First evidence for silica condensation within the solar protoplanetary disk

Significance The oldest solar system solids dated are refractory inclusions [Ca-Al–rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs)], which occur in chondritic meteorites and provide records of high-temperature processes in the early solar system. An ultrarefractory CAI and the silica-phase quartz occur in an AOA from the carbonaceous chondrite Yamato-793261, indicating formation over a temperature range exceeding 650 K. The minerals have16 O-rich compositions consistent with the nebular setting associated with refractory inclusions. This AOA provides direct evidence that silica condensed from gas in a CAI/AOA-forming region in our solar system indicates that gas became Si-rich as Mg condensed and may explain the origin of silica detected from infrared spectroscopy of T Tauri and asymptotic giant branch stars.