When the Acraman asteroid struck the Earth, the single-celled cyanobacteria were largely wiped out. Post impact, more complex single-celled organisms thrived and became a source of food for other life forms.
Credit: iStockPhoto
We know the age of the dinosaurs came to an abrupt, painful end when a huge asteroid crashed to Earth 65 million years ago.
But tantalising new evidence suggests it may also have kick-started their reign in the first place: dinosaurs grew and diversified to dominate the world, but only after 95% of marine life and 70% of land species were obliterated by an earlier asteroid strike at the end of the Permian Period.
And in much the same way, following the demise of the dinosaurs, another group evolved and grew rapidly to dominate: mammals.
Mammals first arose about 210 million years ago, but didn’t diversify greatly in size or ecological niches until an asteroid pushed dinosaurs into extinction.
Over the next 20 million years, mammals grew in size from a maximum body size of 10 kg to Indricotherium - an enormous 17 tonne rhinoceros-like herbivore.
It’s a pattern that is repeated throughout history – in fact, since the Solar System formed 4.6 billion years ago. Major meteorites cleared the evolutionary path not just for dinosaurs and mammals, but for the development and diversification of all organisms, from the earliest life to the first large and complex animals.
In the beginning, Earth saw a period of relative peace for 700 million years. The giant planets began a complex ballet, upsetting the delicate gravitational balance of objects beyond the Solar System and within the Asteroid Belt between Mars and Jupiter.
Gigantic meteorites rained upon the young Earth in a constant barrage known as the Late Heavy Bombardment. Some were 50 km across, and left craters that today would easily bury Britain.
The bombardment lasted at least 20 million years (and possibly 200 million years). As the impacts shattered the crust, dust scattered high into the atmosphere, blanketing out the Sun and boiling or vaporising the oceans.
Travelling at up to 250,000 km/h, meteorites melted the crust, feeding volcanoes that warmed the planet. Roughly 200,000 million million tonnes of meteorites rained down on the young planet, and up to a quarter of the Earth was resurfaced.
At first glance, this sort of bombardment looks like the kind of thing that would doom life before it even got the chance. But that might not be the whole story.
“The difficulty is untangling all the threads, when the evidence has been obliterated by the very phenomenon we are interested in,” says astrobiologist and author Paul Davies, the director of the Beyond Centre for Fundamental Concepts in Science at Arizona State University.
Geologists Oleg Abramov and Stephen Mojzsis believe life’s chances were not only good, but improved by the bombardment. This massive assault from space may have created the cradle of life, or helped life along its evolutionary path. And this is the killer asteroids’ hidden story.
Perhaps, instead of dramatically and periodically pushing life towards destruction, the impact of impacts is to help life – or certain types of life – evolve.
Abramov and Mojzsis, from the University of Colorado, Boulder, found no scenario, no combination of many small or several massive meteorite impacts during the bombardment that would have left Earth barren.
In fact, they found that it created an underground network of hot, mineral-rich fluids, which provided at least a sanctuary to life or may even have been the crucible of life’s origin, they reported in March 2009 in the British journal Nature.
Hydrothermal networks and hot oceans favour the kind of life that thrives in heat: so-called thermophillic microbes, which thrive in temperatures between 45°C and 80°C, or even hyperthermophillic microbes, some of which live near black smokers fed by hydrothermal systems in the deep ocean at temperatures above 113°C.
Davies theory on a shadow
Davies theory on a shadow biosphere can't receive support from bad science, which is what the arsenic bacteria hoax is about. Please check your information before spreading nonsense.