equipped to search for life.
现在，科学家们正在开发一种 Now, scientists are developing Dragonfly,
可以搜索生命的太空直升机“蜻蜓” a space helicopter that can search for life.
蜻蜓是一个了不起的任务 Dragonfly is an amazing mission.
我们将它发送到土卫六 We're sending this to Titan to better
可以更好地了解生命是如何在与地球截然不同的环境中 understand how life might arise in a very different
产生的 context than Earth.
有一件事是我们完全可以肯定的 One thing we know absolutely for certain
那就是土卫六的化学成分有趣而复杂 is that Titan has interesting, complex chemistry.
现在的问题是 The question now is,
这种化学反应真的会转化为生物化学吗？ does that chemistry actually turn into biology?
最重要的问题是，这是一个有生命的世界吗？ The million-dollar question, is this a living world?
2021年4月 ROWE: April 2021.
我们测试太空直升机的概念 We test the concept of a space helicopter.
首次在另一个世界进行远程飞行的 Ingenuity making the first remote flight on
“独创性”飞船进入了稀薄的火星大气层 another world launches into the thin Martian atmosphere.
火星是一个非常难飞行的地方 Mars is a really difficult place to fly,
因为它的大气层比地球薄100倍 because the atmosphere is 100 times thinner than Earth's.
要知道，是大气层为直升机的飞行 And remember, it's the atmosphere that provides
提供了支撑和升力 the support and the lift for a helicopter to fly.
所以为了让“匠心”飞起来 So in order for Ingenuity to fly,
它必须旋转得非常快 it had to spin very fast in order
才能离开地面 to even get itself off the ground.
幸运的是，土卫六厚厚的大气层 ROWE: Fortunately, Titan's thick atmosphere
对直升机更有利 is much more helicopter friendly.
“匠心”和“蜻蜓”任务之间的对比 The contrast between Ingenuity and the Dragonfly mission
真的很有趣 is really funny,
因为火星几乎没有大气层 because Mars has almost no atmosphere,
气压不到地球的1% less than 1 percent the atmospheric pressure of Earth.
在土卫六上，情况正好相反 On Titan, you have exactly the opposite.
土卫六表面附近的气压 The air pressure near the surface of Titan can be
是地球上气压的四倍 four times as much as the air pressure on Earth.
所以对于直升机或者像无人机这样的东西 So for a helicopter or something like a drone,
比如八翼直升机这样的东西 something like an octocopter,
重力越低，大气密度越大 the lower the gravity is and the denser the atmosphere,
就会飞得越好 the better you can fly.
兰扎:所以土卫六需要被探索 LANZA: So Titan just begs to be explored, because you get
因为有很大的升力，而且还可以随身携带 a lot of lift, and you can actually carry heavy
沉重的仪器 instruments with you.
它可以让你飞越大气层 It allows you to fly through the atmosphere,
收集样本，并确定那颗卫星上生命起源的 collect samples, and determine what the prebiotic chemistry
化学成分 is on that moon.
如果说有一个世界是为无人机建造的 If ever there was a world built for flying drones,
那就是土卫六 it's Titan.
蜻蜓号计划于2027年发射 ROWE: Dragonfly is scheduled to launch in 2027,
大约7年后抵达土卫六 arriving at Titan around seven years later,
完成由旅行者号和卡西尼号开始的 completing the journey of moon discovery that began
卫星发现之旅 with Voyager and Cassini.
杜尔达:我们完全改变了 DURDA: We completely transformed
我们对土星系统、土星环和土星卫星的认识 our picture of the Saturn system, the rings and the moons.
这里的环境 It's a far more complex
比我们想象的要复杂得多 environment than we ever dreamed possible.
卫星活了，是吧？ The moons have come alive, right?
它们不是无聊的死冰球，只是需要 They're not boring, dead ice balls, and it just
一代又一代的宇宙飞船跟进 begs generation after generation of spacecraft follow up.
我们才刚刚开始揭开 ROWE: We're only just beginning to
土星卫星的秘密 unravel the secrets of Saturn's moons.
有超过80颗卫星有待探索，土星系统 And with more than 80 to explore, the Saturn system is
是一份礼物，我们将继续探索 a gift that'll keep on giving.
土星是我小时候 Saturn was the very first thing I ever
用望远镜看到的第一个东西 saw through a telescope when I was a kid.
我在这里，很明显，我是受到土星的启发 And here I am -- clearly, I was inspired by Saturn,
被它的美丽所吸引 by its beauty.
塞勒:土星一直是我最喜欢的行星 THALLER: Saturn has always been my favorite planet.
你想要的一切都在那里—— Everything you want
暴力，碰撞的卫星 is there -- violence, colliding moons,
新环的形成，随着时间的推移，新卫星的形成 how new rings form, new moons form over time.
普莱特:那里可能有生命 PLAIT: And there might be life there.
那里可能不止一个地方有生命 There might be life in more than one place there.
一个目的地，一个星球的邮政编码，会给你所有想要的 One destination, one planetary zip code, gives you all of that.
我建议你回土星去 I say go back to Saturn.