在格陵蘭和南極的冰層中發現超級太陽風暴留下的痕跡

原文網址：www.sciencedaily.com/releases/2015/10/151026112106.htm

Traces of enormous solar storms in the ice of Greenland and Antarctica

在格陵蘭和南極的冰層中發現超級太陽風暴留下的痕跡

Solar storms and the particles they release result in spectacular phenomena such as auroras, but they can also pose a serious risk to our society. In extreme cases they have caused major power outages, and they could also lead to breakdowns of satellites and communication systems. According to a study published today in Nature Communications, solar storms could be much more powerful than previously assumed. Researchers at Lund University in Sweden have now confirmed that Earth was hit by two extreme solar storms more than 1,000 years ago.

太陽風暴和其拋射的粒子會造成像是極光的奇景，但它們對我們的社會也可能是相當大的潛在風險。在最極端的例子中，它們曾經造成大停電，並損壞衛星而造成通訊系統中斷。根據本日(10/15)發表於《自然通訊》(Nature Communications)的研究，太陽風暴可達到的規模比之前預估的還要高上許多。瑞典隆德大學的研究人員現在證明出1000年以前曾有兩次超級太陽風暴襲擊地球。

"If such enormous solar storms would hit Earth today, they could have devastating effects on our power supply, satellites and communication systems," says Raimund Muscheler at the Department of Geology, Lund University.

「若今日有如此巨大的太陽風暴襲擊地球，可能會對我們的電力供應、人造衛星和通訊系統有毀滅性的影響。」隆德大學地質科學系的Raimund Muscheler說。

A team of researchers at Lund University, together with colleagues at Uppsala University in Sweden, as well as researchers in Switzerland, Denmark and the US, have been looking for traces of solar storms in ice cores from Greenland and Antarctica. Everywhere on Earth you can find traces of cosmic rays from the Galaxy and the sun, such as low levels of radioactive carbon.

隆德大學的研究團隊，協同來自瑞典烏普薩拉大學以及瑞士、丹麥和美國的研究人員，從採自格陵蘭和南極的冰芯中尋找太陽風暴留下來的蛛絲馬跡。在地球各處皆能發現這類由銀河系和太陽產生的宇宙射線遺留下來的線索，比方微量放射性碳元素。

A few years ago researchers found traces of a rapid increase of radioactive carbon in tree rings from the periods AD 774/775 and AD 993/994. The cause for these increases was, however, debated.

在數年前研究人員曾在樹輪記錄中發現放射性碳元素在西元前774/775年，和西元前993/994年有突然暴增的現象，但當時對此遽增現象的成因並無定論。

"In this study we have aimed to work systematically to find the cause for these events. We have now found corresponding increases for exactly the same periods in ice cores. With these new results it is possible to rule out all other suggested explanations, and thereby confirm extreme solar storms as the cause of these mysterious radiocarbon increases," says Raimund Muscheler.

「本研究中我們有系統得分析以找出這些事件的成因。現在我們發現冰芯中的增加事件也剛好對應到同樣的時間點。有了這些新結果，我們便可以排除所有其他的解釋，而能確認超級太陽風暴便是這幾起放射性碳元素神秘增加事件的元凶。」Raimund Muscheler說。

The study also provides the first reliable assessment of the particle fluxes connected to these events. Raimund Muscheler points out that this is very important for the future planning of reliable electronic systems:

這也是首次有研究確切預估關於這些事件的粒子通量。Raimund Muscheler指出在未來要設計完善的電路系統時此數據相當重要。

"These solar storms by far exceeded any known events observed by instrumental measurements on Earth. The findings should lead to a reassessment of the risks associated with solar storms," says Raimund Muscheler.

「這幾起太陽風暴遠遠超過了我們所知由地球儀器曾觀測到的事件。這些事件應能讓我們重新評估太陽風暴可能造成的風險。」Raimund Muscheler說。

引用自：Lund University. "Traces of enormous solar storms in the ice of Greenland and Antarctica." ScienceDaily. ScienceDaily, 26 October 2015. 

