Structural Mechanics of Cryogenic Ice as Planetary Bedrock: A Rock-Analogue Framework for Dwarf Planet Surface Dynamics and the Methane Sintering Paradox

The 2015 New Horizons flyby of Pluto revealed wind-sculpted methane ice dune fields across the Sputnik Planitia basin — a discovery that contradicted expectations for a body with atmospheric pressure approximately 100,000 times thinner than Earth's. While the dune-formation mechanism via sublimation-assisted saltation is broadly accepted, an unresolved problem persists: methane ice at Pluto's ambient temperature of approximately 40 K should undergo sintering, fusing individual grains into a rigid, unflowable crust rather than behaving as loose mobile sand. This paper applies a structural engineering framework to this problem, treating Pluto's water-ice crust as a mechanical analogue for terrestrial igneous bedrock and its volatile methane-nitrogen ices as sedimentary analogues. We formalise the mechanical property equivalences using Young's modulus, compressive strength, tensile strength, Brinell hardness, and plasticity data across temperature ranges. We demonstrate that water ice at 40 K exceeds granite in compressive strength and thermal shock resistance by approximately a factor of three, validate this through a comparative thermodynamic energy calculation (2,962 J required to destroy 1 g of Pluto surface water ice versus 1,188 J to melt 1 g of granite on Earth), and introduce a soapstone control-variable thought experiment to isolate fluid-dynamic dune formation from thermodynamic sublimation. We identify the sintering paradox as the primary unresolved gap in the current model, and argue that a structural engineering lens provides a productive framework for addressing it.