The compressive strength a crust holds a mountain up with, pascals.
Peak relief scales as strength / (ρ g): a mountain is a column of rock
standing on rock, and it stops growing when its own base yields. The constant
is calibrated on Olympus Mons — 21.9 km on Mars, where ρg is 14,600 — which
puts it at 3.2 × 10⁸ Pa, the right order for basalt in compression.
Earth comes out at 5.9 km against Everest's 8.8, and the understatement is the model rather than a fitting error: the Himalaya are still being pushed up by a collision, and a static strength limit describes what a crust can hold, not what a convergence is currently doing to it.
Cryogenic ice counts as rock here and gets no constant of its own. At 90 K water ice has a compressive strength within a factor of two of basalt, which is why Iapetus stands a 20 km ridge on a 735 km moon and why that is right rather than a bug.
universe/src/grammar.ts:67