It’s life, but not as we know it. The oldest fossil ever discovered on Earth shows that organisms were thriving 4.2 billion years ago, hundreds of millions of years earlier than previously thought.

The microscopic bacteria, which were smaller than the width of a human hair, were found in rock formations in Quebec, Canada, but would have lived in hot vents in the 140F (60C) oceans which covered the early planet.

The discovery is the strongest evidence yet that similar organisms could also have evolved on Mars, which at the time still had oceans and an atmosphere, and was being bombarded by comets which probably brought the building blocks of life to Earth.