Life surviving on early Earth

Within 100 million years of being formed, the young Earth was hit by a rogue planet , the debris from which ultimately formed the Moon, melting the Earth’s surface. For the next 600 million years the planet was bombarded by debris and meteors that heated up both land and oceans. Few, if any, rocks remain from before the end of this era, with the oldest currently known being from 4.03 Gyr ago.

The earliest know isotopic evidence for life is at 3.8 Gyr, although its findings remain controversial.

For years geological models suggested that the oceans, where life is thought to have originally formed were sterilized during this period.

This left two uncomfortable conclusionsâmdash;that life originated more than once, or that life started elsewhere in the solar system.

This story began to change with the discovery of zircons that pre-date the late bombardment. Zircons are telltale mineral inclusions in ancient rocks, and the evidence from them supported the idea that between 4.38â3.85 Gyr the Earth had liquid water, crustal recycling, a granitoid crust and low-temperature processes occurring at the boundaries of tectonic plates.

Abramov and Mojzsis’s research now suggests that the conditions were never severe enough to sterilize Earth, eliminating the need for more esoteric solutions for how life survived on the early Earth.

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