Findings about Earth鈥檚 Crust Could Unlock Mysteries of Exoplanets
Image by Richard Gaschnig
04/04/2023
By Brooke Coupal
Earth as we know it today looked drastically different several billion years ago.
According to a paper recently published in the 聽(PNAS), the composition of the continents resembled the ocean floor, consisting of a dense crust that sits lower on the Earth鈥檚 very hot and soft mantle. But about 3 billion years ago, the continental crust transitioned, making the planet more hospitable to life.
鈥淭he Earth transitioned to this distinct rock type that gives rise to the continents, so you get a lot more land above sea level, making Earth more habitable to advanced life,鈥� says Environmental, Earth and Atmospheric Sciences Assoc. Prof. Richard Gaschnig, who co-authored the research paper.
The researchers鈥� findings on the evolution of the Earth鈥檚 crust could lead to a better understanding of the formation of exoplanets 鈥� planets outside of our solar system. According to , more than 5,000 exoplanets have been discovered in the Milky Way Galaxy since the 1990s.
鈥淲e are looking at the Earth back then to figure out how planets operate,鈥� Gaschnig says. 鈥淎s researchers keep discovering extrasolar planets, we鈥檙e trying to find what the process of planetary evolution is going to look like and how that might apply to whether life can develop or not.鈥�
Research Supports Transition of Earth鈥檚 Crust
Scientists have debated whether the Earth鈥檚 crust went through a major change, and the research behind the PNAS publication shows that it did, says Gaschnig, whose work was funded by a $226,000 .
To find how the continents鈥� composition changed through time, Gaschnig collected samples of ancient glacial deposits from around the world, including in China, Namibia, South Africa, Bolivia, Canada and the United States. The deposits are the result of ice ages in which massive ice sheets ground up rock material before dumping them in areas later discovered by scientists. Like geological time capsules, the deposits offer a glimpse into the past.
Image by Richard Gaschnig
The researchers measured isotopes of the chemical element vanadium within the samples to determine if the composition resembled the ocean crust or the current continental crust. Their results showed that the continents used to have a crust similar to the ocean鈥檚, known as a mafic crust, before transitioning to a less dense crust, known as a felsic crust, about three billion years ago. The change in Earth鈥檚 crust may have been caused by the onset of plate tectonics.
鈥淭oday鈥檚 crust is broken up into slabs that move around and bump into each other, causing mountains to form, earthquakes and volcanoes,鈥� Gaschnig says. 鈥淲e鈥檙e on the North American plate, and it鈥檚 drifting across to the west at about an inch or two a year, but that process might not have been happening at all back then. The Earth might have just been a single-plate planet.鈥�
Gaschnig hopes his future research will continue to uncover the mysteries of the Earth.
鈥淪cience is very cumulative,鈥� he says. 鈥淵ou鈥檙e always building on your research and everyone else鈥檚 work.鈥�
