Searching Mars' surface for evidence of prehistoric microbial life is one of NASA's Perseverance rover's primary objectives.
Over the years, rovers and orbiters have discovered mountains of proof suggesting the Red Planet used to be much bluer and home to rivers and oceans.
Before it could have evolved into the sophisticated kind we see today, life may have begun in those idyllic early times and perished as the planet dried up.
NASA has been searching for evidence of this ancient life, and Perseverance has recently begun its mission to look for microbial fossils
Microbes frequently appear in habitats that were previously thought to be too hostile for life, from the driest deserts to subglacial lakes beneath hundreds of meters of arctic ice.
Earth's enormous microbial biosphere lives in rock fissures and cracks thriving on geochemical interactions between rock and water.
Water undergoes radiolysis when radioactive elements in rocks break it into hydrogen and oxygen atoms, which microorganisms can subsequently use as fuel.
Microbes with this capability have been discovered on Earth living up to a mile below the surface, and it's possible that something similar is happening on Mars.
Mars is also much less tectonically active than Earth, which means any bacteria may potentially graze there for billions of years without being disturbed.
The scientists discovered all three of these components in meteorites of various types in amounts that might sustain microbial ecosystems.
The most favorable environment for life was a type of rock called regolith breccias, which is older than 3.6 billion years.