科學家預測南極大型冰川消失的速率將會變得更快

原文網址：www.sciencedaily.com/releases/2016/05/160518133819.htm

Scientists predict extensive ice loss from huge Antarctic glacier

科學家預測南極大型冰川消失的速率將會變得更快

Current rates of climate change could trigger instability in a major Antarctic glacier, ultimately leading to more than 2m of sea-level rise.

現行的氣候變遷速率會造成南極的一條主要冰川變得相當不穩定，最終可能導致海面上升超過2公尺。

This is the conclusion of a new study looking at the future of Totten Glacier, a significant glacier in Antarctica. Totten Glacier drains one of the world's largest areas of ice, on the East Antarctic Ice Sheet (EAIS).

對托滕冰川(Totten Glacier)的未來命運進行的新研究導出了上述結論。托滕冰川是一條位於南極洲的大型冰川，它流經全世界最大的冰原之一—東南極冰原( East Antarctic Ice Sheet, EAIS)。

By studying the history of Totten's advances and retreats, researchers have discovered that if climate change continues unabated, the glacier could cross a critical threshold within the next century, entering an irreversible period of very rapid retreat.

研究人員藉由探討托滕冰川前進和後退的歷史，發現如果氣候變遷在未來仍未減緩，托滕冰川可能會在下個世紀內跨過一道臨界值，而進入再也無法挽回的極端快速消融期。

This would cause it to withdraw up to 300 kilometres inland in the following centuries and release vast quantities of water, contributing up to 2.9 metres to global sea-level rise.

這會造成托滕冰川在下個世紀往內陸退縮長達300公里並且融化出大量的淡水，導致全球海平面上升2.9公尺之多。

The EAIS is currently thought to be relatively stable in the face of global warming compared with the much smaller ice sheet in West Antarctica, but Totten Glacier is bucking the trend by losing substantial amounts of ice. The new research reveals that Totten Glacier may be even more vulnerable than previously thought.

在面臨全球暖化的威脅時，相較位在西南極面積小了許多的冰原來說，目前認為東南極冰原是較為穩定的地區。然而與此趨勢相反，托滕冰川其實已經流失了大量冰雪。新研究顯示跟我們過往認為的相比，托滕冰川實際上可能更加脆弱。

The study, by scientists from Imperial College London and institutions in Australia, the US, and New Zealand is published today in Nature. Last year, the team discovered that there is currently warm water circulating underneath a floating portion of the glacier that is causing more melting than might have been expected.

這篇今日刊登於期刊《自然》(Nature)的新研究由倫敦帝國學院以及澳洲、美國和紐西蘭學術機構的科學家進行。研究團隊去年發現在冰河漂浮於海面的部分的下方，目前於此循環的暖水融化冰河的能力可能比我們預期中還要超出許多。

Their new research looks at the underlying geology of the glacier and reveals that if it retreats another 100-150 km, its front will be sitting on an unstable bed and this could trigger a period of rapid retreat for the glacier. This would cause it to withdraw nearly 300 km inland from its current front at the coast.

他們的新研究著眼於托滕冰河之下的地質，並且發現如果冰河再繼續往後消退100至150公里，則它的前緣將會落在一個不穩定岩盤之上，這可能造成冰河進入一段快速消融期。結果將會使目前位於海岸附近的冰河前緣往內陸退縮將近300公里。

Retreating the full 300 km inland may take several hundred years, according to co-author Professor Martin Siegert, Co-Director of the Grantham Institute at Imperial College London. However, once the glacier crosses the threshold into the unstable region, the melting will be unstoppable -- at least until it has retreated to the point where the geology becomes more stable again.

根據倫敦帝國學院葛拉森研究所的共同作者 Martin Siegert教授所言，托滕冰河要往內陸後退整整300公里大概需要數百年的時間。然而，一旦冰河跨越臨界值而進入不穩定狀態，融化的趨勢就會變得銳不可擋—至少要等到冰河後退至地質再次穩定的地區為止。

"The evidence coming together is painting a picture of East Antarctica being much more vulnerable to a warming environment than we thought," he said. "This is something we should worry about. Totten Glacier is losing ice now, and the warm ocean water that is causing this loss has the potential to also push the glacier back to an unstable place."

「我們結合所有證據描繪出來的圖像顯示，在日趨暖化的環境下南極大陸東部跟我們過往認知中相比，實際上更為脆弱。」他說。「這確實是件我們應該要憂心的事情。托滕冰河的冰雪正不斷流失，而身為罪魁禍首的溫暖海水還可能會將冰河往後推至不穩定的環境。」

"Totten Glacier is only one outlet for the ice of the East Antarctic Ice Sheet, but it could have a huge impact. The East Antarctic Ice Sheet is by far the largest mass of ice on Earth, so any small changes have a big influence globally."

「雖然托滕冰河不過是東南極冰原往海洋流動的管道之一，但它仍可能會造成重大影響。東南極冰原身為當今地球上最大的冰層，任何一點小小的變動都可能對全世界造成巨大的衝擊。」

To uncover the history of Totten Glacier's movements, the team looked at the sedimentary rocks below the glacier using airborne geophysical surveys. From the geological record, influenced by the erosion by ice above, they were able to understand the history of the glacier stretching back millions of years.

為了瞭解托滕冰河移動的歷史，研究團隊利用空中地球物理探測來探測冰河下方的沉積岩。這些地質紀錄會受上方冰河侵蝕作用影響，藉此他們可以得知冰河數百萬年之前的歷史。

They found that the glacier has retreated more quickly over certain 'unstable' regions in the past. Based on this evidence, the scientists believe that when the glacier hits these regions again we will see the same pattern of rapid retreat.

他們發現過去冰河在經過某些不穩定地區時，冰河消融的速度會變得更快。科學家根據這些證據，認為當冰河未來再次經過這種地帶時，我們同樣會看見冰河進入這種快速倒退的模式。

引用自：Imperial College London. "Scientists predict extensive ice loss from huge Antarctic glacier." ScienceDaily. ScienceDaily, 18 May 2016. .

