Astrobiologists at the University of Colorado’s Department of Geological Sciences say an intense asteroid bombardment nearly four billion years ago may not have been as cataclysmic as originally thought.

A growing scientific consensus is that during our solar system’s formation, planetary bodies were pummeled by asteroids and debris. A visual record of the event is preserved in the form of the scarred face of our moon.

Oleg Abramov and Stephen J. Mojzsis say the Late Heavy Bombardment (LHB) occurred approximately 3.9 billion years ago and lasted 20 to 200 million years with asteroids, some the size of Kansas, pummeling the Earth’s surface.

The two say their Nasa-funded project showed that while the LHB might have generated enough heat to sterilize the Earth’s surface, microbial life in subsurface and underwater environments almost certainly would have survived.

“Even under the most extreme conditions we imposed on our model, the LHB could not have sterilized Earth completely.

“Our results are in line with the scientific consensus that hyperthermophilic, or ‘heat-loving,’ microbes could have been the earliest life forms on Earth, or survivors from an even more ancient biosphere.

“The results also support the potential for the persistence of microbial biospheres on other planetary bodies whose surfaces were reworked by the bombardment, including Mars,: Abramov said.

Michael H. New, the astrobiology discipline scientist and manager of the Exobiology and Evolutionary Biology Program at Nasa headquarters in Washington described the findings as significant.

“They indicate that if life had begun before the LHB or some time prior to 4 billion years ago, it could have survived in limited refuges and then expanded to fill our world.”