科學家找到了也許是地球生命出現的最早證據

Scientists may have found the earliest evidence of life on Earth

科學家找到了也許是地球生命出現的最早證據

When did life on Earth begin? Scientists have dug down through the geologic record, and the deeper they look, the more it seems that biology appeared early in our planet’s 4.5-billion-year history. So far, geologists have uncovered possible traces of life as far back as 3.8 billion years. Now, a controversial new study presents potential evidence that life arose 300 million years before that, during the mysterious period following Earth’s formation.

地球上的生命何時誕生？科學家長久以來不停地深堀地質記錄以期找到解答。隨著他們越加深入，生物在地球45億年的歷史上似乎顯得越早出現。目前為止，地質學家找到疑似由生命留下來的蹤跡可追溯至38億年前。現今，一則頗受爭議的新研究發表的證據顯示生命可能比這還要早3億年誕生—在那段地球甫形成，至今仍充滿謎團的時期。

The clues lie hidden in microscopic flecks of graphite—a carbon mineral—trapped inside a single large crystal of zircon. Zircons grow in magmas, often incorporating other minerals into their crystal structures of silicon, oxygen, and zirconium. And although they barely span the width of a human hair, zircons are nearly indestructible. They can outlast the rocks in which they initially formed, enduring multiple cycles of erosion and deposition.

這些線索隱藏在石墨(一種碳質礦物)的微小顆粒之中，而它們又被包覆在體積較大的鋯石(zircon)結晶裡面。在鋯石結晶於岩漿逐漸生長的過程中，常有其他礦物會被困在它由矽、氧、鋯組成的結晶構造內。雖然鋯石甚少成長至比人類毛髮還要寬的尺寸，但它幾乎是堅不可摧的。它們的壽命遠遠長過它們形成時所待的岩石，且經歷多次侵蝕沉積循環後仍能毫髮無傷。

In fact, although the oldest rocks on Earth date back only 4 billion years, researchers have found zircons up to 4.4 billion years old. These crystals provide a rare glimpse into the first chapter of Earth’s history, known as the Hadean eon. “They are pretty much our only physical samples of what was going on on the Earth before 4 billion years ago,” says Elizabeth Bell, a geochemist at the University of California, Los Angeles (UCLA), and lead author of the new study, published online today in the Proceedings of the National Academy of Sciences.

事實上，雖然現今地球上已知最古老岩石的年齡僅僅40億年，研究人員早已發現年代為44億年的鋯石顆粒。這些晶體讓我們有機會驚鴻一瞥地球歷史序章，科學家稱之為冥古宙時(Hadean eon)的樣貌。「或許能讓我們一窺地球40億年之前有何事物發生的實際樣品僅只如此。」加州大學洛杉磯分校(UCLA)的地球化學家Elizabeth Bell說，她是此篇發表在10/26《美國國家科學院院刊》(Proceedings of the National Academy of Sciences)的新研究的第一作者。

In the study, Bell and her colleagues examined zircons from the Jack Hills in Western Australia, a site that has yielded more Hadean samples than anywhere else on Earth, searching for inclusions of carbon minerals like diamonds and graphite. The mere presence of these minerals does not prove biology existed when the zircons formed, but it does provide the opportunity to look for chemical signs of life. The team eventually found small bits of potentially undisturbed graphite in one 4.1 billion-year-old crystal. The graphite has a low ratio of heavy to light carbon atoms—called isotopes—consistent with the isotopic signature of organic matter. “On Earth today, if you were looking at this carbon, you would say it was biogenic,” Bell says. “Of course, that’s more controversial for the Hadean.”

在此研究中，Bell和她的同僚檢視了來自澳洲西部Jack Hills的鋯石。於此地區發現的冥古宙樣品數量之多為世上首屈一指。他們的目標是尋找鋯石內的碳質礦物包裹體(inclusion)，像是石墨或鑽石。僅是出現這些礦物並不能證明鋯石形成當下有生物存在，但我們有機會能從中找到生命存在的蛛絲馬跡。研究團隊最終找到了一顆41億年前的鋯石，其中含有的微量石墨可能尚未受到汙染。這些石墨的碳原子較重和較輕者(同位素(isotope))之間的比例偏低，與有機物的碳同位素訊號相當一致。「如果今日在地球上看到帶有這種訊號的碳，你會說他來自生物體。」Bell說，「當然，在時空背景是冥古宙的情況下，爭議會大上許多。」

The authors list several nonbiological processes that could explain their findings, but they favor the idea that the graphite started out as organic matter in sediments that got dragged into the Earth’s mantle during the collision of tectonic plates. As the sediments melted to form magma, the elevated temperatures and pressures transformed the carbon into graphite, which eventually found its way into a zircon crystal.

