From the first solids of the Solar System to planets: the decisive role of extreme and violent cooling

A sudden and extreme cooling, driving material diversity…
For decades, models have described the formation of the first minerals as a slow condensation process governed by chemical equilibrium: as it cooled gradually, the gas of the solar nebula would have given rise to well-ordered mineral assemblages. However, this view struggles to account for the diversity of meteorites—ancient fragments that record the earliest stages of planetary formation.

The researchers explored an alternative hypothesis. Using a new model that describes the condensation of solar gas out of equilibrium, they show that in an environment with intense heating and rapid cooling, matter does not have time to follow the laws of thermodynamic equilibrium. Instead, it becomes “frozen” in transient states… and minerals that should not appear at equilibrium naturally emerge under non-equilibrium conditions.

This framework yields only three major types of mineral assemblages, consistent with the three main families of meteorites known in the Solar System. The diversity of planetary materials may therefore not necessarily result from large-scale compositional variations in the solar nebula, but could instead be largely explained by local formation conditions—particularly the rapidity of cooling episodes. This points to a highly dynamic solar nebula, marked by violent motions and intense heating events within the first hundred thousand years.

…And the early incorporation of oxygen into the first solids
These results also shed new light on another major question: the origin of oxygen and water in terrestrial planets. In classical models, the formation of oxidized or hydrated minerals from a gas of solar composition is difficult to explain without invoking external inputs. Here, by contrast, the researchers show that during rapid cooling, certain elements remain available at low temperatures and can be incorporated into forming solids. This mechanism thus provides a natural pathway for incorporating oxygen—and potentially water—from the very earliest stages of planetary material formation.