Vol. 670
10. Planets and planetary programs
The Curie line in protoplanetary disks and the formation of Mercury-like planets
Protoplanetary disks imaged within the optical or millimeter vary present wealthy ring-like buildings, which have been attributed to a wide range of processes, together with embedded planets, snow traces, the pile-up of fabric at stress maxima, or different native instabilities. Snow traces, specifically, are favored places for the triggering of planetesimal formation. Bogdan et al. right here suggest the brand new idea of a Curie line in protoplanetary disks. Laboratory measurements, during which chondritic materials is heated to 1400 Okay in a hydrogen ambiance and analyzed with Mössbauer spectroscopy and magnetometry, point out the formation of metallic iron from silicates close to temperatures of 1200 Okay or decrease. This means that inward drifting materials in protoplanetary disks have to be a supply of metallic iron. The presence of a disk magnetic subject then makes the magnetic aggregation of mud aggregates attainable, a mechanism beforehand proposed for the selective development of iron-rich our bodies by streaming instabilities. Nevertheless, coincidentally, the temperature of metallic iron formation from silicates is much like the Curie temperature (1041 Okay), above which iron loses its everlasting magnetic properties and turns into paramagnetic. Subsequently, contained in the Curie line, the big magnetic clusters will dissolve however generate a big density of small particles, probably inflicting a “visitors jam” (analogous to the method thought to happen at ice snow traces), which could even be useful for planetesimal formation by gravitational instability. The Curie line might thus seem as a dividing line between two attainable formation processes for iron-rich, Mercury-like planets.