新研究對地球大球為何充滿氧氣提出了解釋

原文網址：www.sciencedaily.com/releases/2016/05/160516151935.htm

New answer to why Earth's atmosphere became oxygenated

新研究對地球大球為何充滿氧氣提出了解釋

Earth scientists from Rice University, Yale University and the University of Tokyo are offering a new answer to the long-standing question of how our planet acquired its oxygenated atmosphere.

來自萊斯大學、耶魯大學和東京大學的地球科學家對這個由來以久的問題給出了新解答：地球大氣如何氧化？

Based on a new model that draws from research in diverse fields including petrology, geodynamics, volcanology and geochemistry, the team's findings were published online this week in Nature Geoscience. They suggest that the rise of oxygen in Earth's atmosphere was an inevitable consequence of the formation of continents in the presence of life and plate tectonics.

根據結合了多個領域的模型，包括岩石學、地球動力學、火山學以及地球化學，研究團隊將他們的發現刊登於本周《自然—地質科學》(Nature Geoscience)期刊的線上版。他們提出的說法認為在生物和板塊運動已經出現的情況下，陸地的形成必然會使地球大氣中的氧含量上升。

"It's really a very simple idea, but fully understanding it requires a good bit of background about how Earth works," said study lead author Cin-Ty Lee, professor of Earth science at Rice. "The analogy I most often use is the leaky bathtub. The level of water in a bathtub is controlled by the rate of water flowing in through the faucet and the efficiency by which water leaks out through the drain. Plants and certain types of bacteria produce oxygen as a byproduct of photosynthesis. This oxygen production is balanced by the sink: reaction of oxygen with iron and sulfur in Earth's crust and by back-reaction with organic carbon. For example, we breathe in oxygen and exhale carbon dioxide, essentially removing oxygen from the atmosphere. In short, the story of oxygen in our atmosphere comes down to understanding the sources and sinks, but the 3-billion-year narrative of how this actually unfolded is more complex."

「這是個相當簡單的概念，但要充分了解它確實需要對地球的運作方式有一定的背景知識。」第一作者，萊斯大學的地球科學教授Cin-Ty Lee說。「我最常使用的分析方式可以類比為一座漏水的浴缸。此浴缸中的水位高低受控於從水龍頭流進來的水流量，以及排水孔將水排出的效率。植物以及某些種類的藍綠菌在進行光合作用時排出的副產物之一即為氧氣。這些產氧作用會跟某些消耗機制相互抵消：地殼中的鐵和硫會跟氧氣反應，還有形成有機碳的逆反應。此種逆反應像是我們會呼吸氧氣並排出二氧化碳，這就會將氧氣從大氣中移除。簡單來說，了解我們大氣中氧氣的來源以及它們如何被消耗，便能得知大氣氧含量變動的歷史，但要闡明這段30億年的故事實際上是如何運作當然複雜許多。」

Lee co-authored the study with Laurence Yeung and Adrian Lenardic, both of Rice, and with Yale's Ryan McKenzie and the University of Tokyo's Yusuke Yokoyama. The authors' explanations are based on a new model that suggests how atmospheric oxygen was added to Earth's atmosphere at two key times: one about 2 billion years ago and another about 600 million years ago.

Lee和同樣來自萊斯大學的Laurence Yeung及Adrian Lenardic、耶魯大學的Ryan McKenzie和東京大學的 Yusuke Yokoyama共同進行了此篇研究。他們奠基於新模型的解釋呈現出大氣中的氧氣是如何在兩段關鍵時期進入到地球大氣層當中：其中一段發生在大約20億年前，而另一段則是在6億年前左右。

Today, some 20 percent of Earth's atmosphere is free molecular oxygen, or O2. Free oxygen is not bound to another element, as are the oxygen atoms in other atmospheric gases like carbon dioxide and sulfur dioxide. For much of Earth's 4.5-billion-year history, free oxygen was all but nonexistent in the atmosphere.

現今地球大氣中約有20%是游離氧分子( free molecular oxygen)，也稱作 O₂。游離氧不像其他大氣氣體中的氧原子，譬如二氧化碳和二氧化硫，它們並未跟其他元素產生鏈結。但在地球45億年的歷史中，多半時期大氣當中幾乎不存在游離氧。

"It was not missing because it is rare," Lee said. "Oxygen is actually one of the most abundant elements on rocky planets like Mars, Venus and Earth. However, it is one of the most chemically reactive elements. It forms strong chemical bonds with many other elements, and as a result, it tends to remain locked away in oxides that are forever entombed in the bowels of the planet -- in the form of rocks. In this sense, Earth is no exception to the other planets; almost all of Earth's oxygen still remains locked away in its deep rocky interior."

「雖然游離氧很稀少但還不至於消失無蹤。」Lee說。「事實上，在火星、金星和地球這類的石質行星上，氧可說是含量最多的元素。然而，由於氧是最容易發生化學反應的元素之一，因此它們很容易就跟其他元素產生強力的化學鍵，這使得它們很容易被封鎖在氧化物當中，並且永遠埋藏在行星的臟腑當中—也就是岩石內部。從這個角度來看，與其他的行星相比地球並非例外，地球的氧幾乎仍封存在地球深處的岩石內部。」

Lee and colleagues showed that around 2.5 billion years ago, the composition of Earth's continental crust changed fundamentally. Lee said the period, which coincided with the first rise in atmospheric oxygen, was also marked by the appearance of abundant mineral grains known as zircons.

Lee和他的同僚們顯示大約在25億年前，地球大陸地殼的成分在本質上發生了改變。Lee說那段時期跟地球大氣中的氧氣首度上升剛好同步，另外還有一個相當明顯的特徵，那時出現了許多鋯石(zircon)礦物的顆粒。

"The presence of zircons is telling," he said. "Zircons crystallize out of molten rocks with special compositions, and their appearance signifies a profound change from silica-poor to silica-rich volcanism. The relevance to atmospheric composition is that silica-rich rocks have far less iron and sulfur than silica-poor rocks, and iron and sulfur react with oxygen and form a sink for oxygen.

