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Was early Earth habitable?

Planet Earth in its infancy phase when it was being hit by massive asteroids could have been habitable with the presence of isolated areas of liquid water, according to a new study.

The study has been published in today's issue of the journal Nature.

During the Hadean period, Earth's crust was subjected to consistent powerful bombardments by asteroids, comets as well as meteors.

The authors in their study state that any form of life evolving during Earth's initial half billion years would have been resistant to severe conditions and would also be capable of spreading from the few stable places present at that time.

Dr Simone Marchi from the Southwest Research Institute, in Boulder Colorado, along with his colleagues, have come up with a computer model that gives a detailed insight of the Hadean epoch.

According to the researchers, every major portion of the Earth would have been impacted at one point or another.

A few of the simulations demonstrate the impacts of 1000-kilometre wide asteroids that were capable of wiping out any form of life existing at that time.

The simulations also showed about seven asteroids more than 500 kilometers wide that would have smashed the Earth, the impact of each one would cause worldwide ocean vaporisation, in turn producing a steam atmosphere, as well as magma oceans, with the most recent happening four billion years ago.

The study author Marchi and his colleagues discovered during the course of the study that the highest bombardment of the infant Earth took place soon after the formation of the Moon and slowly tapered off until the simulation ended 3.5 billion years ago, when the number of impacts was insignificant.

The researchers found out Earth's early impact history by studying the greatly cratered surface of the Moon which given an insight into the number of impact events as well as the size of the objects that caused them.