But any organisms brave enough to carve out a niche on early Earth would have needed to endure extreme conditions, including an asteroid storm that peppered the planet for 500 million years. Some asteroids were as small as football field. The big ones were 1,000 times the size of Manhattan.
Dr. Simone Marchi and his colleagues at the Southwest Research Institute, in Boulder, Colo., developed a computer model that predicts what this hellish time in Earth's earliest days -- called the Hadean epoch -- might have looked like. And though it wouldn't have been so pleasant for inhabitants, Marchi and others say these characteristics made what Earth is today, perhaps paving the way for life as we know it.
"The oldest traces for life on Earth have been found in old rocks -- isotopic traces of life. Those rocks date to 3.9 billion years old," explained Marchi -- a date not long after the asteroid storm of the Hadean eon.
"Is that just a coincidence or is there a more profound link to what's going on in the Hadean and the present? It's a very difficult problem to address, and there's a lot of work to be done in that regard. This paper is just a step toward that goal."
Marchi, whose recent research into Earth's earliest conditions was published in Nature, thinks more research is needed to understand exactly how these asteroids shaped Earth.
"When you have a large collision, you basically dig a large hole in the ground, and that means mixing and melting of the rocks," explained Marchi. "The heat from the impact can melt rocks in the proximity of collision. Mixing, melting and burial of rocks must have been extremely important back then, and we need to understand how the crust formed."