「鋯石的出現述說了一切。」他說。「鋯石只會從特定成分的熔岩中結晶出來。它們的現身明顯透露出岩漿從缺少二氧化矽轉變成相當豐富，這是一項十分深遠的改變。大氣成分也因此連帶出現了變化，富含二氧化矽的岩石跟缺少二氧化矽的岩石相比，鐵和硫的含量低了許多，而這兩者正好會跟氧氣反應並吸收氧氣。」

"Based on this, we believe the first rise in oxygen may have been due to a substantial reduction in the efficiency of the oxygen sink," Lee said. "In the bathtub analogy, this is equivalent to partially plugging the drain."

「根據於此，我們深信氧氣濃度首次上升或許可歸因於氧氣被吸收的速率發生了明顯下降。」Lee說。「在浴缸的比喻當中，這就相當於排水孔有一部分被塞住了。」

Lee said the study suggests that the second rise in atmospheric oxygen was related to a change in production -- analogous to turning up the flow from the faucet.。

Lee說這項研究認為大氣氧含量第二次上升則跟產生速率的變化相關—這可類比成將水龍頭的出水量轉得更大。

"The bathtub analogy is simple and elegant, but there's an added complication that must be taken into account," he said. "That is because oxygen production is ultimately tied to the global carbon cycle -- the cycling of carbon between Earth, the biosphere, the atmosphere and oceans."

「浴缸比喻確實相當簡單且優雅，但實際上仍得考慮到另一項更加複雜的作用。」他說。「這是因為氧氣的產生歸根究柢跟全球碳循環有密切的關係。碳循環是碳在地球生物圈、大氣層與海洋之間的循環流動。」

Lee said the model showed that Earth's carbon cycle has never been at a steady state because carbon slowly leaks out as carbon dioxide from Earth's deep interior to the surface through volcanic activity. Carbon dioxide is one of the key ingredients for photosynthesis.

Lee說模型顯示地球的碳循環從未達到穩定的狀態，這是因為經由火山活動碳會持續以二氧化碳的形式從地球深處漏往地表，而二氧化碳又是光合作用的關鍵原料之一。

"On long, geologic timescales, carbon is removed from the atmosphere by the production of condensed forms of carbon, such as organic carbon and minerals called carbonate," he said. "For most of Earth's history, most of this carbon has been deposited not in the deep ocean but rather on the margins of continents. The implications are profound because carbon deposited on continents does not return to Earth's deep interior. Instead, it amplifies carbon inputs into the atmosphere when the continents are subsequently perturbed by volcanism."

「就長久的地質時間尺度來看，將碳沉降成固態型式的作用，像是產生有機碳或稱作碳酸鹽類的礦物，都會將碳從大氣中移除。」他說。「在地球歷史上的大部分期間，這些碳並未沉積在深海而是在大陸邊緣。這具有相當重要的意涵，因為沉積在大陸的碳並不會返回地球深處；相反地，當大陸之後受到火山作用擾動時，這會增加更多進入大氣中的碳。」

Lee said the team's model showed that volcanic activity and other geologic inputs of carbon into the atmosphere may have increased with time, and because oxygen production is tied to carbon production, oxygen production also must increase. The model showed that the second rise in atmospheric oxygen had to occur late in Earth's history.

Lee說團隊的模型顯示火山活動以及其他會將碳輸送至大氣的地質作用可能會隨著時間經過而更加活躍，且由於氧氣增加跟碳的產生有密切關係，因此氧氣產量必定會隨之提升。模型顯示大氣氧含量第二次提昇會發生在地球史上較為近代的時間。

"Exactly when is model-dependent, but what is clear is that the formation of continental crust naturally leads to two rises in atmospheric oxygen, just as we see in the fossil record," Lee said.

「雖然確切的發生時間是由模型給出，但從化石紀錄中我們可以很明顯地看到大陸地殼的形成會順理成章地導致大氣層氧含量提升兩次。」Lee說。

Exactly what caused the composition of the crust to change during the first oxygenation event remains a mystery, but Lee said the team believes it may have been related to the onset of plate tectonics, where Earth's surface, for the first time, became mobile enough to sink back down into Earth's deep interior.

第一次氧化事件時，地殼成分變化的確切成因仍然是個謎團，但Lee說他們的團隊認為這可能跟板塊運動開始運作有關。這是地球歷史上地表首度具有足夠的動力可以下沉回地球深處。

Lee said the team's new model is not without controversy. For example, the model predicts that production of carbon dioxide must increase with time, a finding that goes against the conventional wisdom that carbon fluxes and atmospheric carbon dioxide levels have steadily decreased over the last 4 billion years.

Lee說他們團隊的新模型也並非完全沒有爭議。舉例來說，該模型預測二氧化碳的產量會隨著時間增加，但這項發現卻跟一般常識認為的相反，過往認為碳進入大氣層的速率以及大氣二氧化碳的含量在過去40億年來會隨著時間穩定下降。

"The change in flux described by our model happens over extremely long time periods, and it would be a mistake to think that these processes that are bringing about any of the atmospheric changes are occurring due to anthropomorphic climate change," he said. "However, our work does suggest that Earth scientists and astrobiologists may need to revisit what we think we know about Earth's early history."

「我們模型中描述的速率變化是在極長一段時間中慢慢發生的，因此若認為導致這些大氣變化的作用中有任何一項是起因於人為導致的氣候變遷，那完全是項謬誤。」他說。「然而，我們的成果確實告訴地球科學家和天體生物學家，也許有必要重新思量我們對地球早期歷史所知的一切。」

引用自：Rice University. "New answer to why Earth's atmosphere became oxygenated." ScienceDaily. ScienceDaily, 16 May 2016. 

發現從地球形成時期殘留至今的痕跡

原始網址：www.sciencedaily.com/releases/2016/05/160512145338.htm

Found: Surviving evidence of Earth's formative years

發現從地球形成時期殘留至今的痕跡

New work from a team including Carnegie's Hanika Rizo and Richard Carlson, as well as Richard Walker from the University of Maryland, has found material in rock formations that dates back to shortly after Earth formed. The discovery will help scientists understand the processes that shaped our planet's formative period and its internal dynamics over the last 4.5 billion years. It is published by Science.

