Water feels good when we're thirsty, cools us when we're hot, looks great in a pond, a lake, a cloud. Because we ourselves are two-thirds water, we like the stuff, we're drawn to it. We search the universe looking for signs of water and when we look back at our planet, we are small and pale, yes, but we're dazzlingly blue.
當(dāng)我們口渴的時(shí)候，水就如甘露一樣。當(dāng)我們炎熱的時(shí)候，水又能夠讓我們涼爽。池塘、湖泊、云朵中的水看起來(lái)都很棒。那是因?yàn)槲覀冏陨淼?/3都是水，我們喜歡水，我們迷戀它。我們探索宇宙來(lái)尋找水的跡象，但當(dāng)我們回望地球的時(shí)候，發(fā)現(xiàn)她又小又暗，但是確閃耀著藍(lán)色。
It's good to be wet. Compared to our neighbors — Mars, Venus, the dust-dry Moon — we look the wettest. More than two thirds of our surface is ocean. Another twentieth is ice. Water, water, everywhere. We've got so much of it.
地球上有水真的很棒。與我們的鄰居相比——火星、金星、干燥多塵的月球——我們是最多水的。地球表面2/3都是海洋。另外1/20是冰。到處都是水。我們擁有很多的水。
Or do we?
但這是真的嗎？
There's an oceanographer in Hawaii, Mike Mottl by name, who's been measuring — or trying to measure — how much water we have on this planet, and his calculations are a little startling. When you stand on the shore of Lake Michigan, or the Pacific, the water supply looks impressive. But Mike changes perspective; he steps off the planet and considers the whole sphere, the surface, the crust, the mantle, the core and he asks, how much total water is there? Is Earth carrying a lot? Or a little?
在夏威夷有個(gè)叫做麥克莫特兒的海洋學(xué)家一直致力于測(cè)量或者嘗試測(cè)量地球上有多少水。他的結(jié)果有些令人震驚。當(dāng)你站在密歇根湖旁，抑或是太平洋邊，水撲面而來(lái)，讓人印象深刻。但是麥克改變視角；他著眼于地球之上，將地球看做一個(gè)整體，地表，地殼，地幔，地核，提出自己的疑問(wèn)：地球上有多少水？地球上的水是很多還是很少？
So he starts counting. First, of course, are our oceans. On a map there are five big ones, but combines them into one "global ocean."
于是他開(kāi)始計(jì)算。首先計(jì)算的肯定是海洋中的水資源。在下圖中有五大塊海洋，但是在計(jì)算中將它們總匯入一個(gè)“世界洋”。
Then come all the rivers, all the lakes, big and small ...
然后計(jì)算所有的河流，湖泊，無(wú)論大小。。。
Then the water in our atmosphere, the clouds, the fog, the moisture that hangs invisibly in the air...
然后計(jì)算大氣中的水分，云朵中，霧中，空氣中不可見(jiàn)的濕氣中。。。
Then, hidden below us, are the underground pools of water, aquifers, that show themselves in wadis or oases in the desert, that you touch when you dig a well deep into the ground...
然后，藏于我們之下的地下水，包括地下湖中的，地下蓄水層的，沙漠中干涸河道或者綠洲中的。只要你在地上挖一個(gè)深井，你就可以接觸到它們。
When Mike Mottl counts, he counts in Global Ocean units, all the oceans together. So when he adds up all the air, oceanic/lake/river and underground water he gets, roughly 1.2 "Global Oceans;" basically surface Earth is mostly ocean with a scoop of fresh water on top.
麥克莫特兒在計(jì)算時(shí)，把所有的大洋匯總到一起作為世界洋。然而，當(dāng)他將所有空氣中水，地表水以及地表水加起來(lái)時(shí)，大體上等于1.2個(gè)“世界洋”；基本上可以這么說(shuō)，地球表面上空是一個(gè)擁有巨量水源的大洋。
But we're not done...
但是我們依然沒(méi)有結(jié)束。。。
What about water inside the earth?
地球內(nèi)部的水呢？
There are three layers: the upper mantle, lower mantle and the core.
地球內(nèi)部分為三層：上地幔，下地幔以及地核。
In the upper mantle, or crust, there is water hiding in the tiny pores of certain "hydrous" minerals — in clay, in mica — and when conditions are right, that water can be squeezed out. When volcanoes erupt and you see a white billowing cloud hurtling to the sky, much of that is water vapor. Volcanoes belch water. How much is down there? Estimates vary (a lot) but Mottl figures there's maybe a fifth of a global ocean in the upper mantle.
