The Solar System chose fire over ice from the very beginning

Ancient iron meteorites reveal that some of the Solar System’s first solid bodies were built mostly from tiny heat-forged rock beads called chondrules, while water-rich dust was largely excluded. The finding pushes this selective planet-building process back to within the Solar System’s first million years. The Solar System chose fire over ice from the very beginning.

As the young Solar System began assembling solid objects such as planets, moons, and protoplanets, two major types of material were available. One was chondrules, millimeter-sized pieces of rock formed at high temperatures. The other was matrix, a cold, fine-grained dust rich in water ice and organic material.

New research led by Yale University suggests that the Solar System strongly favored the heat-formed material almost immediately. Researchers have found the first geochemical evidence showing that chondrules were already being preferentially incorporated into solid bodies during the Solar System’s first million years. Until now, scientists had only been able to document this type of sorting in objects that formed 2 to 4 million years after the Solar System began.