Mega meteorite tore up seabed and boiled Earth's oceans

Georgina Rannard - Climate and science reporter
Mon, October 21, 2024 

The meteorite was 40-60km in diameter and left a crater 500km across [Getty Images]


A huge meteorite first discovered in 2014 caused a tsunami bigger than any in known human history and boiled the oceans, scientists have discovered.

The space rock, which was 200 times the size of the one that wiped out the dinosaurs, smashed into Earth when our planet was in its infancy three billion years ago.

Carrying sledge hammers, scientists hiked to the impact site in South Africa to chisel off chunks of rock to understand the crash.

The team also found evidence that massive asteroid impacts did not bring only destruction to Earth - they helped early life thrive.

“We know that after Earth first formed there was still a lot of debris flying around space that would be smashing into Earth,” says Prof Nadja Drabon from Harvard university, lead author of the new research.

“But now we have found that life was really resilient in the wake of some of these giant impacts, and that it actually bloomed and and thrived,” she says.

The meteorite S2 was much larger than the space rock we are most familiar with. The one that led to the dinosaurs’ extinction 66 million years ago was about 10km wide, or almost the height of Mount Everest.

But S2 was 40-60km wide and its mass was 50-200 times greater.

It struck when Earth was still in its early years and looked very different. It was a water world with just a few continents sticking out of the sea. Life was very simple - microorganisms composed of single cells.

Nadja and her colleagues went to the Eastern Barberton Greenstone Belt in South Africa to collect rock samples [Nadja Drabon]

The impact site in Eastern Barberton Greenbelt is one of the oldest places on Earth with remnants of a meteorite crash.

Prof Drabon travelled there three times with her colleagues, driving as far as possible into the remote mountains before hiking the rest of the way with backpacks.

Rangers accompanied them with machine guns to protect them against wild animals like elephants or rhinos, or even poachers in the national park.

They were looking for spherule particles, or tiny fragments of rock, left behind by impact. Using sledge hammers, they collected hundreds of kilograms of rock and took them back to labs for analysis.

Prof Drabon stowed the most precious pieces in her luggage.

"I usually get stopped by security, but I give them a big spiel about how exciting the science is and then they get really bored and let me through," she says.

The team travelled with rangers who could protect them from wild animals like elephants or rhinos [Nadja Drabon]

The team have now re-constructed just what the S2 meteorite did when it violently careened into Earth. It gouged out a 500km crater and pulverised rocks that ejected at incredibly fast speeds to form a cloud that circled around the globe.

“Imagine a rain cloud, but instead of water droplets coming down, it's like molten rock droplets raining out of the sky,” says Prof Drabon.

A huge tsunami would have swept across the globe, ripped up the sea floor, and flooded coastlines.

The 2004 Indian Ocean tsunami would have paled in comparison, suggests Prof Drabon.

All that energy would have generated massive amounts of heat that boiled the oceans causing up to tens of metres of water to evaporate. It would also have increased air temperatures by up to 100C.

The skies would have turned black, choked with dust and particles. Without sunlight penetrating the darkness, simple life on land or in shallow water that relied on photosynthesis would have been wiped out.

The team of geologists analysed rock showing evidence of ripped up seafloor [Nadja Drabon]

These impacts are similar to what geologists have found about other big meteorite impacts and what was suspected for S2.

But what Prof Drabon and her team found next was surprising. The rock evidence showed that the violent disturbances churned up nutrients like phosphorus and iron that fed simple organisms.

“Life was not only resilient, but actually bounced back really quickly and thrived,” she says.

“It’s like when you brush your teeth in the morning. It kills 99.9% of bacteria, but by the evening they're all back, right?” she says.

The new findings suggest that the big impacts were like a giant fertiliser, sending essential ingredients for life like phosphorus around the globe.

The tsunami sweeping the planet would also have brought iron-rich water from the depths to the surface, giving early microbes extra energy.