包括卡內基的研究人員Hanika Rizo和Richard Carlson，以及馬里蘭大學的Richard Walker在內的團隊進行的新研究，發現在岩層當中有些物質的形成年代可追溯至地球形成後不久。這項刊登於期刊《科學》(Science)的發現有助於科學家了解地球形成時期受哪些作用影響，以及過去45億年來我們星球內部發生的動力作用。

Earth formed from the accretion of matter surrounding the young Sun. The heat of its formation caused extensive melting of the planet, leading Earth to separate into two layers when the denser iron metal sank inward toward the center, creating the core and leaving the silicate-rich mantle floating above.

地球是由環繞在幼年太陽周遭的物質加積而成。在形成時產生的熱量造成整顆行星幾乎處於融化的狀態，此時密度較高的鐵往中心下沉而形成地核，剩餘下來富含矽酸鹽類的地函就浮在上方，造成地球被分成兩層。

Over the subsequent 4.5 billion years of Earth's evolution, convection in Earth's interior, like water boiling on a stove, caused deep portions of the mantle to rise upwards, melt, and then separate once again by density. The melts, since they were less dense than the unmelted rock, rose to form Earth's crust, while the denser residues of the melting sank back downward, altering the mantle's chemical composition in the process.

在接下來45億年的地球演化過程中，地球內部發生的對流就像鍋爐上的滾水一樣，會造成地函深部的物質上湧、熔化，並再次因為密度差而分離。由於熔化部分的密度較未熔化的岩石低，因此它們會往上浮而形成地球地殼，熔化剩下來較為緻密的物質則往下沉回去，在過程中這些殘留物會改變地函的化學成分。

The mantle residues of crust formation were previously believed to have mixed back into the mantle so thoroughly that evidence of the planet's oldest geochemical events, such as core formation, was lost completely.

過往認為地殼形成過程中殘留下來的地函物質會沉回去並跟地函其他部分徹底混合，而完全抹除像是地核形成這類最古老的地球化學事件留下來的痕跡。

However, the research team--which also included Sujoy Mukhopadhyay and Vicky Manthos of University of California Davis, Don Francis of McGill University, and Matthew Jackson, a Carnegie alumnus now at University of California Santa Barbara--was able find a geochemical signature of material left over from the early melting events that accompanied Earth's formation. They found it in relatively young rocks both from Baffin Island, off the coast of northern Canada, and from the Ontong-Java Plateau in the Pacific Ocean, north of the Solomon Islands.

同時包括加利福尼亞大學戴維斯分校的Sujoy Mukhopadhyay和Vicky Manthos、麥基爾大學的Don Francis以及現任職於加利福尼亞大學聖塔芭芭拉分校，曾是卡內基研究員的Matthew Jackson在內的團隊，卻發現了從地球形成時伴隨發生的早期熔化事件中，殘留下來的物質攜帶的地球化學訊號。他們從加拿大北方外海的巴芬島(Baffin Island)，以及太平洋索羅門群島北方的安通-爪哇海底高原(Ontong-Java Plateau)上，年代相對較年輕的岩石中發現了這些訊號。

These rock formations are called flood basalts because they were created by massive eruptions of lava. The solidified lava itself is only between 60 and 120 million years old, depending on its location. But the team discovered that the molten material from inside Earth that long ago erupted to create these plains of basaltic rock owes its chemical composition to events that occurred over 4.5 billion years in the past.

這些岩層是由大規模的岩漿噴發而形成，因此稱作洪流玄武岩(flood basalt)。經由它們的位置研究團隊推測這些岩漿凝固的年代大約只有6000萬至1億2000萬年。然而，他們發現許久以前從地球內部噴發而形成這些玄武岩平原的熔融物質，其化學成分卻起源自發生在45億年前之久的事件。

Here's how they figured it out:

以下為他們的發現過程：

They measured variations in these rocks of the abundance of an isotope of tungsten--the same element used to make filaments of incandescent light bulbs. Isotopes are versions of an element in which the number of neutrons in each atom differs from the number of protons. (Each element contains a unique number of protons.) These differing neutron numbers mean that each isotope has a slightly different mass.

他們測量了這些岩石當中一種鎢同位素含量的變化。鎢即是用來製作白熾燈泡的燈絲的原料。同位素則是相同一種元素然而中子數不同的版本，這跟質子數並不相同(每一種元素的質子數都是獨一無二的)。這種在中子數上的差異意味著每個同位素之間的質量都有些微差距。

Why tungsten? Tungsten contains one isotope of mass 182 that is created when an isotope of the element hafnium undergoes radioactive decay, meaning its elemental composition changes as it gives off radiation. The time it takes for half of any quantity of hafnium-182 to decay into tungsten-182 is 9 million years. This may sound like a very long time, but is quite rapid when it comes to planetary formation timescales. Rocky planets like Earth or Mars took about 100 million years to form.

為什麼是鎢？當元素發生放射性衰變時，它會在發散出輻射的同時改變其組成。鎢擁有一種質量數為182的同位素，它是由一種鉿(hafnium，讀音同「哈」)同位素發生放射性衰變時產生。要讓任何數量的鉿-182其中一半轉變成鎢-182需要的時間為900萬年。這聽起來或許是段很長的時間，但是跟行星形成花費的時間一比就顯得相當短暫了。要形成一顆像是地球或火星這樣的石質行星，通常需要1億年左右。

The team determined that the basalts from Baffin Island, formed by a 60-million-year-old eruption from the mantle hot-spot currently located beneath Iceland, and the Ontong-Java Plateau, which was formed by an enormous volcanic event about 120 million years ago, contain slightly more tungsten-182 than other young volcanic rocks.

