In the first billion years of existence, our planet and many other objects in the solar system were under a continuous rain of asteroid and meteors. This period, aptly called the Late Heavy Bombardment, doesn’t seem very-life friendly. However, new research suggests that some areas of habitability might have persisted.

The research was conducted by Robert Grimm and Simone Marchi from the Southwest Research Institute in Boulder Colorado. The scientists studied zircon fragment from the early Earth. These stones suggest that there was a decent amount of water to be found within the last few kilometers of the Earth Crust, even during the Late Heavy Bombardment. And if there is water, there could have been the conditions for life. 

As reported in Earth and Planetary Science Letters, the team looked at how asteroid impacts might have affected the Earth’s crust and its components. The impact would heat up and break the crust, but the research found that over time, the effect becomes more limited. And regions that could host life become more and more common. Some of these regions were likely havens among the hellish landscape of the primordial Earth.

The research focuses on the Hadean and early Archean time period which stretched between 4.5 and 3.5 billion years ago. The initial period has the Earth recovery from the Mars-sized impact which formed the Moon and continuing to be the target in a cosmic billiard game. The team estimated that the heat from projectiles was able to melt the entire crust several times during the first few hundred million years.

But sometime after 4.2 billion years ago, the impacts began to occur less often and the team estimates that at most the Earth was completely resurfaced once. This suggests that habitable subsurface localities were possible and present long before life actually emerged.

The researchers estimated that the only way to make the Earth completely sterile was a more intense and quick bombardment. To completely destroy life-friendly zone, the Earth should have had ten times more impacts in one-tenth of the time.

While life might have been possible in those regions, it is not clear if it was probable. Asteroid impacts on such magnitude, might not have affected the whole crust but they would have brought changes to the atmosphere and even in movements within the mantle. Understanding what our planet was like back then is not at all simple.

[h/t: Science News]