作者雖然也有列出數種非生物作用或許能解釋他們的發現，但他們仍偏好這些石墨一開始是沉積物中的有機物，之後在板塊碰撞時被拖入地球地函中的說法。隨著沉積物慢慢熔融成岩漿，逐漸升高的溫度和壓力會把有機物轉變成石墨，最後被鋯石晶體囚禁於其中。

If this story is true, and life existed 4.1 billion years ago, Bell says that the new results would corroborate growing evidence of a more hospitable early Earth than scientists once imagined. “The traditional view of the Earth’s first few hundred million years was that this was a sterile, lifeless, hot planet that was constantly being bombarded by meteorites,” she says. But partly thanks to the wealth of information revealed by the Jack Hills zircons in recent years, scientists have come to see the early Earth as much milder and more amenable to life.

若此故事屬實，即代表了生命41億年前就已存在。Bell說這跟越來越多的證據結合起來，顯示了早期地球比科學家曾經認為的還要宜人。「傳統觀點認為地球在最初數億年是顆貧瘠、了無生氣、熾熱的星球，且時常被隕石雨轟炸。」她說，「然而，部分歸功於近幾年來Jack Hills鋯石提供的豐富資訊，科學家已經開始認為早期地球是處更溫和，且更適合生命成長的地方。」

“We know there was liquid water,” says Mark van Zuilen, a geomicrobiologist at the Paris Institute of Earth Physics. “There’s nothing that holds us back from assuming life was there.” However, van Zuilen and others say they’re not sure the new study provides compelling evidence that it was.

「我們知道那時候的地球有液態水。」Mark van Zuilen說，他是巴黎地球物理研究所的地質微生物學家。「沒有任何證據可以遏止我們推論當時生命已經存在。」然而，van Zuilen和其他人並不確定此篇新研究提出的證據具備足夠說服力，能夠證明生命已經出現。

Some of this circumspection has roots in recent history. In 2008, researchers announced that diamond-graphite inclusions in 4.3-billion-year-old zircons had potentially biological signatures, inspiring Bell and her team to start looking through UCLA’s own collection of Jack Hills crystals. But subsequent analysis showed the 2008 inclusions came from lab contamination, not early Earth. In the new study, the researchers took measures to prevent similar problems.

這樣慎重的態度其來有自。發生在最近的2008年，另一組研究人員聲稱他們在43億年前的鋯石中，發現的鑽石-石墨包裹體可能含有生物訊號。這也啟發了Bell和她的團隊開始仔細檢視UCLA擁有的Jack Hills結晶樣品。但隨後的分析結果顯示2008年的包裹體來自於實驗室汙染而非早期地球。因此在這項新研究中，研究人員採取許多措施來預防類似的問題發生。

“That one negative experience doesn’t mean nobody should try again,” says John Eiler, a geologist at the California Institute of Technology in Pasadena. “But let’s just say, I’m cautious.” For one, he says, researchers need to settle some important debates, like whether the inclusions in Hadean zircons truly preserve original material, or if they’ve been altered, for example, during a later bout of metamorphism. He also questions whether organic matter can survive in magma chambers long enough to form graphite, casting doubt on the proposed mechanism.

