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Validation: src/calliope/structure.py

This page tracks the @pytest.mark.reference_pinned tests that anchor the behaviour of calliope.structure against a published source.

Test id Reference Source page Scope
tests/test_structure.py::test_calculate_mantle_mass_recovers_wang_2018_earth_core_fraction Wang, Lineweaver & Ireland (2018)1, arxiv:1708.08718: Earth core mass fraction 32.5 +/- 0.3 wt% arxiv:1708.08718 Pins the Earth-like mantle mass against the published core mass fraction and verifies the result lies in the 1e24 to 1e25 kg envelope expected for an Earth-mass planet.

Re-derivation note

structure.calculate_mantle_mass computes mantle mass by subtracting the core mass from the total planetary mass. The core mass is the volume of a sphere of radius core_frac * R_planet multiplied by a core density derived from Earth: core_rho = 3 * earth_fm * M_earth / (4 pi * (earth_fr * R_earth)^3) with earth_fm = 0.325 and earth_fr = 0.55 from Wang et al. (2018)1.

For Earth-like input (R = R_earth, M = M_earth, core_frac = 0.55), the construction is degenerate: the core density times the Earth-radius core volume reproduces the cited 0.325 mass fraction, so the mantle equals (1 - 0.325) * M_earth = 0.675 * M_earth ~ 4.03e24 kg.

Scale: a regression that swaps the r^3 core-volume factor for r^2 would land at ~3e18 kg, six orders of magnitude below the correct value. The test's scale guard 1e24 < mantle < 1e25 brackets the correct order and fails on any factor-of-10 unit slip.

Anchor type

Published benchmark + analytical limit. The Wang+2018 cite is the published-benchmark anchor; the conservation closure M_mantle + M_core = M_planet is asserted separately in test_calculate_mantle_mass_closure_holds_for_earth_like as the analytical-limit second-line check.

Cross-references

  • src/calliope/structure.py line 50: cites arxiv:1708.08718 for Earth core mass fraction 0.325.
  • PROTEUS src/proteus/orbit/satellite.py uses the same Earth core fraction in the satellite angular-momentum decomposition; both codes are pinned against the same source.

References

  1. H. S. Wang, C. H. Lineweaver, T. R. Ireland, The elemental abundances (with uncertainties) of the most Earth-like planet, Icarus, 299, 460-474, 2018. SciX. ↩↩