On University of Rochester Week: We’re still making new discoveries about how life formed on our planet.
John Tarduno, the William R. Kenan, Jr. professor of geophysics in the department of Earth and Environmental Sciences, details a new finding.
John Tarduno’s research centers on the origin of the geodynamo, its history and relationship with habitability. Such questions have become of significant recent interest in astrophysics in studies of exoplanets. To investigate the magnetic field of the early Earth, Tarduno and his research group have developed a method to derive information on past field strength from single silicate minerals.
He joined the University of Rochester in 1993 where he founded the paleomagnetism laboratory. Tarduno is currently the William R. Kenan., Jr., Professor of Geophysics in the Department of Earth and Environmental Sciences, and holds appointments as Professor of Physics and Astronomy, and Distinguished Scientist in the Laboratory for Laser Energetics
Tarduno is a recipient of the Price Medal of the Royal Astronomical Society, and the Petrus Peregrinus Medal of the European Geosciences Union, and is a fellow of the American Geophysical Union.
Weak magnetic field millions of years ago may have fueled the proliferation of life
The Ediacaran Period 635 to 541 million years ago, was an era when complex, multicellular organisms emerged. How did this surge of life unfold and what factors on Earth may have contributed to it?
My research asks whether a huge change in Earth’s ancient magnetic field strength led to shifts in oxygen levels that may have been crucial to the proliferation of macroscopic life forms millions of years ago.
The fauna of the Ediacaran Period were remarkable because earlier animal life was microscopic. Ediacaran animals reached sizes of more than three feet and were mobile.
Liquid iron churns in Earth’s outer core, creating the planet’s protective magnetic field essential for life on Earth by shielding solar winds. But Earth’s magnetic field wasn’t always as strong as it is today. What had been unknown is the mean strength of the field during the Ediacaran Period.
We studied this through magnetism locked in ancient feldspar and pyroxene crystals from the rock anorthosite. The crystals contain magnetic particles that preserve magnetization from the time the minerals were formed.
The data indicates that Earth’s magnetic field during the Ediacaran Period was on the verge of complete collapse, with values 30 times weaker than the magnetic field today. This weak-field state lasted for at least 26 million years and made it easier for charged particles from the sun to strip away lightweight atoms such as hydrogen from the atmosphere, causing them to escape into space. If hydrogen loss is significant, more oxygen may remain in the atmosphere leading to its buildup over time. Our research suggests that during the Ediacaran Period, the ultraweak magnetic field caused a loss of hydrogen over at least tens of millions of years. This loss may have led to increased oxygenation of the atmosphere and surface ocean, enabling more advanced life forms to emerge.
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The Conversation – John Tarduno
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