Earth scientist discovers what happened after a meteorite the size of four Mt. Everests hit Earth

It was common for meteorites to hit the planet billions of years ago. This happened also precisely 3.26 billion years ago, which helped to define the planet that Earth has become. Geologists are still figuring out how much today.

Nadja Drabon, an early-Earth geologist and assistant professor in the Department of Earth and Planetary Sciences wonders what the planet would have looked like on the ancient earth, when meteorites plummeted to the surface, and the only life that existed were bacteria and archaea.

Their team took on backbreaking work, hiking to mountain passes to uncover sedimentary rocks that hid chemical clues marking a tsunami from as far back as over 3 billion years ago. There was still much change to come, from the oceans, to the continents and even plate tectonics. Catastrophic, violent impacts shaped and sculpted the Earth in many ways.

A new study in Proceedings of the National Academy of Sciences shows how much the S3 meteoritic impact took effect, over 3 billion years ago. Evidence is unpicked from the Barberton Greenstone belt of South Africa today.

Drabon’s team analysed the geochemistry, sedimentology and carbon isotope compositions left behind in site samples, to show what happened the day a meteorite mammoth the size of four mountains as big as Mount Everests met the Earth.

The S2 meteorite shaped the Earth

Being 200 times bigger than the meteorite responsible for killing the dinosaurs, the S2 meteorite set off a tsunami made up of the ocean and debris the land to coast. It brought so much heat from impact that the top of the ocean boiled and heated the atmosphere rapidly, bringing a thick cloud of dust to shroud everything in sight. Blocking sunlight shut off photosynthetic activity.

Bacteria are resilient, the team found, for the survived the vent and even bounced back quickly. Populations of unicellular life expanded by feeding off the elements iron and phosphorus. Iron upwelled from the deep ocean by the tsunami, and phosphorus nutrients came from the meteorite itself as well as the additional erosion its impact had caused.

Iron eating bacteria thrived after impact

While much life died, this intense event caused an opportunity for some lifeforms. The research showed that it was bacteria that metabolise iron that would have taken off just after the impact, as part of one of the intricate threads of Earth’s early life.

“We think of impact events as being disastrous for life,” Drabon said. “But what this study is highlighting is that these impacts would have had benefits to life, especially early on … these impacts might have actually allowed life to flourish.”

It has been observed in geological research, since deep time, that catastrophic events and extinction events might kill the majority of life on earth, but create opportunities for niche organisms to utilise their strengths, depending on what accommodations are available. In this case, iron and phosphorous provided a feast for single celled bacteria after this monumental impact.

Drabon and the team plan to continue to study the The Barberton Greenstone Belt in South Africa to understand past tsunamis and other cataclysmic events on Earth.