地球早期也許十分寒冷

原始網址：www.sciencedaily.com/releases/2016/03/160317144620.htm

Early Earth may have been ice cold

地球早期也許十分寒冷

When Earth's first organisms were formed, it may have been in an ice cold ocean. New research, published in Science Advances, indicates that both land and ocean were much colder than previously believed.

地球最初的生命也許誕生在一座冰冷的海洋當中。刊登在《科學前緣》(Science Advances)的新研究指出，也許當時的陸地和海洋都較先前認為的要寒冷許多。

Many researchers believe that Earth's early oceans were very hot, reaching 80° Celsius, and that life originated in these conditions. New findings may prove the opposite to be true. Harald Furnes, Professor Emeritus at the Department of Earth Science, has analysed volcanic and sedimentary rocks in the Barberton Greenstone Belt, South Africa. The volcanic rocks were deposited at depths of 2 to 4 kilometres.

許多研究人員認為早期地球的海洋十分滾燙，溫度可達攝氏80度，而生命就在這種環境條件下誕生。新研究或許證明了相反的論述才是正確的。卑爾根大學地球科學系的榮譽教授 Harald Furnes分析了南非 Barberton綠岩帶的火山岩與沉積岩而得到了這項結論。這些火山岩的沉積深度為水深2至4公里處。

"We have found evidence that the climate 3.5 billion years ago was a cold environment," says Furnes.

「我們找到了証據指出35億年前的氣候環境十分寒冷。」 Furnes說。

Along with Professor Maarten de Wit from Nelson Mandela Metropolitan University, South Africa, Furnes has published the results in the journal Science Advances.

Furnes和納爾遜曼德拉都市大學的Maarten de Wit教授將他們的合作成果刊登於期刊《科學前緣》。

A cold globe

酷寒星球

The rocks analysed by Furnes and de Wit were formed at latitudes comparable with that of the Canary Islands. Some of the sedimentary rocks associated with the volcanic rocks, show a remarkable resemblance to those known from more recent ice ages.

Furnes和de Wit分析的岩石形成緯度位置大致與現今的加那利群島(北緯30度左右)相當。其中一些伴隨火山岩的沉積岩與在較為近代的冰河期形成的岩石之間有驚人的相似性。

"This may indicate that Earth, 3.5 billion years ago, experienced an extensive, perhaps global, ice age," Furnes says.

「這或許意味著35億年前冰河曾經十分廣布，甚至全球皆進入了冰河期。」 Furnes說。

Past ocean temperatures are measured by analysing the relations between oxygen isotopes in rocks known as "chert," a rock composed of pure silicium-oxide. These South African rocks have been exposed to high temperatures. Even so, this is related to hydrothermal activity, or springs of extremely hot water, pumped from the ocean bed.

分析一種幾乎由純矽氧化物組成的岩石，即一般所稱的「燧石」(chert)中氧同位素之間的關係，可以得知過去海洋的溫度。結果顯示這些南非的岩石曾經位處高溫環境。然而這跟從海床上湧出的熱泉活動，也就是溫泉或著極高溫的水有關。

Similar to present climate

與現在的氣候雷同

Additionally, the researchers found more proof indicating that these rocks had been exposed to cold water. By examining finely grained sedimentary rocks (originally a claylike mud), that exists along with the deep-submarine volcanic rocks, the researchers found gypsum. Gypsum is produced under high pressure and at very cold temperatures, as in the present deep ocean.

除此之外，研究人員發現了更多證據顯示這些岩石曾位處冷水當中。研究人員檢驗了跟深海火山岩並存的細顆粒沉積岩(原先為黏土狀的泥土)，發現其中有石膏。石膏生成於高壓低溫的環境中，譬如說現在的深海。

"In other words, we have found independant lines of evidence that the climate conditions at this time may have been quite similar to the conditions we have today," says Furnes.

「換言之，我們發現了數條獨立線索指出當時的氣候條件也許跟現在我們可見的環境十分相似。」 Furnes說。

Furnes thinks some researchers may have difficulties accepting the new knowledge of an early, cold Earth. A paradigm shift in Earth Science is not to be expected, but he thinks the climate of the early earth will be seen in a new light.

Furnes認為部分研究人員也許很難信服這個冰冷的早期地球的新學說。他並不期待這會撼動地球科學的基本理論，但他認為未來要用全新的觀點來看待地球早期的氣候。

"I think that this will force research to go further," he says.

「我想這會促使未來的研究去更加深入探討。」他說。

引用自：University of Bergen. "Early Earth may have been ice cold." ScienceDaily. ScienceDaily, 17 March 2016.