IAU descriptor term
Regiones in the Solar System
Regio is the term planetary geologists use for a large area distinguished by its brightness or colour. 51 named features carry it, across 7 of the 14 mapped worlds, the largest being Eistla Regio on Venus at 8,015 km.
Where they are
The largest regiones anywhere
Ranked across every mapped world, by catalogued diameter.
1Eistla RegioVenus8,015 km2Ovda RegioVenus5,280 km3Marius RegioGanymede4,940 km4Galileo RegioGanymede4,439 km5Melotte RegioGanymede4,100 km6Ulfrun RegioVenus3,954 km7Nicholson RegioGanymede3,900 km8Perrine RegioGanymede3,800 km9Atla RegioVenus3,200 km10Barnard RegioGanymede3,200 km11Beta RegioVenus2,869 km12Colchis RegioIo2,860 km13Phoebe RegioVenus2,852 km14Thetis RegioVenus2,801 km15Media RegioIo2,628 km16Falga RegioEuropa2,500 km17Balgatan RegioEuropa2,500 km18Hyndla RegioVenus2,300 km19Dione RegioVenus2,300 km20Annwn RegioEuropa2,300 km21Laufey RegioVenus2,100 km22Powys RegioEuropa2,000 km23Argadnel RegioEuropa1,900 km24Alpha RegioVenus1,897 km25Themis RegioVenus1,811 km26Tara RegioEuropa1,780 km27Bell RegioVenus1,778 km28Dyfed RegioEuropa1,750 km29Imdr RegioVenus1,611 km30Bosphorus RegioIo1,607 km
What they are named after
Naming themes are set per world, so one descriptor can draw on very different sources depending on where it sits. Across all 51 regiones, 20 categories appear.
Greek17Norse5American5Celtic5Wales3Italy2Mari1Norway1