研究火星得到的線索指出生命搖籃的可能場所

原文網址：https://www.jpl.nasa.gov/news/news.php?feature=6966

研究火星得到的線索指出生命搖籃的可能場所

在火星發現古代海床熱液沉積物的證據，證實火星某處或許可以提供地球生命起源線索的想法。

最近一則國際報告檢視了美國太空總署的火星偵察軌道器(MRO)，對火星南部一處盆地中的大量沉積物的觀察結果。作者解讀資料後，認為其證實了這些沉積物是在許久以前，火星地殼中火山活動頻繁之處的熱水從海底流出而形成的說法。

「就算我們從未在火星找到生命曾經存於其上的證據，此處還是能告訴我們地球上的生命可能在何種環境誕生的線索。」美國休士頓NASA詹森太空中心的Paul Niles表示，「火山活動跟靜止水體的組合，提供的環境條件跟大約同一時間存在於地球上的十分類似——早期生命便是於此時此地演化出來。」

今日的火星既無靜止水體也無火山活動。研究人員估計這些火星沉積物是在37億年前左右由海底熱液活動造成。地球大約同時間的海底熱液環境則是地球生命起源的熱門候選時間地點之一。現今地球仍有此種環境存在，其中繁榮生長著各式各樣完全不需陽光，而是從岩石取出化學能的生物。在木衛二和土衛二這類冰質衛星內部有海底熱液活動的可能性，使得它們成為尋找地外生命任務時深感興趣的目標。

火星艾瑞達尼亞盆地(Eridania basin)的所在區域有部分是這顆紅色行星表面最古老的地殼。MRO的火星專用小型偵察影像頻譜儀(CRISM)提供的觀測資料可以用來辨識盆地內部堆積的大量沉積物含有何種礦物。

「此處呈現的故事使我們相信當時這裡有座存在許久、深度頗深的海洋，且底部擁有熱液環境。」Niles表示，「這讓我們想起地球上的深海熱液環境，或許其他世界的生命也會在類似環境發現。生命不需要有宜人的大氣層或是溫暖的地表才能生存，只需要岩石、熱和水即可。」

Niles是這篇近期發表於《自然通訊》(Nature Communications)的共同作者之一，主要作者Joseph Michalski於倫敦自然史博物館時最先開始分析這些資料，其他共同作者則是美國亞利桑那州圖森市行星科學研究所和倫敦自然史博物館的人員。

研究人員估計古代艾瑞達尼亞盆地擁有大約21萬立方公里的水量，多達古代火星其他所有湖泊和海洋的總和，同時也是美國五大湖總體積的9倍之餘。從頻譜儀的數據可以辨識出這些礦物係由蛇紋石、滑石和碳酸鹽等混雜而成，加上厚層岩床的形狀與紋理，使得研究人員認定其可能為海床熱液沉積物。在海洋消失之後，該區域轉而被岩漿覆蓋。研究人員以此為證，表示該區域為火星地殼中受到火山活動影響的區域，也同時解釋了當海洋還在時為何會有前述的熱液沉積物產生。

這項新成果增添了一筆新證據顯示火星曾經擁有相當多樣的有水環境，包括河流、湖泊、三角洲、海洋、溫泉、地下水、以及冰下噴發的火山。

報告聲稱「艾瑞達尼亞盆地的古代深海熱液沉積物代表了新的一種在火星上尋找地外生物的目標。」並表示，「艾瑞達尼亞盆地的底部不只讓探勘火星的研究人員深感興趣，它也讓我們得以一窺早期地球的樣貌。」這是因為地球上最古老的生命證據來自於類似年代與成因的海洋沉積物，但是地球早期環境的地質紀錄卻保存得十分差勁。

Mars Study Yields Clues to Possible Cradle of Life

The discovery of evidence for ancient sea-floor hydrothermal deposits on Mars identifies an area on the planet that may offer clues about the origin of life on Earth.

A recent international report examines observations by NASA's Mars Reconnaissance Orbiter (MRO) of massive deposits in a basin on southern Mars. The authors interpret the data as evidence that these deposits were formed by heated water from a volcanically active part of the planet's crust entering the bottom of a large sea long ago.

