Real Moon

Tap a spot to zoom in and name it; tap again to go out. Play flies to Tycho and more.

The real Moon from NASA's maps: its colors from the Lunar Reconnaissance Orbiter's wide-angle camera, its heights from the orbiter's laser altimeter. Each splat sits at its map's height and leans with its ground, so the sun lights the slopes facing it; craters stand out best near the line between day and night.

The relief is exaggerated ten times by default (the highest and lowest points are only about 20 km apart on a ball 3,475 km across); pick True height in the Splash tab to see it as it is. The Moon turns once every 27.3 days; here a day passes each second. There are no shadows, and the colors are a little enhanced, as in NASA's map. A tap zooms in and names the spot from the IAU's list; tap again to go out.

The Moon drawn from real maps: every splat sits at its place's measured height and has its place's measured color, and each named feature is where the planetary gazetteer puts it. The relief, the turning speed and the lighting are simplified, and each simplification is labeled in the splash.

1. Correct

   The color and elevation maps are CGI Moon Kit (LRO LROC color mosaic, 2025, and LOLA elevation).¹

   tools/sp2-maps.mjs reads the source file named in src/space/worlds.js and averages it into the splash's smaller maps (east longitudes from -180° to 180°).

2. Correct

   The Moon turns once every 655.72 hours (its sidereal day), sped up by the chosen factor.²

   Each frame the drive adds the elapsed time times the speed-up, over the day's length, to the turn.

3. Correct

   A tap flies to Tycho crater at -43.3°, -11.22° east, and the map shows it there. Its floor lies at least 3,500 m below its rim on the map.³⁴

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

4. Correct

   A tap flies to Copernicus crater at 9.62°, -20.08° east, and the map shows it there. Its floor lies at least 3,000 m below its rim on the map.⁵⁶

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

5. Correct

   A tap flies to Apollo 11's landing site (Tranquility Base) at 0.67°, 23.47° east, and the map shows it there.⁷

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

6. Not yet checked

   A tap names the place under it: the smallest named feature it lies in, what that lies on, and the plain or highland round it, from the IAU Gazetteer.⁸

   tools/sp3-places.mjs keeps each adopted feature center and size from the Gazetteer downloads; src/space/places.js finds the features a spot lies within (half their listed size from the center). tests/sp3.spec.mjs checks Tycho, Olympus Mons, Gale, Rachmaninoff, Maat Mons and Tranquility Base, and a tap on Tycho and on Olympus Mons in the browser.

7. Not yet checked

   Zoomed in, the ground comes from close-up tiles of the same maps, finer than the global map (the scales are in src/space/zoom.js); a feature named as a circle is an approximation of its real outline.¹

   tools/sp3-tiles.mjs averages each source into 10° tiles; tests/sp3.spec.mjs checks each world's tiles against its global map at a named feature.

1. 1CGI Moon Kit (LRO LROC color mosaic, 2025, and LOLA elevation), NASA's Scientific Visualization Studio (Ernie Wright); LRO LROC and LOLA teams
2. 2Moon Fact Sheet, NASA Space Science Data Coordinated Archive
3. 3Gazetteer of Planetary Nomenclature, USGS, IAU
4. 4Tycho (lunar crater), Wikipedia
5. 5Gazetteer of Planetary Nomenclature, USGS, IAU
6. 6Copernicus (crater), Wikipedia
7. 7Gazetteer of Planetary Nomenclature, USGS, IAU
8. 8Gazetteer of Planetary Nomenclature, IAU WGPSN and USGS Astrogeology Science Center

Simplified

The relief is exaggerated by default (ten or twenty times; Pluto, Ceres and Vesta are drawn at true height), as chosen and labeled in the Splash tab; close up during a fly it eases to at most twice its height. True height is one choice away.

Simplified

The world turns thousands of times faster than real (labeled in the Splash tab: an hour or a day each second).

Simplified

North is always up and the sun stays near the equator's plane: the axial tilt and the seasons are left out.

Simplified

The sun shades each slope by the cosine of its angle to the sun (Lambert's law) and leaves the night side dark, but nothing casts a shadow, and real surfaces scatter light in more complicated ways.

Simplified

The global map has about 1,000 by 500 heights and 2,000 by 1,000 colors; only the patches round the named features are sharper.

Simplified

The colors come from NASA's color map, which is adjusted toward human vision; the poles beyond 70° are filled from the laser altimeter's monochrome albedo.

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