# Project Structure

Structure map for the Titans crate.

```text
Titans/
├── README.md                           # Project overview and usage
├── LICENSE                             # MIT license
├── ChangeLog.md                        # Version history
├── ComingSoon.md                       # Planned features
├── Contributing                        # Contribution guidelines
├── lastest_versions.sh                 # Restore wildcard dependency versions
│
├── src/
│   ├── main.rs                         # Entry point — Titan diagnostics: orbit, thick atmosphere, methane cycle
│   ├── lib.rs                          # Library root, TITANMASS (1.35e23 kg), radius 2 575 km, constants
│   │
│   ├── environment/                    # Surface environment
│   │   ├── mod.rs                      # Exports dust, radiation, thermal
│   │   ├── dust.rs                     # Tholin haze particles settling, organic sand grain transport
│   │   ├── radiation.rs                # Dense atmosphere shields surface — minimal GCR/particle flux at ground
│   │   └── thermal.rs                  # Surface 94 K uniformly, 1.5 atm N₂/CH₄ atmosphere, greenhouse + anti-greenhouse
│   │
│   ├── exosphere/                      # Atmosphere model (dense N₂/CH₄ atmosphere, not tenuous exosphere)
│   │   ├── mod.rs                      # Exports charging, escape, species
│   │   ├── charging.rs                 # Ionospheric interaction with Saturn magnetosphere, upper atmosphere
│   │   ├── escape.rs                   # Hydrodynamic escape of H₂, photochemical CH₄ destruction in upper atmosphere
│   │   └── species.rs                  # N₂ (95%), CH₄ (5%), C₂H₆, C₂H₂, HCN, tholin haze (>100 identified species)
│   │
│   ├── geodata/                        # Geographic reference data
│   │   ├── mod.rs                      # Exports coordinates, elevation, landing_sites, regions
│   │   ├── coordinates.rs              # Planetocentric lat/lon, IAU Titan-fixed frame
│   │   ├── elevation.rs                # Cassini RADAR altimetry/SAR-derived topography through opaque atmosphere
│   │   ├── landing_sites.rs            # Dragonfly target (Selk crater region), Huygens landing (Adiri)
│   │   └── regions.rs                  # Xanadu continent, Kraken/Ligeia/Punga Maria (north polar seas), Belet Sand Sea
│   │
│   ├── geology/                        # Surface and interior geology
│   │   ├── mod.rs                      # Exports craters, erosion, mountains, regolith, volcanism
│   │   ├── craters.rs                  # Menrva (392 km), Selk (90 km) — very few craters, young surface
│   │   ├── erosion.rs                  # Methane rain erosion, fluvial channels, coastal erosion at lake margins
│   │   ├── mountains.rs                # Mithrim Montes (~3.3 km), Doom Mons (cryovolcano candidate), ice ridges
│   │   ├── regolith.rs                 # Organic tholin-coated ice grains, water-ice bedrock beneath
│   │   └── volcanism.rs               # Possible cryovolcanism — Doom Mons/Sotra Patera, ammonia-water lavas
│   │
│   ├── interactions/                   # Gravitational interactions
│   │   ├── mod.rs                      # Exports earth_tides, saturns, orbital_dynamics
│   │   ├── earth_tides.rs              # Earth–Titan perturbation (negligible at 9.5 AU)
│   │   ├── saturns.rs                  # Saturn gravitational influence, 4:3 resonance with Hyperion
│   │   └── orbital_dynamics.rs         # Eccentric orbit (e = 0.029), tidal interaction with Saturn
│   │
│   ├── lighting/                       # Illumination model
│   │   ├── mod.rs                      # Exports eclipses, saturnshine, solar_position
│   │   ├── eclipses.rs                 # Saturn shadow transits, ring shadow bands, atmosphere scattering
│   │   ├── saturnshine.rs              # Negligible at surface — dense haze blocks all direct/reflected light
│   │   └── solar_position.rs           # ~0.1% surface illumination (through haze), 15.95 d orbital period
│   │
│   ├── missions/                       # Exploration missions
│   │   ├── mod.rs                      # Exports landers, orbiters, relay
│   │   ├── landers.rs                  # Huygens probe (landed 2005-01-14), Dragonfly rotorcraft (~2034 arrival)
│   │   ├── orbiters.rs                 # Cassini (127 Titan flybys, RADAR mapping), future orbiter concepts
│   │   └── relay.rs                    # Cassini relay for Huygens, Dragonfly direct-to-Earth link
│   │
│   ├── observation/                    # Remote observation
│   │   ├── mod.rs                      # Exports communications, saturn_view, navigation
│   │   ├── communications.rs           # Deep-space link budget, 9.5 AU light-time delay (~79 min)
│   │   ├── saturn_view.rs              # Saturn not visible from surface (opaque haze), RADAR mapping only
│   │   └── navigation.rs              # Atmospheric navigation, RADAR ground tracking, Doppler wind measurement
│   │
│   ├── physics/                        # Orbital and impact mechanics
│   │   ├── mod.rs                      # Exports collisions, orbit, rotation, tides
│   │   ├── collisions.rs               # Atmosphere decelerates impactors, few craters survive
