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Crater degradation

Chosen by "type" in degradation.

Type What it is
freshness Scales depth and rim height linearly with freshness, down to a cutoff depth ratio at the end of a crater's lifetime.
none Craters stay fresh, optionally all with one depth to diameter ratio.
diffusion Wears craters down by topographic diffusion, from each crater's diameter and age.

freshness

Scales depth and rim height linearly with freshness, down to a cutoff depth ratio at the end of a crater's lifetime.

Key Type Default Range Unit Description
cutoff_depth_ratio number 0.04 (0, 0.1) Depth over diameter of a crater at the end of its lifetime, in (0, 0.1); lower values let old craters wear shallower.
Every key with its default 
{
    "type": "freshness",
    "cutoff_depth_ratio": 0.04
}

none

Craters stay fresh, optionally all with one depth to diameter ratio.

Key Type Default Range Unit Description
depth_ratio number, optional null (0, inf) Depth over diameter given to every crater, positive; unset keeps each crater's fresh depth for the body.
Every key with its default 
{
    "type": "none",
    "depth_ratio": null
}

Used in: example_craters_degradation_none

diffusion

Wears craters down by topographic diffusion, from each crater's diameter and age.

Key Type Default Range Unit Description
diffusivity one of matched, fassett_2022_hartmann, fassett_2022_trask, fassett_thomson_2014, fassett_thomson_2014_calibration, power_law "matched" Model of the diffusion age each crater has from its diameter and age; on Mars only power_law is allowed.
reach_radii number 3.0 Distance from the centre, in crater radii, out to which the diffused profile is solved and held at 0; at least the fresh profile's reach.
power_law: The diffusivity used when the diffusivity model is power_law.
Key Type Default Range Unit Description
coefficient number 1.0 (0, inf) m^2/Myr Diffusivity of a 1 km crater, in m^2/Myr, positive; higher values wear craters down faster.
exponent number 0.0 Exponent of the diameter in coefficient (D / 1 km)^exponent; 0 gives the same diffusivity for every crater size.
min_diameter number 0.0 [0, inf) m Diameter in metres below which the diffusivity is held at its value at this diameter; not negative.
Every key with its default 
{
    "type": "diffusion",
    "diffusivity": "matched",
    "power_law": {
        "coefficient": 1.0,
        "exponent": 0.0,
        "min_diameter": 0.0
    },
    "reach_radii": 3.0
}

Used in: example_ages_fresh, example_ages_steady_state, example_ages_uniform, example_albedo_blast_zone, example_albedo_fresh_crater, example_albedo_new_crater, example_craters_degradation_diffusion, example_craters_texture