The space rock that hit Earth 66 million years ago and caused the deaths of many life forms – including dinosaurs - was not the largest object to ever strike our planet.
One meteorite up to 200 times bigger hit the planet 3.26 billion years ago, causing worldwide destruction. But, as new research shows, that event may have been helpful for the early development of life.
The meteorite may have served as "a giant fertilizer bomb." In other words, it may have supplied the key nutrients phosphorus and iron for the bacteria and other organisms that existed at the time.
Researchers studied the effects of this meteorite strike using evidence from ancient rocks in an area in northeastern South Africa. The area is called the Barberton Greenstone Belt.
Researchers found many signs that life quickly came back after the strike.
"Life not only recovered quickly once conditions returned to normal within a few years to decades, it actually thrived," said Nadja Drabon of Harvard University.
Drabon was the lead writer of the study that appeared recently in the scientific publication Proceedings of the National Academy of Sciences.
Earth was a much different place when the meteorite strike took place.
At the time, during the Paleoarchean Era, meteorite strikes were larger and more common.
"At this time, Earth was something of a water world... There was essentially no oxygen gas in the atmosphere and oceans, and no cells with nuclei," said study co-writer Andrew Knoll.
The meteorite was rich in carbon and also contained phosphorus. Its diameter was around 37-58 kilometers, Drabon said, meaning its mass was 50 to 200 times the mass of the asteroid that killed the dinosaurs.
The effects of the hit, or impact, would have been quick and serious, Drabon suggested.
The impact force would have caused a dust storm that circled the world and turned the sky black within hours, she explained. It also would have likely had a big effect on the ocean and created a lot of heat, possibly boiling the upper part of the oceans.
Drabon said it probably would have taken years for the dust to settle and for the atmosphere to cool enough for the water vapor to return to the ocean.
But the meteorite would have contained a large amount of phosphorous. It is an important nutrient for molecules central to storing and sharing genetic information.
Powerful ocean waves also would have mixed iron-rich deep waters into shallower waters, creating a good environment for many kinds of microbes. Iron provides microbes with an energy source.
"Imagine these impacts to be giant fertilizer bombs," Drabon said.
"We think of meteorite impacts as being disastrous," 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 added.
The evidence of the hit included chemical signatures of the meteorite, small circular structures formed from rock melted by the impact, and pieces of seabed mixed with other debris in sedimentary rock.
"Early life was resilient in the face of a giant impact," Drabon said.
I’m John Russell.
