Well, you know, sometimes the most important things come in the smallest packages. I am going to try to convince you, in the 15 minutes I have, that microbes have a lot to say about questions such as, "Are we alone?" and they can tell us more about not only life in our solar system but also maybe beyond, and this is why I am tracking them down in the most impossible places on Earth, in extreme environments where conditions are really pushing them to the brink of survival. Actually, sometimes me too, when I'm trying to follow them too close. But here's the thing: We are the only advanced civilization in the solar system, but that doesn't mean that there is no microbial life nearby. In fact, the planets and moons you see here could host life -- all of them -- and we know that, and it's a strong possibility. And if we were going to find life on those moons and planets, then we would answer questions such as, are we alone in the solar system? Where are we coming from? Do we have family in the neighborhood? Is there life beyond our solar system?
古語有云: 合抱之木,生于毫末; 九層之台,起于壘土。 接下來的一刻鐘裏, 大家會發現 微生物世界暗藏玄機, 有可能幫助解開 人類身世的謎題。 對微生物世界的探索, 還將開拓我們對太陽系 及系外生命的認知。 正是懷著這樣的信念, 我不辭艱辛, 遠赴地球一隅追尋 微生物的足跡, 見證它們在極端環境下 的生存狀態。 環境之惡劣與嚴峻, 令我自己都望而却步。 普遍認同的觀點是, 雖然人類社會是太陽系 唯一的高等文明, 但並不意味著, 附近星系沒有微生物存在。 像這些行星及其衛星 都有可能是生命的家園, 我們對此較爲確信。 一旦在這些星球上發現生命, 我們也許能回答以下問題: 太陽系裏人類是否孑然一身? 我們來自何方? 附近星系中是否有我們的親戚? 太陽系之外是否有生命存在?
And we can ask all those questions because there has been a revolution in our understanding of what a habitable planet is, and today, a habitable planet is a planet that has a zone where water can stay stable, but to me this is a horizontal definition of habitability, because it involves a distance to a star, but there is another dimension to habitability, and this is a vertical dimension. Think of it as conditions in the subsurface of a planet where you are very far away from a sun, but you still have water, energy, nutrients, which for some of them means food, and a protection. And when you look at the Earth, very far away from any sunlight, deep in the ocean, you have life thriving and it uses only chemistry for life processes.
諸如此類的問題沒有窮盡, 因爲對於什麽星球適合生存、居住, 我們的認識一直在變化。 時至今日,我們認爲適宜居住的星球 應該環繞著大氣圈, 幫助保持水分。 但對我而言,這只是衡量 適宜居住的一個橫軸, 只要與恒星之間存在 合適的距離即可滿足這一要求; 還需要有一個衡量維度—— 縱軸, 借此衡量地表以下的生存條件。 地表之下遠離太陽, 生命仍然需要水分、能量 和營養來維持, 對於一些生命而言, 這是指食物和庇護之所。 比如我們的地球, 在遠離光照的深海之底, 依然萬物繁衍,生生不息。 生命進程全仰賴化學作用。
So when you think of it at that point, all walls collapse. You have no limitations, basically. And if you have been looking at the headlines lately, then you will see that we have discovered a subsurface ocean on Europa, on Ganymede, on Enceladus, on Titan, and now we are finding a geyser and hot springs on Enceladus, Our solar system is turning into a giant spa. For anybody who has gone to a spa knows how much microbes like that, right? (Laughter)
從這個角度來審視生命, 我們獲得了開闊的視界。 如果各位關注科學界的重大新聞, 應該知道我們最近 在木衛二、木衛三、土衛二和 土衛六上發現了次表層海洋, 又在土衛二上找到了間歇泉和溫泉。 太陽系搖身一變, 似乎成了巨型SPA會所! SPA會所裏有多少微生物? 各位曾光顧會所的人有切身體會。 (笑聲)
So at that point, think also about Mars. There is no life possible at the surface of Mars today, but it might still be hiding underground.
我們再來看看火星的情况。 在火星表面尚未發現生命, 但生命有可能隱藏於地表之下。
So, we have been making progress in our understanding of habitability, but we also have been making progress in our understanding of what the signatures of life are on Earth. And you can have what we call organic molecules, and these are the bricks of life, and you can have fossils, and you can minerals, biominerals, which is due to the reaction between bacteria and rocks, and of course you can have gases in the atmosphere. And when you look at those tiny green algae on the right of the slide here, they are the direct descendants of those who have been pumping oxygen a billion years ago in the atmosphere of the Earth. When they did that, they poisoned 90 percent of the life at the surface of the Earth, but they are the reason why you are breathing this air today.
