The day a meteorite four times the size of Everest fell to Earth

Nadja Drabon, a geologist in the Department of Earth and Planetary Sciences at Harvard University, has dedicated her career to trying to find out what the planet was like at the time of that intense bombardment, when only bacteria and single-celled archaea existed on Earth, and when and why everything began to change until it became the world we know. When did the first oceans appear? What about the continents? And with plate tectonics? How did all those violent impacts affect the evolution of life?

A new study published by this researcher and her team in ‘Proceedings of the National Academy of Sciences’ sheds light on some of these questions. And it does so by thoroughly analyzing the so-called ‘S2’ impact, which occurred more than 3 billion years ago and whose geological evidence is still preserved today in the ‘Barberton Greenstone Belt’, in South Africa.

Everest four times

Through meticulous and exhausting field work, walking through mountain passes that contain sedimentary evidence and collecting the first splashes of rock that were embedded in the soil and preserved over time in the Earth’s crust, and after analyzing the sedimentology, geochemistry and carbon isotope compositions left by the passage of time, Drabon’s team managed to construct the most convincing picture to date of what happened the day a meteorite measuring more than 35 km (four times the size Mount Everest) fell on our planet.

“Imagine standing off the coast of Cape Cod (a famous hook-shaped tourist peninsula in Massachusetts), on a shelf of shallow water,” says the researcher. It is a low energy environment, without strong currents. And then, suddenly, a giant tsunami appears that passes and destroys the bottom of the sea.

The S2 meteorite, much larger than the one that killed the dinosaurs (which was about 10 km and fell in the Gulf of Mexico 66 million years ago), caused a tsunami of such magnitude that it churned up the entire ocean, tore away parts of the bottom and It dumped huge amounts of rocks and dirt into coastal areas. The heat from the impact also caused the upper layer of the ocean to evaporate, while warming the atmosphere. A thick cloud of dust covered everything, blocking any photosynthetic activity that might be taking place.

and life changed

But the bacteria are resistant and, according to the team’s analysis, they recovered quickly after the impact. And not only that, but there was a sharp increase in the populations of organisms that feed on the elements phosphorus and iron. The iron was probably washed from the ocean floors into shallow waters by the aforementioned tsunami, and the phosphorus was delivered to Earth by the meteorite itself and by increased land erosion itself.

Drabon’s analysis shows that these iron-metabolizing bacteria would have flourished immediately after the impact. A change that turns out to be a key piece of the puzzle that describes early life on Earth. According to the study, indeed, meteorite impacts, despite killing everything in their path (including dinosaurs 66 million years ago), have a positive side for life.

“We think of impact events as disastrous for life,” says Drabon. “But what this study highlights is that these impacts would actually have brought benefits, especially in the early stages… these impacts could have allowed life to flourish.”

Chemical signatures hidden in thin layers of rock helped Drabon gather evidence of tsunamis and other cataclysmic events. The Barberton Greenstone Belt, where Drabon’s team currently focuses most of its work, contains evidence of at least eight different impact events, including S2. And the researcher does not plan to stop until she manages to extract every last one of their secrets about the often mysterious history of the Earth.