Lava Worlds & Nightside Volcanoes on K2-141 b

In the vast catalog of discovered exoplanets, few environments are as extreme as the "lava world." SETI Institute host Dr. Moiya McTier recently sat down with ETH Zurich geoscientist Dr. Claire Marie Guimond to discuss K2-141 b, a rocky planet located approximately 200 light-years away. Unlike Earth, this planet orbits its host star so closely that its surface temperature reaches roughly 2,000 degrees Celsius. 

At these temperatures, rock cannot remain solid. Instead, the surface becomes a molten landscape, potentially featuring oceans of liquid magma. While astronomers have detected dozens of these worlds, K2-141 b is particularly notable for its short orbital period, providing a robust signal for terrestrial telescopes.

Modeling the Interior of a Distant Rock

Studying a planet hundreds of light-years away requires a blend of observational data and complex theoretical physics. Dr. Claire Marie Guimond and her team used mantle convection models (the process in which solid rock moves slowly due to internal heat) originally designed to study Earth's interior.

Dr. Guimond explained that geoscientists rely on the principle that physics and chemistry are universal. By inputting known parameters such as the planet's mass and radius, researchers can toggle "levers" in their models to explore unknown variables. These variables include:

• Radiogenic heating: Heat produced by the decay of elements like uranium and thorium. 
• Basal heating: The transfer of heat from the planet's iron core into its mantle.
• Melt intrusion: The percentage of molten rock that successfully breaks through the surface to form a volcano rather than remaining trapped underground.

K2-141 b is approximately 1.5 times Earth's radius but significantly denser, suggesting it has a much larger iron core.

The Paradox of Nightside Volcanism

One of the most striking findings of Dr. Guimond’s research involves the planet's tidal locking. Because K2-141 b is so close to its orange K-type star, one side permanently faces the heat while the other remains in eternal darkness.

While the "dayside" is a continuous lake of molten lava, the "nightside" is incredibly cold. However, the mantle convection model suggests that the nightside is not geologically dead. Instead, it is likely punctuated by active volcanoes.

This occurs because internal energy is transferred through the planet's interior. On the dayside, a massive plume of hot material rises, while on the nightside, cooler material sinks back down. This creates a convergence zone near the terminator, the line between light and dark, facilitating a process similar to Earth's subduction, in which the crust is recycled back into the mantle.

Evolution and the Search for Rock-Vapor Atmospheres

The long-term evolution of K2-141 b depends heavily on this recycling mechanism. If the planet can return volcanic gases to its interior, it may sustain geological activity for billions of years.

A major focus for the scientific community now is the potential for a "rock-vapor atmosphere". In these extreme conditions, minerals such as silicon monoxide or magnesium oxide can sublimate into the gaseous state. Dr. Guimond noted that data from the James Webb Space Telescope (JWST) is currently being analyzed to look for signatures of these exotic gases.

Understanding these planets is essential for the SETI Institute and the broader scientific community to determine the "typical" state of rocky planets in the galaxy. By studying the most extreme examples, researchers can better understand the forces that shaped our own world.

Watch the full SETI Live conversation here. Read the full scientific paper.

Final questions

1. Could lava worlds like K2-141 b help scientists understand how rocky planets form and evolve?

Yes. Extreme planets like K2-141 b serve as natural laboratories for studying planetary geology under conditions that are impossible to recreate on Earth. By comparing these molten worlds with Earth and other rocky planets, scientists can better understand how planetary interiors, crusts, and atmospheres evolve over time.

2. What would volcanic eruptions on K2-141 b actually look like?

Volcanoes on K2-141 b could erupt molten rock at temperatures far hotter than lava on Earth. Instead of water vapor and familiar volcanic gases, eruptions may release vaporized rock minerals such as silicon monoxide, creating glowing plumes and exotic weather unlike anything in our solar system.

3. How could the James Webb Space Telescope change what we know about lava planets?

JWST can analyze the chemical fingerprints of exoplanet atmospheres in unprecedented detail. If scientists detect rock-vapor gases around K2-141 b, it would provide the strongest evidence yet that some rocky planets possess atmospheres composed of evaporated rock rather than traditional gases like nitrogen or oxygen.