我們對“適宜居住”的概念 有了更深的認識, 同時對地球上的生命信號 也有新的瞭解。 這些生命信號包括有機分子, 它是構成生命的基本材料; 還包括化石、 礦物,以及生物礦物—— 這是細菌與岩石反應的産物; 大氣中的各類氣體當然 也是生命信號之一。 請看畫面右側, 這些微小的綠藻, 正是十億年前 向地球大氣層釋放氧氣 的原始藻類植物的後裔。 在釋放大量氧氣的同時, 它們毒殺了地球表面90%的生命, 這些生命的消失 成全了人類的今天。
But as much as our understanding grows of all of these things, there is one question we still cannot answer, and this is, where are we coming from? And you know, it's getting worse, because we won't be able to find the physical evidence of where we are coming from on this planet, and the reason being is that anything that is older than four billion years is gone. All record is gone, erased by plate tectonics and erosion. This is what I call the Earth's biological horizon. Beyond this horizon we don't know where we are coming from.
儘管我們的知識與日俱增, 但仍然無法回答一個問題: 我們來自何方? 而且,回答問題的難度 似乎在增加—— 因爲我們無法找到實物證據 證明我們來自地球何處。 四十億年前的所有證據 已蕩然無存, 各種記錄都銷聲匿跡, 在板塊構造和氣候 變遷中湮滅無痕。 我把這種未知的生命源頭 稱作“生物地平綫”, 生命來自地平綫之外的何處, 我們一無所知。
So is everything lost? Well, maybe not. And we might be able to find evidence of our own origin in the most unlikely place, and this place in Mars.
是否尚存蛛絲馬跡?也許。 我們也許有可能在火星 這個最不可能的地方, 發現人類起源的證據。
How is this possible? Well clearly at the beginning of the solar system, Mars and the Earth were bombarded by giant asteroids and comets, and there were ejecta from these impacts all over the place. Earth and Mars kept throwing rocks at each other for a very long time. Pieces of rocks landed on the Earth. Pieces of the Earth landed on Mars. So clearly, those two planets may have been seeded by the same material. So yeah, maybe Granddady is sitting there on the surface and waiting for us. But that also means that we can go to Mars and try to find traces of our own origin. Mars may hold that secret for us. This is why Mars is so special to us.
爲什麽呢? 在太陽系形成之初, 火星和地球 都遭受了小行星和彗星的猛烈撞擊, 撞擊造成碎片四處飛濺。 地球與火星相互投擲石塊, “戰况”不斷。 大量巨石襲擊了地球, 同時也有來自地球的巨石落入火星。 所以,兩個行星可能包含著孕育 生命的相同物質, 火星表面也許埋藏著 我們原始祖先的秘密。 爲此,我們有必要啓程去火星, 尋找生命之源, 解開身世之謎。 火星對人類的意義十分特殊。
But for that to happen, Mars needed to be habitable at the time when conditions were right. So was Mars habitable? We have a number of missions telling us exactly the same thing today. At the time when life appeared on the Earth, Mars did have an ocean, it had volcanoes, it had lakes, and it had deltas like the beautiful picture you see here. This picture was sent by the Curiosity rover only a few weeks ago. It shows the remnants of a delta, and this picture tells us something: water was abundant and stayed founting at the surface for a very long time. This is good news for life. Life chemistry takes a long time to actually happen.
如果火星當時存在生命, 它必定是適宜居住的星球。 火星當時是否適宜居住呢? 多項科研探索證實了同一事實: 地球上最初出現生命的時候, 火星上存在海洋、火山和湖泊, 甚至還有如此美麗的三角洲。 這張照片由“好奇號”火星探測車 於幾個星期前發回, 顯示了三角洲地區的遺迹, 並告訴我們 火星在相當長一段時間內, 湖泊密布,江河奔流—— 無疑都是孕育生命的溫床。 生命的進化過程步履蹣跚, 曠日持久,
So this is extremely good news, but does that mean that if we go there, life will be easy to find on Mars? Not necessarily.
