Mars

Construction

The globe is rendered in Three.js at the IAU equatorial radius (3,396.2 km, scaled to scene units) and built as a true oblate spheroid at the polar/equatorial ratio 0.9941111 (flattening 0.00589): each texture row is placed at its own planetocentric latitude on the ellipsoid rather than a sphere being compressed along the spin axis, which would displace features by up to 0.17°. Markers are placed on the same ellipsoid and, when relief is enabled, are lifted by the sampled MOLA elevation onto the displaced terrain. The base layer is the Viking MDIM 2.1 colour mosaic, assembled from Viking Orbiter frames at 232 m/px and tiled through NASA Mars Trek; the dark regions (Syrtis Major, Acidalia) are albedo features. The Relief control displaces the surface from the MGS MOLA global topographic model at 463 m/px; the displacement is measured elevation and the slider sets the vertical exaggeration only. The optional Elevation overlay drapes the colour-shaded MOLA relief across the full 29.4 km range, from the Hellas floor at −8.2 km to the Olympus Mons summit at +21.2 km. Textures load from Maps/textures/mars_color_*.jpg, the DEM from Data/worlds/mars/layers/mars_dem.jpg.

Features, landing sites and research feed

Named features in Data/worlds/mars/features.json — the Tharsis and Elysium volcanoes, the canyon and outflow systems, the impact basins and northern plains, the highland terrae and the polar plana — are placed in planetocentric east longitude from the USGS/IAU Gazetteer. Successful surface missions are marked as landing icons: Viking 1 and Viking 2 (1976), the rovers Mars Pathfinder, Spirit, Opportunity, Curiosity, Zhurong and Perseverance, and the Phoenix and InSight landers. Selecting a marker returns the date, craft and context. The research panel calls body_server.py at /api/mars/latest for current Mars literature (NASA ADS, with arXiv as fallback) and issues a per-feature query on selection; absent a server it falls back to the seed research.json and to ADS search links. The engine, server and schema are shared with the other Worlds globes.

Areographic almanac

The sub-Earth longitude is the central meridian facing Earth. The pole direction and prime-meridian angle are taken from the IAU WGCCRE 2015 rotation model (via the RotationAxis function of Astronomy Engine), the body-fixed frame is constructed from them, and the Earth direction is projected onto that frame — east-positive, in the same frame as the map. The rate is 14.62°/hr. The solar longitude L_s, the season, the Mars Year and the sol of the Mars year derive from the NASA GISS Mars24 algorithm (Allison & McEwen 2000); the sol is taken as the difference of Mars Sol Dates between the epoch and the start of the current Mars year, not from a linear scaling of L_s, which the orbital eccentricity would displace by up to 40 sols. Apparent diameter and illuminated fraction follow from the Earth–Mars geometry at the time of evaluation.

Moons, fleet and locator

The two moons are drawn as an orbit diagram to scale: Phobos at 2.77 mean Mars radii on a 7 h 39 m orbit — 3.2 revolutions per 24 h 40 m sol, so it rises in the west — and Deimos at 6.92 radii on a 30 h 18 m orbit. Maximum angular separation from the disk is evaluated from the current Earth–Mars distance. No client-side ephemeris for the Martian moons is publicly available, so the rings and the separations are drawn rather than an instantaneous position. The fleet list carries the active orbiters and rovers, an arrival countdown for ESCAPADE (Mars transfer November 2026, arrival 2027), and the planned MMX and Rosalind Franklin. The community image is the most recent amateur image of Mars, retrieved by body_server.py from the PVOL2 (UPV/EHU Bilbao) archive and proxied same-origin. The final panel is a top-down plan of the Solar System: all eight planets placed from Astronomy Engine, Mars highlighted, and the dashed Earth–Mars sightline whose length sets the light-time and whose geometry gives the elongation and the next opposition — 19 February 2027. Each feed carries a status lamp and degrades when the server is unreachable.

Calibration

Feature longitudes are placed in the MDIM 2.1 frame (map centred on 0°, left edge −180°E, east-positive). Registration was checked against the mosaic at Olympus Mons, the three Tharsis Montes and Valles Marineris. Coordinates are planetocentric on the Mars 2000 sphere, matching the USGS nomenclature product; the offset from planetographic latitude peaks near 0.33° at mid-latitudes. The almanac is an ephemeris readout; the freely rotating globe is not slaved to the sub-Earth longitude.

• USGS Astrogeology / NASA — Viking MDIM 2.1 global colour mosaic (base map, via NASA Mars Trek)
• Smith, D. E. et al. 2001 — Mars Orbiter Laser Altimeter: experiment summary after the first year of global mapping of Mars, J. Geophys. Res. Planets 106(E10), 23689–23722, doi:10.1029/2000JE001364
• Archinal, B. A. et al. 2018 — Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015, Celest. Mech. Dyn. Astron. 130, 22, doi:10.1007/s10569-017-9805-5 — Mars pole, prime meridian and radii
• Allison, M. & McEwen, M. 2000 — A post-Pathfinder evaluation of areocentric solar coordinates with improved timing recipes for Mars seasonal/diurnal climate studies, Planet. Space Sci. 48, 215–235, doi:10.1016/S0032-0633(99)00092-6 — basis of the NASA GISS Mars24 algorithm
• IAU / USGS — Gazetteer of Planetary Nomenclature (Mars) — feature names & coordinates
• Cross, D. 2017– — Astronomy Engine (MIT) — rotation axis, planet positions, elongation & opposition search
• Hueso, R. et al. 2018 — The Planetary Virtual Observatory and Laboratory (PVOL) and its integration into the Virtual European Solar and Planetary Access (VESPA), Planet. Space Sci. 150, 22–35, doi:10.1016/j.pss.2017.03.014 — community amateur imagery
• NASA / agencies — Mars Exploration Program; The Planetary Society — every Mars mission (fleet status)