The Vaporized Silicate Atmosphere and Lava Oceans of Exoplanet K2-141b
Subsequent high-precision radial velocity measurements obtained with instruments such as the High Accuracy Radial Velocity Planet Searcher (HARPS-N) have allowed scientists to constrain the planet's fundamental physical dimensions with high accuracy. K2-141b possesses a radius of approximately 1.51 Earth radii and a mass roughly 5.08 times that of Earth. These values translate to an exceptional bulk density of approximately 8.2 grams per cubic centimeter, significantly higher than Earth's density of 5.51 grams per cubic centimeter. This elevated density indicates a terrestrial internal structure dominated by a massive, high-density metallic iron-nickel core surrounded by a compressed, dense silicate mantle.
Orbital Mechanics and Tidal Locking Extremes
The orbital geometry of K2-141b is defined by its extreme proximity to its host star. The planet orbits at a semi-major axis of just 0.00716 astronomical units—equivalent to roughly 1.07 million kilometers, or less than one-eightieth of Mercury's distance from the Sun. At this proximity, K2-141b completes a single orbit in approximately 6.7 hours (0.28 Earth days). This rapid orbital cadence subjects the body to immense gravitational tidal forces that have fully synchronized its rotational period with its orbital period.
As a consequence of tidal locking, K2-141b maintains a permanent day side facing the central star and a permanent night side turned toward deep space. This persistent illumination gradient creates a stark thermodynamic divide across the planetary surface. Without a thick, insulating volatile atmosphere like that of Earth or Venus to redistribute heat efficiently via advection, heat remains concentrated overwhelmingly on the star-facing hemisphere, maintaining an extreme thermal equilibrium that actively reshapes the planet's geology.
Thermal Architecture and Sub-Stellar Magma Ocean
Spectroscopic modeling and thermal radiation calculations reveal that the sub-stellar point on K2-141b reaches equilibrium temperatures exceeding 3,000 Kelvin (approximately 2,700 degrees Celsius). Temperatures of this magnitude far surpass the melting points of virtually all known rock-forming minerals, including olivine, pyroxene, and quartz. Consequently, the illuminated hemisphere does not possess a solid crust; instead, it is covered by a massive, global lava ocean estimated to be several hundred kilometers deep.
This molten sea is composed of liquid silicates, iron, sodium, and magnesium oxides. Near the sub-stellar point, intense convective updrafts drive molten material from the deep interior to the surface, creating a churning, glowing incandescent fluid body. Toward the edges of the illuminated hemisphere—the planetary limb—the incident stellar flux decreases, allowing the liquid rock to cool partially and form fractured, dynamic slabs of semi-solid basaltic slag that float atop the incandescent liquid beneath.
Silicate Vapor Dynamics and Supersonic Winds
The intense thermal energy on the day side of K2-141b drives a surface pressure regime radically different from standard planetary atmospheres. At temperatures exceeding 2,000 Kelvin, the liquid rock surface actively evaporates directly into space. Silicate minerals undergo thermal decomposition, releasing atomic and molecular vapor species including silicon monoxide (SiO), silicon dioxide (SiO2), atomic sodium (Na), potassium (K), and iron (Fe).
This localized surface evaporation forms a thin, volatile-rich rock-vapor atmosphere over the illuminated hemisphere. The atmospheric pressure at the sub-stellar point is substantially higher than the near-vacuum conditions of the night side. This intense pressure differential creates a planetary-scale atmospheric engine, driving ultra-high-speed winds from the hot day side toward the cold night side. Fluid dynamics simulations indicate these silicate-laden winds reach supersonic velocities exceeding 1.75 kilometers per second (over 6,300 kilometers per hour), sweeping vaporized mineral gas westward across the planetary surface.
Nocturnal Cryo-Precipitation and Liquid Rock Cycles
As the supersonic rock-vapor winds pass over the terminator line—the transition zone between the permanent day and permanent night—the ambient temperature drops precipitously. On the night side, unshielded by stellar radiation, surface temperatures plunge to below 40 Kelvin (minus 233 degrees Celsius). This extreme cold causes the transported silicate vapor to freeze rapidly out of the atmosphere.
This phase transition gives rise to a planetary rock cycle operating entirely through inorganic phase changes. In the atmosphere above the terminator, silicon dioxide and sodium condense into microscopic mineral droplets and crystalline grains, falling back toward the surface as mineral hail and quartz snow. Over geological timescales, these mineral deposits build up massive, frozen rock glaciers on the night side. Under the pressure of their own weight and the steady push of tectonic gravity, these night-side rock glaciers slowly flow back toward the day side, where they re-melt upon reaching the high-temperature zone, re-entering the sub-stellar lava ocean and maintaining a closed, planet-wide mineral circulation loop.
