# Solar System surface maps — sources and credits

`data/solar/*.jpg` are the globes of the Solar System view (Earth's Blue Marble
is credited separately in `data/EARTH_TEXTURE_CREDIT.md`). Every map is a
public-domain (or no-use-constraint, "please cite") product of NASA or the
U.S. Geological Survey, built reproducibly by `tools/build_solar_textures.py`:
downloaded, re-centred so longitude 0° is mid-image with east to the right,
unimaged areas filled smoothly where noted, colour-adjusted where noted,
resized, and saved as JPEG (quality 85). Godot imports them VRAM-compressed with
mipmaps (the committed `.import` files). NASA and USGS do not endorse Expanse.

NASA imagery is generally not subject to copyright in the United States
(<https://www.nasa.gov/nasa-brand-center/images-and-media/>); USGS Astrogeology
products are public domain (U.S. federal government works), their catalogue
asking users to cite the authors. The NASA 3D Resources collection
(<https://github.com/nasa/NASA-3D-Resources>) describes its assets as "free and
without copyright".

| File | Size | Source | Credit | Treatment |
|------|------|--------|--------|-----------|
| `mercury.jpg` | 1024×512 | USGS Astropedia, *Mercury MESSENGER MDIS Global Color Mosaic 665m* (1024 px sample) | NASA / Johns Hopkins University APL / Carnegie Institution of Washington; USGS Astrogeology Science Center | desaturated 80 % toward grey-brown (the colour mosaic is enhanced); polar gaps filled |
| `venus.jpg` | 1024×512 | NASA 3D Resources, *Venus* | NASA / JPL, Magellan synthetic-aperture radar mosaic (false colour). **Radar surface, not cloud tops** — Venus's clouds are featureless in visible light | resized |
| `moon.jpg` | 2048×1024 | NASA SVS 4720, *CGI Moon Kit*, `lroc_color_2k.jpg` <https://svs.gsfc.nasa.gov/4720> | NASA's Scientific Visualization Studio (Ernie Wright, USRA; Noah Petro, NASA/GSFC); LRO LROC WAC | none |
| `moon_4k.jpg` | 4096×2048 | NASA SVS 4720, *CGI Moon Kit*, `lroc_color_poles_4k.tif` (close-up map, high render tier only) | NASA's Scientific Visualization Studio (Ernie Wright, USRA; Noah Petro, NASA/GSFC); LRO LROC WAC | none |
| `mars.jpg` | 1440×720 | NASA 3D Resources, *Mars* | NASA / JPL / USGS, Viking colour mosaic | none |
| `mars_topo.png`, `mars_hypsometry.csv` | 1024×512 (8-bit elevation, −8.5 to +21.5 km) | PDS Geosciences Node, MGS MOLA Mission Experiment Gridded Data Record, 4 px/deg, `megt90n000cb.img` | NASA / GSFC / JPL, Mars Global Surveyor MOLA Science Team (Smith et al. 2001, JGR 106, 23689) | re-centred; scaled to 8 bits; the hypsometry (water volume → sea level) computed on the full grid. Built by `tools/solar/build_mars_topography.py`; drawn only for terraformed seas (docs/design/COLONIES.md) |
| `phobos.jpg`, `deimos.jpg` | 512×256 | NASA 3D Resources, *Mars – Phobos*, *Mars – Deimos* | NASA / JPL (Viking, Mars Global Surveyor, MRO) | resized |
| `ceres.jpg` | 1024×512 | USGS Astropedia, *Ceres Dawn FC Global Mosaic 140m* (1024 px sample) | NASA / JPL-Caltech / UCLA / MPS / DLR / IDA; USGS Astrogeology | south-pole gap filled |
| `jupiter.jpg` | 2048×1024 | NASA Photojournal PIA07782, *Cassini's Best Maps of Jupiter (Cylindrical Map)* | NASA / JPL / Space Science Institute | resized from 3601×1801 |
| `io.jpg` | 1024×512 | USGS Astropedia, *Io Galileo SSI / Voyager Color Merged Global Mosaic 1km* | NASA / JPL / USGS (Galileo SSI, Voyager 1) | none |
| `europa.jpg` | 1024×512 | USGS Astropedia, *Europa Voyager – Galileo SSI Global Mosaic 500m* | NASA / JPL / USGS (Voyager, Galileo SSI); Tammy Becker, USGS | re-centred; greyscale tinted icy beige / reddish lineae; gaps filled |
| `ganymede.jpg` | 1024×512 | USGS Astropedia, *Ganymede Voyager – Galileo SSI Global Mosaic 1km* | NASA / JPL / USGS (Voyager, Galileo SSI) | re-centred; greyscale tinted; gaps filled |
| `callisto.jpg` | 1024×512 | USGS Astropedia, *Callisto Galileo / Voyager Global Mosaic 1km* | NASA / JPL / USGS (Voyager, Galileo SSI) | re-centred; greyscale tinted, brightened; gaps filled |
| `saturn.jpg` | 720×360 | NASA 3D Resources, *Saturn* | NASA / JPL Solar System Simulator | 60 % toward a paler butterscotch |
| `titan.jpg` | 1024×512 | USGS Astropedia, *Titan Cassini ISS Global Mosaic 4005m* | NASA / JPL-Caltech / Space Science Institute; USGS Astrogeology | re-centred; the near-infrared surface map is shown faintly through an orange haze tint (in visible light Titan is a featureless orange ball) |
| `neptune.jpg` | 720×360 | NASA 3D Resources, *Neptune* | NASA / JPL Solar System Simulator (a rendering after Voyager 2; no true global map exists) | none |
| `triton.jpg` | 1024×512 | USGS Astropedia, *Triton Voyager 2 Global Color Mosaic 600m* | NASA / JPL / USGS (Voyager 2) | the unimaged northern hemisphere filled smoothly; colour pulled 50 % toward pinkish white |
| `pluto.jpg` | 1024×512 | USGS Astropedia, *Pluto New Horizons LORRI MVIC Global Mosaic 300m* | NASA / Johns Hopkins University APL / Southwest Research Institute / Lunar and Planetary Institute (New Horizons team) | re-centred; greyscale tinted from dark red-brown to pale cream; the unimaged south (in polar night during the 2015 flyby) filled flat |
| `charon.jpg` | 1024×512 | USGS Astropedia, *Charon New Horizons LORRI MVIC Global Mosaic 300m* | as Pluto | re-centred; grey tint with a reddish north cap (Mordor Macula); unimaged south filled |

Bodies with no usable global map are drawn procedurally: the **Sun**
(animated granulation noise with limb darkening, `shaders/solar_sun.gdshader`),
**Uranus** (Voyager 2 saw an almost featureless haze: flat cyan with faint
bands) and **Eris** (never resolved: a pale sphere).

Total added: about 2.0 MB of JPEG across 18 files.

Source pages (Astropedia): <https://astrogeology.usgs.gov/search> — the product
names above; each lists the full-resolution mosaic and the 1024-pixel sample
used here.