巴芬島的玄武岩是於6000萬年前由現今位在冰島下方的地函熱點(hot spot)噴發而產生，安通爪哇海底高原上的玄武岩則是在1億2000萬年前由一個大型火山噴發事件造成。研究團隊檢驗了這些玄武岩，發現跟其他較年輕的火山岩相比，它們的鎢-182含量多了一些。

Because all the hafnium-182 decayed to tungsten-182 during the first 50 million years of Solar System history, these findings indicate that the mantle material that melted to form the flood basalt rocks that the team studied originally had more hafnium than the rest of the mantle. The likely explanation for this is that the portion of Earth's mantle from which the lava came had experienced a different history of iron separation than other portions of the mantle (since tungsten is normally removed to the core along with the iron.)

由於所有的鉿-182在太陽系歷史上最初的5000萬年就已經全數衰變成鎢-182，因此這項發現意味著研究團隊最初研究的這些洪流玄武岩，熔融而形成它們的地函物質跟地函其餘部分相比之下擁有較多的鉿。可能的解釋是形成這些岩漿的地函跟地函其他部分相較而言，鐵的分離歷程有些許不同。（因為正常情況之下鎢會隨著鐵一起沉到地核中）

It was a surprise to the team that such material still exists in Earth's interior.

地球內部仍存有這樣的物質令研究團隊感到十分震驚。

"This demonstrates that some remnants of the early Earth's interior, the composition of which was determined by the planet's formation processes, still exist today," explained lead author Rizo, now at Université du Québec à Montréal.

「這表示早期地球內部的殘渣仍有一些留存至今日，它們的成分取決於地球形成的過程。」現任職於魁北克大學蒙特婁分校的第一作者 Rizo解釋。

"The survival of this material would not be expected given the degree to which plate tectonics has mixed and homogenized the planet's interior over the past 4.5 billion years, so these findings are a wonderful surprise," added Carlson, Director of Carnegie's Department of Terrestrial Magnetism.

「在經過了過去45億年來板塊運動攪動地球內部並使其成分趨向均勻的情況下，我們並沒有預料到這些物質仍能倖存，因此這項發現確實是個十分美好的驚喜。」卡內基研究所地磁系的主任Carlson補充說。

The team's discovery offers new insight into the chemistry and dynamics that shaped our planet's formative processes. Going forward, scientists will have to hunt for other areas showing outsized amounts of tungsten-182 with the hope of illuminating both the earliest portion of Earth's history as well as the place in Earth's interior where this ancient material is stored.

研究團隊的這項發現讓我們對塑造地球的化學和動力過程有了新的見解。這群科學家的下一步是尋找其他同樣擁有過量鎢-182的地體，他們希望這可以讓他們闡明地球歷史最剛開始時發生的事物，並且找到這些遠古物質究竟儲存在地球內部何處。

引用自：Carnegie Institution for Science. "Found: Surviving evidence of Earth's formative years." ScienceDaily. ScienceDaily, 12 May 2016. 

宇宙微塵揭露遠古大氣的成分

原始網址：www.sciencedaily.com/releases/2016/05/160511154214.htm

Cosmic dust reveals Earth's ancient atmosphere

宇宙微塵揭露遠古大氣的成分

Using the oldest fossil micrometeorites -- space dust -- ever found, Monash University-led research has made a surprising discovery about the chemistry of Earth's atmosphere 2.7 billion years ago.

利用自古以來發現的最古老微隕石化石—宇宙塵，蒙納許大學領導的研究對27億年前的大氣化學成分做出了驚人的發現。

The findings of a new study published today in the journal Nature -- led by Dr Andrew Tomkins and a team from the School of Earth, Atmosphere and Environment at Monash, along with scientists from the Australian Synchrotron and Imperial College, London -- challenge the accepted view that Earth's ancient atmosphere was oxygen-poor. The findings indicate instead that the ancient Earth's upper atmosphere contained about the same amount of oxygen as today, and that a methane haze layer separated this oxygen-rich upper layer from the oxygen-starved lower atmosphere.

由蒙納許大學地球、大氣與環境學院的 Andrew Tomkins博士及團隊率領，偕同來自澳洲同步輻射中心、倫敦帝國學院的科學家，於今日刊登在期刊《自然》（Nature）的研究中，挑戰了地球遠古大氣相當缺乏氧氣的普遍看法。這項發現指出地球古代的高層大氣含氧量與現今相若，且有一層甲烷霧霾將富含氧的高層大氣從缺氧的低層大氣隔絕開來。

Dr Tomkins explained how the team extracted micrometeorites from samples of ancient limestone collected in the Pilbara region in Western Australia and examined them at the Monash Centre for Electron Microscopy (MCEM) and the Australian Synchrotron.

Tomkins博士解釋他們的團隊是如何從西澳皮爾布拉(Pilbara)地區的遠古石灰岩樣品中萃取出微隕石，並在澳洲同步輻射中心和蒙納許電子顯微鏡中心檢視它們。

"Using cutting-edge microscopes we found that most of the micrometeorites had once been particles of metallic iron -- common in meteorites -- that had been turned into iron oxide minerals in the upper atmosphere, indicating higher concentrations of oxygen than expected," Dr Tomkins said.

「我們利用最先進的顯微鏡發現這些微隕石大都曾是隕石中常見的金屬鐵微粒，它們在經過高層大氣時被轉變成氧化鐵礦物，顯示當時氧氣濃度比預期中的還要高。」Tomkins 博士說。

"This was an exciting result because it is the first time anyone has found a way to sample the chemistry of the ancient Earth's upper atmosphere," Dr Tomkins said.

「這個結果相當令人興奮。因為這是人們首度發現有一種方法可以用來取樣遠古大氣高層的化學性質。」Tomkins 博士說。

Imperial College researcher Dr Matthew Genge -- an expert in modern cosmic dust -- performed calculations that showed oxygen concentrations in the upper atmosphere would need to be close to modern day levels to explain the observations.

帝國學院的Matthew Genge博士是研究現代宇宙塵的專家，他經由計算顯示當時高層大氣的氧氣濃度必須要相當接近現今的數值才能解釋觀測結果。

"This was a surprise because it has been firmly established that the Earth's lower atmosphere was very poor in oxygen 2.7 billion years ago; how the upper atmosphere could contain so much oxygen before the appearance of photosynthetic organisms was a real puzzle," Dr Genge said.