"Even if we never find evidence that there's been life on Mars, this site can tell us about the type of environment where life may have begun on Earth," said Paul Niles of NASA's Johnson Space Center, Houston. "Volcanic activity combined with standing water provided conditions that were likely similar to conditions that existed on Earth at about the same time -- when early life was evolving here."

Mars today has neither standing water nor volcanic activity. Researchers estimate an age of about 3.7 billion years for the Martian deposits attributed to seafloor hydrothermal activity. Undersea hydrothermal conditions on Earth at about that same time are a strong candidate for where and when life on Earth began. Earth still has such conditions, where many forms of life thrive on chemical energy extracted from rocks, without sunlight. But due to Earth's active crust, our planet holds little direct geological evidence preserved from the time when life began. The possibility of undersea hydrothermal activity inside icy moons such as Europa at Jupiter and Enceladus at Saturn feeds interest in them as destinations in the quest to find extraterrestrial life.

Observations by MRO's Compact Reconnaissance Spectrometer for Mars (CRISM) provided the data for identifying minerals in massive deposits within Mars' Eridania basin, which lies in a region with some of the Red Planet's most ancient exposed crust.

"This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment," Niles said. "It is evocative of the deep-sea hydrothermal environments on Earth, similar to environments where life might be found on other worlds -- life that doesn't need a nice atmosphere or temperate surface, but just rocks, heat and water."

Niles co-authored the recent report in the journal Nature Communications with lead author Joseph Michalski, who began the analysis while at the Natural History Museum, London, and co-authors at the Planetary Science Institute in Tucson, Arizona, and the Natural History Museum.

The researchers estimate the ancient Eridania sea held about 50,000 cubic miles (210,000 cubic kilometers) of water. That is as much as all other lakes and seas on ancient Mars combined and about nine times more than the combined volume of all of North America's Great Lakes. The mix of minerals identified from the spectrometer data, including serpentine, talc and carbonate, and the shape and texture of the thick bedrock layers, led to identifying possible seafloor hydrothermal deposits. The area has lava flows that post-date the disappearance of the sea. The researchers cite these as evidence that this is an area of Mars' crust with a volcanic susceptibility that also could have produced effects earlier, when the sea was present.

The new work adds to the diversity of types of wet environments for which evidence exists on Mars, including rivers, lakes, deltas, seas, hot springs, groundwater, and volcanic eruptions beneath ice.

"Ancient, deep-water hydrothermal deposits in Eridania basin represent a new category of astrobiological target on Mars," the report states. It also says, "Eridania seafloor deposits are not only of interest for Mars exploration, they represent a window into early Earth." That is because the earliest evidence of life on Earth comes from seafloor deposits of similar origin and age, but the geological record of those early-Earth environments is poorly preserved.

原始論文Joseph R. Michalski, Eldar Z. Noe Dobrea, Paul B. Niles, Javier Cuadros. Ancient hydrothermal seafloor deposits in Eridania basin on Mars. Nature Communications, 2017; 8: 15978 DOI: 10.1038/ncomms15978

引用自：NASA/Jet Propulsion Laboratory. "Mars study yields clues to possible cradle of life."

地震有徵兆嗎？

原文網址：http://www.mccormick.northwestern.edu/news/articles/2017/10/do-earthquakes-have-a-tell.html

地震有徵兆嗎？

數據科學家和地震學家利用「深層微地動」來預報大地震

研究人員長久以來有很好的理由相信地震本質上就是不可預測的，但西北大學研究人員做出的新發現卻可能大幅撼動此舊思維。

「慢地震」釋放能量的時間長達數小時至數個月。一組跨領域研究團隊發現慢地震或許會引發鄰近地區發生「一般地震」。這項發現可以幫助地震學家在一定時間以前預測出某些大地震即將發生，讓他們能發出預警並做好防備來減少生命財產的損害。