這對于我們研究生命有利。 但我們去到火星之後, 是否就能輕易找到生命呢? 未必。
Here's what happened: At the time when life exploded at the surface of the Earth, then everything went south for Mars, literally. The atmosphere was stripped away by solar winds, Mars lost its magnetosphere, and then cosmic rays and U.V. bombarded the surface and water escaped to space and went underground. So if we want to be able to understand, if we want to be able to find those traces of the signatures of life at the surface of Mars, if they are there, we need to understand what was the impact of each of these events on the preservation of its record. Only then will we be able to know where those signatures are hiding, and only then will we be able to send our rover to the right places where we can sample those rocks that may be telling us something really important about who we are, or, if not, maybe telling us that somewhere, independently, life has appeared on another planet.
讓我們簡單回顧 火星經歷的劇變。 當地球上的生命蓬勃發展時, 火星則每况愈下, 日暮途窮。 火星的大氣層被太陽風席捲而去, 磁層破壞殆盡, 宇宙射綫和紫外綫長驅直入, 直抵火星地表, 水分逃逸到太空或滲入地下。 假如我們要瞭解並發現 火星上的生命信號—— 前提是它們的確存在, 我們需要考慮這一系列變遷 對火星生命記錄的保存 所産生的影響。 只有這樣,我們才能知曉 生命信號的藏身之處, 然後驅使火星探測車前往, 對岩石等進行採樣、研究, 嘗試破解人類的起源之謎; 或者,我們有望發現 其他星球存在生命的佐證
So to do that, it's easy. You only need to go back 3.5 billion years ago in the past of a planet. We just need a time machine.
方法似乎並不困難, 我們只需要 穿越到35億年前 的那顆行星。 我們只需要一台時光機,
Easy, right? Well, actually, it is. Look around you -- that's planet Earth. This is our time machine. Geologists are using it to go back in the past of our own planet. I am using it a little bit differently. I use planet Earth to go in very extreme environments where conditions were similar to those of Mars at the time when the climate changed, and there I'm trying to understand what happened. What are the signatures of life? What is left? How are we going to find it? So for one moment now I'm going to take you with me on a trip into that time machine.
對吧? 完全正確。 請環顧四周, 我們所在的行星地球 就是我們的時光機, 它載著地質學家回溯 到遠古時代。 但是,我的用法略有不同, 我搭乘這台時光機, 進入條件類似于當時 火星的極端環境中。 當時,火星經歷了氣候劇變, 我嘗試理解這些劇變 所帶來的影響。 什麼是生命的印記? 凡走過必留下痕跡?我們要如何追尋? 現在我就將帶你們 穿越時空隧道。
And now, what you see here, we are at 4,500 meters in the Andes, but in fact we are less than a billion years after the Earth and Mars formed. The Earth and Mars will have looked pretty much exactly like that -- volcanoes everywhere, evaporating lakes everywhere, minerals, hot springs, and then you see those mounds on the shore of those lakes? Those are built by the descendants of the first organisms that gave us the first fossil on Earth.
你可以看到我們已經來到了4,500米之遙的安第斯山脈, 但事實上這是在地球和火星成型后的近十億年后。 那時的地球和火星看起來 可能到處都是火山群, 正在蒸發的湖泊隨處可見, 礦石、溫泉、 還有在湖岸邊的土丘? 它們都是由最初構成地球的化石 衍變出的物質組成。
But if we want to understand what's going on, we need to go a little further. And the other thing about those sites is that exactly like on Mars three and a half billion years ago, the climate is changing very fast, and water and ice are disappearing. But we need to go back to that time when everything changed on Mars, and to do that, we need to go higher. Why is that? Because when you go higher, the atmosphere is getting thinner, it's getting more unstable, the temperature is getting cooler, and you have a lot more U.V. radiation. Basically, you are getting to those conditions on Mars when everything changed.
但如果我們希望弄清之後的事,就必須再往前看。 這些地方的另一景象 和三十五億年前的火星十分相像, 氣候驟變,你看不到水源和冰川。 但我們必須回到火星不穩定的那一刻, 要這麼做,我們就必須往高處去。 你問為什麼? 因為位置越高, 大氣層越細,環境越不穩定, 溫度越來越低,你會受到更多紫外線輻射 基本上, 對於瞬息萬變的火星來說,這種情況是常有的。
So I was not promising anything about a leisurely trip on the time machine. You are not going to be sitting in that time machine. You have to haul 1,000 pounds of equipment to the summit of this 20,000-foot volcano in the Andes here. That's about 6,000 meters. And you also have to sleep on 42-degree slopes and really hope that there won't be any earthquake that night. But when we get to the summit, we actually find the lake we came for. At this altitude, this lake is experiencing exactly the same conditions as those on Mars three and a half billion years ago. And now we have to change our voyage into an inner voyage inside that lake, and to do that, we have to remove our mountain gear and actually don suits and go for it. But at the time we enter that lake, at the very moment we enter that lake, we are stepping back three and a half billion years in the past of another planet, and then we are going to get the answer came for. Life is everywhere, absolutely everywhere. Everything you see in this picture is a living organism. Maybe not so the diver, but everything else. But this picture is very deceiving. Life is abundant in those lakes, but like in many places on Earth right now and due to climate change, there is a huge loss in biodiversity. In the samples that we took back home, 36 percent of the bacteria in those lakes were composed of three species, and those three species are the ones that have survived so far.
