The finding is the first concrete validation of a long-held hypothesis that oxygen was being produced and consumed by that time and that the transition to an oxygenated atmosphere was long term. The results are published in the on-line early edition of the Proceedings of the National Academy of Science, to appear the week of October 16th.
It is generally believed that before 2.4 billion years ago, Earth's atmosphere was essentially devoid of oxygen. Exactly when and how oxygen-producing photosynthesis evolved and began fueling the atmosphere with the gas that much of life depends on has been hotly debated for some time. Plants, algae, and cyanobacteria (blue-green algae) emit oxygen as a waste product of photosynthesis--the process by which sugar, essential for nutrition, is made from light, water, and carbon dioxide.
"Our evidence points to the likelihood that Earth was peppered with small 'oases' of shallow-water, oxygen-producing, photosynthetic microbes around 2.7 billion years ago," stated lead author Jennifer Eigenbrode of Carnegie's Geophysical Laboratory, who collected the data while pursuing her Ph.D. at Penn State. "Over time these oases must have expanded, eventually enriching the atmosphere with oxygen. Our data record this transition."
The researchers discovered changes in fossil isotopes of the life-essential element carbon in a 150 million-year section of rock that included shallow and deepwater sediments from the late Archean period (the Archean lasted from 3.8 to 2.5 billion years ago) in Hamersley Province in Western Australia. Isotopes are different forms of an element's atoms. The relative proportions of carbon and other isotopes in organic matter depend on chemical reactions that happen as the carbon wends its way through an organism's metabolism. There are two stable isotopes of carbon found in nature--12C and 13C--which differ only in the number of neutrons in the nucleus. By far the most abundant variety is in the lighter, 12C. About 1% is 13C, a heavier sibling with an additional neutron; it is the key to understanding photosynthetic organisms.
"Photosynthetic microbes evolved in the shallow water where light was plentiful," explained Eigenbrode. "They used light and CO2 to produce their food, like cyanobacteria do today. They gobbled up 12C and 13C, which became part of the organisms. The results are recorded in the rocks containing the remains for us to find billions of years later. Organisms leave behind different mixes of 12C and 13C depending on what they eat and how they metabolize it. Changes in these chemical fingerprints tell us about changes in how organisms got their energy and food."
In the Archean, microbes that could not live with oxygen--anaerobic organisms--ended up with relatively small amounts of 13C. As oxygen became available in shallow water due to oxygen-producing photosynthesis, anaerobic organisms were out-competed by microbes that had adapted to oxygen. As a result, the amount of 13C increased--first in shallow water, then in deeper water. Changes in the mix of carbon isotopes in these late Archean rocks indicate microbes were learning to live with oxygen well before the atmosphere began accumulating noticeable amounts of oxygen.
Jennifer Eigenbrode | EurekAlert!
Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union
Enormous dome in central Andes driven by huge magma body beneath it
25.10.2016 | University of California - Santa Cruz
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
25.10.2016 | Earth Sciences
25.10.2016 | Power and Electrical Engineering
25.10.2016 | Process Engineering