在上地幔或者地殼中，有一些藏身于含水礦物質(zhì)——黏土和云母——的微孔中的水。一旦條件合適，水就可以釋放出來(lái)。當(dāng)您看到火山噴發(fā)時(shí)噴涌而出的白色浪云時(shí)，云朵中大部分是水蒸氣?；鹕絿娚涑鏊魵?。那么下面有多少呢？估計(jì)應(yīng)該有很多。但是莫特兒估計(jì)上地幔中的水應(yīng)該有1/5世界洋那么多。
In the lower, bigger mantle, the calculations get more theoretical, and therefore chancy, but he guesses anywhere from one tenth to 1.8 global oceans.
在更大的下地幔中，計(jì)算將更為理論化，因此可能不太準(zhǔn)確。麥克估計(jì)將會(huì)有0.1~1.8世界洋。
Then, all the way down, in the earth's core, nobody knows. There's enough capacity to house 60 oceans. Or maybe 100. The core could be very, very rich in hydrogen (a water ingredient) or totally dry. We have no data. Which leaves us in the odd position of not knowing where most of the Earth's water is. As Professor Mottl wrote me,
那么，繼續(xù)往下，沒(méi)有人知道地核之中的水有多少。地核可以儲(chǔ)存60個(gè)，或者100個(gè)大洋的水。地核中可能有巨量的氫（水分子的一種組分）或者完全干燥。我們沒(méi)有任何數(shù)據(jù)。這將讓我們處于一種奇怪的處境：不知道地球上哪里水最多，正如莫特兒教授信中所說(shuō)的那樣。
Is it in the oceans? Is it in the crust and mantle? Is it in the core? We don't know the answer to this question, as any one of these three could be the dominant reservoir
So I asked him: "If you had to make a rough calculation, right now, and no one's going to hold you to it, how much water do you think we have on earth?" And he said a conservative (albeit blind) guess would be the earth today carries with it 3 global oceans of water, 1/3 on top, where we can swim in it, sail on it, drink it, get rained on by it, and 2/3rds down below where it sits silently with the minerals.
哪里水最多呢？海洋？地殼和地幔？還是在地核中呢？我們不知道這個(gè)問(wèn)題的答案。三者都有可能是最大的水源儲(chǔ)藏地。
因此我問(wèn)道；“如果你現(xiàn)在有個(gè)粗略的計(jì)算，沒(méi)有人讓您為其負(fù)責(zé)。 那么你認(rèn)為地球上有多少水呢？”然后他說(shuō)（盡管有點(diǎn)盲人摸象的感覺(jué)），地球上應(yīng)該有三個(gè)世界洋那么多的水，1/3在上部，我們可以在里面游泳，航行，暢飲它同時(shí)也會(huì)被它淋到。另外的2/3都靜靜地藏身于地下礦物質(zhì)里。
Three global oceans of water! Sounds like a lot, no?
3個(gè)世界洋那么多的水！聽(tīng)起來(lái)很多，還不夠多嗎？
But from Mike's point of view, when you consider the mass of the earth, three oceans would take up less than one tenth of one percent of the planet. Think of your car. One tenth of one percent of your car would be smaller than a paper cup. (Well, it depends on the car, but you get the idea.) 0.1% is a tiny fraction.
但是從麥克的觀點(diǎn)來(lái)看，當(dāng)你考慮到地球的質(zhì)量的時(shí)候，3個(gè)世界洋的水也不足地球的1/1000.那你的車打個(gè)比方吧，車重量的1/1000還不如一個(gè)紙杯重呢。（雖然車的重量有大有小，但是你應(yīng)該明白了）。1/1000真的很少。
Not only could we carry a lot more, there are other heavenly bodies, Europa, one of Jupiter's moons, for example, that are almost ENTIRELY water. So compared to what's out there, or what could be out there, while the Earth looks so very, very wet, all that blue sloshing around on the surface, actually — when you look closely...we're pretty dry.
不僅地球可以承載更多水資源，其它天體也可以。舉個(gè)例子，木衛(wèi)二，木星的一個(gè)衛(wèi)星，幾乎全部是水。所以與那里的水資源相比，或者推測(cè)的相比，雖然地球上水很多，表面全部都是藍(lán)色的大洋，但是當(dāng)我們仔細(xì)觀察時(shí)。。。我們的水依然不多。
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Mike Mottl's paper (with Glazer, Kaiser and Meech) on Earth Water appeared in Water and Astrobiology. He and I have written back and forth, but I'm especially indebted to Mike's colleague Karen Meech, who walked me through this subject slowly and carefully. Any errors here, as usual, are all mine.
麥克米特爾（與Glazer,Kaiser和Meech)關(guān)于地球水源的文章將會(huì)在水和天體生物學(xué)上刊出。他和我來(lái)回探討了多次。我同樣要特別感謝麥克的同事Karen Meech，他循序漸進(jìn)的幫助我了解了這個(gè)學(xué)科。正如往常一樣，文章出現(xiàn)的的問(wèn)題，都是我的錯(cuò)誤。
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