The findings add to a growing view among scientists that early life was actually helped by the violent succession of rocks striking Earth in its early years, Prof Drabon says.

“It seems that life after the impact actually encountered really favourable conditions that allowed it to bloom,” she explains.

The findings are published in the scientific journal PNAS.


Ancient meteorite was 'giant fertilizer bomb' for life on Earth

Mon, October 21, 2024 





Small spherules are seen in rock from a region called the Barberton Greenstone Belt in northeastern South Africa

By Will Dunham

WASHINGTON (Reuters) - The space rock that slammed into Earth 66 million years ago at the end of the Cretaceous Period caused a global calamity that doomed the dinosaurs and many other life forms. But that was far from the largest meteorite to strike our planet.

One up to 200 times bigger landed 3.26 billion years ago, triggering worldwide destruction at an even greater scale. But, as new research shows, that disaster actually may have been beneficial for the early evolution of life by serving as "a giant fertilizer bomb" for the bacteria and other single-celled organisms called archaea that held dominion at the time, providing access to the key nutrients phosphorous and iron.

Researchers assessed the effects of this meteorite impact using evidence from ancient rocks in a region in northeastern South Africa called the Barberton Greenstone Belt. They found ample signs - mostly from the geochemical signature of preserved organic material but also from fossils of mats of marine bacteria - that life bounced back with aplomb.

"Life not only recovered quickly once conditions returned to normal within a few years to decades, it actually thrived," said Harvard University geologist Nadja Drabon, lead author of the study published on Monday in the journal Proceedings of the National Academy of Sciences.

Earth was a much different place during the Paleoarchean Era when this occurred, and meteorite impacts were larger and more frequent.

"At this time, Earth was something of a water world, with limited emergence of volcanoes and continental rocks. There was essentially no oxygen gas in the atmosphere and oceans, and no cells with nuclei," Harvard geologist and study co-author Andrew Knoll said.

The meteorite was a type called a carbonaceous chondrite that is rich in carbon and also contains phosphorus. Its diameter was approximately 23-36 miles (37-58 km), Drabon said, making it about 50-200 times the mass of the asteroid that wiped out the dinosaurs, aside from their bird descendants.

"The effects of the impact would have been quick and ferocious. The impactor hit with so much energy that it and whatever sediment or rock it hit vaporized. This rock vapor cloud and dust ejected from the crater would have circled the globe and turned the sky black within hours," Drabon said.

"The impact likely occurred in the ocean, initiating a tsunami that swept across the globe, ripping up the sea floor and inundating coastlines. Lastly, a lot of the impact energy would get transferred into heat, meaning that the atmosphere started heating up so much that the upper layer of the oceans started boiling," Drabon added.

It probably would have taken a few years to decades for the dust to settle and for the atmosphere to cool enough for the water vapor to return to the ocean, Drabon said. Microbes depending on sunlight and those in shallow waters would have been decimated.

But the meteorite would have delivered a large amount of phosphorous, a nutrient for microbes crucial for the molecules central to storing and conveying genetic information. The tsunami also would have mixed iron-rich deep waters into shallower waters, creating an environment ideal for many types of microbes because iron provides them with an energy source.

"Imagine these impacts to be giant fertilizer bombs," Drabon said.

"We think of meteorite impacts as being disastrous and detrimental to life - the best example being the Chicxulub impact (at Mexico's Yucatan Peninsula) that led to the extinction of not only the dinosaurs but also of 60-80% of animal species on Earth," Drabon said. "But 3.2 billion years ago, life was a lot simpler."

"Microorganisms are relatively simple, versatile, and they reproduce at fast rates," Drabon said.

The evidence of the impact included chemical signatures of the meteorite, small spherical structures formed from rock melted by the impact, and chunks of seabed mixed with other debris churned up by the tsunami in sedimentary rock.

"Early life was resilient in the face of a giant impact," Drabon said.

(Reporting by Will Dunham, Editing by Rosalba O'Brien)