│   │   ├── orbit.rs                    # a = 1 221 870 km, e = 0.0288, period 15.95 d, vis-viva
│   │   ├── rotation.rs                 # Synchronous rotation, super-rotation of atmosphere (~4%)
│   │   └── tides.rs                    # Tidal deformation of ice shell, ocean detection via tidal Love number k₂
│   │
│   ├── rendering/                      # Visual rendering pipeline
│   │   ├── mod.rs                      # Exports dust, materials, shaders
│   │   ├── dust.rs                     # Tholin haze particle rendering, orange atmospheric scattering
│   │   ├── materials.rs                # PBR organic sand (dunes), methane lakes (specular), icy bedrock
│   │   └── shaders.rs                  # GPU shader programs — atmospheric haze layers, methane lake reflection
│   │
│   ├── resources/                      # Extractable resources
│   │   ├── mod.rs                      # Exports minerals, regolith, water_ice
│   │   ├── minerals.rs                 # Organic tholin deposits, complex prebiotic chemistry products
│   │   ├── regolith.rs                 # Organic sand grains, tholin-coated pebbles, Huygens surface data
│   │   └── water_ice.rs               # Water-ice bedrock beneath organics, subsurface ammonia-water ocean
│   │
│   ├── surface/                        # Surface mapping
│   │   ├── mod.rs                      # Exports heightmaps, mapping, zones
│   │   ├── heightmaps.rs               # Cassini RADAR/SAR altimetry through opaque atmosphere
│   │   ├── mapping.rs                  # RADAR-dark (smooth) and RADAR-bright (rough) terrain maps, VIMS composites
│   │   └── zones.rs                    # Equatorial dune seas, polar lake districts, Xanadu highlands, labyrinth terrain
│   │
│   ├── temporal/                       # Time systems
│   │   ├── mod.rs                      # Exports calendar, epoch, time_scale
│   │   ├── calendar.rs                 # Titan calendar — 15.95 d orbital period, Saturn year (29.5 yr), methane seasons
│   │   ├── epoch.rs                    # J2000 epoch, Huygens landing (2005-01-14), Dragonfly arrival timeline
│   │   └── time_scale.rs              # TDB/UT1/TAI conversions at 9.5 AU light-time delay
│   │
│   └── terrain/                        # Terrain mesh generation
│       ├── mod.rs                      # Exports lod, mesh, texturing
│       ├── lod.rs                      # Level-of-detail streaming for dune fields and lake shorelines
│       ├── mesh.rs                     # Spherical mesh, radius 2 575 km (second-largest moon)
│       └── texturing.rs               # Cassini RADAR/VIMS composite drape, organic surface textures
│
├── tests/                              # Integration tests
│   ├── environment_tests.rs            # Tests 1.5 atm pressure, 94 K surface, tholin settling rate
│   ├── exosphere_tests.rs              # Tests N₂/CH₄ atmospheric profile, photochemical destruction rate
│   ├── geodata_tests.rs                # Tests coordinate transforms, Kraken Mare shoreline, Selk crater
│   ├── geology_tests.rs                # Tests methane fluvial erosion, dune morphology, crater scarcity
│   ├── interactions_tests.rs           # Tests Hyperion 4:3 resonance, Love number k₂ ocean detection
│   ├── lighting_tests.rs              # Tests haze attenuation (~0.1% surface), Saturn shadow timing
│   ├── missions_tests.rs              # Tests Huygens descent profile, Cassini flyby parameters
│   ├── observation_tests.rs            # Tests RADAR mapping resolution, Doppler wind measurement
│   ├── physics_tests.rs                # Tests orbital period, atmospheric super-rotation, tidal amplitude
│   ├── rendering_tests.rs              # Tests haze scattering model, methane lake specular reflection
│   ├── resources_tests.rs              # Tests tholin composition, methane lake volume estimates
│   ├── surface_tests.rs                # Tests RADAR altimetry resolution, terrain unit classification
│   ├── temporal_tests.rs               # Tests methane season cycle, epoch conversions
│   └── terrain_tests.rs               # Tests mesh accuracy, LOD transitions at lake shorelines
│
└── examples/                           # Runnable examples
    ├── check_landing_site.rs           # Evaluate Dragonfly Selk crater region for rotorcraft operations
    ├── crater_sim.rs                   # Menrva/Selk formation through dense atmosphere impactor deceleration
    ├── eclipse_sim.rs                  # Saturn shadow transit timing through opaque atmosphere
    ├── exosphere_sim.rs                # N₂/CH₄ atmospheric column, photochemical haze production
    ├── saturn_observation.rs           # Saturn hidden by haze — RADAR-only observation geometry
    ├── orbital_sim.rs                  # 15.95-day orbit propagation, Hyperion resonance effects
    ├── radiation_sim.rs                # Atmospheric shielding — minimal surface radiation dose
    ├── resource_survey.rs              # Tholin organic deposit and methane lake distribution mapping
    └── tidal_effects.rs               # Tidal Love number — subsurface ocean detection via deformation
```