「我對這個結果感到相當驚訝，因為已經有很確切的證據指出27億年前地球的低層大氣相當缺乏氧氣，然而高層大氣何以能在行使光合作用的生物出現之前含有那麼多氧氣，確實是個謎團。」Genge博士說。

Dr Tomkins explained that the new results suggest the Earth at this time may have had a layered atmosphere with little vertical mixing, and higher levels of oxygen in the upper atmosphere produced by the breakdown of CO 2 by ultraviolet light.

Tomkins博士解釋這項新結果顯示那時地球或許擁有分層明顯的大氣，少有垂直混和(vertical mixing)的現象，而高層大氣的高濃度氧氣應該是由紫外線分解二氧化碳所產生。

"A possible explanation for this layered atmosphere might have involved a methane haze layer at middle levels of the atmosphere. The methane in such a layer would absorb UV light, releasing heat and creating a warm zone in the atmosphere that would inhibit vertical mixing," Dr Tomkins said.

「會產生這樣分層明顯的大氣，可能之一的解釋跟大氣中間有一層甲烷霧霾有關。像這樣的甲烷層可以吸收紫外線，並釋放出熱能而在大氣當中製造出一個暖區，進而抑制垂直混和發生。」Tomkins 博士說。

"It is incredible to think that by studying fossilised particles of space dust the width of a human hair, we can gain new insights into the chemical makeup of Earth's upper atmosphere, billions of years ago." Dr Tomkins said.

「想想我們藉由研究跟人髮寬度相仿的宇宙塵微粒化石，就能得到關於上億年前地球高層大氣化學組成的新資訊，這真的是件相當驚人的事情。」

Dr Tomkins outlined next steps in the research.

Tomkins博士大致說明了他們之後的研究方向。

"The next stage of our research will be to extract micrometeorites from a series of rocks covering over a billion years of Earth's history in order to learn more about changes in atmospheric chemistry and structure across geological time. We will focus particularly on the great oxidation event, which happened 2.4 billion years ago when there was a sudden jump in oxygen concentration in the lower atmosphere."

「我們研究的下一個階段將是從各種岩石中萃取出微隕石，它們會涵蓋地球歷史數十億年以上的時間。這是為了得知在不同的地質年代，大氣成分和結構會如何變化的更多相關資訊。我們將會特別專注在發生於24億年前的大氧化事件(great oxidation event)，在當時低層大氣的氧濃度突然地躍昇。」

引用自：Monash University. "Cosmic dust reveals Earth's ancient atmosphere." ScienceDaily. ScienceDaily, 11 May 2016. 

是什麼造成了壯觀的夏威夷-天皇海山鍊(Hawaiian-Emperor seamount chain)變得如此彎折？

原始網址：www.sciencedaily.com/releases/2016/05/160511142351.htm

How the spectacular Hawaiian-Emperor seamount chain became so bendy

是什麼造成了壯觀的夏威夷-天皇海山鍊(Hawaiian-Emperor seamount chain)變得如此彎折？

The physical mechanism causing the unique, sharp bend in the Hawaiian-Emperor seamount chain has been uncovered in a collaboration between the University of Sydney and the California Institute of Technology (Caltech).

在雪梨大學和加州理工學院的合作之下，終於找出了可以用來解釋夏威夷-天皇海山鍊中獨一無二的急轉彎是如何形成的物理機制。

Led by a PhD candidate at the University of Sydney's School of Geosciences, researchers used the Southern Hemisphere's most highly integrated supercomputer to reveal flow patterns deep in the Earth's mantle -- just above the core -- over the past 100 million years. The flow patterns explain how the enigmatic bend in the Hawaiian-Emperor seamount chain arose.

在雪梨大學地質科學院的博士候選人領導之下，研究人員利用南半球效能最強的超級電腦展現出緊鄰地核正上方的深層地函過去1億年來的流動模式。這可以用來解釋夏威夷-天皇海山鍊中謎樣的轉折究竟是如何形成。

True to the old adage -- as above, so below -- the Sydney-US collaboration found the shape of volcanic seamount chains (chains of mostly extinct volcanoes), including Hawaii, is intimately linked to motion near the Earth's core.

如同一句古老格言所說：「如其在上，如其在下(As above, so below)。」雪梨跟美國大學的合作成果發現了包括夏威夷在內的海山鍊(排成鍊狀的火山，其中大都為死火山)，其形態跟地核附近的地函運動息息相關。

The findings of PhD candidate Rakib Hassan and fellow researchers including Professor Dietmar Müller from the University's EarthByte Group, are being published in Nature.

此篇刊登於《自然》的研究由博士候選人Rakib Hassan 進行，共同研究人員包括了雪梨大學地球位元團隊的成員之一， Dietmar Müller教授。

Mr Hassan explained: "Until now, scientists believed the spectacular 60° bend in the Hawaiian seamount chain -- not found in any other seamount chains -- was related to a change in plate motion combined with a change in flow direction in the shallow mantle, the layer of thick rock between the Earth's crust and its core.

Hassan解釋：「目前為止科學家仍然認為出現在夏威夷海山鍊中十分引人注目的60度彎曲，這項未在其他海山鍊中出現的特徵，跟板塊運動方向以及淺層地函流向的改變有關。地函是位在地球地核跟地殼中間，厚度相當厚的岩石。」

"These findings suggest the shape of volcanic seamount chains record motion in the deepest mantle, near the Earth's core. The more coherent and rapid the motion deep in the mantle, the more acute its effects are on the shape of seamount chains above," he said.

「這項發現也告訴我們海底火山鍊的型態紀錄了地核附近的深層地函是如何運動。地函深部的運動越一致且迅速，對上方海山鍊型態造成的影響就會越劇烈。」他說。

Although solid, the mantle is in a state of continuous flow, observable only over geological timescales. Vertical columns of hot and buoyant rock rising through the mantle from near the core are known as mantle plumes. Volcanic seamount chains such as Hawaii were created from magma produced near the surface by mantle plumes. Moving tectonic plates sit above the mantle and carry newly formed seamounts away from the plume underneath -- the oldest seamounts in a chain are therefore furthest away from the plume.