所以我不能說這次時光旅行會是次休閒之旅。 其實當時你並非在搭乘時光機。 你必須扛著1000磅重的裝備攀上安第斯山脈 高達20,000英呎的火山頂峰。 全程距離約為6,000米。 而且你只能在42度的斜坡上就寢 祈禱那晚不會發生地震吧。 但當我們攀上頂峰上,將能親見找尋的湖泊。 處於這個高度的湖泊呈現的現狀 火星上三十五億前的湖泊無異。 現在,我們將更改行程, 深入探究那條湖泊的“內涵”, 為趕去那,我們必須放棄登山裝備 這些裝備的確是負擔,還是輕裝上陣。 當我們一旦踏入湖泊中,每深入一步, 就表示我們離重返 三十五億年前的另一個星球又近了一點, 我們已經接近謎底了。 這裡充滿生靈,四處都有生物的氣息。 你所見的都是鮮活的有機物。 它們可能不是潛鳥,但確定是某種生物。 眼前的景象令人迷惑。 這些湖泊中充滿生命體, 可是和目前地球的某些地區相似,受氣候變化影響 生物多樣性受重創,損失嚴重。 我們反觀地球上的取樣結果, 這些湖泊中36%的細菌由三種物種組成, 這三種物種至今仍存活。
Here's another lake, right next to the first one. The red color you see here is not due to minerals. It's actually due to the presence of a tiny algae. In this region, the U.V. radiation is really nasty. Anywhere on Earth, 11 is considered to be extreme. During U.V. storms there, the U.V. Index reaches 43. SPF 30 is not going to do anything to you over there, and the water is so transparent in those lakes that the algae has nowhere to hide, really, and so they are developing their own sunscreen, and this is the red color you see. But they can adapt only so far, and then when all the water is gone from the surface, microbes have only one solution left: They go underground. And those microbes, the rocks you see in that slide here, well, they are actually living inside rocks and they are using the protection of the translucence of the rocks to get the good part of the U.V. and discard the part that could actually damage their DNA. And this is why we are taking our rover to train them to search for life on Mars in these areas, because if there was life on Mars three and a half billion years ago, it had to use the same strategy to actually protect itself. Now, it is pretty obvious that going to extreme environments is helping us very much for the exploration of Mars and to prepare missions. So far, it has helped us to understand the geology of Mars. It has helped to understand the past climate of Mars and its evolution, but also its habitability potential. Our most recent rover on Mars has discovered traces of organics. Yeah, there are organics at the surface of Mars. And it also discovered traces of methane. And we don't know yet if the methane in question is really from geology or biology. Regardless, what we know is that because of the discovery, the hypothesis that there is still life present on Mars today remains a viable one.
