Five years of sawing, crushing, dissolving, and analyzing later, they have coaxed from those rocks a secret hidden for eons: the era when plate tectonics began.Earth’s fractured carapace of rigid, interlocking plates is unique in the solar system. Scientists increasingly connect it to our planet’s other special features, such as its stable atmosphere, protective magnetic field and menagerie of complex life. But geologists have long debated exactly when Earth’s crust broke into plates, with competing hypotheses spanning from the first billion years of the planet’s 4.5-billion-year history to sometime in the last billion. Those estimates have wildly different implications for how plate tectonics affects everything else on Earth.
As the first spacecraft to visit a carbonaceous asteroid, Hayabusa2 can help determine the provenance of meteorites discovered on Earth and shed some light on the processes that formed the organic compounds in the early solar system.“Are there samples of the organics that we don’t have in our collection because they didn’t survive going through the atmosphere?
The spreading, smashing, and plunging of tectonic plates shapes far more than just geography. The recycling of Earth’s surface helps to regulate its climate, while the building of continents and mountains pumps vital nutrients into the ecosystem. Indeed, plate tectonics, if it began early enough, may have been a major driver of the evolution of complex life. And by extension, shifting plates could be a prerequisite for advanced life on distant planets as well.Now, a study of the rocks from the Australian Outback by Tusch, Münker and their co-authors, published in Proceedings of the National Academy of Sciences, has captured “a snapshot” of the advent of plate tectonics, said Alan Collins, a geologist at the University of Adelaide in Australia. The team’s analysis of tungsten isotopes in the rocks reveals Earth in the act of transitioning to plate tectonics around 3.2 billion years ago.
The findings buttress other circumstantial evidence accrued over the last decade pointing to that date, said Richard Palin, a petrologist at the University of Oxford. It “supports the growing consensus in the geological community that plate tectonics established itself at a global scale” sometime around 3 billion years ago, he said.“There’s a lot of different people, coming from very different perspectives, coming up with a convergence of 3.2 to 3 billion years,” said Collins.Earth’s EngineWhen the geologist Alfred Wegener first proposed the theory of continental drift in 1912, most of his colleagues thought it was preposterous. How could giant landmasses move? Wegener couldn’t identify a mechanism to drive his drifting continents. And indeed it would take another five decades for geologists to figure out how convection within Earth’s mantle—the thick layer of hot rock between the crust and core—propels the plates on the surface. They eventually showed that these plates—15 main ones and dozens of smaller ones—spread apart at mid-ocean ridges, move with the mantle’s flow, scrape against each other at their edges, and plunge back into the mantle at “subduction zones.”
“Plate tectonics gives a very organized way of moving the surface,” said Carolina Lithgow-Bertelloni, a geophysicist at the University of California, Los Angeles. “You can then understand why there are earthquakes where there are earthquakes, why there are mountains where there are mountains.”
So among the set of actions we can take, that are likely to increase the scope and scale of consciousness such that we are better able to understand the nature of the universe, one of those actions is to become a multi-planet species or ensure that life is multi-planetary, not because I think—it's not not from the standpoint of it just being an escape hatch, or because I think that Earth is doomed.