「雖然地殼中應力累積的多寡大部分來說是可以預測的，但透過一般地震來釋放應力的過程性質卻較為渾沌，造成預測它們可能發生的時間相當困難。」西北大學複雜系統研究所的數據科學學者Kevin Chao表示。「但近幾年越來越多的研究發現隱沒帶的大地震發生之前常常有前震或是慢地震出現。」

這項由國家科學基金會補助的研究刊登於《地球物理研究期刊：固體地球》。論文第一作者Chao同時也是西北大學優化與統計學習中心的成員。此外，西北大學文理學院的地球與行星科學教授Suzan van der Lee也參與了這項研究。

Chao和他的同事於數年前將目光轉往台灣其中一處而開始這項研究。台灣擁有大約100座經年累月持續記錄地面移動的地震站。研究團隊在台灣注意到深層微地動的訊號，這是一種以數天至數週為週期重複發生的慢地震。

Chao表示：「深層微地動對微小的應力變化十分敏感。因此我們決定把它當作應力儀，來監測大地震發生之前與之後當地應力的累積與釋放有何變化。」

為了感應並監測深層微地動的活動，Chao的團隊發展出一套精密的數學方法來處理從台灣10座地震站得到的數據。2010年3月台灣南部發生了一場規模6.4的地震，他們發現大約二個月之前深層微地動的行為開始出現變化。舉例來說，在地震發生之前微地動的持續時間增加了二倍，且在地震之後仍持續增加。

雖然科學家首度於2002年發表深層微地動的存在，卻還沒有發現太多在大地震之前行為有所改變的案例。「在規模6.4的地震發生之後，我們注意到事件前後的深層微地動有值得研究的潛力。」Chao表示，「我們辨識出在地震前三週微地動的持續時間有所增加，但起初我們還無法下定結論，因為微地動的發生頻率隨時都有可能受到不同因素而增長。」

但在規模6.4的地震發生三年之後，Chao和同事注意到他們對微地動的觀測結果跟附近GPS站的紀錄有吻合之處，其指出微地動來源附近的地表移動方向有所轉變。

結合大地觀測(像是GPS和地震站)得到的數據以及一系列的演算法，團隊顯示深層微地動的模式變化可以做為附近即將發生地震的徵兆。為了進一步驗證這項發現，Chao檢驗了另外四場地震並發現此種預警模式確實存在。他和Van der Lee期許這項成果可以啟發地震學領域中更多以資料為導向的研究。

他說：「在發展出可靠的中長期地震預警方法之前，對這些微小但有趣的微地動訊號進行更加大量的資料分析是必須的。」

Do Earthquakes Have a ‘Tell’?

Data scientists and seismologists use “deep tremor” to forecast strong earthquakes

Researchers have long had good reason to believe that earthquakes are inherently unpredictable. But a new finding from Northwestern University might be a seismic shift for that old way of thinking.

An interdisciplinary team recently discovered that “slow earthquakes,” which release energy over a period of hours to months, could potentially lead to nearby “regular earthquakes.” The finding could help seismologists better forecast some strong earthquakes set to occur within a certain window of time, enabling warnings and other preparations that may save lives.

“While the build-up of stress in the Earth’s crust is largely predictable, stress release via regular earthquakes is more chaotic in nature, which makes it challenging to predict when they might occur,” said Kevin Chao, a data science scholar in the Northwestern Institute on Complex Systems (NICO). “But in recent years, more and more research has found that large earthquakes in subduction zones are often preceded by foreshocks and slow earthquakes.”

Supported by the National Science Foundation, the research was published in the Journal of Geophysical Research: Solid Earth. Chao, who is also a member of Northwestern’s Center for Optimization and Statistical Learning, served as the paper’s first author. Suzan van der Lee, a professor of earth and planetary sciences in Northwestern’s Weinberg College of Arts and Sciences, also contributed to the work.

Chao and his colleagues began their work several years ago by turning to a region within Taiwan, home to approximately 100 seismic stations that have continuously recorded ground motion for years. It was there the team noticed deep tremors, a type of slow earthquake that typically recurs in days- or weeks-long cycles.

“Deep tremor is very sensitive to small stress changes,” Chao said. “So, we decided to use them as stress meters to monitor local variations in stress build-up and release before and after large earthquakes.”

