Some rocky planets might not be 'dead rocks' at all—they could actually be growing or shrinking like living things.
April 17, 2026
Original Paper
Energy-Driven Radius Evolution of Chthonian Planets: A Viscoelastic Maxwell Framework with Applications to Earth
SSRN · 6578925
The Takeaway
We usually think of rocky planets like Earth as static spheres that just cool down over billions of years. But 'Chthonian' planets—the rocky cores left behind when gas giants lose their atmosphere—behave differently. This new framework shows these planets expand or contract based on 'internal energy reservoirs' and the thickness of their mantles. They are dynamic, 'breathing' worlds whose size changes significantly over geological time. This means that when we look for 'Earth 2.0,' we can't just assume a planet's size tells us its age or history. It adds a whole new layer of 'life' to what we thought were just cold, dead chunks of stone.
From the abstract
Chthonian planets—dense rocky or metallic remnants of gas giants stripped of their gaseous envelopes—experience extreme internal pressures and energy densities, making their structural evolution fundamentally different from classical terrestrial planets. We aim to develop a physically grounded framework to describe energy-driven radius evolution in such bodies and to understand how internal properties control their structural changes. Using mass conservation, hydrostatic equilibrium, and the vir