You wouldn't want to have been alive four billion years ago. There was no oxygen to breathe, no ozone in the air (it would have been really, really, easy to get sunburnt), and no animals to hang out with or eat. Plus, the era was known as the "Late Heavy Bombardment": asteroids and comets pummeled the Earth.
Those hurtling chunks of rock and ice could easily take out a human, if not all humans. But they may have actually been a good thing for ancient microbes. Not immediately, during the instant of impact, of course. But an "initially detrimental" asteroid strike, geologists explain in a new paper, might have created nooks and crannies perfect for early life to take up long-term residence.
The geologists looked at the roughly 30 million-year old Haughton meteorite impact crater in northern Canada. They collected 28 rock samples from both in and out of the crater. When they put the rocks under the microscope, they found that rocks which had experienced the greatest shock from the impact were the ones with the most pores.
They explain to Inside Science why these pores might have been cozy environments for microbes:
Not only would shocked rocks have offered shelter against harmful ultraviolet light at [a] time when Earth still lacked a protective atmosphere, asteroid and comet impacts would have created hydrothermal systems that could have helped sustain life by providing sources of heat, water, and nutrients.
Asteroid and comet strikes have devastated life on Earth, but in various other ways--by providing metals and water and, in this case, shelter--it's likely we wouldn't even be here without them.