To detect and monitor this deep tremor activity, Chao’s team developed a sophisticated set of algorithms and applied it to data from 10 seismic stations in Taiwan. They discovered that deep tremor started to change its behavior about two months before the occurrence of a 6.4-magnitude earthquake in March 2010 in southern Taiwan. The tremor’s duration, for example, increased by two-fold before this event and continued to increase afterwards.

Although deep tremor was first reported in 2002, scientists have not found many cases in which behavior changed before large earthquakes. “After the 6.4-magnitude earthquake occurred, we noticed a potential to study deep tremor near the event,” Chao said. “We identified the increase in tremor duration three weeks before the earthquake, but we initially could not draw conclusions because tremor rates increase all the time and for different reasons.

But three years after the 6.4-magnitude, Chao and his colleagues noticed that their observations of tremor activity coincided with nearby a GPS recording, which indicated a flip in the direction of ground motion near tremor sources. 

By combining data from earth observatories, such as GPS and seismic stations, with statistics and a series of algorithms, the team showed that changes in deep tremor patterns could signal an impending earthquake nearby. To further test the finding, Chao examined four additional earthquakes and discovered that similar precursory patterns did exist. He and Van der Lee hope that this work will inspire more data-driven research in the seismology field.

“Much more data analysis of these tiny but fascinating tremor signals is necessary,” he said, “before mid- to short-term earthquake forecasting become reliable.”

原始論文：Kevin Chao, Zhigang Peng, Ya-Ju Hsu, Kazushige Obara, Chunquan Wu, Kuo-En Ching, Suzan van der Lee, Hsin-Chieh Pu, Peih-Lin Leu, Aaron Wech. Temporal variation of tectonic tremor activity in southern Taiwan around the 2010 M L 6.4 Jiashian earthquake. Journal of Geophysical Research: Solid Earth, 2017; 122 (7): 5417 DOI: 10.1002/2016JB013925

引用自：Northwestern University. "Do earthquakes have a 'tell'? Data scientists and seismologists use 'deep tremor' to forecast strong earthquakes." 

地球生命的基石或許是由隕石帶來的

原文網址：https://www.sciencedaily.com/releases/2017/10/171002161248.htm

地球生命的基石或許是由隕石帶來的

By Wade Hemsworth

美國麥克馬斯特大學和德國馬克斯普朗克研究所的科學家表示，在37億年至45億年前生命必需的物質從隕石噴濺到許多溫暖的小池塘並溶解之後，於其中某處誕生了生命。

他們的計算結果顯示在富含養分的生命原湯中反覆出現的乾燥與濕潤環境，使得池塘中做為生命基石的基本分子鍵結成可以自我複製的RNA分子，構成了地球上第一組含有生命訊息的基因密碼。

研究人員從天文物理、地質、化學、生物和其他各領域的角度進行詳盡的研究和計算而得出此結論。雖然「溫暖的小池塘」的概念從達爾文那時就已經問世，研究人員如今才透過大量基於實證的計算證明其可行性。

Ben K.D. Pearce和Ralph Pudritz是這篇論文的主要作者，兩位皆任職於美國麥克馬斯特大學的起源研究所和天文物理系。他們表示現有證據顯示生命出現時地球仍在成形階段，當時陸地才剛從海面升起；隕石不斷轟炸地球，其中有些承裝著生命基石；可以過濾太陽紫外線的臭氧層保護罩也還沒有出現。

「之前從未有人真的去進行這些計算。」Pearce表示，「這是個相當宏大的起頭。我們對此感到十分興奮。」

Pudritz表示：「由於這項計算要輸入來自許多不同領域的大量數據，因此可以將所有資訊全部統籌起來實在非常驚人。過程中的每一步都自然而然地銜接到下一步。最終，它們結合起來呈現的是單獨一幅清晰的圖像，代表結果必有幾分真實。」

這項研究今日刊登於《美國國家科學院院刊》(Proceedings of the National Academy of Science)，合作研究人員包括了德國馬克斯普朗克天文研究所的Dmitry Semenov和Thomas Henning。