「一次失敗的經驗並非表示不應該有任何人再去嘗試。」John Eiler說，他是加州理工學院的地質學家。「但這麼說吧，對此我十分保留。」他說，身為一名研究人員必須提出一些重要的論點，比方說冥古宙鋯石中的包裹體是否真得保有原本的物質，或者他們其實已經被置換掉了，像是在形成之後的連串變質作用可能造成的結果。他同時也質疑作者提出的機制：有機物是否能在岩漿庫存活夠久而形成石墨。

Those issues aside, most scientists—including the authors—agree that the data do not yet exclude nonbiological explanations. Many abiotic processes can produce carbon with isotopic signatures similar to organic matter. For instance, the graphite could contain carbon from certain kinds of meteorites, which have light isotopic compositions. Alternatively, some invoke chemical processes, like the so-called Fischer-Tropsch reactions, in which carbon, oxygen, and hydrogen react with a catalyst like iron to form methane and other hydrocarbons. Such reactions probably occurred near hydrothermal vents in the Hadean, van Zuilen says, and can impart isotopic signatures that are indistinguishable from biological materials.

除了這些議題之外，大部分的科學家，包括作者本身也同意這些數據並不能完全排除非生物來源的解釋。許多非生物作用生成的碳可以與有機物有類似的同位素訊號。比如某些種類隕石中的石墨會含有較輕的碳同位素組成。另外也有人提出一些化學作用也會生成類似的產物，像是費雪－闕布希反應(Fischer-Tropsch reaction)，這是一種碳、氧、氫在環境中有鐵這類催化劑的情況下，生成甲烷和其他碳氫化合物的反應。van Zuilen說在冥古宙的熱泉附近可能會發生這類反應，它們產生的碳同位素訊號可能會無法與生物物質區分開來。

One way to settle the question that doesn’t rely on isotopes involves studying Mars, which, unlike Earth, still has rocks older than 4 billion years on its surface. “If we can find evidence for the existence of life on Mars at that time, then it will be easier to argue the case that it was also present on Earth,” says Alexander Nemchin, a geochemist at Curtin University in Bentley, Australia, and lead author of the 2008 study on diamond inclusions.

要解決這件問題而不依靠同位素的方法之一，便是研究火星上的岩石。因為火星與地球不同，它的表面仍然有許多年代超過40億年的岩石。「如果我們可以找到證據說明那時火星上有生命存在，那我們要證明地球也是如此便簡單的多。」澳洲科廷大學的地球化學家Alexander Nemchin說，他是2008年鑽石包裹體研究的第一作者。

For now, scientists must make do with zircons, the only materials that preserve any record—however cryptic—of the Hadean eon. Bell acknowledges the need to test her team’s hypothesis on additional samples. She says researchers must make a concerted effort to find more Hadean carbon in Jack Hills zircons and see if it too has potentially biological origins. “Hopefully we didn’t just chance on the one freak zircon that had graphite in it,” she says. “Hopefully there is actually a fair amount of it.”

目前科學家仍須仰賴鋯石來研究冥古宙。儘管是如此的難以解讀，它們畢竟是唯一保存並記錄當時資訊的物質。Bell坦承她的團隊仍須更多樣品來驗證他們的假說。她說研究人員必須要同心協力尋找更多包裹在Jack Hills鋯石中的碳，並且檢視它們是否有可能來自生物。「我希望我們找到一顆含有石墨的奇特鋯石並非偶然。」她說，「希望這樣的鋯石事實上為數眾多。」

原文網址：http://news.sciencemag.org/biology/2015/10/scientists-may-have-found-earliest-evidence-life-earth

原作者：Julia Rosen

地球在41億年前就已經有生命出現，較科學家之前認為的還要早了許多

原文網址：www.sciencedaily.com/releases/2015/10/151019154153.htm

Life on Earth likely started 4.1 billion years ago, much earlier than scientists thought

地球在41億年前就已經有生命出現，較科學家之前認為的還要早了許多

Evidence that early Earth was not dry and desolate

證據顯示早期地球並非乾燥的不毛之地

UCLA geochemists have found evidence that life likely existed on Earth at least 4.1 billion years ago -- 300 million years earlier than previous research suggested. The discovery indicates that life may have begun shortly after the planet formed 4.54 billion years ago.

加州大學洛杉磯分校的地球化學家發現的證據，顯示生命很可能早在41億年前便已經存在於地球，比前人研究認為的還要早了3億年。此發現象徵著45.4億年前，地球形成不久後生命就誕生了。

The research is published today in the online early edition of the journal Proceedings of the National Academy of Sciences.