地函雖為固體，但它其實處於持續緩緩流動的狀態，不過這樣的運動只能從地質時間尺度來看才能觀察到。稱作地函柱(mantle plume)的高熱且上湧的柱狀岩石會從將近地核處往上升並穿過地函，它在接近地表處產生的岩漿會形成像夏威夷這類的海底火山鍊。在地函上方移動的板塊會將新形成的海山帶離下方的地函柱，造成海山鍊中最老的海山會離地函柱最遠。

"We had an intuition that, since the north Pacific experienced a prolonged phase where large, cold tectonic plates uninterruptedly sank into the mantle, the flow in the deepest mantle there would be very different compared to other regions of the Earth," Mr Hassan said.

「既然北太平洋很長一段時間都處於低溫的大型板塊不斷往地函下沉的環境，直覺告訴我們在這裡地函最深處的運動必然會跟地球上其他地區大不相同。」 Hassan說。

One of the most contentious debates in geoscience has centred on whether piles of rock in the deep mantle -- to which plumes are anchored -- have remained stationary, unaffected by mantle flow over hundreds of millions of years.

地質科學中最眾說紛紜的爭論之一便聚焦於地函深處的岩石，也就是地函柱的根基所在，是否在數億年的時光中能固定在同一個地方，不受地函流動影響。

The new research shows the shapes of these piles have changed through time and their shapes can be strongly dependent on rapid, coherent flow in the deep mantle.

這項新研究顯示這些岩石的形狀會隨著時間變化，且跟深部地函一致且迅速的流動密切相關。

Between 50-100 million years ago, the edge of the pile under the north Pacific was pushed rapidly southward, along with the base of Hawaii's volcanic plume, causing it to tilt. The plume became vertical again once the motion of its base stopped; this dramatic start-stop motion resulted in the seamount chain's sharp bend.

在5000萬年到1億年前，在北太平洋之下這些岩石的邊界迅速地往南推進，夏威夷火山地函柱的根基也連帶著移動，使得整根地函柱傾斜。然而，一旦這個運動停止下來，地函柱便會再次回復直立的狀態。這種劇烈地停止及運動的交互發生，造成海山鍊發生急遽的轉彎。

Using Australia's National Computational Infrastructure's supercomputer Raijin, the team created high-resolution three-dimensional simulations of mantle evolution over the past 200 million years to understand the coupling between convection in the deep Earth and volcanism.

研究團隊利用澳洲國家計算基礎建設中心的超級電腦「雷神(Raijin)」創建了高解析度的三維模型，可以顯現過去2億年來地函的演化過程，並從中了解地球深部的對流跟火山活動之間的關聯。

Mr Hassan said the simulations were guided by surface observations -- similar to meteorologists applying past measurements to predict the weather.

Hassan先生說這項模擬是以地表的觀測結果為基礎來進行，這跟大氣學家利用過往累積的觀測結果來預報天氣之間有異曲同工之處。

"These simulations required millions of central processing unit (CPU) hours on the supercomputer over the course of the project," he said.

「在整個計畫執行的過程中，光是進行模擬就得花上超級電腦的中央處理器數百萬個小時。」他說。

Professor Müller concluded: "Our results help resolve a major enigma of why volcanic seamount chains on the same tectonic plate can have very different shapes.

Müller教授總結說：「我們的結果可以幫助科學家解答這個謎題：為什麼在同一座板塊中，不同海底火山鍊之間的型態可以如此截然不同。」

"It is now clear that we first need to understand the dynamics of the deepest 'Underworld', right above the core, to unravel the history of volcanism at Earth's surface," said Professor Müller.

「我們現在相當明瞭首先要了解『地底世界』的最深處，也就是緊鄰地核處發生了何種動力過程，才能闡明地表火山活動為何會擁有這樣的歷史。」 Müller教授說。

Watch the animation here https://youtu.be/Xy5kHjAHXec

連結此網址來觀看動畫https://youtu.be/Xy5kHjAHXec

引用自：University of Sydney. "How the spectacular Hawaiian-Emperor seamount chain became so bendy." ScienceDaily. ScienceDaily, 11 May 2016. 

地球早期空氣的重量不到現在大氣的一半

原始網址：www.sciencedaily.com/releases/2016/05/160509115114.htm

Early Earth's air weighed less than half of today's atmosphere

地球早期空氣的重量不到現在大氣的一半

The idea that the young Earth had a thicker atmosphere turns out to be wrong. New research from the University of Washington uses bubbles trapped in 2.7 billion-year-old rocks to show that air at that time exerted at most half the pressure of today's atmosphere.

地球幼年時擁有厚重大氣層的想法現在看來似乎是錯的。華盛頓大學進行的新研究利用了27億年前困在岩石中的氣泡，顯示當時空氣造成的壓力頂多只有現今大氣的一半而已。

The results, published online May 9 in Nature Geoscience, reverse the commonly accepted idea that the early Earth had a thicker atmosphere to compensate for weaker sunlight. The finding also has implications for which gases were in that atmosphere, and how biology and climate worked on the early planet.

以往被廣為接受的想法中認為早期地球擁有厚重的大氣層並遮蔽了陽光，但刊登在5月9日《自然—地質科學》(Nature Geoscience)線上版的研究結果卻顛覆了這個說法。這項發現對於了解地球早期的空氣成分、氣候運作方式和生物的行為，也都具有相當的啟發。

"For the longest time, people have been thinking the atmospheric pressure might have been higher back then, because the sun was fainter," said lead author Sanjoy Som, who did the work as part of his UW doctorate in Earth and space sciences. "Our result is the opposite of what we were expecting."