「要瞭解生命是如何開始，就要先瞭解地球在數十億年前是什麼樣子。如同我們研究顯示的，天文學提供了解答中很重要的一部份：太陽系形成過程中的細節會直接影響地球生命的起源。」其中一位共同作者，馬克斯普朗克天文研究所的Thomas Henning表示。

作者說生命的火苗點燃於RNA聚合物誕生的時刻。形成核苷酸的必要成分由隕石攜帶至這些池塘，而池水因為反覆地降雨、蒸發和流乾來回升降，使得這些成分的濃度提升到足以鍵結在一起的地步。論文表示乾燥與濕潤環境的結合，是發生鍵結的必要條件。

研究人員相信在部分案例中，某些分子鏈具備適合條件使得它們可以摺疊，並且從環境中吸引其他核苷酸而發生自發性複製，讓它們滿足了生命定義的其中一個條件。雖然這些聚合物還不算完美，但它們可以透過達爾文式的演化來逐漸進步，而這又滿足了另一項條件。

Pearce表示：「這是有關生命起源的實驗化學的聖杯。」

這種原始生命型式最終會發展出DNA。直到DNA演化出來以前，世界上僅有以RNA為基礎的生命。要到許久之後才會演化出以DNA作為基因藍圖的較高等生命。

「DNA太過複雜而無法成為第一種出現的生命型態。」Pudritz表示，「生命必須要以別的樣子開始，那就是RNA。」

研究人員的計算結果顯示在數以千計的池塘中都具有生命形成的必須條件，而關鍵合成過程所需的要件在其中一座池塘通通達成的可能性比在熱液噴泉大上許多。熱液噴泉是目前最具競爭力的理論認為生命出現的地方，其認為在海床熱液翻騰的裂隙當中，構成生命的元素在洶湧的熱水裡結合而成。作者在他們的新論文中表示熱泉不可能是生命誕生的環境，因為要讓RNA形成必備的鍵結作用，需要反覆出現的乾燥與濕潤環境。

計算結果也排除了形成生命的核苷酸來自宇宙塵的可能性。雖然這些塵埃確實會攜帶對的物質，但研究人員確定它們散落至地表的量不足以到達形成生命所需的濃度。在太陽系生命的早期，那時候的小行星遠比現在更加常見，它們可能會落到這數以千計的小池塘中，把生命的基石運送進來。

Pearce和Pudritz計畫於明年麥克馬斯特大學的生命起源實驗室開始運作時，將他們的理論付諸實驗，在此他們可以於密封環境下重現生命出現以前的地球環境。

Pudritz表示：「我們感到十分振奮可以將所有線索結合起來完成一篇理論論文，而對我們在實驗室能進行的工作提供清晰的預測與明確的想法。」

Meteorites may have brought building blocks of life to Earth

Life on Earth began somewhere between 3.7 and 4.5 billion years ago, after meteorites splashed down and leached essential elements into warm little ponds, say scientists at McMaster University and the Max Planck Institute in Germany.

Their calculations suggest that wet and dry cycles bonded basic molecular building blocks in the ponds’ nutrient-rich broth into self-replicating RNA molecules that constituted the first genetic code for life on the planet.

The researchers base their conclusion on exhaustive research and calculations drawing in aspects of astrophysics, geology, chemistry, biology and other disciplines. Though the “warm little ponds” concept has been around since Darwin, the researchers have now proven its plausibility through numerous evidence-based calculations.

Lead authors Ben K.D. Pearce and Ralph Pudritz, both of the McMaster’s Origins Institute and its Department of Physics and Astronomy, say available evidence suggests that life began when the Earth was still taking shape, with continents emerging from the oceans, meteorites pelting the planet – including those bearing the building blocks of life – and no protective ozone to filter the Sun’s ultraviolet rays.

“No one’s actually run the calculation before,” says Pearce. “This is a pretty big beginning. It’s pretty exciting.”

“Because there are so many inputs from so many different fields, it’s kind of amazing that it all hangs together,” Pudritz says. “Each step led very naturally to the next. To have them all lead to a clear picture in the end is saying there’s something right about this.”