這篇研究今日(2015.10.19)發表在線上的《美國國家科學院學報》早版(early edition of Proceedings of the National Academy of Sciences)。

"Twenty years ago, this would have been heretical; finding evidence of life 3.8 billion years ago was shocking," said Mark Harrison, co-author of the research and a professor of geochemistry at UCLA.

「如果是在20年前，這番言論也許會被斥為一派胡言。發現38億年前已有生命存活的證據確實相當令人震驚。」此研究的共同作者，加州大學洛杉磯分校的地球化學教授Mark Harrison說。

"Life on Earth may have started almost instantaneously," added Harrison, a member of the National Academy of Sciences. "With the right ingredients, life seems to form very quickly."

「生命可能與地球幾乎同時形成。」Harrison補充說，他也是一名美國國家科學院院士。「有了適當的原料，生命似乎很快便能從中誕生。」

The new research suggests that life existed prior to the massive bombardment of the inner solar system that formed the moon's large craters 3.9 billion years ago.

這項新研究認為生命在39億年前，形成月球眾多巨型隕石坑的內太陽系大轟炸事件之前就已存在。

"If all life on Earth died during this bombardment, which some scientists have argued, then life must have restarted quickly," said Patrick Boehnke, a co-author of the research and a graduate student in Harrison's laboratory.

「正如一些科學家提出的說法，若地球上所有生命都在大轟炸事件中死亡，那麼生命必然很快又東山再起。」共同作者，Harrison研究室的研究生Patrick Boehnke說。

Scientists had long believed the Earth was dry and desolate during that time period. Harrison's research -- including a 2008 study in Nature he co-authored with Craig Manning, a professor of geology and geochemistry at UCLA, and former UCLA graduate student Michelle Hopkins -- is proving otherwise.

科學家長久以來認為在那段時期，地球是一片乾旱的荒蕪之地。Harrison的研究，包括他在2008年與Craig Manning和Michelle Hopkins刊登於《自然》的共同著作，卻證明事實並非如此。Craig Manning 為加州大學洛杉磯分校的地質和地球化學教授；Michelle Hopkins則是之前就讀於同所大學的研究生。

"The early Earth certainly wasn't a hellish, dry, boiling planet; we see absolutely no evidence for that," Harrison said. "The planet was probably much more like it is today than previously thought."

「地球早年絕非是一座乾燥且熾熱的煉獄，我們並未看到任何證據可以支持此說法。」Harrison說。「也許在當時，這顆星球比我們先前認為的還要與目前更加相似。」

The researchers, led by Elizabeth Bell -- a postdoctoral scholar in Harrison's laboratory -- studied more than 10,000 zircons originally formed from molten rocks, or magmas, from Western Australia. Zircons are heavy, durable minerals related to the synthetic cubic zirconium used for imitation diamonds. They capture and preserve their immediate environment, meaning they can serve as time capsules.

此篇研究由Harrison實驗室的特約博士後研究員Elizabeth Bell領導。他們研究了產自澳洲西部，形成於熔化岩石，即岩漿中的一萬多顆鋯石(zircon)碎屑。鋯石是一種高密度且相當堅硬的礦物，與用來製作人造鑽石的人造立方氧化鋯相當類似。它們可以捕捉並且保存形成當時的環境資訊，意味著它們就像時光膠囊一般。

The scientists identified 656 zircons containing dark specks that could be revealing and closely analyzed 79 of them with Raman spectroscopy, a technique that shows the molecular and chemical structure of ancient microorganisms in three dimensions.

科學家發現其中的656顆鋯石碎屑含有暗色微粒，在這之中有79顆鋯石的微粒可以用拉曼光譜(Raman spectroscopy)來檢視並詳細分析。拉曼光譜是一種可以檢視古代微生物的分子和化學三維構造的技術。

Bell and Boehnke, who have pioneered chemical and mineralogical tests to determine the condition of ancient zircons, were searching for carbon, the key component for life.

Bell和Boehnke率先使用化學和礦物試驗來確認這些遠古鋯石形成時的環境，它們的目標是尋找形成生物的關鍵成分--碳。

One of the 79 zircons contained graphite -- pure carbon -- in two locations.