「一直以來人們都因為當時的陽光較現今微弱，而認為那時的大氣壓力會比較高。」第一作者Sanjoy Som說。這是他於華盛頓大學攻讀地球與太空科學博士學位時進行的研究中的一部分。「然而我們的成果卻跟我們預設的恰好相反。」

The idea of using bubbles trapped in cooling lava as a "paleobarometer" to determine the weight of air in our planet's youth occurred decades ago to co-author Roger Buick, a UW professor of Earth and space sciences. Others had used the technique to measure the elevation of lavas a few million years old. To flip the idea and measure air pressure farther back in time, researchers needed a site where truly ancient lava had undisputedly formed at sea level.

華盛頓大學地球與太空科學教授Roger Buick，同時也是本文的共同作者，在幾十年前就已經想到說可以把岩漿冷卻後困在其中的氣泡作為「古氣壓計」，來測量地球年輕時大氣的重量。其他的研究通常用這項技術測定數百萬年前岩漿噴發時位於的海拔高度。但本篇研究的人員則反向利用這個概念來得知過去的大氣壓力，為了執行這個想法，他們需要一處年代十分久遠的熔岩，其生成位置必須要位於海平面的高度。

Their field site in Western Australia was discovered by co-author Tim Blake of the University of Western Australia. There, the Beasley River has exposed 2.7 billion-year-old basalt lava. The lowest lava flow has "lava toes" that burrow into glassy shards, proving that molten lava plunged into seawater. The team drilled into the overlying lava flows to examine the size of the bubbles.

他們的野外工作地點是由共同作者，西澳大學的Tim Blake 發現。稱作Beasley River的這個地方有27億年前的玄武岩熔岩出露。他們發現熔岩流在地勢最低處的「熔岩趾(lava toe)」具有玻璃質孔洞，證實了這片熔岩流曾經流進海水當中。研究團隊接著在上方的熔岩流上鑽孔，以檢視氣泡的大小。

A stream of molten rock quickly cools from top and bottom, and bubbles trapped at the bottom are smaller than those at the top. The size difference records the air pressure pushing down on the lava as it cooled, 2.7 billion years ago.

熔岩流動時會從上而下快速地冷卻，造成困於底部的氣泡會比頂端的要小。它們的尺寸差距即成為了27億年前，熔岩冷卻當下大氣對它施加壓力大小的紀錄。

Rough measurements in the field suggested a surprisingly lightweight atmosphere. More rigorous x-ray scans from several lava flows confirmed the result: The bubbles indicate that the atmospheric pressure at that time was less than half of today's.

在野外粗略的估計就顯示出當時大氣重量輕的令人驚訝。在以更加精確的X光掃描了數個熔岩流樣品後確立了以下結論：氣泡指出當時的大氣壓力比現在的一半還要低。

Earth 2.7 billion years ago was home only to single-celled microbes, sunlight was about one-fifth weaker, and the atmosphere contained no oxygen. But this finding points to conditions being even more otherworldly than previously thought. A lighter atmosphere could affect wind strength and other climate patterns, and would even alter the boiling point of liquids.

27億年前的地球僅有一些單細胞生物生存於此，而陽光比現在弱了將近8成，大氣也完全沒有氧氣。但這個發現指出當時的地球可能比之前認為的更像外星世界。較稀薄的大氣會影響風的強度以及其他氣候模式，甚至還會改變液體的沸點。

"We're still coming to grips with the magnitude of this," Buick said. "It's going to take us a while to digest all the possible consequences." Other geological evidence clearly shows liquid water on Earth at that time, so the early atmosphere must have contained more heat-trapping greenhouse gases, like methane and carbon dioxide, and less nitrogen.

「我們仍然在釐清這會帶來多大的影響。」Buick說。「要整理出所有可能發生的效應得花上我們一段時間。」其他的地質證據顯示當時地表已經擁有液態水，因此早期大氣勢必要含有更多可以關住熱量的溫室氣體，像是甲烷、二氧化碳以及少量的氮氣。

The new study is an advance on the UW team's previous work on "fossilized raindrops" that first cast doubt on the idea of a far thicker ancient atmosphere. The result also reinforces Buick's 2015 finding that microbes were pulling nitrogen out of Earth's atmosphere some 3 billion years ago.

華盛頓大學團隊繼先前以「雨滴化石」的研究而首度對遠古大氣相當濃厚的說法拋出質疑後，這篇研究更進一步地鞏固了他們的論述。結論也支持了Buick於2015年發現將近30億年前的微生物，會從地球大氣中吸收氮氣的研究。

"The levels of nitrogen gas have varied through Earth's history, at least in Earth's early history, in ways that people just haven't even thought of before," said co-author David Catling, a UW professor of Earth and space sciences. "People will need to rewrite the textbooks."

「直到不久前才有人去仔細思考在整個地球歷史，或者至少是在地球歷史的早期，氮氣在大氣中的濃度是如何變化的。」共同作者，華盛頓大學的地球與太空科學家David Catling說。「人們需要為此而重新編撰教科書。」

The researchers will next look for other suitable rocks to confirm the findings and learn how atmospheric pressure might have varied through time.

研究人員接下來的目標是放在尋找其他符合條件的岩石，以驗證他們的發現並且試著去了解大氣壓力隨著時間可能是如何變化的。

While clues to the early Earth are scarce, it is still easier to study than planets outside our solar system, so this will help understand possible conditions and life on other planets where atmospheres might be thin and oxygen-free, like that of the early Earth.

雖然關於早期地球樣貌的是如此稀少，但是跟研究太陽系之外的行星一比還是簡單許多，因此這或許有助於我們了解跟早期地球相似，大氣層稀薄且不含氧氣的其他行星上的環境條件以及生命形式可能的樣貌。

Som is CEO of Seattle-based Blue Marble Space, a nonprofit that focuses on interdisciplinary space science research, international awareness, science education and public outreach. He currently does astrobiology research at NASA's Ames Research Center in California.

Som是Blue Marble Space組織的執行長，此非營利組織位於西雅圖，主要業務著重於跨領域太空科學研究、國際關懷事務、科學教育及推廣ㄧ。他目前於加州NASA艾姆斯研究中心從事有關天體生物學的研究。

引用自：University of Washington. "Early Earth's air weighed less than half of today's atmosphere." ScienceDaily. ScienceDaily, 9 May 2016.