Their work, with collaborators Dmitry Semenov and Thomas Henning of the Max Planck Institute for Astronomy, has been published today in the Proceedings of the National Academy of Science.

 “In order to understand the origin of life, we need to understand Earth as it was billions of years ago.  As our study shows, astronomy provide a vital part of the answer.  The details of how our solar system formed have direct consequences for the origin of life on Earth,” says Thomas Henning, from the Max Planck Institute for Astronomy and another co-author.

The spark of life, the authors say, was the creation of RNA polymers: the essential components of nucleotides, delivered by meteorites, reaching sufficient concentrations in pond water and bonding together as water levels fell and rose through cycles of precipitation, evaporation and drainage. The combination of wet and dry conditions was necessary for bonding, the paper says.

In some cases, the researchers believe, favorable conditions saw some of those chains fold over and spontaneously replicate themselves by drawing other nucleotides from their environment, fulfilling one condition for the definition of life. Those polymers were imperfect, capable of improving through Darwinian evolution, fulfilling the other condition.

“That’s the Holy Grail of experimental origins-of-life chemistry,” says Pearce.

That rudimentary form of life would give rise to the eventual development of DNA, the genetic blueprint of higher forms of life, which would evolve much later. The world would have been inhabited only by RNA-based life until DNA evolved.

“DNA is too complex to have been the first aspect of life to emerge,” Pudritz says. “It had to start with something else, and that is RNA.”

The researchers’ calculations show that the necessary conditions were present in thousands of ponds, and that the key combinations for the formation of life were far more likely to have come together in such ponds than in hydrothermal vents, where the leading rival theory holds that life began in roiling fissures in ocean floors, where the elements of life came together in blasts of heated water. The authors of the new paper say such conditions were unlikely to generate life, since the bonding required to form RNA needs both wet and dry cycles.

The calculations also appear to eliminate space dust as the source of life-generating nucleotides. Though such dust did indeed carry the right materials, it did not deposit them in sufficient concentration to generate life, the researchers have determined. At the time, early in the life of the solar system, meteorites were far more common, and could have landed in thousands of ponds, carrying the building blocks of life.

Pearce and Pudritz plan to put the theory to the test next year, when McMaster opens its Origins of Life laboratory that will re-create the pre-life conditions in a sealed environment.

“We’re thrilled that we can put together a theoretical paper that combines all these threads, makes clear predictions and offers clear ideas that we can take to the laboratory,” Pudritz says.

原始論文：Ben K. D. Pearce, Ralph E. Pudritz, Dmitry A. Semenov, Thomas K. Henning. Origin of the RNA world: The fate of nucleobases in warm little ponds. Proceedings of the National Academy of Sciences, 2017; 201710339 DOI: 10.1073/pnas.1710339114

引用自：McMaster University. "Did life on Earth start due to meteorites splashing into warm little ponds?." 

科學家發現2億5000萬年前的滅絕事件是由西伯利亞火山爆發造成的證據

原文網址：http://www.nyu.edu/about/news-publications/news/2017/october/scientists-find-evidence-that-siberian-volcanic-eruptions-caused.html

科學家發現2億5000萬年前的滅絕事件是由西伯利亞火山爆發造成的證據

二疊紀大滅絕事件發生於大約2億5000萬年前。一組科學家團隊發現新證據顯示原因為現今西伯利亞地區發生大規模火山爆發，而導致嚴重的氣候變遷。

刊登於期刊《科學報告》(Scientific Reports)的這篇研究，發現在滅絕當時鎳元素的含量在全球都出現了高峰。異常多的鎳很有可能是來自同一時間在現今西伯利亞地區發生的大型火山噴發所釋放出來的噴氣(emanations)。研究人員表示噴發事件跟富含鎳的岩漿入侵體有關，這些由岩漿冷卻而形成的岩石含有某些地球上規模最大的鎳礦礦床。

研究人員利用感應耦合電漿質譜分析儀以原子層級測量稀有元素的豐度，結果證明二疊紀大滅絕事件時從南極到印度各地區都有出現鎳的異常高值，如此廣泛的分布顯示此現象在全世界都有出現。

