Which tiny part of Earth contains every known life form?

1% of the Earth’s mass contains all known life in the known universe

To call our planet one grain of sand on the beach that is the universe would be to vastly overstate its size. Yet however infinitesimal in the unfathomably grand scheme of things, Earth is home to all known life in the universe — and all of that life has been found in just 1% of the planet’s mass. That tiny fraction refers to Earth's crust, which is 25 miles deep and has been home to every life-form ever known. There is no evidence of intelligent life beyond our pale blue dot, although many scientists and civilians alike tend to believe (or at least hope) that it’s out there. 

Beneath the crust lies the planet’s mantle, which contains solid rocks, minerals, and areas of semisolid magma. Even deeper, there’s the Earth’s core, which is extremely hot — parts are as hot as the surface of the sun — and mostly made of metal, which isn’t exactly conducive to nurturing life. Beyond our planet, astronomers have long sought to discover life on Mars, although Venus (often called Earth’s twin) is also looking promising when it comes to aliens, or at least alien microbes. Both Mars and Venus sit within our sun’s “habitable zone,” which is defined as the distance from a star that enables liquid water to exist on a planet’s surface, like our precious crust.