Our planet formed about four-and-a-half billion years ago. Soon afterward, whatever life may have developed was wiped out during what's called the Late Heavy Bombardment--a deluge of massive meteor and comet strikes that began around 3.9 billion years ago and probably lasted for a hundred million years.

The Bombardment melted much of the earth's crust and boiled away the oceans, rendering the planet a seething, hellish sphere hostile to surface life. But apocalypse eventually gave way to rebirth as the Earth cooled and microbial life made a comeback.

Life Underground

That's the story, in a nutshell. But according to one study, the Late Heavy Bombardment may not have done quite as much damage as previously thought. Computer models show that meteor and comet strikes probably melted only a small part of the earth's crust.

Even if the oceans did evaporate, hydrothermal vents likely provided shelter for microbes that thrive in extreme conditions--in this case extreme heat. So life not only carried on during the Bombardment--it may have actually thrived, albeit underground.

So what?

The study suggests that life on Earth has existed without interruption for longer than we thought. Knowing this is important for understanding how life may have developed in the first place.

Plus, if microbes were able to withstand Earth's fiery bombardment, perhaps there are alien microbes thriving in extreme conditions deep below the surface on other planets, like Mars.

And, finally, if early life on our planet was able to soldier on despite the chaos of the Late Heavy Bombardment, well, that's quite a testament to life's tenacity.