Reconstructed setting· The columns of time

Hadean world

4.54 Ga → 4.03 Ga

This backdrop shows the Hadean: plumes of hot gas over molten ground, with no land, no relief and no horizon drawn.

Backdrop representing a world whose surface was molten: plumes of hot gas above a melted ground, with no emergent land, no relief and no horizon drawn.

What the evidence shows

The surface was held molten by the energy of accretion and then by the giant impact that formed the Moon, and no rock survives from it. Thinner vapour plumes succeed the denser ones, the oxygen isotopes of Hadean zircons recording interaction with liquid water at low temperature before 4.3 billion years: the planet cooled enough to possess oceans earlier than had been estimated. The oldest preserved fragment of crust is a 4.4-billion-year-old zircon from the Jack Hills, that is, a mineral grain and not a landscape.

Bounds and conventions

The composition reconstructs a world of which no landscape survives. What it represents proceeds from chemistry and modelling and not from an outcrop, and the absence of a drawn horizon expresses that limit: the shape of a molten surface is unknown, its temperature is not.