在79顆鋯石中，有一顆鋯石內的兩處有石墨分佈，這是一種純碳。

"The first time that the graphite ever got exposed in the last 4.1 billion years is when Beth Ann and Patrick made the measurements this year," Harrison said.

「今年Beth Ann與Patrick進行測量時，首度發現在41億年前石墨就已經出現了。」Harrison說。

How confident are they that their zircon represents 4.1 billion-year-old graphite?

他們對他們的鋯石真的含有形成於41億年前的石墨有多少信心？

"Very confident," Harrison said. "There is no better case of a primary inclusion in a mineral ever documented, and nobody has offered a plausible alternative explanation for graphite of non-biological origin into a zircon."

「我們相當有信心。」Harrison說。「有關礦物原始包裹體(primary inclusion)的文獻中沒有比這更佳的案例，而且也沒有人提出其他可信說法能解釋鋯石裡的石墨其實是非生物來源。」

The graphite is older than the zircon containing it, the researchers said. They know the zircon is 4.1 billion years old, based on its ratio of uranium to lead; they don't know how much older the graphite is.

研究人員說石墨比包覆它的鋯石還要古老。藉由測量鋯石中鈾跟鉛的比例，他們得知鋯石的年代為41億年，但他們並無法確知石墨究竟有多老。

The research suggests life in the universe could be abundant, Harrison said. On Earth, simple life appears to have formed quickly, but it likely took many millions of years for very simple life to evolve the ability to photosynthesize.

Harrison說此研究顯示了生命可能存活在宇宙各處。地球上簡單生命可能出現得相當迅速，然而，生命要從十分簡當演化成能夠行使光合作用，可能得耗費數百萬年的時間。

The carbon contained in the zircon has a characteristic signature -- a specific ratio of carbon-12 to carbon-13 -- that indicates the presence of photosynthetic life.

鋯石裡的碳其碳-12與碳-13之間具有獨特比例，而這種特殊訊號指示出能進行光合作用的生命已然出現。

"We need to think differently about the early Earth," Bell said.

「我們需要以不同的眼光看待早期地球。」Bell說。

Wendy Mao, an associate professor of geological sciences and photon science at Stanford University, is the other co-author of the research.

此研究的另一位共同作者Wendy Mao是史丹佛大學地質科學與光子科學系的副教授。

The research was funded by the National Science Foundation and a Simons Collaboration on the Origin of Life Postdoctoral Fellowship granted to Bell.

Bell的這項博士後研究由西蒙斯基金會的生命起源合作計畫授予，並由國家科學基金會資助。

引用自：University of California - Los Angeles. "Life on Earth likely started 4.1 billion years ago, much earlier than scientists thought: Evidence that early Earth was not dry and desolate." ScienceDaily. ScienceDaily, 19 October 2015. 

地球內核形成於10至15億年前

原文網址：www.sciencedaily.com/releases/2015/10/151007135656.htm

Earth's inner core was formed 1-1.5 billion years ago

地球內核形成於10至15億年前

There have been many estimates for when the earth's inner core was formed, but scientists from the University of Liverpool have used new data which indicates that the Earth's inner core was formed 1 -- 1.5 billion years ago as it "froze" from the surrounding molten iron outer core.

過往對於地球內核何時形成有許多的猜測。近日，利物浦大學的科學家利用新證據推測地球的內核約在10至15億年前，從周遭的鐵質液態外核中「冷卻」而生。

The inner core is Earth's deepest layer. It is a ball of solid iron just larger than Pluto which is surrounded by a liquid outer core. The inner core is a relatively recent addition to our planet and establishing when it was formed is a topic of vigorous scientific debate with estimates ranging from 0.5 billion to 2 billion years ago.

內核在地球的分層構造中是最深的一層，為一顆比冥王星略大的固體鐵球，被液態的外核環繞。相較其它構造，內核加入地球是起較近代的事件，而確認它的形成時間也是一件討論十分熱烈的科學議題。過往科學家對此時間的預估從5億至20億年前不等。

In a new study published in Nature, researchers from the University's School of Environmental Sciences analysed magnetic records from ancient igneous rocks and found that there was a sharp increase in the strength of the Earth's magnetic field between 1 and 1.5 billion years ago.

