We don’t really know what the very early Earth looked like because the landscape was always being recycled. Zircons, however, are hard enough that they may survive, containing clues about the previous environments.
Using zircon oxygen isotopes, researchers previously discovered that liquid water covered parts of our planet some 4.3 billion years ago, suggesting the surface cooled just a few hundred million years after our planet’s formation. And just last year, researchers found what they believe might be hints of early life in the form of carbon-rich inclusions in 4.1-billion-year-old zircons.
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Some zircons contain the chemical signatures of rocks weathered by water to form clay. Other zircons bear the signatures of dissolved minerals that crystallize to form rocks like chert or banded iron formations in lakes or oceans. Still others have the signature of a process known as serpentinization, so called for its snake-skin-like texture and color. During this process, water reacts with rocks enriched in iron and magnesium, incorporating itself into the mineral structures. Maya Wei-Haas, “4-Billion-Year-Old Crystals Offer Clues to the Origins of Life” at National Geographic
We know that life got started soon after the planet cooled but the conditions remain largely a mystery. It’s been a few good decades for hypotheses as a result.
See also: Rob Sheldon: Why zircons might be evidence for life at earliest formation of Earth
and
“Compelling new evidence” claimed for comets generating phosphates for earliest life