Sometimes, getting hit by a space rock is a good thing. The asteroid which struck Earth 66 million years ago wiped the dinosaurs off the planet (at least until John Hammond built Jurassic Park) but cleared the way for the age of mammals, and us.
A few billion years earlier than that, a massive meteorite four times the size of Everest smashed into the planet. The destruction was catastrophic, but the iron and nutrient rich aftermath may have been beneficial to the microscopic survivors, according to a new study published in the Proceedings of the National Academy of Sciences.
Asteroid and meteorite bombardment may have fueled early life on Earth
The early solar system was a chaotic and violent place where impacts from asteroids and meteorites were common. The solar system started as a cloud of gas and dust which formed into a disk accreting around a central mass. That central mass eventually gathered enough material to begin fusion and the Sun was born. The disk settled into planets, small and rocky or large and gaseous, with a whole bunch of cosmic construction materials (asteroids, meteors, and comets) left over.
As everything swirled around the Sun, driven by the complex pull of gravity, space rocks smashed into the planets, the moons, and the Sun, becoming part of them. Eventually, most of the collisions that could happen, had happened, and the solar system got a little calmer. This period of relative violence is called the Late Heavy Bombardment, and you can see evidence of it written in scars across the face of the Moon. It’s been a while since our planet was rocked by a sucker punch from outer space, but the ancient microbes who jump started life on Earth had to deal with them relatively often.
About 3.26 billion years ago, Earth got hit by a meteorite roughly 50 – 200 times the size of the rock that killed the dinosaurs. The impact triggered a tsunami unlike any the Earth has seen before or since, evaporated a considerable portion of its oceans, raised the global temperature, and plunged the world into darkness. The hot, dark, tumultuous environment created by the impact was catastrophic to the photosynthetic microbes living in shallow waters. Microbes living in deeper waters or thermophiles relying on deep ocean vents didn’t feel the sting quite as much.
The negative effects of the impact would have been devastating but relatively brief, according to the study, while the benefits stretched into the medium and long term. The meteorite itself was vaporized, releasing its chemical components into Earth’s environment. Scientists noted a spike in phosphorus likely from the vaporized meteorite, in addition to a spike in iron and nutrients caused by nutrient-rich deep waters being recirculated around the planet by the impact.
In the same way that the end-Cretaceous extinction was bad for the dinosaurs but good for us, this ancient meteorite impact was bad for the microbes sunbathing in the shallows but good for everyone else. The nutrients added and recirculated throughout the biosphere resulted in a bloom of iron-cycling microbes.
Researchers suggest that whether an impact is good or bad depends on a number of factors. “The effect of a giant impact on life depends on the size and type of the impactor, the target material, the conditions of the atmosphere and hydrosphere, and the type of life present at the type of impact,” the authors wrote. Impactors deliver crucial payloads of sulfur, phosphorus, iron, and other biologically important materials, even if they make their deliveries violently. That’s probably cold comfort to the shallow water microbes, the dinosaurs, and everything else sacrificed on the altar of cosmic and biological evolution.
At least the dinos got a second chance in Jurassic Park, available now from Universal Pictures.