在發表於《自然》的新研究中，利物浦大學環境科學院的研究人員分析了古代火成岩中的地磁記錄，並發現在10到15億年前地球磁場強度有突然上升的現象。

This increased magnetic field is a likely indication of the first occurrence of solid iron at Earth's centre and the point in Earth's history at which the solid inner core first started to "freeze" out from the cooling molten outer core.

劇烈上升的磁場強度可能代表在地球中心有第一塊固體鐵產生，而象徵著在地球歷史上，逐漸冷卻的外核開始「冷卻」出固態內核的時刻。

Liverpool palaeomagnetism expert and the study's lead author, Dr Andy Biggin, said: "This finding could change our understanding of the Earth's interior and its history."

利物浦大學的古地磁專家，也是本研究的第一作者Andy Biggin博士說：「這項發現有可能會改變我們對地球內部與其歷史的認知。」

"The timing of the first appearance of solid iron or "nucleation" of the inner core is highly controversial but is crucial for determining the properties and history of the Earth's interior and has strong implications for how the Earth's magnetic field -- which acts as a shield against harmful radiation from the sun, as well as a useful navigational aid -- is generated.

「內核的固態鐵首次出現，或「成核」(nucleation)的時間是件備受爭議的議題，它對瞭解地球內部的性質和歷史來說相當重要。而地磁作為可以抵擋來自太陽的有害輻射的屏障，同時也是指引航道的利器，在探討地磁是如何產生的這一方面，它也具有相當重大的意義。」

"The results suggest that the Earth's core is cooling down less quickly than previously thought which has implications for the whole of Earth Sciences. It also suggests an average growth rate of the solid inner core of approximately 1mm per year which affects our understanding of the Earth's magnetic field."

「結果顯示地核的冷卻速率較之前認為的還要慢，這對整個地球科學界有相當重要的啟發。另外結果也指出固態內核成長的平均速率約為每年1mm，而影響我們對地磁的理解。」

The Earth's magnetic field is generated by the motion of the liquid iron alloy in the outer core, approximately 3,000 km beneath the Earth's crust. These motions occur because the core is losing heat to the overlying solid mantle that extends up to the crust on which we live producing the phenomenon of convection.

地磁是由於在地殼下約3000公里處，外核中的液態鐵合金運動而產生。會產生這種運動則是由於地核會向覆蓋於上方的地函散熱，而導致對流現象。地函的延伸範圍為地核至我們所居住的地殼之下。

Once the inner core started to freeze, this convection received a strong boost in power because light, non-metallic elements remained molten in the outer core and were buoyant relative to the overlying liquid. The process continues today and is thought to be the main source of "fuel" for generating the Earth's magnetic field.

一旦內核開始凝結而成，便會產生更強的能量推動這種對流效應，因為較輕盈的非鐵質元素會殘留在融化的外核中，相較於周遭的液體會往上浮動。這種過程在今日仍持續著，並被視為地球磁場的主要「燃料」來源。

Dr Biggin added: "The theoretical model which best fits our data indicates that the core is losing heat more slowly than at any point in the last 4.5 billion years and that this flow of energy should keep the Earth's magnetic field going for another billion years or more.

Biggin博士附加說明：「最符合我們數據的理論模型指出在45億年來的任何時刻，地核流失熱量的速度都比過往認為的還要慢，而此能量流動應該還能繼續支持地球磁場至下一個10億年或是更久。」

"This contrasts sharply with Mars which had a strong magnetic field early in its history which then appears to have died after half a billion years."

「這跟火星是強烈的對比。火星在它的行星歷史早期擁有強烈的磁場，但似乎僅維持了五億年就嘎然而止。」

The study, published in the journal Nature, is a collaboration between scientists at the Universities of Liverpool, Helsinki, Michigan Tech, UC San Diego, and the Chinese Academy of Sciences.

此篇發表於期刊《自然》的研究為利物浦大學、赫爾辛基大學、密西根理工大學、加州大學聖地牙哥分校和中國科學院的科學家之間的合作成果。

引用自：University of Liverpool. "Earth's inner core was formed 1-1.5 billion years ago." ScienceDaily. ScienceDaily, 7 October 2015.