Comprehensive coverage

Conditions for life were created already 4 billion years ago

Science / The oldest material on Earth reveals surprising findings

by Tamara Traubman

Scientists will present evidence today and claim that they have discovered the oldest material discovered so far - material that has been preserved almost since the creation of the earth. The analysis of the composition of the material shows that the primordial earth was quite different from what was thought until now, and that it already had continents and oceans 4.4 billion years ago - shortly after its formation. Until now it was common to assume that the crystallization of the continents and seas took place a few hundred million years later. The discovery also raises another interesting possibility: life originated much earlier than scientists had thought until now.

The Earth was formed almost 4.6 billion years ago, and according to the accepted opinion, until about 3.8 billion years ago its surface was very hot and there was a lot of volcanic activity. The analysis of the discovered material - a tiny grain of a mineral called zircon, which is often used to determine the geological age of rocks - provided scientists with a rare glimpse into a very early period in the Earth's history.

According to the analysis carried out by the researchers, led by Prof. Simon Wade from the Curtin University of Technology in Australia, the Earth was already cold enough 4.4 billion years ago for continents and oceans of flowing water to form on it, a necessary condition for the development of life. "Our data indicates that all of this happened much faster than anyone could have imagined," said Prof. John Walley, one of the partners in the study, in a telephone interview with "Haaretz" from his office at the University of Wisconsin. "We all always thought that the first billion years of the Earth were very different from the last billion years," he added, "Our surprise was when we saw,
that the processes we know very well from the modern Earth also took place on the very early Earth."

The research will be published today in the scientific journal "Nature". Along with it, another study is published, in which a zircon crystal was analyzed at a slightly younger age, and it also hints that at that time the temperature on the surface of the earth was low, and continents and conditions suitable for life began to form there.

"The results represent significant progress in reconstructing the darkness of the Earth's Mesozoic Ages," wrote Dr. Alex Holliday, in a commentary article that accompanied the publication of the studies. "The knowledge we had until now was only about 4.2 billion years ago," says geologist Dr. Dov Avigad from the Institute of Earth Sciences of the Hebrew University. "They found a rock here whose age is 150-100 million years older - it is already very close to the age of the Earth's formation."

The zircon was discovered in Western Australia. After the researchers found out its age, they tested isotopes (atoms whose weight changed due to a change in their nucleus) of oxygen present in it, which are widely used to reconstruct the conditions of formation of rocks. They also performed another test - analyzing the concentration of rare lead in the material. This test also constitutes a kind of fingerprint, which shows in what processes trend rocks (rocks that are melted under the earth's crust) developed.

By studying the isotope, the researchers discovered that the zircon was formed from magma originating from granite rock - a rock that exists only on land. The studied isotopes are also a unique sign that shows that the rock has interacted with water at low temperatures.

Scientists say that the research significantly extends the period during which conditions prevailed on the earth that allow the development of life, and therefore, raises the question of whether life developed earlier than previously thought - and if not, why did it take so long for them to develop (the fossils
The first ones that were discovered testify to primitive life forms that were created about 3.5 billion years ago).

According to Dr. Steven Mojazsis, who led the second team, the results of the studies raise the possibility that life even evolved and disappeared completely several times, as a result of fatal collisions of meteorites on Earth. "In fact," says Prof. Wally, "we know today that life can develop even at temperatures higher than one hundred degrees Celsius - as long as liquid water is present. Today it is becoming more and more clear that as soon as liquid water appears on the surface of the earth - life develops quite quickly. Our sample provides no evidence for this, but it is not necessary that a long time passed before life formed. They could have been created before what we thought."
{Appeared in Haaretz newspaper, 11/1/2001}

Leave a Reply

Email will not be published. Required fields are marked *

This site uses Akismat to prevent spam messages. Click here to learn how your response data is processed.

Science website logo