Definition
A planet of the Sulfuris class is a terrestrial body with a very dense atmosphere dominated by carbon dioxide (CO₂), containing clouds of sulfur dioxide (SO₂). These planets are characterized by extreme surface temperatures, a strong greenhouse effect, and active geological dynamics, which exclude the presence of any known life.
Atmosphere
The atmosphere of a Sulfuris planet traps heat due to an intense greenhouse effect. The high concentration of CO₂ absorbs and retains infrared radiation emitted by the surface, while high atmospheric pressure raises surface temperatures to levels sufficient to keep some metals in a molten state. These conditions remain stable over geological timescales.
Chemical Processes
The clouds of sulfur dioxide contribute to the opacity of the atmosphere and participate in chemical cycles involving sulfuric acid precipitation. These interactions create a corrosive environment that alters surface rocks and influences atmospheric processes.
Volcanism
Sulfuris planets are associated with intense and persistent volcanic activity. The high sulfur dioxide content in the atmosphere suggests that large eruptions constantly renew the gaseous composition. The surface features calderas, recent lava flows, and fractures, indicating strong internal dynamics. Due to the absence of liquid water, classical erosional processes are lacking, resulting in abrupt reliefs and vast volcanic plains.
Past
Geological evidence indicates that Sulfuris planets may have temporarily held surface water in the past. This water evaporated due to stellar radiation. Hydrogen escaped into space, while the remaining oxygen interacted with crustal minerals or remained in the atmosphere as stable compounds.
Evolution
Sulfuris planets illustrate the evolution of a terrestrial body subjected to climatic imbalance. Their dense atmosphere, very hot surface, and active volcanism provide a natural framework to study the effects of a runaway greenhouse effect and the long-term transformations of planetary environments.