從滅絕當時的鎳足跡得出的新證據，使科學家相信西伯利亞火山的劇烈活動造成嚴重全球暖化和其他環境變遷，使得超過90%的物種就此消失。

「西伯利亞的火山爆發，以及連帶發生大量進入地殼、富含鎳的岩漿入侵體，顯然將富含鎳的氣體釋放到大氣當中並散布至全球。」此篇論文的第一作者，紐約大學的地質學家Michael Rampino解釋。「於此同時，岩漿跟之前形成的煤炭礦床發生劇烈反應，釋放出二氧化碳和甲烷兩種溫室氣體。這可以解釋為什麼在大滅絕發生的時候，可以在海洋和陸地看到呈現強烈全球暖化的紀錄。海洋暖化使得它的流動變得相當遲緩，造成溶氧量降低，許多種類的海洋生物因而滅絕。」

「這項新發現給出進一步證據顯示地球經歷過的最嚴重滅絕事件，其導火線就是西伯利亞玄武岩噴發。此外，它對我們也有重大啟發。」此篇論文的共同作者，巴納德學院環境科學系的講師Sedelia Rodriguez表示，「我們期望將我們對於鎳和其他元素進行的研究範圍更加擴大，以精確描繪出此噴發事件的影響地區。我們冀望藉此可以更加瞭解噴發事件對陸上和海洋生物造成了何種影響而引發大滅絕。此外，我們也盼望這項研究可以幫助科學家確立未來是否有可能發生另一次此等規模的事件。」

Scientists Find Evidence that Siberian Volcanic Eruptions Caused Extinction 250 Million Years Ago

A team of scientists has found new evidence that the Great Permian Extinction, which occurred approximately 250 million years ago, was caused by massive volcanic eruptions that led to significant environmental changes.

The study, which appears in the journal Scientific Reports, reports a global spike in the chemical element nickel at the time of extinction. The anomalous nickel most likely came from emanations related to the concurrent huge volcanic eruptions in what is now Siberia. These eruptions, the researchers say, are associated with nickel-rich magmatic intrusions—rocks formed from the cooling of magma—that contain some of the greatest deposits of nickel ore on the planet.

Using an Inductively Coupled Plasma Mass Spectrometer, which measures the abundance of rare elements at their atomic level, the scientists documented anomalous peaks of nickel in regions ranging from the Arctic to India at the time of the Great Permian Extinction—distributions that suggest these nickel anomalies were a worldwide phenomenon.

This new evidence of a nickel fingerprint at the time of the extinctions convinced the scientists that it was the volcanic upheaval in Siberia that produced intense global warming and other environmental changes that led to the disappearance of more than 90 percent of all species.

“The Siberian volcanic eruptions and related massive intrusions of nickel-rich magmas into the Earth’s crust apparently emitted nickel-rich volatiles into the atmosphere, where they were distributed globally,” explains New York University geologist Michael Rampino, the paper’s senior author. “At the same time, explosive interactions of the magma with older coal deposits could have released large amounts of carbon dioxide and methane, two greenhouse gases, which would explain the intense global warming recorded in the oceans and on land at the time of the mass extinctions. The warm oceans also became sluggish and depleted in dissolved oxygen, contributing to the extinction of many forms of life in the sea”.

“This new finding, which contributes further evidence that the Siberian Trap eruptions were the catalyst for the most extensive extinction event Earth has ever endured, has exciting implications,” says Sedelia Rodriguez, a co-author of the paper and lecturer in the department of Environmental Science at Barnard College. “We look forward to expanding our research on nickel and other elements to delineate the specific areas affected by this eruption. In doing so, we hope to learn more about how these events trigger massive extinctions that affect both land and marine animals. Additionally, we hope this research will contribute to determining whether an event of this magnitude is possible in the future.”

原始論文；Michael R. Rampino, Sedelia Rodriguez, Eva Baransky, Yue Cai. Global nickel anomaly links Siberian Traps eruptions and the latest Permian mass extinction. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-12759-9

引用自：New York University. "Siberian volcanic eruptions caused extinction 250 million years ago, new evidence shows."