相鄰第一條湖旁還有另一條湖。 因礦物質影響湖水已泛紅。 這完全是因為湖水中有微藻。 該地區的紫外線輻射極其嚴重。 縱觀地球,有11個地區堪稱狀況嚴峻。 紫紫外線風暴肆虐期間, 這裡的紫外線指數高達43。 在那裡,防曬指數達30的防曬物品根本不起作用, 而湖水卻清澈透明 微藻清晰可見, 形成天然屏障, 也就是你所看到的一片鮮紅色。 但這不是長久之計, 一旦湖面的湖水乾涸, 微生物的生路就只剩下: 轉移至地下。 而你在另一張幻燈片中看到的微生物、岩石 都是湖泊中真實存在的岩石 他們利用岩石的半透明性, 吸收紫外線中的有利部分, 剔除有損DNA的部分,以達到保護作用。 這也就是我們駕選擇漫步火星 探索這些地區生命體的原因, 因為如果三十五億年前火星已有生命體存在, 他們必須採用相同的策略進行自我保護。 所以,顯然前往環境條件極端的地區 將極其有助於我們 探索火星,做好準備工作。 迄今為止,我們已藉此掌握了 火星的地質情況。 這有助於了解火星過去的 氣候狀況和演變情況, 但它仍有適合生物居住的潛力。 我們近期漫遊火星時已發現了有機物的蹤跡。 沒錯,火星表面的確有有機物存活。 我們還發現火星有甲烷存在。 我們尚未明確有待驗證的甲烷 是因地質原因還是生物質原因造成。 無論如何,我們所掌握的是通過探索 對于火星目前仍有生命存在的假設 仍然有可能成立。
So by now, I think I have convinced you that Mars is very special to us, but it would be a mistake to think that Mars is the only place in the solar system that is interesting to find potential microbial life. And the reason is because Mars and the Earth could have a common root to their tree of life, but when you go beyond Mars, it's not that easy. Celestial mechanics is not making it so easy for an exchange of material between planets, and so if we were to discover life on those planets, it would be different from us. It would be a different type of life. But in the end, it might be just us, it might be us and Mars, or it can be many trees of life in the solar system. I don't know the answer yet, but I can tell you something: No matter what the result is, no matter what that magic number is, it is going to give us a standard by which we are going to be able to measure the life potential, abundance and diversity beyond our own solar system. And this can be achieved by our generation. This can be our legacy, but only if we dare to explore.
贅述到此,我想我應該能說服 各位火星對於我們有特殊意義, 但認為火星是太陽系唯一一顆 值得探索潛在微生物的星球, 也可能是一種錯誤想法。 這是因為火星和地球 的生命樹可能是同根同源, 但如果你跳出火星去看, 並非如此簡單。 天體力學成為了兩顆星球間 物質轉換的障礙, 所以,如果我們去探索 這些星球的生命體, 會發現他們與我們截然不同。 是兩種不同類的生命體。 但最終,剩下的可能只有我們, 可能是我們,是火星 也可能是太陽系中的其它生命樹。 我無從解答,但我能說的是: 無論結果如何,無論神秘數字是什麼 它都為我們衡量我們身處的太陽系以外 的生命潛力、充分性 和多樣性樹立了標準。 這有待我們的下一代去完成。 只有我們勇於探索, 才能為後人留下有價值的東西。
Now, finally, if somebody tells you that looking for alien microbes is not cool because you cannot have a philosophical conversation with them, let me show you why and how you can tell them they're wrong. Well, organic material is going to tell you about environment, about complexity and about diversity. DNA, or any information carrier, is going to tell you about adaptation, about evolution, about survival, about planetary changes and about the transfer of information. All together, they are telling us what started as a microbial pathway, and why what started as a microbial pathway sometimes ends up as a civilization or sometimes ends up as a dead end.
最後, 如果有人不認為探索 外星微生物很了不起, 因為你無法與他們進行有意義的對話, 那我將向這些人證明為什麼你們錯了。 有機物能向你傳達有關環境、 生物複雜性和多樣性的信息。 DNA或各種信息載體能夠讓你了解 有關適應性、演變、生存、 行星變化及轉移的信息。 總之,進行這些研究能夠令我們了解 何為微生物路徑的開端, 為何曾是微生物路徑的開端 對象有時會成為文明的終結 或最終滅亡。
Look at the solar system, and look at the Earth. On Earth, there are many intelligent species, but only one has achieved technology. Right here in the journey of our own solar system, there is a very, very powerful message that says here's how we should look for alien life, small and big. So yeah, microbes are talking and we are listening, and they are taking us, one planet at a time and one moon at a time, towards their big brothers out there. And they are telling us about diversity, they are telling us about abundance of life, and they are telling us how this life has survived thus far to reach civilization, intelligence, technology and, indeed, philosophy.
縱觀太陽系和地球。 地球上的物種很多充滿智慧, 但僅一種將其變為技術。 我們的太陽系之旅到此階段, 已經能獲得強烈的訊息 即我們應該如何從微觀到 宏觀的看待外星生物。 微生物們在發聲, 我們應該精心聆聽, 他們將帶領我們 從星球到月球 逐步了解他們的其它兄弟。 他們向我們傳達著生物多樣性、 充分性的信息, 也讓我們了解到至今形成文明、智能、 技術和真正的哲學為止 生命如何求生存。
Thank you.
謝謝。
(Applause)
(鼓掌)