麻豆淫院

A new paper led by a York University professor and in Nature Astronomy introduces a simple theoretical framework to describe the evolution of the coupled interior鈥揳tmosphere system of hot rocky exoplanets known as "lava planets."

"Lava planets are in such extreme orbital configurations that our knowledge of rocky planets in the solar system does not directly apply, leaving scientists uncertain about what to expect when observing lava planets," says first author Charles-脡douard Boukar茅, Assistant Professor in York University's Department of 麻豆淫院ics and Astronomy in the Faculty of Science.

"Our simulations propose a conceptual framework for interpreting their evolution and provide scenarios to probe their internal dynamics and chemical changes over time. These processes, though greatly amplified in lava planets, are fundamentally the same as those that shape rocky planets in our own solar system."

Exotic worlds may unveil processes driving planetary evolution

Lava planets are Earth- to super-Earth鈥搒ized worlds orbiting extremely close to their host stars, completing an orbit in less than a single Earth day. Much like Earth's moon, they are expected to be tidally locked, always showing the same face to their star. Their dayside surfaces reach such extreme temperatures that silicate rocks melt鈥攁nd even vaporize鈥攃reating conditions unlike anything in our solar system. These exotic worlds, easily observable due to their ultra short orbital period, provide unique insights into the fundamental processes that shape planetary evolution.

Probing planetary interiors through atmosphere and surface properties

The study combines expertise in geophysical fluid mechanics, exoplanetary atmospheres, and mineralogy to explore how the compositions of lava planets evolve through a process akin to distillation. When rocks melt or vaporize, elements such as magnesium, iron, silicon, oxygen, sodium, and potassium partition differently between vapor, liquid, and solid phases. The unique orbital configuration of lava planets maintains vapor鈥搇iquid and solid鈥搇iquid equilibria over billions of years, driving long-term chemical evolution.

The paper, "The role of interior dynamics and differentiation on the surface and atmosphere of lava planets," was co-authored by Daphn茅 Lemasquerier (University of St Andrews), Nicolas B. Cowan (McGill University), Lisa Dang (University of Waterloo), Henri Samuel, James Badro, Aur茅lien Falco and S茅bastien Charnoz (Universit茅 Paris Cit茅).

Using unprecedented numerical simulations, the team predicts two end-member evolutionary states:

• Fully molten interior (likely young planets): The atmosphere mirrors the bulk planetary composition, and heat transport within the molten interior keeps the nightside surface hot and dynamic.
• Mostly solid interior (likely older planets): Only a shallow lava ocean remains on the dayside, and the atmosphere becomes depleted in elements such as sodium, potassium, and iron.

Testing hypotheses with the James Webb Space Telescope

Boukar茅 explains that this research on lava exoplanets began as a highly exploratory effort with few initial expectations. It builds on a novel modeling approach he developed to study molten rocky planets in collaboration with colleagues at the Institute de 麻豆淫院ique du Globe de Paris, Universit茅 Paris Cit茅, published in Nature earlier this year.

What began as an exploratory study has since opened a promising new line of research. The predictions outlined in this work helped secure 100 hours of observation time on the James Webb Space Telescope (JWST)鈥攖he most advanced infrared observatory ever built, featuring a 6.5鈥憁eter segmented mirror and ultra鈥憇ensitive instruments capable of probing the earliest galaxies and the atmospheres of distant exoplanets with unprecedented precision. These upcoming JWST observations, led by co-author Prof. Dang, will directly test the theoretical framework proposed in this study.

"We really hope we can observe and distinguish old lava planets from young lava planets. If we can do this, it would mark an important step toward moving beyond the traditional snapshot view of exoplanets," says Boukar茅.