Ancient Earth Had More Oxygen than Scientists Thought
Researchers say the Earth had much more oxygen nearly a billion years ago than scientific experts thought. That claim could change theories about how life developed on our planet.
The claim came from researchers at Brock University in Canada. They wanted to measure the levels of oxygen in the Earth's atmosphere nearly a billion years ago. To do this, the researchers developed a way to study small air bubbles trapped in ancient salt crystals.
"There was a lot of debate as to what the oxygen content was 800 million or more years ago," said Nigel Blamey of Brock University's Department of Earth Sciences. He said the trapped gasses showed that the oxygen level was about half of what it is today.
In fact, many experts believed that the oxygen level was only about two percent of the atmosphere so long ago. But the new study found that it was almost 11 percent. Currently, oxygen is about 21 percent of the atmosphere.
The Canadian researchers used a method to study air bubbles trapped in halite, the natural form of table salt.
The researchers say their findings have major effects for theories about how and when life developed.
Professor of Earth Sciences Uwe Brand said that higher oxygen levels in the past may turn back the clock when complex life developed. "Now paleobiologists will have reason to go looking for rocks with" evidence of these first evolutionary steps," he told the Canadian Broadcasting Corporation.
I'm Anne Ball.
1.oxygen level ph.氧气含量
Scientists are not certain why the oxygen level dropped.
2.Earth's atmosphere ph.地球大气层
The spacecraft burned up when it re-entered the earth's atmosphere.
3.air bubbles ph.气泡
Ink particles attach themselves to air bubbles and rise to the surface.
4.looking for ph.寻找
He loafed about the street looking for something to do.
1.The Canadian researchers used a method to study air bubbles trapped in halite, the natural form of table salt.
table salt 食盐
Could you bring me the table salt?
Sodium chloride is the chemical term for table salt.
2.Professor of Earth Sciences Uwe Brand said that higher oxygen levels in the past may turn back the clock when complex life developed.
turn back 阻挡；往回走
They were very nearly forced to turn back.
She turned back towards the crossroads.
这一结论是由加拿大布鲁克大学的研究人员提出的 。他们试图测量约10亿年前地球大气层的氧含量 。为此，研究人员发明了一种办法来研究古盐结晶中夹带的小气泡 。
布鲁克大学地球科学系的奈杰尔·布兰梅（Nigel Blamey）称，“关于8到10亿年前的氧含量的议题存在大量争议 。”他表示，夹带的气泡表明当时的氧含量约为现在的一半 。
其实，很多专家认为远古时期的氧含量约占到大气的2% 。但这项新研究发现氧气所占比例为11% 。目前大气中的氧气含量约21% 。
加拿大研究人员借助一种办法来研究岩盐中夹带的气泡 。岩盐是食盐的自然形态 。
地球科学系教授乌韦·布兰恩德（Uwe Brand）表示，过去的氧含量更高可以让复杂生命起源的时间提前 。接受加拿大广播公司采访时他表示，“现在，古生物学家有充分的理由在岩石中寻找生命进化的第一手证据 。”